The Qianlishan Granite Genetically Related To The Zoning Of Shizhuyuan Ore-Field

Shizhuyuan ore-filed with numerous ore deposits of various ore-forming elements is located in the Nanling Range.Three metallogenic zones,spanning about 8 km,from the Qianlishan granites occurred successively southward: W-Sn-Mo-Bi zone(center),Pb-Zn zone(middle part),Hg-Sb zone(outmost).The ore-forming temperature gradually decreases from the center zone to the outmost zone.There were few records on the timespan of magmatic hydrothermal oreforming system in the Shizhuyuan ore-field,which probably plays an important role in the forming of supergiant deposit.Here,we conducted a set of dating with various close temperature,geochemical content of pyrite and Pb isotope of sulfides(pyrite,galena and Kfeldspar)analysis and metallogenic efficiency of ore-forming elements estimation,in order to reveal the cooling history of the Qianlishan granites,to determine that whether all the zones result from the same magmatic-hydrothermal system and quantitively compare the ore-forming potential of elements.1.The Qianlishan granites,a granite complex with multiple phases,supplied metal and heat for the magmatic-hydrothermal system.Containing high content of heat producing elements(U,Th,K),it belongs to high heat producing granite(HHP)with average volume heat of 9.7 ?W/m3.Due to its high radioactive heat supply and high concentration of F,the crystallization of the Qianlishan granites were apparently protracted,as well as the cooling of the corresponding magmatic-hydrothermal system.Based on the thermal-chronological study,the duration of the cooling history was constrained between 40-69 Ma.2.On the basis of filed-work,petrological research,geochronology and geochemical analysis,the Qianlishan granites were classified into four phases:(1)porphyritic biotite granite with oxygen fugacity of IW-MH;(2)porphyritic biotite granite with oxygen fugacity of FMQMH;(3)equigranular biotite granite;(4)granite porphyry.3.The content of pyrite varied successively among 3 mineralizing zones(center: W-Sn-MoBi;middle: Pb-Zn;out: Hg-Sb).Bi and Ag contents gradually decrease from the center zone to the outmost zone while Mn and Sb concentrations increase.Similarly,Pb isotope mimic the gradual variation of pyrite geochemical content,indicating the unity of the Shizhuyuan magmatic-hydrothermal system.4.According to the metallogenic efficiency of elements in the Shizhuyuan ore-field,ranking elements as follows: W>Sn>Mo>F>Cu>Pb>Zn>Hg>Ag.It is consistent with their ore reserve;i.e.higher potential corresponds to large reserve.Therefore,metallogenic efficiency of elements indicates their ore-forming potentials.Giver a superimposed map of geochemical anomalies of various elements,the regions overlain by geochemical anomalies of several elements with the highest weighted metallogenic efficiencies are favorable locations for polymetallic deposits and thus favorable candidates for further exploration.Summarily,due to the high radioactive heat and ore-forming material supplied by the Qianlishan granites,the magmatic-hydrothermal system in the Shizhuyuan ore-field lasted for ca.70 Ma.It probably plays a key role in the formation of the supergiant Shizhuyuan W-Sn-Mo-Bi deposit and the whole mineralizing zoning.