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—Data on geochemistry, distribution of ore and rare-earth elements and precious metals, and micromineralogy are presented. The objects of study are late Permian sedimentary and volcanosedimentary deposits of the Tikhonya Brook (Atkan (P3at) and Omchak (P3om) formations) and hydrothermally metamorphosed rocks of the Natalka and Pavlik gold deposits of the Omchak ore–placer cluster. Analysis of the deposit ores showed enrichment in chalcophile trace elements Au, Ag, As, W, and Sb relative to their average contents in the upper crust and the host Permian rocks. The high contents of W and Bi in the ores suggest the participation of a magmatic fluid. The absence of abnormal contents of Ni, Co, Sb, Mo, Cr, and Se indicates the redeposition of these elements from ore-bearing rocks, without their input by ore-forming fluids, which is confirmed by the isotopic composition of sulfide sulfur and the characteristics of carbonaceous ore material. The formation of deposits proceeded with a change in REE contents. All objects show similar trace-element patterns: The rocks are enriched in LREE and lack a Ce anomaly. The identical REE patterns of ores reflect their inheritance from unaltered late Permian deposits. It has been established that the ores formed under different redox conditions, mainly with the participation of a relatively oxidized fluid enriched in LREE of the hydrothermal system NaCl–H2O, with domination of Cl over F. The studies have shown that the host carbonaceous sedimentary complexes, which served as additional sources of precious and associated metals, played a crucial role in the formation of the Natalka and Pavlik gold deposits. Some of the ore elements in the unaltered deposits form their own minerals.

This paper presents induced-polarization (IP) data on a number of gold deposits and occurrences in the Magadan Region. Geophysical works are effective for the study of gold-quartz deposits of different morphological types (vein, veinlet-vein, and veinlet-disseminated). It is shown that multifrequency IP sounding reliably identifies zones of carbon metasomatism, a reliable indicator of promising gold mineralization areas and zones in northeastern Russia. Evidence of carbon metasomatism is the typical shape of phase frequency response curves for graphite and graphitized rocks.

We present new data on the structure and age of the upper Permian strata in the basin of the Setorym River (tributary of the Vostochnaya Khandyga River) in the South Verkhoyansk region, represented by the Imtachan Formation and the lower part of the Nekuchan Formation. Based on the new findings of bivalve fossils from the Intomodesma costatum Zone, as well as on the study of carbon isotopes in the shells and carbon isotopes of the organic matter of the host mudstones, we have for the first time proved the completeness of the Permian section. The detailed description of the contact between the Imtachan and Nekuchan Formations bears evidence for a certain continuity of the lithologic characteristics of the sandstones. The sharp lithologic contact between the formations reflects not a regional sedimentation hiatus but a shift of depositional settings from the upper parts of a delta to the deep shelf, caused by forced marine transgression. It is concluded that there was no long-term hiatus between the accumulation of the Imtachan and Nekuchan Formations. Images of the most characteristic species of bivalves and crinoids from the Imtachan Formation are presented.