Study On The Relationship Of Structure-fluid-gold Mineralization From Yangshan Gold Deposit In Gansu

Yangshan gold deposit, which has the biggest treserves in Asia, is located in thecentral and south part of southern subzone in the area of western Qinling, GansuProvince. Tectonic evolutionary analysis shows that Yangshan has the characteristicsof multi-stages and multi-level. Owing to the complex nature of structures andconstituents, Yangshan has formed a complex structural deformation combination.Based on the previous research results, we have emphatically studied on theregional metallogenic background, ore-controlling structural system, characteristics ofquartz fabric and fluid inclusions, and structural features of NO.17exploration line,and have summarized the structure-fluid-gold mineralization model of Yangshan golddeposit. According to the study, some conclusions can be drawn:1. Yangshan gold ore deposit has a strong tectonic transposition, and formedpenetrasive foliation S2. After that,we can make out4-stage structures:（1） thrustnappe spreading from north to south.（2） extensional tectonics trending nearly NSdistribution.（3） thrust nappe spreading from south to north.（4） extensional tectonicstrending nearly ns direction. The deformed rocks in the belt are chara-cterized by thedevelopment of stretching lineation, boudin, domino structure, mechanical twinning,quartz ribbon, dynamic recrystallization, microcracks and relic phenocrysts etc. Mostof these structures including macroscopic and micmi-croscopic characteristics showductile-brittle shear from north to south.2. Study on the fluid inclusions shows that the homogenization tempreture is165²90℃. Ore-forming fluids are basically from the NaCl-H₂O-CO₂system. Den-sity of ore-fluids ranges between0.98g/cm^-3and1.02g/cm^-3. Metallogenic pressure isabout896bar.Salinity ranges from0.7⁹.4NaCl equivalent wt percent. Results oflaser raman spectroscopy show that the main components are H₂O and CO₂. Based ondifferent paragenetic association of fluid inclusion and the characteristics of fluidevolution, we draw the conclusion that the mixture of different fluid leads to golddeposition. 3. The tectonic evolutionary stages of NO.17exploration line includesedimentary stage, regional metamorphic stage, compression stage and denudationstage. The main stage of forming main orebody of Anba Ore Block happens after thepriod when the mountain formed by compression is denudated, and they mainly existin fracture zone as well.