| Yata gold deposit located in Ceheng County of Guizhou Province, belonging tolarge-scale carlin type （micro-disseminated） gold deposit, composed of SouthwesternGuizhou gold metallogenic belt with Lannigou, Suiyindong, Zimudang, Taipingdong,Banqi and other gold deposits, and Southwestern Guizhou gold metallogenic belt is avery important part of "Golden Triangle" in Yunnan-Guizhou-Guangxi area.This papper take fluid inclusions as study objects, through studying petrography,micro-thermometry, Laser Raman Spectra, hydrogen and oxygen isotopics,thermodynamic calculation and comparative research with Banjie paleo-oil reservoir,we discussed the character and genesis of ore-forming fluid and the mineralizationand precipitation process of the Yata gold deposit.There are three types of fluid inclusions in the Yata Au deposit, which includesH2O inclusions, CO2-H2O inclusions and CO2inclusions, and the former two are themain types. The homogenization temperatures, salinities and densities of the H2Oinclusions ranged from112.6℃211.4℃,2.07%7.73%（NaCl）,0.9g/cm31.0g/cm3,and the average values of homogenization temperatures and salinities were158.0℃and5.63%（NaCl） respectively, show that the ore-forming fluid was charactered bylow temperature, low sality and middle-high density. The homogenizationtemperatures, salinities and densities of the CO2-H2O inclusions ranged from217.4℃299.7℃,0.63%4.44%（NaCl）,0.924g/cm30.986g/cm3, and their averagevalues were254.3℃,2.27%（NaCl）,0.953g/cm3. The pressure of ore-forming fluidranged from139.634MPa194.513MPa what is overpressure fluid, the shield layer ofwater-isolation what composition of graywacke or siltstone and clay rock in miningarea maybe the reason of forming overpressure fluid. The research of hydrogen andoxygen isotope showed that the ore-forming fluid are mainly from meteoric water orbasin fluid which associated with meteoric water.There is a high similarity betweenthe ore-forming fluid and Banjie paleo-oil reservoir of homogenization temperatures,salinities, densities, composition and source, what show that both of them may beevolved from organic ore-bearing fluid of the same origin. When the late Yanshanian period, there are strong structural fault activity in thisarea, the shield layer of water-isolation what composition of graywacke or siltstoneand clay rock in mining area were destructed by faulting, which makes theore-forming pressure of overpressure fluid property suddenly decreased and occurredfluid immiscibility, the ore-forming occurred phase separation and formed two fluids,which one was rich with CO2and the other was rich with H2O, and the solubility ofAu in the ore-forming was decreased rapidly, then precipitated in the fault zone,interlayer gliding and other site of pressure release, which is the main cause of theformation of Yata gold deposit. |
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