The Geologic Features of the Occurrence of Copper in North America

Copper is of such widespread natural occurrence in North America and there are so few metal-mining districts that have not contributed to its production that it is obviously necessary in any brief general treatment of the geology of the copper deposits of the continent to restrict the discussion to the districts in which copper is the dominant metallic product. Otherwise the summary would be unreasonably long. The copper deposits of North America may be classified in various ways--with respect to form, genesis, geologic age, distribution, and distinctive features of character or occurrence. On the whole, an areal grouping will probably be most satisfactory. To some extent this will coincide with a classification based on the form or character of the deposits, but there will be notable exceptions. Classification, after all, is merely a human-expedient for systematizing description and for facilitating studies of origin. It is essentially artificial and sets up class distinctions, the legality of which, at least so far as ore deposits are concerned, Nature does not recognize

Copper mineral occurrences in the Wrangell Mountains-Prince William Sound area, Alaska

On January 9, 1970, the U.S. Bureau of Mines entered into an agreement with the University of Alaska based upon a proposal submitted by the Mineral Industry Research Laboratory. Under the terms of this agreement, the Laboratory undertook to compile information on copper occurrences in eight quadrangles covering what are loosely known as the Copper River, White River, and Prince William Sound copper provinces. If time permitted four other quadrangles would be added, and this has been possible. Information was to be obtained by searching published and unpublished records of the Bureau of Mines, the U.S. Geological Survey, the State Division of Geological Survey, the University of Alaska, and the recording offices

Minerals in Afghanistan : The Aynak Copper Deposit

The area around Aynak, 30 km south-south-east of Kabul in south-east Afghanistan, has been the focus of copper working since ancient times. Numerous old excavations and pits, as well as remains of smelting furnaces, have been discovered at Aynak and also nearby at Darband and Jawkhar. In 1974, Russian geologists prospected and mapped the Kabul area and rediscovered the Aynak, Darband and Jawkhar copper prospects. In 1974–1976 and again in 1978–1989, the Soviet Geological Mission conducted detailed exploration of Aynak, but this work ceased in 1989 with the withdrawal of Russian advisors, and the subsequent civil war halted any further work

Minerals in Afghanistan : the potential for copper

There are around 300 documented copper deposits, occurrences and showings in Afghanistan as shown in Figure 1. A variety of styles of copper mineralisation occur in rocks ranging in age from Proterozoic to Neogene. These include sediment-hosted, skarn, porphyry, and vein-hosted, as well as other types. The largest and best-known copper discovery in Afghanistan is the world-class Aynak stratabound deposit hosted within Vendian-Cambrian quartz-biotite-dolomite metasedimentary rocks 30 km south-south-east of Kabul. Soviet surveys in the 1970s and 1980s indicated resources of 240 Mt at 2.3 % Cu. However, Afghanistan has yet to be evaluated in the light of modern mineral deposit models and improved analytical methods. From a global perspective, Afghanistan is relatively under explored and the potential for further discoveries of copper and other minerals is high. A summary of the potential for copper in Afghanistan is shown in Table 1

Ball milling as an effective route for the preparation of doped bornite: synthesis, stability and thermoelectric properties

Bornite, Cu5FeS4, is a naturally-occuring mineral with an ultralow thermal conductivity and potential for thermoelectric power generation. We describe here a new, easy and scalable route to synthesise bornite, together with the thermoelectric behaviour of manganese-substituted derivatives, Cu5Fe1-xMnxS4 (0 ≤ x ≤ 0.10). The electrical and thermal transport properties of Cu5Fe1-xMnxS4 (0 ≤ x ≤ 0.10), which are p-type semiconductors, were measured from room temperature to 573 K. The stability of bornite was investigated by thermogravimetric analysis under inert and oxidising atmospheres. Repeated measurements of the electrical transport properties confirm that bornite is stable up to 580 K under an inert atmosphere, while heating to 890 K results in rapid degradation. Ball milling leads to a substantial improvement in the thermoelectric figure of merit of unsusbtituted bornite (ZT = 0.55 at 543 K), when compared to bornite prepared by conventional high-temperature synthesis (ZT < 0.3 at 543 K). Manganese-substituted samples have a ZT comparable to that of unsubstituted bornite

Sulfide breccias from the Semenov-3 hydrothermal field, Mid-Atlantic Ridge: authigenic mineral formation and trace element pattern

The aim of this paper is the investigation of the role of diagenesis in the transformation of clastic sulfide sediments such as sulfide breccias from the Semenov-3 hydrothermal field (Mid-Atlantic Ridge). The breccias are composed of marcasite\u2013pyrite clasts enclosed in a barite\u2013sulfide\u2013quartz matrix. Primary hydrothermal sulfides occur as colloform, fine-crystalline, porous and radial marcasite\u2013pyrite clasts with inclusions or individual clasts of chalcopyrite, sphalerite, pyrrhotite, bornite, barite and rock-forming minerals. Diagenetic processes are responsible for the formation of more diverse authigenic mineralization including framboidal, ovoidal and nodular pyrite, coarse-crystalline pyrite and marcasite, anhedral and reniform chalcopyrite, inclusions of HgS phase and pyrrhotite\u2013sphalerite\u2013chalcopyrite aggregates in coarse-crystalline pyrite, zoned bornite\u2013chalcopyrite grains, specular and globular hematite, tabular barite and quartz. The early diagenetic ovoid pyrite is enriched in most trace elements in contrast to late diagenetic varieties. Authigenic lower-temperature chalcopyrite is depleted in trace elements relative to high-temperature hydrothermal ones. Trace elements have different modes of occurrence: Se is hosted in pyrite and chalcopyrite; Tl is related to sphalerite and galena nanoinclusions; Au is associated with galena; As in pyrite is lattice-bound, whereas in chalcopyrite it is related to tetrahedrite\u2013tennantite nanoinclusions; Cd in pyrite is hosted in sphalerite inclusions; Cd in chalcopyrite forms its own mineral; Co and Ni are hosted in chalcopyrite

Optimum transportation systems to serve the mineral industry north of the Yukon basin in Alaska

In 1972 the U. S . Bureau of Mines awarded a grant (No. G 01 22096) to the Mineral Industry Research Laboratory, University of Alaska, for a research project to determine optimum transportation systems to serve the mineral industry north of the Yukon River basin in Alaska. The study was conducted during the period May 1 - November 1, 1972. The study assesses the mineral potential of the region and selects two copper deposits: a known one at Bornite, and a potential one on the upper Koyukuk River. Two possible mining sites within the extensive coal bearing region north of the Brooks Range are also selected. A computer model was developed to perform an economic analysis of technically feasible transportation modes and routes from these four sites to Alaskan ports from which minerals could be shipped to markets. Transport modes considered are highway, rail, cargo aircraft, river barge, winter haul road and air cushion vehicles (A.C.V.). The computer program calculates the present worth of tax benefits from mining and transportation and revenues based on the value of minerals at the port, as well as the auxillary benefits derived from the anticipated use of the routes by the tourist industry. Annual and fixed costs of mining and transportation of minerals are calculated, and benefit-cost ratios determined for each combination of routes and modes serving the four mineral sites. The study concludes that the best systems in terms of a high benefit-cost ratio are those utilizing a minimum of new construction of conventional highways or railroads. The optimum system as derived from this study is one linking together existing transportation systems with aircraft or A.C.V. These modes are feasible only for the shipment of a high value product, namely blister copper produced by a smelter at the mining site, Of the several alternatives considered for the shipment of coal, only a slurry pipeline to an as yet undeveloped port on the Arctic coast showed significant promise. The study recommends that: 1. More government support should be given to mineral exploration in Alaska. 2. Potential mineral industry development should be considered in transportation planning at state and federal levels. 3. Additional research pertinent to mining and processing of minerals in the North should be conducted, and the feasibility of smelting minerals within Alaska explored. 4. Alternatives for providing power to Northwestern Alaska should be investigated

Ore geology of the copper sulfide mineralization in the Rudabánya ore-bearing complex

The mineralized complex of Rudabánya hosts deposits of several mineral resources including base metal ores. Recent exploration provided new information on the enrichment of copper within this complex. The primary copper mineralization consists of sulfides. The paragenetic sequence starts with fahlore, continues with bornite, and concludes in chalcopyrite formation partly replacing the former phases. It is hosted by brecciated carbonate rocks, overprinting the paragenesis of the iron metasomatism. It was found to be spatially separated from zinc and lead enrichments. Oxidation and a subsequent new pulse of mineralization formed several new copper, zinc, and lead minerals, probably by the remobilization of the primary parageneses

Concordant ages for the giant Kipushi base metal deposit (DR Congo) from direct Rb-Sr and Re-Os dating of sulfides

We report concordant ages of 451.1 ± 6.0 and 450.5 ± 3.4Ma from direct Rb-Sr and Re-Os isochron dating, respectively, of ore-stage Zn-Cu-Ge sulfides, including sphalerite for the giant carbonate-hosted Kipushi base metal (+Ge) deposit in the Neoproterozoic Lufilian Arc, DR Congo. This is the first example of a world-class sulfide deposit being directly dated by two independent isotopic methods. The 451Ma age for Kipushi suggests that the ore-forming solutions did not evolve from metamorphogenic fluids mobilized syntectonically during the Pan-African-Lufilian orogeny but rather were generated in a Late Ordovician postorogenic, extensional setting. The homogeneous Pb isotopic composition of the sulfides indicates that both Cu-Ge- and Zn-rich orebodies of the Kipushi deposit formed contemporaneously from the same fluid system. The sulfide Pb isotope signatures in combination with initial 87Sr/86Sr and 187Os/188Os ratios defined by the isochrons point to metal sources located in the (upper) crust. The concordant Re-Os and Rb-Sr ages obtained in this study provide independent proof of the geological significance of direct Rb-Sr dating of sphalerit

Petrological Conditions Associated with Gold Deposition at Browns Creek Skarn, Australia

Browns Creek is a skarn that hosts an Au-Cu ore deposit in the Blayney region of New South Wales, Australia. Skarn rock at this location is wollastonite marble, highly mineralized by sulfides and gold deposited as native Au, electrum, telluride minerals and within arsenopyrite crystals. Related alteration includes metasomatized hornfels of the Ordovician Blayney Volcanics and marbleized interbedded limestone lenses of the Cowriga Limestone Member. Magmatic fluids responsible for this alteration were derived from a Silurian felsic-intermediate multi-phase intrusive system, the Browns Creek Intrusive Complex. Main constituents of this intrusive system include the Carcaor Granodiorite, the first and largest phase responsible for main pluton emplacement and skarnification of country rock, and the Mine Dyke Group, which is a smaller and more felsic phase attributed to carrying the ore-bearing fluids deposited at Browns Creek. As a small mine that is no longer operational, Browns Creek offers an example of an economic deposit that has not been thoroughly studied. This honors thesis aims to use petrological and geochemical analyses to better understand the conditions associated with gold deposition at Browns Creek by focusing on host rocks and metallic minerals deposited outside of the primary ore zone. polished blocks and thin sections were prepared for petrographic and microprobe analysis in order to more fully comprehend mineralogical processes occurring here, and supporting evidence was found for striking results presented by the most recent study on this site. These results include the assignment of Browns Creek as a skarn-hosted ore deposit resulting from a magmatic event post-alteration rather than a true skarn deposit, in addition to the re-dating of Browns Creek Intrusive Complex—presenting a Silurian age ~15Ma older than previously understood. These notable distinctions are investigated here through different approaches than previously explored. Additionally, links are proposed between Browns Creek deposit characteristics and tectonic regime, assigning primary Au-Cu ore deposition to a Silurian volcanic arc environment while suggesting that anomalously occurring Sn mineralization is the result of a later Devonian event within a rifting environment