Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Koichiro Watanabe Last modified date:2019.01.18

Professor / Division of Earth System Engineering / Department of Earth Resources Engineering / Faculty of Engineering

1. Mourad CHERBAL, Thomas TINDELL, Kotaro YONEZU, Koichiro WATANABE, Metacarbonatite Rocks from Amesmessa Area (In Ouzzal Terrane), Hoggar Shield, Algeria, Journal of African Earth Sciences , 2019.01.
2. Nyein N. Sint, Kotaro Yonezu, Thomas Tindell, May T. Aye, Htay Win, Akira Imai, Koichiro Watanabe, Geology and Skarn Cu–Bi–Au Mineralization at Shwe Min Bon Area, Kalaw Township, Southern Shan State, Myanmar, Resource Geology, 10.1111/rge.12187, 69, 1, 85-106, 2019.01, The Shwe Min Bon Cu–Au skarn deposit lies within one of the largest Au–Cu belts in Myanmar. The deposit is situated along the Shan scarp zone, which marks the boundary between the Myanmar central basin to the west and the Shan plateau to the east. The Shwe Min Bon deposit comprises skarn-type metasomatic alteration, and the Cu–Au mineralization occurs along the contact face between the Nwabangyi Dolomite and Shweminbon Formation and the Cretaceous dioritic rocks. The metasomatic process resulted in pro- and retrograde mineral assemblages in exoskarn. Hydrothermal activities in the Shwe Min Bon deposit are classified into prograde, retrograde stage I, and retrograde stage II. The prograde skarn is classified into a proximal garnet skarn with minor clinopyroxene and a distal wollastonite skarn. Chlorite, epidote, and tremolite–actinolite were formed during the retrograde stage I. Cu–Au mineralization mainly occurred in retrograde stage I, which was characterized by moderate temperatures (260–320 °C) and fluid with a moderate salinity (5.0–6.0% NaCl equiv.). Low temperature (180–200 °C) and low salinity (2.0–3.0% NaCl equiv.) were responsible for retrograde stage II. Au mineralization is mainly associated with chalcopyrite and tennantite in retrograde stage I and with tellurobismuthite in retrograde stage II..
3. Thomas Tindell, Koichiro Watanabe, Akira Imai, Ryohei Takahashi, Adrian J. Boyce, Kotaro Yonezu, Anders Schersten, Laurence Page, Takeyuki Ogata, The Kago low-sulfidation gold and silver deposit
A peripheral mineralisation to the Nansatsu high-sulfidation system, southern Kyushu, Japan, Ore Geology Reviews, 10.1016/j.oregeorev.2017.10.027, 102, 951-966, 2018.11, The Kago deposit is a small deposit located at the southern tip of the Satsuma Peninsula of Southern Kyushu, Japan. It lies proximal to the well-known Nansatsu-type mineralisation province dominated by high-sulfidation type epithermal deposits. The deposit was heavily mined in the 18 th Century, largely for its relatively higher gold compared to that of surrounding and regional deposits. The Kago deposit is a typical low-sulfidation deposit, characterised by adularia-quartz veins, composed of electrum, Ag-tetrahedrite, polybasite, chalcopyrite and pyrite. Based on mine records, the grade ranged from 4.1 to 13.3 g/t Au and 2.6-6.6 g/t Ag. Alteration grades from low to high temperature argillic into a propylitic zone at the extremes of the vein exposures. Carbonate is absent. Fluid inclusion microthermometry reveals a typical temperature range of 220-240 °C with salinity of 0.7-2.6 NaCl eq. wt%. Electrum from high-grade ore ranges from 66 to 69 wt% Au. 40Ar/39Ar age dating of adularia bearing colloform/crustiform and brecciated veins, suggests a mineralisation event from 4.23 to 4.0 Ma. δ18O of veined and silicified quartz ranges from +4.0 to +18.4‰. δ18OH2O of fluids in equilibrium with quartz, in the dominant range of measured fluid inclusion temperatures, ranges from -6.5‰ to -0.2‰. δ34S of pyrite has a narrow range from -1.8 to 2.7‰. The deposit lies at the northern extent of the classic Nansatsu high-sulfidation epithermal area, in which a number of silicified bodies punctuate the region in a roughly semi-circular shape. The Kago deposit lies within the principle mineralisation age range of the high-sulfidation deposits, which range from 5.5 to 3.7 Ma. The structural displacement of the Kago deposit from the Nansatsu mineralisation and the differing host rocks has greatly influenced alteration, ore and rock-water interaction of the ore depositing fluids. Here we seek to establish the relationship that this extended mineral province has between the differing styles of mineralisation..
4. Guillaume D. Faye, Atsushi Yamaji, Kotaro Yonezu, Thomas Tindell, Koichiro Watanabe, Paleostress and fluid-pressure regimes inferred from the orientations of Hishikari low sulfidation epithermal gold veins in southern Japan, Journal of Structural Geology, 110, 131-141, 2018.05, The orientation distribution of dilational fractures is affected by the state of stress around the fractures and by the pressure of the fluid that opened the fractures. Thus, the distribution can be inverted to determine not only the stress but also the pressure condition at the time of vein formation. However, epithermal ore veins that we observe today are the results of a great number of intermittent upwelling of overpressured fluids with different pressures. Here, we define driving pressure index (DPI) as the representative non-dimensionalized fluid pressure for the fluids. We collected the orientations of ∼1000 ore veins in the Hishikari gold mine, which were deposited at around 1 Ma, in southern Kyushu, Japan. It was found that the majority of the veins were deposited under an extensional stress with a NW-SE-trending σ3-axis and a northeasterly-inclined σ1-axis with relatively high stress ratio. The representative driving pressure ratio was ∼0.2. Data sets obtained at different depths in the mine indicated a positive correlation of representative driving pressure ratios with the depths. The correlation suggests repeated formation and break of pressure seals during the mineralization. Our compilation of the Pliocene–Quaternary stress regimes in southern Kyushu, including the result of the present study, suggests that epithermal gold mineralization was associated with distributed extensional deformations in southern Kyushu, and strain localization into an intra-arc rift seems to have terminated the mineralization..
5. Huan Li, Aung Zaw Myint, Kotaro Yonezu, Koichiro Watanabe, Thomas J. Algeo, Jing-Hua Wu, Geochemistry and U–Pb geochronology of the Wagone and Hermyingyi A-type granites, southern Myanmar: Implications for tectonic setting, magma evolution and Sn–W mineralization, Ore Geology Reviews, 95, 575-592, 2018.04, [URL], Tin-tungsten-associated granites occur widely in the Dawei region of the Southeast Asian tin belt. In this contribution, we present a detailed study of zircon U–Pb geochronology and whole-rock and zircon elemental geochemistry for the Wagone and Hermyingyi granites in southern Myanmar, with the aim of determining their petrogenesis, mineralization associations, and tectonic setting. These granitic rocks, which belong to the high-K calc-alkaline series A2-type granites, are characterized by high concentrations of SiO2 (75.2–82.5%), Rb (264–927 ppm), Th (18.4–58.3 ppm), U (10.4–18.3 ppm), and Y (33.5–212 ppm), but low contents of TFeO (0.57–3.45%), CaO (0.23–0.86%), MgO (0.02–0.19%), MnO (0.01–0.38%), TiO2 (0.01–0.10%), P2O5 (0.003–0.012%), Ba (3–162 ppm), and Sr (4.3–34.4 ppm). Hydrothermal zircons from the mineralized Wagone pluton show an anomalous lack of zoning and vermicular, spongy internal structures, and they contain high concentrations of Ti, Y, U, and light REEs but low Th/U ratios (mostly < 0.1). These features suggest slow crystallization from a U-enriched and Th-depleted residual magmatic fluid under relatively cool and reducing conditions. LA-ICPMS U–Pb dating of magmatic and hydrothermal zircons from the two granites yielded concordant ages of 61–60 Ma, indicating an Early Paleogene magmatic-mineralization event. Geochemical and geochronological data suggest that these A-type granites have a crustal origin and were produced by partial melting of a felsic clay-rich source in a back-arc extensional setting. The magmas may have ascended relatively slowly in the crust and experienced crystal fractionation and upper crustal contamination, contributing to intensive Sn–W mineralization in the Dawei area..
6. Aung Mynt, Koichiro Watanabe, others, Stable isotope and geochronological study of the Mawchi Sn-W deposit, Myanmar: implications for timing of mineralization and ore genesis, Ore Geology Reviews, 2018.03.
7. Warda Saad, Djamal Eddine Aissa, Koichiro Watanabe, Sachihiro Taguchi, Gold deposits associated with the gabbroic rocks at Tirek area, western Hoggar, Algeria
fluid inclusion study, Arabian Journal of Geosciences, 10.1007/s12517-017-3366-5, 11, 2, 2018.01, The Tirek gold deposit hosted in the Archean shield is one of the richest sources of mined gold for Algeria. The deposit is controlled by the East Ouzzal shear zone (EOSZ), a transcurrent N–S lithospheric fault. The EOSZ is a late Pan-African dextral-ductile shear zone separating two contrasting Precambrian domains: the Archean In Ouzzal block to the west (Orthogenesis with subordinate metasediments reworked and granulitized during the ca. 2 Ga Eburnean event) and a middle Proterozoic block to the east involved in the ca. 600 Ma Pan-African event. The auriferous quartz veins are mainly oriented in two directions, N–S veins hosted in mylonitic rocks and NE–SW veins hosted in gabbroic or gneissic bands. The NE–SW veins contain the richest ore. Gold ore is found in a system of veins and lenticular quartz veinlets arranged in anastomosing networks. The hydrothermal alteration associated with these veins is characteristically a carbonate-sericite-albite-pyrite assemblage. Gold is the main metal of economic importance; it is disseminated in the quartz as grains or fibers along microcracks and as microscopic grains in the host rocks. Microthermometric results and Raman laser data from fluid inclusions demonstrate that the ore-forming fluids contained H2O-CO2±CH4 and were low salinity. Homogenization temperatures are commonly 250–310 °C. In the Tirek deposit, the role of the shear zone that hosts the mineralization was to drain the hydrothermal fluid. Interactions between the fluid and the mafic host rocks and CO2 also contributed to the formation of the hydrothermal gold deposit at Tirek..
8. Huan Li, Ladislav A. Palinkaš, Koichiro Watanabe, Xiao Shuang Xi, Petrogenesis of Jurassic A-type granites associated with Cu-Mo and W-Sn deposits in the central Nanling region, South China
Relation to mantle upwelling and intra-continental extension, Ore Geology Reviews, 10.1016/j.oregeorev.2017.11.029, 92, 449-462, 2018.01, The central Nanling region in South China was the site of uplift, extensional deformation, granite magmatism and hydrothermal activity from 180 to 150 Ma. Information on the age, petrological characteristics, major and trace element contents, whole rock Sr and Nd and zircon Hf isotopic compositions of granitic plutons were synthesized to constrain the sources, evolutionary processes, and uplift-cooling rates of intrusions that host Cu–Mo and W–Sn deposits in this region. The older (180–160 Ma) Cu–Mo related granitoids are less differentiated, A1 type alkaline rocks with faster cooling and uplift rates. They have younger Nd and Hf two-stage model ages and higher εNd(t) and εHf(t) values that indicate mantle derived magmas were moderately contaminated by upper crust. The younger (160–150 Ma) W–Sn related granites are more differentiated, A2 type aluminous rocks with slower cooling and uplift rates. They have older Nd and Hf two-stage model ages and lower εNd(t) and εHf(t) values that require more upper crustal contamination. The time–space distribution and characteristics of these granitoids and ore deposits are indicative of centralized mantle upwelling and gradational crustal extension. The older rapidly-uplifted, less contaminated granitoids with Cu–Mo mineralization occur near the center of an intra-continental extension bulge produced by mantle upwelling, whereas the younger, slowly-uplifted, more contaminated granitoids with W–Sn mineralization occur on the periphery. The results suggest that metals in the Cu–Mo deposits may have come from the mantle whereas those in the world-class Nanling W–Sn polymetallic deposits were derived from Early Mesoproterozoic (1.4–1.6 Ga) crustal basement of the Cathaysia Block in South China..
9. Mitsuru Okuno, Agung Harijoko, I. Wayan Warmada, Koichiro Watanabe, Toshio Nakamura, Sachihiro Taguchi, Tetsuo Kobayashi, Geomorphological classification of post-caldera volcanoes in the Buyan-Bratan caldera, North Bali, Indonesia, IOP Conference Series: Earth and Environmental Science, 10.1088/1755-1315/103/1/012014, 103, 1, 2018.01, A landform of the post-caldera volcanoes (Lesung, Tapak, Sengayang, Pohen, and Adeng) in the Buyan-Bratan caldera on the island of Bali, Indonesia can be classified by topographic interpretation. The Tapak volcano has three craters, aligned from north to south. Lava effused from the central crater has flowed downward to the northwest, separating the Tamblingan and Buyan Lakes. This lava also covers the tip of the lava flow from the Lesung volcano. Therefore, it is a product of the latest post-caldera volcano eruption. The Lesung volcano also has two craters, with a gully developing on the pyroclastic cone from the northern slope to the western slope. Lava from the south crater has flowed down the western flank, beyond the caldera rim. Lava distributed on the eastern side from the south also surrounds the Sengayang volcano. The Adeng volcano is surrounded by debris avalanche deposits from the Pohen volcano. Based on these topographic relationships, Sengayang volcano appears to be the oldest of the post-caldera volcanoes, followed by the Adeng, Pohen, Lesung, and Tapak volcanoes. Coarse-grained scoria falls around this area are intercalated with two foreign tephras: the Samalas tephra (1257 A.D.) from Lombok Island and the Penelokan tephra (ca. 5.5 kBP) from the Batur caldera. The source of these scoria falls is estimated to be either the Tapak or Lesung volcano, implying that at least two volcanoes have erupted during the Holocene period..
10. Syafrizal, Tomy Alvin Rivai, Kotaro Yonezu, Damar Kusumanto, Koichiro Watanabe, Arie Naftali Hawu Hede, Characteristics of a low-sulfidation epithermal deposit in the River Reef Zone and the Watuputih Hill, the Poboya gold prospect, Central Sulawesi, Indonesia
Host rocks and hydrothermal alteration, Minerals, 10.3390/min7070124, 7, 7, 2017.07, Systematic exploration has delineated significant gold mineralization in the River Reef Zone and the presence of a siliceous body at Watuputih Hill, which is a Poboya gold prospect in Central Sulawesi, Indonesia. The mineralization is hosted within the Palu Metamorphic Complex. The host rocks consist of granite, biotite gneiss, and biotite schist, which is intercalated by feldspar porphyroblastic biotite schist and amphibolitic schist. The X-ray fluorescence (XRF) analysis of the granite and biotite gneiss suggests that the granitic rocks can be characterized as magnesian arc calcalkaline rocks, with a weakly peraluminous composition. Alteration minerals were analyzed by a combination of petrographic and X-ray diffraction (XRD). In the River Reef Zone, the hydrothermal alteration zones can be sorted by their proximity to the primary fluid conduit and divided into inner, high-T, and low-T propylitic zones. In Watuputih Hill, the hydrothermal alteration can be divided into advanced argillic and argillic zones. The hydrothermal alteration assemblages indicated that the fluid was at a near-neutral pH in the River Reef Zone, whereas the fluid was acidic within Watuputih Hill. Because the hill is relatively distant from the River Reef Zone, the presence of these zones at Watuputih Hill may be indicative of another mineralization system beneath the hill..
11. Huan Li, Kotaro Yonezu, Koichiro Watanabe, Thomas Tindell, Fluid origin and migration of the Huangshaping W–Mo polymetallic deposit, South China
Geochemistry and 40Ar/39Ar geochronology of hydrothermal K-feldspars, Ore Geology Reviews, 10.1016/j.oregeorev.2017.02.005, 86, 117-129, 2017.06, The Huangshaping deposit is a world-class W–Mo–Pb–Zn–Cu polymetallic deposit that formed during the Jurassic magmatic event in the central Nanling region, South China. In order to reveal the three-dimensional development of mineralization and alteration in this complicated fluid-rock system, four typical hydrothermal K-feldspar samples were collected from potassic alteration zones at different elevation levels around main W–Mo ore bodies, followed by precise trace element analysis and 40Ar/39Ar dating. The results show that these K-feldspars have a pronounced lanthanide tetrad effect with high contents of Ga, Ta, Nb, U, Y and HREE but low concentrations of Ba, Sr, Eu and Zr, suggesting a hydrothermal origin. Additionally, correlation between the Ca/Cl/K ratios and the apparent ages suggest that metasomatic fluids played an important role in the formation of the hydrothermal K-feldspars. The plateau 40Ar/39Ar ages which represent the timing of potassic alteration vary from 152.9 ± 0.5 to 154.3 ± 0.6 Ma, spatially showing younger trends from north to south and from shallow to deep. These dates correspond to the previous published molybdenite Re–Os data variations in different elevation levels, which record the mineralization event with relatively older ages ranging from 153.8 to 159.4 Ma. Combined with the spatial relation analysis among samples, the fluid migration rates associated with the mineralization and alteration are calculated at 10–100 m Ma−1. Thus, we propose a fluid downward migration model for the Huangshaping polymetallic deposit..
12. Takashi Ninomiya, Sho Taniguchi, Shoichi Shimoyama, Koichiro Watanabe, Tohru Danhara, Hideki Iwano, Daniel J. Dunkley, Kazuyuki Shiraishi, Chitaro Gouzu, U–Pb and fission-track dating of a submarine pyroclastic rock from southwest Japan, Island Arc, 10.1111/iar.12215, 2017.04.
13. Sachi Masunaga, Kotaro Yonezu, Mayumi Etou, Daisuke Kawamoto, Yoshiki Yamamoto, Yumi Kiyota, Yoshihiro Okaue, Koichiro Watanabe, Takushi Yokoyama, Effect of polyacrylic acid on polymerization and deposition of silicic acid in geothermal water
A case study at Takigami geothermal power plant, Oita Prefecture, Journal of the Geothermal Research Society of Japan, 10.11367/grsj.39.181, 39, 4, 181-189, 2017.01, To elucidate the effect of polyacrylic acid (PAA) on the formation of silica scales from geothermal water at geothermal power plants, two different experiments were carried out using geothermal water supplied from a production well, TP-2, at the Takigami geothermal power plant in Oita Prefecture, Japan. Polymerization of silicic acid in geothermal water and adsorption of silicic acid and aluminum on the surface of silica gel powder as a model compound of pre-formed silica scale were investigated in the presence and absence of PAA around 90?. The polymerization of silicic acid which causes changes in monosilicic acid concentration with time and in hydrodynamic size of polysilicic acid particles was not affected by PAA. On the other hand, the adsorption behavior of aluminum was considerably different in cases between the absence and presence of PAA. Only a small amount of aluminum was adsorbed in the absence of PAA, but most of aluminum was adsorbed in the presence of PAA. The amount of silicic acid adsorbed in the presence of PAA was significantly larger than that in the absence of PAA. Consequently, the Al-PAA complex may accelerate the formation of silica scales from geothermal water..
14. Adi Maulana, Akira Imai, Theo Van Leeuwen, Koichiro Watanabe, Kotaro Yonezu, Takanori Nakano, Adrian Boyce, Laurence Page, Anders Schersten, Origin and geodynamic setting of Late Cenozoic granitoids in Sulawesi, Indonesia, Journal of Asian Earth Sciences, 10.1016/j.jseaes.2016.04.018, 124, 102-125, 2016.07, Late Cenozoic granitoids are widespread in a 1600 km long belt forming the Western and Northern Sulawesi tectono-magmatic provinces. They can be divided into three rock series: shoshonitic (HK), high-K felsic calc-alkaline (CAK), and normal calc-alkaline to tholeiitic (CA-TH). Representative samples collected from eleven plutons, which were subjected to petrography, major element, trace element, Sr, Nd, Pb isotope and whole-rock δ18O analyses, are all I-type and metaluminous to weakly peraluminous. The occurrence of the two K-rich series is restricted to Western Sulawesi, where they formed in an extensional, post-subduction tectonic setting with astenospheric upwelling providing thermal perturbation and adiabatic decompression. Two parental magma sources are proposed: enriched mantle or lower crustal equivalent for HK magmas, and Triassic igneous rocks in a Gondwana-derived fragment thrust beneath the cental and northern parts of Western Sulawesi for CAK magmas. The latter interpretation is based on striking similarities in radiogenic isotope and trace element signatures. CA-TH granitoids are found mostly in Northern Sulawesi. Partial melting of lower-middle crust amphibolites in an active subduction environment is the proposed origin of these rocks. Fractional crystallization and crustal contamination have played a significant role in magma petrogenesis, particularly in the case of the HK and CAK series. Contamination by organic carbon-bearing sedimentary rocks of the HK and CAK granitoids in the central part of Western Sulawesi is suggested by their ilmenite-series (reduced) character. The CAK granitoids further to the north and CA-TH granitoids in Northern Sulawesi are typical magnetite-series (oxidized). This may explain differences in mineralization styles in the two regions..
15. Waleed S. Ibrahim, Koichiro Watanabe, Kotaro Yonezu, Structural and litho-tectonic controls on Neoproterozoic base metal sulfide and gold mineralization in north Hamisana shear zone, south Eastern Desert, Egypt: An integrated field, structural, Landsat 7 ETM + and ASTER data approach, Ore Geology Reviews, 10.1016/j.oregeorev.2016.05.012, 2016.05, The Hamisana shear zone (HSZ), is an excellent example of high strain shear belt of the Neoproterozoic Arabian–Nubian Shield (ANS), situated in a position between three major Pan- African terranes (SE Desert, Gabgaba, and Gebeit terranes)..
16. Mamiko Yamashita Maeno, Hironori Ohashi, Kotaro Yonezu, Akane Miyazaki, Yoshihiro Okaue, Koichiro Watanabe, Tamao Ishida, Makoto Tokunaga, Takushi Yokoyama, Sorption behavior of the Pt(II) complex anion on manganese dioxide (δ-MnO2)
a model reaction to elucidate the mechanism by which Pt is concentrated into a marine ferromanganese crust, Mineralium Deposita, 10.1007/s00126-015-0599-7, 51, 2, 211-218, 2016.02, It is difficult to directly investigate the chemical state of Pt in marine ferromanganese crusts (a mixture of hydrous iron(III) oxide and manganese dioxide (δ-MnO2)) because it is present at extremely low concentration levels. This paper attempts to elucidate the mechanism by which Pt is concentrated into marine ferromanganese crust from the Earth’s continental crust through ocean water. In this investigation, the sorption behavior of the Pt(II) complex ions on the surface of the δ-MnO2 that is a host of Pt was examined as a model reaction. The δ-MnO2 sorbing Pt was characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) to determine the chemical state of the Pt. Hydrolytic Pt(II) complex ions were specifically sorbed above pH 6 by the formation of a Mn-O-Pt bond. XPS spectra and XANES spectra for δ-MnO2 sorbing Pt showed that the sorbed Pt(II) was oxidized to Pt(IV) on δ-MnO2. The extended X-ray absorption fine structure (EXAFS) analysis showed that the coordination structure of Pt sorbed on δ-MnO2 is almost the same as that of the [Pt(OH)6]2− complex ion used as a standard. Therefore, the mechanism for the concentration of Pt in marine ferromanganese crust may be an oxidative substitution (penetration of Pt(IV) into structure of δ-MnO2) by a reduction-oxidation reaction between Pt(II) in [PtCl4-n(OH)n]2− and Mn(IV) in δ-MnO2 through a Mn-O-Pt bond..
17. Agung Harijoko, Ryusuke Uruma, Haryo Edi Wibowo, Lucas Doni Setijadji, Akira Imai, Kotaro Yonezu, Koichiro Watanabe, Geochronology and magmatic evolution of the Dieng Volcanic Complex, Central Java, Indonesia and their relationships to geothermal resources, Journal of Volcanology and Geothermal Research, 10.1016/j.jvolgeores.2015.12.010, 310, 209-224, 2016.01.
18. Mohamed El Ahmady Ibrahim, Koichiro Watanabe, Gehad Mohamed Saleh, Waleed Saad Ibrahim, Abu Rusheid lamprophyre dikes, South Eastern Desert, Egypt
as physical-chemical traps for REEs, Zn, Y, U, Cu, W, and Ag, Arabian Journal of Geosciences, 10.1007/s12517-015-1882-8, 8, 11, 9261-9270, 2015.11, Five lamprophyre dikes (L1-L5) intruded Abu Rusheid rocks (cataclastics and monzogranite) in the South Eastern Desert of Egypt along shear zones with NNW-SSE and E-W. The two sets of dikes differ in age, mineralization, and geochemical aspect. The NNW-SSE trending dikes (L1 and L2) are polymineralized and dislocate the E-W (L3, L4, and L5) trending dikes. These dikes underwent multistage of hydrothermal processes (ferrugination, fluoritization, kaolinitization, and calcification). They are characterized by common box works (physical trap) filled by incoming mineralization, and their feldspars and micas are relatively altered to clay minerals (chemical trap). From the mineralogical point of view, the cataclastic rocks are rich in base metals (pyrite, sphalerite, molybdenite, chalcopyrite, and galena), radioactive minerals (thorite, uranophane, kasolite, uranothorite), and accessories phases (zircon, xenotime, cassiterite, molybdenite, copper, columbite, and fluorite). L1 and L2 lamprophyre dikes contain U minerals (uranophane, kasolite, autunite, and torbernite), Mn-franklinite, woodruffite, xenotime, fluorite, silver, copper, and scheelite. L3 contains Zn and U minerals, whereas L4 and L5 contain Zn minerals only. The source magma producing lamprophyre dikes (L1 to L4) are peralkaline to alkaline, whereas L5 lamprophyres are mainly calc-alkaline in character; they were generated from the mantle and had formed in a post-collision tectonic setting with extensive Ti-rich metasomatism. The average ΣREE content in (L1 and L2) lamprophyres is 8006 ppm. REE patterns display clear concave upward pattern of W-type tetrad effect in the REE pattern accompanied by enrichment of the HREE over the LREE and marked negative Eu anomaly due to secondary mobilization of REEs..
19. Zhivko D. Budinov, KOTARO YONEZU, TINDELL THOMAS DAVID, Jillian Aira Gabo-Ratio, Stanoje Milutinovic, Adrian J. Boyce, Koichiro Watanabe, Copper-Gold Skarn Mineralization at the Karavansalija Ore zone, Rogozna Mountain, Southwestern Serbia, Resource Geology, 10.1111/rge.12075, 65, 4, 328-345, 2015.10.
20. Mohamed El Ahmady Ibrahim, Baher Abd El Hamed El-Kalioby, Gehan Mohamed Aly, Amera Mohamed El-Tohamy, Koichiro Watanabe, Altered granitic rocks, Nusab El Balgum Area, Southwestern Desert, Egypt
Mineralogical and geochemical aspects of REEs, Ore Geology Reviews, 10.1016/j.oregeorev.2015.04.016, 70, 252-261, 2015.10, Gabel Nusab El Balgum is located in the northern part of Bir Safsaf Area Southwestern Desert, Egypt (about 600km southwest of Aswan City) and covers an area of about 40km2. A few workers have investigated the Nusab El Balgum Area from the mineralogical and geochemical point of view. The area consists mainly of Devonian sandstone, Permo-Triassic volcanic rocks, altered granitic rocks and post-granitic dykes. The altered granitic rocks (silicified and kaolinized) have undergone several hydrothermal alteration processes and were subjected to different types of alteration (hematitization, carbonatization, kaolinization, sericitization and silicification) and are characterized by extreme enrichment in rare metals (such as Zr, Nb, Y and REEs).Bastnaesite, parisite, fergusonite, columbite, hydrothermal zircon, monazite and xenotime are common in the silicified and kaolinized granites. The silicified granite commonly contains more rare metals than the kaolinized granite. The REEs in Nusab El Balgum granites were introduced by hydrothermal fluids during alteration and occur in carbonate minerals such as bastnaesite (LREE) (CO3) F and parisite Ca (LREE) 2(CO3)3F2.The REE chondrite-normalized patterns of altered granites show an M-type tetrad effect and indicate higher LREEs, negative Ce anomaly (due to alteration by hydrothermal fluids) and negative Eu anomaly..
21. Tsubasa Otake, Takushi Yokoyama, Paul C. M. Francisco, Koichiro Watanabe, Effect of octahedrally coordinated aluminum ions on the uptake of Au(III) chloro-hydroxy complexes in Al-Si systems, Geochemical Journal, 10.2343/geochemj.2.0360, 49, 343-350, 2015.07, The uptake of Au(III) complexes (initial [Au] = 25 mmol·dm–3) by Al-Si-bearing precipitates formed by the hydrolysis of aluminum ions (initial [Al] = 0.04 mol·dm–3) in the presence of either solid silica or aqueous silicic acid was investigated at pH 6.0, [Cl–] = 0.24 mol·dm–3, and ambient temperature. A maximum of 40% of the total quantity of Au(III) complexes present in solution was sorbed onto the precipitate after 24 h in the absence of silica. Both solid silica and silicic acid inhibited the gold uptake, and silicic acid was a more effective inhibitor. Analyses of the solids showed that the fraction of octahedrally coordinated aluminum decreased as the bulk atomic Si/Al ratio in the solid increased. This decrease was more rapid in the presence of silicic acid than solid silica owing to the more efficient incorporation of aluminum into the silica structure. The zeta potential of the precipitates decreased as the fraction of octahedrally coordinated aluminum decreased and the atomic Si/Al ratio increased. The gold uptake decreased as the zeta potential of the precipitates decreased, suggesting that negatively charged Au(III) complexes were sorbed on the precipitates via electrostatic interactions.
Our findings suggest that the octahedrally coordinated aluminum determined the quantity of the gold uptake by governing the positive charge on the precipitate surface. In addition, desorption was promoted by the presence of solid silica after 5 h, suggesting that silica may promote the release of Au(III) chloro-hydroxy complexes as well as other negatively charged metal complexes from aluminum oxides or iron oxides in soil or sediment..
22. W. S. Ibrahim, Koichiro Watanabe, M. E. Ibrahim, Kotaro Yonezu, Neoproterozoic Tectonic Evolution of Gabal Abu Houdied Area, South Eastern Desert, Egypt
As a Part of Arabian–Nubian Shield Tectonics, Arabian Journal for Science and Engineering, 10.1007/s13369-014-1521-9, 40, 7, 1947-1966, 2015.07, The Neoproterozic-related structures have provided important insights into the tectonic history of the Egyptian Eastern Desert as well as the Arabian–Nubian Shield (ANS). The Gabal Abu Houdeid (GAH) area is in the extreme northern portion of the Hamisana shear zone (HSZ), one of the major high-strain zones in the ANS. The Neoproterozoic rocks exposed around GAH include ophiolitic ultramafic–mafic rocks, island-arc metasediments, metavolcanic rocks, intrusive syn-tectonic granodiorites, post-tectonic gabbros, and granites. The analysis of large-scale structures and fault kinematic data in terms of ductile and brittle deformation indicates that the sequence of folding and faulting events was constrained by available litho-tectonic units. Four deformational events are distinguished in the Neoproterozic rocks. Event D1 a pure compression stress regime with σ1 stress axis trending NNW–SSE to N–S represents an early shortening event associated with the Pan-African thrusting, during which intra-oceanic arcs and plateaus were accreted. Event D2 characterized by structures developed under ENE–WSW compressional regime (shortening event) and considered as the early stage of the second episode of collision within the Pan-African orogeny. Event D3 transpressional deformation associated with E–W contraction and N–S extension. It is the main event that controlled the deformation along the HSZ during the late stages of the collision between the East and West Gondwana in terms of escape tectonics. The D4 event is interpreted as a post-orogenic extensional event manifested by E–W dextral strike-slip and dip-slip normal faults striking NNW–SSE to N–S and E–W, which began to occur after the emplacement of post-tectonic granites..
23. Ratib Salehi, Nureddin M. Saadi, Ahmed Khalil, Koichiro Watanabe,  Integrating remote sensing and magnetic data for structural geology investigation in pegmatite areas in eastern Afghanistan, Journal of Applied Remote Sensing, 10.1117/1.JRS.9.096097, 9, 2015.01, This study used an integrated approach to investigate pegmatite areas in eastern Afghanistan. The analysis of surface data, including a digital elevation model (DEM), and Landsat Enhanced Thematic Mapper Plus (ETM+) images, was combined with airborne magnetic data to better understand three-dimensional geology in the area. The ETM+ and DEM data were used to map geological structures at the surface, which indicate that the area consists of two main fault systems that trend NNE and E-W. The two trends represent the remnants of reactivated structures that formed under the stress regimes generated during the tectonic evolution of eastern Afghanistan. Magnetic data indicate an NE-SW trending basin. A two-dimensional schematic model shows that the basin gradually deepens toward the SW with depths to the magnetic basement ranging between 2 and 11.5 km. The integration of the results gave new insight into the tectonic evolution and structure patterns near the pegmatites area. .
24. Igan S. Sutawidjaja, Mega F. Rosana, Koichiro Watanabe, Magma chamber model of Batur caldera, Bali, Indonesia
Compositional variation of two facies, large-volume dacitic ignimbrites, Indonesian Journal on Geoscience, 10.17014/ijog.2.2.111-124, 2, 2, 111-124, 2015.01, Batur is one of the finest known calderas on Earth, and is the source of at least two major ignimbrite eruptions with a combined volume of some 84 km3 and 19 km3. These ignimbrites have a similar compositions, raising the question of whether they are geneticaly related. The Batur Ignimbrite-1 (BI-1) is crystal poor, containing rhyodacitic (68 - 70wt % SiO2), white to grey pumices and partly welded and unwelded. The overlying Batur Ignimbrite-2 (BI-2) is a homogeneous grey to black dacitic pumices (64 - 66 wt % SiO2), unwelded and densely welded (40 - 60% vesicularity), crystal and lithic rich. Phase equilibria indicate that the Batur magma equilibrated at temperatures of 1100 - 1300°C with melt water contents of 3 - 6 wt%. The post-eruptive Batur magma was cooler ( < 1100°C) and it is melt more water rich ( > 6 wt % H2O). A pressure of 20 kbar is infered from mineral barometry for the Batur magma chamber. Magmatic chamber model is one in which crystals and melt separate from a convecting Batur magma by density differences, resulting in a stratified magma chamber with a homogeneous central zone, a crystal-rich accumulation zone near the walls or base, and a buoyant, melt-rich zone near the top. This is consistent with the estimated magma temperatures and densities: the pre-eruptive BI-1 magma was hoter (1300°C) and more volatile rich (6 wt % H2O) with density 2.25 g/cm3 than the BI-2 magma (1200°C; 4 wt % H2O) in density was higher (2.50 g/cm3). Batur melt characteristics and intensive parameters are consistent with a volatile oversaturation-driven eruption. However, the higher H2O content, high viscosity and low crystal content of the BI-1 magma imply an external eruption trigger..
25. Chaw Thuzar Win, Donatus Hendra Amijaya, Sugeng Sapto Surjono, Salahuddin Husein, Koichiro Watanabe, A Comparison of Maceral and Microlithotype Indices for Interpretation of Coals in the Samarinda Area, Lower Kutai Basin, Indonesia, Advances in Geology, 10.1155/2014/571895, Volume 2014, 17 pages, 2014.08.
26. W. S. Ibrahim, Koichiro Watanabe, M. E. Ibrahim, Kotaro Yonezu, Controls on quartzite bearing base-metal sulfide and invisible gold mineralization at Gabal Abu Houdied area, South Eastern Desert, Egypt, Arabian Journal of Geosciences, 10.1007/s12517-014-1563-z, 8, 7, 4983-4997, 2014.07, The Neoproterozoic basement rocks cropping out in the Gabal Abu Houdied (GAH) area comprises mainly three lithotectonic assemblages; mafic–ultramafic ophiolitic rocks, island arc-related metasediment–metavolcanic rocks and syn- and post-tectonic intrusions. The base-metal sulfide and invisible gold mineralization are restricted to quartzites, which are considered as member of island arc-related metasediment rocks. The mineralized quartzite rocks are cropped out at three localities, at Wadi El Haussioum where cover a small area (0.25 km2), at Bir Abu Houdeid, cover small area (0.5 km2), and at Bir Shani (3.5 km long with different width ranging from 4 to 75 m). Based on textural characteristics and chemical features, documented by electron probe microanalysis (EPMA) and inductively coupled plasma mass spectrometry analyses (ICP-MS), two phases of sulfide minerals assemblages in the investigated quartzites of GAH area. An early mineralization phase includes pyrite, pyrrhotite, argentite (acanthite) and invisible gold, and the late phase, dominated by pyrite, galena, sphalerite, chalcopyrite, covelite, and ± invisible gold. Analyses of the structural data collected from the quartzite rocks and surroundings indicated that the base-metal sulfide and associated gold mineralization in the GAH area are mostly controlled by D3 transperssional deformation event. This event is main Hamisana shear zone (HSZ) deformation event and characterized by transperssional stress regime, with σ1 trending E–W and σ3 trending N–S governed conjugate NNW sinistral and NNE–SSW dextral strike slip faulting..
27. Huan Li, Koichiro Watanabe, Kotaro Yonezu, Geochemistry of A-type granites in the Huangshaping polymetallic deposit (South Hunan, China)
Implications for granite evolution and associated mineralization, Journal of Asian Earth Sciences, 10.1016/j.jseaes.2014.03.004, 88, 149-167, 2014.07, The Huangshaping granites in Hunan Province, South China were investigated for their geochemical characteristics. Three types of granites have been petrographically identified: quartz porphyry, granophyre, and granite porphyry. Whole rock geochemistry suggests that the Huangshaping granites, especially the granite porphyry, exhibit typical A-type granite characteristics with their enrichment in Si, Rb, U, Th, and Nb and significant depletion in Ba, Sr, Ti, Eu, and P. Based on the Al, Y and Zr contents as well as the REE patterns of the rocks investigated, the quartz porphyry and the granophyre are classified as A1 type alkaline granites whereas the granite porphyry is considered as A2 type aluminous granite. Whole rock and quartz/feldspar O isotope data yields a wide range of δ18OSMOW values (11.09-26.32‰). The granites are characterized by high radiogenic Pb isotopic composition. The present-day whole rock Pb isotopic ratios are 206Pb/204Pb=18.706-19.155, 207Pb/204Pb=15.616-15.711 and 208Pb/204Pb=38.734-39.296. Combining the O-Pb isotope compositions with major, trace and REE geochemistry and regional geology characteristics, the Huangshaping granites were determined to resemble within-plate granites that were mainly derived from a felsic infracrustal source related to continental extension. The magma source of the quartz porphyry and the granophyre may have been generated from deeper depths, and then ascended rapidly with limited water content and low oxygen fugacity, which contributed to Cu, Pb and Zn mineralization. On the other hand, the magma that generated the granite porphyry may have ascended relatively slower and experienced pronounced crystal fractionation, upper-crustal basement rock contamination (assimilation) and wall-rock interaction, producing the Sn- and W-rich granite porphyry. This study reveals the crustal extension process and associated magmatic-metallogenic activities during 180-150Ma in South Hunan..
28. Huan Li, Koichiro Watanabe, Kotaro Yonezu, Zircon morphology, geochronology and trace element geochemistry of the granites from the Huangshaping polymetallic deposit, South China
Implications for the magmatic evolution and mineralization processes, Ore Geology Reviews, 10.1016/j.oregeorev.2013.12.009, 60, 14-35, 2014.07, The Huangshaping polymetallic deposit is a large-scale deposit located in the central Nanling region, South China. Different types of mineralization have been classified in the area, which are attributed to three types of granitoids from the composite granitic pluton: quartz porphyry, granophyre and granite porphyry. In order to study the magmatic genesis and evolutionary process, as well as constrain the crystallization and mineralization events, 100 zircon separates from different intrusive stages of the pluton have been analyzed for trace element contents and U-Pb isotopic concentrations. The results show that zircons from the Huangshaping granitoids are enriched in Th, U, Hf, Ti, REE and other trace elements, indicating hydrothermal fluid alteration and transformation. Additionally, there is a large variation between different types of granitoids in terms of trace element concentrations. Compared to the zircons from the quartz porphyry and the granophyre, zircons from the granite porphyry are more enriched in Th, U, Hf, Ti, and P but strongly depleted in Eu. This suggests that the magma that formed the granite porphyry possessed higher temperatures, possibly experienced stronger crystal fractionation and originated from a more evolved, complex magmatic source region with higher degree of crustal maturity. Combined with characteristics of crystal morphology and internal texture, hydrothermal zircons were distinguished from magmatic zircons in each granitoid to reveal mineralization processes. The U-Pb geochronology results show that there are two major stages of mineralization: ~. 190. Ma weak Cu (Pb, Zn) mineralization related to the quartz porphyry and the granophyre, and ~. 155. Ma strong W, Sn (Mo, Pb, Zn) mineralization associated with the granite porphyry. Compositions of these hydrothermal zircons suggest that the earlier stage mineralization could be close to single, relatively cold, reduced and quickly ascended fluids, whereas the later stage might be related to hot, oxidized, strongly fractionated and highly evolved, mixed fluids. This study also indicates that hydrothermal zircons from typical composite granitic plutons could be a good tool to reveal the multi-stage magmatic and mineralization process in middle to late Jurassic South China..
29. Adi Maulana, Kotaro Yonezu, Koichiro Watanabe, Geochemistry of rare earth elements (REE) in the weathered crusts from the granitic rocks in Sulawesi Island, Indonesia, Journal of Earth Science, 10.1007/s12583-014-0449-z, 25, 3, 460-472, 2014.06, We report for the first time the geochemistry of rare earth elements (REE) in the weathered crusts of I-type and calc-alkaline to high-K (shoshonitic) granitic rocks at Mamasa and Palu region, Sulawesi Island, Indonesia. The weathered crusts can be divided into horizon A (lateritic profile) and B (weathered horizon). Quartz, albite, kaolinite, halloysite and montmorrilonite prevail in the weathered crust. Both weathered profiles show that the total REE increased from the parent rocks to the horizon B but significantly decrease toward the upper part (horizon A). LREE are enriched toward the upper part of the profile as shown by La/YbN value. However, HREE concentrations are high in horizon B1 in Palu profile. The total REE content of the weathered crust are relatively elevated compared to the parent rocks, particularly in the lower part of horizon B in Mamasa profile and in horizon B2 in Palu profile. This suggests that REE-bearing accessory minerals may be resistant against weathering and may remain as residual phase in the weathered crusts. The normalized isocon diagram shows that the mass balance of major and REE components between each horizon in Mamasa and Palu weathering profile are different. The positive Ce anomaly in the horizon A of Mamasa profile indicated that Ce is rapidly precipitated during weathering and retain at the upper soil horizon..
30. Ibrahim WS, Mostafa MS, Ibrahim ME, Koichiro Watanabe, Soliman FA, Deformation history of Nugrus- Sikiat Belt, South Eastern Desert, Egypt; implication for Tectonic Environment, International Research Journal of Geology and Mining, 4, 3, 84-100, 2014.04.
31. Experimental Study on the Effect of Polyacrlic Acid on the Growth of Silica Scale.
32. Takashi Ninomiya, Shoichi Shimoyama, Koichiro Watanabe, Kenji Horie, Daniel J. Dunkley, Kazuyuki Shiraishi, Age of the Taishu Group, southwestern Japan, and implications for the origin and evolution of the Japan Sea, Island Arc, 10.1111/iar.12072, 23, 3, 206-220, 2014.01, The Taishu Group, a marine formation with a thickness of >5400m, crops out on Tsushima Island, located in the southwestern Japan Sea. The group, which is generally regarded as early Eocene to early Miocene in age, provides important information about the tectonic setting of the Japan Sea. In this study, we present new SHRIMP U-Pb dates for igneous zircons from the Kunehama Tuff, which is in the basal part of the Taishu Group, and the Oobaura Tuff, which is in the uppermost part of the group. Results show that the Taishu Group was deposited rapidly, during the short interval of 17.9-15.9Ma (early-middle Miocene), and is equivalent to other early-middle Miocene strata found in the Japan Sea region. Our results provide new constraints on the geological history of the Japan Sea and its islands..
33. Ryohei Takahashi, Yuki Shingo, Akira Imai, Koichiro Watanabe, Agung Harijoko, I. Wayan Warmada, Arifudin Idrus, Lucas Donny Setijadji, Phouvang Phoumephone, Anders Scherstén, Laurence Page, Epithermal gold mineralization in the Trenggalek District, East Java, Indonesia, Resource Geology, 10.1111/rge.12034, 64, 2, 149-166, 2014, Gold-mineralized quartz veins at the Trenggalek district of the Southern Mountains Range in East Java, Indonesia, are hosted by Oligo-Miocene volcaniclastic and volcanic rocks, and are distributed close to andesitic plugs in the northern prospects (Dalangturu, Suruh, Jati, Gregah, Jombok, Salak, and Kojan) and the southern prospects (Sentul and Buluroto). The plugs are subalkaline tholeiitic basaltic-andesite to calc-alkaline andesite in composition. 40Ar-39Ar dating of a quartz-adularia vein at the Dalangturu prospect yielded an age of 16.29 ± 0.56 Ma (2σ), and a crystal tuff of a limestone-pyroclastic rock sequence at the southwest of the Dalangturu prospect was determined as 15.6 ± 0.5 Ma (2σ). Statistic overlap of ages suggests that the gold mineralization in the northern prospects took place in a shallow marine to subaerial transitional environment. Hydrothermal alteration of the host rocks is characterized by the replacement of quartz, illite and adularia. Quartz veins in surface outcrops are up to 50cm wide in the northern prospects and up to 3m wide in the southern prospects, showing a banded or brecciated texture, and are composed of quartz, adularia, carbonates with pyrite, electrum, sphalerite, galena, and polybasite. Gold contents of quartz veins are positively correlated with Ag, Zn, Pb, and Cu contents in both the northern and southern prospects. The quartz veins at the Jati, Gregah, and Sentul prospects have relatively lower gold-silver ratios (Ag/Au = 23.2) compared to those at the Kojan, Dalangturu, Salak, and Suruh prospects (Ag/Au = 66.8). The quartz veins at the Dalangturu prospect are relatively rich in base metal sulfides. Ag/(Au+Ag) ratios of electrum in the Dalangturu prospect range from 45.2 to 65.0 at%, and FeS contents of sphalerite range from 1.2 to 6.4 mol%. Fluid inclusion microthermometry indicates ore-forming temperatures of 190-200°C and 220-230°C at the Sentul and Kojan prospects, respectively. Widely variable vapor/liquid ratio of fluid inclusions indicates that fluid boiling took place within the hydrothermal system at the Sentul prospect. Salinities of ore-fluids range from 0 to 0.7 wt% (av. 0.4 wt% NaCl equiv.) and from 0.5 to 1.4 wt% (av. 0.9 wt%) for the Sentul and Kojan prospects, respectively. The boiling of hydrothermal fluid was one of the gold deposition mechanisms in the Sentul prospect..
34. Mohamed El- Ahmady Ibrahim, Watanabe Koichiro, Abu Rusheid Lamprophyre Dykes, South Eastern Desert, Egypt: As Physical - Chemical Traps For REEs, Zn, Y, U, Cu, W and Ag, International Research Journal of Geology and Mining, Vol.3, No.3, 2013.12.
35. Sitha Kong, Koichiro Watanabe, Akira Imai, Magnetic Susceptibility and Geochemistry of Granitic Rocks in Cambodia, ASEAN Engineering Jour. Part C, 2, 1, 113-132, Part C, , 2013.12.
36. Adi Maulana, Andrew G. Christy, David J. Ellis, Akira Imai, Koichiro Watanabe, Geochemistry of eclogite- and blueschist-facies rocks from the Bantimala Complex, South Sulawesi, Indonesia: Protolith origin and tectonic setting , Island Arc , 10.1111/iar.12037, 22, 4, 427-452, 2013.12.
37. Vongsavanh, Kamar Shah Ariffin, Koichiro Watanabe, The Mineralogy of the Copper – Gold Ore Deposits at the Phu Kham Mine, Laos, Advanced Materials Research, 10.4028/ ,  858, 283-289, 2013.11, The Phu Kham Cu-Au deposit Porphyry-related skarn-type mineralization, Lao PDR is hosted by complexly deformed, schistose, quartz-sericite-pyrite altered Permo-Carboniferous volcanic, volcaniclastic and intrusive rocks. These rocks occupy the immediate hanging wall of a large NE-dipping thrust fault. Unmineralized, variably deformed red beds of the Mesozoic Khorat basin occur in the foot wall to the thrust. At Phu Kham the well defined foot wall and hanging wall sequences are separated by poorly-stratified quartz-rich conglomerate, breccia and lesser sandstone of uncertain affinities. In previous studies, the conglomerate package has both been included in the Khorat basin succession and interpreted tostratigraphically underlie the Permo-Carboniferous volcanics. Structural studies and additional U-P zircon geochronology were undertaken in 2009 to help clarify geological relations at Phu Kham. Improved constraints on thrust geometry and kinematics were also sought, enabling the deformation history at Phu Kham to be more confidently placed into a regional context. Results indicate the thrust was emplaced from the NE, and thus has greater affinity with deformation patterns in the NW-trending Truong Son fold belt.The conglomerate package is reinterpreted as a syn-orogenic molasse deposited ahead of the Advancing allochthon, but eventually overridden during the final stages of thrustemplacement. Unfortunately, definitive geochronological data supporting this conlusion were not obtained..
38. Sunyoung Ryu, Hiroshi Kitagawa, Eizo Nakamura, Tetsumaru Itaya, Koichiro Watanabe, K-Ar analyses of the post-caldera lavas of Bratan volcano in Bali Island, Indonesia - Ar isotope mass fractionation to light isotope enrichment, Journal of Volcanology and Geothermal Research, 10.1016/j.jvolgeores.2013.07.002, 264, 107-116, 2013.08, The post-caldera lavas of Bratan volcano in Bali Island, Indonesia were collected for whole rock chemical analyses and K-Ar analyses. Major and trace element chemistry shows that the lavas are basalts to andesites and typical of subduction-related tectonic setting. The 38Ar/36Ar ratios are 0.1851±3-0.1875±2 and the 40Ar/36Ar, 294.3±0.3-301.6±0.1, which strongly suggest that the mass fractionation to light isotope enrichment took place. The effect of the groundwater on magma is common on the basis of systematic mass fractionation of the atmospheric Ar enriched in lighter isotopes. This case was under the mass fractionation law analyzed numerically, giving the mass fractionation correction ages (14±15, 31±6, 55±22, 66±23, 94±32 and 125±51ka) consistent with the volcano stratigraphy though the magma composition that changed frequently in time..
39. Win Khant, I Wayan Warmada, Arifudin Idrus, Lucas Donny Setijadji, Koichiro Watanabe, Host Rocks’ Geochemistry and Mineralization Potential of Polymetallic Epithermal Quartz Veins at Soripesa Prospect Area, Sumbawa Island, Indonesia, Journal of Southeast Asian Applied Geology, 5, 1, 30-40, 2013.06.
40. Sanematsu, K., Kon, Y., Imai, A., Watanabe, K. and Watanabe, Y., Geochemical and mineralogical characteristics of ion-adsorption type REE mineralization in Phuket, Thailand, Mineralium Deposita, 10.1007/s00126-011-0380-5, 48, 4, 437-451, 2013.04.
41. Ryohei Takahashi, Matsueda Hiroharu, Victor M. Okrugin, Naotatsu Shikazono, Shuji Ono, Akira Imai, Elena D. Andreeva, Koichiro Watanabe, Ore-forming Ages and Sulfur Isotope Study of Hydrothermal Deposits in Kamchatka, Russia, Resource Geology, 10.1111/rge.12005,  63, 2, 210-223, 2013.03, In Kamchatka, Central Koryak, Central Kamchatka and East Kamchatka metallogenic belts are distributed from northwest to southeast. K–Ar age, sulfur isotopic composition of sulfide minerals, and bulk chemical compositions of ores were analyzed for 13 ore deposits including hydrothermal gold-silver and base metal, in order to elucidate the geological time periods of ore formation, relationship to regional volcanic belts, type of mineralization, and origin of sulfur in sulfides. The dating yielded ore-forming ages of 41 Ma for the Ametistovoe deposit in the Central Koryak, 17.1 Ma for the Zolotoe deposit and 6.9 Ma for the Aginskoe deposit in the Central Kamchatka, and 7.4 Ma for the Porozhistoe deposit and 5.1 Ma for the Vilyuchinskoe deposit in the East Kamchatka metallogenic belt. The data combined with previous data of re-forming ages indicate that the time periods of ore formation in these metallogenic belts become young towards the southeast. The averaged d34S CDT of sulfides are -2.8‰ for the Ametistovoe deposit in Central Koryak,-1.8‰ to +2.0‰ (av.-0.1‰) for the Zolotoe, Aginskoe, Baranievskoe and Ozernovskoe deposits in Central Kamchatka, and -0.7 to +3.8‰ (av.+1.7‰) for Bolshe-Bannoe, Kumroch, Vily-uchinskoe, Bystrinskoe, Asachinskoe, Rodnikovoe, and Mutnovskoe deposits in East Kamchatka. The negative d34S CDT value from the Ametistovoe deposit in Central Koryak is ascribed to the contamination of 32S-enriched sedimentary sulfur in the Ukelayat-Lesnaya River trough of basement rock. Comparison of the sulfur isotope compositions of the mineral deposits shows similarity between the Central Koryak and Magadan metallogenic belts, and East Kamchatka and Kuril Islands belts. The Central Kamchatka belt is intermediate between these two groups in term of sulfur isotopic composition..
42. Akira Imai, Kotaro Yonezu, Kenzo Sanematsu, Takashi Ikuno, Shingo Ishida, Koichiro Watanabe, Visut Pisutha-Arnond, Somchai Nakapadungrat and Jurapong Boosayasak, Rare Earth Elements in Hydrothermally Altered granitic Rocks in the Ranong and Takua Pa Tin-Field, Southern Thailand, Resource Geology, 10.1111/j.1751-3928.2012.00212.x, 63, 1, 84-98, 2013.03.
43. Huan Li, Xiaoshuang Xi, Chengming Wu, Koichiro Watanabe, Genesis of the zhaokalong Fe-Cn polymetallic deposit at Ynshu, China
Evidence from ore geochemistry and fluid inclusions, Acta Geologica Sinica (English Edition), 10.1111/1755-6724.12063, 87, 2, 486-500, 2013, The ore types of the Zhaokalong Fe-Cu deposit are divided into two categories: sulfide-type and oxide-type. The sulfide-type ore include siderite ore, galena-sphalerite ore and chalcopyrite ore, whereas the oxide-type ore include magnetite ore and hematite ore. The ore textures and structures indicate that the Zhaokalong deposit is of the sedimentary-exhalative mineralization type. Geochemical analyses show that the two ore types have a high As, Sb, Mn, Co and Ni content. The REE patterns reveal an enrichment of the LREE compared to the HREE. Isotopic analysis of siderite ore reveal that the o13C011 ranges from -2.01 to 3.34 (%o) whereas the δ18Osmow ranges from 6.96 to 18.95 (%). The tluid inclusion microthermometry results indicate that homogenization temperatures of fluid inclusions in quartz range from 131 to 181°C, with salinity values of 1.06 to 8.04 wt% NaCl eq. The mineralizing fluid therefore belongs to the low temperature - low salinity system, with a mineralizing solution of a CO2-Ca2+(Na+, K +)-SO42- (F-, Cl-)-H 2O system. The geochemical results and fluid inclusion data provide additional evidence that the Zhaokalong deposit is a sedex-type deposit that experienced two stages of mineralization. The sulfide mineralization probably occurred first, during the sedimentary exhalative process, as exhibited by the abundance of marine materials associated with the sulfide ores, indicating a higher temperature and relatively deoxidized oceanic depositional environment. After the main exhalative stage, hydrothermal activity was superimposed to the sulfide mineralization. The later stage oxide mineralization occurred in a low temperature and relatively oxidized environment, in which magmatic fluid circulation was dominant..
44. Win Kant, I Wayan Warmada, Arifudin Idrus, Lucas Donny Setijadji, Watanabe Koichiro, Fluid Inclusion Study of the Polymetallic Epithermal Quartz Veins at Soripesa Prospect Area, Sumbawa Island, Indonesia, Journal of Southeast Asian Applied Geology,  4, 2, 77-89, 2012.12.
45. Budi Muljana, Koichiro Watanabe, Mega Fatima Rosana, Source-rock Potential of the Middle to Late Miocene Turbidite in Majalengka Sub-basin, West Java Indonesia: Related to Magmatism and Tectonism
, Journal of Novel Carbon Resource Science,  6, 15-23, 2012.09.
46. Christopher Vehe Sagapoa, Akira Imai, Takeyuki Ogata, Kotaro Yonezu and Koichiro Watanabe, Lateritization Process of Peridotites in Siruka, Choiseul, Solomon Islands, Journal of Southeast Asian Applied Geology, 3, 2, 76-92, 2012.03.
47. Budi Muljana and Koichiro Watanabe, Modal and Sandstone Composition of the Representative Turbidite from the Majalengka Sub-Basin, West Java, Indonesia, Journal of Geography and Geology, 4, 3-17, 2012.03.
48. Win Kant, I Wayan Warmada, Arifudin Idrus, Lucas Donny Setijadji, Watanabe Koichiro, Ore Mineralogy and Mineral Chemistry of Pyrite, Galena, and Sphalerite at Soripesa Prospect Area, Sumbawa Island, Indonesia, Journal of Southeast Asian Applied Geology, 4, 1, 1-14, 2012.02.
49. Adi Maulana, Koichiro Watanabe, Akira Imai and Kotaro Yonezu, Petrology and Geochemistry of Granitic Rocks in South Sulawesi, Indonesia: Implication for Origin of Magma and Geodynamic Setting, International Journal of Civil and Geological Engineering, 6, 2-8, 2012.01.
50. Pornthip Parinayok, Mamiko Yamashita, Kotaro Yonezu, Hironori Ohashi, Koichiro Watanabe, Yoshihiro Okaue, Takushi Yokoyama, Interaction of Au(III) and Pt(IV) complex ions with Fe(II) ions as a scavenging and a reducing agent: A basic study on the recovery of Au and Pt by a chemical method, Journal of Colloid and Interface Science, 10.1016/j.jcis.2011.07.038, 364, 1, 272-275, 2011.12.
51. Zaw, K.L., Setijadji, L. D., Warmada, I.W. and Watanabe, K., Petrogenetic interpritation of granitoid rocks using multicationic parameters in the Sanggau Area, Kalimantan Island, Indonesia, Journal of Southeast Asian Applied Geology, Vol.3, No. 1, 45-53, 2011.06.
52. Nureddin Saadi, Koichiro Watanabe and Hideki Mizunaga, Evaluation of Image Processing Methods for Geological Interpretation in the Different Environments in Libya, Arabian Journal of Geosciences, 10.1007/s12517-010-0241-z, 4, 635-643, 2011.03.
53. N. M. Saadi, M. Abdel Zaher, F. El-Baz, Koichiro Watanabe, Integrated remote sensing data utilization for investigating structural and tectonic history of the Ghadames Basin, Libya, International Journal of Applied Earth Observation and Geoinformation, 10.1016/j.jag.2011.05.016, 13, 5, 778-791, 2011.01, This study was initiated to constrain the geological structure of the Ghadames Basin in northwest Libya. Detailed analysis was based on digital integration of surface data, including SRTM DEM, ETM+ and geologic maps with subsurface data, including well logs and potential field data. Integrated analysis of remotely sensed data of the SRTM and ETM+ were utilized to identify geologic lineaments in the area. Ground-based verification of the remote sensing data was achieved with field work. Interpretation and analysis of the lineaments indicate that the Ghadames Basin is controlled by four main fault systems that trend WNW, NNW, NW and ENE. Well logs and potential field data were used to delineate a detailed picture of the subsurface structure. The potential field data reveal two NE and NNE trending sedimentary basins. The depth of the basement inside the main basin ranges from 2 to 6 km. A two-dimensional (2-D) schematic model shows that the basin gradually deepens towards the southwest. The applied data integration gave new insight into the tectonic and structure patterns of the Ghadames Basin and the adjacent areas of northwest Libya..
54. Watanabe, K., Yamanaka, T. Harijoko, A., Saitra, C. and Warmada, IW., Caldera Activities in North Bali, Indonesia, Journal of Southwest Asian Applied Geology, 2, 3, 283-291, 2010.12.
55. Yuki Tohma, Akira Imai, Kenzo Sanematsu, Kotaro Yonezu, Ryohei Takahashi, Masaaki Koyama, Ryota Sekine, Robert Duncan, Koichiro Watanabe, Characteristics and mineralization age of the fukusen no. 1 vein, hishikari epithermal gold deposits, southern Kyushu, Japan, Resource Geology, 10.1111/j.1751-3928.2010.00140.x, 60, 4, 348-358, 2010.12, The Fukusen No. 1 vein is located in the southeastern part of the Yamada deposit, Hishikari epithermal gold deposits, southern Kyushu, Japan. 40Ar/39Ar plateau ages of adularia from the margin and the center of the Fukusen vein are determined to be 0.617 ± 0.024-Ma and 0.606 ± 0.009-Ma, respectively. The Fukusen No. 1 vein shows banding structure composed mainly of quartz, adularia and clay minerals. Colloform texture is displayed by cryptocrystalline to amorphous silica material that is associated with fine-grained electrum and sulfides near the center of the vein. Pyrite in the Fukusen No. 1 vein often shows acicular shape resulting from inversion from marcasite. Near the center of the vein, primary marcasite occurs associated with colloform texture of silica. The Fukusen No.1 vein preserves primary texture and materials which were deposited from the ore-forming hydrothermal solution. The Fukusen No. 1 vein was formed in a short period and is one of the youngest veins in the Hishikari deposits..
56. Akmaluddin, Koichiro Watanabe, Akihiro Kano, Wartono Rahardjo, Miocene warm tropical climate
Evidence based on oxygen isotope in central java, Indonesia, World Academy of Science, Engineering and Technology, 71, 66-70, 2010.11, Oxygen and carbon isotopes records of multi-species planktonic, benthic foraminifera and bulk carbonate sample from Central Java Indonesia demonstrate that warm sea surface temperature occurred during the Miocene. Planktonic δ 18O values from this study consistently lighter (-4 to -3 ‰PDB) than previous studies that indicate sea surface temperature during Miocene in this area was warm than tropical/equatorial localities. A surprising decrease of oxygen isotopic composition was recorded at ±14 Ma where the maximum of δ 18O values is -4.87 ‰PDB for Orbulina universa, -5.02 ‰PDB for Globigerinoides sacculifer and -4.30 ‰PDB for Globoquadrina dehiscens, this event we predict as Middle Miocene Optimum. Warming of sea surface temperature we interpret as related to the development of Western Pacific Warm Pool where warm water from Pacific Ocean through the Indonesian seaway appears to remain during Miocene. Our result also show increasing suddenly of oxygen isotope values of planktic, benthic and bulk carbonate sample from ± 12 Ma, the increasing cooled surface water relatively high degree with Late Miocene global cooling climate or we predict that due to closing of Indonesian Gateway..
57. Nanshi Zeng, Eiji Izawa, Koichiro Watanabe, Yoshinobu Motomura, Hydrothermal alteration related to silver mineralization at the iwami silver deposit, shimane prefecture, Japan, Resource Geology, 10.1111/j.1751-3928.2010.00129.x, 60, 3, 234-248, 2010.09, The Iwami epithermal silver deposit consists of Ag-Cu veins in a dacitic intrusive body at the deep portion of the Eikyu area, and veinlets with disseminated Ag mineralization in dacitic tuff breccia at a shallow portion of the Fukuishi area. Hydrothermal alteration associated with the silver mineralization is characterized by intense potassium metasomatism with oxidizing conditions. An illite zone occurs around the pathways of uprising fluids in both the Eikyu and Fukuishi areas. It grades laterally into the illite/smectite zone, which is surrounded by a broad smectite zone. Because of boiling, abundant adularia associated with silver mineralization overlaps on the altered tuff breccia in the Fukuishi area. The alteration zoning suggests that the western Eikyu area and the eastern Fukuishi area belong to a single hydrothermal system. The data of fluid inclusion microthermometry indicate that the temperatures range 220-270°C, and salinities range 5-7 wt percent NaCl equivalent for the silver mineralization at the upper portion in the Eikyu area and the lower portion in the Fukuishi area. Radiometric ages for volcanic rocks in the area range from 2.19 to 1.64 Ma, and the dacitic intrusion formed at approximately 1.6 Ma. The silver-dominant mineralizing hydrothermal fluids system was active around 1.44 to 1.07 Ma, which formed the Eikyu Ag-Cu veins at depth, and the Fukuishi Ag ores at the shallower portion..
58. Didit Hadi Barianto, Pentatok Kuncoro, Koichiro Watanabe, The use of foraminifera fossils for reconstructing the Yogyakarta Graben, Yogyakarta, Indonesia, Jour. of Southwest Asian Applied Geology, 2, 2, 138-143, 2010.08.
59. Agung Harijoko, Tin May Htun, Rodhie Saputra, I Wayan Warmada, Lucan Donny Setijadji, Akira Imai and Koichiro Watanabe, Mercury and arsenic contamination from small scale gold mining activities at Selogiri area, Central Java, Indonesia, Journal of Southwest Asian Applied Geology, 2, 1, 56-64, 2010.07.
60. Rare Earth Elements in the Silica Scales from Geothermal Water.
61. Sengpasith Houngaloune, Kamar Shah Ariffin, Hashim Bin Hussin, Koichiro Watanabe, Visane Nhinxay, The effects of limestone characteristic, granulation and calcination temperature to the reactivity of quicklime, Malaysian Journal of Microscopy, 6, 1, 53-57, 2010, This paper presents a study on the effects of limestone characteristic, granulation and calcination temperature to the reactivity of the produced quicklime. Limestones with different granulations (<1.18 mm, 4.75-10 mm and 10-20 mm) have been calcined at four selected temperatures (950°C, 1050°C, 1150°C, 1250°C) for 2 hours and the produced quicklime were then slaked, respectively. The microstructural characteristics of the limestone (texture, grain size, etc.) were determined using polarizing transmitted light microscope. The produced quicklime was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and BET (N2 adsorption method). The temperature rises during the hydration of quicklime were recorded in order to study its reactivity. Test results pointed out that the hydrated lime which was prepared at 1050°C calcination temperature for all granulations had the highest reactivity due to their highest specific surface area, high porosity with uniform pore size distribution structure and minimum crystalline size characteristics..
62. Nureddin M. Saadi, Essam Aboud, Koichiro Watanabe, Integration of DEM, ETM+, geologic, and magnetic data for geological investigations in the Jifara Plain, Libya, IEEE Transactions on Geoscience and Remote Sensing, 10.1109/TGRS.2009.2020911, 47, 10, 3389-3398, 2009.10, We used an integrated approach to constrain the geological structure of the Jifara Plain in northwest Libya. The analysis of surface data, including a digital elevation model (DEM), Landsat Enhanced Thematic Mapper Plus images, and geologic maps, was combined with subsurface data, including well logs and magnetic data. The DEM data were used for the identification of geological lineaments in the study area. The interpretation and analysis of the lineaments indicate that the Jifara Plain is controlled by three main fault systems, trending northwestsoutheast, eastwest, and northeastsouthwest. The three trends represent the remnants of reactivated structures that formed under the stress regimes generated during the tectonic evolution of North Africa. The magnetic data reveal three northwest- and northeast-trending sedimentary basins in the study area. The depth of the basement inside the main basin ranges from 1 to 5 km. The results indicate that the Jifara Basin is shallower than the surrounding basins. The integration of the results reflects different periods of tectonic activity in the Jifara Plain and the adjacent Jabal Nafusah..
63. N. M. Saadi, Koichiro Watanabe, Assessing image processing techniques for geological mapping
A case study in Eljufra, Libya, Geocarto International, 10.1080/10106040802556199, 24, 3, 241-253, 2009.07, Various image processing techniques were experimented with in this study to evaluate their efficiency for geological mapping in the Eljufra area of northwest Libya. Remote sensing data including multi-spectral optical Landsat Enhanced Thematic Mapper (ETM+), Synthetic Aperture Radar (ERS-2 SAR) and Digital Elevation Models (DEMs) extracted from the Shuttle Radar Topography Mission (SRTM) data were used to trace different lithological units as well as extracting geological lineaments in the study area. The study area is located in an arid environment mostly devoid of any vegetation. Most lithological and structural units are distinguishable based on their topographic form and spectral properties. Fusion of ETM+ and ERS-2 images was experimented with to further identify lithological units. Shaded relief techniques were implemented to enhance terrain perspective views and to extract geological lineaments. The results discriminated different rock units and modified formation boundaries and revealed new geological lineaments. Nine rock units were identified and plotted in the new geological map defined by the new boundaries. The dominant lineaments tend to run in the NNW-SSE and NNE-SSW directions. Analysis and interpretation of the lineaments provided information about the tectonic evolution of the study area..
64. Amirhomayoun Saffarzadeh, Takayuki Shimaoka, Yoshinobu Motomura, Koichiro Watanabe, Characterization study of heavy metal-bearing phases in MSW slag, Journal of Hazardous Materials, 10.1016/j.jhazmat.2008.08.093, 164, 2-3, 829-834, 2009.05, Slag products derived from the pyrolysis/melting and plasma/melting treatment of municipal solid waste (MSW) in Japan were examined for the characterization study of heavy metal-bearing phases using petrographic techniques. Detailed microscopic observations revealed that the shapes of heavy metal-rich inclusions are generally spherical to semi-spherical and their sizes range from submicron to scarcely large size spheres (over 100 μm). The experiments (both optical microscopy and electron probe microanalysis) indicated that Fe and Cu participate in mutual substitution and different proportions, and form mainly two-phase Fe-Cu alloys that bound in the silicate glass. This alloy characterizes the composition of more than 80% of the metal-rich inclusions. Other metals and non-metals (such as Pb, Ni, Sb, Sn, P, Si, Al and S) with variable amounts and uneven distributions are also incorporated in the Fe-Cu alloy. In average, the bulk concentration of heavy metals in samples from pyrolysis/melting type is almost six times greater than samples treated under plasma/arc processing. The observations also confirmed that slag from pyrolysis origin contains remarkably higher concentration of metallic inclusions than slag from plasma treatment. In the latter, the metallic compounds are separately tapped from molten slag during the melting treatment that might lead to the generation of safer slag product for end users from environmental viewpoint..
65. Jiro Etoh, Takeshi Kawagoe, Takayuki Shimaoka, Koichiro Watanabe, Hydrothermal treatment of MSWI bottom ash forming acid-resistant material, Waste Management, 10.1016/j.wasman.2008.08.002, 29, 3, 1048-1057, 2009.03, To recycle municipal solid waste incinerator (MSWI) bottom ash, synthesis of hydrothermal minerals from bottom ash was performed to stabilize heavy metals. MSWI bottom ash was mixed with SiO2, Al(OH)3, and Mg(OH)2 so its chemical composition was similar to that of hydrothermal clay minerals. These solid specimens were mixed with water at a liquid/solid ratio of 5. The reaction temperature was 200 °C, and reactions were performed for 24-240 h. Generation of kaolinite/smectite mixed-layer clay mineral was found in the samples after the reaction of the mixture of bottom ash, SiO2, and Mg(OH)2. Calcium silicate hydrate minerals such as tobermorite and xonotlite were also generated. X-ray powder diffraction suggested the presence of amorphous materials. Leaching tests at various pHs revealed that the concentration of heavy metals in the leachates from MSWI bottom ash hydrothermally treated with SiO2 and Mg(OH)2 was lower than that in leachates from non-treated bottom ash, especially under acid conditions. Hydrothermal treatment with modification of chemical composition may have potential for the recycling of MSWI bottom ash..
66. Amirhomayoun Saffarzadeh, Takayuki Shimaoka, Yoshinobu Motomura, Koichiro Watanabe, Petrogenetic characteristics of molten slag from the pyrolysis/melting treatment of MSW, Waste Management, 10.1016/j.wasman.2008.08.008, 29, 3, 1103-1113, 2009.03, MSW slag materials derived from four pyrolysis melting plants in Japan were studied from the viewpoint of petrology in order to discriminate the glass and mineral phases and to propose a petrogenetic model for the formation process of molten slag. Slag material is composed of two major components: melt and refractory products. The melt products that formed during the melting process comprise silicate glass, and a suite of minerals as major constituents. The silicate glass is essentially composed of low and high silica glass members (typically 30% and 50% of SiO2, respectively), from which minerals such as spinels, melilite, pseudowollastonite, and metallic inclusions have been precipitated. The refractory products consist mainly of pieces of metals, minerals and lithic fragments that survived through the melting process. Investigations demonstrated that the low silica melts (higher Ca and Al contents) were produced at upper levels of high temperature combustion chamber HTCC, at narrower temperature ranges (1250-1350 °C), while the high silica melts formed at broader temperature ranges (1250-1450 °C), at the lower levels of HTCC. The recent temperature ranges were estimated by using CaO{single bond}Al2O3{single bond}SiO2 (CAS) ternary liquidus diagram that are reasonably consistent with those reported for a typical combustor. It was also understood that the samples with a higher CaO/SiO2 ratio (>0.74-0.75) have undergone improved melting, incipient crystallization of minerals, and extensive homogenization. The combined mineralogical and geochemical examinations provided evidence to accept the concept of stepwise generation of different melt phases within the HTCC. The petrogenesis of the melt products may therefore be described as a two-phase melt system with immiscible characteristics that have been successively generated during the melting process of MSW..
67. Lucas Donny Setijadji, Koichiro Watanabe, An integrative geoscience data model by linking field-specific data models in digital geologic map, earth resource, and geo-hazard, Advances in Geosciences Volume 13: Solid Earth (SE), 10.1142/9789812836182_0006, 73-86, 2009.01, There are now several object-relational geoscience data models available, such as the digital geologic map and mineral exploration models. This study pursues an integrative model by integrating them and extending their contents with data from our research projects in Japan and SE Asia. Current result is the first version of GeoSEA data model that can support different kinds of geoscience projects in geological mapping, earth resources, and geo-hazards at a continental margin setting such as SE Asia..
68. Nureddin M. Saadi, Koichiro Watanabe, Lineaments extraction and analysis in Eljufra area, Libya, Journal of Applied Remote Sensing, 10.1117/1.2994727, 2, 1, 2008.10, Several image processing techniques have been separately and simultaneously applied to data obtained from Landsat ETM+, ERS-2 SAR, and Digital Elevation Models (DEM) to evaluate the performance of different satellite sensors for extracting and mapping geological lineaments in the Eljufra area of northwest Libya. Herein, hundreds of new lineaments in various trends have been identified in comparison to previous results obtained from geological maps. Visible and near infrared color composite of Landsat ETM+ overlaid on shaded relief maps enhanced the ability of extracting and mapping geological lineaments. Analysis and interpretation of the extracted lineaments provided information about the tectonic evolution of the investigated area. A gravity survey was performed to explore the subsurface structure of the study area. Euler deconvolution was applied to the gravity data to estimate the depths and locations of gravity source anomalies. A comparison of results obtained from remote sensing and gravity data indicates that the origin of most lineaments is structural..
69. N. M. Saadi, E. Aboud, H. Saibi, Koichiro Watanabe, Integrating data from remote sensing, geology and gravity for geological investigation in the tarhunah area, Northwest libya, International Journal of Digital Earth, 10.1080/17538940802435844, 1, 4, 347-366, 2008.01, The present work deals with the integration of remote-sensing, surface-geology and gravity-survey data to improve the structural knowledge of the Tarhunah area, northwest Libya. Geological information and remote-sensing data provided information about the surface structure. A gravity survey was conducted to decipher the subsurface structure. The results revealed that a basin having a width of 39 to 48 km trends NE. A two-dimensional (2-D) schematic model shows that the basin gradually deepens toward the southwest. Faults determined from a horizontal gradient, tilt derivative, and Euler deconvolution show a depth range of 2.5 to 7.5 km. The integration and interpretation of the results indicate that volcanic activity was related to the tectonic activity of an anticlinal structure called the Jabal Uplift..
70. Masaaki Owada, Yasuhito Osanai, Atsushi Kamei, Koichiro Watanabe, Gondwana to Asia - A history of continental growth and deep crustal processes
Introduction, Journal of Mineralogical and Petrological Sciences, 10.2465/jmps.080709, 103, 4, 215-217, 2008.
71. Nureddin Mohamed Saadi, Koichiro Watanabe, Akira Imai, Hakim Saibi, Integrating potential fields with remote sensing data for geological investigations in the Eljufra area of Libya, Earth, Planets and Space, 60, 6, 539-547, 2008, In this study, we successfully integrated geological data, potential field data, and remote sensing data with the aim of investigating and improving our knowledge of the structural setting of the Eljufra area, northwestern Libya. SPOT-5 panchromatic band and digital elevation models (DEM) were used to construct surface shaded maps, and gravity and aeromagnetic surveys were used to provide information on subsurface structures and the nature of intrusive bodies. The results revealed that the prevailing trend of lineaments is NNW-SSE and NNE-SSW. A Bouguer anomaly map revealed that horst and graben blocks occur inside the large graben. An analytic signal method was applied to the aeromagnetic data to estimate locations and the minimum depths to the contact. A comparison of gravity and magnetic data provided information on hydrothermally altered basalt and sediment density. An anticlinal structure was detected in the western part of the study area. The effects of faults on basalt rocks indicated geological time for volcanic activity..
72. Kotaro Yonezu, Takushi Yokoyama, Yoshihiro Okaue, Akira Imai, Koichiro Watanabe, Concentration of gold(I) Thiosulfate complex ions on the surface of alumina gel and their change in chemical state
Preliminary experiment in the elucidation of the formation mechanism of epithermal gold deposits, Resource Geology, 10.1111/j.1751-3928.2007.00035.x, 57, 4, 400-408, 2007.12, In order to elucidate the formation mechanism of low-sulfidation epithermal gold deposit, the adsorption of [Au(S2 O3)2]3- (a model compound for gold(I) complex ion) on alumina gel (a model compound for the aluminum-bearing minerals) and change in chemical state of [Au(S2 O3)2]3- after adsorption on the surface of alumina gel were investigated as a basic model experiment. In the pH range from 4 to 6, the amount of [Au(S2 O3)2]3- adsorbed on alumina gel decreased with increasing pH and decreased drastically between pH 6 and 7, and then approached zero above pH 8 at 30°C. At 60°C, the amount of gold adsorbed above pH 7 was enhanced compared with that at 30°C. This adsorption tendency indicates that [Au(S2O3)2]3- is mainly adsorbed by electrostatic interaction between negative charges of [Au(S2O3)2]3- and positive charges of alumina gel because of its isoelectric point around pH 9. The chemical state of gold after adsorption of [Au(S2 O3)2]3- on alumina gel was examined using X-ray absorption near edge structure (XANES). The result showed that [Au(S2O3)2]3- was spontaneously reduced to elemental gold even in the absence of specific reducing agents after adsorption on alumina gel. This reduction reaction might occur by two steps: (i) disproportionation of the adsorbed [Au(S2O3)2]3- at the surface of alumina gel, and (ii) spontaneous reduction of the resulting gold(III) complex ions on the surface of alumina gel. The experimental results suggest that aluminum plays an important role in the concentration of gold(I) complex ions and subsequent reduction of gold during the formation of low-sulfidation epithermal gold deposits..
73. Coprecipitation of Au(III) Complex Ions with Iron(III) Hydroxide and Their Spontaneous Reduction -Application to Recovery of Gold from the Wastes of Electronic Products-.
74. Abd Wl Wahed, A.A., Sadek, A.A., Abdel Kader, Z., Y. Motomura and K. Watanabe, Petrogenetic relationships between pegmatite and granite based on chemistry of muscovite in pegmatite wall zones, Wadi El Falio, Central Eastern Desert, Egypt., Annals Geological Survey Egypt, Vol.29, pp.123-134, 2007.07.
75. Takayuki Shimaoka, R. Zhang, Koichiro Watanabe, Alterations of municipal solid waste incineration residues in a landfill, Waste Management, 10.1016/j.wasman.2007.03.011, 27, 10, 1444-1451, 2007.07, Fresh municipal solid waste incineration residues (MSWIR) and a drilling core of 2-10 years old landfilled MSWIR were investigated to determine the alterations due to weathering in a landfill. Physical and geochemical properties and transformations of major components and heavy metals were analyzed for fresh and landfilled residues. Carbonates and hydroxides (10-12 vol%) as major mineralogical compositions in the 8-10 years weathered MSWIR were observed by modal analysis of thin sections. Three step sequential extractions indicated that reducible phases, mainly the Fe, Al and Mn hydroxides increased with depth in the landfill. A pH controlled leaching test (including availability test and pH dependent leaching test) was then conducted. Results indicated lower concentrations of leachable contents at pH values from 6 to 10 for the four elements (Pb, Zn, Al and Fe) in the 8-10 years landfilled residues than in the fresh and 1-2 years landfilled residues. This means that 8-10 years weathered MSWIR became more stable than fresh landfilled residues. The reasons for the stabilization of these elements might be the hydration of Al and Fe during weathering in the landfill, which then results in the heavy metals adsorptions of these minerals..
76. Syafrizal, Akira IMAI and Koichiro WATANABE, Origin of Ore-forming Fluids Responsible for Gold Mineralization of the Pongkor Au-Ag Deposit, West Java, Indonesia: Evidence from Mineralogic, Fluid Inclusion Microthermometry and Stable Isotope Study of the Ciurug-Cikoret Veins, Resource Geology, 10.1111/j.1751-3928.2007.00013.x, 57, 2, 136-148, 2007.06.
77. Kotaro Yonezu, Takushi Yokoyama, Yoshihiro Okaue, Akira Imai, Koichiro Watanabe, Role of Aluminum Surface in Concentration of Gold(I) Complexes and its Change of Chemical State, Resource Geology, Vol. 57, pp. 400-408, 2007.06.
78. Agung Harijoko, Yukiko Ohbuchi, Yoshinobu Motomura, Akira Imai, Koichiro Watanabe, Characteristics of the Cibaliung gold deposit
Miocene low-sulfidation-type epithermal gold deposit in Western Java, Indonesia, Resource Geology, 10.1111/j.1751-3928.2007.00011.x, 57, 2, 114-123, 2007.06, Middle Miocene (11.18-10.65 Ma) low sulfidation-type epithermal gold mineralization occurred in the Cibaliung area, southwestern part of Java Island, Indonesia. It is hosted by andesitic to basaltic andesitic lavas of the Middle Miocene Honje Formation (11.4 Ma) and is covered by Pliocene Cibaliung tuff (4.9 Ma). The exploration estimates mineral resource of approximately 1.3 million tonnes at 10.42 g/t gold and 60.7 g/t silver at a 3 g/t Au cut-off. This equates to approximately 435,000 ounces of gold and 2.54 million ounces of silver. That resource resulted from two ore shoots: Cibitung and Cikoneng. Studies on ore mineralogy, hydrothermal alteration, geology, fluid inclusion, stable isotopes and age dating were conducted in order to characterize the deposit and to understand a possible mechanism of preservation of the deposit. The ore mineral assemblage of the deposit consists of electrum, naumannite, Ag-Se-Te sulfide minerals, chalcopyrite, pyrite, sphalerite and galena. Those ore minerals occur in quartz veins showing colloform-crustiform texture. They are enveloped by mixed layer clay illite/smectite zone, which grades into smectite zone outward. The temperature of mineralization revealed by fluid inclusion study on quartz in the veins ranges from 170 and 220°C at shallow and deep level, respectively. The temperature range is in agreement with the temperature deduced from the hydrothermal alteration mineral assemblage including mixed layered illite/smectite and laumontite. The mineralizing fluid is dilute, with a salinity <1 wt% NaCl equivalent and has stable isotopes of oxygen and hydrogen composition indicating a meteoric water origin. Although the deposit is old enough that it would have been eroded in a tropical island arc setting, the coverage by younger volcanic deposits such as the Citeluk tuff and the Cibaliung tuff most probably prevented this erosion..
79. Leilanie O. Suerte, Sho Nishihara, Akira Imai, Koichiro Watanabe, Graciano P. Yumul, Victor B. Maglambayan, Occurrences of ore minerals and fluid inclusion study on the Kingking Porphyry copper-gold deposit, Eastern Mindanao, Philippines, Resource Geology, 10.1111/j.1751-3928.2007.00018.x, 57, 2, 219-229, 2007.06, The Kingking deposit is a gold-rich porphyry copper deposit and the southernmost deposit at the eastern Mindanao mineralized belt, Philippines. It is underlain by Cretaceous-Paleogene sedimentary and volcanic rocks that are intruded by mineralized Miocene diorite porphyries and by barren Miocene-Pliocene dacite and diorite porphyries. The main alteration zones in the deposit are the inner potassic zone and the outer propylitic zone. The biotite-bearing diorite and hornblende diorite porphyries are the primary host rocks of mineralization. Two dominant copper minerals, bornite and chalcopyrite, which usually occur as fracture fillings, are associated with fine crystalline quartz veinlet stockworks in the mineralized diorites. Minor secondary covellite, chalcocite and digenite are also observed. The primary Cu-Fe sulfide phases initially deposited from ore fluids consisted of bornite solid solution (bnss) and intermediate solid solution (iss), which decomposed to form the bornite and chalcopyrite. Peculiar bornite pods that are different from dissemination and are associated with volcanic rock xenoliths in biotite-bearing diorite porphyry are noted in a drill hole. These pods of bornite are not associated with quartz veinlet stockworks. Fluid inclusion analyses show three types of inclusions contained in Kingking samples: two-phase fluid-rich and vapor-rich inclusions and polyphase hypersaline inclusions from porphyry-type quartz veinlet stockworks. The liquid-vapor homogenization temperatures (TH) and the dissolution temperature of halite daughter crystals (TM) from the polyphase hypersaline inclusions predominantly range from 400°C up to >500°C. The wide range of TH and TM may be due to heterogeneous trapping of variable ratios of vapor and brine. For some inclusions, TH > TM and in some cases, TH < TM, indicating that some of the brine was supersaturated or saturated with NaCl at the time of entrapment. Calculated salinity of the polyphase hypersaline inclusions ranges from 40 to 60% NaCl equivalent. Temperature and vapor pressure of mineralized fluid were estimated to be 400°C and 16 MPa..
80. Akira Imai, Jumpei Shinomiya, Maung Thiha Soe, Lucas Donny Setijadji, Koichiro Watanabe, I. Wayan Warmada, Porphyry-type mineralization at Selogiri Area, Wonogiri Regency, Central Java, Indonesia, Resource Geology, 10.1111/j.1751-3928.2007.00019.x, 57, 2, 230-240, 2007.06, [URL], The Selogiri area, situated in Wonogiri regency, Central Java, is one of several gold prospecting areas in the Southern areas Mountain Range in Java, Indonesia. Three types of dioritic-andesitic intrusive rocks occur in the Selogiri area, namely, hornblende andesite porphyry, hornblende diorite porphyry and hornblende diorite, exposed in a half-circular depression where volcanic breccia and tuff are widely distributed. The occurrence of stockwork quartz veinlets and associated with magnetite and malachite coating along the cracks in the diorite porphyry suggests porphyry type mineralization. This is also supported by the occurrence of polyphase hypersaline fluid inclusions in the stockwork veinlet quartz. Small-scale miners are mining NS-trending quartz veins for gold associated with base metal sulfides. These veins are probably epithermal-type mineralization that overprinted porphyry-type mineralization. The Neogene intermediate to silicic hydrous magmatism in Java could have formed the porphyry-type mineralization in Selogiri, as in the rest of the Sunda-Banda arc..
81. Amirhomayoun Saffarzadeh, Takayuki Shimaoka, Yoshinobu Motomura, Koichiro Watanabe, Chemical and mineralogical evaluation of slag products derived from the pyrolysis/melting treatment of MSW, Waste Management, 10.1016/j.wasman.2005.12.005, 26, 12, 1443-1452, 2006.10, This paper provides the results of studies on the characteristics of novel material derived from pyrolysis/melting treatment of municipal solid waste in Japan. Slag products from pyrolysis/melting plants were sampled for the purpose of detailed phase analysis and characterization of heavy metal-containing phases using optical microscopy, electron probe microanalysis (EPMA), XRF and XRD. The study revealed that the slag material contains glass (over 95%), oxide and silicate minerals (spinel, melilite, pseudowollastonite), as well as individual metallic inclusions as the major constituents. A distinct chemical diversity was discovered in the interstitial glass in terms of silica content defined as low and high silica glass end members. Elevated concentrations of Zn, Cr, Cu, Pb and Ba were recorded in the bulk composition. Cu, Pb and Ba behave as incompatible elements since they have been markedly characterized as part of polymetallic alloys and insignificantly sulfides in the form of spherical metallic inclusions associated with tracer amounts of other elements such as Sb, Sn, Ni, Zn, Al, P and Si. In contrast, an appreciable amount of Zn is retained by zinc-rich end members of spinel and partially by melilite and silica glass. Chromium exhibits similar behavior, and is considerably held by Cr-rich spinel. The intense incorporation of Zn and Cr into spinel indicates the very effective enrichment of these two elements into phases more environmentally resistant than glass. There was no evidence, however, that Cu and Pb enter into the structure of the crystalline silicates or oxides that may lead to their easier leachability upon exposure to the environment..
82. Lucas Donny Setijadji, Shigeo Kajino, Akira Imai, Koichiro Watanabe, Cenozoic island arc magmatism in Java Island (Sunda Arc, Indonesia)
Clues on relationships between geodynamics of volcanic centers and ore mineralization, Resource Geology, 10.1111/j.1751-3928.2006.tb00284.x, 56, 3, 267-292, 2006.09, [URL], Java island, regarded as a classic example of island arcs, is built through multi events of Cenozoic arc magmatism produced by the subduction of Indian-Australian oceanic crusts along the southern margin of Eurasian plate. Regional crustal compositions, subducted slabs, and tectonics determined the spatial-geochemical evolution of arc magmatism and regional metallogeny. Tertiary geodynamics of island arc was dominated by backarc-ward migrations of volcanic centers. Only after the Miocene-Pliocene roll-back effects of retreating slab, slab detachment, and backarc magmatism took place in central Java. The source of arc magmas is mainly partial melting of mantle wedge, triggered by fluids released from dehydrated slabs. Increasing potassium contents of arc magmas towards the backarc-side and younger magmas is typical for all magmas, while alkali and incompatible trace elements ratios are characteristics for different settings of volcanic centers. The oceanic nature of crust and the likely presence of hot slab subducted beneath the eastern Java determine the occurrences of adakitic magmas. Backarc magmatism has a deeper mantle source with or without contributions from subduction-related materials. The domination of magnetite-series magmatism determines the sulfide mineralization for the whole island. District geology, geodynamics, and magma compositions in turn control particular styles and scales of precious metals concentrations. Deep-seated crustal faults have focused the locations of overlapping volcanic centers and metalliferous fluids into few major gold districts. Porphyry deposits are mostly concentrated within Lower Tertiary (early stage) volcanic centers in eastern Java which are not covered by younger volcanic centers, and whose sulfides are derived from partial melting of basaltic parental materials. On the other hand, high-grade low-sulfidation epithermal gold deposits formed in later stages of arc development and are spatially located within younger volcanic centers (Upper Miocene-Pliocene) that overlap the older ones. Gold in low-sulfidation epithermal system is likely to be derived from crustal materials. The overall interacting factors resulting in the petrochemical systematics that are applicable for exploration: 1) early-stage volcanic centers with high Sr/Y and Na2O/K2O ratios are more prospective for porphyry mineralization, while 2) later-stage volcanic centers with high K2O, total alkali, and K2O/Na2O ratios are more prospective for low-sulfidation epithermal mineralization..
83. K. Sanematsu, Koichiro Watanabe, R. A. Duncan, E. Izawa, The history of vein formation determined by 40Ar/39AR dating of adularia in the Hosen-1 vein at the Hishikari epithermal gold deposit, Japan, Economic Geology, 10.2113/gsecongeo.101.3.685, 101, 3, 685-698, 2006.05, The Hosen-1 vein has a symmetrical banded structure within the Hishikari epithermal gold deposit in Japan. The vein can be divided into four macroscopic bands. We used 40Ar/39Ar dating of adularia by incremental step heating to determine the duration of mineralization in the individual bands of the vein and the history of vein formation. Plateau ages were obtained from all adularia samples, and no significant excess 40Ar is recognized from inverse isochrons. The derived age spectra suggest that thermal overprinting of the epithermal system did not affect the plateau ages, although early bands must have been reheated by the thermal pulses associated with later bands. The 40Ar/39Ar ages of adularia indicate that vein formation occurred episodically in distinct periods separated by intervals of about 30,000 to 110,000 yr. The Hosen-1 vein grew in at least six increments at the -20-m level and at least four increments at the +62.5-m level. The total duration of mineralization from the margin to the center of the Hosen-1 vein was about 260,000 yr, during which time the temperature of the hydrothermal fluid decreased from 190° to 210°C to less than 170°C..
84. Stella Marris Limos-Martinez, Koichiro Watanabe, Slagging and fouling characteristics of seam 32/33, Panian coalfield, Semirara Island, Philippines, Fuel, 10.1016/j.fuel.2005.07.007, 85, 3, 306-314, 2006.02, Twenty samples of seam 32/33, the main seam of Panian coalfield in Semirara Island, Antique Province, Philippines, were collected from a borehole drilled at the northeastern edge of the coalfield. The samples were analyzed to characterize the coal geochemistry of the seam and understand why the coals of Semirara Island exhibit a high tendency for slagging and fouling despite its low average ash content. Analysis of the slagging and fouling characteristics of this seam is important because it supplies five electric power utilities and several cement plants in the Philippines. Proximate analyses and vitrinite reflectance measurements designate the rank of the seam as sub-bituminous C, based on ASTM coal classification. H/C versus O/C ratios indicate that the seam is made up largely of huminite, denoting early stages of coalification. Chemical analysis of the ash reveals high contents of Na, Mg, Fe, Ca, Ba and Sr. The strongly negative correlation of these elements with the ash content indicates an organic affinity of the chemical elements of the seam. Owing to enrichment in alkali and alkali-earth elements, slagging and fouling indices indicate that the seam has medium to high propensity for slagging and a severe tendency for fouling. The detrimental characteristics of coal feedstock from Panian mine is mitigated by modifications to the boiler design and operational conditions and by blending with coals imported from Indonesia, China and Australia..
85. Amirhomayoun SAFFARZADEH, Takayuki SHIMAOKA, Yoshinobu MOTOMURA, Koichiro WATANABE, Chemical and mineralogical evaluation of slag products derived from the pyrolysis/melting treatment of MSW, Waste Management, 26, pp. 1443-1452, 2006.01.
86. Nan Shi Zeng, Koichiro Watanabe, Eiji Izawa, Yushinobu Motomura, Mineralogy, K-Ar and 40Ar-39Ar dating studies of biotites from dacitic volcanics in the Iwami Silve area, Shimane Pref, Japan, Kuangwu Yanshi, 25, 4, 17-22, 2005.12, Base on the methods of microscope, X-ray diffractometer and electron-probe microanalyzer, biotites from dacitic rocks in the Iwami silver mining area, Shimane prefecture, Japan have been studied in detail. Part of these biotites subjected different level of hydrothermal alteration. The dating results from those fresh or with weakly altered biotites indicated that they were formed during Quaternary. However, the 40Ar-39Ar dating results obtained from biotites with intensively hydrothermal alteration suggested that the K-Ar isotope equilibrium in biotite crystal was broken by the later higher temperature hydrothermal activity. It revealed that the results obtained from altered biotites were older than that obtained from fresh biotites, and may cause a big age error. So, caution should be paid to the samples from the area with intensively hydrothermal alterations. The critical temperature for heating to break the original K-Ar isotope system was estimated to be about 200 °C..
87. Aramaki, Y., Yokoyama, T. Okaue, Y. Imai, A. and Watanabe, K., A study on the Formation of Smectite in Silica Scale Precipitated from Geothermal Water: The Effect of Magnesium, Resource Geology, 10.1111/j.1751-3928.2005.tb00248.x, 55, 3, 281-284, Vol.55, No.3, 281-284, 2005.09.
88. Sanematsu, K. Duncan, R., Imai, A. and Watanabe, K., Geochronological Constraints Using 40Ar/39Ar Dating on the Mineralization of the Hishikari Epithermal Gold Deposit, Japan, Resource Geology, 10.1111/j.1751-3928.2005.tb00246.x, 55, 3, 249-266, Vol.55, No.3, 249-266, 2005.09.
89. Syafrizal, Imai, A., Motomura, Y. and Watanabe, K., Characteristics of Gold Mineralization at the Ciurug Vein, Pongkor Gold-Silver Deposit, Indonesia, Resource Geology, 10.1111/j.1751-3928.2005.tb00244.x, 55, 3, 225-238, 2005.09.
90. Lucas Donny SETIJADJI, Koichiro WATANABE, On the Progress Design of Integrated Geologic Analysis System: Object-relational Detabase Model and Visualization for Earth Resources, Resource Geology, 10.1111/j.1751-3928.2005.tb00247.x, 55, 3, 267-280, Vol.55, No.3, 267-280, 2005.09.
91. Akira Imai, Carla B. Dimalanta, Graciano P. Yumul, Lucas Donny Setijadji, Koichiro Watanabe, About the special issue
Collection of achievements on Earth Resources from AUN/SEED-net, Resource Geology, 10.1111/j.1751-3928.2005.tb00236.x, 55, 3, 141-144, 2005.01.
92. Agung HARIJOKO, Kenzo SANEMATSU, Robert A. DUNCAN, Sukmandaru PRIHATMOKO and Koichiro WATANABE, Timing of the Mineralization and Volcanism at Cibaliung Gold Deposit, Western Java, Indonesia, Resource Geology, 10.1111/j.1751-3928.2004.tb00199.x, 54, 2, 187-195, 2004.06.
93. Yoshinobu ARAMAKI, Takushi YOKOYAMA, Yoshihiro OKAUE and Koichiro WATANABE, Chemical adsorption of silicic acid to aluminum combined with cation exchange and chelate resins as model compounds of the surface of microbes, Chemical Geology, 10.1016/j.chemgeo.2004.08.023, 212, 3-4, 339-349, 2004.01.
94. Takushi YOKOYAMA, Sachihiro TAGUCHI, Yoshinobu MOTOMURA, Koichiro WATANABE, Tetsuya NAKANISHI, Yoshinobu ARAMAKI and Eiji IZAWA, The effect of aluminum on the biodeposition of silica in hot spring water: Chemical state of aluminum in siliceous deposits collected along the hot spring water stream of Steep Cone hot spring in Yellowstone National Park, USA, Chemical Geology, 10.1016/j.chemgeo.2004.08.022, 212, 3-4, 329-337, 2004.01.
95. Ryota SEKINE, Eiji IZAWA and Koichiro WATANABE, Timing of fracture formation and duration of mineralization at the Hishikari deposit, southern Kyushu, Japan, Resource Geology, 10.1111/j.1751-3928.2002.tb00149.x, 52, 4, 395-404, 2002.12.
96. Ahmed BELHADI, Tetsuya NAKANISHI, Koichiro WATANABE and Eiji IZAWA, Gold Mineralization and Occurrence of Sinter in the Hoshino Area, Fukuoka Prefecture, Japan, Resource Geology, 10.1111/j.1751-3928.2002.tb00147.x, 52, 4, 371-380, 2002.12.
97. Agung HARIJOKO, Koichiro WATANABE, Yoshinobu MOTOMURA and Eiji IZAWA, Gold-bearing Quartz Veins and Hydrothermal Alteration of the Paleozoic Epithermal System in the Francis Creek Area, North Queensland, Australia, Resource Geology, 10.1111/j.1751-3928.2002.tb00145.x, 52, 4, 353-358, 2002.12.
98. Fernando G. SAJONA, Eiji IZAWA, Yoshinobu MOTOMURA, Akira IMAI, Hiroyuki SAKAKIBARA and Koichiro WATANABE, Victoria Carbonate-Base Metal Gold Deposit and Its Significance in the Mankayan Mineral District, Luzon, Philippines, Resource Geology, 10.1111/j.1751-3928.2002.tb00142.x, 52, 4, 315-328, 2002.12.
99. Jiro Etoh, Eiji Izawa, Koichiro Watanabe, Sachihiro Taguchi, Ryota Sekine, Bladed quartz and its relationship to gold mineralization in the Hishikari low-sulfidation epithermal gold deposit, Japan, Economic Geology, 10.2113/gsecongeo.97.8.1841, 97, 8, 1841-1851, 2002.12, Bladed quartz frequently is observed in low-sulfidation, epithermal gold deposits. Bladed calcite also has been documented in boiling zones of some active epithermal systems, and boiling in these systems has been directly linked to gold mineralization. In the Hishikari low-sulfidation epithermal gold deposit, the distribution and texture of fluid inclusions within bladed quartz reveal a similar relationship to gold precipitation. The formation of bladed quartz at Hishikari involves several stages: (1) deposition of bladed calcite; (2) precipitation of fine-grained adularia and quartz on the surface of calcites blades; (3) dissolution of calcite blades leaving cavities in the interstices between aggregates of adularia and quartz; and (4) infilling of the cavities by later quartz (i.e., pseudomorphs of the original bladed calcite). Bladed quartz is present largely in the deeper part of the vein system, beneath the high-grade gold ore zone at Hishikari. This distribution may be explained by the fact that the original bladed calcite formed at depth in the system, where boiling and loss of CO 2 initially caused the precipitation of the calcite, and quartz formed as pseudomorphs of the original calcite blades..
100. A. UCHIDA, T. YOKOYAMA, Y. MOTOMURA, A. MIYAZAKI, Y. OKAUE,, Role of iron (III) and aluminum hydroxides in concentration/reduction of Au (III) complexes, Resource Geology, 10.1111/j.1751-3928.2002.tb00132.x, 52, 3, 223-230, 2002.09.
101. O. HIMENO, H. OHIRA, Z. LIU, X. JIN and K. WATANABE, Provenance ages of Cretaceous strata in the Songliao Basin, Northeast China inferred from fission track data, International Geology Review, 43, 10, 945-952, 2001.12.
102. K. WATANABE and S. TAGUCHI, Overview of geological and geophysical features of Aso Volcano, Soc. Economic Geologists, Guidebook Ser., 34, 153-160, 2001.11.
103. A. UCHIDA, T. YOKOYAMA, K. WATANABE and E. IZAWA, Gold content in siliceous deposits formed from acidic and iron-rich geothermal waters at Hatchobaru, central Kyushu, Japan, Resource Geology, 10.1111/j.1751-3928.2001.tb00099.x, 51, 3, 269-271, 2001.09.
104. T. OKUDAIRA, Y. HAYASAKA, O. HIMENO, K. WATANABE, Y. SAKURAI and Y. OHTOMO, Cooling and inferred exhumation history of the Ryoke metamorphic belt in the Yanai district, south-west Japan: Constraints from Rb-Sr and fission-track ages of gneissose granitoid and numerical modeling, The Island Arc, 10.1046/j.1440-1738.2001.00312.x, 10, 2, 98-115, 2001.06.
105. T. YOKOYAMA, Y. MATSUKADO, A. UCHIDA, Y. MOTOMURA, K. WATANABE and E. IZAWA, Uptake of Au(III) ions by aluminum hydroxide and their spontaneous reduction to elemental gold (Au(0)), Jour. Colloid and Interface Science, 10.1006/jcis.2000.7260, 233, 1, 112-116, 2001.01.
106. Takamoto Okudaira, Yasutaka Hayasaka, Osamu Himeno, Koichiro Watanabe, Yasuhiro Sakurai, Yukiko Ohtomo, Cooling and inferred exhumation history on the Ryoke metamorphic belt in the Yanai district, South-west Japan
Constraints from Rb-Sr and fission-track ages of gneissose granitoid and numerical modeling, Island Arc, 10.1111/j.1440-1738.2001.00312.x, 10, 2, 98-115, 2001.01, The Ryoke metamorphic belt in south-west Japan consists mainly of I-type granitoids and associated low-pressure/high-temperature metamorphic rocks. In the Yanai district, it has been divided into three structural units: northern, central and southern units. In this study, we measured the Rb-Sr whole-rock-mineral isochron ages and fission-track ages of the gneissose granodiorite in the central structural unit. Four Rb-Sr ages fall in a range of ca 89-87 Ma. The fission-track ages of zircon and apatite are 68.9±2.6 Ma and 57.4 ±2.5 Ma (1σ error), respectively. Combining the newly obtained ages with previously reported (Th-)U-Pb ages from the same unit, thermochronologic study revealed two distinctive cooling stages; 1) a rapid cooling (>40°C/Myr) for a period (∼7 Myr) soon after the peak metamorphism (∼95 Ma) and 2) the subsequent slow cooling stage (∼5°C/Myr) after ca88 Ma. The first rapid cooling stage corresponds to thermal relaxation of the intruded granodiorite magma and its associated metamorphic rocks, and to the uplift by a displacement along low-angle faults which initiated soon after the intrusion of the magma. Uplift by the later stage deformation having formed large-scale upright folds resulted in progress of the exhumation during the first stage. The average exhumation velocity of the stage is ≥ 2 mm/yr. During the second stage, the rocks were not accompanied by ductile deformation and were exhumed with the rate of 0.1-0.2mm/yr. The difference in the exhumation velocity between the first and second cooling stages resulted from the difference in the thickness of the crust and in the activity of ductile deformation between the early and later stages of the orogenesis..
107. Osamu Himeno, Hiroto Ohira, Zhaojun Liu, Xue Jin, Koichiro Watanabe, Provenance ages of cretaceous strata in the songliao basin, Northeast China inferred from fission track data, International Geology Review, 10.1080/00206810109465058, 43, 10, 945-952, 2001, The Songliao Basin in northeast China is an intra-continental fossil rift basin mainly developed from the latest Jurassic and throughout the Cretaceous. The Daqing oil field in the basin is one of the largest hydrocarbon exploitation areas in China. A fission track (FT) study has been carried out on sandstone well samples in the Songliao Basin to constrain the depositional ages of Cretaceous strata and to ascertain their source region. FT dating also has been carried out on welded tuffs in the Dahinganling Mountains to determine their eruption ages. The detrital zircon FT age suggests that the depositional age of the middle Quantou Formation is younger than 109 Ma. Zircon FT ages for Cretaceous strata (from the Nenjiang Formation to the Quantou Formation) suggest that the source region has a fairly homogeneous cooling history at ∼120-100 Ma. Eruption ages of welded tuffs in the Dahinganling Mountains show an age range from 110 to 92 Ma. The regional geology and FT data suggest that volcanic rocks in the Dahinganling Mountains were eroded soon after their deposition and were reworked toward the Songliao basin..
108. Koichiro Watanabe, Tohru Danhara, Kazunori Watanabe, Kunihisa Terai, Tohru Yamashita, Juvenile volcanic glass erupted before the appearance of the 1991 lava dome, Unzen volcano, Kyushu, Japan, Journal of Volcanology and Geothermal Research, 10.1016/S0377-0273(98)00127-9, 89, 1-4, 113-121, 1999.04, Fugen-dake, the main peak of Unzen volcano, began to erupt on 17 November 1990 after 198 years of dormancy. Following a period of steam-dominated tephra eruptions, a new lava dome appeared at the bottom of Jigokuato Crater in the summit region on 20 May 1991. Non-hydrated vesiculated glass was detected in the precursory tephra eruptions, beginning 12 February 1991. Determination of whether glass pyroclasts are hydrated or not appears to be an effective means of ascertaining whether the tephra contains juvenile material from ascending magma. The detection of juvenile pyroclasts at Fugen-dake more than 3 months before the appearance of the lava dome suggests that monitoring of early tephra emissions is an effective way to help forecast impending magmatic eruptions..
109. Ryuji Yamada, Tetsu Yoshioka, Koichiro Watanabe, Takahiro Tagami, Hiroyuki Nakamura, Tetsuo Hashimoto, Susumu Nishimura, Comparison of experimental techniques to increase the number of measurable confined fission tracks in zircon, Chemical Geology, 10.1016/S0009-2541(98)00037-0, 149, 1-2, 99-107, 1998.07, We compared three experimental techniques for increasing the number of measurable horizontal confined fission tracks (HCTs) in annealed and unannealed zircons. These techniques are irradiation of 252Cf spontaenous fission fragments, irradiation of heavy ions (58Ni11+) using a tandem van de Graaf accelerator, and artificial fracturing of the zircon grains. All these techniques increased the number of measurable HCTs and they introduced no significant change in the measured length of annealed HCTs. For the samples with low track density (~105 cm-2), heavy ion irradiation was far more effective than irradiation of 252Cf fission fragments, because relatively long artificial tracks could be formed by the heavy ion irradiation. The artificial fracturing method is recommended when an accelerator facility is not easily available, because its effect was comparable to heavy ion irradiation and it is practicable in ordinary laboratories. Using these techniques, a preliminary comparison of annealing characteristics was performed for three zircon samples with different spontaneous track densities of ~4.105, ~4.106 and ~2.107cm-2 (with fission track ages of 3.1, 22.8 and 367.6 Ma, respectively). The length reduction due to the thermal annealing of these zircons appeared to be different, with the possibility that the thermal stability of spontaneous fission tracks depends on the initial spontaneous track density (ie the higher the initial spontaneous track density of a sample, the slower the rate of track annealing)..
110. M. Hayashi, T. Teramae, Koichiro Watanabe, Etching index to fission tracks, Nuclear Tracks and Radiation Measurements, 17, 3, 416-417, 1990, A practical procedure is proposed to standardize etching degrees for materials having different critical angles. Assuming that Vq and Vt are constant through the etching process, the increase of the track densities is considered to be proportional to the enlargement in the maximum track width. The density observable at time (Tt) after the saturation is given by ρt = ρηo cos2 θ + ηs (dρ/dW)Ws + (dρ/dW)(Wt - Ws), were ρ is the 'true' track density for a reference material, θ is the critical ange η0 the optical counting efficiency for tracks intersecting the original surface, ηs that for tracks revealed by bulk etching from the start of the saturation time, and Ws and Wt the maximum track widths at times of the saturation (Ts) and (Tt). The sum of the former two is equal to the saturated density (ρs), and the last to the additional density after the saturation. The etching index at time (Tt) after the saturation is defined as the ratio of ρt to ρ cos2 θ: EIt = ρt/[(ρs - ηs(dρ/dW)Ws)/ ηo]. The counting efficiency for latent tracks (ηs) can be evaluated by integrating (dρ/dW) from W = 0 to Ws, taking into account consideration the appearance of the bulk etched tracks, and can also be calculated when the track geometry is assumed. It must be stressed that this efficiency is unchangeable by the resolving power of microscopes used. On the other hand, ηo would be greatly affected by the resolving power in most cases, and cannot be logically evaluated because it is the product of two kinds of obscure factors: η1 for track length correction and ηu for many other unknowns. However, the former will be roughly given by ηo = Wr/R, where Wr is the resolving power measured separately, or estimated by the minimum track width which corresponds to just after the incubation period on the line tied to the origin and Wt. R is the etchable track length. In conclusion, using the available value of ρ cos2 θ, objective comparison of track densities is possible, because it depends essentially not on the etching efficiency only, but also the resolving power of microscopes used..
111. Koichiro Watanabe, Etching characteristics of fission tracks in plio-pleistocene zircon, Radiation Physics and Chemistry, 10.1016/1359-0189(88)90124-0, 15, 1-4, 171-174, 1988.01, Etching characteristics of fission tracks on the external surface of zircon with low spontaneous track densities have been assessed in order to facilitate more accurate dating of Plio-Pleistocene volcanic rocks. The etched track increment rate due to the prolonged etching factor was experimentally determined and the effects of etching anisotropy was examined..
112. Hiromu Mukaiyama, Tsuyoshi Kimura, Koichiro Watanabe, Masahiro Inoue, Hidemi Yakabe, Masato Nakamura, DISTRIBUTION OF LINEAMENTS IN KYUSHU ISLAND EXPLORATION OF EPITHERMAL GOLD-SILVER ORE DEPOSITS BY REMOTE SENSING TECHNIQUE (1ST REPORT)., Nihon Kogyokaishi, 10.2473/shigentosozai1953.103.1194_477, 103, 1194, 477-484, 1987.01, Remote Sensing is a useful technique for analysis of the fractures through which magmas rise in the crust and subsequently cause volcanism or mineralization. These fractures appear as lineaments on the ground surface. In order to detect the lineaments in Kyushu Island, 'slope-shaded' maps were drawn based on Landsat images and topographic maps treated by computer, in which slopes facing a certain direction were shaded to emphasize the elevation. Since this topographic maps were drawn using an imaginary light source shining from specified directions (N, NE, NW and W), it was possible to detect even those lineaments which would otherwise be difficult to be found from the Landsat images only. The lineaments detected in Kyushu Island are divided into four orientation groups; N -- S, NW -- SE, NE -- SW, and E -- W, respectively. In particular the E -- W lineament pattern can be mechanically obtained by putting the slope-shaded map from the Landsat images upon its negative map and then slightly shifting one of them. This lineament pattern reflects an E -- W stress field in Kyushu Island..
113. Koichiro Watanabe, Masao Hayashi, Toshio Fujino, Fission Track Age of Volcanoes in the Kuju Volcanic Region in Relation to Geothermal Activity, Journal of the Geothermal Research Society of Japan, 10.11367/grsj1979.9.207, 9, 3, 207-217, 1987.01, In order to clarify the relation between volcanic and geothermal activities in the Hohi geothermal area, fission track ages of the Kuju volcanic rocks, characterized by hornblende andesite, have been measured. The results show that the Kuju volcanism began about 0.3 Ma ago and continued to several tens thousand years ago. The most active Type A geothermal fields are associated with volcanoes younger than 0.20 Ma, the active Type B fields with those from 0.15 to 0.30 Ma in most cases. The volumes of these volcanoes range from 0.3 to 3.2 km3. Larger volcanoes tend to cool down more slowly than smaller ones..
114. Koichiro Watanabe, M. Hayashi, Fission track ages of volcanic rocks from the Hikosan area, northern Kyushu ( Japan)., Journal - Geological Society of Japan, 92, 3, 219-230, 1986, Fission track ages have been determined on zircon grains separated from Neogene volcanic rocks in the Hikosan area to clarify their chronological relations to the 'Green Tuff' activity. The obtained ages of 10 rock samples and their standard errors are as follows in ascending order: Yamakuni Formation 5.68+ or -0.29 Ma, 4.50+ or -0.48 Ma, Kitasakamoto Formation 5.66+ or -0.30 Ma, 4.83+ or -0.51 Ma, 5.22+ or -0.56 Ma, 4.60+ or -0.35 Ma, Hikosan Volcanic Rocks 4.05+ or -0.78 Ma, 3.97+ or -0.39 Ma, 3.95+ or -0.40 Ma, 3.85+ or -0.40 Ma. The 2 age data for the Yamakuni Formation seem to be lowered due to alteration, while those for the Kitasakamoto Formation are likely to present their formation age. Therefore, the so-called 'Green Tuff' activity in N and central Kyushu is considered to have continued on into the Pliocene. On the other hand, the Hikosan Volcanic Rocks were formed in the Pliocene, contrary to a previously accepted view that they are assigned to the Pleistocene Hohi Volcanic Rocks. -from English summary.
115. Masao Hayashi, Koichiro Watanabe, Naoyuki Furutani, Faults and their Stress Fields at the Otake-Hatchobaru Geothermal Area, Journal of the Geothermal Research Society of Japan, 10.11367/grsj1979.7.383, 7, 4, 383-399, 1985, The strike and dip of fractures such as slickensides, hydrothermal veins and joints, found in drillcores from the Otake-Hatchobaru geothermal area have been estimated after measuring the thermoremant magnetism of the cores with an astatic magnetmeter. The results show that most of the slickensides and veins dip southward, though their strikes vary considerably from NW-SE to NE-SW. In addition, the analysis of slickensides has revealed that the NW-SE trending faults basically are of left-handed strike slip type, while the NE-SW ones are of light-handed one. It is inferred that both kinds of faults were originally formed by the ENE-WSW compressional stress fields whose minimum stress axis dip NNW with moderate angles. Recently, the normal stress fields, whose intermediate stress axis tends NW-SE, have probably made the NW-SE trending fault planes open and permeable so that they have become the present breeding faults..