Identification and Zircon U-Pb Geochronology of the Yingchengzi Paleoarchean Gneiss Complex, Anshan Area
详细信息
- 责任者：Zhang Jiahui (College of Earth Science ; Jilin University ; Changchun 130021 ; China) ; Jin Wei
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(2)
- 关键词：片麻岩 ; gneisses ; 铀—铅计时 ; U-Pb dating ; 辽宁 ; Liaoning Province
- 页码：p.399-413
- 图表：illus., 2 tables, 34 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Eoarchean-Neoarchean granitite complexes are widely distributed in the Anshan area, which is a classical place for studying early crustal material composition and evolution. We newly identified a suit of the Yingchengzi gneiss complex and trondhjemite assemblages through large-scale field lithology survey work. This provides new evidences and clues for comparing regional ancient rock series, recovering the tectonic structures and revealing the Archean crustal formation and evolution in the Anshan area. The gneiss complex mainly consists of stromatic biotite plagioclase gneiss, vein trondhjemitic gneiss and biotite schist, which occur as xenolithes in different sizes in the trondhjemite with fine texture and homogenous massive structure. The rock assemblage, complicated and heterogeneous rock fabric of the gneiss complex show characteristics of an anatectic migmatite. SIMS zircon U-Pb dating results indicate that the stromatic biotite plagioclase gneiss and biotite schist have the ages of 3312±14Ma, 3304±7Ma and 3324±7Ma～3235±14Ma respectively, indicating an Paleoarchean thermal event. In addition, several samples contain inherited zircons with ages of 3.68～3.60Ga and～3.47Ga age. The fine grained biotite trondhjemite formed 3.14～3.13Ga, which is consistent with the regional Mesoarchean magmatic events. Regional comparative study reveals that the rock assemblage, occurrence relationship and chronological characteristics of the Yingchengzi gneiss complex are similar with the Dongshan complex and Shengouzi complex, all of which were the products of the Paleoarchean (3.33～3.24Ga) anatexis. The Yingchengzi gneiss complex in the Anshan area is another geologic body which preserved information of ancient zircons and Early Archean crustal rocks.
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