Geochronology,Hf Isotope,Geochemistry and Petrogenesis of the Baimashan Granitic Complex in the Central Hunan Province
Liu Xianhong
Liu Deliang
Lou Yuanlin
Pan Siyuan
Xiao Tao
Liu Xiaojian
Zhang Zhenli
Abstract：In order to thoroughly investigate the tectonic evolution,magmatic activities,and their effects on mineral resource formation during the Early Paleozoic and Early Mesozoic eras in South China,systematic field investigations were conducted in the Baimashan complex located in the central Hunan region.Additionally,zircon geochronological analysis,Hf isotope studies,and geochemical assessments were performed.Zircon LA-ICP-MS U-Pb dating illustrates that the weighted mean ages of the Shuiche mylonitized granite and the Longtan-Xiaoshajiang biotite granodiorite within the Baimashan granitic complex are 409±2 Ma and 211±1 Ma,respectively.These ages correspond to the Late Caledonian and Indosinian magmatic events,respectively.The Caledonian mylonitized granite is characterized by high silica,high alkali and strong peraluminosity,accompanied by a pronounced negative Eu anomaly.This,combined with its enriched Hf isotopic composition[εHf(t)=-13.4 to-5.4],indicates that it is likely a S-type granite formed through partial melting of Paleoproterozoic sedimentary rocks.In contrast,the Indosinian biotite granodiorite exhibits low-silica,high-alkalinity and aluminous,displaying a moderate Eu-negative anomaly with a relatively negative εHf(t)value(-10.3 to-7.4)and an ancient modal age(1.71 to 1.89 Ga).This granodiorite can be categorised as a Paleoproterozoic meta-igneous mixing of partially metasomatised sedimentary rocks remelted to form Ⅰ type granites.The Caledonian and Indosinian superunits of the Baimashan complex may have been formed in a tectonic environment of intra-plate orogeny.There is a strong genetic connection between the Caledonian rocks and the regional W mineralization,as well as between the Indosinian granitic rocks and the Au-Sb-W mineralization in the area.These rocks exhibit significant potential for Au-Sb-W mineralization.
Keywords：Baimashan granitic complexgeochronologyHf isotopesgeochemistryPetrogenesis
Publication Date：2025-02-14
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：12( 609-620 )