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    青海祁漫塔格卡尔却卡铜多金属矿区花岗闪长岩锆石SHRIMP U-Pb测年及其地质意义

    Zircon SHRIMP U-Pb dating of granodiorite in the Kaerqueka polymetallic ore deposit, Qimantage Mountain, Qinghai Province, and its geological implications

    • 摘要: 提要:笔者在对青海祁漫塔格地区卡尔却卡铜多金属矿床进行典型解剖基础之上,开展了矿区内与矽卡岩型铁铜铅锌多金属矿化具有密切成因联系的花岗闪长岩的岩石地球化学和锆石SHRIMP U-Pb精细定年研究。结果表明:花岗闪长岩为高钾钙碱性系列,轻稀土富集,轻重稀土分异明显,具弱的负铕异常(δEu=0.61~0.91);微量元素以富集大离子亲石元素Rb、K、Th,亏损Nb、Sr、Ti为特征;获得15个锆石数据点的206Pb/238U年龄为(237±2) Ma(MSWD=0.8),表明岩体形成于中三叠世,属印支期岩浆活动的产物。结合年代学、岩石地球化学和区域地质构造演化特征,笔者认为本区花岗闪长岩形成的构造环境为后碰撞演化阶段。

       

      Abstract: Abstract:Based on a detailed analysis of the Kaerqueka polymetallic ore deposit in Qimantage area of Qinghai Province, the authors consider that the granodiorite is closely related to the Fe-Cu-Pb-Zn skarn polymetallic mineralization. A petrological-geochemical study and SHRIMP zircon U-Pb dating of the granodiorite show that the granodiorite is composed of intermediate-acid rocks of the high-potash calc-alkaline series. The rocks are characterized by obvious fractionation of REE, enrichment of LREE, δEu values of 0.61~0.91 that indicate a weak negative Eu anomaly, high LILE (such as Rb, Th, K ) and depletion of Nb, Sr, Ti. 15 data points from SHRIMP zircon U-Pb dating show that the age is (237±2)Ma (MSWD=0.8), suggesting that the granodiorite was formed in Middle Triassic. Based on a combined study of geochronology, petrological geochemistry and evolutionary characteristics of regional structures, the authors hold that the granodiorite was formed at the post-collisional development stage in the continental orogen.

       

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