Geochemical Characteristics of Host Rocks and Ores of the Verninskoe Large Gold Deposit (Bodaibo District, Russia)

Research subject . The Verninskoe large gold deposit (Bodaibo District, Irkutsk Oblast). Aim . The study of trace and rare earth element distribution in ores and host rocks and the specific features of ore formation. Materials and Methods . The geochemical features of ores and host rocks of the Verninskoe deposit are studied by X-ray fluorescence analysis and inductively coupled plasma mass spectrometry. Results. The host rocks are slightly enriched in a wide range of elements (given in the order of enrichment factor decreases): As, Ag, W, Cr, Au, Ni, Cd, Ba, V, Bi, Sc, Sr, Co, Mo, Cs, and Ti. The ores are highly enriched in Au, As, and Ag. The enrichment of the ores in Mo and Bi may be due to the relatively high admixture of these elements in diagenetic pyrite, which is widespread in host rocks. The Sr enrichment indicates its capture from the host calcareous sandstones. The deposition of a significant amount of arsenopyrite in the ores could be due to an additional supply of As from the rocks of the ore-bearing Aunakit Formation enriched in As. Conclusions. According to geochemical indicator values, the host rocks of the deposit can be classified mostly as shales and graywackes, while a number of samples are represented by Fe-sandstones, litharenites, and sublitharenites. Trace element and REE distribution in the ores indicates the interaction of the ore-forming fluid with the host rocks. The results obtained correspond to the metamorphogenic model of formation of the orogenic gold deposits. The information given in the article is of practical importance for regional metallogenic forecasting and modeling and gold prospecting and evaluation.