Mineralogical Criteria for the Prediction of Gold Mineralization in the Structures of the Siberian Craton

Abstract

Generalization of the results of the study of placer gold and the mechanisms of its distribution in the east of the Siberian Platform made it possible for the first time to reveal that the ore sources of gold-bearing placers were mainly mineralization of the gold-sulfide formation formed under the influence of hydrothermal metasomatic processes occurred in deep fault zones. It is determined that the gold-bearing hydrothermal-metasomatic formations of the gold-sulfide rock formation are amagmatic, near-surface, low-temperature and spatially confined to deep faults. These formations are widespread in terrigenous-carbonate strata and sand deposits of PZ-MZ age and are observed in the zones of brecciation, silicification, and ferruginization. The analysis of the mechanisms of distribution of hydrothermal-metasomatic gold-bearing formations in the east of the Siberian Platform, based on previously conducted research of predecessors and our field observations, allowed us to establish the following. In the northeast, hydrothermal-metasomatic formations occur in the field of development of the Zhigansky fault, the Molodo-Popigai and Anabar-Eekite fault system, in the central part of the east of the Siberian Platform, the Vilyui paleorift (Kempendyai dislocations), and in the southeast in the Baikal-Patom thrust belt in ancient faults (Bappagai, Khorinsky, etc.). Metasomatites of hydrothermal origin form extended narrow formations along ancient faults activated in the Mesozoic, as well as conformable deposits in the Vendian, Cambrian carbonate strata, Jurassic and Cretaceous sandstones. It is proved that these formations are amagmatic and are not related to the widespread magmatism of the basic composition, which is confirmed by the homogenous mineral composition of metasomatites, independent of the composition of magmatic bodies spatially located with them. Zones of metasomatites with gold mineralization contain Au from 0.5 to 3.0 g/t, and in isolated cases up to 24–32 g/t. Gold is represented from finely-dispersed to visible fine, with a size from 0.01 to 0.5 mm or more. It is known that hydrothermal-metasomatic processes on the territory of Central Aldan contributed to the formation of large deposits such as Kuranakh, Tabornoye and others. It is possible that the identified gold-ore metasomatites, developed along the zones of regional faults and not confined to magmatic formations, widely occurred both in the northeast and in the southeast of the Siberian Platform, represent a huge metallogenic potential.