Gold-silver ratio as variability factor for epithermal deposits

Comparative studying of regional variations for gold-silver ratio in ores of epithermal deposits is executed. For this purpose the database on 515 deposits of the world have been created. It contains the complete information on their geographical co-ordinates, reserves and contents (gold and silver). Statistical analysis of distribution for parameters of gold-silver ratio and application of EM-algorithm (Expectation-Maximization) for separation of probability distribution mixture has allowed to define the boundaries for definition of gold-silver specialization of deposits: mainly silver (less than 1:250), gold-silver (1:250 - 1:25), mainly gold (more than 1:25). For more detailed classification the last group can be presented as mixture of 4 allocations with boundaries (1:25 - 1:8, 1:8 - 1:3, 1:3 - 1.2:1, more than 1.2). The executed calculations have allowed to receive the science-based summary about gold-silver specialization of the Central and South Americas and the Northeast of Russia. The North America, Thetis, Northeast of Asia, Oceania and Australia are classified as mainly gold.