Gochemical Characteristics And Genetic Analysis Of Mengman Gold Deposit, Yunan Province

Mengman gold deposits, whose tecnotic structures is located in southern Lan-cangjiang zone, its metallogenic province belongs to Xiao Nan Po-Xi Ding iron,gold polymetallic metallogenic region,which is one of the important goldpolymetallic enrichment region in our country.The ore bodys in Mengman gold deposit mainly include epimetmorphic rockseries of Manlai Formation, clastic rock of Huakaizuozu Formation and weatheringslope eluvium of quaternary period. Structure in the study area is mainly characterizedby fracture structure. the gold deposit mainly distributes along some big fractures inthe research area, which has obvious structural ore-controlling features. The metalminerals are simple, mainly including pyrite, arsenopyrite and submicroscopicinvisible gold; Deposit has a typical structure of hydrothermal type deposit, Orestructure are brecciated, banded, block-shaped, floated and boiled, and the textures areautomorphic-hypautomorphic granular, xenomorphic granular, microcrystal-coarsegrain and pseudomorphic ect. According to conclusion summarized and analyzed byfield observation and laboratory research, Deposit can be divided into threemetallogenic stages, including the diagenetic mineralization period, hydrothermalstage and supergene period, but the hydrothermal stage is the mainly metallogenicperiod.Ore-forming elements is characterized by the enrichment of Au-Ag-As-Sb, andthe belt affected by strong silicified has a huge metallogenetic potentiality.Thetemperature from fluid inclusions of quartz show that the metallogenic temperaturebelongs to the area of low temperature hydrothermal with the temperature from164℃to189℃and ore-forming fluid has a low salinity(1.53~2.64%NaCleqv); Electronmicroprobe analysis showed that Co/Ni value of pyrite is between0.27~3.33; Zirconfission track age show that Ore-forming age is l94±5~114±4Ma. the compositions offliud inclusions indicate that the ore-forming fluid is mainly from the atmosphericprecipitation. Silicon isotope geochemistry and silica cathode luminescence researchmethod have proved sueeessfully that mineralization silica is not provided bysurrounding rock but supplied by deep substance. S isotope from pyrite reflect thecharacteristics of deep sulfur. Au was transported probably in the comolex form ofAuH3SiO40, because of the abruptly change of physical and chemical conditions,thegold transporting in the complex of AuH3SiO40would be wholly deposited accompanied with the depositing of quantities of chalcedonies.According to the features of ore-controlling structure, the structure and texture ofmineral, and the types of alteration, Mengman gold deposit has the characteristics ofhydrothermal type gold deposit.