Ore-forming solution and genesis of a rock crystal deposit in south Hunan, indicated by fluid inclusion studies

Si, Al, Ca, Mg, Fe, Na, K, CO 3 −2 , F, etc. are detected from the fluid inclusion leachates. Among these constituents, Si, Na, and CO 3 −2 are predominant, amounting to more than 80 percent. This indicates that the ore-forming solution must be alkaline with Si, Na, and CO 3 −2 as its dominant components. Homogenization temperatures for the solution range from 80 to 360°C. Although rock quartz can crystallize at the above temperature interval, perfect crystals of economic importance are largely formed below 260°C. The temperature of formation increases toward the granite intrusives at a rate of about one degree per meter. It is estimated from the lithostatic load that the salinity of rock quartz is 17–23 (NaCl wt%), while that of vein quartz is relatively high as compared with the former. There is a tendency for the salinity of the ore-forming solution to increase with depth.