Morphological Characteristics and Chemical Composition of Placer Gold from the Kengeveem River Basin and First Data on Associated Platinum-Metal Mineralization (Magadan Oblast)

Abstract

The paper presents a study of typomorphic characteristics of placer gold from tributaries of the Kengeveem River, Magadan oblast. The placer gold was studied by optical and scanning electron microscopy at the Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences. As a result, the first information on the morphology, internal structure, and chemical composition of placer gold from the southeastern Taigonos Peninsula was obtained. Three mineral types of the gold were determined. The first type is dominant. Its grains are characterized by subore morphology, with weak and medium roundness. Only Au and Ag are present in the composition of native gold, other macrocomponents were not found. The gold fineness is 750‒950‰. Some gold grains bear signs of supergene transformation, which is expressed in the development of high-fineness gold rims and intergranular veins. The second type of the gold is represented by well-rounded plates with a fineness of 980‒990‰. The third type is loose aggregates of secondary high-grade mustard gold. The obtained data allowed us to determine the different transport distances of native gold and to consider the low-sulfide epithermal Au‒Ag mineralization and presumably distal gabbroids as the primary sources of gold.