Nodular sillimanite rocks as field indicators to metamorphosed massive sulfide deposits

Spry, Paul G.; McFadden, Scott; Teale, Graham S.; Alers, Brian; Shallow, John M.; Glenn, J. MacPherson

doi:10.1016/j.oregeorev.2021.104632

Cited by 5 publications

(13 citation statements)

References 40 publications

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“…In this contribution, we evaluate the geological setting along with the major and trace element studies of various rock types (including metamorphosed hydrothermally altered rocks and granitoids), the compositions of minerals in the sulphide-bearing units and attendant alteration, and the sulphur isotope ratios of sulphides in various deposits. The present contribution complements previous studies on aspects of the geology of these occurrences, including the descriptive geology of the deposits by Sheridan and Raymond (1984a, 1984b), the genetic relationship of gahnite to sulphide mineralization (Heimann et al 2005), the origin of gedrite-garnet-cordierite rocks at the Evergreen prospect (Heimann et al 2006), and the genetic relationship of nodular sillimanite rocks to sulphide mineralization (Spry et al 2022b). The aim of the current study is to evaluate the origin of the various deposits and to provide exploration tools that can potentially be used as guides to further mineralization in regionally metamorphosed rocks in south-central Colorado.…”

Section: Introductionsupporting

confidence: 70%

“…Although nodular sillimanite rocks and gahnite-bearing rocks are spatially associated with several deposits listed in Table 1, they were the focus of studies by Spry et al . (2022b) and Heimann et al (2005), respectively, and will only be discussed here as they relate to the origin of the deposits and their potential as exploration guides to metallic mineralization. Note we use the term ‘gahnite’ here for zinc-bearing spinels regardless of the Zn-Fe-Mg proportion, which was shown by Heimann et al (2005) to be variable in composition for deposits in Colorado.…”

Section: Local Geology Of Mineral Depositsmentioning

confidence: 99%

“…Note the presence of metagabbro just to the south of the Cinderella deposit. The figure is modified after Spry et al (2022b). …”

Section: Local Geology Of Mineral Depositsmentioning

confidence: 99%

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The genesis of metamorphosed Paleoproterozoic massive sulphide occurrences in central Colorado: geological, mineralogical and sulphur isotope constraints

Berke,

Spry,

Heimann

et al. 2023

Geol. Mag.

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Paleoproterozoic massive Cu-Zn±Pb±Au±Ag sulphide deposits metamorphosed to the middle-upper amphibolite facies in central-south Colorado formed in a volcanic arc setting on the edge of the Yavapai crustal province. Previously published U-Pb ages on spatially related granitoids range from ∼1.9 to ∼1.1 Ga, while Pb isotope studies on galena from massive sulphides suggest mineralization formed at around 1.8–1.7 Ga. Some deposits in the Dawson-Green Mountain trend (DGMT) and the Gunnison belt are composed of Cu-Zn-Au-(Pb-Ag) mineralization that were overprinted by later Au-(Ag-Cu-Bi-Se-Te) mineralization. Sulphide mineralization is spatially related to amphibolite and bimodal, mafic-felsic volcanic rocks (gabbro, amphibolite, rhyolite and dacite) and granitoids, but it occurs mostly in biotite-garnet-quartz±sillimanite±cordierite schists and gneisses, spatially related to nodular sillimanite rocks, and in some locations, exhalative rocks (iron formations, gahnite-rich rocks and quartz-garnetite). The major metallic minerals of the massive sulphides include chalcopyrite, sphalerite, pyrite, pyrrhotite, and magnetite, with minor galena and gahnite. Altered rocks intimately associated with mineralization primarily consist of various amphiboles (gedrite, tremolite and hornblende), gahnite, biotite, garnet, cordierite, carbonate and rare högbomite. The Zn/Cd ratios of sphalerite (44 to 307) in deposits in the DGMT fall within the range of global volcanogenic massive sulphide (VMS) deposits but overlap with sphalerite from sedimentary exhalative (Sedex) deposits. Sulphur isotope values of sulphides (δ34S = −3.3 to +6.5) suggest sulphur was largely derived from magmatic sources, and that variations in isotopic values resulting from thermochemical sulphate reduction are due to small differences in physicochemical conditions. The preferred genetic model is for the deposits to be bimodal-mafic (Gunnison) to mafic-siliciclastic VMS deposits (Cotopaxi, Cinderella-Bon Ton, DGMT).

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Section: Introductionsupporting

confidence: 70%

Section: Local Geology Of Mineral Depositsmentioning

confidence: 99%

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The genesis of metamorphosed Paleoproterozoic massive sulphide occurrences in central Colorado: geological, mineralogical and sulphur isotope constraints

Berke,

Spry,

Heimann

et al. 2023

Geol. Mag.

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“…Walters, 1996;Walters et al 2002;Spry & Teale, 2021) or deposits that are possibly transitional between Sedex and VMS deposits (e.g. Walters, 1998;Leach et al 2005;Spry et al 2010). Epigenetic models revolve around the introduction of metals during peak metamorphism or by post-tectonic replacement (e.g.…”

Section: A Previous Genetic Modelsmentioning

confidence: 99%

“…Walters, 1996;Walters et al 2002;Spry & Teale, 2021) or deposits that are possibly transitional between Sedex and VMS deposits (e.g. Walters, 1998;Leach et al 2005;Spry et al 2010).…”

Section: A Previous Genetic Modelsmentioning

confidence: 99%

Zinc, sulfur and cadmium isotopes and Zn/Cd ratios as indicators of the origin of the supergiant Broken Hill Pb–Zn–Ag deposit and other Broken Hill-type deposits, New South Wales, Australia

Spry

Mathur

Teale³

et al. 2022

Geol. Mag.

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Various genetic models have been proposed for the supergiant Proterozoic Broken Hill Pb–Zn–Ag deposit largely based on geological and geochronological evidence. Here we present Zn, Cd and S isotope compositions as well as Zn/Cd ratios of sphalerite from Broken Hill and minor Broken Hill-type deposits (Australia) to help constrain these models but focus on syngenetic and magmatic–hydrothermal processes, since epigenetic models can be rejected because the orebodies were deformed and metamorphosed by the Olarian Orogeny. Values of δ34SVCDT, δ66ZnAA-ETH and δ114CdNIST SRM 3108 for sphalerite from Broken Hill range from +0.27 to +4.73 ‰, −1.15 to +0.46 ‰ and −0.48 to +0.01 ‰, respectively, while those for the smaller Broken Hill-type deposits range from −5.11 to +1.28 ‰, −0.97 to +0.10 ‰ and −1.02 to +2.59 ‰, respectively. By combining published S isotope data of sulfides from the Broken Hill district with those obtained here, the sources of sulfur via thermochemical sulfate reduction, bacterial sulfate reduction and a magmatic origin cannot be distinguished. However, when the S isotope compositions are considered along with the broad range of Cd and Zn isotope data for sphalerite, which are among the lightest and heaviest yet reported for a sulfide deposit, the isotopic datasets are consistent with low-temperature biogenic processes associated with syngenetic deposition of sulfides. Cadmium isotope compositions when coupled with Zn/Cd ratios of sphalerite have previously been used to classify Pb–Zn deposits, including low-temperature, high-temperature and exhalative ores. However, the Zn/Cd ratios of sphalerite from Broken Hill cannot be used for such classification purposes.

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Microfabric evolution during metasomatism and deformation, exemplified by the nodular sillimanite gneisses (Bamble lithotectonic domain, South Norway)

Engvik,

Trepmann,

Austrheim

2023

Lithos

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Nodular sillimanite rocks as field indicators to metamorphosed massive sulfide deposits

Cited by 5 publications

References 40 publications

The genesis of metamorphosed Paleoproterozoic massive sulphide occurrences in central Colorado: geological, mineralogical and sulphur isotope constraints

The genesis of metamorphosed Paleoproterozoic massive sulphide occurrences in central Colorado: geological, mineralogical and sulphur isotope constraints

Zinc, sulfur and cadmium isotopes and Zn/Cd ratios as indicators of the origin of the supergiant Broken Hill Pb–Zn–Ag deposit and other Broken Hill-type deposits, New South Wales, Australia

Microfabric evolution during metasomatism and deformation, exemplified by the nodular sillimanite gneisses (Bamble lithotectonic domain, South Norway)

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