| 中甸弧阿热岩体锆石U-Pb年龄、地球化学特征及岩石成因 |
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| 引用本文： | 周放,王保弟,刘函,闫国川,李小波.中甸弧阿热岩体锆石U-Pb年龄、地球化学特征及岩石成因[J].地球科学,2018,43(8):2614-2627. |
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| 作者姓名： | 周放 王保弟 刘函 闫国川 李小波 |
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| 作者单位： | 1.中国地质科学院矿产资源研究所, 北京 100037 |
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| 基金项目： | 国家自然科学基金项目41603038国家自然科学基金项目41773026国家重点研发计划项目2016YFC0600305中国地质调查局项目DD20160016 |
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| 摘 要： | 中甸弧是中国西南"三江"特提斯构造带南段最重要的成矿区之一.前人的研究重点一直放在该带中北部含矿岩体中，对南部不含矿岩体却了解甚少.对南部阿热岩体进行了岩石学、主量和微量元素地球化学及锆石U-Pb年代学等研究，结果表明阿热岩体（216.3±1.8 Ma）与该地区其他岩体形成时代相同.岩石地球化学研究显示阿热石英二长岩具有高Sr（1 563×10-6~2 051×10-6）、低Y（15.0×10-6~22.4×10-6）含量及高Sr/Y值（86.0~120.5），富集大离子亲石元素（Rb、Ba、Th、U），亏损高场强元素（Nb、Ta、Ti），并具有轻微负Eu异常等特征，表明岛弧火成岩和埃达克质岩亲和性.同时，阿热岩体中MgO含量（1.97%~3.30%）和Mg#值（38.7~50.8，平均为43.03）较低，Ni（10.7×10-6~26.8×10-6）、Cr（18.0×10-6~75.8×10-6）、Co（12.4×10-6~17.4×10-6）等相容元素含量也较低，地球化学性质指示其可能由地壳部分熔融形成.晚三叠世甘孜-理塘俯冲洋壳由于温度和压力的改变发生脱水，释放的流体或熔体上升至下地壳，致使下地壳发生部分熔融，从而产生了阿热地区的这些花岗质岩浆.因此，晚三叠世阿热岩体形成于陆缘弧构造背景，是甘孜-理塘洋西向俯冲消减的产物，而此时很可能发生了大洋向残留海转化的过程.
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| 关 键 词： | 中甸弧 阿热岩体 埃达克质岩 陆缘弧 甘孜-理塘洋 地球化学 地质年代学 |
| 收稿时间： | 2018-05-30 |
Zircon U-Pb Dating,Geochemistry and Petrogenesis of Intrusive Rocks from A're Area,Zhongdian Arc |
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| Abstract: | Zhongdian arc, located in Sanjiang Tethyan Orogenic belt in Southwest China southern part of Tethys belt, is one of the most important districts for polymetallic ore deposits.Previous studies mainly focus on the ore-bearing intrusions in the central and northern part of Zhongdian arc, however, there are still limited knowledge about the barren intrusions in the southern part.In this paper, we present detailed petrology, major and trace elemental geochemistry and geochronology of A're granitoids, southern part of Zhongdian arc.Zircon U-Pb dating results show the timing of emplacement of A're intrusion (216.3±1.8 Ma) is comparable to those of the other intrusive rocks in Zhongdian arc.A're quartz monzonites have high Sr (mean 1810.24×10-6), low Y (mean 19.05×10-6) concentrations and thus high Sr/Y(86.0-120.5) ratios.In addition, they also display enrichment in LILE (Rb, Ba, Th, U), depletion in HFSE (Nb, Ta, Ti) and slightly Eu negative anomaly, which suggests that they have geochemical characteristics of both arc-related and adakitic affinities.The low MgO (1.97%-3.30%), Ni (10.7×10-6-26.8×10-6), Cr (18.0×10-6-75.8×10-6) and Co (12.4×10-6-17.4×10-6) contents of the A're granitoids support that they were, generated from partial melting of thicken lower crust.Therefore, the A're quartz monzonites belong to a part of the continental marginal arc during westward subduction of Ganzi-Litang ocean, which represents the products of transformation from widespread Tethys ocean to residual sea in Zhongdian arc. |
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