Characteristics Of Fluid Inclusions And Metallogenic Prognosis Of Jianquanzi Gold Deposit At Alashan

The tectonic position of Jianquanzi gold deposit belongs to the Heli mountain uplift zone of southwestern edge of Alashan block in North China platform. On the basis of geological survey in the field, the metallogenic fluid characteristics and metallogenic mechanism of Jianquanzi gold deposit are researched by ways of analysising of the fluid inclusions, oxyhydrogen stable isotope.The results of analysis of fluid inclusions show that homogenization temperature, salinity and density of fluid inclusions ranged from 182.5℃to 308.6℃(its average is 295℃), 2.07% to 9.21%( its average is 6.03%), 0.74 g/㎝ 3 to 0.93 g/㎝³. Based on the average metallogenic pressure which is 218.6×10⁵Pa, the estimated average metallogenic depth pressure is 2.186 km, belonging to the middle-shallow depth type. Composition analysis of fluid inclusions show that gas composition of fluid inclusions are mainly H₂O and CO₂, meanwhile contains H₂, H₂S, CH₄ and N₂; The appearance of reducing gas including H₂, H₂S and CH4 reflects the reducing environment of ore-forming fluids. Gas composition including a large number of CO₂ reflects the characteristics of mineralization of low pressure, also illustrates that CO2, H₂S, H₂ and CH4 as important mineralizer involved in the process of mineralization in the deposit; The results of analysising of hydrogen and oxygen isotopic composition reflect that the hydrogen isotopic composition in quartz is -67.2‰ -73.1‰; Oxygen isotope composition in quartz is 10.8‰ 14.2‰; Oxygen isotope composition in water is 1.7‰ 5.1‰. These results show that ore-forming fluid seems to be a mixture of magmatic and metamorphic water mixing with litter meteoric water. Fluid mixing, fluid-wallrock interacting, the decreasing of temperature and pressure possibly lead the ore-forming elements to concentrating and depositing within the ore-hosting space.