Study On The Geological-geochemical Characteristics And Origin Of The Yuzigou Gold Deposit,Tianshui

The Qinling Mountain Range,which runs from east to west in central China,is regarded by the geologists at inland and abroad due to its special geological structure and complex evolutionary history.The Yuzigou gold deposit in this study is located on the south side of the Shangdan suture zone in the West Qinling,and the imperceptible turning point of the Liziyuan area in the area of the Yuanlong-Liziyuan regional anti-S type structure..West Qinling,which is rich in mineral resources and has a good place for enrichment,is also one of the key areas for studying the metallogenic system of the complex orogenic belt.Therefore,the geological structure and metallogenic conditions of the Yuzigou gold deposit are relatively complex,and the previous research is also low.There is a lack of systematic and in-depth research on the geological characteristics of ore deposits,ore-forming fluids and material sources,ore-controlling factors,and genesis of deposits.The lack of experimental data supports the division of deposit types.Based on the comprehensive collection of geological data from regional and research areas,this paper conducts a comprehensive analysis of the geological features,geochemical characteristics,ore-controlling factors,and genesis of the gold deposits.The main achievements and understandings are as follows:?1?The gold deposits in the mining area are developed in metamorphic volcanic rocks of greenschist facies,and are part of the ophiolite in Guanzi Town.The exposed strata are mainly in the lower rock group?Pz₁Lz₁?in the Lower Paleozoic Liziyuan Group.The tectonic activity is intense and has multiple phases.In the early stage,the brittle-ductile fault zone and its secondary faults were mainly located in the northwest direction,and the northeast-facing faults formed in the later stage formed X-shaped structures in the region.?2?Acidic dikes are more developed in the Yuzigou,and the intrusive rocks mainly include the Tianzishan monzonitic granite and the late granite porphyry in the west.The gold deposits in the early ductile shear zone are mainly formed around the Tianzishan,and the late phase is mainly the relationship between granite porphyry and gold mineralization.?3?The ore body distribution,ore-controlling factors and mineralization characteristics of the Yuzigou gold deposit in the mining area are described in detail.A total of five ore bodies have been delineated.The No.1.2 ore body is oriented in the northwest direction.The ore body is controlled mainly by the northwest fault and is hosted in the Juanyun chlorite quartz schist and the Juanyun quartz schist in the second lithologic section of the Xiayan Formation in the Liziyuan Group;No.3 The orebodies are in the northwest direction.The orebodies are mainly controlled by granite porphyry and northwest faults.No.4.5 orebody is a blind ore body with two types of ore structures.Late porphyry cutoff early ductile shear zone type Gold mine?4?The rock wall alterations seen in the mining area are mainly silicified,chlorite,green-roofing,metal sulfide mineralization,and local sericitization.Pyrite mineralization,silicification,and carbonation are evident below the oxidized zone,with local chlorite and green linoleum petrification.The types of alteration most closely related to gold mineralization are mainly silicified,chlorite and sulfide mineralized.?5?The area has experienced two periods of hydrothermal and early supergene mineralization as hydrothermal interactions with the diorite granite magmatic hydrothermal action and ductile-brittle shearing,and the late stage is associated with granite porphyry during the hydrothermal period.The two phases of mineralization have different superposition effects at different locations;the epigenetic period distributed in the surface-near surface oxidation zone,has a secondary enrichment of gold mineralization.?6?The study results of the stable isotopes H,O,and S in the deposits show that sulfur is a deep source sulfur that inherits the characteristics of the original rock and undergoes a later-stage hydrothermal transformation;the ore-forming hydrothermal fluid is a multi-source mixed hydrothermal fluid of atmospheric precipitation and magmatic water.The magmatic water features are more pronounced.The characteristics of the quartz fluid inclusions in the deposits show that the ore-forming hydrothermal fluids in this area show the characteristics of medium-low temperature moderate-low salinity hydrothermal gold deposits.?7?In this study,a comprehensive analysis of the above-mentioned various metallogenetic factors suggests that there are two types of gold deposits in this area,namely ductile shear zone gold deposits and porphyry rock gold deposits.