„Invisible“ gold in ore minerals from Chelopech deposit

The concentrations of trace elements in pyrite from blocks 7, 8, 17, 18, 19-SE, 19-NW, 19-NE, 19-SW, 103-W, 103-E, 144, 146, 147, 148, 149-south, 150, 151, 153 and 700 of copper-gold high-sulphidation Chelopech deposit were determined by LA-ICP-MS technique. It was found that the average gold content in pyrite from different blocks varies from 1.5 to 17 ppm, in enargite-luzonite – from 0.8 to 61 ppm, in chalcopyrite – from 0.6 to 8 ppm, in tennantite-tetrahedrite – from 1.3 to 3.9 ppm, in sphalerite – from 0.9 to 7.4 ppm, and in bornite it reaches 0.6 ppm only in block 148. Its presence is mainly due to microinclusions of native gold and/or electrum and tellurides, and this is also its predominant variety in the deposit. The higher values and variations in gold content in colloform pyrite are most likely due to adsorption processes, not to isomorphism. Besides the fact that all ore minerals in the deposit are gold-bearing, they are also a potential source of the so-called “critical raw materials” (such as Ge and Ga), especially enargite and sphalerite, which are distinguished by their highest contents (up to hundreds and thousands of ppm in some of the analyses).