Abstract:

Yata gold deposit is a typical sediment hosted disseminated gold deposit in southwestern Guizhou. Based on the data from fluid inclusions, we discuss the temperature and pressure conditions and the fluid evolution in the ore forming process. Results from petrographic observation and fluid inclusion microthermometry study of gangue minerals in different stages give us the following conclusions: fluid inclusions in the main mine ralizing stage can be divided into three categories including H₂O, CO₂ and CO₂-H₂O inclusions, which indicates the immiscibility of the ore forming fluid; while fluid inclusions in the late mineralizing stage are mainly H₂O inclusions; homogenization temperatures of H₂O inclusions in the main mine ralizing stage vary from 139 to 268 ℃, salinities range from 2.9% to 7.4%, while homogenization temperatures of H₂O inclusions in the late mineralizing stage vary from 121 to 194 ℃, and salinities range from 2.7% to 6.6%. According to the simultaneous solution of isochoric formulas derived from H₂O inclusions and CO₂ inclusions, the capture temperatures of inclusions in the main mineralizing stage vary from 260 to 294 ℃, while capture pressures range from 59 to 98 MPa. Based on the comparison of characteristics of CO₂ rich fluids in different types of gold deposits, we conclude that CO₂ rich fluid in Carlin type gold deposits in southwestern Guizhou may play a role in the transportation of gold, and that phase separation between CO₂ and H₂O could be the cause for gold deposition.

Key words: fluid inclusion, ore forming fluid, Yata gold deposit, Carlin type, Guizhou