The paper explores the applicability of the Kohonen clustering algorithm for peak detection during the preprocessing of mass spectra. Various modifications made to the algorithm’s classical version during its implementation in the program code are described . The results of peak detection carried out in four mass spectra of inorganic compounds using the Kohonen algorithm are presented. A brief study is conducted on how the algorithm’s output is affected by various parameter values. The Kohonen algorithm and two other approaches are compared in terms of their peak detection quality. The findings suggest that the Kohonen clustering algorithm can be used for the initial detection of mass spectrum peaks; however, certain peculiarities of the algorithm’s functioning need to be considered.

The distribution of index minerals of the hydrothermal arsenide process of the formation of Ni‒Co–As (±U–Ag), Co–S–As (±Au–W), and Cu–Co–As (±Sb–Ag) quartz–carbonate veins of deposits of the Bou Offro–El Graara ore belt (Morocco) are discussed. The Co arsenide objects of the Bou Azzer ore cluster with typical low-temperature Ni–Co–As (U–Ag) deposits of the five-element hydrothermal type are of special interest: El Jir, Mechoui, Tarouni, Central and East Bou Azzer, Aghbar, Tamdrost, etc. The ores of most of the studied deposits are strongly enriched in Co relative to Ni (Co/Ni ratio = 10/1), have high grades of Au (up to 100 g/t) and Mo (up to 0.1%) with relatively low Ag, Ni, and U contents. Based on the analysis of the interrelations of ore and gangue minerals, the sequence of the formation of mineral assemblages is identified and their mineralogical–geochemical zonation is studied. The range of the most favorable physicochemical parameters of ore deposition is determined from the fluid inclusions in the gangue minerals. The indicative role of mineralogical–geochemical features of ore assemblages is shown for the forecast and survey of blind ore bodies.

The Khovu-Aksy Ag–Bi–Cu–Ni–Co arsenide deposit discovered in 1947 was explored in detail by 1954. The Tuvakobalt Mining Complex mined veins cutting skarns in the Khovu-Aksy ore field and used hydrometallurgical process of ores to obtain bulk concentrate in accordance with the ammoniac–carbonate procedure in 1970–1991. During 20 years of operation, 12 000 tons of cobalt concentrate were produced; this concentrate was processed at the Ufaley plant to produce refined Co, Ni, Cu, and Ag. Huge adit dumps of barren material containing oxidized arsenides and sulfides were accumulated and more than 2 million cubic meters of hydrometallurgical wastes are dumped in six disposal pits on the industrial site. The retained cobalt reserves (more than 16 kt) and reserves in the disposal pits (more than 2.5 kt) are valuable critical minerals.

Проведено обобщение результатов изучения состава металлоносных флюидов собственно кобальтовых месторождений гидротермального генезиса, формировавшихся в различных геодинамических обстановках в связи со становлением щелочных и щелочно-базитовых интрузивов и даек. Для определения физико-химических параметров рудоотложения по флюидным включениям в минералах использовались как традиционные, так и новые инструментальные методы термобарогеохимии: термо- и криометрия, КР-спектроскопия; концентрации рудных и петрогенных элементов в индивидуальных флюидных включениях оценивались методом LA-ICP-MS. Полученные результаты послужили основой исследования, главной задачей которого являлось термодинамическое моделирование условий совместного переноса и отложения Co, Ni, Cu, Fe, Mg, Ca, Ag, Au, Bi, U, Pt и Pdc расчетом ряда равновесных состояний гидротермальной системы, по составу близкой к природным рудообразующим флюидам. Выявлены физико-химические факторы отложения самородных – золота, серебра, платины и палладия в рудах таких месторождений. Полученные данные могут послужить базой для разработки корректных генетических моделей рудообразующих систем собственно кобальтовых месторождений и содействовать решению проблем их поиска.

The paper reports generalized investigation data on the composition of metal-bearing fluids at hydrothermal cobalt deposits, which formed in different geodynamic settings during the development of alkali and alkali-basic intrusions and dikes. To determine the physicochemical parameters of ore deposition from fluid inclusions in minerals, both traditional and new instrumental thermobarogeochemical methods were used: thermometry, cryometry, and Raman spectroscopy; the concentrations of ore- and rock-forming elements in individual fluid inclusions were evaluated by LA-ICP-MS. The results served as the basis for a study focused on thermodynamic modeling of joint transport and deposition of Co, Ni, Cu, Fe, Mg, Ca, Ag, Au, Bi, U, Pt, and Pd; the number of equilibrium states of the hydrothermal system similar in composition to the natural ore-forming fluids was also calculated. The physicochemical factors of native Au, Ag, Pt, and Pd in the ores at such deposits were revealed. These data can be used to develop correct genetic models for the ore-forming systems of the cobalt deposits proper and to solve the problem of searching for them.

An important role of the early Neoproterozoic juvenile crustal growth in the formation of the Khangai group of Precambrian terranes in the Central Asian Orogenic Belt was demonstrated by the example of the Holbo Nur Zone of the Songin Block. Magmatic complexes of this zone correspond to different settings of the Early Neoproterozoic ocean: oceanic islands, mid-ocean ridges, intraoceanic island arcs, and turbidite basins. Obtained data on volcanic rocks and associated granitoids constrain a timing of the island-arc magmatic complexes, at least within the interval of 888–859 Ma. The comparison of structures of the Songino and Tarbagatai blocks of the Khangai group of terranes showed that they share many common features in their geology and evolution and may be united into the single Songino–Tarbagatai terrane. This terrane was formed owing to the Early Neoproterozoic (~800 Ma) accretion of the ocean island, spreading, island-arc, and turbidite complexes of the oceanic plate to a stable continental massif represented by the Early Neoproterozoic Ider Complex of the Tarbagatai Block. The involvement of the Dzabkhan terrane into a Khangai collage of terranes is constrained between the formation of the volcanic rocks of the Dzabkhan Formation (~770–755 Ma), which are unknown in the Songino–Tarbagatai terrane, and the Tsagaan-Olom carbonate cover (~630 Ma), overlying both the Dzabkhan and Songino–Tarbagatai terranes. It was proposed that the formation of the Precambrian terranes of the Central Asian Orogenic Belt began from the Early Neoproterozoic accretion to the Rodinia supercontinent. The fragmentation of the latter above a mantle superplume at the end of the Early Neoproterozoic spanned also the newly formed fold area. This led to the formation of terranes, which included both fragments of the Paleoproterozoic craton and Early Neoproterozoic structures. Subsequent amalgamation of these Precambrian crustal fragments into composite terranes possibly occurred at the end of the early Baikalian tectonic phase.

The paper reports original isotopic and geochemical data on Early Precambrian lavas in the Ozernaya Zone in Mongolia. According to their normalized trace-element patterns, the rocks are classified into the following groups: (1) rocks similar to N-MORB; (2) rocks similar to E-MORB; (3) basalts enriched in trace elements, with HFSE minima; and (4) basalts depleted in trace elements, with HFSE minima. All of the lava types could be produced in an island arc-backarc basin system. The magmatic rocks of group (1) were likely formed in a spreading backarc basin, and those of group (2) were likely generated within the influ- ence zone of a hotspot or were derived from heterogeneous upper mantle domains. The lavas of group (3) seem to be fragments of an ensimatic, relatively primitive island arc. The basalts and basaltic andesites of group (4) were likely produced by mixing melts of groups (1) and (3). The fact that lavas of groups (1) and (4) sometimes intercalate within a single stratigraphic section suggests that the extension and subduction zones were closely spaced and operated simultaneously. The magmas of groups (1), (2), and (3) were derived from different mantle sources, which possessed different ratios of trace elements and were different in isotopic composition.

Data on the composition, inner structure, and magma sources of giant batholith in the Central Asian Orogenic Belt are analyzed with reference to the Khangai batholith. The Khangai batholith was emplaced in the Late Permian–Early Triassic (270–240 Ma) and is the largest accumulations (>150000 km2) of granite plutons in central Mongolia. The plutons are dominated by granites of normal alkalinity and contain subalkaline granites and more rare alkaline granites. The batholith is hosted in the Khangai zonal magmatic area, which consists of the batholith itself and surrounding rift zones. The zones are made up of bimodal basalt–trachyte–comendite (pantellerite) or basalt-dominated (alkaline basalt) volcanic associations, whose intrusive rocks are dominated by syenite and granite, granosyenite, and leucogranite. Both the batholith and the rift zones were produced within the time span of 270–240 Ma. Although the rocks composing the batholith and its rift surroundings are different, they are related through a broad spectrum of transitional varieties, which suggests that that the mantle and crustal melts could interact at various scale when the magmatic area was produced. A model is suggested to explain how the geological structure of the magmatic area and the composition of the magmatic associations that make up its various zones were controlled by the interaction between a mantle plume and the lithospheric folded area. The mantle melts emplaced into the lower crust are thought to not only have been heat sources and thus induced melting but also have predetermined the variable geochemical and isotopic characteristics of the granitoids. In the marginal portions of the zonal area, the activity of the mantle plume triggered rifting associated with bimodal and alkaline granite magmatism. The formation of giant batholiths was typical of the evolution of the active continental margin of the Siberian paleocontinent in the Late Paleozoic and Early Mesozoic: the Khangai, Angara–Vitim, and Khentei batholiths were formed in this area within a relatively brief time span between 300 and 190Ma. The batholiths share certain features: they consist of granitoids of a broad compositional range, from tonalite and plagiogranite to granosyenite and rare-metal granites; and the batholiths were produced in relation to rifting processes that also formed rift magmatic zones in the surroundings of the batholiths. The large-scale and unusual batholith-forming processes are thought to have occurred when the active continental margin of the Late Paleozoic Siberian continent overlapped a number of hotspots in the Paleo- Asian Ocean. This resulted in the origin of a giant anorogenic magmatic province, which included batholiths, flood-basalt areas in Tarim and Junggar, and the Central Asian Rift System. The batholiths are structural elements of the latter and components of the zonal magmatic areas.

We consider mineral assemblages and mineralogical and geochemical peculiarities of hypogene gold from the Khaak-Sair multistage low-sulfide gold-quartz ore occurrence in listwanites. Three productive substages of Au- and Ag-mineral formation have been recognized on the basis of mineralogical studies: gold-sulfosalt-sulfide-quartz, gold-mercury-quartz, and gold-selenide-telluride-sulfide-quartz. These substages were characterized by the following sequences of mineral formation: (1) ultrahigh-fineness gold -> high-fineness gold -> argental gold (medium-and low-fineness gold) -> electrum + Ag-bearing and argental fahlores (up to 50 wt.% Ag) +/- acanthite +/- hessite; (2) high-fineness gold -> Hg-bearing and mercurian gold -> mercurian electrum -> mercurian kustelite -> Au-bearing mercurian silver; and (3) high-fineness gold -> mercurian gold -> mercurian electrum + naumannite + Te-bearing naumannite + fischesserite + tiemannite + hessite + coloradoite + Ag-bearing minerals of the galena-clausthalite series (up to 6 wt.% Ag) +/- Se-cinnabar +/- Se-imiterite. Productive mineral assemblages of the ore occurrence formed in the hypabyssal facies (depth similar to 1.5 km, P similar to 0.5 kbar) on the background of a temperature decrease from 290 to 160 degrees C and variations in f(O-2), f(S-2), f(Se-2), and f(Te-2). (C) 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.