Geochronological and geochemical constraints on the petrogenesis of late Mesoproterozoic mafic and granitic rocks in the southwestern Yangtze Block

• 作者: Guichun Liu Jing Li Xin Qian Qinglai Feng Wei Wang Guangyan Chen Shaobin Hu
• 来源期刊: 地学前缘（英文版）
• 年，卷（期）: 2021,（1）
• 所属期刊栏目: Research Paper
• 页码范围: 39-52
• 页数: 14页
• 语种: 英文

摘要

Late Mesoproterozoic igneous rocks in the SW Yangtze Block are important for understanding the role of it in reconstruction of the Rodinia supercontinent.In the present study, we report new geochronological, geochemical,and Nd-Hf isotopic data for the Cuoke plagioclase amphibolites and granites in the SW Yangtze Block.Geochronological results show that the plagioclase amphibolites and granites have similar late Mesoproterozoic zircon U-Pb ages of 1168-1162 Ma, constituting a bimodal igneous assemblage.The plagioclase amphibolites have high and variable TiC2 contents(1.15-4.30 wt.％)and Mg#(34-66)values, similar to the tholeiitic series.They are characterized by enrichment in LREEs and LILEs, and have OIB-like affinities with positive Nb and Ta anomalies.The plagioclase amphibolites have positive whole-rock εNd(t)(+3.2 to+4.3)and zircon εHf(t)(+4.3 to+10.7)values, indicating that they were derived from an OIB-like asthenospheric mantle source.The granites belong to the reduced peralkaline A-type series and have negative εNd(t)value of-6.0 and εHf(t)values of-5.8 to-13.8, indicating a derivation from the partial melting of ancient mafic lower crust.In combination with the～1.05-1.02 Ga bimodal igneous assemblage in the SW Yangtze Block, we propose that the Cuoke 1168-1162 Ma igneous rocks were likely formed in a continental rift basin and argue against the existance of Grenvillian Orogen in the SW Yangtze Block during the late Mesoproterozoic.