Characteristics of Fluid Inclusions and Metallogenesis of Annage Gold Deposit in Qinghai Province, China
- 1 Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education, School of Geosciences and Info-Physics, Central South University, Changsha, China
- 2 Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education, School of Geosciences and Info-Physics, Central South University, Changsha, China
- 3 Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education, School of Geosciences and Info-Physics, Central South University, Changsha, China
- 4 No. 8 Team, Qinghai Bureau of Nonferrous Metals Geological Exploration, Xining, China
- 5 No. 8 Team, Qinghai Bureau of Nonferrous Metals Geological Exploration, Xining, China
Abstract
The Annage gold deposit is located at the east part of the eastern Kunlun orogenic belt. The characteristics of ore-forming fluids and metallogenesis were discussed by using fluid petrography, micro-thermometry and hydrogen-oxygen isotope analysis. Three stages, namely quartz-pyrite stage (A), quartz-polymetallic-sulfide stage (B) and quartz-ankerite stage (C) were included in the hydrothermal process as indicated by the results of this study. Inclusions developed in ore-bearing quartz veins from stages A and B are of three types: aqueous inclusions (type I), CO 2 -bearing inclusions (type II) and pure CO 2 inclusions (type III). All three types of inclusions, mainly type I, are presented in stage A, having homogenization temperatures at 180 ° C - 360 ° C, and salinities ranging from 0.53% to 21.44%. In addition to development of type I inclusions, type II and III inclusions increase significantly in stage B, with homogenization temperatures ranging from 160 ° C to 330 ° C, and salinities are from 1.32% to 22.01%. Based on micro-thermometry, fluids in Annage deposit are of H 2 O-NaCl-CO 2 type with medium-high temperature (140 ° C - 395 ° C) and medium-low salinity (0.53% - 22.01%). Results of hydrogen-oxygen isotope analysis show that ore-forming fluid is mainly CO 2 -rich magmatic fluid, mixed with shallow groundwater or metamorphic hydrothermal in the late mineralization stages. Calculated metallogenic pressures are in the range of 79 - 130MPa corresponding to a maximum depth of 4.8 km. The Annage deposit is a mesothermal quartz vein type gold deposit.
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