The Genesis Of The Baiyangping Lead-Zinc-Copper-Silver Polymetallic Vein Deposit In Western Yunnan

As the continental orogenic belt formed by Indian-Asia plate collision,the Tibetan plateau is an ideal area for studying the metallogenesis of continent-continent collision.The Sanjiang region in the eastern-northern margin of the Tibetan plateau has many sediment hosted base metal deposits,which is an important type among them.By studying these deposits,it is benefitial for us to make clear of the coupling relationship between orogenetic process and region metallogen,to develop the metallogenic theory of sediment-hosted base metal deposits,to enrich and improve the metallogenic theory system of continental collision.The predecessor did much research work,and they got some cognition.But there are still many metallogenic problems to solve,for examples:the resource of ore-forming fluid,mineral resource,mineralogenetic epoch and genetic model,and it is necessary to compare to other similary deposits in the world,in order to find out their similarities and differences.Lanping basin is located in the middle-south of the Sanjiang area,clamping between Lancang River suture and Jinshajiang-Ailaoshan suture.In Lanping basin,the deposits can be devide into two zones:one is a NS striking Cu ore belt at western margin,controlled by the NS striking thrust fracture,and the other is a NNE striking Pb-Zn-(Ag-Sr)ore belt at eastern margin,controlled by the Huachang mountain thrust fracture.The article select Baiyangping,Zhatang and Liangchaqing three ore blocks as the research object,and we call it Baiyangping Pb-Zn-Cu-Ag polymetal vein deposit or Baiyangping vein deposit.The wall-rock are mainly hoary sandstone of Cretaceous Jingxing formation,and the deposit is controlled by extension fractures which move towards NE and NWW.The ?13Cv-PDB of carbonate minerals is between-0.5?-5.2‰ average-2.3‰,which indicates the C was derived from mantle emanation and dissolution of carbonate rocks.The ?18Ov-SMOW is mainly between 13.6?21.3‰,average-17.4‰,the ore-forming fluid was mainly derived from basin fluid.The ?34Sv-CDT is between-26.8‰?9.3‰,mainly 4.0‰?8.0‰,which indicates the sulfur was derived from hydatogenic rock sulphate by thermal reducing action(TSR),and biological reducing action(BSR)may also have some contribution to the early stage of mineralization.From the features of REEs,we can know the cal cites of Baiyangping,Zhatang and Liangchaqing three ore blocks are homology,but the calcites of Liangchaqing formed latestly.What is more,the study area was in reducing environment during the main mineralization epoches.According to the study and analyse of the Baiyangping vein deposit,combining with the research result of predecessors,we can know that:The Pb-Zn mineralization happened at early Miocene,and the Cu mineralization happened at Eocene,earlier than the Pb-Zn mineralization;The Baiyangping,Zhatang and Liangchaqing three ore blocks were belong to the same metallogenic system with two stage,the Cu mineralization and the Pb-Zn mineralization.