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Early Paleozoic Magmatism in West Kunlun: Constraints from Geochemical and Zircon U-Pb-Hf Isotopic Studies of the Bulong Granite
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摘要


     This study reports geochemistry, zircon U-Pb and Hf-isotopic data for the monzogranite from the Bulong pluton, west Kunlun. The monzogranites are high-K calc-alkaline to shoshonitic series,with A/CNK values of 1.1. Their low Rb/Sr0.67 0. 88 and Sr/Y ratios 13.2 16.6, weakly negative Eu anomaly Eu/Eu = 0. 68 0.84, and moderate Sr, Rb contents Sr = 214 × 10-6 247 × 10-6, Rb = 165 × 10-6 191× 10-6 indicate dehydration melting of biotiteand amphibole in the source region. LA-ICP-MS U-Pb zircon dating of the Bulong monzogranite yielded age of 441 2 Ma MSWD = 0.33 with 8s~t values between -5.1 and -2.3 average value of -0.3 . The inferred protolith is an intermediate crustal igneous rock formed during the period of Mesoproterozoic-Neoproterozoic. Combined with the previous studies,it is suggest that the Early Paleozoic granites distrubuted at both sides of the Kudi ophiolitic melange and almost simultaneous with the Kudi ophiolitic melange. Early Paleozoic granites from the west Kunlun display multi-episodes with forming ages of 507 500 Ma, 471 468 Ma, 447 430 Ma and 408 404 Ma,which is probably the result of northward subduetion of the Paleo-Tethys ocean.

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