| 班—怒成矿带西段江玛南铜银矿区石英闪长玢岩锆石U-Pb年龄、Hf同位素及地球化学特征 |
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| 引用本文：高腾,王立强,王勇,郑斯伦,胡宇.2019.班—怒成矿带西段江玛南铜银矿区石英闪长玢岩锆石U-Pb年龄、Hf同位素及地球化学特征[J].地球学报,40(6):884-894. |
| DOI：10.3975/cagsb.2019.042201 |
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| 基金项目:中国地质科学院基本科研业务费专项(编号: JYYWF20182402);国家重点研发计划“深地资源勘查开采”重点专项(编号: 2018YFC0604106);国家自然基金项目(编号: 41873046);中国地质调查局地质调查项目(编号: DD20160026) |
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| 中文摘要:西藏革吉县江玛—赛登地区是班公湖—怒江成矿带内近两年发现的成矿潜力较好的地区之一。本文对江玛南铜银矿点的石英闪长玢岩进行锆石U-Pb年代学、全岩地球化学和锆石Hf同位素组成研究。利用LA-ICP-MS测得206Pb/238U年龄为(118.6±2.8) Ma (N=13, MSWD=3.8), 此年龄可解释为石英闪长玢岩成岩年龄。全岩主量和微量元素分析显示, 石英闪长玢岩属于中钾钙碱性准铝质I型花岗岩。岩石轻、重稀土元素分馏明显(LREE/HREE =9.37~9.76), 富集轻稀土元素; δEu值为0.94～0.9, Eu负异常不甚明显。岩石相对富集Rb、Th、U、K等大离子亲石元素(LILE), 亏损Nb、Ta、Zr、Ti等高场强元素(HFSE), 具有岛弧岩浆岩的岩石化学属性。锆石Hf同位素分析结果显示, 锆石εHf(t)值为+7.9 ~ +11.2, 平均值为+9.5, 两阶段模式年龄TDMC=456~675 Ma, 表现出明显的幔源成岩物质来源特征。通过年代学、岩石地球化学、Hf同位素及区域综合对比研究, 认为江玛南石英闪长玢岩的形成与班公湖—怒江特提斯洋南向俯冲有关。 |
| 中文关键词:石英闪长玢岩 LA-ICP-MS 锆石U-Pb定年 锆石Hf同位素 全岩地球化学 班公湖—怒江成矿带 |
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| Zircon U-Pb Age, Hf Isotope and Geochemistry of Quartz Diorite Porphyry of the Jiangmanan Copper-silver Ore District in the Western Part of the Bangong Co–Nujiang Metallogenic Belt |
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| Abstract:The Jiangma–Saideng ore district with a large potential of copper polymetallic resources was discovered recently in the Bangong Co–Nujiang metallogenic belt. Zircon U-Pb geochronology, whole-rock geochemistry and Zircon Hf isotope composition of the quartz diorite porphyry in Jiangmanan were studied in this paper. LA-ICP-MS zircon 206Pb/238U dating result indicates that the quartz diorite porphyry was emplaced at (118.6±2.8) Ma (N=13, MSWD = 3.6). Whole-rock major and trace element data show that the quartz diorite porphyry belongs to medium-K calc-alkaline and metaluminous I-type felsic rocks. The quartz diorite porphyry is obviously enriched in LREE and displays weak or no Eu anomalies (REE/HREE = 9.37~9.76, LaN/YbN = 12.33~12.98, δEu = 0.94~0.97). The rock is also enriched in large-ion lithophile elements (LILE such as Rb, Th, U, and K) and relatively depleted in high field strength elements (HFSE such as Ta, Nb, Ti and Zr), having geochemical features of arc-type magmas. The positive εHf(t) values of zircons are +7.9 ~ +11.2, and the second stage Hf mode ages TDMC are 456~675 Ma, which indicates its mantle source. Based on geochronology, geochemistry, zircon Hf isotope and regional study, the authors hold that the quartz diorite porphyry resulted from southward subduction of Bangong Co–Nujiang Tethys Ocean. |
| keywords:quartz diorite porphyry LA-ICP-MS zircon U-Pb dating zircon Hf isotope whole-rock geochemistry Bangong Co–Nujiang metallogenic belt |
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