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滇西南团梁子岩组分异石英脉锆石U-Pb年龄——晚三叠世澜沧江构造带区域变质变形的时代制约 预览

Zircon U-Pb ages of quartz vein rocks in Tuanliangzi Formation complex of southwestern Yunnan Province: Regional metamorphism deformation age restriction of Late Triassic Lancang River tectonic belt
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摘要 在滇西南澜沧江构造带东侧、扬子板块西缘中元古代团梁子岩组含有大量的平行于区域面理(S2)的构造热液石英脉,利用LA-ICP-MS对3件石英脉和1件绿片岩中的锆石进行206U/238Pb测年,获得3组明显的组合年龄:395~461Ma、240~260Ma和222~228Ma,大部分集中于222~228Ma。对比研究表明,区域上2期变质变形(M1D1、M2D2)与获得的锆石年龄有较好的对应性,早期的变质变形(M1D1)形成于早古生代(395~461Ma)原特提斯洋盆向东俯冲阶段;晚期的2期变质变形(M2aD2a,M2bD2b)发生于晚古生代—中生代早期(240~260Ma)古特提斯洋盆向东俯冲阶段和晚三叠世早期(222~228Ma)古特提斯洋盆闭合阶段。晚三叠世早期变质变形(M2bD2b)构造热液发生在临沧花岗岩侵位和弧陆碰撞型忙怀组火山岩(229~235Ma)之后,早于小定西组/芒汇河组拉伸期火山岩(210~222Ma),是古特提斯洋与扬子陆块碰撞后的应力松弛阶段俯冲岩片快速折返的证据,同时也反映了古特提斯洋盆在晚三叠世早期之前已经关闭。 Abundant tectonic hydrothermal quartz veins were found, which are parallel to the regional foliation (S2) in Mesoproterozoic Tuanliangzi Formation in southwest Yunnan, and those ancient mixtites of Tuanliangzi Formation are important tectonic rocks in southern Lancang River tectonic belt and along the west Yangtze block. Three zircon samples of quartz dykes and one zircon sample of green dyke were selected and analyzed using laser ablation inductively coupled plasma mass spectrometry (LAICP-MS). The 206Pb/238U ages can be divided into three groups, i.e., 395~461Ma, 240~260Ma and 222~228Ma, with most of them concentrated on 222~228Ma. The quartz dykes ages indicate two stages of regional metamorphism deformation (M1D1, M2D2): the first stage of metamorphism deformation(M1D1)was the result of pro-Tethys eastward subduction in Early Paleozoic(395~461Ma); the second stage of metamorphism deformation(M2D2)occurred in late Paleozoic-Mesozoic which could be divided into two periods of metamorphism deformation(M2aD2a, M2bD2b): the early period was Late Paleozoic to Early Mesozoic (240~260Ma) when the Paleo-Tethys experienced eastward subduction, whereas the late period of metamorphism deformation was caused by the closure of Paleo-Tethys Ocean basin in early Late Triassic (222~228Ma). The quartz dykes in Tuanliangzi Formation were impacted by tectonic hydrothermal event in the early Late Triassic,and were formed later than Lincang granite and the volcanic rocks of Manghuan Formation(229~235Ma), but earlier than stretch volcanic rocks of Xiaodingxi Formation and Manghuihe Formation (210~222Ma), which indicates that these syn-emplacement quartz dykes were the results of rapid exhumation that happened later than the Paleotethys ocean eastward collision with Yangtze block; in addition, the ancient Tethys Ocean had been closed earlier than early Late Triassic, suggesting minimum age limitation of quartz dykes in Tuanliangzi Formation.
作者 刘桂春 孙载波 冯庆来 陈光艳 刘军平 俞赛赢 田素梅 LIU Guichun;SUN Zaibo;FENG Qinglai;CHEN Guangyan;LIU Junping;YU Saiying;TIAN Sumei(Yunnan Institute of Geological Survey, Kunming 650216 , Yunnan, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, Hubei, China)
出处 《地质通报》 CAS CSCD 北大核心 2019年第1期14-21,共8页 Geologcal Bulletin OF China
基金 国家自然科学基金项目《安徽栏杆含金刚石母岩及金刚石矿床指示矿物特征研究》(批准号:41402075) 《滇西南原特提斯及其与古特提斯演化关系研究》(批准号:41672222) 中国地质调查局项目《云南区域地质调查片区总结与服务产品开发》(编号:DD20160345-02) 云南省科技领军人才培养计划项目《西南“三江”叠合成矿作用与成矿预测》(编号:2013HA001).
关键词 锆石U-PB年龄 分异石英脉岩 团梁子岩组 变质变形 南澜沧江构造带 zircon U- Pb age quartz dyke structure differentiation Tuanliangzi Formation complex regional metamorphism deformation South Lancang River tectonic belt
作者简介 刘桂春(1982-),男,硕士,高级工程师,从事区域地质调查工作和造山带地质学研究。E-mail:liuguichun15@sina.com;通讯作者:冯庆来(1961-),男,教授,博士生导师,从事地层古生物学和造山带地质学研究。E-mail: qinglaifeng@cug.edu.cn
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