| The gold-antimony-lead-zinc-silver polymetallic metallogenic belt in southern Tibet is an important part of the Tethys Himalayan metallogenic domain.The Buzhu gold(antimony)deposit in the Kangma area is located at an advantageous metallogenic location where the SN-trending Lejin Kangsang faults zone crosses the EW-trending Rongbu-Gudui faults zone.Due to the low degree of research in the mining area,there has been no clear understanding of the characteristics of mineralization,ore controlling structure,fluid characteristics,and metallogenic age.Through the study of fluid inclusions in different veins in the area,it is found that the bulk inclusions in the Buzhu area are mainly pure liquid inclusions,liquid-rich inclusions,gas-rich inclusions,and a small amount of CO2 inclusions,showing obvious immiscibility.The average uniform temperature is 282.1?,and the average salinity is 7.71wt%.It is a medium-high temperature fluid with low salinity.The average density is 0.82g/cm3,the average pressure is23.6~114.9bar,and the average ore-forming depth is about 236~1149m.It is in line with the fluid characteristics of orogenic gold deposits as a whole.The K-Ar dating of fault gouge illite for the main ore-controlling faults in the study area found that the SN-and EW-trending faults were still active in the late Miocene,and it is inferred that the mineralization age does not exceed 7.2~ 8.5Ma.The north-south and east-west fault zones control the distribution of the main veins in the mining area,and the mineralization is mainly concentrated at the turning end of large-scale anticline folds.Three tectonic events are determined,which couple the three mineralization.The first stage of tectonic activity is the fold of S0 foliation under the N-S compressive stress,and the S1 replacement S0 foliation in some areas,accompanied by the mineralization of lodes and surrounding rocks along S0 foliation.The mineralization is mainly concentrated in the turning end of the fold,pyritization,and gold mineralization,and the mineralization alteration is mainly limonitization,chloritization,silicification,and carbonatization;The second stage of tectonic activity is N-S extensional action.Under the condition of late extensional stress mechanism,a large number of mixed veins of calcite and quartz intruded along S1 foliation,which was compressed to form reverse faults and plate cleavages in the early stage,and mineralized with fractured rock or wall rock in the fracture zone.The mineralized alteration mainly includes arsenopyrite,ferritization,pyritization,chloritization,silicification,etc;In the third stage,the tectonic activity was E-W extension,forming a N-S fracture zone.In the later stage,pyritization,gold,and antimony mineralization occurred in the contact area between the extensional vein,fault fracture zone,and the surrounding rock,with a higher grade but smaller scale.It is a late metallogenic event.Based on the study of fault structure,mineralization characteristics,fluid characteristics,and fault activity age in Buzhu area,this paper provides a certain basis for further prospecting in the Kangma Buzhu area... |
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