Determination of Abrasiveness in Copper-Gold Sulfide Ores: A Contribution to the Geometallurgical Model of the Sossego Deposit

The geological context of this study is established in the iron oxide-copper-gold (IOCG) deposit of Sossego (Canaã dos Carajás, Brazil), where hydrothermal alterations in shear zones concentrated the metals of interest and added new characteristics to the metavolcanic-sedimentary and granite rocks. The mineral transformation of rocks by hypersaline fluids enriched in metals and silica also modifies some metallurgical properties, such as abrasiveness. Special bench tests on rock drill cores are used in mapping the abrasiveness of rocks, with the Bond abrasion test being more commonly used in the mining industry, but it has a restrictive sampling protocol and mass requirement for geometallurgical studies. As a counterpoint, the test of the Laboratoire Central des Ponts et Chaussées/Central Laboratory of Bridges and Roads (LCPC) requires a smaller amount of fine material and a finer granulometric range. The study on the use of LCPC was implemented in 40 samples, using Bond Ai as a reference. The results showed a strong correlation between both methodologies (R2 = 95%), validating the use of LCPC to quantify abrasiveness in the Sossego mine. It was also possible to classify the most abrasive lithologies.

Stratigraphic-lithological factors of the location of gold mineralization in the central part of the Bukantau Mountains in Uzbekistan

The leading role in the placement of gold mineralization in the Bukantau mountains belongs to structural and lithological factors. For gold-ore and gold-silver occurrences, sandy-shale strata of the flyschoid and olistostrome formations are favorable, then, rocks of the volcanogenic-dolomite-siliceous formation and then the carbonate formation (Okzhetpes type). The leading types of near-ore hydrothermal alteration of the host rocks in the studied deposits are silicification and, to a lesser extent, carbonatization and sericitization. They are accompanied by chloritization, biotitization, argillization, etc. Gold ore deposits and ore occurrences of sulfide-disseminated ores are confined mainly to the deposits of the Karashakh suite of the Middle Carboniferous (C2b + m1 kr). Moreover, gold-sulfide mineralization in the rocks of the Karashakh Formation is unevenly distributed.

DEVELOPMENT OF METHOD TO ASSESS SEPARATION PROCESS TAKING INTO ACCOUNT RHEOLOGICAL PROPERTIES OF MINERAL SLURRY

This article considers the possibility of developing a methodology for assessing the separation process of gold-sulfide raw materials, taking into account the rheological characteristics of the mineral suspension. The object of the study is the ore of the Mayskoye deposit, which is subjected to fine crushing followed by cyanidation, so the consideration of rheological properties is the most important aspect of achieving the necessary enrichment performance. In the course of the research, using the object-oriented programming language Python 3.8, a program for calculating the empirical coefficients of the three-component rheological equation was developed. The resulting equation is the determinant for the shear stress within the suspension as a function of the velocity gradient. The developed program has been used to calculate coefficients of rheological equations for three variants of solid concentration in feed which correspond to the minimum, average and maximum for hydrocyclone used in the research (400 g/l, 500 g/l and 700 g/l respectively). Then, using the Ansys Fluent software, the multiphase classification modeling problem in the hydrocyclone was solved, resulting in shear rate profiles in the cross-section of the apparatus, from which the conditions necessary for the suspension to reach a fully dispersed state were concluded. It was determined that solid concentration 400 g/l is the optimum value that ensures maximum dispersion of the mineral slurry.

Metamorphic Conditions and Raman Spectroscopic Carbonaceous Material Thermometry of Host Schists of Olympiada and Eldorado Gold Deposits (Yenisey Ridge, Russia)

Metamorphic processes play a key role in forming orogenic gold deposits. In this paper, we present new evidence that host schists of the two largest gold deposits of the Yenisey ridge (Russia) Olympiada and Eldorado underwent a single stage of metamorphism in contrast to surrounding blocks. This metamorphism is of moderate thermal gradient and belongs to the Barrovian type, which is typical for the collisional event in the time range 800–850 Ma. The new Ar/Ar age data presented in this paper and the review of magmatic and metamorphic events and ore-forming processes indicate that the most productive stage (gold-sulfide-quartz) correlates well in time with the regional metamorphism of the Barrovian type. This indicates that metamorphic processes can have a crucial role in forming gold deposits of the Yenisey ridge. Carbonaceous material thermometry indicates a wide range of obtained temperatures around 90–150 °C around the mean temperature for each sample. The highest temperatures are close to the peak metamorphic temperatures estimated by garnet-biotite thermometry.

The Internal Structure of Placer Gold of the North-East of the Siberian Platform as a Reliable Search Sign of Primary Sources

Typomorphic features of placer gold are carriers of the most important information necessary for the reconstruction of the history of the formation of placer and ore occurrences of gold and can be used as mineralogical criteria in the search for primary sources of placers. The study of these features is relevant for placer areas with unidentified gold sources, which include the territory of the north-east of the Siberian Platform. The internal structure of native gold is one of the most informative typomorphic features is. We studied the internal gold structures of modern placers and conglomerates of the Early Permian age in the north-east of the Siberian Platform. The purpose of the work: to identify the features of the internal structure of placer gold, depending on the chemical composition and the degree of its transformations, as well as the possibility of their use as a prospecting indicator. Structural etching of native gold was performed using the reagent: HCl + HNO3 + FeCl3 × 6H2O + CrO3 + thiurea + water. As a result of the research, it was found that the well-rounded high-grade gold of modern placers has undergone repeated redeposition through intermediate sources. The discovery of slightly rounded gold with an internal structure without signs of exogenous transformation indicates that it entered the modern alluvium from a nearby primary source. This was a prerequisite for setting up ore gold exploration, resulting in identification of apocarbonate hydrothermal-metasomatic formations with disseminated gold-sulfide mineralization were identified. Thus, the features of the internal structures of placer gold in combination with other typomorphic features are additional indications of determining the sources of formation of gold-bearing placers.

Secondary dispersion haloes in the gold-bearing weathering crust of the Vasilkovskoe gold deposit, Northern Kazakhstan

The formation conditions and characteristics of secondary dispersion haloes in the gold-bearing weathering crust of a gold-sulfide-quartz deposit are considered. The fraction < 0,1mm is demonstrated to be preferable for lithochemical prospecting for the Vasilkovskoe type gold mineralization. The secondary dispersion haloes of gold, identified based on analyses of this fraction, are characterized by the maximum size and productivity.

Gold metallogeny of the East Tannu-Ola ore region, Tyva Republic

The Elegest-Mezhegei, Aptara, and Shivilig forecasted gold ore clusters and the Kharalyg and Irbitei forecasted gold-silver-polymetallic ore clusters were distinguished within the East Tannu-Ola iron-copper-polymetallic-gold ore region, based on examination of historical and new geological, geochemical, and metallogenical data. Subsequently, the Urgailyg, Proezdnoe, and Chumurtuk forecasted gold ore fields were delineated within the Elegest-Mezhegei cluster; the Despen ore field was delineated within the Aptara ore cluster; and the Ovur-Ongesh ore field was outlined within the Shivilig cluster. In addition, the Ulug-Sailyg and Ak-Charinsk gold-molybdenum-copper ore fields were distinguished outside the ore clusters. The article summarizes the investigation history, geological-structural position, geological features, and geochemical specialization of the rocks of the East Tannu-Ola region. Descriptions of the ore clusters embrace peculiarities of their geological structure, ore mineralogy, and native gold, as well as parameters of the gold-sulfide-quartz, goldskarn, gold-containing polymetallic VMS, and porphyry molybdenum-copper mineralized zones. The conclusions highlight the metallogenic epochs and distribution regularities of the gold and gold-containing mineralization within the region studied.