Prediction of possible primary sources of gold-platinoid mineralization within the Lena- Viluy interfluve (East Siberian platform)

Abstract

A wide mineral scattering halo of fine and thin high-standard gold with still unidentified commercial placers and primary sources is typical for the East Siberian platform, particularly the central part of the Viluy syneclise. It is related to the fact that the studied area overlaps with a thick layer of the Mesozoic-Cenozoic deposits, where traditional methods of prospecting for gold deposits do not yield positive results. It is well known that placer gold can retain “genetic memory” of its primary endogenetic gold sources. In this connection, detailed mineralogical studies of placer gold were performed with the aim to identify mineral types of gold mineralization and to forecast and assess primary gold content. Mineralogical-geochemical features of gold and mechanisms of its distribution from channel fill and the Quaternary deposits of numerous water courses of the Lena-Viluy interfluve. Over 300 samples were analysed, and the analysis takes morphologic features of gold, granulometric composition, fineness, composition of trace elements, inner structure and presence of micromineral inclusions into account. Permanent admixtures of Pt (6–96 g/t), Pd (5–570 g/t) and Ni (5–100 g/t), as well as micro-inclusions of the exotic mineral phase of platinum group are identified in placer gold of the Suntar arch in right-bank tributaries of the Viluy river (Kempenday, Chybyda, Tonguo, Kundayi rivers etc.). Apart from that, micro-inclusions of hematite, ilmenite, rutile, sulfides (pyrite, chalcopyrite, galena) and Fe—Mg-aluminisilicates, which correspond to ore mineralization and are typical for magmatism of the basic composition, are found in gold. The combination of identified mineralogical-geochemical features of gold indicates that the Precambrian hightemperature, deep depth mineralization processes were primary sources of gold. This allowed to forecast the presence of primary sources of gold-platinoid mineralization, probably related to basites of the Early Proterozoic and later age, within the Suntar arch for the first time.