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The long-term stored tailings of the ore concentration of pyrite-polymetallic ore deposits are an ideal natural laboratory in which it is possible to study the gold transformation from primary ores to supergene with superimposed anthropogenic characteristics. The typomorphic characteristics of native gold are studied on the example of technogenic-mineral formations (TMF) of the Novo-Ursk, Belokluch and Zmeinogorsk deposits (Western Siberia). The grain size distribution of gold and its concentration, morphology, internal structure and chemical composition shows the features of gold conversion in the processes of dissolution, migration and secondary deposition at geochemical barriers.As a result of a typomorphic analysis, external and internal signs were identified that prove that gold underwent supergene transformations directly in the body of the technogenic tailings. The growths and accumulations of nano- and microsize gold, the formation of particles of aggregate structure, lamination, fine particles and veinlets, openwork edges, as well as the absence of physical damage on the surface of the golds, confirm the active mobility of gold at the scales of tailings and emphasize the complex nature of multi-stage processes of gold mobilization.The gold formation of different chemical composition in TMF is explained by specific physical and chemical conditions for the section of the mound of stored waste, different sources of primary gold and geochemical barriers. Au(S2 O3 )n (1-2n) and Au(HS)2 – are the main complexes responsible for the mobility of gold. Gold of low and medium fineness is formed from thiosulfate complexes, whereas high-fineness gold is formed from hydrosulfide complexes.

Typomorphic features of placer gold of the Anabar region were studied as predictive-exploration criteria. The target of the study was to determine the typomorphic features of placer gold related to the intermediate sources (paleo-placers) and the supposed nearby primary ore occurrences. Two varieties of placer gold were identified. The first variety is well-rounded high-fineness lamellar gold with a highly modified internal structure. This native gold is associated with intermediate sources, Neogene–Quaternary watershed pebble beds. The second type includes slightly rounded gold with a wide variation in fineness (494‰–999‰). Its indicator is a block heterophase internal structure. The set of typomorphic features of this variety of placer gold indicates the vicinity of the primary source, what was the prerequisite for constructing prospecting traverses in order to find ore occurrences. As a result of these studies, hydrothermal-metasomatic formations with gold-sulfide mineralization were identified. The main primary substrate for them is fractured near-fault carbonate rocks of the Cambrian and Vendian–Cambrian age. Along with this, hydrothermalites developed on slightly cemented fine-pebble quartz conglomerates of the Middle Permian age were found in the core of exploration wells. Two types of metasomatic rocks are identified: quartz-potassium feldspar and jasperoid. The main ore minerals were galena and pyrite, different ratios by sites were revealed. Gold was identified in the form of small particles in the carbonate and siliceous substrate of hydrothermal-metasomatic formations. The lithological factor was one of the leading favorable factors for the ore formation due to the presence of near-fault highly permeable fractured carbonate and slightly cemented terrigenous rocks. The structural control of the studied ore occurrences is determined by their localization in the Mayat–Logoy and Dogoy–Kuoy faults of the Molodo–Popigay system of discontinuous faults. We assume a two-stage formation of the gold ore occurrences: during the first stage, the ore components in the form of primary hydrothermal-sedimentary ores in the near-gault zones were formed. The second stage was related to the processes of the Mesozoic tectonic-magmatic activation, when the intrusion of basite dikes initiated the mobilization of ore components the gold-sulfide occurrences were formed in the near-fault zone as a result of silicic-potassic metasomatosis of the carbonate and terrigenous rocks. [ABSTRACT FROM AUTHOR]

Analysis of the evolution of bauxite-bearing weathering crust in the geological history of Asia, as well as detailed mineralogical-geochemical and hydrogeochemical studies, has made it possible to consider supergene infiltration metasomatism as a single mechanism for the formation of the eluvial zonal profile, using the weathering crust of southern Vietnam weathering crust as an example. It is established that all weathering crust zones develop simultaneously throughout the existing fracturing as rocks interact with the solutions percolating through them. All supergene minerals are formed directly from original parent rock components rather than by staged development at each other's expense. The resulting paragenetic assemblages of newly formed minerals result in zoning. [ABSTRACT FROM AUTHOR]

Diamond crystals with graphite inclusions synthesized during the experimental modeling of natural diamond formation in chloride and carbonate systems under mantle PT-conditions were studied to elucidate the specifics of the protogenetic graphite inclusions. It has been established that the inclusions of graphite, both primary ones and those resulted from sodium oxalate decomposition, form compact clusters of grains and plates of different shapes in diamond. Diamonds rich in graphite inclusions are black and opaque. Their distinctive feature is significant low-frequency shift (to 1328 cm - 1 ) and broadening (to 6.5 cm - 1 ) of the Raman line, testifying to high residual deformation. Based on the data of previous experiments and the results obtained in this study, we consider peculiarities of protogenetic, syngenetic, and epigenetic graphite inclusions in diamond and their possible use as typomorphic features for the investigation of natural diamonds and reconstruction of their genesis. [ABSTRACT FROM AUTHOR]

Abstract: The formation conditions of placers within the Tapsa–Kaakhem gold zone (Tuva) have been determined, and the relation between primary and placer gold deposits has been studied. Polycyclicity in the valleys of the region resulted in the formation of gold placers of various morphologies with stratified producing reefs in loose sediments differing in composition and age: Oligocene–Lower Pliocene, Eopleistocene–Lower Pleistocene, Middle Pleistocene, and Upper Pleistocene. A complex relation between placers and their primary sources has been established. In general, the macrocomposition of gold in the producing reefs of different ages reflects the composition of gold from the primary sources. From older to younger producing reefs, gold fineness varies more widely, showing a trend toward smaller values. This suggests that undiscovered primary sources belonging to another association exist in the source area. The same is confirmed by a drastic change in the typomorphic features, grain size, and roundedness of gold in the longitudinal section of the Bai-Syut River valley. The peculiarities of gold from placers formed by the rewashing of glacial drift have been established. In the Kopto placer, nuggets are widespread (10 mm), which fully retained the shape inherent to vein gold. Apparently, the nuggets were transported to the placer with glacial drift in quartz gravel, which protected them from rounding. Quartz crumbled completely, and gold became free in situ under frost action. The presence of nuggets in the Kopto placer permits predicting a cluster distribution of gold in the known thin quartz veins. [ABSTRACT FROM AUTHOR]

The typomorphic features of modern oceanic massive sulfides are established in comparison with ancient continental deposits of a similar origin on the basis of data accumulated for 17 years. The typomorphic mineralogical features of the objects under consideration are also established with regard to the substratum composition and the maturity of hydrothermal sulfide mounds. The results add to our knowledge of mineral substances at early stages of development. [ABSTRACT FROM AUTHOR]