Method for Revealing Placer Gold Source

Abstract

Material characteristics of placer gold and geological and geomorphological features of placercontaining watercourses allow revealing the type of source that formed the placer. The studied area (the middle reach of theAdychaRiver, Verkhoyansk District, Yakutia) is characterized by highly developed placer gold mineralization both in ancient terrace sediments and high-order watercourses. The significant placer gold mineralization in the high-order watercourses, at very limited number of known bedrock gold deposits suggests the presence of not yet discovered bedrock gold mineralization. Revealing the type of sources of placer gold in young high-order watercourses allows to create prognostic and prospecting models for both potential placer and primary (vein) ore occurrences. The purpose of the study is to compile a logical-information algorithm, which, based on the most significant material and geological-geomorphological factors, will enable revealing the type of placer gold source and the possibility of its location discovery and probability of gold transportation continuation from the source. The study result is presented by a program (the Python programming language) that characterizes the type of placer gold source based on gold grain rounding degree, the presence of gold intergrowths with other minerals and the presence of heavy fraction. Assessment of the possibility of placer gold source location determination is based on geological and geomorphological factors: watercourse order, the type of placer, and spatial association with terraces of ancient erosion levels. The study of well-known gold placers using the created program allowed revealing gold placers  with supposedly primary gold source and other ones with the source in the form of a natural intermediate gold concentrator. A map of exogenous gold mineralization with forecast elements was also created, presenting areas promising for revealing primary gold mineralization (areas of presence of high-order watercourses with gold mineralization source) and areas of high-order watercourses promising for discovering gold placers (identified by analogy (in geological and geomorphological position) with watercourses with the known source in the form of natural intermediate gold concentrator.