Geochronological and Geochemical Constraints on the Petrogenesis of Early Paleoproterozoic(2.40–2.32 Ga) Nb-Enriched Mafic Rocks in Southwestern Yangtze Block and Its Tectonic Implications  

作　　者：Guichun Liu Xin Qian Jing Li Jian-Wei Zi Tianyu Zhao Qinglai Feng Guangyan Chen Shaobin Hu 

机构地区：[1]Guangdong Provincial Key Lab of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-Sen University,Guangzhou 510275,China [2]Yunnan Institute of Geological Survey,Kunming 650216,China [3]School of Resource Environment and Earth Sciences,Yunnan University,Kunming 650091,China [4]Southern Marine Science and Engineering Guangdong Laboratory,Zhuhai 519082,China [5]State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China

出　　处：《Journal of Earth Science》2020年第1期35-52,共18页地球科学学刊（英文版）

基　　金：jointly supported by the National Natural Science Foundation of China(Nos.U1701641,41702230);the District Summary and Service Product Develop of Yunnan Region Geologic Survey(No.121201102000150012-02);Yunnan Province Geological Survey Foundation(No.2013HA001);Natural Science Foundation of Guangdong Province(No.2018B030312007)

摘　　要：Recent geological survey has identified the Early Paleoproterozoic meta-mafic intrusions in the southwestern Yangtze Block.We present geochronological,whole-rock geochemical and Nd isotopic data for these meta-mafic rocks to better address the tectonic evolution of the Yangtze Block during the Early Paleoproterozoic Period.Geochronological data show that the meta-mafic rocks have zircon ages of 2 395-2 316 Ma.They have high TiO_2 contents of 1.40 wt.%-3.66 wt.% and Nb concentrations of 13.7 ppm-45.5 ppm,thus aregrouped as Nb-enriched mafic rocks.These mafic rocks are characterized by tholeiitic compositions with enrichment of LREEs and LILEs,and can be divided into two groups.Group 1 samples display E-MORB-like geochemical characteristics.Group 2 samples have positive ENd(t) values of 4.0-5.0.Geochemical data indicate that all meta-mafic rocks were likely derived from a depleted asthenospheric mantle.REE modeling indicates lower degree of partial melting for Group 2 samples(3%-10%) relative to Group 1 samples(15%-20%).Taking into account contemporaneous post-collisional granitoids in southwestern Yangtze Block,we propose that these meta-mafic rocks were formed in a post-collisional extension setting.These meta-mafic rocks can be compared with those in Africa,South America and Europe,and might be linked with the Arrowsmith orogenic belt.Recent geological survey has identified the Early Paleoproterozoic meta-mafic intrusions in the southwestern Yangtze Block.We present geochronological,whole-rock geochemical and Nd isotopic data for these meta-mafic rocks to better address the tectonic evolution of the Yangtze Block during the Early Paleoproterozoic Period.Geochronological data show that the meta-mafic rocks have zircon ages of 2 395-2 316 Ma.They have high TiO2 contents of 1.40 wt.%-3.66 wt.% and Nb concentrations of 13.7 ppm-45.5 ppm,thus aregrouped as Nb-enriched mafic rocks.These mafic rocks are characterized by tholeiitic compositions with enrichment of LREEs and LILEs,and can be divided into two groups.Group 1 samples display E-MORB-like geochemical characteristics.Group 2 samples have positive ENd（t） values of 4.0-5.0.Geochemical data indicate that all meta-mafic rocks were likely derived from a depleted asthenospheric mantle.REE modeling indicates lower degree of partial melting for Group 2 samples（3%-10%） relative to Group 1 samples（15%-20%）.Taking into account contemporaneous post-collisional granitoids in southwestern Yangtze Block,we propose that these meta-mafic rocks were formed in a post-collisional extension setting.These meta-mafic rocks can be compared with those in Africa,South America and Europe,and might be linked with the Arrowsmith orogenic belt.

关 键 词：zircon dating geochemistry Early Paleoproterozoic Nb-enriched rocks Yangtze Block 

分 类 号：P534.3[天文地球—古生物学与地层学] P59[天文地球—地质学]