鄂尔多斯盆地西缘石岗沟地区直罗组碎屑锆石LA-ICP-MS U-Pb年代学特征及物源区判定  

LA-ICP-MS U-Pb CHRONOLOGICAL CHARACTERISTICS OF DETRITAL ZIRCON FROM ZHILUO FORMATION AND ITS PROVENANCE IN SHIGANGGOU REGION,WESTERN ORDOS BASIN

作　　者：罗伟[1] 刘池洋[1] 张东东[1] 王建强[1] 郭配 牛海青[1] 赵岩[1] 王飞飞[1] 

机构地区：[1]西北大学大陆动力学国家重点实验室,陕西西安710069

出　　处：《矿物岩石》2015年第4期106-115,共10页Mineralogy and Petrology

基　　金：国家自然科学基金项目(41330315);中国地质调查局专项项目(12120113039900;12120114009201)

摘　　要：在对鄂尔多斯盆地中侏罗统直罗组地层矿产资源的勘探中,于其西缘部分地区的直罗组地层发现油气及铀矿的相关性显示,以此判定其物源区对进一步的勘探开发具有重要作用。应用碎屑锆石LA-ICP-MS U-Pb年代学研究方法准确分析和确定直罗组地层物源区位置,实验样品选取直罗组中碎屑锆石所得年代学结果显示缺少加里东期碎屑锆石,且锆石Th/U比值均>0.1,结合CL图像确定锆石均为岩浆成因,测定结果表明其年龄可以分为3个年龄段:1230 Ma^310 Ma年龄段,峰值年龄为268.8 Ma;属于天山-兴蒙褶皱带在晚海西—印支期提供大量沉积物源。2340Ma^400Ma年龄段,峰值年龄为391.2 Ma;碎屑锆石少,海西早期构造热事件不强烈,该时期物源由天山-兴蒙褶皱带供给。31 600 Ma^2 600 Ma年龄段,表现出3个峰值年龄,分别为1 912.9 Ma,2 134.7Ma和2 494.1 Ma;对应吕梁—晋宁时期,存在3期构造热事件,物源来自于华北板块结晶基底及贺兰山杂岩。综上所述,鄂尔多斯盆地西缘直罗组存在3个物源区,以天山-兴蒙褶皱带作为主要的物源区。The Zhiluo Formation in western Ordos Basin shows mineralization about oil,gas and uranium. Chronological characteristics of zircons in the Zhiluo Formation are studied by LA-ICP- MS zircon U-Pb so as to determine the provenance of Zhiluo Formation. The ratio of Th/U C〉1） and the CL images of zircons indicate that all the zircons belong to magmatic origin. LA-ICP-MS zircon U-Pb dating reveals following results .. O230 Ma to 310 Ma,with peak value of 268.8 Ma, they belong to the Tianshan Xingmeng folded belt which provided the major provenance in Hercynian-Indosinian age;（2）Q340 Ma to 400 Ma,with peak value of 391.2 Mal the amount of this sort of zircons is small,representing a less strong tectonic-thermal event in early Hercynian with the Tianshan Xingmeng folded belt as its provenance;（3）l 600 Ma to 2 600 Ma,with three peak values of 1912.9 Ma,2134. 7 Ma and 2 494. 1 Ma respectively,representing 3 thermo-tectonic events and with the Huabei plate crystalline basement and Holanshan complex rock as its provenance. There- fore,there were 3 provenances for the Zhiluo Formation in western Ordos basin, and Tianshan- Xingmeng folded belt is the main sources of Zhiluo Formation.

关 键 词：碎屑锆石 U—Pb年代学 物源区 峰值年龄 褶皱带 

分 类 号：P597.1[天文地球—地球化学] P588.121[天文地球—地质学]