Добірка наукової літератури з теми "Tetrahedrite-tennantite"

Heterogeneous rhythmic-zonal aggregates of tennantite-IV replaced partly or completely early homogeneous Zn-tetrahedrite-I and euhedral (Fe-Zn)-tennantite-I crystal were found in ores of the Darasun gold deposit. Different replacement stages of fahlore were observed. It initiates at grain boundaries and is terminated by a complete transformation into pseudomorphic newly formed (Zn-Fe)-tennantite-IV aggregates rimed with Zn-tetrahedrite-IV. These aggregates associated intimately with bournonite and galena and their deposition initiated the pseudomorph formation. EMPA revealed that (Fe-Zn)-tetrahedrite richer in As relative to Zn-tetrahedrite-I was deposited at initial stage. Tennantite with wide variation in Sb/(Sb + As) and Fe/(Fe + Zn) ratios predominantes in heterogenous zonal aggregates of (Fe-Zn)-tetrahedrite-tennantite-IV. A negative correlation between the Sb/(Sb + As) and Fe/(Fe + Zn) was found in these minerals. In each site at the contact between Zn-tetrahedrite-I and newly formed (Fe-Zn)-tetrahedrite-tennantite-IV a miscibility gap between As and Sb a sharp drop in the Sb/(Sb + As) ratio and an increase in Fe/(Fe + Zn) ratio occur. Sharp saw-shape boundaries between Zn-tetrahedrite-I and tennantite-IV and voids in newly formed aggregates are considered to be evidence for couple dissolution-precipitation reactions. The dissolution was initiated due disequilibrium between Zn-tetrahedrite-I and an undersaturated fluid resulted from deposition of galena and bournonite. Precipitation of tetrahedrite-tennantite-IV occurred under oscillation in Sb/(Sb + As) and Fe/(Fe + Zn) ratios due to the metal and semimetal contents in the fluid. Crystallization temperature of zonal-heterogenous tennantite-IV aggregates was calculated by sphalerite-fahlore geothermometer which shows (134161) 20 С. Instability of early Zn-tetrahedrite-I resulted from fluid cooling, decreasing in fluid salinity, changing in tetrahedrite and tennantite solubility due to an evolution of migration conditions of semimetals.

A number of sediment-hosted, Carlin-type/-like gold deposits are distributed in the Youjiang basin of SW China. The gold ores are characterized by high As, Hg, and Sb contents but with low base metal contents (Cu+Pb+Zn < 500–1000 ppm). The Nibao deposit is unique among these gold deposits by having tennantite–tetrahedrite-series minerals in its ores. The deposit is also unique in being primarily hosted in the relatively unreactive siliceous pyroclastic rocks, unlike classic Carlin-type gold deposits that are hosted in carbonates or calcareous clastic rocks. In this study, we have identified tennantite-(Zn), tennantite-(Hg), and tetrahedrite-(Zn) from the tennantite–tetrahedrite-series mineral assemblage. The tennantite-(Zn) can be further divided into two sub-types of Tn-(Zn)-I; and Tn-(Zn)-II;. Tn-(Zn)-I; usually occurs in the core of a Tennantite–tetrahedrite composite and appears the darkest under the SEM image, whereas Tn-(Zn)-II overgrows on Tn-(Zn)-I and is overgrown by tetrahedrite-(Zn). Tennantite-(Hg) occasionally occurs as inclusions near the uneven boundary between Tn-(Zn)-I and Tn-(Zn)-II. An appreciable amount of Au (up to 3540 ppm) resides in the tennantite–tetrahedrite-series minerals, indicating that the latter is a major Au host at Nibao. The coexistence of tennantite–tetrahedrite-series minerals and Au-bearing pyrite indicates the Nibao ore fluids were more oxidized than the Carlin-type ore fluids. The tennantite–tetrahedrite series at Nibao evolved from Tn-(Zn)-I through Tn-(Zn)-II to tetrahedrite-(Zn), which is likely caused by Sb accumulation in the ore fluids. This indicates that the Nibao ore fluids may have become more reduced and less acidic during Au precipitation.

The crystals of significantly zonal tetrahedrite-tennantite were found in the mine dump material of the Grubenwall 42 mine, Kramolín, the Michalovy Hory ore district, western Bohemia (Czech Republic). Tetrahedrite-tennantite forms layer of tetrahedral, partly corroded crystals up to 1 mm in size on a crust of crystalline quartz in association with chalcopyrite and cerussite. Individual zones in oscillatory zoned crystals are represented by three members of tetrahedrite group minerals - tetrahedrite-(Zn), tennantite-(Zn) and rare tennantite-(Fe). The observed range of AsSb-1 substitution is unusual within a single crystal and indicates high variability of the As/Sb ratio in the hydrothermal fluids.

The quantitative study of chemical composition of 42 samples of the tetrahedrite group minerals from 16 deposits in Peru provided new data enabling their detailed classification within this group. The majority of samples are usual members of tetrahedrite group: tennantite-(Zn) (Casapalca, Castrovirreyna, Huanzala, Mundo Nuevo, Palomo, Pasto Bueno, Quiruvilca, Huarón, Morococha), tetrahedrite-(Zn) (Huachocolpa, Julcani, Palomo, Pasto Bueno, San Genaro), tetrahedrite-(Fe) (Julcani, Mercedes, Quiruvilca) and tennantite-(Fe) (Milpo, Pachapaqui, Huampar, Huanzala, Quiruvilca). The recently approved new member of this group tennantite-(Cu) was found in two samples from the Julcani ore district. At sample from the San Genero mine, recently approved argentotetrahedrite-(Zn) and an unnamed new member „argentotennantite-(Fe)“ were determined.

AbstractNatural samples containing tetrahedrite–tennantite, bournonite–seligmannite and geocronite–jordanite from the Coranda-Hondol ore deposit, Romania, were investigated by Raman spectroscopy to determine its capability to provide estimates of solid solutions in three common and widespread sulfosalt mineral series. Raman measurements were performed on extended solid solution series (Td1 to Td97, Bnn25 to Bnn93 and Gcn24 to Gcn67, apfu). The tetrahedrite–tennantite and bournonite–seligmannite solid solution series show strong correlations between spectroscopic parameters ( position, relative intensity and shape of the Raman bands) and the Sb/(Sb+As) content ratio, while Raman spectra of geocronite–jordanite shows no evolution of Raman bands. In order to simplify the method used to estimate the Sb/(Sb+As) content ratio in tetrahedrite–tennantite and bournonite–seligmannite series, several linear equations of the first-order polynomial fit were obtained. The results are in good agreement with electron microprobe data. Moreover, a computer program was developed as an analytical tool for a fast and accurate determination of Sb/(Sb+As) content ratio by at least one spectroscopic parameter. These results indicate that Raman spectroscopy can provide direct information on the composition and structure of the tetrahedrite–tennantite and bournonite– seligmannite series.

The composition and structure of tennantite-tetrahedrites from blocks 17 and 18 of the copper-gold high to intermediate sulphidation Chelopech deposit were determined by SEM-EDS. Based on 31 analyses is determined that the tennantites are mostly ferrous, while the tetrahedrites are zinc-rich. In zonal tennantite-tetrahedrite aggregates, sharp saw-shape chalcopyrite bands are evidence of coupled dissolution-precipitation reactions, during the replacement of the former. The fine oscillatory zoning in other tennantite crystals also is related predominantly to internal “self-organization” processes rather than external. In some cases, however, the irregular boundaries between tennantite matrix and tetrahedrite rims and strips and their variable thickness could be due to uneven penetration of fluid into the crystal along the weak zones as a result of replacement rather than overgrowth.

Abstract The classification of the tetrahedrite group minerals in keeping with the current IMA-accepted nomenclature rules is discussed. Tetrahedrite isotypes are cubic, with space group symmetry I43m. The general structural formula of minerals belonging to this group can be written as M(2)A6M(1)(B4C2)X(3) D4S(1)Y12S(2)Z, where A = Cu+, Ag+, ☐ (vacancy), and (Ag6)4+ clusters; B = Cu+, and Ag+; C = Zn2+, Fe2+, Hg2+, Cd2+, Mn2+, Cu2+, Cu+, and Fe3+; D = Sb3+, As3+, Bi3+, and Te4+; Y = S2– and Se2–; and Z = S 2–, Se2–, and ☐. The occurrence of both Me+ and Me2+ cations at the M(1) site, in a 4:2 atomic ratio, is a case of valency-imposed double site-occupancy. Consequently, different combinations of B and C constituents should be regarded as separate mineral species. The tetrahedrite group is divided into five different series on the basis of the A, B, D, and Y constituents, i.e., the tetrahedrite, tennantite, freibergite, hakite, and giraudite series. The nature of the dominant C constituent (the so-called “charge-compensating constituent”) is made explicit using a hyphenated suffix between parentheses. Rozhdestvenskayaite, arsenofreibergite, and goldfieldite could be the names of three other series. Eleven minerals belonging to the tetrahedrite group are considered as valid species: argentotennantite-(Zn), argentotetrahedrite-(Fe), kenoargentotetrahedrite-(Fe), giraudite-(Zn), goldfieldite, hakite-(Hg), rozhdestvenskayaite-(Zn), tennantite-(Fe), tennantite-(Zn), tetrahedrite-(Fe), and tetrahedrite-(Zn). Furthermore, annivite is formally discredited. Minerals corresponding to different end-member compositions should be approved as new mineral species by the IMA-CNMNC following the submission of regular proposals. The nomenclature and classification system of the tetrahedrite group, approved by the IMA-CNMNC, allows the full description of the chemical variability of the tetrahedrite minerals and it is able to convey important chemical information not only to mineralogists but also to ore geologists and industry professionals.

AbstractThe study presents analysis from members of the tennantite–tetrahedrite solid-solution series (‘fahlore’) from 78 locations in the Schwarzwald ore district of SW Germany. Electron microprobe analysis is used to correlate the compositional variations of the fahlores with mineral association, host rock, tectonic history and precipitation mechanisms. Results indicate that most fahlores from gneiss-hosted veins do not have distinctive geochemical characteristics and range from tetrahedrite to tennantite end-member composition with variable trace-element content. However, diagenetically formed fahlore has a near-end-member tennantite composition with very small trace-element content. Red-bed-hosted fahlore formed by fluid mixing is tennantite enriched in Hg that probably has its source in the red-bed sediments. Fahlore formed from granite-related late-magmatic fluids, or from mixing of fluids of which one has equilibrated with granitic basement rocks, is typically As- and Bi-rich (up to 22.2 wt.% Bi). Gneiss-hosted fahlore formed by fluid cooling is Ag-rich near-end-member tetrahedrite. Some fahlores reflect their paragenetic association, e.g. a large Ag content in association with Ag-bearing minerals or a large Co and Ni in association with Co- and Ni-arsenides.Although they have similar compositions, gneiss-hosted fahlores show systematic variations in Ag contents and Fe/Zn ratios between the Central and the Southern Schwarzwald with Fe-rich fahlore in higher stratigraphic levels (North) and Zn- and Ag-rich fahlore in lower stratigraphic levels (South). We show that fahlore composition varies with precipitation mechanism (cooling vs. mixing vs. diagenesis), depth of formation, paragenetic association and host rock. Comparison with fahlores from other European occurrences indicates that these conclusions are consistent with fahlore systematics found elsewhere, and could be used to infer details of ore-forming processes.

The Mutnovskoe deposit is one of the largest and most prospective ore deposits in South Kamchatka. The northern and southern flanks within the main veining zone Opredelyayushchaya, composed of low-sulfi (goldsilver) and sulfide-polymetallic (gold-silver-polymetallic) types of ores, respectively, are distinguished. The paper presents the results of the complex mineralogical and geochemical studies of the gold-silver-polymetallic ores of the southern flank of the deposit. Features of textures and structures, mineral, chemical compositions and genesis of the ores, as well forms of precious and base metals occurrences are shown. Typomorphic features of pyrite, sphalerite, galena, chalcopyrite, tennantite-tetrahedrite, Au, Ag, Pb and Bi tellurides, native gold, Bi, Se and Ag sulfosalts are characterized. The pyrite-sphaleritequartz, sphalerite-galena-quartz, and chalcopyrite-tennantite-tetrahedrite mineral associations are distinguished. The temperatures and composition of ore-forming solutions are shown.

This study addresses trace element concentrations and distributions in hydrothermal base metal sulphide (BMS) ores using samples from a wide variety of ore deposits and conditions of ore formation. The ranges of trace elements that can be incorporated into natural sphalerite, galena, chalcopyrite and tetrahedrite-tennantite are determined, as are the preferred equilibrium trace element partitioning trends among these sulphides. The previously documented coupled substitution Ag⁺+(Bi, Sb)³⁺↔2Pb²⁺ in galena is confirmed, yet should also be modified to include Cu⁺ and Tl⁺. However, when Bi and/or Sb are present at concentrations above ~2000 ppm, incorporation likely includes the creation of site vacancies. Thallium is always principally hosted in galena when BMS assemblages including sphalerite and chalcopyrite are mapped with LA-ICP-MS. Trace element mapping also reveals oscillatory and sector compositional zoning of various elements in galena for the first time. It is inferred that the partitioning of certain minerals between galena and sphalerite pairs is both predictable and systematic. This systematic partitioning is explored and it is shown that the primary factors controlling the preferred BMS hosts of almost all trace elements in sphalerite-galenachalcopyrite assemblages are element oxidation state, ionic radii of the substituting elements, element availability and the maximum trace element budget that a given sulphide structure can accommodate. In contrast, it is revealed that temperature, pressure, redox conditions at time of crystallization and metal source, do not significantly affect the preferred BMS host of almost all trace elements. The only exceptions to this recognized in the study are the critical metals Ga, In and Sn in assemblages recrystallized at high metamorphic grades. Observed partitioning patterns can be used to assess whether a particular BMS assemblage cocrystallized. Compared to sphalerite and galena, trace element concentrations in chalcopyrite are typically quite low (tens to hundreds of ppm). Nevertheless, it is shown that chalcopyrite can host a wide range of trace elements, and the concentrations of such elements generally increase in chalcopyrite in the absence of other co-crystallizing sulphides. Importantly, chalcopyrite is generally a poor host for most elements considered harmful or unwanted in the smelting of Cu (except for Se and Hg on occasions), which suggests it is rarely a significant contributor to the presence of such elements in copper concentrates. The concentrations of Zn and Cd in chalcopyrite show systematic variation that depends, at least in part, on the temperature of BMS crystallization. The Cd:Zn ratios in coexisting chalcopyrite and sphalerite may be used to assess if the physiochemical conditions remained constant during BMS crystallization. Since minerals of the tetrahedrite isotypic series are also common components in base metal ores, investigation into the trace element chemistry of tetrahedrite-tennantite is relevant to understanding the controls on trace element partitioning in such ores. It is shown that tetrahedrite-tennantite will always be the primary host of Ag, Fe, Cu, Zn, As and Sb, and will be the secondary host of Cd, Hg and Bi in co-crystallizing BMS assemblages. Conversely, tetrahedrite-tennantite is a poor host for the critical metals Ga, In and Sn, all of which will prefer to partition to co-crystallizing BMS.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Physical Sciences, 2017.