| 1. |
Yoshikuni HIROI, ＠Tomokazu HOKADA, ＠Tatsuro ADACHI, Atsushi KAMEI, Kazuyuki SHIRAISHI, Yoichi MOTOYOSHI, Chlorine-rich potassic-ferro-pargasite with Cl-poor cummingtonite in mafic granulite from Austhovde, Lützow-Holm Complex, East Antarctica, Journal of Mineralogical and Petrological Sciences, 10.2465/jmps.230329, 2024.01.  |
| 2. |
Fumiko HIGASHINO, Tetsuo KAWAKAMI, Tatsuro ADACHI, Masaoki UNO, Multiple post-peak metamorphic fluid infiltrations in southern Perlebandet, Sør Rondane Mountains, East Antarctica, Journal of Mineralogical and Petrological Sciences, https://doi.org/10.2465/jmps.221124, 118, 2023.06. |
| 3. |
Yoshikuni HIROI, Tomokazu HOKADA, Tatsuro ADACHI, Kazuyuki SHIRAISHI, Yoichi MOTOYOSHI, Edward S. GREW, Nanogranitoid inclusions with grandidierite in mafic granulite from Austhovde, Lützow-Holm Complex, East Antarctica, Journal of Mineralogical and Petrological Sciences, https://doi.org/10.2465/jmps.221209, 118, 2023.06. |
| 4. |
Fumiko Higashino, Tetsuo Kawakami, Tatsuro Adachi, Masaoki Uno, Multiple post-peak fluid infiltrations in southern Perlebandet, Sør Rondane Mountains, East Antarctica., Journal of Mineralogical and Petrological Sciences, 10.2465/jmps.230131a, 2023.04. |
| 5. |
Tomokazu HOKADA, Tatsuro ADACHI, Yasuhito OSANAI, Nobuhiko NAKANO, Sotaro BABA and Tsuyoshi TOYOSHIMA, Formation of corundum in direct contact with quartz and biotite in clockwise P–T trajectory from the Sør Rondane Mountains, East Antarctica, Journal of Mineralogical and Petrological Sciences, https://doi.org/10.2465/jmps.220317, 117, 1, 2022.08. |
| 6. |
Masaaki Owada, Yasuhito Osanai, Nobuhiko Nakano, Ippei Kitano, Tatsuro Adachi, Pham Binh, Tran Van Tri, Timing of magmatism and ultrahigh- to high-grade metamorphism in the Kannak Complex, Kon Tum Massif, Vietnam: Magmatic activity and its tectonic implications, Journal of Asian Earth Sciences, 10.1016/j.jseaes.2019.104077, 200, 104077-104077, 2020.09. |
| 7. |
Vuong Thi Sinh Bui, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Ippei Kitano, Masaaki Owada, Timing of high-grade metamorphism in the Kontum Massif, Vietnam: Constraints from zircon–monazite multi-geochronology and trace elements geochemistry of zircon–monazite–garnet, Journal of Asian Earth Sciences, 10.1016/j.jseaes.2019.104084, 187, 104084-104084, 2020.01. |
| 8. |
Sotaro Baba, Yasuhito Osanai, Tatsuro Adachi, Nobuhiko Nakano, Tomokazu Hokada, Tsuyoshi Toyoshima, Metamorphic P-T conditions and variation of REE between two garnet generations from granulites in the Sør-Rondane mountains, East Antarctica, Mineralogy and Petrology, 10.1007/s00710-019-00680-0, 123, 6, 821-845, 2019.06. |
| 9. |
Vuong Bui Thi Sinh, Yasuhito Osanai, Christoph Lenz, Nobuhiko Nakano, Tatsuro Adachi, Elena Belousova, Ippei Kitano, Gem-Quality Zircon Megacrysts from Placer Deposits in the Central Highlands, Vietnam—Potential Source and Links to Cenozoic Alkali Basalts, Minerals, 9, 2, 89, 2019.03. |
| 10. |
Vuong BUI THI SINH, Yasuhito OSANAI, Nobuhiko NAKANO, Tatsuro ADACHI, Ippei KITANO, Geochronology and REE geochemistry of zircon and garnet in pelitic gneisses from the Higo metamorphic terrane, Kyushu, Japan: Constraints on the timing of high–temperature metamorphism, Journal of Mineralogical and Petrological Sciences, 10.2465/jmps.181115, 114, 2, 47-59, 2019.03. |
| 11. |
Yoshikuni Hiroi, Tomokazu Hokada, Mutsumi Kato, Ayahiko Yanagi, Tatsuro Adachi, Yasuhito Osanai, Yoichi Motoyoshi, Kazuyuki Shiraishi, Felsite-nanogranite inclusions and three Al2Si5 polimorphs in the same garnet in ultrahigh-temperature granulites from Rundvagshetta, Lutzow-Holm Complex, East Antarctica., JournalJournal of Mineralogical and Petrological Sciences, 114, 60, 2019.03. |
| 12. |
Nguyen Van Thinh, Yasuhito Osanai, Tatsuro Adachi, Phong K. Thai, Nobuhiko Nakano, Akinori Ozaki, Yoshihiro Kuwahara, Ryosuke Kato, Masato Makio, Kiyoshi Kurosawa, Chemical speciation and bioavailability concentration of arsenic and heavy metals in sediment and soil cores in estuarine ecosystem, Vietnam, Microchemical Journal, 10.1016/j.microc.2018.03.005, 139, 268-277, 2018.06, The first investigation of arsenic (As) contamination in soil cores in the biggest estuarine ecosystem in northern Vietnam was conducted using FE-EPMA, ICP-MS and XRD techniques. Concentrations of arsenic and five heavy metals were measured and mineralogical characteristic of soils and sediments in different land uses were analyzed. Most of the soils contained high proportions of As and heavy metals in the potential mobility fractions and silicate minerals. High concentrations of As and heavy metals were observed in river sediments and top-layers of mangrove forest soil cores. Qualitative analyses using WDS technique on FE-EPMA found As on the iron (hydro)oxides and framboidal pyrite surfaces in the samples. The principal component analysis indicated the enrichment of As and heavy metals in the upper soil layers, suggesting that intensive human activities in upstream of the Red river in recent decades could be the cause of elevated levels of these toxic elements in the estuarine ecosystem.. |
| 13. |
Terumi Ejima, Yasuhito Osanai, Masahide Akasaka, Tatsuro Adachi, Nobuhiko Nakano, Yoshiaki Kon, Hiroaki Ohfuji, Jargalan Sereenen, Oxidation states of Fe in constituent minerals of a spinel Lherzolite xenolith from the Tariat depression, Mongolia: The significance of Fe3+ in olivine, Minerals, 10.3390/min8050204, 8, 5, 2018.05. |
| 14. |
Ippei Kitano, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Ian C.W. Fitzsimons, Detrital zircon and igneous protolith ages of high-grade metamorphic rocks in the Highland and Wanni Complexes, Sri Lanka: Their geochronological correlation with southern India and East Antarctica, Journal of Asian Earth Sciences, 10.1016/j.jseaes.2018.01.017, 156, 122-144, 2018.05, The high-grade metamorphic rocks of Sri Lanka place valuable constraints on the assembly of central parts of the Gondwana supercontinent. They are subdivided into the Wanni Complex (WC), Highland Complex (HC) and Vijayan Complex (VC), but their correlation with neighbouring Gondwana terranes is hindered by a poor understanding of the contact between the HC and WC. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U–Pb dating of remnant zircon cores from 45 high-grade metamorphic rocks in Sri Lanka reveals two domains with different age characteristics that correlate with the HC and WC and which help constrain the location of the boundary between them. The HC is dominated by detrital zircon ages of ca. 3500–1500 Ma from garnet–biotite gneiss, garnet–cordierite–biotite gneiss, some samples of garnet–orthopyroxene–biotite gneiss and siliceous gneiss (interpreted as paragneisses) and igneous protolith ages of ca. 2000–1800 Ma from garnet–hornblende–biotite gneiss, other samples of garnet–orthopyroxene–biotite gneiss, garnet–two-pyroxene granulite, two-pyroxene granulite and charnockite (interpreted as orthogneisses). In contrast, the WC is dominated by detrital zircon ages of ca. 1100–700 Ma from paragneisses and igneous protolith ages of ca. 1100–800 Ma from orthogneisses. This clearly suggests the HC and WC have different origins, but some of our results and previous data indicate their spatial distribution does not correspond exactly to the unit boundary proposed in earlier studies using Nd model ages. Detrital zircon and igneous protolith ages in the HC suggest that sedimentary protoliths were eroded from local 2000–1800 Ma igneous rocks and an older Paleoproterozoic to Archean craton. In contrast, the WC sedimentary protoliths were mainly eroded from local late Mesoproterozoic to Neoproterozoic igneous rocks with very minor components from an older 2500–1500 Ma craton, and in the case of the WC precursor sediments there was possibly additional detritus derived from early to middle Neoproterozoic metamorphic rocks. The relic zircon core ages in the HC are comparable with those of the Trivandrum Block and Nagercoil Block of southern India. In contrast, those ages in the WC match the Achankovil Shear Zone and Southern Madurai Block of southern India. These comparisons are also supported by Th/U ratios of detrital zircon cores from paragneisses (Th/U ratios of >
0.10 for the former and not only >
0.10 but also ≤0.10 for the latter). Comparisons with the Lützow-Holm Complex of East Antarctica indicate that the geochronological characteristics of the HC and WC broadly match those of the Skallen Group, and the Ongul and Okuiwa Groups, respectively.. |
| 15. |
Kitano, I., Osanai, Y., Nakano, N., Adachi, T., Fitzsimons, I.C.W., Detrital zircon and igneous protolith ages of high-grade metamorphic rocks in the Highland and Wanni Complexes, Sri Lanka: Their geochronological correlation with southern India and East Antarctica., Journal of Asian Earth Sciences, 156, 122-144, 2018.02. |
| 16. |
Recent progress in lower crustal process : precise analyses on ultrahigh-temperature metamorphism. |
| 17. |
Yasuhito Osanai, K. Sajeev, Nobuhiko Nakano, Ippei Kitano, W.K.V. Kehelpannala, Ryosuke Kato, Tatsuro Adachi, S.P.K. Malaviarachchi, UHT granulites of the Highland Complex, Sri Lanka II: Geochronological constraints and implications for Gondwana correlation, Journal of Mineralogical and Petrological Sciences, 111, 157-169, 2016.06. |
| 18. |
Yasuhito Osanai, K. Sajeev, Nobuhiko Nakano, Ippei Kitano, Tatsuro Adachi, W.K.V. Kehelpannala, Ryosuke Kato, S.P.K. Malaviarachchi, UHT granulites of the Highland Complex, Sri Lanka I: Geological and petrological background., Journal of Mineralogical and Petrological Sciences, 111, 145-156, 2016.06. |
| 19. |
Masaaki Owada, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Ippei Kitano, T. Van Tri, Hiroo Kagami, Late Permian plume-related magmatism and tectonothermal events in the Kontum Massif, central Vietnam., Journal of Mineralogical and Petrological Sciences, 111, 181-195, 2016.06. |
| 20. |
N.I. Setiawan, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Kazuhiro Yonemura, Aya Yoshimoto, Prograde and retrograde evolution of eclogites from the Bantimala Complex in South Sulawesi, Indonesia., Journal of Mineralogical and Petrological Sciences, 111, 231-247, 2016.06. |
| 21. |
Excavations at Daram and Tevsh Sites: A Report on Joint Mongolian-Japanese Excavations in Outer Mongolia. |
| 22. |
Masaaki Owada, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Ippei Kitano, Tran Van Tri, Hiroo Kagami, Late Permian plume-related magmatism and tectonothermal events in the Kontum Massif, central Vietnam, JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES, 10.2465/jmps.151019b, 111, 3, 181-195, 2016.06, The Kontum Massif is situated in the southern part of Trans Vietnam Orogenic Belt (TVOB), central Vietnam, and contains various types of magmatic and metamorphic rocks, the latter including both ultrahigh-pressure and ultrahigh-temperature units. While geochronological data indicate the existence of two main tectonothermal events at 480-420 Ma and 270-240 Ma, the most intense metamorphic and magmatic activity occurred between the Late Permian and Early Triassic due to continental collision between the South China and Indochina cratons. In this study, U-Pb LA-ICP-MS geochronological analyses of zircon obtained from two samples of metagabbro and one sample of charnockite from the massif yielded a magmatic age range of 260-250 Ma for all three samples and an inherited age of similar to 1400 Ma for the charnockite. These magmatic ages overlap with those documented for peak metamorphism in the Kontum Massif. When combined with Nd isotopic data for granitic rocks and pelitic gneisses from the region, these data suggest that the massif may have been derived from reworked continental crust. Geochemical characteristics of metagabbros from the massif reveal that the parental basaltic magma can be correlated with the Song Da igneous suite situated in the northern part of the TVOB, and was assimilated by crustal materials. The Song Da igneous suite is a member of the Emeishan large igneous province and resulted from Late Permian mantle plume activity. We conclude that the plume-related magma intruded into the deeper part of Kontum Massif and induced ultrahigh-temperature metamorphism of the lower crust by acting as a heat source.. |
| 23. |
Nugroho Imam Setiawan, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Kazuhiro Yonemura, Aya Yoshimoto, Prograde and retrograde evolution of eclogites from the Bantimala Complex in South Sulawesi, Indonesia, JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES, 10.2465/jmps.150907, 111, 3, 211-225, 2016.06, This contribution reports the metamorphic evolution of the high-pressure metamorphic rocks from the Bantimala Complex, South Sulawesi, Indonesia. Barroisite-bearing and barroisite-free eclogites were examined to assess their metamorphic evolutions, which have implications regarding the tectonic conditions in this region. The eclogites mainly consist of garnet, omphacite, phengite, rutile, and epidote, with or without barroisite. The variations in mineral assemblages are interpreted to depend upon local changes in the bulk chemical composition. The barroisite-bearing eclogites contain two types of euhedral garnet: coarse- (1-1.5 mm) and fine-grained ( |
| 24. |
Yasuhito Osanai, Krishnan Sajeev, Nobuhiko Nakano, Ippei Kitano, Wilbert K. V. Kehelpannala, Ryosuke Kato, Tatsuro Adachi, Sanjeewa P. K. Malaviarachchi, UHT granulites of the Highland Complex, Sri Lanka II: Geochronological constraints and implications for Gondwana correlation, JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES, 10.2465/jmps.151230, 111, 3, 157-169, 2016.06, The regional ultrahigh-temperature (UHT) metamorphism of the Highland Complex, Sri Lanka is well established and has an important role in our understanding of the tectonic history of the Gondwana supercontinent. U-Pb zircon dating of sapphirine-bearing Mg-Al granulites yielded two major metamorphic age populations at approximately 620-590 and 563-525 Ma with no evidence of older zircon cores. Pelitic granulite samples with a Grt-Sil-Spl-Crd assemblage have similar metamorphic ages with concordant data clusters at similar to 602, 563, and 526 Ma and inherited zircon cores aged from 2040 to 1600 Ma. The pelitic granulites also underwent two stages of metamorphism (565-520 and 622-580 Ma). Some of these pelitic granulite samples have inherited zircon cores ranging from 3060 to 760 Ma. Zircons in mafic granulite samples have age ranges of 566-533 and 620578 Ma. A calc-silicate granulite sample also has similar age populations at 591, 541, and 524 Ma. Combining these new results with previously published ages from Sri Lanka and formerly adjacent continental fragments of Gondwana, we propose that the terranes in southern Madagascar (south of Ranotsara Shear Zone), Northern and Southern Madurai and the Trivandrum Blocks of southern India, the Highland Complex of Sri Lanka, and the Skallen Group in the Lutzow-Holm Complex of East Antarctica represent a unique metamorphic belt that regionally experienced the Ediacaran-Cambrian UHT event during the amalgamation of the Gondwana super-continent.. |
| 25. |
Yasuhito Osanai, Krishnan Sajeev, Nobuhiko Nakano, Ippei Kitano, Wilbert K. V. Kehelpannala, Ryosuke Kato, Tatsuro Adachi, Sanjeewa P. K. Malaviarachchi, UHT granulites of the Highland Complex, Sri Lanka I: Geological and petrological background, JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES, 10.2465/jmps.151227, 111, 3, 145-156, 2016.06, The ultrahigh-temperature (UHT) regional metamorphism of Sri Lanka has a significant role in understanding the tectonics and formation of the Gondwana supercontinent. Sri Lanka is specifically important because of its central position in Gondwana, located between southern India, Madagascar and eastern Antarctica. In particular, the Highland Complex has been the focus of several previous studies because of the prominence of metasedimentary rocks that experienced UHT metamorphism. The central Highland Complex of Sri Lanka consists of Spr-bearing Mg-Al rich granulites intercalated with other pelitic, mafic granulites and calc-silicates, which preserve several textural evidences for UHT metamorphism. The calculated peak metamorphic conditions for the Mg-Al rich granulite yielded a temperature range from 910 to 1005 degrees C at 1.0 GPa, and the pressure varies between 0.9 to 1.2 GPa. The estimated metamorphic P-T conditions and evolution path is in good agreement with previous studies and also to that of similar rock-types from southern Madagascar, southern India and East Antarctica.. |
| 26. |
Revised stratigraphy and zircon U-Pb age data of the Hitachi metamorphic formations in the southern Abukuma Mountains, and reconstruction of the basement of the Northeast Japan Arc before the opening of the Japan Sea
We revised the stratigraphy of the Hitachi metamorphic district, based on supplementary U-Pb SHRIMP zircon ages and a review of the geochronological data available for this district. Early to late Cambrian formations and intrusives are grouped into the Cambrian Hitachi volcano-plutonic complex, which consists of the Akazawa Formation, the Tamadare Formation, meta-granites and meta-porphyry. Post-Silurian mica gneiss that occurs near the Tamadare Formation is newly defined as the Takizawa Formation, distinct from the Tamadare Formation. The Daioin and Ayukawa formations are early Carboniferous and early Permian in age, respectively. The contact between the Hitachi volcano-plutonic complex and the Daioin Formation is marked by a prolonged hiatus. There are no geochronological data available for the Omika Formation.
Zircon U-Pb age data of the Nishidohira Formation indicate deposition during the Early Cretaceous. The Nishidohira Formation was intruded by 119 Ma granitoids and was metamorphosed during 118-96 Ma under conditions of the amphibolite facies, kyanite-sillimanite zone. Sedimentation, metamorphism and exhumation, and intrusion of granitic magma in the terrain of the Nishidohira Formation occurred over a short period of time during the Cretaceous. A similar rapid metamorphism and exhumation is also recorded in the Takanuki metamorphic rocks of the Abukuma Belt.
We reconstructed the basement of the Northeast Japan Arc for the period before the opening of the Japan Sea, assuming that the Median Tectonic Line had a linear trend from the Southwest Japan Arc to the Northeast Japan Arc during the Paleogene. After the reconstruction, the Paleozoic Hitachi Formations and the Abukuma Belt move closer to the Jiamusi and Khanka blocks of Northeast China. This result indicates that the Cambrian Hitachi volcano-plutonic complex was originally marginal part of the North China Block.. |
| 27. |
Ippei Kitano, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Detrital zircon provenances for metamorphic rocks from southern Sør Rondane Mountains, East Antarctica: A new report of Archean to Mesoproterozoic zircons. , Journal of Mineralogical and Petrological Sciences, 111, 118-128, 2016.04. |
| 28. |
Ippei Kitano, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Detrital zircon provenances for metamorphic rocks from southern Sør Rondane Mountains, East Antarctica: A new report of Archean to Mesoproterozoic zircons, Journal of Mineralogical and Petrological Sciences, 10.2465/jmps.151001, 111, 2, 118-128, 2016.04, The Sør Rondane Mountains in East Antarctica consist of the various metamorphic rocks and several plutonic rocks, which are related to formation of Gondwana supercontinent. In order to understand the detrital provenances, LA-ICP-MS zircon U-Pb dating were conducted from metamorphosed sedimentary rocks in southern Sør Rondane Mountains. Detrital cores with ~ 990-730 Ma ages were recognized from zircons in the pelitic gneisses and calc-silicate rocks from Menipa, Imingfjella, Mefjell and Arden, while the pelitic gneiss from Tvihøgda exhibited the Archean to Mesoproterozoic ages of ~ 2630-1060 Ma. The Neoproterozoic zircon ages are recognized not only from metamorphosed sedimentary rocks but also from metamorphosed igneous rocks distributed in the central and southern parts of the mountains. However, the Archean to Mesoproterozoic zircon ages are rare in these areas. The results imply the detrital zircons with the Neoproterozoic ages were probably derived from neighbouring igneous rocks (present metamorphosed igneous rocks), while those with Archean to Mesoproterozoic ages have clearly different provenances because of the lack in the Neoproterozoic components. This study suggests the possibility that southern Sør Rondane Mountains can be considered to be juvenile late Mesoproterozoic to Neoproterozoic terrane partly mixed with the Archean to Mesoproterozoic components.. |
| 29. |
Nugroho Imam Setiawan, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Amril Asy'ari, Metamorphic evolution of garnet-bearing epidote-barroisite schist from the Meratus complex in South Kalimantan, Indonesia, Indonesian Journal on Geoscience, 10.17014/ijog.2.3.139-156, 2, 3, 139-156, 2015.12, This paper presents metamorphic evolution of metamorphic rocks from the Meratus Complex in South Kalimantan, Indonesia. Eight varieties of metamorphic rocks samples from this location, which are garnet-bearing epidote-barroisite schist, epidote-barroisite schist, glaucophane-quartz schist, garnet-muscovite schist, actinolite-talc schist, epidote schist, muscovite schist, and serpentinite, were investigated in detail its petrological and mineralogical characteristics by using polarization microscope and electron probe micro analyzer (EPMA). Furthermore, the pressure-temperature path of garnet-bearing epidote-barroisite schist was estimated by using mineral parageneses, reaction textures, and mineral chemistries to assess the metamorphic history. The primary stage of this rock might be represented by the assemblage of glaucophane + epidote + titanite ± paragonite. The assemblage yields 1.7 - 1.0 GPa in assumed temperature of 300 - 550 °C, which is interpreted as maximum pressure limit of prograde stage. The peak P-T condition estimated on the basis of the equilibrium of garnet rim, barroisite, phengite, epidote, and quartz, yields 547 - 690 °C and 1.1 - 1.5 GPa on the albite epidote amphibolite-facies that correspond to the depth of 38 - 50 km. The retrograde stage was presented by changing mineral compositions of amphiboles from the Si-rich barroisite to the actinolite, which lies near 0.5 GPa at 350 °C. It could be concluded that metamorphic rocks from the Meratus Complex experienced low-temperature and high-pressure conditions (blueschist-facies) prior to the peak metamorphism of the epidote amphibolite-facies. The subduction environments in Meratus Complex during Cretaceous should be responsible for this metamorphic condition.. |
| 30. |
N. Nakano, Y. Osanai, M. Owada, M. Satish-Kumar, T. Adachi, S. Jargalan, A. Yoshimoto, K. Syeryekhan, CH. Boldbaatar, Multiple growth of garnet, sillimanite/kyanite and monazite during amphibolite facies metamorphism: implications for the P-T-t and tectonic evolution of the western Altai Range, Mongolia, JOURNAL OF METAMORPHIC GEOLOGY, 10.1111/jmg.12154, 33, 9, 937-958, 2015.12, Four amphibolite facies pelitic gneisses from the western Mongolian Altai Range exhibit multistage aluminosilicate formation and various chemical-zoning patterns in garnet. Two of them contain kyanite in the matrix and sillimanite inclusions in garnet, and the others have kyanite inclusions in garnet with sillimanite or kyanite in the matrix. The Ca-zoning patterns of the garnet are different in each rock type. U-Th-Pb monazite geochronology revealed that all rock units experienced a c. 360Ma event, and three of them were also affected by a c. 260Ma event. The variations in the microstructures and garnet-zoning profiles are caused by the differences in the (i) whole-rock chemistry, (ii) pressure conditions during garnet growth at c. 360Ma and (iii) equilibrium temperatures at c.260Ma. The garnet with sillimanite inclusions records an increase in pressure at low-P (5.2-7.2kbar) and moderate temperature conditions (620-660 degrees C) at c. 360Ma. The garnet with kyanite inclusions in the other rock types was also formed during an increase in pressure but at higher pressure conditions (7.0-8.9kbar at 600-640 degrees C). The detrital zircon provenance of all the rock types is similar and is consistent with that from the sedimentary rocks in the Altai Range, suggesting that the provenance of all the rock types was a surrounding accretionary wedge. One possible scenario for the different thermal gradient is Devonian ridge subduction beneath the Altai Range, as proposed by several researchers. The subducting ridge could have supplied heat to the accretionary wedge and elevated the geotherm at c. 360Ma. The differences in the thermal gradients that resulted in varying prograde P-T paths might be due to variations in the thermal regimes in the upper plate that were generated by the subducting ridge. The c. 260Ma event is characterized by a relatively high-T/P gradient (25 degrees Ckm(-1)) and may be due to collision-related granitic activity and re-equilibrium at middle crustal depths, which caused the variations in the aluminosilicates in the matrix between the rock units.. |
| 31. |
Nobuhiko Nakano, Yasuhito Osanai, Masaaki Owada, M. Satich-Kumar, Tatsuro Adachi, S. Jargalan, Aya Yoshimoto, K. Syeryekhan, Ch. Boldbaatar, Multiple growth of garnet, sillimanite/kyanite and monazite during amphibolite facies metamorphism: Implications for the P-T-t and tectonic evolution of the western Altai Range, Mongolia., Journal of Metamorphic Geology, 33, 937-958, 2015.07. |
| 32. |
Sotaro Baba, Kenji Horie, Tomokazu Hokada, Masaaki Owada, Tatsuro Adachi, Kazuyuki Shiraishi, Multiple collisions in the East African–Antarctica Orogen: Constraints from timing of metamorphism in the Filchnerfjella and Hochlinfjellet terranes in central Dronning Maud Land., Journal of Geology, 123, 55-78, 2015.01. |
| 33. |
Sotaro Baba, Kenji Horie, Kenji Horie, Tomokazu Hokada, Tomokazu Hokada, Masaaki Owada, Tatsuro Adachi, Tatsuro Adachi, Kazuyuki Shiraishi, Kazuyuki Shiraishi, Multiple collisions in the east african–antarctica orogen: Constraints from timing of metamorphism in the filchnerfjella and hochlinfjellet terranes in central dronning maud land, Journal of Geology, 10.1086/679468, 123, 1, 55-77, 2015.01, © 2015 by The University of Chicago. All rights reserved. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon age dating was applied to several types of cordieritebearing gneisses and orthopyroxene-bearing gneiss from the basement rocks in central Dronning Maud Land, East Antarctica, to clarify the timing of tectonothermal events during the amalgamation of East and West Gondwana. The zircon ages of ca. 522–525 and 598–599 Ma were obtained in Filchnerfjella and Hochlinfjellet, respectively, and the cathodoluminescence images of analyzed zircons suggest that these were formed during high-temperature metamorphism. These two sets of ages are interpreted to represent periods that immediately followed the peak metamorphism. The dating results reveal an age gap of 80 Myr between the two areas, indicating different collisional events. In the cordierite-bearing samples in Filchnerfjella, zircon cores with oscillatory zoning have concordia ages that range from 1800 to 650Ma. These are considered to represent the ages of detrital zircons derived over a long time from different source materials. In Hochlinfjellet, the inherited detrital zircons with oscillatory zoning have concordia ages of ca. 930, 780, and 730Ma, indicating sedimentary protoliths derived from differently aged igneous source rocks, possibly formed in a subduction zone as an accretionary prism before the collision. According to previous age results, previously documented shear zones are now interpreted as representing a major tectonic boundary. The obtained age results imply that different allochthonous metamorphic terranes were assembled along the collisional zone of the East African–Antarctica Orogen during the period from 650 to 500 Ma.. |
| 34. |
LA-ICP-MS zircon U-Pb geochronology of Paleozoic granitic rocks and related igneous rocks from the Kurosegawa tectonic belt in Kyushu, Southwest Japan
The Yatsushiro area in Kyushu Island, southwest Japan, forms the western tip of the Kurosegawa tectonic belt. This area is underlain by a serpentinite melange with complicated tectonic block assemblage of granitic rocks, high-temperature (HT)-type metagabbro (Grt-Cpx granulite, Grt-amphibolite and Cpx-bearing amphibolite), and high-pressure (HP)-type metagabbro (Jd-Gln rock and Gln-bearing metagabbro). The granitic rocks and the gabbros are the protoliths of the HT-type metagabbro (HT-gabbro), and supposed to be derived from volcanic arc at an active continental margin based on their major, trace, and rare earth element (REE) chemistry, while geochemistry of the gabbro protoliths of the HP-type metagabbro (HP-gabbro) indicates mid oceanic ridge basalt (MORB)-like precursors. The laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb dating of the granitic rocks and the HT-gabbro gave the Ordovician magmatic ages (∼ 450 Ma). On the other hand, the HP-gabbro showed the igneous age of the Late Cambrian (∼ 490 Ma). Similar rock suites collected from the Kurosegawa tectonic belt in Shikoku and in the Kii-peninsula have the same chemical and age affinities according to their rock types. These results indicate the strong geological and tectonic similarities within the Kurosegawa tectonic belt. The similar assemblage is present in the South-Kitakami belt suggesting similarities in their origin.
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| 35. |
Nobuhiko Nakano, Yasuhito Osanai, M． Satish-Kumar, Tatsuro Adachi, Masaaki Owada, S. Jargalan, Ch. Boldbaatar, Aya Yoshimoto, K. Syeryekhan, Paleozoic subduction-accretion-closure histories in the west Mongolian segment of the Paleo-Asian ocean: Evidence from pressure-temperature-time-Protolith evolution of high-Mg and -Al gneisses in the Altai Mountains., Journal of Geology, 122, 283-308, 2014.05. |
| 36. |
Nobuhiko Nakano, Yasuhito Osanai, M. Satish-Kumar, Tatsuro Adachi, Masaaki Owada, Sereenen Jargalan, Chimedtseie Boldbaatar, Aya Yoshimoto, Kundyz Syeryekhan, Paleozoic Subduction-Accretion-Closure Histories in the West Mongolian Segment of the Paleo-Asian Ocean: Evidence from Pressure-Temperature-Time-Protolith Evolution of High-Mg and -Al Gneisses in the Altai Mountains, JOURNAL OF GEOLOGY, 10.1086/675665, 122, 3, 283-308, 2014.05, High-Mg, high-Al metasedimentary gneisses from the Altai Mountains, Mongolia, belonging to a subduction-accretion complex within the Central Asian Orogenic Belt can be divided into five rock types on the basis of mineral assemblages. Most rock types have high MgO and Al2O3 content and low CaO, Na2O, Rb, and Sr content. All rock types experienced a similar medium-pressure metamorphism characterized by a "hairpin"-shaped counterclockwise pressure-temperature path. U-Pb zircon and U-Th-Pb monazite ages indicated metamorphism at ca. 356 Ma and 277 Ma and inherited ages of 510-379 Ma, suggesting possible provenance to granitoids comparable to those in the Altai Mountains, China. The zircons that newly nucleated at ca. 356 Ma are characterized by high concentrations of light rare earth elements without a Ce anomaly-features common in zircons from hydrothermally altered rocks and a reducing environment. Petrological and geochronological results in this study suggest the following tectonic evolution: (1) continuous subduction and accretion of paleo-Asian oceanic crust during the Early Paleozoic, resulting in periodic granitoid magmatism in the period 510-380 Ma and a continuous supply of granite-derived sediments providing detrital zircon and monazite grains to the accretionary prism; (2) ridge subduction during the Late Devonian-Early Carboniferous (ca. 356 Ma), resulting in hydrothermal metamorphism of the accretionary prism and interaction with seawater that produced rocks with unusual whole-rock chemistry; and (3) closure of the ocean leading to continental collision in the Early Permian (ca. 277 Ma), with part of the accretionary prism squeezed into lower crustal levels to form medium-pressure metamorphic rocks.. |
| 37. |
土谷 信高, 武田 朋代, 谷 健一郎, 足立 達朗, 中野 伸彦, 小山内 康人, 木村 純一, 阿武隈山地東縁の石炭紀および白亜紀アダカイト質花崗岩類とその地質学的意義, 地質雑, 10.5575/geosoc.2014.0003, 120, 2, 37-51, 2014.02, 「割山圧砕花崗閃緑岩」は，阿武隅山地東縁の双葉断層に沿い，その東側に南北に細長く分布する岩体である．全岩化学組成の特徴から典型的なアダカイトと判断されるが，中粒でよりK2O，Srに乏しい系列と，粗粒でそれらに富む系列に2分される．前者から308 ± 3，302 ± 4 Maの，また後者から118 ± 2，117 ± 1 MaのジルコンU–Pb年代が得られた．このことから，後期石炭紀のものを従来にならい割山花崗岩体，前期白亜紀のものをあらたに高瀬花崗岩体と命名した．300 Ma頃の年代を示す花崗岩は，これまで日本列島からほとんど見つかっていなかった．今回の発見により，これまでペルム紀（約280 Ma）とされてきた日本列島の後期古生代花崗岩の形成開始年代は，後期石炭紀の300 Maまで遡ることになる．またその花崗岩がアダカイト質花崗岩であることから，300 Ma頃に始まる花崗岩形成は，海嶺沈み込みあるいは若いプレートの沈み込みで始まった可能性が指摘できる．. |
| 38. |
Yoshikuni Hiroi, Ayahiko Yanagi, Mutsumi Kato, Tomoyuki Kobayashi, Bernard Prame, Tomokazu Hokada, Madhusoodhan Satish-Kumar, Masahiro Ishikawa, Tatsuro Adachi, Yasuhito Osanai, Yoichi Motoyoshi, Kazuyuki Shiraishi, Supercooled melt inclusions in lower-crustal granulites as a consequence of rapid exhumation by channel flow, Gondwana Research, 25, 226-234, 2014.01. |
| 39. |
Yoshikuni Hiroi, Ayahiko Yanagi, Mutsumi Kato, Tomoyuki Kobayashi, Bernard Prame, Tomokazu Hokada, Madhusoodhan Satish-Kumar, Masahiro Ishikawa, Tatsuro Adachi, Yasuhito Osanai, Yoichi Motoyoshi, Kazuyuki Shiraishi, Supercooled melt inclusions in lower-crustal granulites as a consequence of rapid exhumation by channel flow, GONDWANA RESEARCH, 10.1016/j.gr.2013.04.001, 25, 1, 226-234, 2014.01, Here we report on the unexpected occurrence of felsic (granitic) inclusions with quench textures such as spherulite and dendrite (hereafter referred to as "felsite inclusions"), similar to some volcanic rocks, within garnet in presumably "slowly cooled" lower-crustal granulites of various geologic ages ranging from Early Proterozoic to Middle Paleozoic and wide global distribution (the Limpopo Belt, the Grenville Province, the Liltzow-Holm Complex of East Antarctica, the Highland Complex of Sri Lanka, and the southern Bohemian Massif). The well-preserved textures of felsite inclusions are indicative of melts formed by anatexis during high-pressure and high-temperature metamorphism, crystallization under far-from-equilibrium conditions (at >50 degrees C undercooling) and subsequent rapid cooling. The occurrence of felsite inclusions in granulites in restricted tectonostratigraphic zones in Sri Lanka, among other examples, may be the first geologic evidence for fast exhumation of lower-crustal rocks to andalusite-stable upper-crustal conditions by channel flow in a continental collision orogen. We hypothesize that granulites ascend episodically along discrete high-strain zones and cool as fast as some felsic magmas. This conclusion sheds new light on the debate regarding the deep crustal processes and necessitates changes to fundamental beliefs about exhumation rates based on rates of plate convergence (1-10 cm/year). (C) 2013 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.. |
| 40. |
Toshisuke Kawasaki, Tatsuro Adachi, Nobuhiko Nakano, Yasuhito Osanai, Possible armalcolite pseudomorph-bearing garnet-sillimanite gneiss from Skallevikshalsen, Lützow-Holm Complex, East Antarctica: Implications for ultrahigh-temperature metamorphism, Geological Society Special Publication, 10.1144/SP383.2, 383, 1, 135-167, 2013.10, A possible armalcolite pseudomorph has been identified in garnet-sillimanite gneiss from Skallevikshalsen, located c. 30 km NE of Rundvågshetta, in a terrane with the highest metamorphic grade in the Lützow-Holm Complex, East Antarctica. It occurs as an Fe-Mg-Ti compositional domain consisting of ilmenite, rutile and pseudorutile, partially mantled by rutile within ilmenite. The domain yields an average XMg of 0.171±0.036 exceeding by 3 wt% TiO2from armalcolite stoichiometry, while the analysis closest to armalcolite stoichiometry has an XMgvalue close to 0.202. Host ilmenite with 0.4 mol% hematite is in contact with prismatic sillimanite, quartz, plagioclase and K-feldspar. In run products of annealing experiments performed to investigate the origin of the pseudomorph, armalcolite-ilmenite reaction coronae were developed around relict rutile in rock fragments of quartz eclogite from the Higashi-Akaishi mass of the Sanbagawa belt, central Shikoku, Japan. The experiments were carried out at 1 atm and 960-1050°C with wü stite-magnetite buffer and imply a minimum temperature of 1290°C for armalcolite stability when extrapolated to Skallevikshalsen pressures of 1.0 GPa. Mineral chemistry thermobarometry for Skallevikshalsen yields a metamorphic path with P-T peak conditions of 0.88-1.1 GPa and 970-1050°C, followed by retrograde metamorphism at 0.6 GPa and 780°C, and finally metasomatic alteration at c. 630°C. This P-T path matches that for similar ultrahigh-temperature metamorphic rocks from Rundvågshetta and Sri Lanka, and is markedly lower in temperature than the unreasonable estimates based on armalcolite stability. This discrepancy is inferred to reflect chemical impurities in armalcolite that lower its minimum temperature stability by more than 200°C. © The Geological Society of London 2013.. |
| 41. |
Tatsuro Adachi, Tomokazu Hokada, Tomokazu Hokada, Yasuhito Osanai, Nobuhiko Nakano, Sotaro Baba, Tsuyoshi Toyoshima, Contrasting metamorphic records and their implications for tectonic process in the central Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica, Geological Society Special Publication, 10.1144/SP383.4, 383, 1, 113-133, 2013.10. |
| 42. |
Yasuhito Osanai, Yoshifumi Nogi, Sotaro Baba, Nobuhiko Nakano, Tatsuro Adachi, Tomokazu Hokada, Tsuyoshi Toyoshima, Masaaki Owada, Madhusoodhan Satish-Kumar, Atsushi Kamei, Ippei Kitano, Geologic evolution of the Sør Rondane Mountains, East Antarctica: Collision tectonics proposed based on metamorphic processes and magnetic anomalies, Precambrian Research, 10.1016/j.precamres.2013.05.017, 234, 8-29, 2013.09. |
| 43. |
Tsuyoshi Toyoshima, Yasuhito Osanai, Sotaro Baba, Tomokazu Hokada, Nobuhiko Nakano, Tatsuro Adachi, Makoto Otsubo, Masahiro Ishikawa, Yoshifumi Nogi, Sinistral transpressional and extensional tectonics in Dronning Maud Land, East Antarctica, including the Sør Rondane Mountains, Precambrian Research, 10.1016/j.precamres.2013.05.010, 234, 30-46, 2013.09. |
| 44. |
Nobuhiko Nakano, Yasuhito Osanai, Atsushi Kamei, M. Satish-Kumar, Tatsuro Adachi, Tomokazu Hokada, Sotaro Baba, Tsuyoshi Toyoshima, Multiple thermal events recorded in metamorphosed carbonate and associated rocks from the southern Austkampane region in the Sør Rondane Mountains, East Antarctica: A protracted Neoproterozoic history at the Gondwana suture zone, Precambrian Research, 10.1016/j.precamres.2012.10.009, 234, 161-182, 2013.09, This paper provides a detailed analysis of the geological evolution of the southern Austkampane region in the Sør Rondane Mountains, Antarctica, using geological and petrographical observations, geochemical, geochronological, radiogenic, and stable isotopic data, and metamorphic petrological techniques. The study area is dominated by felsic gneisses intercalated with mafic and carbonate rocks. Carbonate rocks include several calc-silicate and mafic to ultramafic blocks with carbonatite-like characteristics. The new data presented here indicate the presence of five important thermal events in the geological history of the region, at c. 1060, 770-750, 655-635, 560-545, and |
| 45. |
Tatsuro Adachi, Yasuhito Osanai, Tomokazu Hokada, Nobuhiko Nakano, Sotaro Baba, Tsuyoshi Toyoshima, Timing of metamorphism in the central Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica: Constrains from SHRIMP zircon and EPMA monazite dating, Precambrian Research, 10.1016/j.precamres.2012.11.011, 234, 136-160, 2013.09, In order to understand the tectonic evolution of the Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica, sensitive high resolution ion microprobe (SHRIMP) U-Pb zircon dating and electron probe micro analyzer (EPMA) U-Th-Pb monazite dating were carried out on igneous rocks and metamorphic rocks whose P. T conditions have been well-constrained. Metamorphic rocks from northern part of Austkampane area recording a clockwise P. T path yield 600-640. Ma as the timing of peak granulite-facies metamorphism and 550-570. Ma for subsequent retrograde metamorphism. The same age relations were obtained from the metamorphic rocks from Brattnipene and eastern Menipa areas recording an anti-clockwise P. T path. Contemporaneous peak metamorphism with contrasting P. T paths can be explained by thrusting up (obduction) of the unit showing a clockwise P. T path onto the unit showing an anti-clockwise P-T path at ca. 660-640. Ma, which is considered to be the main metamorphic event. Metamorphic rocks from Lunckeryggen, southern Walnumfjella and western Menipa areas that preserve amphibolite-facies peak metamorphic conditions and are unaffected by the retrograde hydration, yield ca. 550. Ma. Ages of 500-550. Ma were also obtained on igneous rocks distributed throughout the whole area. Based on the close age relation between metamorphism of amphibolite-facies rocks and igneous activity, it is likely that metamorphism at ca. 550. Ma was caused by emplacement of voluminous igneous bodies. These precise correlation of metamorphic evolution and age would provide strong constraints on the construction of a tectonic model for Gondwana amalgamation. © 2012 Elsevier B.V.. |
| 46. |
Tomokazu Hokada, Tomokazu Hokada, Kenji Horie, Tatsuro Adachi, Yasuhito Osanai, Nobuhiko Nakano, Sotaro Baba, Tsuyoshi Toyoshima, Unraveling the metamorphic history at the crossing of Neoproterozoic orogens, Sør Rondane Mountains, East Antarctica: Constraints from U-Th-Pb geochronology, petrography, and REE geochemistry, Precambrian Research, 10.1016/j.precamres.2012.12.002, 234, 183-209, 2013.09, The Sør Rondane Mountains in East Antarctica preserve two stages of tectonothermal events, at c. 650-600. Ma and c. 560-550. Ma, each of which is also widely preserved elsewhere in Gondwana within tectonic suture zones/orogens, although both ages of tectonothermal events are only rarely documented together in these other parts of Gondwana. A geochronological and petrogenetic study of highly retrogressed garnet-sillimanite-biotite-bearing pelitic gneiss, along with three generations of associated sub-concordant to discordant leucocratic felsic veins, which together are exposed in the southern Austkampane area in the central part of the Sør Rondane Mountains, provides important new constraints on the geological and age relationships between these two regional tectonothermal events. U-Pb SHRIMP dating of zircon grains isolated from the host garnet-sillimanite-biotite gneiss yields at least four distinct zircon age populations of c. 2800-720. Ma, c. 700. Ma, 640-630. Ma, and ~500. Ma. Chondrite-normalized REE patterns indicate that a pooled age of 637. ±. 6. Ma represents the timing of recrystallization of metamorphic HREE-depleted zircon, during which the zircon was in equilibrium with garnet. The earliest emplaced leucocratic vein (LV-1), which is partly intermingled with the host garnet-sillimanite-biotite gneiss (and enclosing garnet-bearing pelitic enclaves), contains a population of zircon grains that yielded a crystallization age of 635. ±. 4. Ma, which is almost identical to the age of zircons found within the host pelitic gneiss. The second-generation leucocratic vein (LV-2) occurs as a part of a set of sub-concordant veins/leucosomes comprising mostly biotite and muscovite. Although these particular leucosomes do not contain any zircon, they were found to contain abundant monazite, which yielded U-Pb ages of 640-630. Ma along with some older (relict) ~700. Ma ages. The third-generation leucocratic vein (LV-3) was sampled from a suite of pegmatitic veins that discordantly crosscut both the host pelitic gneisses and the older two sets of leucocratic veins. These third-generation veins contain magmatic zircons that exhibit HREE-enriched patterns typical of magmatic zircon crystallization, and which yielded a crystallization age of 550. ±. 3. Ma. The data imply that a major high-grade metamorphic event (possibly at granulite facies) took place in this region along with a subsequent late-stage re-hydration event, all within a relatively narrow time interval of |
| 47. |
Seishiro Furuyama, Akihiro Kano, Yoko Kunimitsu, Yasuhito Osanai, Tatsuro Adachi, Xinchun Liu, Wei Wang, Ediacaran mineralized microfossils from the basinal facies of the Doushantuo Formation in northwestern Hunan Province, South China, Paleontological Research, 10.2517/1342-8144-17.3.241, 17, 3, 241-250, 2013.08, The Ediacaran sediments in the Yangtze Block preserve valuable records of biological evolution and drastic climate changes. However, most of the Ediacaran fossil occurrences have been reported from the shallow platformal facies, and few fossils have been described from the deep basinal facies in the Yangtze Block. Here, we report mineralized microfossils from the basinal facies of the Ediacaran Doushantuo Formation at Fengtan in northwestern Hunan Province, China. The submillimeter-sized microfossils with oval-discoidal shapes have apatite walls of variable thickness. The lack of morphological regularity, ornamentation, and distinct apertures indicates that they are not protozoan shells or tests. The apatite walls have more likely replaced the recalcitrant organic walls of prasinophyte phycomata and/or algal resting cysts. These fell from shallow water and were quickly preserved in a deeper setting, associated with a local decline in pH caused by bacterial decomposition and elevated concentration of phosphate in seawater. This discovery provides new insight into the stratigraphic correlation between the shallow and basinal facies of the Chinese Ediacaran. © by the Palaeontological Society of Japan.. |
| 48. |
Seishiro Furuyama, Akihiro Kano, Youko Kunimitsu, Tatsuro Adachi, Yasuhito Osanai, Xinchun Liu, Wei Wang, Ediacaran mineralized microfossils from the basinal facies of the Doushantuo Formation in northwestern Hunan Province, South China, Paleontological Research, 17, 241-250, 2013.04. |
| 49. |
Kazuhiro Yonemura, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Punya Charusiri, Tun Naing Zaw, EPMA u-th-pb monazite dating of metamorphic rocks from the mogok metamorphic belt, central myanmar, Journal of Mineralogical and Petrological Sciences, 10.2465/jmps.121019a, 108, 3, 184-188, 2013.04. |
| 50. |
Aya Yoshimoto, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Kazuhiro Yonemura, Hideo Ishizuka, U-Pb detrital zircon dating of pelitic schists and quartzite from the Kurosegawa Tectonic Zone, Southwest Japan, Journal of Mineralogical and Petrological Sciences, 10.2465/jmps.121022a, 108, 3, 178-183, 2013.04. |
| 51. |
Nugroho Imam Setiawan, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Kazuhiro Yonemura, Aya Yoshimoto, Joko Wahyudiono, Kaharuddin Mamma, An overview of metamorphic geology from central Indonesia : Importance of South Sulawesi, Central Java and South-West Kalimantan metamorphic terranes, Bulletin of the Graduate School of Social and Cultural Studies, Kyushu University, 19, 39-55, 2013.03. |
| 52. |
Masaaki Owada, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Kazuhiro Yonemura, Aya Yoshimoto, Madhusoodhan Satish-Kumar, Sereenen Jargalan, Chimedtseye Boldbaatar, An early Paleozoic tectonothermal event in western Mongolia: Implications for regional extension of the Cambrian orogenic belt., Journal of Mineralogical and Petrological Sciences, 108, 1, 42-46, 2013.03. |
| 53. |
Nobutaka Tsuchiya, Tomoyuki Shibata, Masako Yoshikawa, Yoshiko Adachi, Sumio Miyashita, Tatsuro Adachi, Nobuhiko Nakano, Yasuhito Osanai, Petrology of Lasail plutonic complex, northern Oman ophiolite, Oman: An example of arc-like magmatism associated with ophiolite detachment., Lithos, 156-159, 120-138, 2013.03. |
| 54. |
Masaaki Owada, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Kazuhiro Yonemura, Aya Yoshimoto, Madsudan Satish-Kumar, Jargalan Sereenen, Chimedteie Boldbaatar, An early Paleozoic tectonothermal event in western Mongolia: Implications for regional extension of the Cambrian orogenic belt, JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES, 10.2465/jmps.121021a, 108, 1, 42-46, 2013.02, The Central Asian Orogenic Belt consists of various terranes amalgamated in several periods from the Late Pre-cambrian/Early Paleozoic to the Late Mesozoic. Mongolia is situated in the center of this belt. Foliated garnet granite (Grt metagranite) and andalusite-bearing massive leucogranite (Leucogranite) are exposed in the Hanhohiyn region of northwest Mongolia. The results of monazite Th-U-Pb dating of the Grt metagranite and Leucogranite give ages of 508 +/- 10 Ma and 496 +/- 4 Ma, respectively. Cambrian granite with an age of similar to 500 Ma is also reported from the south-central part of Mongolia. Combined with previously published age data of metamorphic and intrusive rocks, these results show that the Cambrian orogenic belt spans over 800 km, from the northwest to the south-central part of Mongolia.. |
| 55. |
Atsushi Kamei, Horie Kenji, Masaaki Owada, Masaki Yuhara, Nobuhiko Nakano, Yasuhito Osanai, Tatsuro Adachi, Yuki Hara, Madoka Terao, Shinjiro Teuchi, Toshiaki Shimura, Kazuhiro Tsukada, Tomokazu Hokada, Chika Iwata, Kazuyuki Shiraishi, Hideo Ishizuka, Yuhei Takahashi, Late Proterozoic juvenile arc metatonalite and adakitic intrusions in the Sør Rondane Mountains, eastern Dronning Maud Land, Antarctica, Precambrian Research, 234, 47-62, 2013.01. |
| 56. |
Nobuhiko Nakano, Yasuhito Osanai, Tatsuro Adachi, Atsushi Kamei, Madhusoodhan Satish-Kumar, Tomokazu Hokada, Sotaro Baba, Tsuyoshi Toyoshima, Multiple thermal events recorded in metamorphosed carbonate and associated rocks from the southern Austkampane region in the Sør Rondane Mountains, East Antarctica: A protracted Neoproterozoic history at the Gondwana suture zone, Precambrian Research, 234, 161-182, 2013.01. |
| 57. |
Tomokazu Hokada, Kenji Horie, Tatsuro Adachi, Yasuhito Osanai, Nobuhiko Nakano, Sotaro Baba, Tsuyoshi Toyoshima, Unraveling the metamorphic history at the crossing of Neoproterozoic orogens, Sør Rondane Mountains, East Antarctica: Constraints from U–Th–Pb geochronology, petrography, and REE geochemistry, Precambrian Research, 234, 183-209, 2013.01. |
| 58. |
Sotaro Baba, Yasuhito Osanai, Nobuhiko Nakano, Masaaki Owada, Tomokazu Hokada, Kenji Horie, Tatsuro Adachi, Tsuyoshi Toyoshima, Counterclockwise P-T path and isobaric cooling of metapelites from Brattnipene, Sør Rondane Mountains, East Antarctica: Implications for a tectonothermal event at the proto-Gondwana margin, Precambrian Research, 234, 210-228, 2013.01. |
| 59. |
Tatsuro Adachi, Yasuhito Osanai, Tomokazu Hokada, Nobuhiko Nakano, Sotaro Baba, Tsuyoshi Toyoshima, Timing of metamorphism in the central Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica: Constrains from SHRIMP zircon and EPMA monazite dating, Precambrian Research, 234, 136-160, 2013.01. |
| 60. |
Nobutaka Tsuchiya, Tomoyuki Shibata, Masako Yoshikawa, Yoshiko Adachi, Sumio Miyashita, Tatsuro Adachi, Nobuhiko Nakano, Yasuhito Osanai, Petrology of Lasail plutonic complex, northern Oman ophiolite, Oman: An example of arc-like magmatism associated with ophiolite detachment, LITHOS, 10.1016/j.lithos.2012.10.013, 156, 120-138, 2013.01, Lasail plutonic complex (4.7x3.8 km), as a typical example of late stage intrusive rocks, is located to the south of Wadi Jizi, and intrudes into the base of V1 volcanic rocks and sheeted dike complex. The Lasail plutonic complex consists of various rock types ranging from ultramafic cumulates to tonalite, and is associated with minor amounts of axis stage gabbro to quartz diorite. These rocks are classified into the following eleven rock types: massive gabbro 1, quartz diorite 1 (axis stage intrusive rocks), olivine websterite, olivine gabbronorite, gabbronorite, hornblende gabbronorite, leucogabbronorite (layered gabbros), massive gabbro 2, diorite, quartz diorite 2, and tonalite (late stage intrusive rocks). The layered gabbros are intruded by the massive gabbro 2, and often occur as large irregular blocks in the massive gabbro 2. The massive gabbro 2 intrudes into the layered gabbros, and sometimes grades into hornblende gabbronorite layer of the layered gabbros. In some places, anastomosing veins of the hornblende quartz gabbronorite injected into the gabbronorite, which continue to the layer of leucogabbronorite. These gabbroic rocks are intruded by small intrusions of diorite, quartz diorite 2, and tonalite. The quartz diorite 2 forms rather larger intrusive bodies that intrude into the gabbroic rocks in the higher level. The tonalite occurs as thin dike and sheet mainly in the layered gabbros. N-MORE normalized trace element patterns for the massive gabbro 2 are characterized by enrichment of LILEs relative to REEs, and resemble to 'subduction component' from the island arc tholeiite except a weak enrichment for middle to light REE and P. In contrast, the massive gabbro 1 (axis stage gabbro) shows rather flat pattern similar to MORE with no remarkable 'subduction component'. From the examination of Sr and Nd isotopic signature, the Lasail plutonic rocks are characterized by higher epsilon-Sr values than those of MORE. This suggests that the primitive magma of Lasail complex was influenced by the rocks with higher epsilon-Sr values than those of MORE, e.g., the axis stage rocks interacted with seawater. These lines of evidence suggests that the massive gabbro 2 was formed by the partial melting of residual MORE mantle which is contaminated with slab melt derived from the axis stage rocks interacted with seawater. In addition, petrogenesis of felsic rocks in the Lasail complex can be explained by the partial melting model of pre-existing layered gabbro. U Pb zircon ages analyzed by LA-ICPMS are 100 +/- 2 and 99 +/- 2 Ma for late stage tonalite and 100 +/- 1 Ma for axis stage quartz diorite. These ages are slightly older than the ages reported for felsic rocks in the Oman ophiolite (ca., 95 Ma), and suggest that the conversion from ridge stage to detachment stage took place rapidly. (C) 2012 Elsevier B.V. All rights reserved.. |
| 61. |
Sotaro Baba, Yasuhito Osanai, Nobuhiko Nakano, Masaaki Owada, Tomokazu Hokada, Tomokazu Hokada, Kenji Horie, Tatsuro Adachi, Tsuyoshi Toyoshima, Counterclockwise P-T path and isobaric cooling of metapelites from Brattnipene, Sør Rondane Mountains, East Antarctica: Implications for a tectonothermal event at the proto-Gondwana margin, Precambrian Research, 10.1016/j.precamres.2012.10.002, 234, 210-228, 2012.10, In this paper we provide evidence for a counterclockwise P-T path and isobaric cooling for metapelitic rocks from the Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica. The counterclockwise path was determined using the following mineral textures and relationships: (1) garnet coronae on sillimanite where the sillimanite is associated with spinel in orthopyroxene-bearing granulite; (2) garnets that contain inclusions of spinel, sillimanite, and corundum, and where the sillimanite and corundum have sparse tiny spinel inclusions; (3) the garnet-orthopyroxene-plagioclase-quartz equilibria relationships using the contrasting compositions of high-Mg garnet - plagioclase inclusions and high-Ca garnet coronae - matrix plagioclase point to an increase in pressure. The peak metamorphic conditions were determined by thermobarometry and pseudosection analyses, and are consistently within the ranges 850-900°C and 8-9kbar. Orthopyroxene porphyroblasts close to garnet coronae have relatively high Al2O3contents (~6.1wt.%), consistent with the highest temperature conditions reported so far from the Sør Rondane Mountains. Prismatic subidioblastic staurolite formed as a secondary mineral along the margins of the garnets, and this retrograde staurolite indicates a back-reaction during isobaric cooling. The conditions for staurolite formation are taken to be 680-700°C and 8.5kbar using isopleths, and this is consistent with the appearance of secondary kyanite in the matrix. On the basis of the metamorphic P-T path and the tectonic setting of the precursor rocks, the following tentative scenarios can be inferred: (1) the heat source for the early sequence of metamorphism was derived from advective heat flow at an active continental margin, and (2) the subsequent increase in pressure was caused by overthrusting or obduction of either oceanic crust or oceanic island arc onto the Brattnipene region. These tectonothermal events took place along a possible proto-Gondwana margin at ca. 650-600Ma. © 2012 Elsevier B.V.. |
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Atsushi Kamei, Kenji Horie, Masaaki Owada, Masaki Yuhara, Nobuhiko Nakano, Yasuhito Osanai, Tatsuro Adachi, Yuki Hara, Madoka Terao, Shinjiro Teuchi, Toshiaki Shimura, Kazuhiro Tsukada, Tomokazu Hokada, Chika Iwata, Kazuyuki Shiraishi, Hideo Ishizuka, Yuhei Takahashi, Late Proterozoic juvenile arc metatonalite and adakitic intrusions in the Sør Rondane Mountains, eastern Dronning Maud Land, Antarctica, Precambrian Research, 10.1016/j.precamres.2012.09.026, 234, 47-62, 2012.10, This study is a detailed investigation of the petrology and geochronology of the Late Proterozoic metatonalite in the Sør Rondane Mountains, eastern Dronning Maud Land, Antarctica. Metatonalite is dominant over roughly 100×20km2area in the southwestern end of the mountain range and is classified into five lithologies: gneissose Bt-Hbl metatonalite, weak gneissose Hbl-Bt metatonalite, Hbl metagabbro, Hbl-Bt tonalitic gneiss, and Bt metatonalite. The gneissose Bt-Hbl metatonalite is the main lithotype widely distributed over this area, which is geochemically categorized as low-K tholeiitic granitoid. Petrological studies suggest that the tholeiitic magma was derived from low-K basalt melting at the crustal depth, and the most plausible tectonic setting is a juvenile oceanic arc. The other four metaplutonic rocks are scattered as stocks or small intrusions in this area. They are geochemically regarded as calc-alkaline adakites related to oceanic slab melting. U-Pb SHRIMP zircon ages of the tholeiitic metatonalite are concentrated at 998-995Ma, whereas the calc-alkaline adakitic rocks are younger and divided between ages 945-920Ma and 772Ma. We believe that the tholeiitic metatonalite was formed first as a juvenile arc component between 998 and 995Ma, followed by adakitic magmatism and oceanic slab melting at 945-920Ma and 772Ma. Magmatism during this stage is not recorded in the western to central Dronning Maud Land. Moreover, the exposure of an adakitic equivalent continues at the farther eastern side of the Sør Rondane Mountains. This suggests that the tectonic framework of the Sør Rondane Mountains, eastern Dronning Maud Land, is different from the western to central Dronning Maud Land. © 2012 Elsevier B.V... |
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Identification of the Origin for Mold Stones, Processing of Mold Material and Distribution in Northern Kyushu in the Yayoi Period. |
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足立 達朗, 小山内 康人, 中野 伸彦, Owada Masaaki, 浮嶽地域に産する泥質グラニュライトのLA-ICP-MS U－Pbジルコン年代とFE-EPMA U－Th－Pbモナザイト年代, 地質雑, 10.5575/geosoc.2011.0022, 118, 1, 39-52, 2012.01, 脊振山地・浮嶽に産する泥質グラニュライトとその周囲の糸島花崗閃緑岩について，LA-ICP-MSジルコンU－Pb年代とFE-EPMAモナザイトU－Th－Pb年代を測定した．糸島花崗閃緑岩からはジルコンU－Pb法で102 ± 2 Maの火成年代が得られた．また，泥質グラニュライトのジルコンの縁辺部からは105 ± 2 MaのU－Pb年代が得られた．この年代は100－120 MaのモナザイトU－Th－Pb年代と調和的である．ジルコンの核部からは，400－510 Maに集中する砕屑性年代が得られ，最も若い年代は360 Maであった．この砕屑性ジルコンの年代分布は蓮華変成岩に類似するが，変成作用の時期や条件が異なる．浮嶽の泥質グラニュライトが示す変成年代は100－120 Maであり，肥後変成岩の再加熱の時期あるいは領家変成岩の主要な変成作用の時期とほぼ同時期である．しかし砕屑性ジルコンの年代分布が一致せず，これらの変成岩は互いに異なる後背地に由来することが考えられるため，直接の対比は困難である．. |
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The oldest formations in Japan
茨城県多賀山地の日立変成古生層は，産出化石により前期石炭紀以降の地層とされてきた．しかし最近広範にSHRIMP年代が測定され，多賀山地に日本最古のカンブリア系が60 km2以上にわたって広く分布することが明らかになった．A班では，原岩構造のわかるカンブリア系のうち，枕状構造や発泡構造，急冷組織などがみられる火山岩を原岩とする赤沢層と，堆積構造を残す砂泥質堆積岩や礫岩を原岩とする西堂平層，さらに赤沢層に貫入するカンブリア紀花崗岩類を見学する．また，赤沢層を不整合で覆う石炭系大雄院層基底部の礫岩などを見学する．今後，これらの露頭は日本におけるカンブリア系の模式地となることが予想される．今回は当初の研究成果に基づくものであり，今後さらに多くの研究者によってより深く研究され，日本列島形成の初期の様子が明らかになるであろう．. |
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Nobuhiko Nakano, Yasuhito Osanai, Sotaro Baba, Tatsuro Adachi, Tomokazu Hokada, Tsuyoshi Toyoshima, Inferred ultrahigh-temperature metamorphism of amphibolitized olivine granulite from the Sør Rondane Mountains, East Antarctica, Polar Science, 5, 3, 345-359, 2011.09. |
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Nobuhiko Nakano, Yasuhito Osanai, Sotaro Baba, Tatsuro Adachi, Tomokazu Hokada, Tsuyoshi Toyoshima, Inferred ultrahigh-temperature metamorphism of amphibolitized olivine granulite from the Sør Rondane Mountains, East Antarctica, Polar Science, 10.1016/j.polar.2011.03.005, 5, 3, 345-359, 2011.09, This paper reports the first evidence of ultrahigh-temperature (UHT) metamorphism from the Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica, which is evident as orthopyroxene. +. spinel symplectite in an amphibolitized mafic granulite. The granulite consists of olivine, orthopyroxene, clinopyroxene, pargasitic amphibole, plagioclase, and ilmenite, and it possesses a within-plate alkali basalt signature. The local bulk chemical composition of symplectite, major and trace element compositions, and thermodynamic calculations for the symplectite, suggest the presence of garnet at the high-pressure stage and that the symplectite formed from garnet, olivine, and primary orthopyroxene by decompression from more than 12. kbar at 1000°C. The granulite records a subsequent amphibolite-facies overprint ( |
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Michio Tagiri, Daniel J. Dankley, Tatsuro Adachi, Yoshikuni Hiroi, C. Mark Fanning, SHRIMP dating of magmatism in the Hitachi metamorphic terrane, Abukuma Belt, Japan: Evidence for a Cambrian volcanic arc, Island Arc, 20, 2, 259-279, 2011.06. |
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Michio Tagiri, Daniel J. Dunkley, Tatsuro Adachi, Yoshikuni Hiroi, C. Mark Fanning, SHRIMP dating of magmatism in the Hitachi metamorphic terrane, Abukuma Belt, Japan: Evidence for a Cambrian volcanic arc, ISLAND ARC, 10.1111/j.1440-1738.2011.00764.x, 20, 2, 259-279, 2011.06, Ion microprobe dating of zircon from meta-igneous samples of the Hitachi metamorphic terrane of eastern Japan yields Cambrian magmatic ages. Tuffaceous schist from the Nishidohira Formation contains ca 510 Ma zircon, overlapping in age with hornblende gneiss from the Tamadare Formation (ca 507 Ma), and meta-andesite (ca 507 Ma) and metaporphyry (ca 505 Ma) from the Akazawa Formation. The latter is unconformably overlain by the Carboniferous Daioin Formation, in which a granite boulder from metaconglomerate yields a magmatic age of ca 500 Ma. This date overlaps a previous estimate for granite that intrudes the Akazawa Formation. Intrusive, volcanic, and volcaniclastic lithologies are products of a Cambrian volcanic arc associated with a continental shelf, as demonstrated by the presence of arkose and conglomerate in the lowermost Nishidohira Formation. Granitic magmatism of Cambrian age is unknown elsewhere in Japan, except for a single locality in far western Japan with a similar geological context. Such magmatism is also unknown on the adjacent Asian continental margin, with the exception of the Khanka block in far northeastern China. A 'great hiatus' in the Paleozoic stratigraphy of the Sino-Korean block also exists in the Hitachi terrane between Cambrian volcanic arc rocks and Early Carboniferous conglomerate, and may indicate a common paleogeographic provenance.. |
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Nobuhiko Nakano, Yasuhito Osanai, Tatsuro Adachi, Major and trace element zoning of euhedral garnet in high-grade (> 900 ˚C) mafic granulite from the Song Ma Suture zone, northern Vietnam, Journal of Mineralogical and Petrological Sciences, 105, 5, 222-234, 2010.10. |
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Nobuhiko Nakano, Yasuhito Osanai, Tatsuro Adachi, Major and trace element zoning of euhedral garnet in high-grade (> 900 °C) mafic granulite from the Song Ma Suture zone, northern Vietnam, Journal of Mineralogical and Petrological Sciences, 10.2465/jmps.100620a, 105, 5, 268-273, 2010.10, In this study, mafic granulite and related leucosomes from the Song Ma Suture zone in northern Vietnam were investigated. Euhedral garnet appears in both granulites and leucosomes, whereas the former is partly to mostly replaced by orthopyroxene + plagioclase symplectite. Most garnets occurring both in granulite and leucosome contain an Mg-rich and Ca-poor core as well as an Mg-poor and Ca-rich mantle. Garnets in leucosomes have an Mg-rich and Ca-poor thin rim. Amphibole + quartz association is observed only in the core and mantle and not in the rim and matrix. Garnet core is characterized by flat middle to heavy rare earth element (REE) patterns and depletion of light REEs. The rim also contains high concentrations of middle REEs, whereas light and heavy REEs are further depleted in comparison with the core. The REE patterns of the mantle are completely different from core and rim, which show considerable depletion in light to middle REEs and extreme enrichment in heavy REEs. The petrographical features and REE patterns of the associated mineral phases suggest that the complex chemical zonation of garnet might be formed by dehydration melting of amphibole and multiple recrystallization of garnet.. |
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Hitachi Metamorphic Rocks : Occurrence and Geology of Meta-granitic Rocks with Cambrian SHRIMP Zircon Age
Hitachi metamorphic rocks located in the southern part of the Abukuma Mountains, Northeast Japan, distinctively contain meta-volcanic rocks and meta/sheared granitoids. The igneous ages of meta-granite and meta-porphyry from the Hitachi metamorphic rocks were determined by the SHRIMP zircon method. In this paper, we describe occurrence, petrography, and petrochemical characteristics of these studied rocks. Meta-porphyry, with an igneous age of 506 Ma, intrudes into the meta-volcanic rocks of the Akazawa Formation of the Hitachi metamorphic rocks and has a micrographic texture and a spherulitic texture of an igneous origin. Previous studies have already reported an igneous age of 491 Ma for meta/sheared granitoids using the SHRIMP zircon method. Cambrian meta/sheared granitoid samples occur widely as a granitic body in the northeastern part of the Hitachi metamorphic rocks. (A) Meta-granite of the same age (498 Ma) as the sample used for the above dating is found as boulders in meta-conglomerates. The meta-conglomerate, which is found in the Daioin Formation of the Hitachi metamorphic rocks, lies unconformably on a Cambrian meta-granite body. Both meta-volcanic rocks and meta/sheared granitoids have chemical characteristics commonly associated with island arc volcanism. As such, the Akazawa Formation is likely to have originated in the Cambrian era, although we have no SHRIMP age for meta-volcanic rocks of the Akazawa Formation.. |
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Tatsuro Adachi, Tomokazu Hokada, Yasuhito Osanai, Tsuyoshi Toyoshima, Sotaro Baba, Nobuhiko Nakano, Titanium behavior in quartz during retrograde hydration: Occurrence of rutile exsolution and implications for metamorphic processes in the Sør Rondane Mountains, East Antarctica, Polar Science, 3, 4, 222-234, 2010.01. |
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Tatsuro Adachi, Tomokazu Hokada, Tomokazu Hokada, Yasuhito Osanai, Tsuyoshi Toyoshima, Sotaro Baba, Nobuhiko Nakano, Titanium behavior in quartz during retrograde hydration: Occurrence of rutile exsolution and implications for metamorphic processes in the Sør Rondane Mountains, East Antarctica, Polar Science, 10.1016/j.polar.2009.08.005, 3, 4, 222-234, 2010.01, In the central Sør Rondane Mountains, East Antarctica, orthopyroxene felsic gneiss (OPG) was converted to hornblende-biotite felsic gneiss (HBG) by hydration that accompanied the intrusion of pegmatite. The retrograde HBG contains exsolved rutile in quartz. The composition of orthopyroxene and clinopyroxene in OPG suggests a temperature of 840 °C (interpreted as the near-peak temperature), and the composition of hornblende and plagioclase in HBG suggests a temperature of 670-700 °C (interpreted as the temperature during hydration). Ti concentrations in quartz were measured using an electron probe micro-analyzer, and Ti-in-quartz thermometers were applied. Measured Ti concentrations were 110 ppm (equivalent to 760-820 °C) for homogeneous quartz from OPG and 35 ppm (650-700 °C) for an exsolution-free area of a quartz grain from HBG. The pre-exsolution Ti concentration in quartz from HBG was reconstructed with 100 μm beam diameter and 25 kV of accelerating voltage, giving 103 ppm, similar to the value obtained for homogeneous quartz in OPG. The temperatures obtained using a Ti-in-quartz thermometer are consistent with those estimated using other thermometers. Although analysis of the main constitute minerals in HBG yields the conditions of hydration, the reconstructed pre-exsolution Ti content in quartz within HBG yields the pre-hydration conditions. Thus, the Ti-in-quartz thermometer is a potentially powerful tool with which to identify the peak or near-peak temperature conditions, even for retrogressed metamorphic rocks. © 2009 Elsevier B.V. and NIPR.. |
