Geological Characteristics And Metallogenic Regularity Of The Gaowushan-Jiaokengwu Fluorite Deposit In The Bamianshan Orefield, Chanshan County, Zhejiang Province

The Gaowushan-Jiaokengwu fluorite mine of Bamianshan fluorite orefield, located inChangshan County, west of Zhejiang Province, is a new type of fluorite deposit which wasfirstly discovered recently. The occurring of fluorite orebodies and the characteristics of oresare unique.The deposit is in the southeastern flank of the Yanqian brachyanticline.Theorebodies mainly in the exocontact of Yanqian high F granite and the Cambrian carbonate rocksor interstratal tectonic zone of carbonate rocks occur in the bedded and lenticular form.Someorebodies are controlled by steep dipping fractures. Most of the fluorite ores are gray-dark gray,fine grained texture, massive structure, which look like the limestone. Ore minerals are mainlyquartz, fluorite, calcite, chlorite and sericite.The genesis of the deposit is disputed, while thesource of ore-forming materials is still contentious, which restricts the understanding of thenew type of fluorite deposit.This article describes the geological background of mineralization and the geologicalcharacteristics of the new type fluorite deposit; mainly studies on the tipical orebodies, such asNo.17orebody in Jiaokengwu ore domain and No.XIV, No. IV orebody in Gaowushan oredomain; and summarizes the fluid inclusion, rare earth, isotope geochemistry characteristics ofthe deposit.Combined with the latest achievements of exploration work, this article studies onthe temporal and spatial distribution of orebodies,ore-controlling factors,establishes a tentativemetallogenic model,and provides a guidance for the exploration work for the new type fluoritedeposit.Studies show that the Yanqian high F-granite is not of S-type, but A-type. The fluoriteorebodies are close to the granite in space and time.The granite not only offers ore-formingelement F, but also ore preserves the structure after magama invaded. The ore material (F) ismainly derived from the post-magma hydrothermal fluid, partly from the Cambrian carbonaterocks. The studies on REE and Sr isotope indicate that ore material (Ca) is mainly derived fromthe Cambrian carbonate rocks. Pure marblized limestone of Upper Cambrian Huayansiformation is best wall rock to form orebodies. The granite invaded in Yanqian brachy anticline,swallowed large amounts of carbonate rock,and formed the post-magmatic hydrothermal whichis rich in F, Ca materials,accompanied by large-scale alteration of marblization,hornfelsization and silicification.The ore-forming hydrothermal moved along the contact zone andinterformation fracture tectonic, exchanged material component with wall rock. Aftertemperature and pressure reduction, most of fluorite ores were forming by filling (accompaniedby replacement) in the contact zone and interformation structure, composed of layered orlentoid orebodies. Part of ore-forming hydrothermal fluids move along the fracture, with theinfiltration of atmospheric precipitation, forming veined orebodies.The Yanqian graniteemplacement is the most important control factors. The study of fluid inclusion shows that thehomogenization temperature of fluorite is120~255℃, which is a middle-1ow temperature.Fission-track dating of fluorite metallogenic age is115.70±10.99Ma, slightly later than theYanqian granite formation.Studies show that it is a mesothermal-epithermal deposit and controlled by rock masstogether with fracture and stratum. The ore is dominated by filling and accompanied byreplacement. Then a tentative metallogenic model is established, while direct and indirectprospecting indicators are put forward.