西秦岭两当地区太阳寺岩组碎屑锆石LA-ICP-MSU-Pb年龄:形成时代与源区特征  

Detrital zircon LA-ICP-MS UPb dating of the Taiyangsi Formation in Liangdang area, Western Qinling and its implications for material source and sedimentaryage

作　　者：刘图杰 裴先治[1,2] 刘成军[1] 李佐臣[1,2] 李瑞保[1,2] 魏博[1] 王元元[1] 任厚州 胥晓春 陈伟男[1] 

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]西部矿产资源与地质工程教育部重点实验室,陕西西安710054

出　　处：《地质通报》2014年第7期1028-1040,共13页Geological Bulletin of China

基　　金：国家自然科学基金项目(批准号:41172186;40972136;40572121);教育部高等学校博士学科点专项科研基金项目(编号:20110205110004);中央高校基本科研业务费专项(编号:CHD2011TD020;2013G1271091;2013G1271092)

摘　　要：选取西秦岭两当地区太阳寺岩组的变质碎屑岩为研究对象,依据CL图像,采用LA-ICP-MS锆石U-Pb同位素定年方法,探讨两当地区太阳寺岩组的形成时代与物源。两当地区太阳寺岩组的锆石U-Pb年龄及与邻近地层的变质变形关系和时代对比表明,太阳寺岩组的沉积时代为426～420Ma,为晚志留世—末志留世。太阳寺岩组的碎屑锆石年龄谱可分为4组：500～420Ma、955～550Ma、1866～1227Ma和3039～2132Ma。早古生代年龄组呈现最强的烈峰值特征,峰值为438Ma,该组锆石物源以西秦岭北缘构造带为主;新元古代年龄组的碎屑锆石物源为西秦岭北缘构造带和北祁连造山带;中元古代和古元古代—新太古代年龄组的碎屑锆石物源主要来自于北祁连造山带和西秦岭北缘构造带基底岩系。综合分析认为,西秦岭北缘构造带为天水两当地区太阳寺岩组碎屑沉积物的主要源区。Detailed observations of CL images and LA-ICP-MS detrital zircon U-Pb ages of the metasandstone samples from Liangdang area of Western Qinling provide information about the provenance of Taiyangsi Formation. The ages of detrital zircons show that the sedimentary ages of the Taiyangsi Group range from 426 to 420 Ma, suggesting Ludlow to Pridoli period. The U-Pb detrital zircon ages can be assigned to four age groups： 500～420Ma, 955～550Ma, 1866～1227Ma and 3039～2132Ma. Early Paleozoic age group shows the most strong peak age of 438 Ma, implying that the material source was mainly from the north margin of Western Qinling tectonic belt. The detrital zircons with Neoproterozoic age were related to the magma of the north margin of Western Qinling tectonic belt and Northern Qilian orogenic belt in the Neoproterozoic. The detrital zircons with Mesoproterozoic age and Paleoproterozoic-Neoarchaean age were mainly from the basement of Northern Qilian orogenic belt and the north margin of Western Qinling tectonic belt. A comprehensive analysis reveals that the material source of Taiyangsi Formation was mainly from the north margin of Western Qinling tectonic belt.

关 键 词：LA-ICP-MS锆石U-PB年龄 形成时代 物源 太阳寺岩组 西秦岭 两当地区 

分 类 号：P588.344[天文地球—岩石学] P597.3[天文地球—地质学]