| Pe trology and SHRIMP zircon geochronology of granulites from Vesleknausen,Lützow-Holm Complex,East Antarctica: Neoarchean magmatism and Neoproterozoic high-grade metamorphism |
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| 作者姓名： | Toshiaki Tsunogae Daniel J. Dunkley Kenji Horie Takahiro Endo Tomoharu Miyamoto Mutsumi Kato |
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| 作者单位： | [1]Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan [2]Department of Applied Geology, Western Australian School of Mines, Curtin University, GP0 Box U1987, Perth, WA 6845, Australia [3]Department of Applied Geology, Western Australian School of Mines, Curtin University, CPO Box U1987, Perth, WA 6845, Australia [4]National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan [5]Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan [6]Department of Earth Sciences, Graduate School of Science, Chiba University, Chiba 263-8522, Japan |
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| 摘 要： | We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the L＆#252;tzow-Holm Complex, part of the Gondwana-assembling collisional orogen in East Antarctica. The locality is dominated by felsic to intermediate orthogneiss （charnockite and minor biotite gneiss）, mafic orthogneiss, and hornblende-pyroxene granulite, with deformed and undeformed dykes of metagranite and felsic pegmatite. Pseudosection analysis of charnockite in the system NCKFMASHTO, supported by geothermometry of mafic orthogneiss, was used to infer peak metamorphic temperatures of 750e850 ？C, approximately 150 ？C lower than those estimated for met-asedimentary gneisses from Rundv？gshetta, 6 km to the northeast. SHRIMP U-Pb analysis of zircons from feldspar-pyroxene gneiss, which corresponds to a partially molten patch around mafic orthogneiss, yielded a Concordia upper intercept ages of 2507.9 ？ 7.4 Ma, corresponding to the time of formation of the magmatic protolith to the orthogneiss. Partial melting during peak metamorphism probably took place between 591 and 548 Ma, as recorded in rims overgrew around magmatic zircon. Our results suggest that Rundv？gshetta-Vesleknausen-Strandnibba region in southwestern L＆#252;tzow-Holm Bay, where orthogneisses are dominant, consists of a single crustal block, possibly formed by ca. 2.5 Ga arc mag-matism. The Neoarchean magmatic terrane was tectonically mingled with other fragments （such as metasedimentary units in northern L＆#252;tzow-Holm Bay） by subduction/collision events during the as-sembly of Gondwana supercontinent, and subsequently underwent w850 ？C granulite-facies meta-morphosed during Neoproterozoic to Cambrian final collisional event.
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| 关 键 词： | 锆石SHRIMP 锆石年代学 麻粒岩 岩石学 紫苏花岗岩 地质温度计 岩浆活动 片麻岩 |
| 收稿时间： | 29 January 2013 |
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