Late Mesoarchean crust growth event： evidence from the ca. 2.8 Ga granodioritic gneisses of the Xiaoqinling area, southern North China Craton  

作　　者：Xiaoliang Jia Xiyan Zhu Mingguo Zhai Yan Zhao Hong Zhang Jialin Wu Tao Liu 

机构地区：[1]State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China [2]Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029,China

出　　处：《Science Bulletin》2016年第12期974-990,共17页科学通报（英文版）

基　　金：supported by China Ministry of Science and Technology ("973" Project) (2012CB4166006);the National Natural Science Foundation of China (41210003)

摘　　要：Recently, more attention has been paid to Precambrian magma events and crustal growth of the North China Craton(NCC), accompanying with controversy in activity stages and dynamic mechanism. In this study, we report the Archean(2802 ± 13 Ma) granodioritic gneisses in the Taihua Complex from the Xiaoqinling area, located in the southern margin of the NCC. The zircon Lu–Hf isotope analysis of the rocks showed ^(176)Hf/^(177)Hf ratios of0.280977–0.281228, corresponding to ε_(Hf)(t) values ranging from-3.5 to +6.6, and two–stage Hf model ages varying from 2836 to 3409 Ma. It was confirmed that late Mesoarchean(2.9–2.8 Ga) juvenile crust made contribution to the source material of these ca. 2.8 Ga granodioritic gneisses in the Xiaoqinling area. The whole rock geochemical data indicate that the granodioritic gneisses are high-K calc-alkaline series, probably generated at relatively high pressure and temperature, and formed under the continental arc setting. Statistically, we conclude that the magmatic activities during 2.9–2.7 Ga may represent the most intense crustal growth events in the NCC and these Archean rocks at different locations in southern NCC underwent a similar crustal evolution history.Recently, more attention has been paid to Precambrian magma events and crustal growth of the North China Craton （NCC）, accompanying with controversy in activity stages and dynamic mechanism. In this study, we report the Archean （2802 ± 13 Ma） granodioritic gneisses in the Taihua Complex from the Xiaoqinling area, located in the southern margin of the NCC. The zircon Lu-Hf isotope analysis of the rocks showed 176Hf/177Hf ratios of 0.280977-0.281228, corresponding to εHf（t） values ranging from -3.5 to ＋6.6, and two-stage Hf model ages varying from 2836 to 3409 Ma. It was confirmed that late Mesoarchean （2.9-2.8 Ga） juvenile crust made contribution to the source material of these ca. 2.8 Ga granodioritic gneisses in the Xiaoqinling area. The whole rock geochemical data indicate that the granodioritic gneisses are high-K calc-alkaline series, probably generated at relatively high pressure and temperature, and formed under the continental arc setting. Statistically, we conclude that the magmatic activities during 2.9-2.7 Ga may represent the most intense crustal growth events in the NCC and these Archean rocks at different locations in southern NCC underwent a similar crustal evolution history.

关 键 词：2.8 Ga Granodioritic gneisses ZirconU-Pb-Hf isotopic composition Archean crustalgrowth Taihua Complex North China Craton 

分 类 号：P588.345[天文地球—岩石学]