Skarn mineral charactersistics of Guanfang tungsten deposit and its geological significance,southeastern Yunnan Province,China
The Guanfang tungsten deposit,located in the Bozhushan tungsten polymetallic ore concentration area in Southeast Yunnan,is a newly discovered large scheelite deposit in recent years.The skarn mostly occurs in the in-terlayer fracture zones of the strata,in the form of layered,lenticular and vein.Most of the skarns do not contact with the granite body and form the distal skarn(the deep exploration revealed that a small amount occurs in the contact zone),and the skarn minerals are developed.In order to further identify the mineralogical and mineral-chemical characteristics of the skarn,reveal the formation environment of skarn,and explore the relationship be-tween skarn and mineralization types,the rock samples from near-end skarn(KT3)and distal-end skarn(KT5)were collected for comparison.A systematic mineralogical observation was undertaken,and analysis of garnet composition and In-Situ analysis of typical skarn minerals were carried out using EMPA and LA-ICP-MS,respec-tively.The study shows that the skarn of the Guanfang tungsten deposit belongs to the typical calcareous skarn,and the skarn minerals mainly include garnet,pyroxene,and vesuvianite,among which garnet is grossular-andra-dite series,pyroxene is diopside-hedenbergite series,and vesuvianite is the common vesuvianite.From the near-end skarn to the distal skarn,the main composition of garnet changes from grossular to andradite;the pyroxene transforms from almost purely diopside to the combination of diopside and hedenbergite.The characteristics of garnet and pyroxene indicate that the skarn of the deposit has changed from the reduced skarn type at near-end to the oxidized skarn type at distal end;the oxygen fugacity of KT5 is higher than that of KT3,the fluid metasoma-tism of KT5 and KT3 is mainly diffusion metasomatism.The characteristics of garnet and pyroxene end-member components and slightly higher Mn/Fe and Mg/Fe ratios comprehensively indicate that the mineralization type be-longs to Fe-Cu-Zn polymetallic mineralization type;The lower W content in vesuvianite can be used as a pros-pecting indicator for finding tungsten ore bodies.
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