阿尔金喀腊大湾地区中酸性火山岩SHRIMP年龄及其构造环境
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本文为“十一.五”、“十二.五”国家科技支撑计划重点项目(编号:2006BAB07B02-04、2011BAB06B08-04)和地质矿产调查专项(编号:1212011085043)的资助成果。


Zircon SHRIMP U Pb Dating of Intermediate Felsic Volcanic Rocks from the Kaladawan Area, Altun Mountains and Its Tectonic Environment
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    摘要:

    阿尔金山喀腊大湾地区位于北东向阿尔金走滑断裂北侧与东西向阿尔金北缘断裂所夹持的区域,是区域上红柳沟-拉配泉构造带的中段。该区广泛发育火山-沉积岩系,前人将其确定为中元古代。本文运用锆石SHRIMP U Pb方法对区内火山-沉积岩系中的中酸性火山岩进行测年,获得477~485Ma的年龄,确认喀腊大湾地区早古生代中酸性岩浆喷发活动的存在。同时根据岩石地球化学研究,显示这套火山岩具有活动大陆边缘(岛弧)构造环境,其岩浆源具有I型及I与S过渡类型特点。结合前人对红柳沟-拉配泉一带的蛇绿混杂岩、高压变质泥岩、榴辉岩、中酸性侵入岩等相关年代资料及构造环境示踪,作者认为喀腊大湾地区中酸性火山岩形成于活动大陆边缘(岛弧)大地构造环境,其时限与蛇绿混杂岩的末期非常接近,代表了洋壳俯冲碰撞过程中形成的同碰撞中酸性火山岩。据此可以将区域上红柳沟-拉配泉一带的构造演化划分为洋壳扩张期(晚元古代末-寒武纪,蛇绿混杂岩年龄510~580Ma,但扩张起始会早一些)、洋壳板块俯冲碰撞期(早奥陶世-中奥陶世早期,中酸性岩浆岩(包括侵入岩和火山岩)年龄为477~488 Ma (部分花岗岩年龄延迟到467Ma左右),以及高压变质岩的退变质年龄479~491Ma),碰撞后伸展期(晚奥陶世—志留纪,蛇绿混杂岩变质基质岩系的变质年龄450~455Ma,代表蛇绿混杂岩最后就位,碰撞—碰撞后S型碱性花岗岩年龄417~431Ma,代表碰撞后伸展构造环境)三个演化阶段。

    Abstract:

    The Kaladawan area of Altun Mountains is located in the central segment of the Hongliugou Lapeiquan structural belt, which is bounded by the NE striking Altun strike slip faults to the north and the E W trending northern Altun fault. The area is widely developed with volcanic sedimentary rocks, which were determined to be Mesoproterozoic in age by previous studies. In this study zircon SHRIMP U Pb dating for the intermediate felsic volcanic rocks from the volcanic sedimentary rocks was conducted and yielded an age of 477~485 Ma, which confirms the existence of intermediate and felsic magmatic activity in the Kaladawan area during early Paleozoic. Petrogeochemical study also indicates that the volcanic rocks reflect the tectonic setting of active continental margin (Island arc) and magma source is characteristic of I type and I S transition type. In combination with dating and tectonic setting tracing of the ophiolitic mélange, high pressure metamorphic mudstone, eclogite, intermediate felsic intrusive rocks in the Hongliugou Lapeiquan structural belt, the authors suggest that the intermediate felsic volcanic rocks in the Kaladawan area are related to a tectonic setting of active continental margin (Island arc) and the age is roughly consistent with the final phase of ophiolitic mélange, representing that the syn collision intermediate felsic volcanic rocks resulting from the subduction of oceanic crust process. The Hongliugou Lapeiquan structural belt can be divided into 3 evolutional stages: ①a period of oceanic crust expansion in the Late Proterozoic Cambrian (the age of ophiolitic mélange is 510~580Ma and the expansion was slightly earlier); ②a period of subduction collision of oceanic crust plates in Early Ordovician Middle Ordovician early (the age of intermediate acidic volcanic rocks (including intrusive rock and volcanic rock) is 477~488Ma, part of granite has an age of 467Ma and high pressure metamorphic rocks of regressive metamorphism age is 479~491Ma); ③a period of post collision to extension in Late Ordovician Silurian (the ophiolitic mélange metamorphic basement is 450~455Ma in age, which represent final emplacement of ophiolitic mélange, and collision and post collision S type granite has the age of 417~431Ma, which shows the post collision to extension settings).

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陈柏林,李松彬,蒋荣宝,陈正乐,韩凤彬,崔玲玲,李丽,赵树铭,祁万修,杨屹,王世新,王永,周永贵,郝瑞祥.2016.阿尔金喀腊大湾地区中酸性火山岩SHRIMP年龄及其构造环境[J].地质学报,90(4):708-727.
CHEN Bolin, LI Songbin, JIANG Rongbao, CHEN Zhengle, HAN Fengbin, CUI Lingling, LI Li, ZHAO Shuming, QI Wanxiu, YANG Yi, WANG Shixin, WANG Yong, ZHOU Yonggui, ZHOU Yonggui.2016. Zircon SHRIMP U Pb Dating of Intermediate Felsic Volcanic Rocks from the Kaladawan Area, Altun Mountains and Its Tectonic Environment[J]. Acta Geologica Sinica,90(4):708-727.

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  • 收稿日期:2015-02-07
  • 最后修改日期:2015-04-03
  • 录用日期:2016-04-26
  • 在线发布日期: 2016-04-26
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