| TianZhu-JinPing gold field is the one of the enrichment region of the gold deposits in Guizhou province,this area is a famous and long-term gold producer.The gold deposits in the study area are dense,the ore-forming geological conditions are good,and prospecting potential of gold reserves is obvious.Nevertheless,due to the exploration fall far behind mining,and the more research work have been carried out for single deposit,which makes the regional mechanism of mineralization is unfamiliar,and leading to the intense controversy for the origin of metals and fluids and so on.The study area is located at southwestern section of Jiangnan orogenic belt,belonging to southwestern part of Hunan-Guizhou gold mineralization belt.It has experienced Wuling period,Xuefeng period,Caledonian and Yanshanian-Himalayan through geological times,which contributed to the complex tectonic associations.The ore bodies are mainly controlled by antincline and fault of Northeast direction.The output forms have been divided into the quartz vein in the anticlinal nucleus and the quartz vein in the shear zone.Mineral assemblage type is relatively simple,common ore minerals are gold,silver,pyrite,arsenopyrite,chalcopyrite,galena and sphalerite,etc.,gangue minerals are mainly quartz,calcite,siderite,etc.The main hydrothermal alteration types are pyritization,arsenopyritization,silicification,chloritization and sericitization,and are closely related to gold mineralization.Based on regional geological characteristics,tectonic evolution background,the typical ore deposit geological features and geochemistry of mineralization.Combined with the basic framework of metallogenic system theory and previous research results,this paper focuses on the metallogenic mechanism,the source of metals and fluids of gold field in southeastern Guizhou,and the following conclusions were acquired:By the characteristics of Regional geology and ore deposit geology of Tianzhu-Jinping area of the Southeastern Guizhou,the macroscopic ore-prospecting criterias have been determined.Integration of petrographic observations and geochemical data from auriferous quartz vein of metasediment-hosted orogenic gold deposits in Southeastern Guizhou establishs the migration and precipitation mechanism of gold,gold clathrate[Au(HS)2-] is primary model of migration in the fluids,and sulfuration results in the precipitation of gold;revealing the Relationship between sulfdes,Carbonaceous material(CM)and mineralization,the physical and chemical properties of CM are favorable to gold mineralization.Meanwhile,the role of regional evolution of the mineralised shear zone in the process of gold mineralization has been illustrated.The trace element and rare earth element in gold-bearing quartz veins,wall rock from the typical gold deposits of Tianzhu area of the Southeastern Guizhou have been determined by Quadrupole-Inductively Coupled Plasma-Mass Spectrometry(Q-ICP-MS).The result shows that the distribution curve of the trace element and rare earth element is similar with the regional metamorphic,indicating a part of ore-forming metals have been come from the regional strata of the low greenchist facies in shallow.The REE of distribution patterns of some auriferous quartz veins dispaly horizontal model,the difference of LREE and HREE was not significant and closer to the upper mantle or lower crust,this metal extraction was accompanied by rock dehydration,this kind of transformation of chlorite and dolomite into hornblende and plagioclase has been loss of between 3 and 5 wt% water during prograde metamorphism from greenschist to amphibolite facies,These transformations liberated the metals and made them available for dissolution in the metamorphic dehydration fluid being generated at the same time.Based on Y/Ho,Th/U show that the main ore forming fluid is metamorphic fluids,and some deposits may be mixed with meteoric water.Basing on the analyses: metallogenic fluids and ore-forming materials should have the feature of multiple sources. |
PDF Full Text Request