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滇中地区昆阳群物源及构造环境
引用本文:纪星星,周诗,陈棋,刘德民,李德威.滇中地区昆阳群物源及构造环境[J].中国地质,2016(3):857-878.
作者姓名:纪星星  周诗  陈棋  刘德民  李德威
作者单位:贵州省工程防震研究院, 贵州 贵阳 550001;中国地质大学地球科学学院, 湖北 武汉 430074;贵州省地震局, 贵州 贵阳 550001,中国地质大学地球科学学院, 湖北 武汉 430074,中国地质大学地球科学学院, 湖北 武汉 430074,中国地质大学地球科学学院, 湖北 武汉 430074,中国地质大学地球科学学院, 湖北 武汉 430074;中国地质大学地质调查研究院, 湖北 武汉 430074
基金项目:中国地质调查局项目(1212011220400)资助。
摘    要:昆阳群的形成时代、沉积环境、源岩性质等一直存在较大争议,为了查明滇中地区昆阳群的物源及其形成的构造环境,文章在分析昆阳群沉积组合和沉积相的基础上,对昆阳群3件变质砂岩样品中的碎屑锆石进行LA-ICPMS锆石U-Pb年龄测定,对昆阳群20件极低级变质碎屑岩进行地球化学分析。从昆阳群黄草岭组、黑山头组和美党组中分别获得了最年轻的谐和年龄为984.0 Ma、945.0 Ma和954.0 Ma;碎屑锆石年龄峰谱显示,在1.0 Ga、1.35Ga、1.73 Ga和2.44 Ga出现了统计峰值,其年龄主要集中在1.73 Ga和1.35 Ga。表明昆阳群源区主要经历了1.0 Ga、1.35 Ga、1.73 Ga和2.44 Ga的构造热事件,资料显示扬子地块西南缘出露的大红山群形成时代为1.7 Ga,格林威尔期的构造热事件时期为1.0~1.3 Ga。此外,地球化学分析结果表明昆阳群源岩主要是形成于大陆岛弧—活动大陆边缘的石英质旋回沉积、长英质岩石和少量镁铁质岩石。在中元古代晚期—新元古代早期(0.95~1.0 Ga),Rodinia超大陆形成阶段,在扬子地块西南缘的弧后前陆盆地中形成昆阳群的沉积组合,物源主要来自扬子地块西南缘的大红山群和格林威尔期岛弧的岩石。

关 键 词:昆阳群  碎屑锆石  地球化学  物源  构造环境
收稿时间:2016/1/14 0:00:00
修稿时间:2016/4/14 0:00:00

Provenance and tectonic setting of the Kunyang Group in central Yunnan Province
JI Xing-xing,ZHOU Shi,CHEN Qi,LIU De-min and LI De-wei.Provenance and tectonic setting of the Kunyang Group in central Yunnan Province[J].Chinese Geology,2016(3):857-878.
Authors:JI Xing-xing  ZHOU Shi  CHEN Qi  LIU De-min and LI De-wei
Institution:School of Earthquake Engineering of Guizhou Province, Guiyang 550001, Guizhou, China;School of Earth Sciences, China University of Geosciences, Wuhan 430074, Hubei, China;Earthquake Administration of Guizhou Province, Guiyang 550001, Guizhou, China,School of Earth Sciences, China University of Geosciences, Wuhan 430074, Hubei, China,School of Earth Sciences, China University of Geosciences, Wuhan 430074, Hubei, China,School of Earth Sciences, China University of Geosciences, Wuhan 430074, Hubei, China and School of Earth Sciences, China University of Geosciences, Wuhan 430074, Hubei, China;Institute of Geological Survey, China University of Geosciences, Wuhan 430074, Hubei, China
Abstract:Formation age, sedimentary environment and source rock characteristics of the Kunyang Group are problems of considerable controversy. In order to identify the provenance and tectonic setting of the Kunyang Group in central Yunnan, the authors analyzed the sedimentary assemblage and sedimentary facies of the Kunyang Group, and conducted LA-ICP-MS detrital zircon U-Pb dating of 3 metamorphic sandstone samples from the Kunyang Group, which yielded different youngest concordant ages for Huangcaoling Formation, Heishantou Formation and Meidang Formation, being 984.0 Ma, 945.0 Ma and 954.0 Ma respectively. Age spectrum of these detrital zircons reveals a wide age range from Archean to Neoproterozoic with prominent peak at ~1.0 Ga, ~1.35 Ga and ~1.73 Ga and the second peak at ~2.44 Ga, mainly concentrated on ~1.35 Ga and ~1.73 Ga. It is inferred that the Kunyang Group source area mainly experienced 1, 1.35 and 1.73-2.44 Ga tectonic thermal events, and the age of the Dahongshan Group in southwest Yangtze Block is about 1.7Ga. The period of tectonic thermal event in Greenvillian is from 1.0 Ga to 1.3Ga. The authors also analyzed the geochemical characteristics of 20 extremely low-grade metamorphic rocks from Kunyang Group. The result shows that source rocks of Kunyang Group are quartzose cyclic sediments, felsic rocks and some mafic rocks formed in active continental margin or continental island arc. It is concluded that, from late Mesoproterozoic to early Neoproterozoic (0.95-1.0 Ga), the Kunyang Group was formed in the foreland basin with its provenance mainly from the Dahongshan Group in southwestern Yangtze block and Grenville-aged island arc.
Keywords:Kunyang Group  Detrital zircon  geochemistry  provenance  tectonic environment
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