Zircon U-Pb geochronology of Archean high-grade metamorphic rocks from Xi Ulanbulang area,central Inner Mongolia  

作　　者：DONG XiaoJie XU ZhongYuan LIU ZhengHong SHA Qian 

机构地区：[1]College of Earth Science,Jilin University,Changchun 130061,China

出　　处：《Science China Earth Sciences》2012年第2期204-212,共9页中国科学（地球科学英文版）

基　　金：supported by National Natural Science Foundation of China (Grant Nos. 90814006, 40972135);Geological Survey of China (Grant No. 1212010510515)

摘　　要：The early Precambrian high-grade metamorphosed basement in the Xi Ulanbulang area, central Inner Mongolia of China, is composed mainly of intermediate granulites and charnockitic gneisses. Both types of the rocks are closely associated spatially and temporally, with a gradual variation between them. In order to understand timing of the high-grade metamorphism, we carried out SHRIMP U-Pb dating of zircons of the rocks. Zircons from the granulites and charnockitic gneisses are similar in structure and age. Zircon cores show magmatic zoning and have ages of 2507-2545 Ma. The ages are interpreted as the forming time of protolith of the granulites and charnockitic gneisses, indicating that a strong magmatism existed at that time in the Yinshan Block. The zircon mantles and rims show homogeneous structures and record a strong granulite facies metamorphism event around 2500 Ma, with a time interval between the metamorphism and magamatism being less than 50 Ma. These suggest that the Western Block was similar to the Eastern Block in tectono-thermal timing at the end of the Neoarchean.The early Precambrian high-grade metamorphosed basement in the Xi Ulanbulang area, central Inner Mongolia of China, is composed mainly of intermediate granulites and charnockitic gneisses. Both types of the rocks are closely associated spatially and temporally, with a gradual variation between them. In order to understand timing of the high-grade metamorphism, we carried out SHRIMP U-Pb dating of zircons of the rocks. Zircons from the granulites and charnockitic gneisses are similar in structure and age. Zircon cores show magmatic zoning and have ages of 2507–2545 Ma. The ages are interpreted as the forming time of protolith of the granulites and charnockitic gneisses, indicating that a strong magmatism existed at that time in the Yinshan Block. The zircon mantles and rims show homogeneous structures and record a strong granulite facies metamorphism event around 2500 Ma, with a time interval between the metamorphism and magamatism being less than 50 Ma. These suggest that the Western Block was similar to the Eastern Block in tectono-thermal timing at the end of the Neoarchean.

关 键 词：Xi Ulanbulang high-grade metamorphic rocks ZIRCON SHRIMP U-Pb dating 

分 类 号：P588.3[天文地球—岩石学] P534.2[天文地球—地质学]