东昆仑地区纳赤台群碎屑岩段碎屑锆石LA-ICP-MS U-Pb年龄及其地质意义  

LA-ICP-MS U-Pb dating of the detrital zircons from clastic rocks of Naij Tal Group in East Kunlun and its geological implications

作　　者：靳立杰 周汉文[1,3,4] 王继林[1,5] 朱云海[1,6] 林启祥[1,6] 

机构地区：[1]中国地质大学(武汉)地球科学学院,湖北武汉430074 [2]山东第一地质矿产勘查院,山东济南250014 [3]地质过程与矿产资源国家重点实验室,湖北武汉430074 [4]教育部长江三峡库区地质灾害研究中心,湖北武汉430074 [5]中国冶金地质总局山东局测试中心,山东济南250014 [6]中国地质大学(武汉)地质调查研究院,湖北武汉430074

出　　处：《地质通报》2015年第10期1848-1859,共12页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:1212011086001)

摘　　要：纳赤台群是东昆仑造山带中段出露的构造混杂岩的重要组成部分,对纳赤台群碎屑岩段的地层时代及物质来源进行限定,可以为恢复和反演东昆仑早古生代的构造格局提供依据。前人多认为纳赤台群的地层时代为奥陶纪或奥陶纪—志留纪,但是志留纪、二叠纪甚至新生代的观点也同时存在。通过对纳赤台群碎屑岩段进行碎屑锆石年龄研究,得到最年轻的锆石年龄538±10Ma,结合侵入其中的英云闪长岩体的年龄为427.7Ma,将纳赤台群碎屑岩的沉积时代限定于538~427Ma之间,另外由于纳赤台群特殊的演化意义,结合沙松乌拉组和赛什腾组的地层时代,将纳赤台群碎屑岩的地层时代确定为奥陶纪,并认为有可能延伸至早志留世。得到的碎屑锆石年龄谱显示约2450Ma、约1100Ma、约980Ma、约810Ma、约650Ma五个明显峰值,结合纳赤台群碎屑岩近源堆积的特征,将得到的锆石年龄与东昆仑及邻区出露的老地层和岩体时代进行比对,推测白沙河岩组、小庙群、万宝沟群及新元古代早期在东昆仑地区形成的中酸性岩体为其可能物源。将得到的锆石年龄与各期重大构造-岩浆事件在昆仑造山带留下的地质记录进行对比,推测认为,纳赤台群碎屑岩的源区存在太古宙结晶基底,并经历了古元古代早期构造-岩浆事件、中元古代晚期构造-岩浆事件（格林威尔运动）和新元古代早期构造-岩浆事件。Naij Tal Group consists of a set of ophiolitic m61anges. Therefore, some evidence for restoring the structural pattern of east Kunlun in Early Palaeozoic can be obtained by studying Naij Tal Group＇ s formation time and provenance. Most previous researchers hold the opinion that Naij Tal Group belongs to Ordovician or Ordovician-Silurian; nevertheless, other viewpoints arguing for Silurian, Permian or Cenozoic are also existent. The authors obtained the youngest age 538＋10Ma by LA-ICP-MS U-Pb dating of the detrital zircons from Naij Tal Group＇s clastic rocks and thus confined its formation time to 538-427Ma in combination the intrusion age of 427.7Ma. Thus, the formation age of Naij Tal Group was assigned to Ordovician because of its special geological significance. Moreover, there are five age peaks existent in Naij Tal Group＇s detrital zircons, i.e., ~2450Ma, -1100Ma, -980Ma, ~810Ma, and ~ 650Ma. The authors thus suppose that Baishahe Group, Xiaomiao Group, Wanbaogou Group and magmatic rocks formed during ear- ly Neoproterpzoic were provenances of Naij Tal Group＇s clastic rocks because of the similar distributions of their zircon ages. It is al- so held that the source areas might have experienced early Paleoproterozoic, late Paleoproterozoic, late Mesoproterpzoic and early Neoproterpzoic tectono-magmatic events according to the characteristics of their zircon U-Pb ages.

关 键 词：东昆仑纳赤台群 碎屑锆石LA-ICP-MS U-PB年龄 地层时代 物源 构造-岩浆事件 

分 类 号：P597.3[天文地球—地球化学]