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岩石学报 2009
LA-ICP-MS zircon U-Pb dating of the Huangyangshan pluton and its enclaves from Kalamaili area eastern Junggar,Xinjiang, and geological implications
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Abstract:
High-precision LA-ICP-MS zircon U-Pb dating has revealed that the Huangyangshan pluton in eastern Junggar, northern Xinjiang,was formed at 311 ± 12Ma, which represents the age of lithogenesis of the Huangyangshan magma mixing pluton, and that microgranular enclaves in the alkaline granite were formed at 300 ± 6Ma. It' s the first time obtain the microgranular enclaves age in Huangyangshan pluton, which represents the age of the enclaves formed, both ages are very consistent within errors, the time belongs to Late Carboniferous, implying the host rock and its enclaves were formed at the same time, that is the product of post-collisional magma activity around the Junggar area in 300Ma approximately. Petrochemistry and geochemistry researching suggested host rock characteristics of high silicon and enrich alkali,low magnesium, calcium and aluminous, and high differentiation, ingredient of the host rock, microgranular enclaves and diabase dykes project on hne of the magma mixing. Host rock enrichment of LILE (such as Rb and Th) and HFSE (such as Zr and Hf), depleted of Ba,Sr,Ta and Ti, have lowest δEu (0.01), low initial ~(87)Sr/~(86)Sr ratios and high positive ε_(Nd) (t) values. Huangyangshan magma mixing pluton formed in expansion tectonics setting of post-collisional stage, mantal magma take place underplating, because the underplating of the mantal magma, low crust melt by the high temperature forming the acid crust-magma,part of the mantal magma up to crust along the deep fault belt, the basic magma from mantle and acid one from crust mixing,formed the Huangyangshan magma mixing pluton. The diorite microgranular enclaves are the recorder of the crust and mantal magma mixing process,the diabase dykes in research area is the product from direct differentiation and evolution of the mantal magma.
