海南岛印支期麻粒岩的发现及其地质意义:来自锆石U- Pb 定年与微量元素组成的新证据
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本文为中国地质调查局地质调查二级项目(编号DD20189410、DD2019001、DD2019003和DD20190370)联合资助的成果。


Discovery and geological significance of the Indosinian granulites in Hainan Island: new evidence from U- Pb dating and trace element composition of zircons
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    摘要:

    琼中基性麻粒岩是海南岛高级变质杂岩中最重要的组成部分之一,对其深入研究可为客观恢复海南岛晚古生代—早中生代构造演化历史、查明古特提斯洋向东如何延伸等基础地质问题提供新的制约。本次研究以琼中地区出露的基性麻粒岩为研究对象,对基性麻粒岩中锆石采用内部矿物包体自动矿物分析系统(TIMA)扫描、阴极发光图像照相、LA- ICP- MS U- Pb定年与稀土元素分析等综合研究发现,琼中基性麻粒岩中锆石可划分为岩浆锆石和变质锆石两类;30个岩浆锆石测点206Pb/238U年龄介于245~230 Ma之间,相应的加权平均年龄为238±2 Ma(MSWD=0. 38),应代表琼中基性麻粒岩的原岩时代;24个变质锆石测点206Pb/238U年龄介于243~231 Ma之间,其加权平均年龄为237±2 Ma(MSWD=1. 70),代表琼中基性麻粒岩的变质时代。综合海南岛已发表的相关数据,琼中基性麻粒岩原岩形成时代与变质时代均为三叠纪,而不是前人所认为的中元古代,其形成可能与古特提斯洋闭合后印支陆块、华南陆块在碰撞造山后伸展垮塌阶段的岩浆- 变质作用有关。

    Abstract:

    The Qiongzhong mafic granulite is one of the most important components of high- grade metamorphic complex in Hainan Island. A further study of the Qiongzhong mafic granulites will provide new constraints on fundamental geological problems which include the objective restoration of the Late Paleozoic to Early Mesozoic tectonic evolution and potential dynamics of Hainan Island and the determination of the eastward extension of the Paleo- Tethys Ocean. Based on TIMA analyses of mineral inclusions, cathodoluminescence (CL) images, LA- ICP- MS U- Pb dates, and in- situ rare earth element (REE) compositions of zircons in the Qiongzhong mafic granulites, the Triassic zircons can be further divided into two groups (magmatic and metamorphic zircons). Thirty magmatic zircons yielded the consistent 206Pb/238U ages ranging from 245 Ma to 230 Ma, with a corresponding weighted mean age of 238±2 Ma (MSWD=0. 38), which is interpreted as the protolithic timing of the Qiongzhong mafic granulites. Twenty- four metamorphic zircons also yielded consistent 206Pb/238U ages ranging from 243 Ma to 231 Ma, with a corresponding weighted mean age of 237±2 Ma (MSWD=1. 70), which is the metamorphic timing of the Qiongzhong mafic granulites. Combined with the published and related data in Hainan Island, the Qiongzhong mafic granulites were generated in Triassic, not Mesoproterozoic, and may have been formed in a post- collisional extensional setting during the collision orogenesis between South China and the Indochina Blocks after the closure of the Paleo- Tethys Ocean.

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高维,施建荣,孟庆奎,舒晴,张凯淞,王晨阳,徐光晶.2022.海南岛印支期麻粒岩的发现及其地质意义:来自锆石U- Pb 定年与微量元素组成的新证据[J].地质学报,96(2):426-444.
Gao Wei, Shi Jianrong, Meng Qingkui, Shu Qing, Zhang Kaisong, Wang Chenyang, Xu Guangjing.2022. Discovery and geological significance of the Indosinian granulites in Hainan Island: new evidence from U- Pb dating and trace element composition of zircons[J]. Acta Geologica Sinica,96(2):426-444.

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  • 收稿日期:2021-08-03
  • 最后修改日期:2021-09-30
  • 录用日期:2021-09-30
  • 在线发布日期: 2022-03-02
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