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李宝龙,王丹丹,张建,毛景文,马波. 2018. 海南岛西部戈枕含金剪切带花岗质糜棱岩中锆石SHRIMP U-Pb年代学及其地质意义. 岩石学报, 34(9): 2687-2702
海南岛西部戈枕含金剪切带花岗质糜棱岩中锆石SHRIMP U-Pb年代学及其地质意义
作者单位
李宝龙 自然资源部成矿作用与资源评价重点实验室, 中国地质科学院矿产资源研究所, 北京 100037 
王丹丹 中国地质调查局油气资源调查中心, 北京 100083 
张建 海南省国土资源厅, 海口 570203 
毛景文 自然资源部成矿作用与资源评价重点实验室, 中国地质科学院矿产资源研究所, 北京 100037 
马波 海南省地质调查院, 海口 570206 
基金项目:本文受中央级公益性科研院所基本科研业务专项(K1309)、国家自然科学重点基金项目(41430314)和中国地质调查局地质调查项目(12120114034301、DD2016026)联合资助.
摘要:
      海南岛西部的中元古代抱板群混合岩主要沿北东向戈枕剪切带展布,近年来的研究逐渐揭示混合岩的原岩为花岗质岩石,是遭受强烈剪切作用改造的糜棱岩。本文选择土外山金矿的花岗质糜棱岩和不磨金矿的糜棱岩化花岗岩进行锆石SHRIMP U-Pb年代学测试,3件样品的锆石SHRIMP U-Pb谐和线年龄值分别为1439.1±8.4Ma(样品13JC-8-1,MSWD=0.85,n=14)、1436.9±8.3Ma(样品13JC-41,MSWD=0.54,n=10)和1448±13Ma(样品BM-3,MSWD=0.56,n=10),代表其原岩的侵位时代。结合研究区已有的研究成果,本文认为海南岛西部花岗质岩类和沿戈枕剪切带出露的糜棱岩原岩结晶年龄为~1450Ma,之后于~1400Ma经历一期构造-热变质事件;海南岛应为华夏地块的一部分,在Rodinia超大陆聚合前,华夏地块(包括海南岛,至少包括海南岛北西部)最有可能位于劳伦大陆南缘的西南延伸部分,华夏地块(包括海南岛)所经历的格林威尔造山事件可能较扬子板块偏早。
英文摘要:
      Hainan Island, located off the southern coast of South China, is separated from the South China mainland by the Qiongzhou Strait. Tectonically, the island is located at the intersection of the Eurasian, India-Australian and Pacific plates. It is generally considered part of the Cathaysia Block, but some researchers propose that it has an affinity to the Indochina Block. The Precambrian granitoid plutons emplaced in the Paleoproterozoic-Mesoproterozoic Baoban Group in Gezhen area and the Mesoproterozoic migmatites distributed along the Gezhen shear zone in western Hainan Island, are subjected to strongly shearing mylonites by recent studies, and their original rocks are granitic rocks. In this study, the mylonitic granites of the Bumo gold deposit in the Gezhen shear zone and granitic mylonites of the Tuwaishan gold deposit in the northern segment of the Gezhen shear zone were dated by SHRIMP U-Pb analysis together with CL imaging of their zircons, respectively. Zircons from three deformed granitic rocks yield concordant SHRIMP U-Pb ages of 1439.1±8.4Ma (Sample 13JC-8-1, MSWD=0.85, n=14)、1436.9±8.3Ma (Sample 13JC-41, MSWD=0.54, n=10) and 1448±13Ma (Sample BM-3, MSWD=0.56, n=10), indicating the original granitic rocks of this mylonite emplacement at~1450Ma. In connection with the zircon internal structures, the structural deformation and CL images, as well as the previously published age data by different dating methods in this area, we suggest that a tectono-thermal metamorphic event most likely took place at~1400Ma, and thus the crystallization age for granitic original rocks of mylonites in the study area should be at~1450Ma. The Hainan Island should be part of the Cathaysia Block (including Hainan Island, at least its northwestern part) which could be regarded as a southwestward extension of southern Laurentia before the assembly of the Mesoproterozoic-Neoproterozoic Rodinia supercontinent. These results also imply that the Cathaysian Block (including Hainan Island) probably underwent an earlier Grenville orogeny event, in comparison with Yangtze Block.
关键词:花岗质糜棱岩  锆石SHRIMP U-Pb年龄  戈枕剪切带  海南岛西部  劳伦大陆
投稿时间:2017-08-30  修订日期:2018-06-02
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