Ore mineralogy and mineral chemistry of quartz-chalcopyrite veins from the Krusha ore occurrence, Western Srednogorie, Bulgaria

The Krusha ore occurrence is located in the western part of the Srednogorie zone. The quartz-chalcopyrite veins are hosted by altered basaltic andesites. The styles of alteration are propylitic, sericitic, argillic and advanced argillic. The ore veins consist mainly of chalcopyrite, quartz and carbonates. Native copper is observed as single grains. Chalcopyrite is with high contents of Se. Au is up to 3.13 ppm with average contents of 1.43 ppm.

Michigan International Copper Analogue (MICA) project – current status

One of the key requirements for the deep geological disposal of high-level nuclear waste is the assessment of its long-term performance and safety (up to 1 Ma). Regarding engineered barrier system materials, such as copper, much of the data available comes from short-term investigations, such as laboratory experiments at different scales. Copper is an important part of many waste packaging and disposal concepts, e.g. KBS-3 developed in Sweden and Finland and Mark II developed in Canada. Natural analogues provide another important way of obtaining understanding on potential repository system behavior. Observations made from the geological systems can be utilized in the safety case, providing information on the assessment time scale. Copper analogue studies (both natural analogues and archaeological analogues) have been reported in the literature and they have been extensively reviewed by various authors (e.g. Miller et al., 2000) and by safety case projects (e.g. Reijonen et al., 2015) within waste management organizations. So far, only a few studies have focussed on the general stability of native copper within its natural media (e.g. Milodowski et al., 2000; Marcos, 2002). Keweenaw native copper occurrences (Lake Superior, USA) have been mentioned as a qualitative source of information (e.g. in Miller et al., 2000); however, data to be used in process-based safety assessments for geological disposal are lacking. These deposits have been mined for a long time and there is a great deal of knowledge related to them as well as samples collected, but no formal review has been made from the geological disposal point of view. The native copper at the Keweenaw area reflects various geological environments from bedrock to sediment and even anthropogenic mine site remnants and geochemical environments (e.g., anoxic vs. oxic, sulphur-free vs. sulphur-bearing). It thus provides a unique complementary data source that will be useful for estimating processes governing behavior of metallic copper. The MICA project phase I systematically collects and reviews the existing literature and data on the Michigan copper analogue sites and available sampling potential. Here, we present the current status of the project.

Distribution of sulfides and PGE minerals in the picritic and taxitic gabbro-dolerites of the Norilsk 1 intrusion

ABSTRACT Disseminated ores in the Norilsk 1 intrusion were studied to elucidate the typomorphic features of sulfides and noble metal mineralizations in picritic and taxitic (or lower olivine) gabbro-dolerites. The former are characterized by the development of a low-sulfur sulfide association (troilite, Fe-rich pentlandite, talnakhite, chalcocite, native copper) while the latter exhibits a high-sulfur association (monoclinic pyrrhotite, Ni-rich pentlandite, pyrite, heazlewoodite). The contact between these types of rocks is geochemically and mineralogically contrasting. The mineralogical and geochemical zoning directed from the roof to the base of each layer is expressed by an increase in the Cu content (and chalcopyrite) in ores, an increase in the concentration of Ni in pentlandite and S in pyrrhotite in line with a decrease of the crystallization temperature, and an increase in sulfur fugacity in the same direction. Zoning of Pd(Pt) mineralization in picritic and taxitic (olivine) gabbro-dolerites is uniform and characterized by the distribution of Pd-Sn compounds in the upper parts (together with Pd-Pb minerals in picritic rocks) and Pd-As compounds in the lower parts of the sections according to a drop in temperature. Such reverse zoning contradicts the typical mechanism of differentiation by fractional crystallization, and possibly suggests a fluid-magmatic nature. Mineralogical and geochemical features in platinum group element-Cu-Ni-bearing rocks are consistent with the idea that different stages of multi-pulse intrusions of mafic-ultramafic magmas with different compositions formed the picritic and taxitic gabbro-dolerites of the Norilsk region.

Mineralogical-geochemical features of magnetite occurrences in serpentinites of the Kalkan area (Main Uralian fault zone, South Urals)

Chemical and mineralogical composition of magnetite occurrences from serpentinites of the Kalkan melange area of the Main Uralian Fault zone (South Urals) are studied. Abundant Cu minerals including native copper, Cu sulfdes (covellite, bornite, minerals of the chalcocite-digenite series), chlorides (nantokite), Cu carbonates and Cu silicates are found in magnetite ores. Magnetite also contains abundant inclusions of cobaltpentlandite, rare Ag and Bi sulfdes, heazlewoodite and awaruite. All magnetite occurrences host relicts of chromites, the composition of which (moderate to high Cr / (Cr + Al) values) indicates a strong depletion of a peridotite protolith, which formed in the upper mantle below a forearc basin. A two-stage formation model of magnetite occurrences is suggested. At an early stage, the disseminated magnetite with inclusions of Cu-Fe-Co sulfdes formed under the infuence of metalliferous fuids in serpentinized ultramafc rocks at the bottom of the oceanic basin. During collision, serpentinites were tectonized with the formation of small bodies of massive magnetite ores and Cu, Ag and Bi sulfdes and native minerals.

Evolution of Furnaces

A new generation of industrial melting furnaces has been developed during the last 25 years. Present practices followed in Furnaces are discussed in this paper. Through a literature review account of various practices presently being followed in industries using Furnaces has been carried out with a view to gather principal of working. Apart from this a pilot study has also been carried out in few industries in India. We provide some recommendations for the productivity improvement. Due to lack of proper instruments the effect of the ill practices cannot be precisely judged. If this is properly measured, the percentage of productivity improvement in steel melting Furnace can be calculated. The review is carried out from the literature in the various journals and manuals. The first controlled use of fire in metallurgy dates from the eighth millennium ВС, when native copper was deliberately heated to form artifacts. Problems how to distinguish between native copper and smelted copper are addressed, especially what concerns the role of iron in copper. kilns. Metallurgy is an independent development. The decisive factor was the introduction of charcoal that was important to produce reducing conditions during firing. The earliest stages in metallurgy are represented by a non-slagging process. Reduction of ores was carried out in crucibles as exemplified by finds from Anatolia, Iran, Jordan, and the Iberian Peninsula. Special attention is paid to the putative early stages of metallurgy claimed to exist at that age. The is called Neolithic and Chalcolithic copper smelting there is critically prooved in the light of radio carbon data. Wind-powered furnaces played a major role in Early Bronze Age copper metallurgy, as exemplified by sites in the Feinan-area, in Wadi Dara, Egypt, and at numerous sites in the Aegean. Later, artificial air supply by bellows and tuyeres was introduced.

GEODYNAMICS

Purpose. The main purpose of this paper is to investigate the peculiarities of the spatial distribution of thickness and paleorelief of continental flood basalts of Luchychi stratum of Ratne suite of the Ediacaran of the Ratne–Kamin-Kashyrskyi Area in Western Volyn using maps of the thickness and relief of the paleosurface. The study also focuses on correlation between the specified parameters of the stratum and the spatial change of concentrations of native mineralization and its localization relative to the roof (sole) of the stratum. Method. The research applies a number of methods, including field geological surveys; petrography of basalts, structural features (degree of crystallization of mesostasis, structural position of minerals and, in particular, copper, ratio of globular formations and minerals that surround them, relationship between globules), macro- and microtextural features of rocks; geochemical research: determination of the content of the main chemical components of the rocks by the method of gross chemical analysis and copper content; geological and morphostructural studies: construction of a map of paleorelief and thickness of continental flood basalt of the Luchichiv stratum (according to the section of wells). Results. The constructed maps of the thickness and paleo surface of the Luchychi stratum show the spatial variability of the basalt thickness and the reflection of the effective tectonic situation on its paleo surface, which can be "read" by relief elements. It is established that high copper content in basalts is spatially confined to areas of maximum thickness and shifted vertically to the near-roof and, partially, plantar parts of the basalt thickness, and the degree of their crystallization increases in the direction of the inner parts of bodies. This situation with the spatial arrangement of native mineralization indicates the existence within these areas of local isolated thermostated systems. They evolved in their internal parts in conditions close to the intrusive ones (relatively slow decrease in melt temperature, crystallization of rock differences almost devoid of volcanic glass – dolerite-basalts with the transition to dolerites in the central part). Such physicochemical conditions caused long-term migration of gaseous, gaseous-liquid and liquid fluids, providing concomitant extraction, concentration, transfer and deposition not only of native copper, but also a number of petrogenic oxides (alkalis, iron, partially calcium, silicium). The latter subsequently formed a number of low-temperature minerals, the most common of which are zeolites, calcite, and iron compounds. In areas with small and minimum thickness of basalts, the above facts are observed in a reduced form, and in some places are virtually absent. The research has established the complete absence of signs of hydrothermal copper ore mineralization. The latter indicates the lack of evidence about the formation of native mineralization of the hydrothermal type. We provide the geological and petrogeochemical facts that give grounds to consider the scenario of the process of formation of native copper mineralization in relation to the fluid-liquidation hypothesis, earlier developed and proposed by the authors. Scientific novelty. For the first time, the study made it possible to construct maps of the thickness and relief of the paleo surface of the basalts of the Luchychi strata of the Ratne–Kamin-Kashyrskyi area of Western Volyn. Based on the actual material it is shown that the vertical distribution and localization of native mineralization within basaltic bodies are naturally related to their thickness. The value of native copper is directly related to body thickness, reaching a maximum in areas with maximum thickness and background values at the minimum thickness. Practical significance. For the first time, geological, petrographic, geological and morphostructural data were compared with the copper content in basalts of the Luchichi stratum. The proposed approach can be used by geological production organizations in conducting exploration work to prepare promising areas for exploration of the North-Hirnyky and Rafalivka ore fields (ore nodes) within the Ratne Horst anticline. The obtained original material can be distributed as a new method of native mineralization search in other areas of the continental flood basalts distribution.

Lead Isotope Analysis of Geological Native Copper: Implications for Archaeological Provenance Research in the North American Arctic and Subarctic

The Indigenous inhabitants of Arctic and Subarctic North America had been using native copper for several centuries prior to sustained interaction with Europeans beginning in the 18th century. The connection, if any, between the use of copper in these two adjacent regions is, at present, unclear. The ability to determine the source of native copper artifacts found in greater northwestern North America would inform on the movement of copper via trade and exchange between, and aid in understanding the innovation and diffusion of native copper metallurgy among, ancestral Dene and Inuit People. This paper provides the results of a Lead Isotope Analysis (LIA) pilot study examining Pb isotope ratios of native copper samples from multiple locations in the northern regions of North America. The results from this preliminary study indicate some overlap in Pb isotope ratios between Arctic and Subarctic sources of native copper, and these nonetheless record distinct isotope signatures relative to those associated with other North American native Cu deposits.

Arsenical native copper from Au-Cu porphyry Ak-Sug deposit, Eastern Tyva

The geology of the Ak-Sug Au-Cu-porphyry deposit in the eastern Tyva is considered. The distribution of native copper in ores of the deposits was studied. It has been established that the native copper is of both hypogene and supergene origin. The hypogene native copper is characterized by an elevated arsenic content (up to 4.4 %) and occurs in association with copper arsenides, native silver, zircon, brannerite, xenotime-(Y), florensite-(Ce), chalcocite, and berzelianite. Hypogene native copper is confined to ore schistosity zones .