Fe-Zn exchange reaction between tetrahedrite and sphalerite in natural environments

O’Leary, Michael J.; Sack, Richard O.

doi:10.1007/bf01166687

Cited by 41 publications

(24 citation statements)

References 20 publications

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“…13) (see below). In addition, the data in Fig.14 support the existence of a miscibility gap in fahlores first predicted by O´Leary and Sack (1987) and confirmed by Sack et al (2003) and Chutas and Sack (2004).…”

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confidence: 76%

The Patricia Zn–Pb–Ag epithermal ore deposit: An uncommon type of mineralization in northeastern Chile

Chinchilla

Menor

Piña

et al. 2016

Ore Geology Reviews

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The Patricia ore deposit represents an unusual example of economic Zn-Pb-Ag mineralization at the northernmost end of the Late Eocene-Oligocene metallogenic belt in Chile. It is hosted by volcanosedimentary units, which are typically tuffaceous and andesitic breccias. The ore body consists of a set of subvertical E-W vein systems developed under a sinistral strike-slip regime that included transtensive domains with generalized extensional structures where the ores were deposited. The deposit is divided into two blocks by a set of NNW-ESE-trending reverse faults, which uplifted the eastern block and exhumed thicker and deeper parts of the deposit. At least 200 m of volcano-sedimentary pile hosting the mineralization has been eroded in this block. By contrast, the western block exposes a shallower part of the system where cherts, amorphous silica and jasperoids occur. Three main stages of mineralization have been defined: (1) pre-ore stage is characterized by early quartz, pyrite and arsenopyrite, (2) base-metal and silver stage; characterized by sphalerite (6 to 15 mol.% FeS), galena, chalcopyrite, pyrrhotite and Agbearing minerals (freibergite, polybasite, stephanite, pyrargyrite, freieslebenite and acanthite) and (3) post-ore stage; characterized by late quartz, kutnohorite and minor sulfides (arsenopyrite, sphalerite,pyrite, galena, Ag-bearing minerals and Pb-sulfosalts). Whole-ore geochemistry shows two groups of elements that are positively correlated; 1) Ag-Cd-Cu-Pb-Zn related to the base metal sulfides and 2) AuAs-Ge-Sb-W related to arsenopyrite and pyrite. Hydrothermal alteration is pervasive in the outcropping mineralized areas, including silicification and locally, vuggy silica textures. At depth, chloritic and sericitic alteration is developed along vein selvages and is superimposed to the regional propylitic alteration. Fluid inclusions indicate that the base-metal ores were deposited from 250-150º C moderate salinity fluids (1-9 wt % NaCl). The pre-ore stage is characterized by a saline fluid (6-22 wt % NaCl) and between 210 and 250ºC whereas the post-ore stage has salinity of 4-8 wt % and temperature from 175 to 215ºC. Cooling was the mechanism of ore mineral precipitation in the Patricia deposit, although mixing of fluids could have occurred in the pre-ore stage. Mineralogical, geochemical and fluid inclusion evidence is consistent with an intermediate sulfidation (IS) epithermal deposit type. This study highlights the high potential for hidden economic mineralization at depth in the western block and for extension of the ore body both to the south and to deeper levels in the eastern block of the Patricia ore deposit. To a larger extent, the implications of finding such polymetallic epithermal style of mineralization in the northern Chile Precordillera is relevant both to the regional metallogenic perspective and to the exploration potential of the region, where the late Eocene-early Oligocene metallogenic belt apparently disappears.

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confidence: 76%

The Patricia Zn–Pb–Ag epithermal ore deposit: An uncommon type of mineralization in northeastern Chile

Chinchilla

Menor

Piña

et al. 2016

Ore Geology Reviews

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“…The intersections of miscilibity-gap isotherms with /-yElec isopleths of electrum composition v'~Ag of 0.60, 0.65, 0.75, 0.85, and 1.00) define tielines for coexisting fahlores that are in Ag-Cu exchange equilibrium with these electrums, chalcopyrite, and pyrite according to the calibration of Sack (1989, 1991). Sources of compositional data are referenced in Sack et al (1987), Sack (1992), or are from Akande (1985), Charnock et al (1989), Gemell et al (1989, Kase (1988), Lynch (1989), Naik (1975), Pearson et al (1988), Schmid et al (1990), and Yigitgtiden and Friedrich (1986.…”

Section: Resultsmentioning

confidence: 99%

“…We may analyse the As-Sb exchange isotherms using the formulation of Sack et al (1987) for the thermodynamic properties of (Cu,Ag)10-(Fe,Zn)2(Sb,As)4S13 fahlores, given the assumptions of (1) strictly regular binary solution behaviour of bournonite-seligmannite and (2) negligible energetic consequences of deviations from the nominal stoichiometric formula of fahlore. For these approximations, we may write the following equation for the condition of As-Sb exchange equilibrium between these phases, (~GBRN Table 1 or are estimated from nominal compositions.…”

Section: Resultsmentioning

confidence: 99%

“…Values for the energies of the reciprocal reactions defining these incompatibilities, and for the energetic effects associated with the Ag for Cu and Zn for Fe exchange substitutions, have been established from constraints on exchange reactions between fahlores and assemblages consisting of simpler sulphosalts, sulphides, and alloys (cf. Raabe and Sack, 1984;Sack and Loucks, 1985;O'Leary and Sack, 1987;Sack et al, 1987;Sack, 1989, 1991). In this paper, we present results from As-Sb exchange experiments between tetrahedrite-ten-nantite fahlores and bournonite-seligmannite solid solutions.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we present results from As-Sb exchange experiments between tetrahedrite-ten-nantite fahlores and bournonite-seligmannite solid solutions. These experimental results are used to constrain the nonideality associated with the As-Sb substitutions in these minerals, and complete the calibration of a model for the thermodynamic mixing properties of tetrahedrite-tennantite (Sack et al, 1987). Model miscibility gaps and the calibration for the As-Sb exchange reaction are compared with constraints from nature.…”

Section: Introductionmentioning

confidence: 99%

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As-Sb Exchange Energies in Tetrahedrite-Tennantite Fahlores and Bournonite-Seligmannite Solid Solutions

Sack

Ebel

1993

Mineral. mag.

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Reversed brackets on As and Sb partitioning between tetrahedrite-tennantite fahlores {--CUlo(Fe,Zn)2(Sb,As)4S13} and bournonite-seligmannite solid solutions {CuPb(Sb,As)S3} (400 ~ evacuated silica tubes, NH4CI flux) indicate that the maximum nonidealities associated with the As-Sb substitution are about 165 (bournonite) and 250 (fahlore) cal/gfw on a per atom exchange basis. The experimental constraints are consistent with the following calibration of the As-Sb exchange reaction between these phases: kcal/gfw, X2 -Zn/(Zn + Fe) (or one-half the number of Zn atoms/formula unit) and X3 -As/(As + Sb) refer to atomic ratios in fahlore, and AG~3-o = AH23 = 2.59 _+ 0.14 kcal/gfw (Raabe

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Textural, chemical, isotopic and microthermometric features of sphalerite from the Wunuer deposit, Inner Mongolia: Implications for two stages of mineralization from hydrothermal to epithermal

2020

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The Wunuer Pb-Zn-Ag-Mo deposit is a newly explored polymetallic ore deposit located in the middle segment of the Great Xing'an Range, Inner Mongolia, NE China. Three stages of mineralization, composed of an early porphyry stage, an intermediate hydrothermal (cryptoexplosive breccia) stage, and a later epithermal stage, have been identified in the Wunuer deposit. Sphalerite is one of the principal metal sulphides in both hydrothermal and epithermal stages, and thus two generations of sphalerite, with the first-generation sphalerite (Sp1) precipitated in hydrothermal stage and the second-generation sphalerite (Sp2) precipitated in epithermal stage, were discriminated. The Sp1 is generally euhedral, transparent and colour-zoned, and is usually replaced by Sp2, galena and chalcopyrite. The Sp2 is generally anhedral, opaque and black in colour. Chalcopyrite inclusions in Sp1 and Sp2 have different genetic mechanisms: chalcopyrite inclusions in Sp1 were produced by replacement as the result of interaction of sphalerite with Cu-rich fluids, while chalcopyrite inclusions in Sp2 were produced by coprecipitation of sphalerite and chalcopyrite during crystal growth. Electron probe microscope analyser and laser ablation inductively coupled plasma mass spectrometry in-situ analysis techniques have been used to obtain chemical compositions of sphalerite. The Sp1 is enriched in Cd and In, and depleted in Mn, Fe, Cu, Ag, Sb and Pb. In contrast, the Sp2 is enriched in Mn, Fe, Cu, Ag, Sb and Pb, and depleted in Cd and In. Elements of Pb, Ag, Bi and some of Fe, Cu concentrated in Sp2 are greatly attributed to micro-mineral inclusions like chalcopyrite and galena, while most elements concentrated into Sp1 are generally incorporated into crystal structure in mechanisms of direct substitution (e.g. Fe 2+ ! Zn 2+) or coupled substitution ((Cu + + In 3+) ! 2Zn 2+). In-situ sulphur isotope results reveal similar slightly positive sulphur isotope compositions (+1.55‰ to +3.33‰ δ 34 S V-CDT for Sp1, and +1.71‰ to +2.34‰ δ 34 S V-CDT for Sp2) of the two generations of sphalerite, implying a magmatic material for both Sp1 and Sp2. Fluid inclusions in molybdenite-bearing quartz vein, Sp1 and Sp2-coexisting quartz have been studied to reveal fluid temperature and salinity evolution from porphyry to hydrothermal and to epithermal stage mineralization. Primary fluid inclusions in porphyry stage quartz homogenized to a liquid phase by high homogenization temperatures (range from 385 to 416 C, with an average of 399 C), with salinities ranging from 12.4 to 25.3 wt% (average of 19.4 wt%).

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Fe-Zn exchange reaction between tetrahedrite and sphalerite in natural environments

Cited by 41 publications

References 20 publications

The Patricia Zn–Pb–Ag epithermal ore deposit: An uncommon type of mineralization in northeastern Chile

The Patricia Zn–Pb–Ag epithermal ore deposit: An uncommon type of mineralization in northeastern Chile

As-Sb Exchange Energies in Tetrahedrite-Tennantite Fahlores and Bournonite-Seligmannite Solid Solutions

Textural, chemical, isotopic and microthermometric features of sphalerite from the Wunuer deposit, Inner Mongolia: Implications for two stages of mineralization from hydrothermal to epithermal

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