地质学报2011，Vol.85Issue(8)：1284-1290,7.DOI:11-1951/P.20110804.1239.009
南秦岭略阳鱼洞子岩群磁铁石英岩形成时代的锆石U-Pb年代学约束
Constraints from Zircon U-Pb Chronology of Yudongzi Group Magnetite-Quartzite in the Lueyang Area, Southern Qinling, China
摘要
Abstract
Yudongzi complex is a significant Archean basement exposed in the Qinling orogenic belt and also the oldest geological mass in the Qinling area. It is composed mainly of metamorphic strata (Yudongzi Group) and granitic metamorphic intrusions with various sizes, most of which contact with structural foliation. The Yuzidong Group is an important iron-hosting horizon, but there has been no reliable evidence for formation ages of iron deposit and ore-hosting country rocks. The study picked lots of zircons from magnetite quartzite at that Xiaogoushan mining area. CL images of zircons show a distinct mantle-edge structure which most zircons have, oscillatory zoning developed within mantle indicating magmatic in origin, and late-stage metamorphic, grayish zoning edge. According to CL imaging features and genetic analysis of zircons, we obtained an upper intercept age of 2645 ±25 Ma(MSWD=1. 2) and a weighted mean 207Pb/206Pb age of 2645 ±24 Ma for the magnetite-quartzite magmatic zircons in Xiaogoushan mine area using microdomain U-Pb isotope LA-ICP-MS (laser ablation ICP-MS) determination. Two ages are consistent to each other, representing the formation age of protolith of quartzite. The upper intercept age of 2555±24 Ma (MSWD=1. 4) for the metamorphic zircons is consistent with the weighted mean 207Pb/ 206Pb age of 2527±27 Ma within the error range, and should indicate the metamorphic age of quartzite. This age reflects an important regional metamorphic event occurring in the Archean. From above we can say that the age reflects an important regional metamorphism event in Archean.关键词
秦岭造山带/鱼洞子岩群/磁铁石英岩/锆石/年代学Key words
Qinling Orogenic Belt/ Yudongzi rock group/ magnetite-quartzite/ zircon/ chronology引用本文复制引用
王洪亮,徐学义,陈隽璐,闫臻,李婷,朱涛..南秦岭略阳鱼洞子岩群磁铁石英岩形成时代的锆石U-Pb年代学约束[J].地质学报,2011,85(8):1284-1290,7.基金项目
本文为国土资源大调查项目(编号1212010610319)、国家自然科学基金项目(编号40773044和40472044)、国家科技支撑计划项目(编号2006BAB01A11)和西北大学大陆动力学国家重点实验室开放课题基金(编号06LCD16)资助成果. （编号1212010610319）
