Minor Arsenopyrite Research Articles

Strata-bound copper sulfide and nonstrata-bound arsenopyrite and base metal mineralization in the Caledonides of East Greenland; a review

In the central East Greenland Caledonides there are numerous occurrences of strata-bound copper mineralization and hydrothermal arsenic and tungsten mineralization. The host rocks are metasediments of middle Proterozoic and unmetamorphosed to slightly metamorphosed late Proterozoic sediments (quartzite, shale, limestone), all intruded by Caledonian granites.Strata-bound copper mineralization 0.2 to 2 m thick is found at different stratigraphic levels in late Proterozoic shale and quartzite and extends over a distance of 275 km. The mineral assemblages in the shale are dominated by chalcopyrite-pyrite, bornite-chalcocite, or chalcocite. The sulfide associations in the quartzite are chalcopyrite-pyrite-(pyrrhotite) or chalcopyrite-pyrite-(tetrahedrite). In addition strata-bound sulfide-bearing veins occur. The grade of the mineralized zones varies from 0.05 to 1.35 percent Cu. The strata-bound copper sulfides were probably concentrated mainly by diagenetic processes but later were modified by metamorphic mobilization and locally enriched by hydrothermal solutions.Hydrothermal scheelite and arsenopyrite mineralization is located mainly close to the border zone between the Central Metamorphic Complex and the late Proterozoic sediments.Three main types of scheelite mineralization occur: (1) a skarn type, (2) a vein type, and (3) a breccia type. The skarn type is hosted by marble, schist, and calc-silicate rocks. The tungsten content varies from 0.1 to 1 percent W with enrichment of the elements Be, Bi, F, Li, and Sn. Scheelite mineralization in quartz veins yields 0.1 percent W associated with enhanced contents of As, Be, Bi, F, Li, Pb, and Sn. The skarn and vein types are closely related to Caledonian granitic intrusions. The scheelite (+ or -stibnite) mineralized breccia type is found in fault zones probably connected with a granite. These occurrences contain 0.8 to 3 percent W and up to 2.4 Sb and represent at the moment the only mineral deposit of potential economic interest in the area.The arsenopyrite mineralization is regionally widespread. Mineralized quartz veins occur in both quartzitic and semipelitic sediments, whereas mineralized fracture zones are restricted to semipelitic quartzite. The arsenopyrite mineralization is often associated with scheelite, galena, pyrrhotite, chalcopyrite, sphalerite, and traces of gold and silver.The distribution of the elements in the scheelite and arsenopyrite mineralization indicates a zonation around the Caledonian granites. In general, elements such as Be, Bi, F, Li, and Sn are concentrated within 1 to 2 km from the contact. At a greater distance, up to 7 km, the metals Bi, Co, Cu, Pb, and Zn are typical. In terms of fluid inclusions in the veins, the homogenization temperatures of boiling CO 2 -bearing water of moderate salinity are from 225 degrees to 260 degrees C with a pressure of approximately 1 kb.

Native antimony and bournonite intergrowths in galena from the English Lake District

AbstractThe Driggith vein is representative of the lead-zinc mineralization in the Caldbeck Fells area, with a primary mineral assemblage consisting of quartz, baryte, calcite, chalcedony, pyrite, arsenopyrite, galena, sphalerire, bournonite, argentian tetrahedrite, and native antimony. Broadly similar assemblages are found in Pb-Zn mineralization of Upper Devonian to Permian age else-where in the Lake District. The paragenetic sequence appears to have been early pyrite and minor arsenopyrite associated with quartz; with later baryte, calcite, sphalerite, and chalcopyrite enclosed by galena. Within the galena occur inclusions of tetrahedrite, bournonite, and native antimony. A later stage of baryte mineralization was followed by the alteration of primary sulphides to secondary minerals. Elsewhere in the Lake District, galena occurring in this association also contains inclusions of native antimony, bournonite, and other sulphosalts, and in this respect differs from galena associated with earlier veins composed dominantly of chalcopyrite, pyrite, and arsenopyrite. The inclusions make a major contribution to the high antimony values reported in trace element analyses of galena from the Lake District. The occurrence of these inclusions, which in some cases display preferred orientation within the host galena, is discussed in terms of phase relations involving PbS and AgSbS2.

Multistage vein ores of the Lake City District, western San Juan Mountains, Colorado

Multistage vein ores of the Lake City District, western San Juan Mountains, Colorado

The mineralogy and chemical composition of the Woodlawn massive sulphide orebody

Abstract The main Woodlawn ore lens is a polymetallic, massive sulphide deposit’ with pyrite the major constituent, variable sphalerite, galena and chalcopyrite, and minor arsenopyrite, tetrahedrite‐tennantite, pyrrhotite and electrum. The silicate gangue minerals are chlorite, quartz, talc and sericitic mica. Other mineralization in the vicinity consists of footwall copper ore in chlorite schist and several smaller massive sulphide lenses. The predominant country rocks are felsic volcanics and shales, with abundant quartz, chlorite and mica, and talc in mineralized zones. An important textural feature of the massive ore is the fine compositional banding. Bands, which vary in thickness from a few tens of micrometres to several millimetres, are produced by variations in the sulphide content. Post‐depositional metomorphism and minor fracturing have only slightly modified this banding. Apart from the major element constituents—Pb, Zn, Fe, Cu and S—the ore is characterized by significant (100–1000 ppm) values...

Geology of the Bailadores, Venezuela, massive sulfide deposit

The Bailadores zinc-lead-copper sulfide deposit, located near the town of Bailadores in the southern Venezuelan Andes, represents a potentially large base metal occurrence. Originally it was perceived as a vein deposit, but the recent recognition of associated siliceous pyroclastic rocks and the stratiform nature of the sulfide mineralization suggest that it is a volcanogenic massive sulfide.The sulfides occur in the lower part of the Upper Paleozoic Mucuchachi Formation along the contact between an underlying basal pyroclastic unit, which unconformably overlies the Precambrian basement rocks, and overlying black phyllite, which is the dominant rock type of the Mucuchachi Formation. The volcanic rocks appear to form a local pile which interfingers with the overlying phyllite along its flanks.Associated with the mineralization are a chloritic quartzite and a chlorite-biotite-margarite schist, both of which are located in the footwall. The chloritic quartzite was possibly originally a pyroclastic rock which has been altered by silicification and sericitization and is similar to chlorite alteration pipes observed, for example, with some Archean massive sulfide deposits. The schist was probably a pelitic sediment, enriched in Mg, Ca, and Fe.The massive sulfide zone consists of sphalerite, pyrrhotite, galena, chalcopyrite, and minor arsenopyrite and pyrite. Gangue minerals include quartz, chlorite, and sericite. Disseminated mineralization associated with the massive sulfide zone includes pyrrhotite-sphalerite-galena with minor chalcopyrite in siliceous phyllitic rocks, usually in the immediate hanging wall or footwall, and pyrrhotite-chalcopyrite with minor sphalerite and galena in the footwall chloritic quartzite. Typical zoning is from lead-zinc in the upper massive zone to copper in the footwall.Rocks in the vicinity of the deposit have been sheared and metamorphosed. The Mucuchachi Formation has undergone general low-grade regional metamorphism, whereas the Bailadores area has been subjected to somewhat higher grade metamorphism with the development of garnet and the formation of pyrrhotite from the pyrite which is more typical regionally.The Bailadores deposit is interpreted to be a stratiform volcanogenic massive sulfide deposit based on the following criteria: (1) Sulfide mineralization is stratigraphically controlled. (2) Alteration within the pyroclastics and stratigraphically below the massive sulfides suggests that mineralization resulted from hydrothermal activity related to late-stage volcanism. (3) Fine interbanding of sulfides and pelitic sediments adjacent to the massive sulfide zone indicates contemporaneous emplacement in a marine environment. (4) Zoning of metals from lead and zinc in the massive hanging-wall zone to copper in the disseminated footwall zone is typical of many deposits of this type.

Oxygen reduction on sulphide minerals: Part III. Comparison of activities of various copper, iron, lead and nickel mineral electrodes

The cathodic reduction of oxygen was studied at rotated electrodes of the sulphide minerals arsenopyrite (FeAsS), bornite (Cu 5FeS 4), chalcocite (Cu 2S), chalcopyrite (CuFeS 2), covellite (CuS), galena (PhS), pentlandite ((Fe,Ni) 9S 8), pyrite (FeS 2) and pyrrhotite (Fe 1− x S) in both acid and alkaline solution. The working range of each mineral (i.e. the potential range over which background currents from surface processes are negligible) was determined from analyses of linear sweep voltammograms in deoxygenated solutions. In oxygenated solutions, minerals with wide working ranges give, at low rotation speeds, voltammograms that show limiting currents corresponding to the diffusion currents calculated from the Levich equation for a 4-electron reduction of oxygen to water. Departure from Levich conditions is observed at higher rotation speeds. This is simply a consequence of the inaccessibility of the limiting current region, and the extent of the departure depends on both the sulphide and the electrolyte used. Potential vs. log i plots in the kinetically-controlled region for each mineral give characteristic Tafel slopes, which show no systematic dependence on pH. In both acid and alkaline solutions there are significant differences between the oxygen reduction activities of the sulphides. The more active minerals pyrite, pentlandite, chalcocite and covellite are only slightly less active for oxygen reduction than gold. The ranking of activity of iron containing sulphides for oxygen reduction is consistent with their requirement for oxygen in flotation with xanthate collectors.

Aspects of metallogeny of Kyzylovskaya zone of folding (Western Kalba)

Extensive recurrent hydrothermal metamorphism, metasomatism, connections of the ores with the minor intrusions, tectono-magmatic considerations, and the fact that total gold content of pyrite, arsenopyrite, and other minerals, stable as it is, tends to increase further, with depth, suggest a high gold potential of the zone and its further exploration. —V.P. Sokoloff.

New Semiconducting Arsenopyrite-type Compounds

IN a recent paper1 we reported on semiconductivity in CoSb2-type compounds. The ternary analogues of these polycompounds are formed by the arsenopyrite group. The monoclinic minerals arsenopyrite, FeAsS, and gud-mundite, FeSbS, closely correspond to the mineral safflorite, CoAs2. They have the same number of valence electrons and we therefore expect their cations to have the same d-electron configuration. In CoAs2 we have found a magneton number much smaller than that corresponding to one unpaired spin1. A measurement of the magnetic susceptibility of a natural arsenopyrite crystal (from Altenberg, Silesia, the same on which resistivity measurements were performed earlier2) of unknown purity showed a very similar behaviour (see Table 1).

Cobalt mineralization in the Blackbird District, Lemhi County, Idaho

The cobalt mineralization in the Blackbird district of Lemhi County, Idaho, probably the most extensive mineralization of its kind in the United States, is confined to irregular and discontinuous veins and lodes along zones of fractured and schistose quartzite belonging to the Belt series (pre-Cambrian). These lodes are represented by (1) zones of cobaltite-impregnated tourmalinized quartzite (cobalt-tourmaline lodes); (2) zones of cobaltite-impregnated biotitized quartzite (cobalt-biotite lodes); (3) bodies of cobaltite-containing quartz in zones of cobaltite-impregnated biotitized quartzite (cobalt-quartz lodes); and (4) stringers and lenses of quartz and such ore minerals as cobaltite, native silver, chalcopyrite, gold, and electrum in zones of cobaltite-impregnated biotitized quartzite (gold-copper-cobalt lodes).These lodes are the products of three stages of mineralization: (1) an early cobalt stage during which biotite, tourmaline, and cobaltite were formed, (2) a copper-cobalt stage during which biotite, quartz, cobaltite, arsenopyrite, pyrite, pyrrhotite, native silver, chalcopyrite, siderite and other minerals were deposited, and (3) a gold-electrum stage during which scant amounts of these minerals and quartz were deposited. The differences that exist among the lodes depend largely on the variations in the amounts and kinds of minerals added during each stage of mineralization. All lodes show marked effects of the first stage of mineralization; the cobalt-quartz and the gold-copper-cobalt, also the effects of the second stage; and the gold-copper-cobalt lodes, mild effects of the third.The mineralizing solutions apparently had their source in early Tertiary magma which also provided the substance for accompanying bodies of gabbro and lamprophyre. Lode schistosity, which developed concomitantly with the mineralization, indicates deposition along zones of deepseated shearing under intense stress conditions. Mineral associations suggest relatively high temperatures, particularly when cobaltite was deposited. The early-stage solutions apparently carried the cobalt direct from its magmatic source, but the cobalt contained in the second-stage solutions was probably obtained by solution of the earlier-deposited cobaltite.