SHRIMP Dating and Hf Isotope Analysis of Zircons from the Early Precambrian Basement in the Xi Ulanbulang Area, Wuchuan, Inner Mongolia
详细信息
- 责任者：Ma Mingzhu (Beijing SHRIMP Center ; Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Xu Zhongyuan
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(2)
- 关键词：变质岩 ; metamorphic rocks ; 内蒙古 ; Inner Mongolia
- 页码：p.501-516
- 图表：illus., 4 tables, 34 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
This paper reports SHRIMP U-Pb ages and Hf isotopes of zircons from Archean basement in the Xi Ulanbulang area, Wuchuan, western North China Craton (NCC). Zircons from a trondhjemite gneiss sample show core-rim textures, with magmatic cores and metamorphic rims having weighted mean 207Pb/206Pb ages of 2692±17Ma and 2528±16Ma, respectively. Hf isotope analyses have been carried out on zircons from 9 samples. Magmatic zircons of Early Neoarchean (2692～2697Ma) trondhjemite gneisses (2 samples) have εHf(t), tDM1(Hf) and tDM2(Hf) being 4.78～8.83, 2646～2780Ma and 2632～2845Ma, respectively. Captured zircons of Neoarchean two-pyroxene granulite (2 samples) have εHf(t), tDM1(Hf) and tDM2(Hf) of -2.30～8.62, 2543～2954Ma and 2529～3189Ma. Neoarchean meta-intrusive rocks (4 samples) have magmatic zircons with εHf(t) values of -2.60～8.09, tDM1(Hf) ages of 2529～2880Ma and tDM2(Hf) ages of 2538～3089Ma. Analyses on detrital zircons from a Paleoproterozoic kyanite-garnet felsic gneiss yielded εHf(t) values ranging from 1.52 to 6.59 and tDM1(Hf) and tDM2(Hf) model ages of 2432～2774Ma and 2498～2925Ma. Combined with early studies, we draw conclusions as follows: 1) in the study area, there are Early Neoarchean TTG rocks which underwent strong metamorphism at the end of Neoarchean together with Late Neoarchean rocks; 2) Early Neoarchean is an important period when continental crust was formed, however, in Late Neoarchean, reworking of older continental materials played an important role; 3) Guyang-Wuchuan, a typical area of the Archean Yinshan block, is similar to the Archean basement of the eastern NCC in many aspects, supporting an idea that the NCC had already been a single unit at the end of the Neoarchean.
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