| 高级变质作用对锆石U-Pb同位素体系的影响:胶东栖霞地区变质闪长岩锆石定年 |
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| 引用本文： | 万渝生,刘敦一,董春艳,刘守偈,王世进,杨恩秀.高级变质作用对锆石U-Pb同位素体系的影响:胶东栖霞地区变质闪长岩锆石定年[J].地学前缘,2011,18(2):17-25. |
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| 作者姓名： | 万渝生 刘敦一 董春艳 刘守偈 王世进 杨恩秀 |
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| 作者单位： | 万渝生,刘敦一,董春艳,刘守偈,Wan Yusheng,Liu Dunyi,Dong Chunyan,Liu Shoujie(中国地质科学院,地质研究所北京离子探针中心,北京,100037);王世进,杨恩秀,Wang Shijin,Yang Enxiu(山东省地质调查院,山东,济南,250013) |
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| 基金项目： | 中国地质构造区划与区域地质调查综合集成项目,中国地质调查局霞点资助项目 |
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| 摘 要： | 文中对高级变质作用(高角闪岩相-麻粒岩相)条件下"干的"岩石体系中锆石U、Th、Ph行为进行了研究.样品为胶东栖霞地区太古宙变质基底的高角闪岩相-麻粒岩相变质闪长岩.矿物组合为单斜辉石+斜长石+钾长石+黑云母+石英.锆石呈近短轴状、等轴状和不规则状,阴极发光下具板状、杉树叶状、扇形结构,部分具封闭环带结构.锆石中存在斜...
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| 关 键 词： | 锆石 U-Th-Pb体系 铅丢失 高级变质作用 SHRIMP定年 早前寒武纪 胶东 |
The impact of high-grade metamorphism on the U-Th-Pb system of zircons:A case study of zircon dating of meta-diorite in Qixia Area, eastern Shandong |
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| Wan Yusheng,Liu Dunyi,Dong Chunyan,Liu Shoujie,Wang Shijin,Yang Enxiu.The impact of high-grade metamorphism on the U-Th-Pb system of zircons:A case study of zircon dating of meta-diorite in Qixia Area, eastern Shandong[J].Earth Science Frontiers,2011,18(2):17-25. |
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| Authors: | Wan Yusheng Liu Dunyi Dong Chunyan Liu Shoujie Wang Shijin Yang Enxiu |
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| Institution: | 1.Beijing SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China 2.Shandong Geological Survey Institute,Jinan 250013,China |
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| Abstract: | This paper presents a study of the U-Th-Pb behavior of zircons in a "dry" rock system during high-grade metamorphism in the Archean basement of eastern Shandong.The studied sample has a mineral assemblage of plagioclase+K-feldspar+clinopyroxene+biotite+quartz and its protolith is considered to be diorite.The zircons are stubby,equant or irregular in shape and show fir-leaf,sector,banded or oscillatory zoning.They contain inclusions,including the mineral assemblages of clinopyroxene+orthopyroxene+hornblende+quartz and plagioclase+K-feldspar+biotite+quartz.Fifty SHRIMP analyses were carried out on 34 zircon grains and commonly yielded high Th/U ratios(mostly>0.5).Most analyses are distributed along a concordia from 2.54 to 2.25 Ga,with the youngest age of about 1.95 Ga.Compositions and ages show large variations even in an individual zircon grain.Combined with early studies,conclusions have been drawn as follows:(1) the diorite underwent two episodes of high-grade metamorphism both at the end of the Neoarchean and the Paleoproterozoic(about 2.50 Ga and about 1.95 Ga or slightly later);(2) high-grade metamorphism in a "dry" rock system may partially reset the U-Th-Pb system of zircons,and in this case,the ages between the oldest and youngest are chronologically meaningless;(3) high Th/U ratios may be common features of the zircons formed during high-grade metamorphic conditions. |
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| Keywords: | zircon U-Th-Pb system lead loss high-grade metamorphism SHRIMP dating Early Precambrian eastern Shandong |
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