青海东昆仑东段塔妥地区小庙岩组变质岩LA-ICP-MS锆石U-Pb年龄及其地质意义  

LA-ICP-MS zircon U-Pb ages of metamorphic rocks from Xiaomiao Formation in Tatuo area of eastern East Kunlun Mountains and their geological significance

作　　者：王旭斌[1] 裴先治[1,2] 李瑞保[1,2] 陈有炘[1] 刘成军[1] 李佐臣[1,2] 杨森[1] 桑继镇 陈功[1] 邓文兵 

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》2016年第7期1144-1157,共14页Geological Bulletin of China

基　　金：国家自然科学基金项目(批准号:41472191;41502191;41172186);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资金项目(CHD2011TD020;2013G1271091;2013G1271092;310827161002;310827161006)

摘　　要：东昆仑地区小庙岩组的形成时代长期存在争议，且缺少精确的年代学证据。以东昆仑东段塔妥地区小庙岩组变质碎屑岩为研究对象，采用LA-ICP-MS锆石U-Pb同位素定年方法，探讨其形成时代。结果显示，锆石具有较宽的年龄谱（1551~2624Ma），可划分为2624~2603Ma、2501~2290Ma、2196~2036Ma和1921~1551Ma年龄组，最后一组可进一步划分为1921~1690Ma和1641~1551Ma两个亚组。其中1921~1690Ma代表了物源区强烈的变质岩浆热事件，具有最强峰值特征（峰值年龄为1783Ma），而2501~2290Ma代表了源区一次变质事件，并有少量2196~2036Ma年龄记录，个别2600Ma的碎屑锆石暗示东昆仑地区存在新太古代的陆核。1641~1551Ma（加权平均年龄为1597Ma）代表了小庙岩组发生变质的时间，而物源区最晚变质年龄为1690Ma，从而确定小庙岩组形成于1690~1597Ma，属中元古代。对比碎屑锆石年龄频谱和东昆仑地区较老变质基底记录的构造-热事件信息，小庙岩组主要沉积物源可能来自于古元古界白沙河岩组，而东昆仑与华北在古元古代末—中元古代早期构造事件的对比揭示，在这一时期二者具有相似的构造演化特征。There has been long controversy over the formation age of the Xiaomiao Formation in the eastern part of East Kunlun oro-genic belt due to the lack of precise age. Choosing the meta-detrital rocks of Xiaomiao Formation in Tatuo area in eastern East Kun-lun orogenic belt as the study objects, the authors used LA-ICP-MS zircon U-Pb isotope geochronologic method to study the for-mation age of Xiaomiao Formation. The result shows that it has a wide age range （1551~2624Ma） which can be evidently divided in-to four groups, namely 2624~2603Ma, 2501~2290Ma, 2196~2036Ma and 1921~1551Ma, and the last group can be further divided into two subgroups of 1921~1690Ma and 1641~1551Ma. The age range 1921~1690Ma with the most intense peak value of 1783Ma represents a metamorphism and magmatism of the source region whereas the age range 2501~2290Ma represents a metamorphism of＆nbsp;the source region. The detrital zircon also has the age range 2196~2036Ma with some detrital zircons being 2600Ma, which implies that there exists a Neoarchean basement in East Kunlun. The age range 1641~1551Ma （weighted average age equal to 1597Ma） repre-sents the metamorphism time of Xiaomiao Formation, and the latest metamorphism age of the source region is 1690Ma, which re-stricts the formation age of Xiaomiao Formation, which should belong to Mesoproterozoic. The contrast of the metasedimentary zir-con age range and metamorphosed basement tectonic-thermal event of the East Kunlun Mountains shows that the main sediments of Xiaomiao Formation were from Mesoproterozoic Baishahe Formation, and East Kunlun area and North China Craton have similar tectonic evolution processes from the end of Paleoproterozoic to the beginning of Mesoproterozoic, as shown by contrasting their tec-tonic-thermal events.

关 键 词：东昆仑 LA-ICP-MS锆石U-PB年龄 小庙岩组 中元古代 

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