The Characteristics And The Genesis Of The Wangxianling Granitic Intrusive,South Hunan Province

Located about10km at the southeast of Chenzhou City in Hunan Province,Wangxianling granite intrusion is in the middle of the Nanling tungsten-tinpolymetallic metallogenic area of South China Block. On the basis of field geologicalsurvey, combined with mineralogy, petrology, geochemistry and isotope research, thispaper discussed the age and diagenetic stages, the mineralogical characteristics,magma source and the evolution characteristics of Wangxianling granite intrusion.And by comparing the characteristics of contemporary similar granitoids in SouthChina, we discussed the source region, tectonic setting and geodynamic evolution ofthe same period granitoids in South China Block. Achieving the understanding asfollows:(1)The Wangxianling intrusion in south Hunan province consists of twogranitoids, the main intrusion body tourmaline biotite granites, greisenizationtourmaline granites and the interior stock biotite monzonite granites, in which theourmaline biotite granites and greisenization tourmaline granites are homologousgranites in the same period.(2)The LA-MC-ICP-MS zircon U-Pb dating shows that the tourmaline biotitegranites formed in the Indosinian (235.0±1.3Ma) while the biotite monzonite granitesformed in Yanshanian(155.9±1.0Ma), indicating that Wangxianling intrusion is theproduct of two times magmatic activities.(3) Both the muscovite in tourmaline biotite granites and biotite monzonitegranites are mainly secondary muscovite, and both the tourmaline in tourmalinebiotite granites and greisen tourmaline granites are schorl.(4) The Indosinian tourmaline biotite granites are strongly peraluminous graniteswith S-type granite characteristics and are originated from the Paleo-andMesoproterozoic crustal remelting while the Yanshanian biotite monzonite granitesare peraluminous granites and are originated from the Paleo-and Mesoproterozoiccrustal remelting. Both the Indosinian tourmaline biotite granites and Yanshanianbiotite monzonite granites have experienced fractional crystallization during theformation.(5) The Yanshanian granites are mainly derived from partial melting of lowercrustal material with some of the mantle materials involved while the Indosiniangranites involving more mantle materials than theYanshanian granites.(6)We infer that the Indosinian period granitic magma formed in intermittentlithosphere extensional environment during the collision compression while theYanshanian period granitic magma formed in the extensional environment of the backarc continental margin.