Study On The Geologic Feature And Prospecting Prognosis Of Yangpingwan Gold Deposit In Northern Shiquan In The South Qinling

The northern part of Hanyin-Shiquan metallogenic belt is located in the South Qinling orogenic belt,and the multi-stage tectonic superposition and foliation replacement are strong,which resulted to the special type of gold deposits in this area.What the ore-controlling geological factors are in the gold deposits in the area,what the mineralization materials are,what type of ore-forming tectonics and ore-controlling tectonic patterns are,and what the characteristics of mineralization are,and what the key signs are,what the prospect of the mine in depth is,that are the most critical problems yet to be studied of the gold metallogenic belt.Therefore,it is necessary to select the comprehensive study and analysis of Yangpingwan,which is a typical gold deposit in the western part of the gold belt.Based on the China Geological Survey Bureau's research project of Specified mapping and prospecting of Yangpingwan and Huanglong mining area in Shaanxi Xunyang,the tectonic-petrographic mapping,the geological profile survey and the geological survey are carried out on the basis of the comprehensive analysis of the previous research results.The ore-forming characteristics,the main ore-controlling factors,the ore-controlling structure characteristics,the ore-forming fluid characteristics and the ore-forming material source,and explored the ore-forming tectonic evolution and the deposit in the study area are studied.The results determine the prospecting target in the study area.The main findings and innovations are as follows:Yangpingwan gold deposit is characterized by multiple stages of mineralization in the metamorphic rocks of the Lower Silurian Meiziya Formation.The mineralization time of the southern and northern alteration? zone are relatively earlier,mainly related to the ductile shear deformation.The control factors of the gold mineralization are lithology,brittle-ductile shear zone,fold,alteration and heat metamorphic superposition.The mineralization time of the northern alteration ? zone is relatively late,which is mainly related to the near-east-west brittle fracture zone of the mining area,and the fracture zone is mainly related to the fracture zone.The intrusive rocks are probably the product of the early Yanshanian continental orogenic stage.The intrusion of the veins is mainly in the width of less than 1m along the S₂ foliation direction or a small angle of the intersection of the acidic intrusive veins,mostly located in or aside of the gold mineralization alteration zone,the rock itself has a certain degree of gold mineralization.The similarity curves of the normal mantle normal spider webs map and rare earth element chondrite meteorites map have similar distribution curves,indicating that there are differences in the lithology of the rock veins,but the reason for their forming is similar,which may be caused by the magma in the process of invasion and mixed with different materials.The zircon U-Pb ages of the Guanyinhe granodiorite veins and the Shenba granite fine-grained veins in the northern Hanyin are 180.2 ± 3.6Ma and 172.1 ± 4.5Ma respectively in the same tectonic zone with similar geochemical characteristics in the study area,the comprehensive determination of the study area of intrusive veins formation time is the early Yanshanian period.The genesis type is shallow and medium-low temperature hydrothermal gold deposits.The quartz vein formation temperature is mainly from 180 ? to 200 ?,and the average depth of mineralization is 2.46 Km in the S₂ period and the quartz vines formation temperature is mainly greater than 300 ?,and more at 380 ? 400 ?,the average formation depth is 3.17 Km.The main oxides and trace elements in the gold ore body and the surrounding rock are similar,and they have similar distribution curves on the normalized mantle normal spider web map and the normalized rare earth distribution curve of the chondrite meteorite map.The results of the electron probe analysis show that the isotopic characteristics of the quartz veins show that the source of ore-forming fluids related to the quartz veins of S₂ and S₃-1 is more complicated than that of the quartz petals,mainly composed of metamorphic water,and magmatic water mixed;S₂ quartz veins ?30Si is 0.6,two mica quartzite schist ?30Si is 0.6,the two are more similar,S₃-1 quartz vein ?30Si is 0.4,granite pegmatite ?30Si is 0.3,the two are more similar;gold ore containing pyrite and pyrrhotite S isotope ?30Si between 7.5-11.7 ‰.The mineralization of the southern alteration zone and the north ?alteration zone is mainly related to the ductile shear zone.The formation temperature of the quartz veins in the S₃-1 period is not conducive to the enrichment of gold.Combined with the relationship between the quartz veins and gold mineralization in the S₃-1 period,the formation time of the quartz veins in the S₃-1 period may be not later than that of the northern ? zone.The magmatic activity may be later than the south Mineralization alteration zone and north alteration ? zone,the heat source produced by magmatic activity may promote the further enrichment of gold elements.The ore mineral assemblage,the alteration characteristics of the surrounding rock,the ore body morphology,the ore structure and the structure are mainly characterized by low-temperature mineralization,no large-scale high-temperature hydrothermal mineralization,combined with the analysis of mineralization,comprehensive judgment Yangpingwan gold deposit is medium and low temperature hydrothermal gold deposit.In order to reflect the distribution characteristics of gold mineralization in geological bodies,the numerical model of three-dimensional mineralization domain was established by using Surpac software.The model shows that the high-grade gold mineralization in the mining area is very similar to the spatial distribution of the known orebodies,and all have the characteristics of slow dumping.The overall gold mineralization is not completely connected along the direction of the strike direction,parallel distribution of sub-mineralization zone,the secondary mineralization zone to the mining area with the overall mineralization to a small angle of intersection,and constitute the overall mineralization of the mining direction.The gold mineralization does not continue to extend on the gold mineralization contours,but the gold mineralization is still open to the deep along the dip direction,and may have better prospecting potential along the dip direction and at depth.The study area has the characteristics of multi-stage mineralization,and the southern mineralization alteration zone and the north mineralization alteration ? zone are related to the ductile shear deformation of the Late Indosinian-Early Yanshanian period,which is related to the near-east and west brittle fracture in the area since the early Yanshanian period.The former study shows that the tectonic deformation time of the study area is mainly 222-189 Ma and 178-161 Ma,and the K-Ar age of the biotite single mineral in the gold ore in northern Ankang is 184.12 ± 3.32 Ma and the ductile shear deformation S₂ foliation in the biotite Ar-Ar dating for 161-169 Ma in Shiquan Raofeng area,in gold ore of Yangpingwan the pyrite Rb-Sr isochron age of 208 ± 0.88 Ma.According to the characteristics of mineralization alteration zone in the study area,the mineralization of the southern alteration zone and the north alteration ? zone should be earlier than that of the northern alteration ? zone.The comprehensive analysis shows that the metallogenic age of the study area is late Indosinian-early Yanshan period.The mineralization evolution process is the four main stages of the early Silurian sedimentary diagenesis,the Late Devonian-Middle Triassic metamorphic,the Late Triassic-Middle Jurassic tectonic mineralization and the later Jurassic.According to the relationship between gold mineralization and different lithology,tectonics,quartz veins and magmatic activity,the main prospecting signs of the ore-forming are lithology,ore-controlling structure,hydrothermal alteration,quartz veins and intrusive rocks.In the known gold alteration zone to the south eastward extension section delineated three ore prospecting targets;combined with three-dimensional mineralization domain digital model,the low-grade gold mineralization along the dip direction and deep has the features of better prospecting potential than in strike direction,in the existing ore body deep along the low-grade gold mineralization direction to identify the three ore prospecting targets.