华北克拉通桑干地区高压麻粒岩的锆石SHRIMP U-Pb年龄及其地质含义  

Zircon SHRIMP U-Pb age of the Paleoproterozoic high-pressure granulites from the Sanggan area,the North China Craton and its geologic implications

作　　者：张华锋[1] 翟明国[2] 彭澎[2] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《地学前缘》2006年第3期190-199,共10页Earth Science Frontiers

基　　金：国家自然科学基金资助项目(40372089;40234050);华北地区基础地质调查与数据更新项目(1212010510506)

摘　　要：为了揭示华北克拉通桑干地区古元古代高压麻粒岩变质峰期时限，对选自该区的两个高压麻粒岩样品（DST02，XYS01）进行了锆石SHRIMPU-Pb测年。锆石样品的阴极发光图像显示为球形和无内部结构，Th／U比值变化为0．01～0．93。这些特征表明两样品的锆石应属于变质成因锆石。两样品的SHRIMP测年结果分别给出（1792±12）Ma和（1891±46）Ma。根据前人的年代学方面的研究成果，特别是未变质强过铝花岗岩中获得的1900～1850Ma的锆石U-Pb年龄（郭敬辉等，2002）结果来看，本区高压麻粒岩峰期变质时代不会晚于此。因此本文获得的1850-1800Ma的锆石SHRIMP U—Pb年龄应代表退变年龄。而（1891±46）Ma的年龄限定了峰期高压变质年龄上限。Zircons extracted from high-pressure granulite and strongly peraluminous granites from the Sanggan area of the North China Craton, have been investigated by integrating petrogenesis with U-Pb ages. The isometric internal structure and round shape of the zircons as revealed by cathodoluminescence, in combination with low Th/U ratios （0. 01-0. 93 ）, indicate that they crystallized or recrystallized under metamorphic conditions and the ages obtained must be representative of the metamorphic age. Concordant U-Pb ages of （1 792±12） Ma （8 points） and （1 891±46） Ma （19 points） were obtained from zircons of the sample DST02 and XYS01, respectively. Zircons U-Pb ages of 1 900-1 850 Ma obtained from unmetamorphosed strongly peraluminous granites, indicate that the upper limit of the peak metamorphic age could not be younger than 1 900 or 1 850 Ma. Therefore, the U-Pb ages of （1 792±12） Ma and （1 891±46） Ma are proposed to represents the time of retrograde and peak granulite metamorphic ages, respectively.

关 键 词：华北克拉通 桑干地区 古元古代 高压麻粒岩 U-PB年龄 

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