西藏邦铺斑岩矿床黑云二长花岗岩的形成时代及地球化学特征

发布时间：2018-12-13 21:15

【摘要】：邦铺是继驱龙、甲马之后在冈底斯斑岩铜矿带发现的又一大型斑岩型矿床。为探索邦铺矿区岩浆的起源、建立岩浆演化序列提供依据,本文对位于矿区西南侧的黑云二长花岗岩进行了主、微量元素,锆石U-Pb年代学,Sr-Nd-Pb-Hf同位素分析。结果显示,邦铺黑云二长花岗岩的SiO_2平均含量为73.52%,属钙碱性系列、弱过铝质花岗岩;其轻重稀土分异较明显,负Eu异常强烈,富集K、Rb、Th等大离子亲石元素,相对亏损P、Nb、Ta、Ti等高场强元素;锆石U-Pb年龄为(62.2±0.32)Ma,~(176)Hf/~(177)Hf值分布于0.282892~0.283014,εHf(t)均值为7.3。研究表明,邦铺黑云二长花岗岩起源于俯冲的特提斯洋壳板片脱水引起的地幔楔的部分熔融,地幔组分约占80%,岩浆在上升过程中,有较多地壳物质的加入,并经过了强烈的结晶分异作用。
[Abstract]:Bangpu is another large porphyry deposit discovered in the Gangdis porphyry copper belt after the drive of dragon and Jia Ma. In order to explore the origin of magma and provide basis for magmatic evolution sequence, the main, trace element, zircon U-Pb chronology and Sr-Nd-Pb-Hf isotopic analysis of the bifeldite located in the southwest of the mining area have been carried out in this paper. The results show that the average SiO_2 content of the Bangpu bifeldite is 73.52, which belongs to calc-alkaline series and weakly peraluminous granite. The heavy and heavy rare earth elements are distinct, and the negative Eu is strong, which enriches the large ion lithophile elements such as K ~ (2 +) Rb ~ (2 +) Th, and is relatively depleted in the high field strength elements such as Pnb ~ (2 +) ~ (2 +) Ta-Ti. The U-Pb age of zircon is (62.2 卤0.32) Ma,~ (176) Hf/~ (177) Hf and the mean 蔚 Hf (t) is 7.3. The results show that the Bangpu bifeldite originated from the partial melting of mantle wedge caused by dehydration of subducted Tethys oceanic crust plate, and the composition of mantle is about 80%. During the process of magma rising, more crustal materials are added. And after a strong crystallization differentiation.
【作者单位】：中国地质科学院矿产资源研究所;北京矿产地质研究院;青海省地质调查院;
【基金】：国家重点研发计划课题(2016YFC0600307) 中国地质科学院基本科研业务费项目(K1709)
【分类号】：P588.121;P618.41

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