Mineralogical Characteristics Of Chlorite From The Shimensi W-Cu-Mo Deposit In The Dahutang Mining Area Of Jiangxi Province And Deposit Cause

The Dahutang mining area in Jiangxi Province is a world-class super-large tungsten deposit discovered in the Jiangnan orogenic belt from recent years.It is accompanied by abundant copper and molybdenum mine and rich in mineral resources.Among them,the WO₃ metal in the Shimensi deposit of the northern area is huge?74.255×10⁴t?,and the Yanshanian magmatism is extremely frequent,forming the porphyritic biotite granite?148.3Ma?,the fine-grained biotite granite?144.7Ma?and the granite porphyry?143.1Ma?.The chalcopyrite in the mother rock is closely related to the chlorite and the main ore body of the Shimensi deposit is mainly veinlet-disseminated in the biotite granodiorite.The predecessors have done a lot of research on the tungsten and copper mineralization in the Shimensi deposit.It is believed that the scheelite mineralization is related to the porphyritic biotite granite.The mineralization temperature is 330?,but it is not clear whether the copper mineralization exists in multiple phases.Therefore,we focuses on the chlorite associated with chalcopy mineralization in the Shimensi W-Cu-Mo deposit,and conducts systematic mineralogical studies to reveal the multi-phase copper mineralization and the genesis of the deposit.The third-stage ore-forming mother rocks are characterized by high temperature?741.47??904.66??and low oxygen fugacity?-21.77?-12.96?.The chlorites in the mother rock and surrounding rock are all iron-rich species.The biotite granodiorite has grown the hydrothermal crystalline chlorite,the FeO content is low?average 29.59%?,the average SiO₂ content is 26.60%,the formation temperature changes from 218.33? to 227.59?,and the oxygen fugacity is -50.16 to -46.67.The three periods of chlorite are produced from the early to the late in the porphyritic biomite granite:the hydrothermal crystalline chlorite,the hydrothermal metamorphic chlorite and the hydrothermal filled chlorite,the FeO content decreases in turn?36.67%,31.46%,28.5%?,the SiO₂ content increases in turn?23.92%,25.95%,27.87%?,the formation temperature changes from 216.05? to 263.75?,and the oxygen fugacity is -53.18 to-42.59.The fine-grained biotite granite has grown the hydrothermal metamorphic chlorite and the hydrothermal filled chlorite,the FeO content is respectively 32.26% and 28.78%,the SiO₂ content is respectively 25.59%,28.12%,the formation temperature changes from 229.83? to 243.33?,and the oxygen fugacity is -55.17 to-46.13.There is only the hydrothermal metamorphic chlorite in the granite porphyry,the FeO content has an abnormally high value?average 38.49%?,the amount of chlorite is small and the alteration is serious,and the mineral chemical composition is lost.Comprehensive studies have shown that the large-scale tungsten mineralization in the Shimensi deposit is mainly formed in the fluid-rock interaction stage in the porphyritic biomite granite,while the chalcopy mineralization is at least three stages including the hydrothermal crystalline chlorite stage in the porphyritic biotite granite,the hydrothermal filled chlorite stage in the fine-grained biotite granite and the hydrothermal metamorphic chlorite stage in the biotite granite porphyry.The fluid of the medium-low temperature?229??264??and the low oxygen fugacity?-56?-42?promote the enrichment and precipitation of ore-forming element Cu.