N. A. Goryachev

The first detailed δ 13 С оrg record in Permo-Triassic boundary deposits in the Kolyma–Omolon region (Northeast Asia)

We have obtained the first detailed δ13Сorg record in Permian-Triassic boundary sediments in deepwater facies in Northeast Asia (Kolyma–Omolon region, Balygychan Basin). Our data show good convergence both with the Setorym River section (South Verkoyansk region), where the Permian-Triassic boundary has been determined approximately, and with a number of other sections of Permian-Triassic boundary sediments in the Boreal and Tethyan Superrealms, in particular, in the Buchanan Lake section in Arctic Canada, the Festningen section on Spitsbergen, the Wadi Shahha section on the Arabian Peninsula, and published sections in the Dolomites.

Ore-controlling thrust faults at the Bazovskoe gold-ore deposit (Eastern Yakutia)

This work presents results of structural analysis of the orogenic Bazovskoe gold-ore deposit, the structure of which is controlled by an imbricate fan with frontal succession of ore-controlling thrust faults and conjugated thrust ramps. It was established that linear and stratified stockworks and their combinations are formed by several systems of quartz veins and veinlets, regularly related to thrusting along the ore-controlling zones and interlayer shears. In addition, superimposed shear deformations are widely distributed. The features revealed of the geological structure of the Bazovskoe gold-ore deposit allow us to refine the prospecting and searching pattern developed for gold-ore deposits of the Verkhoyansk–Kolyma fold belt.

New data on the composition of jordanite–geocronite Pb–Sb–As sulfosalts at the Berezitovoe deposit (Upper Amur Region, Russia)

New data on the composition of jordanite–geocronite Pb–Sb–As sulfosalts in the vein–disseminated gold ore at the Berezitovoe deposit were provided. Within the studied quartz–sulfide sample, some grains of Pb–Sb–As sulfosalts, uniform in composition and azonal, are drastically different from each other in As and Sb contents forming a quasi-continuous range of solid compounds from jordanite to geocronite. Jordanite–geocronite minerals at the Berezitovoe deposit (relative to the Darasun deposit) are characterized by a higher Pb concentration with a low polymetal total. It is assumed that such typomorphic features of the composition of Pb–Sb–As sulfosalts are indicative of specific formation conditions of gold mineralization in polymetallic ores at the Berezitovoe deposit.

Mineral composition of gold-bearing veins and typomorphic features of their minerals in the Kirovskoe deposit (Upper Amur region)

A collection of quartz veinlets with ore mineralization sampled from the dumps of the abandoned pit of the Kirov mine was analyzed with defining the mineral assemblages productive for gold mineralization and determining the composition of the main ore minerals and their typomorphic features, which are used for interpreting the genesis of the mineral associations and the deposit as a whole.

Malinovka deposit—A new type of gold mineralization in Primorye, Russia: Geology, mineralogy, and genesis

Original data on the ore composition are obtained by studying samples from mining workings. In terms of mineral composition, gold-productive veinlets are subdivided into three types: sulfide–quartz, sulfide–carbonate–quartz, and sulfide. The wall-rock metasomatites and typomorphic features of the minerals are studied and the genetic problems of the ores and deposit are discussed. It is established that the Malinovka deposit is ascribed to the gold–tourmaline type (gold–quartz formation), which is identified for the first time in Primorye. In terms of many parameters, the ores of this type are close to those of the large deposits from the Transbaikalian and Amur regions (Klyuchevsky, Kariy, Kirov, Darasun, and others), which are genetically related to granitoid magmatism.

New Data on the Age of Gold Mineralization in the Southeastern Part of Eastern Sayan

This article presents new data on the age of the largest gold deposits in the southeastern part of Eastern Sayan. The dates have been obtained by Ar–Ar analysis of micas occurring in gold-bearing quartz veins and mineralized zones. The obtained Ar–Ar ages of fuchsite and sericite from the tectonized and mineralized zones of the Zun–Holba deposit (ore body Severnoye-3), range within 353.9–386.4 Ma; a similar result of 352.9 Ma was yielded by Ar–Ar dating of Cr–muscovite from mylonitized listvenite in the veins of the periphery of the Zun–Ospa gold deposit. However, muscovite from the ore-bearing quartz vein of the Pioneer gold–quartz deposit, located near Zun–Holba, has been dated to 421.9 Ma. The obtained new data on isotopic age of the gold–quartz ores and gold–sulphide–quartz deposits allow recognition of the Early Palaeozoic accretion–collision and the Late Palaeozoic shearing stages of formation of gold mineralization in the SE Eastern Sayan.

Slab Melt as a Potential Source of Profiling Elements of Gold and Heavy Metal Deposits

Spatial/genetic control by slab magma products at gold deposits is shown in this paper by the example of granitoids in the Ust’-Kara area of the Eastern Trans-Baikal Region. The investigation performed makes it possible to take a fresh look at the problem of metal sources in the East Trans-Baikal gold deposits and to relate their formation to material flow from the oceanic lithosphere in the subduction zone, material conservation within the subcontinental mantle, and possible remobilization under large tectonic reconstructions.

Minerals of the Bournonite–Seligmannite Series in Ore of the Beresitovoe Deposit, Upper Amur Region, Russia

New data are presented on segregations and compositions of bournonite-seligmannite series of minerals in gold-bearing veinlets of the Beresitovoe deposit located in the eastern part of the Mongolia–Okhotsk Orogenic Belt. It was established that these minerals represent a discrete series of stoichiometric solid compounds with As formula coefficients varying from 0.2 to 1.2. It is shown that minerals of this series are characteristic of ore deposits that undergo high-grade metamorphism, the P–T conditions of which are sufficient for melting of primary sulfides.

New results of U–Pb SHRIMP dating of zircons from upper Wuchiapingian (Upper Permian) deposits in northeastern Russia

The first results are presented for U-Pb SHRIMP-II dating of zircons from the upper part of the Khivachian regional horizon (stage) of the Regional Stratigraphic Scale (RSS) of the Permian in northeastern Russia. The obtained isotope age of 255 ± 2 Ma is close to that of the present boundary between the Wuchiapingian and Changhsingian stages of the Permian system in the International Stratigraphic Scale (254.1 Ma). Based on the distribution of bivalves—Intomodesma spp. and Claraioides aff. primitivus (Yin)—in the sections considered, their relations to the stratigraphic positions of the samples considered and dated formerly, and in view of the interregional correlation of recent δ13Сorg data for clayey rocks, one may assume with certainty that most of the regional zone of Intomodesma costatum corresponds to the upper part of the Wuchiapingian stage. Here, the Changhsingian stage in northeastern Asia complies only with the uppermost part of this zone within the I. postevenicum subzone and, partially, of Otoceras layers within the Otoceras concavum zone.

First discovery of high-mercury silver in ores of the Rogovik gold–silver deposit (Northeastern Russia)

New data on mercurial mineralization are presented, and a detailed characteristic is given for the first discovery of mercurous silver in ores of the Rogovik gold–silver deposit (the Omsukchan trough, Northeastern Russia). It was found that native silver in the examined ores occurs as finely-dispersed inclusions in quartz filling microcracks and interstitions. It also occurs in associations with kustelite, Ag sulfosalts and selenides, selenitic acanthite, and argyrodite. The mercury admixture varies from “not detected” in the central parts of grains to 0.22–1.70 wt % along the edges, or, in independent grains, to the appearance of Ag amalgams containing 10.20–24.61 wt % of Hg. The xenomorph form of grains of 50 μm or less in size prevails. It is assumed that the appearance of mercurial mineralization is caused by the superposition of products of the young Hg-bearing Dogda–Erikit belt upon the more ancient Ag-bearing Omsukchan trough.