| 湖南骑田岭花岗岩及其暗色微粒包体的地球化学与壳幔岩浆的混合作用 |
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| 关键词:dark microgranular enclave host rock geochemistry magmatic mixing extensional settings |
| 基金项目:中国地质调查局项目(编号:200313000041、200113900018) |
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| Geochemistry and Crust-Mantle Magmatic Mixing of the Qitianling Granites and Their Dark Microgranular Enclaves in Hunan Province |
| The Qitianling pluton is one of the typical granites with the contribution of mantle-derived components in the Nanling region, southern China. The amphibole biotite monzogranite and (amphibole) biotite syenogranite, which commonly contain abundant dark microgranular enclaves and dark mineral bands or nodules, have formed the main body of the pluton. The dark microgranular enclaves have most typical macro- and micro-textures of magma mixing such as ovoid and plastic deformation shape, chilled margin, bimodal plagioclase, rapakivi-like feldspar and apatite needles. The enclaves belong to metaluminous (A/KNC=0.72～1.00, 0.85 on average) shoshonitic rock, and the host rocks show metaluminous to weakly peraluminous attribute(A/KNC=0.89～1.06, 0.97 on average). Between them, main and trace elements display the magmatic mixing evolution trend. They also display close Sr, Nd isotopic compositions with I- Sr and ε- Nd(t) values of 0.71041～0.71263, -6.9～-5.3 for the enclaves and 0.70854～0.71416, -9.2～-5.1 for the host rocks, which are all indicative of mixing of crustal materials with mantle components. The formation age(152 Ma)of the enclave is close to that(155～161 Ma) of the host rock, suggesting that the mixing event took place during the early period of Late Jurassic. According to a comprehensive analysis of their tectonic settings as well as geological and geochemical data, it is suggested that the dark microgranular enclaves in the Qitianling pluton were generated by mixing of mantle-derived basic magma and its induced crustal felsic magma in an extension environment. |
| FU Jian-ming,XIE Cai-fu,PENG Bai-song,YANG Xiao-jun,MEI Yu-ping.2006.Geochemistry and Crust-Mantle Magmatic Mixing of the Qitianling Granites and Their Dark Microgranular Enclaves in Hunan Province[J].Acta Geoscientica Sinica,27(6):557-569. |
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