敦煌地块南部古生代花岗岩地球化学、锆石U-Pb定年及Hf同位素特征研究

发布时间：2018-01-17 00:00

本文关键词：敦煌地块南部古生代花岗岩地球化学、锆石U-Pb定年及Hf同位素特征研究　出处：《岩石学报》2016年12期 　论文类型：期刊论文

【摘要】：敦煌地块出露有大量古生代花岗岩,对这些花岗岩的研究可以更深入的了解敦煌地块的构造演化及其地球动力学意义。本文对敦煌地块南部的安盆沟复式花岗岩体和小草湖花岗岩体进行了岩相学、地球化学、锆石U-Pb年代学和Hf同位素的研究。研究结果表明:(1)安盆沟岩体岩石组合为正长花岗岩-花岗岩,其中正长花岗岩侵位于早古生代(431Ma),花岗岩侵位于泥盆纪(~360Ma)和石炭纪(~340Ma);小草湖岩体主要为似斑状花岗岩,侵位时代为石炭纪(340Ma)。(2)安盆沟早古生代正长花岗岩的ε_(Hf)(t)为-11.7到-6.3,tDM2为1.8~2.2Ga,而晚古生代花岗岩的ε_(Hf)(t)为-12.3到-5.5,tDM2为1.7~2.1Ga,二者Hf同位素特征相似,推测源岩均为古元古代-中元古代时期的含泥质成分的(变)砂质岩。小草湖似斑状花岗岩为加厚下地壳部分熔融成因的埃达克质岩石,ε_(Hf)(t)变化于-16.7至-4.9,tDM2变化于1.8~2.4Ga之间,源岩为古元古代古老地壳物质。两个岩体的部分源岩可能与Columbia超大陆的汇聚和裂解有关。(3)安盆沟正长花岗岩、花岗岩和小草湖似斑状花岗岩的残留相分别为麻粒岩、角闪岩和麻粒岩-角闪榴辉岩,反映了形成深度和变质级别的不同。(4)敦煌地块内的早古生代造山活动结束时间明显晚于中央造山带,并且早古生代造山活动以及早-晚古生代花岗岩与北侧的天山-北山造山带存在时空上的对应关系,敦煌地块可能在古生代期间卷入了中亚造山带的造山活动中。
[Abstract]:A large number of Paleozoic granites emerged from the Dunhuang block. The study of these granites can further understand the tectonic evolution and geodynamic significance of the Dunhuang massif. In this paper, the lithofacies of the Anpenghou complex granitic body and Xiaocaohu granite body in the south of the Dunhuang massif have been carried out. Geochemistry, zircon U-Pb geochronology and HF isotopic studies. The results show that the Anpengou rock assemblage is composed of syenomorphic granitoids and granites. The syenomorphic granite transgressions are located in the early Paleozoic, the granitic intrusions are located in the Devonian and the Carboniferous, and the Carboniferous is 340MaA. The Xiaocaohu pluton is mainly porphyry granitoid, and the emplacement age is the Carboniferous (340MaPU. 2) Anpengou early Paleozoic syenomorphic granite (蔚 ~ + HfCU)) ranging from -11.7 to -6.3. The tDM2 is 1.8 ~ 2.2Ga, while the 蔚 ~ (-1) of the late Paleozoic granite is -12.3 to -5.5 ~ 5.5t DM2 = 1.7 ~ 2.1Ga. Their HF isotopic characteristics are similar. It is inferred that the source rocks are argillaceous (altered) sandstones of Gu Yuan and Mesoproterozoic epoch. The porphyry granite of Xiaocaohu Lake is the adakitic rock formed by the partial melting of the thickened lower crust. The changes of 蔚 HfT) range from -16.7 to -4.9t DM2 between 1.8Ga and 2.4Ga. The source rocks are ancient crustal materials of Gu Yuan. Some of the source rocks of the two bodies may be related to the accumulation and fragmentation of Columbia supercontinent. The residual phases of granite and Xiaocaohu porphyry are granulite, amphibolite and granulite-hornblende eclogite, respectively. The conclusion of early Paleozoic orogenic activity in Dunhuang massif is obviously later than that of central orogenic belt. And the early Paleozoic orogenic activity and the relationship between early and late Paleozoic granites and the northern Tianshan-Beishan orogenic belt. The Dunhuang block may have been involved in orogenic activity of Central Asia orogenic belt during Paleozoic.
【作者单位】：中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室;中国地质科学院地质研究所中国地质调查局大陆动力学研究中心;中国地质大学地球科学学院地质过程与矿产资源国家重点实验室;
【基金】：中国地质调查局项目(121201102000150005-06,12120115027001) 国家自然科学基金项目(41272079)联合资助
【分类号】：P588.121;P597
【正文快照】： 1引言花岗岩是大陆地壳的重要组成部分,花岗岩的形成通常被认为是壳幔相互作用的结果,其中多数是通过地壳岩石的部分熔融而成,仅有少量直接源于演化的地幔岩浆。此外,花岗岩的成因与造山带的形成和演化有着密切的联系,可以通过多种地质过程来实现地壳的水平和垂直增生。因此

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