Geochemistry and Genesis of Con-cealed Granite in Huxingshan Tungsten-Beryllium Ore District,Northeast Hunan Province
The tungsten-beryllium polymetallic deposit at Huxingshan in northeastern Hunan Province is a large-scale quartz and greisen vein-belt type scheelite and beryl beryllium deposit.To investigate its genesis,material source and tectonic environment,we carried out detailed rock geochemical analyses on the newly discovered concealed granite bodies in the Huxingshan mining area,so to provide the theory support for the relationship between local magmatism and mineralization.The results show that the Huxingshan granite is a series of high-K calc-alkaline peraluminous granite rich in SiO2(71.86%～73.22%)and Al2O3(13.99%～14.55%),poor in TFe2O3(1.17%～1.63%)and MgO(0.28%～0.36%),and relatively poor in Na and rich in K(with the(K2O/Na2O)ration between 1.11 and 1.78).It is characterized by strong enrichment of light rare earth elements(LaN/YbN=9.29～21.9)and large ion lithophile elements(Rb,Ba,U,K),and relative depletion of heavy rare earth elements and high field strength elements(Nb,Ti,P).The geochemical characteristics show that Huxingshan granite is an S-type granite formed in an environment of lower pressure(<5 kbar)and an initial temperature of 727℃～785℃.It was formed by a high degree of fractional crystallization(plagio-clase,potash feldspar,apatite,etc.),and its crust source area is Lengjiaxi Group composed of mudstone and sandstone.Combined with the tectonic evolution history of the region,this study concluded that the low-an-gle subduction of the Paleo-Pacific Plate during the Yanshan Period caused strong deformation of the crust in the northeast Hunan region,and the subsequent weakening of regional stresses led to the detachment of the thickened lithosphere,in which case the crustal thinning or underplating of mantle source material had caused intense magmatism in the region,which resulted in the formation of the Huxingshan Granite.
concealed granite body in Huxingshan depositPetrogenesisMaterial sourceTectonic settingNortheast Hunan province
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