Vol. 336 No. 12 (2025)

DOI https://doi.org/10.18799/24131830/2025/12/5349

Gold in the weathering crust of the Sokhatin deposit (North-East of the Russian Federation)

Relevance. The Prikolymskoe uplift is a significant and long-evolving tectonic structure in Northeast Asia. Its unique neotectonic history created favorable conditions for the accumulation and distribution of Cenozoic sediments. Of particular interest are the weathering crusts, which often contain gold concentrations many times higher than in primary ores. Aim. To gather new data on the structure, zoning, and mineralogical and geochemical properties of gold in the weathering crust. This will help determine the supergene nature of the gold and estimate its potential abundance in the oxidation zone. Object. Weathering crusts in rocks, metasomatites, and ores from the Sokhatin deposit. Methods. Mineralogical analysis of concentrates. Microscopic observations of gold particles were conducted using a binocular microscope. Chemical composition analysis was performed with inductively coupled plasma mass spectrometry and a TESCAN VEGA 3 scanning electron microscope equipped with an Oxford energy-dispersive attachment. Bulk mineral composition, clay mineral identification, and quantitative mineral analysis were determined using powder X-ray diffraction analysis on a Rigaku Ultima IV diffractometer. Phase analysis of total sulfur and sulfate sulfur was conducted to assess the oxidation state of sulfides. Results and conclusions. It was established that gold-bearing minerals are linear residual weathering crusts confined to tectonically weakened zones that control endogenous mineralization. A complete weathering profile was not established. Oxidation develops primarily along steeply dipping zones. The identified linear weathering crusts extend for distances of hundreds of meters with a thickness of over 10 m and a dip of tens of meters. This weathering crust represents a special type of ore formation, characterized by unique mineralogy and geochemical parameters and specific technological properties. Hypergene gold crust is represented by hemiidiomorphic, idiomorphic, xenomorphic, and irregular formations. The highest gold concentrations were observed in size classes 1–0.5, 0.1–0.05, and <0.05 mm, with maximum metal contents reaching up to 39.0 ppm. Gold from the oxidation zone has a moderately high-fine and high-fine fineness, with impurities consisting primarily of silver. Oxidized gold becomes more refined as a portion of silver is removed. During ore oxidation, gold redistributes and concentrates, significantly increasing the economic value of the ores in the weathering crust for extraction.

Keywords:

gold, weathering crust, crystal morphology, Sokhatin deposit, Prikolymskoe uplift

Authors:

Timofey V. Timkin

Valery G. Voroshilov

Irina V. Martynenko

Tamara Yu. Yakich

Anastasia N. Nikolaeva

Diana K. Molukpaeva

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