Mica Geochemistry Of The Xianghualing Tin-Polymetallic Deposit In Southern Hunan And Its Indicative Significance For Mineralization

The the Nanling Mountain metallogenic belt is an important gathering place of nonferrous metals and rare metals resources in China.The Xianghualing deposit in southern Hunan,located in the middle of the metallogenic belt,is a typical representative of tin polymetallic deposits.On the basis of detailed petrological and mineralogical studies of the Xianghualing ore-forming rock mass(Laiziling rock mass),hydrothermal mineral assemblage and altered striped rock,this paper mainly carries out the analysis of major elements of magmatic mica and single mineral of hydrothermal mica at different stages by electron probe microanalysis(EPMA)and the analysis of trace elements by laser denudation iso-iron mass spectrometry(LA-ICP-MS),aiming to identify the type and composition change characteristics of mica in the process of magmatic and hydrothermal evolution,Furthermore,the migration and enrichment of ore-forming elements in the magma-hydrothermal process are discussed.The Laiziling pluton is characterized by vertical zoning,which is mainly composed of the lower monzogranite and the more evolved upper albite granite,and is a set of high-silicon,alkali-rich quasi-aluminous and peraluminous granite;The trace elements are enriched in Rb,Th,U,Nb,Ta,and depleted in Ba and Sr.The rare earth elements have weak four-group effect and obvious europium negative anomaly.The mica in monzogranite and albite granite is zinnwaldite,representing the type of mica in the magma stage.EPMA surface analysis shows the trace of hydrothermal metasomatism,and some mica slices develop hydrothermal growth or metasomatic zoning.Mineralized greisen and Unidirectional Solidification Texture(UST)occur in albite granite,where metal sulfides are developed,representing the early stage of hydrothermal fluid.Its mica type is also dominated by zinnwaldite,and the mica edge also shows zonal structure.From monzogranite to albite granite and then to the early stage of hydrothermal solution,the content of ferrolepidolite Si and Al slightly increased,the content of Fe decreased,the content of Li,F,Mn,Rb,Zn increased,and the content of Nb,Ta and Sn first increased and then decreased,indicating that most ore-forming elements gradually enriched from the process of magmatic evolution to the early stage of hydrothermal solution,while Nb Ta and Sn are enriched in the late magmatic stage and saturated with Qitianling ore,niobium tantalum uranium ore,and cassiterite..Compared with the core,the content of Si and Al in the edge of banded mica is significantly higher,and the content of Fe,Mn,Rb,F,Li,Nb,Ta,W,Zn is significantly lower,indicating that the marginal banded mica is formed after the precipitation of ore-forming elements.Altered striped rocks occur in the contact zone between the Laiziling rock body and the surrounding rock of carbonate rocks,which can be divided into magnetite striped rocks and phlogopite fluoborite striped rocks.Their mica types belong to the aluminum rich phlogopite phlogopite series.From magnetite striped rock to phlogopite fluoborite striped rock,the content of Mg and Sn in mica gradually increases,and the content of Fe and F gradually decreases,indicating the full replacement of hydrothermal solution and wall rock and the gradual precipitation of magnetite and fluorite.With the decrease of F content,Sn precipitates as cassiterite saturation in the late hydrothermal stage.