Study of the Method of Geochemical Prospecting for Gold-Silver Deposits, an Example of Mercury Indication at the Okuchi Mine

Abstract

As suggested by the results of Russian investigations of geochernical prospecting methods, mercury can be an effective indicator for localization of hydrothermal gold-silver vein deposits that contain trace of mercury minerals. Reviewing the studies on geochemical prospecting methods by means of mercury indicator, the authors improved the analytical method for mercury and obtained good results. For masking disturbing elements in the process of dithizone colorimetry, tests were carried on EDTA and CyDTA as masking agent. Dithizone-carbontetrachloride solution of 0.25 ml containing 0.0005% dithizone is very effective to detect Hg²⁺+ in 0.1μg. Extraction of mercury is favourable for acid solutions of pH 5. For dissolving soil samples aqua rigia is preferable, but the acidity of solutions must be controlled. The method is very cheap in cost and rapidity is remarkable.
Ore deposits of the Okuchi mine are several subparallel groups of gold-silver quartz veins of epithermal type, occurring in the volcanic formation of the Neogene age. Many anomalies found by application of the method to surface soil suggest good representation of the localization of subsurface vein deposits in the area where outcrops are scarce.
The intimate relationship between the surface indications and the corresponding subsurface ore deposits must be the result of hypogene dispersion of mercury, a process of mineralization in favour of structural and lithological conditions.