GOLD-BEARING ARSENIAN PYRITE AND ARSENOPYRITE FROM VORONTSOVKA CARLIN- STYLE GOLD DEPOSIT IN THE NORTH URALS

Abstract

Invisible gold in hydrothermal ores is frequently scattered in the most abundant minerals of the Fe–As–S system. It is assumed that invisible gold does not incorporate into the mineral structure (nanoscale inclusions of the metal or its compounds) or is chemically fixed (isomorphous substitution). The aim of this study is to determine the concentration range of invisible gold, species of its occurrence in arsenian pyrite and arsenopyrite in the natural samples from the Vorontsovka Carlin-type deposit in the Northern Urals. According to EMPA, LA-ICP-MS analyses, the number of trace elements Sb, Co, Ni, Ag, Cu in arsenian pyrite and arsenopyrite does not exceed 0.1 wt% in total. Specially selected survey conditions were used to determine the Au impurity content. Under these conditions, the detection limit for Au is 0.0045 wt%. The As content in pyrite varies from 0.28 to 4.316 wt%, Au – from 0.2 ppm to 0.074 wt%. The Au content in arsenopyrite reaches 1.23 wt%. Correlation dependences of Au and As contents in pyrite, Au and the main components in arsenopyrite suggest the occurrence of Au in the structure of the minerals.