Metallogenetic Regularities And Predictions Of The Dishui Sandstone-Type Copper Deposit In Xinjiang Uygur Autonomous

In the world wide range,sediment-hosted stratiform copper deposits account for about 23%of the world's proven copper reserves and production,next to porphyry copper deposits,ranking the second.According to its ore-bearing rock facies,sandstone-type copper deposits can be divided into two types,continental sandstone-type copper deposit and marine sandstone-type copper deposit.Continental sandstone-type copper deposit accounts for a very small proportion in the world,and in our county,this type of copper deposit is mainly distributed in the middle Cenozoic sedimentary basin in south China.The proved reserves of continental sandstone-type copper deposit accounting for 2.4%of the total copper reserves in China,and this type of copper deposit has a higher ore grade and often accompanied by Ag and other useful components.The scale of continental sandstone-type copper deposit is up to large size and most of the deposits have been exploitation.Continental sandstone-type copper deposit has become one of the important exploration targets in China in recent years.There are more than 20 sedimentary-type copper deposits in different sizes develop in the Kuqa basin from west to east in the southern Tianshan mountains region of Xinjiang.These copper deposits have similar occurrence position,similar genetic type,and occurrence in the same set of clastic rock and obviously controlled by the types of rocks and lithofacies characteristics.Dishui copper deposit in the Neogene Kuqa basin belongs to the typical continental sandstone-type copper deposit,its ore body scale is relatively large,and it is a representative deposit.In this paper,Dishui continental sandstone-type copper deposit in Baicheng is a typical deposit.On the basis of field investigation and indoor comprehensive study,this paper summarize the metallogenic regularity of Dishui copper deposit,find out the intrinsic factors of occurrence-controlling of the deposits,establish a metallogenic model for typical deposits,summarized the main ore-controlling factors,establish a comprehensive geological prospecting model and predict the resources prospect in this region.On the basis of measured section in the field,recognition of sedimentary facies,thin section and polished section microscope observation,grading analysis and combined with some regional geological data,this paper divides the Miocene of Neogene(Jidike formation,Kangcun formation)and Pliocene(Kuqa formation)in the study area into alluvial fan-fan dalta sedimentary system and lake sedimentary system,and they were further divided into a few subfacies,fan delta plain,fan delta front,pro-fan delta,shore-shallow lake,gypsic saline lake and several sedimentary microfacies.Kangcun formation is the ore-bearing bed layer,and mainly develops fan delta deposition.Ore-bearing bed is closely related to the sedimentary environment from the research on sedimentary characteristics and sedimentary facies of copper bearing rock series.The main ore-bearing bed in the mining area is in the position of transition from red rock series to gray rock series of upper Kangcun formation,namely in the position of fan delta front subfacies(medium and fine grained sandstone in the underwater distributary channel microfacies is the enriched period of copper ore)of the overlying lacustrine facies(marlstone).This sedimentary environment ensure the enrichment of copper material in the lower sandstone in the process of diagenesis.The mining area is located in transition area of Yakelike anticline in the west and the northern flank of Misikantage anticline in the southwest.The northern flank of Misikantage anticline develops a north-shelving thrust sheet extend along the section stably,provides a stable tectonic environment for the distribution of copper layer.The NEE-trending stratigraphic vertical belt and NEE-trending compressive fault in the mining area distribute in belt and extend obliquely through the mining area.The NW-trending compresso-shear fault in the mining area has a large scale,and was second only to the NE-trending structure.The structures in the mining area are post-metallogenic structures,affect the spatial distribution of industrial ore body to some extent,especially the structure in the east part of the mining area.Based on whole rock analysis for the typical samples collect in the research area,whole rock analysis and analysis of characteristics of rare earth elements for the typical samples collect near the ore-bearing layer,this paper argues that the provenance of the main clastic rock in Jidike formation and Kangcun formation is basically the same,the sandstone of the ore-bearing layer formed in the relatively weak alkaline condition.Outdoor and indoor comprehensive study suggests that Dishui copper deposits mainly formed in the rock-forming period.After superficial oxidation leaching,the primary sulfide turn into cuprite by oxidation,and forming streamers of red-bed copper deposits.And for this reason,Dishui copper deposit belongs to typical continental sandstone-type copper deposits.The formation of Dishui copper deposit has experienced several stages as follows:?Primary sedimentary stage,this stage mainly present the formation of framboidal pyrite;?iagenesis stage and Mineralization stage,this stage is the main stage of mineralization;?Superficial oxidation stage.Dishui copper deposit belongs to syngenetic deposit-diagenesis stage reformation type ore deposit.Formation lithology,sedimentary environment and sedimentary microfacies,structure and surface earth environment affect the formation of Dishui copper deposits.In the process of mining depth and peripheral metallogenic prediction,it is necessary to pay attention to the comprehensive influence of the above factors.According to the ore-controlling factors analysis,this paper give a criterion for mining depth and peripheral metallogenic prediction,and make a prediction for the prospective resources on the peripheral area of mining area and put forward corresponding verification advice.