河北平山湾子群的时代:SHRIMP锆石年代学证据  

SHRIMP U-Pb Geochronology Evidence for the Formation Time of the Wanzi Group at Pingshan County, Hebei Province

作　　者：李基宏[1] 杨崇辉[2] 杜利林[2] 万渝生[2] 刘增校 

机构地区：[1]吉林大学地球科学学院 [2]中国地质科学院地质研究所,北京100037 [3]河北地质矿产调查研究所,河北廊坊06500

出　　处：《地质论评》2005年第2期201-207,共7页Geological Review

基　　金：中国地质调查项目 (编号 199913 0 0 0 0 0 3 );国家自然科学基金重大国际合作项目 (编号 40 42 0 12 0 13 5 )资助成果。

摘　　要：经过研究 ,将太行山地区原阜平群中一套浅粒岩、斜长角闪岩和钙硅酸盐岩及大理岩构成的稳定组合解体出来 ,建立了湾子群。本文对河北平山板桥沟地区湾子群中的钾长浅粒岩进行了锆石成因和年代学研究。阴极发光 (CL )图像显示浅粒岩中的锆石主要为具有震荡环带的岩浆型碎屑锆石 ,其 Th/ U >0 .38,表明原岩主要为火成岩。SHRIMP分析结果表明碎屑锆石的结晶年龄为 2 5 36 Ma,并且部分颗粒有 2 0 81 Ma深熔作用的增生边。笔者综合各方面研究成果 ,推测湾子群形成于 2 .5～ 2 .1 Ga之间 ,为古元古代的产物。并且在 2 0 81 Ma经历了强烈的深熔作用的影响 ,形成了太行山地区广泛分布的古元古代钾质花岗岩。这一研究结果为探讨太行山地区的地质演化提供了重要的年代学依据。In the Taihang Mountains, we separated a set of leucoleptite, amphibolite, calc-silicate and marble assemblages from the old Fuping Group to set up the Wanzi Group, and studied the genesis and chronology of the zircons in leucoleptite from the Wanzi Group in the Banqiaogou area, Pingshan County. The CL images reveal that prismatic and oscillatory-zoned zircons with Th/U>0.38 are dominant in the leucoleptite of the Wanzi Group and interpreted as detrital magmatic zircons with igneous rocks as their protoliths. The mean 207Pb/ 206Pb age of 2536±12 Ma is interpreted as the crystallization age of the igneous rocks contributing to the leucoleptite and some zircons underwent anatexis at 2081 Ma. We thus infer that the Wanzi Group was formed in the Paleoproterozoic between 2.5 Ga and 2.1 Ga, and underwent anatexis at 2081 Ma, which produced widely distributed Paleoproterozoic kaligranite. This research provides significant chronological evidence for understanding the geological evolution of the Precambrian complex in the Taihang Mountains.

关 键 词：SHRIMP 锆石年代学 子群 北平 太行山地区 证据 碎屑锆石 深熔作用 古元古代 钙硅酸盐岩 斜长角闪岩 浅粒岩 图像显示 阴极发光 分析结果 研究成果 地质演化 研究结果 阜平群 大理岩 岩浆型 火成岩 花岗岩 成因 原岩 钾质 

分 类 号：P597.3[天文地球—地球化学]