Zircon U-Pb Chronology, Geochemistry and Their Petrogenesis of Early Paleoproterozoic Granitoid Gneisses in Ulashan Area, North China Craton
详细信息
- 责任者：Liu Jianhui (Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Liu Fulai
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(2)
- 关键词：花岗质片麻岩 ; granitic gneiss ; 内蒙古 ; Inner Mongolia
- 页码：p.485-500
- 图表：illus., 2 tables, 62 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Early Paleoproterozoic granitoid gneisses are widely distributed in Ulashan area in the khondalite belt, North China Craton, they record continent-crustal growth and tectonic evolution in the study area. The LA-ICP-MS U-Pb analyses of zircons from four representative granitoid gneiss samples collected from the study area unraveled that they formed at～2.45Ga, and experienced polyphase metamorphic events at ～2.45Ga and 1.89～1.95Ga. The geochemical analyses of the Early Paleoproterozoic granitoid gneisses show they are characterized by high REEs contents (∑REE=301×10-6～909×10-6), enrichment in light REE and depletion in heavy REE with (La/Yb)N ratios of 13～56. They have weakly positive and/or negative Eu anomalies (Eu/Eu*=0.76～1.81,average 1.18), high Sr content (495×10-6～895×10-6) and low Yb content (0.5×10-6～2.61×10-6). Their primitive mantle normalized trace element spider diagrams show they are strongly depleted in high field-strength element Nb, Ta, Th, U, and Ti, and are enrich in large ion lithophile element Ba, K, Rb and Sr. They are magnesian, high-K calc-alkalic and metalumous-weakly peraluminous, indicating that they originated from partial melting of basaltic lower crust under island arc on margin of active continent. It is suggested that there existed arc-continent accretionary process during Early Paleoproterozoic, and experienced tectonic evolutional history of arc-continent accretion, continent-continent collision and extensions post-orogen in Ulashan area.
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