Mature Archean continental crust in the Yangtze craton: Evidence from petrology, geochronology and geochemistry  

作　　者：WANG ZhengJiang WANG Jian DU QiuDing DENG Qi YANG Fei WU Hao 

机构地区：[1]Chengdu Institute of Geology and Mineral Resources,Ministry of Land and Resources of the People's Republic of China [2]Graduate Faculty of Chinese Academy of Geological Sciences [3]Graduate Faculty of Shandong University of Science and Technology

出　　处：《Chinese Science Bulletin》2013年第19期2360-2369,共10页

基　　金：supported by the National Natural Science Foundation of China (41030315 and 41072088);the Chinese Geological Survey (1212011121111 and 1212011220750)

摘　　要：Previous studies have shown that the Archean basement is widely distributed throughout the Yangtze craton. To date, however, Archean basement terrains have not been found, except for a few Kongling high-grade metamorphic terrains in the Huangling dome that have been confirmed to be of Archean age. To further understand the basement component and crustal evolution of the Yangtze craton, we carried out a petrological, geochronological and geochemical study of the Jinshan K-feldspar granite emplaced within the Yangpo Group, located in Huji Town, Zhongxiang City, Hubei Province. Results indicate that the zircon SHRIMP U-Pb age of the Jinshan granite is 2655±9 Ma, placing it within the middle Neoarchean. Chemically, this pluton yields abundant silica and alkalis and is depleted in Ca, Mg and Ti. Furthermore, it is enriched in Rb, Th, Ga, Y and Zr, depleted in Sr, Ba, Nb and Ta, and especially lacking in Eu. High ratios of FeO*/MgO (32.0 to 58.7) and 104 ×Ga/Al (3.19 to 3.41) were also found. The pluton exhibits characteristics typical of A-type granites with crustal source magmas. Moreover, the meta-sedimentary rock association of the Yangpo Group, into which the pluton intruded, clearly shows relatively stable depositional environments of a shallow shelf sequence. Therefore, before the middle Neoarchean, the Yangtze craton contained mature continental crust. This breakthrough discovery opens a new window on the study of the formation and evolution of the Yangtze craton basement.Previous studies have shown that the Archean basement is widely distributed throughout the Yangtze craton. To date, however, Archean basement terrains have not been found, except for a few Kongling high-grade metamorphic terrains in the Huangling dome that have been confirmed to be of Archean age. To further understand the basement component and crustal evolution of the Yangtze craton, we carried out a petrological, geochronological and geochemical study of the Jinshan K-feldspar granite emplaced within the Yangpo Group, located in Huji Town, Zhongxiang City, Hubei Province. Results indicate that the zircon SHRIMP U-Pb age of the Jinshan granite is 2655±9 Ma, placing it within the middle Neoarchean. Chemically, this pluton yields abundant silica and alkalis and is depleted in Ca, Mg and Ti. Furthermore, it is enriched in Rb, Th, Ga, Y and Zr, depleted in Sr, Ba, Nb and Ta, and especially lacking in Eu. High ratios of FeO＊/MgO （32.0 to 58.7） and 104 ×Ga/Al （3.19 to 3.41） were also found. The pluton exhibits characteristics typical of A-type granites with crustal source magmas. Moreover, the meta-sedimentary rock association of the Yangpo Group, into which the pluton intruded, clearly shows relatively stable depositional environments of a shallow shelf sequence. Therefore, before the middle Neoarchean, the Yangtze craton contained mature continental crust. This breakthrough discovery opens a new window on the study of the formation and evolution of the Yangtze craton basement.

关 键 词：地球化学证据 扬子克拉通 中太古代 大陆地壳 SHRIMP锆石U-PB年龄 岩石学 年代学 成熟 

分 类 号：P534.2[天文地球—古生物学与地层学]