| 新疆古伦沟地区古仍格萨拉东岩体的地球化学及锆石U-Pb年龄 |
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| 关键词:granodiorite-porphyry zircon LA-ICP-MS U-Pb dating Early Ordovician epicontinental arc northern margin of Middle Tianshan Mountains |
| 基金项目:国家科技支撑计划项目(编号: 2011BAB06B01-03; 2006BAB07B04-05) |
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| Geochemistry and Zircon U-Pb Age of East Gurenggesala Granitic Intrusion in Gulungou Area, Xinjiang |
| The East Gurenggesala granitic intrusion in Gulungou area on the northern margin of Middle Tianshan Mountains consist of granodiorite-porphyry with porphyry copper mineralization. The intrusion is characterized by enrichment of alkali, with Na2O/K2O ratio changing from 1.95 to 19.00, and depletion of Fe and Mg, accompanied by sub-alkaline (mainly tholeiitic and calc-alkaline series) and weakly peraluminous features (A/CNK=0.98~1.11). REE concentrations are low (∑REE=61.28×10-6~99.50×10-6) and show obvious differentiation between LREE and HREE (LaN/YbN=7.82~22.80), with weak Eu negative anomalies (δEu=0.72~0.97). In addition, the rock mass is relatively rich in such elements as Rb, Ba, Th, U and K, and poor in Nb, Ta, P, Ti etc., suggesting characteristics of volcanic-arc granite (VAG). Zircon LA-ICP-MS U-Pb dating results show that the crystallization of the intrusion took place from (488.9±1.7) Ma to (470.5±3.1) Ma, i.e., in Early Ordovician. Sr-Nd isotopic compositions of East Gurenggesala granitic intrusion are fairly uniform: (87Sr/86Sr)i=0.70677~0.70685, εSr(t)=40.10~41.21, (143Nd/144Nd)i=0.51190~0.51191, εNd(t)=–2.62 ~ –2.30, tDM=1.31~1.38 Ga, implying that magma originated from partial melting of Meso-Proterozoic mantle-derived basic lower crust. Based on both previous and present research results, the authors have reached the conslusion that East Gurenggesala granitic intrusion was formed in the epicontinental arc relevant to the subduction of the paleo-Junggar ocean towards Yili-Central Tianshan plate in Early Ordovician together with porphyry copper mineralization. In general, the emplacement of East Gurenggesala granitic intrusion marked the epoch when the northern margin of Middle Tianshan entered into the stage of active epicontinental arc in connection with subduction in Early Ordovician. |
| WANG Ju-li,YANG Meng,WANG Jian-qi,DANG Fei-peng.2013.Geochemistry and Zircon U-Pb Age of East Gurenggesala Granitic Intrusion in Gulungou Area, Xinjiang[J].Acta Geoscientica Sinica,34(6):680-690. |
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