Characteristics Of Fluid Inclusion And Isotope In Linglong Gold Mine, Shandong, China

Linglong gold deposit, located in the gold ore deposit cluster of the northwest of Jiaodong, is a typical example of quartz vein deposit. Along with the recent exploration projects of the crisis mines, some of deep ore body which over thousand meters has been discovered, so that the great convenience has been provided to the study of ore-forming regularity and the expansion of ore prospecting. Therefore, it is significant that the ore-forming fluid characteristics are compared in different spaces. Based on several main ore vein in East Mountain and West Mountain, the source of ore substance and the fluid and the ore-forming mechanism were dissussed by petrography, temperature, salinity, composition of fluid inclusions and stable isotope in this thesis. And main results are as follows:(1) The type of fluid inclusion in quartz of linglong gold mine includes mainly aqueous two-phase, and then carbon dioxide-bearing three-phase, and a little carbon dioxide. In the high temperature stage, both aqueous two-phase, carbon dioxide-bearing three-phase and little pure gas inclusion are existed. In the low temperature stage, aqueous two-phase inclusions are main. The composition in inclusion showed that the ore-forming fluid was mainly water and CO2, and it is NaCl-H2O-CO2 system.(2) The ore-forming temperature is a little different between East Mountain and West Mountain. In West Mountain, the temperature is mainly 160~320℃, which is lower than that in East Mountain where the temperature is mainly 180~360℃. And the salinity of the ore-forming fluid is very different between East Mountain and West Mountain. In West Mountain, it is mainly 8.5~11%, which is higher than that in East Mountain where the salinity is mainly 4~9%. The density of the ore-forming fluid in West Mountain and East Mountain is from 0.5 to 1.0g/cm3, and a little low-density fluid, such as precipitate water, was added in East Mountain. The mechanism of the ore-forming is considered as fluid-boiling and water/rock interaction on No. 55 vein in West Mountain while fluid-boiling and water/rock interaction on No. 47 vein in East Mountain.(3) The pressure of fluid and the depth of ore-forming are calculated according to the different fluid conclusions type. The pressures in most of inclusion are lower than 100MPa based on aqueous two-phase, and the ore-forming depth is 0.5~8.25km. The pressures in most of inclusion are between 130~230MPa based on carbon dioxide-bearing three-phase, and the ore-forming depth 9.5~12.1km.(4) Stable isotope results shows: theδ13C andδ18O in calcite are mainly -3.5~-6.5‰and 11.0~12.5‰, respectively; TheδD andδ18O in the fluid inclusion of quartz are mainly -51.8~-93.0‰and 4.50~9.89‰,respectively; Theδ34S in pyrite is 3‰～10.5‰, mainly 5.5~8.0‰; The lead isotope composition: 206Pb/204Pb is between 17.142~17.481, mean is 17.270, 207Pb/204Pb is between 15.406~15.588, mean is 15.475, 208Pb/204Pb is between 37.691~38.271, mean is 37.901. Therefore, Archaean Jiaodong rock group is considered as original rock series of gold. And gold gathers into a deposit in the favorable setting after the mobilization of Yanshan mobile gold in Mesozoic and the hydrothermal alteration later.