Genesis Of Gold And Lead-Zinc Deposits In Fengxian Area,South Qinling

A large number of large and medium-sized Pb-Zn deposits have been found in the Devonian strata of the Fengtai Basin in the South Qinling Mountains(such as Bafangshan-Erlihe,Yindongshan,Qiandongshan,Yinmushi,Yindongliang,etc.)and large-super large gold mines(such as Shuangwang and Baguamiao).According to previous studies,the gold deposits and Pb-Zn deposits in the Fengtai Basin have a showing obvious co-generation relationship in the ore-forming strata,mineralization age,material source and mineralization process.However,due to lack of the detailed data support and the establishment of the systematic deposit model have,which led to insufficient understanding of the genetic relationship between gold and Pb-Zn mines.The lag of this research not only hinders the development and improvement of the theory of “Qinling-style” deposits,but also directly affects In-depth development of metallogenic prediction and prospecting exploration work in Qinling District.Based on the Paleozoic-Mesozoic metallogenic dynamics background and metallogenic conditions of the Southern Qinling Mountains,and detailed field observations,petrography,isotope dating,LA-ICP-MS in situ isotope source tracing,LA-ICP-MS in-situ micro-component analysis and fluid inclusion research,this research studied the genesis of the Baguamiao gold deposit and the Erlihe-Yindongshan Pb-Zn deposit that have closely relationship in time and space in Fengxian area of South Qinling,and lately established a unified and unified metallogenic model for the genesis of thses deposits acrroding to related research at abroad.In the course of the research,the results and understanding of this paper are as follows:The petrographic characteristics,sulfur isotope characteristics and trace element characteristics of strawberry-like pyrite in the sedimentary facies of the Baguamiao gold deposit in the study are in line with the first stage mineralization model of SEDEX mineralization,while The petrographic characteristics,sulfur isotope characteristics and trace element characteristics of pyrite in the diagenetic period of the Erlihe-Yindongshan Pb-Zn deposits in ore-bearing surrounding rock are in line with the second stage of SEDEX mineralization.Because the formation of the surroundingrock of the Baguamiao gold deposit(the Upper Devonian Xinghongpu Formation phyllite)is significantly later than that of the Erlihe-Yindongshan Pb-Zn ore-bearing surrounding rock(the Middle Devonian Gudaoling Formation limestone),indicating that the formation of the two different horizons-the formation of pyrite during the diagenesis is the result of multiple-stage(at least two)jet deposition events,due to the differences in jet deposition mineralization at different stages,This led to differences in the enrichment of gold,lead and zinc at different levels.In this paper,it is believed that the late Devonian jet deposition only pre-concentrates gold,lead and zinc elements in the stratum without forming a true ore body.The true ore body is formed in the process of the Late Triassic orogeny.The Late Triassic ore-forming dynamics of the Baguamiao gold deposit and the Erlihe-Yindongshan Pb-Zn deposit in the study area are in the post-Qinling orogenic collision stage and have undergone the orogenic deformation of the early extrusion process(209~220Ma).To the late-stretching(~209Ma)tectonic-fluid metallogenic process: the early I and II mineralization stages of the Baguamiao gold deposit were mainly controlled by the NWW tough-brittle shear zone,and the Erlihe-Yindongshan Pb-Zn mine was early.The ore stage is mainly controlled by the NWW tectonic fracture zone and the physicochemical zone;while the late III and IV mineralization stages of the Baguamiao gold deposit are controlled by NE-trending fissures and shear joints,and the second and third metallogenic stages of the Erlihe lead-zinc deposit are ontrolled by NE Fracture.In terms of ore-forming fluid properties and material sources,for the early metamorphism and warming stage,the early ore-forming fluids of the Baguamiao gold deposit(I and II mineralization stages)are mixed fluids of formation metamorphic fluids and deep magmatic hydrothermal fluids.The mixing of deep magma sulfur and formation sulfur,metamorphism re-activates and enriches a series of elements such as S and Au,Cu,Pb and Zn in the formation,but does not rule out part of the gold and ore-forming materials from deep magmatic hydrothermal activity;The early ore-forming fluids of the Erlihe-Yindongshan Pb-Zn deposit(I mineralization stage)are dominated by stratigraphic metamorphic fluids,and a small amount of magmatic fluid is added.The sulfur source is a mixed source of formation sulfur and magma sulfur,and Yindongshan mining area.The source of lead in the ore I-stage is likely to be the mixed effect of the Xiba rock mass magmatic hydrothermal fluid,the ancientbasement and the ore-bearing surrounding rock.For the late warming and decompression mineralization stage,the fluids of the Baguamiao gold deposit III mineralization stage are derived from magmatic hydrothermal fluid,ancient basement metamorphic fluid and Gudolinling formation,while the IV mineralization stage fluid is mainly derived from magmatic hydrothermal fluid and surrounding rock.In the stratum of the Xinghongpu Formation,the source of sulfur in the III and IV ore-forming stages is from the magma sulfur and the Lower Gudolinling Formation.The lead source in the III metallogenic stage comes from the mixing of the Xiba rock magmatic hydrothermal fluid,the ancient basement and the Gudaoling Formation.The lead in the ore-forming stage is mainly derived from the ore-bearing surrounding rock strata(Xinghongpu Formation);the later-stage ore-forming fluid of the Erlihe lead-zinc deposit(II,III metallogenic stage)is dominated by magmatic hydrothermal fluid,while in the III There are a small amount of formation fluids in the ore stage,and the sulfur source in the II and III mineralization stages is mainly magmatic sulfur.The source of lead in the II mineralization stage is likely to be the Xiba rock mass magmatic hydrothermal fluid,the ancient basement and the ore-bearing surrounding rock.The mix of effects.In terms of gold deposit occurrence and enrichment and sedimentation mechanism,the gold in the ore-forming stage of the Baguamiao gold deposit II mainly exists in the gold and fissure gold,and a small amount exists in the pyrite crystal lattice,while the gold in the IV metallogenic stage is mainly Both lattice gold and gold are present in pyrite.The main enrichment and sedimentation mechanism of gold in the hydrothermal period I and II of the Baguamiao gold deposit is the water-rock reaction.The main enrichment and sedimentation mechanism of gold in the III mineralization stage is the water-rock reaction and the decrease of total sulfur activity.The main enrichment and sedimentation mechanism of gold in the ore-forming stage is the boiling effect caused by temperature drop and pressure drop,water-rock reaction,oxygen fugacity reduction,total sulfur activity decrease and pH increase.The main enrichment and sedimentation mechanism of gold in the I and II mineralization stages of the Erlihe-Yindongshan lead-zinc mine is the decrease of total sulfur activity.The main enrichment and precipitation mechanism of gold in the III metallogenic stage is the boiling effect caused by temperature drop and pressure drop.Water-rock reaction,total sulfur activity decreased,and pH increased.In terms of the state of lead-zinc deposits and the mechanism of enrichment and sedimentation,the lead-zinc ore body mainly exists in the metallogenic stage of the Baguamiao gold deposit.The migration mode of lead and zinc mainly migrates in the form of chloride and is sulfide(galena And sphalerite form precipitation.The main sedimentation mechanism of lead-zinc deposits in the metallogenic stage of the Baguamiao gold deposit is fluid mixing and water-rock reaction.The main enrichment and sedimentation mechanism of the I and II mineralization stages of the Erlihe-Yindongshan lead-zinc mine is fluid mixing,while the main enrichment and sedimentation mechanism of the III metallogenic stage is the boiling effect caused by temperature drop and pressure drop,fluid mixing and Water rock reaction.In terms of the genetic relationship between gold deposits and lead-zinc deposits,this paper considers the limitations and differences of the early Late Devonian jet sedimentary mineralization,leading to the gold preconcentration in the upper level of the Devonian Xinghongpu Formation.The lead-zinc deposit is mainly produced in the Lower Devonian Gudolinling Formation,and the metamorphic deformation of the Late Triassic plays a role in reactivation and enrichment of gold,lead and zinc in the study area,and forms a series of ore-bearing ore.And the ore-constructing structure,the deep magmatic hydrothermal fluid and the metamorphic fluid are uplifted along the ore-conducting structure,which not only activates and extracts the gold,lead and zinc elements of the original formation,but more importantly,the S and Au,Pb and Zn in the lower Gudolinling Formation.The ore-forming materials such as Cu are brought into the relatively rich gold stratum of the upper Xinghongpu Formation,which not only enlarges the metallogenic scale of lead and zinc,but also delays the precipitation of gold,which leads to the enrichment of gold in the later fluids,thus expanding The scale of the gold mine.Therefore,the development of the Late Triassic magmatic hydrothermal fluid is very important.Its nature and scale directly determine the distribution and metallogenic scale of gold,lead and zinc in the study area,and even determine the distribution and formation of gold,lead and zinc in the entire Fengtai Basin.Mine scale.