西藏中拉萨地块晚侏罗世许如错花岗岩地球化学与岩石成因

发布时间：2018-03-10 20:47

本文选题：地球化学　切入点：锆石U-Pb-Hf　出处：《岩石学报》2017年08期 　论文类型：期刊论文

【摘要】：西藏中部拉萨地块晚侏罗世花岗岩的岩石成因与源区性质目前尚未得到很好约束。本文报道了中部拉萨地块西段许如错岩体的寄主花岗岩和闪长质包体的锆石U-Pb年龄、元素地球化学和锆石Hf同位素成分。许如错岩体寄主花岗岩年龄为155.1±0.7Ma,闪长质包体与寄主花岗岩同期(155.7±0.7Ma)形成。寄主花岗岩属I型偏铝质-弱过铝质高钾钙碱性系列岩石,富集Rb、K等大离子亲石元素和轻稀土元素,亏损Nb、Ta、P、Ti等高场强元素,锆石εHf(t)值(-16.6~-6.6)指示其可能来源于拉萨地块古老下地壳物质的重熔作用。闪长质包体为准铝质钙碱性系列,锆石εHf(t)值(-8.9~-3.8)具有总体为负但明显高于寄主花岗岩εHf(t)值的特征,表明这些闪长质包体代表了幔源物质组成的加入。许如错晚侏罗世花岗岩可能形成于班公湖-怒江特提斯洋洋壳在中晚侏罗世向南俯冲于拉萨地块之下,引起幔源物质与中部拉萨地块古老基底重熔所产生的酸性岩浆发生岩浆混合作用形成的。
[Abstract]:The petrogenesis and source properties of late Jurassic granites in Lhasa block in central Tibet have not been well constrained. This paper reports the zircon U-Pb ages of the host granite and diorite inclusions in the western part of the Lhasa block in central Tibet. Elemental geochemistry and zircon HF isotopic composition. The host granite age of Xuruocao is 155.1 卤0.7 Ma.The diorite inclusions were formed at the same time as the host granite (155.7 卤0.7 Ma.). The host granites belong to type I metaalumina-weakly peraluminous high-potassium calc-alkaline series rocks. Enrichment of large ion lithophile elements and light rare earth elements, depletion of high field strength elements, such as NbTa-Ta-Pu Ti, zircon 蔚 Hfct) indicates that they may have originated from the remelting of the ancient lower crust materials in Lhasa block. The diorite inclusions are quasi-aluminous calc-alkaline series, and they may be derived from the remelting of the ancient lower crustal materials in the Lhasa block. The zircon 蔚 Hft) value is generally negative, but significantly higher than that of the host granite. These diorite inclusions represent the addition of mantle-derived materials. The Xuruso late Jurassic granites may have formed in the Bangong Lake-Nu River Tethys oceanic crust, which subducted south under the Lhasa block in the Middle and late Jurassic. It causes magma mixing of mantle source material and acid magma produced by ancient basement remelting of Lhasa block in the central part of China.
【作者单位】：地质过程与矿产资源国家重点实验室中国地质大学地球科学与资源学院;
【基金】：国家重点研发计划(2016YFC0600304) 国家“973”项目(2015CB452604) 国家自然科学基金项目(41273044、41225006) 中国地质调查局工作项目(1212011121260、1212011121066) 长江学者和创新团队发展计划(IRT1083)联合资助
【分类号】：P534.52;P588.121

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