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Mineralogical, Geochemical, Hyperspectral and Isotopic Constraints on the Formation and...
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Mineralogical, Geochemical, Hyperspectral and Isotopic Constraints on the Formation and Discovery of VMS Deposits

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (17 September 2021) | Viewed by 18394

Special Issue Editors

Dr. Steven P. Hollis

E-Mail Website
Guest Editor
School of GeoSciences, The University of Edinburgh, Edinburgh, UK
Interests: VMS deposits; active hydrothermal systems; linear orogens; Archean cratons; lithogeochemistry; isotopes; hyperspectral analysis
Dr. Jonathan Cloutier

E-Mail Website
Guest Editor
1. Centre for Ore Deposit and Earth Sciences (CODES), University of Tasmania, Hobart, TAS 7001, Australia
2. Geoscience Australia, Cnr Jerrabomberra Ave. and Hindmarsh Drive, Symonston, ACT 2609, Australia
Interests: ore deposits; mineral chemistry; VHMS
Special Issues, Collections and Topics in MDPI journals
Dr. Jean-Luc Pilote

E-Mail Website
Guest Editor
Geological Survey of Canada, Québec, QC, Canada
Interests: gold systems; VMS deposits; lithogeochemistry; mineral chemistry; source of metals; metallogenic provinciality

Special Issue Information

Dear Colleagues,

Since the discovery of actively venting seafloor hydrothermal systems in the late 1970s, volcanogenic massive sulfide (VMS) deposits have become one of the best-understood mineral systems. These deposits remain attractive exploration targets, due to their polymetallic natures, often high grades in base and/or precious metals, and relatively simple alteration assemblages. Recent advances in several analytical techniques (e.g., pXRF, hyperspectral analysis, LA-ICP-MS) have provided opportunities to refine exploration techniques and develop new vectors to ore.

This Special Issue will focus on techniques and case studies that enhance our understanding of VMS deposits to aid their discovery. We particularly welcome papers that integrate aspects of mineralogy, volcanology, lithogeochemistry, mineral chemistry, isotope analysis, and hyperspectral analysis.

Our Special Issue will cover a range of relevant topics, such as:

  • Characterization of multi-scale alteration assemblages through field mapping, mineralogy, lithogeochemistry, and hyperspectral analysis.
  • Mineral chemical studies (e.g., sulfide/silicate LA-ICP-MS) to characterize ore-forming fluids and mineralization processes within individual systems.
  • Detailed stratigraphic and volcanological studies to refine targeting in established camps or prospective regions.
  • Investigations of stable (conventional and non-conventional) and radiogenic isotopes within VMS systems to improve our understanding of ore-forming processes, constrain the timing of mineralization, or identify prospective regions.
  • The effects of deformation and metamorphism on alteration halos, ore composition, and geometry.
  • Reviews on advances in hyperspectral techniques, metamorphosed VMS deposits, Au-rich deposits, or well-established camps.

Thank you, and we look forward to receiving your contributions.

Dr. Steven P. Hollis
Dr. Jonathan Cloutier
Dr. Jean-Luc Pilote
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • VMS mineralization
  • lithogeochemistry
  • geochemical halos
  • ore-forming processes
  • mineral exploration
  • vectoring tools
  • hyperspectral analysis

Published Papers (5 papers)

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Research

51 pages, 21481 KiB  
Article
Potential for Volcanogenic Massive Sulfide Mineralization at the A6 Anomaly, North-West British Columbia, Canada: Stratigraphy, Lithogeochemistry, and Alteration Mineralogy and Chemistry
by Stefanie M. Brueckner, Gregory Johnson, Stephanie Wafforn, Harold Gibson, Ross Sherlock, Christina Anstey and Ken McNaughton
Minerals 2021, 11(8), 867; https://doi.org/10.3390/min11080867 - 11 Aug 2021
Cited by 1 | Viewed by 3013
Abstract
The Middle Jurassic A6 Anomaly is located 30 km southeast of Eskay Creek, north-central British Columbia and consists of thick, altered felsic igneous rocks overlain by a mafic volcano-sedimentary package. Lithogeochemistry on igneous rocks, X-ray diffraction on altered felsic units, and electron probe [...] Read more.
The Middle Jurassic A6 Anomaly is located 30 km southeast of Eskay Creek, north-central British Columbia and consists of thick, altered felsic igneous rocks overlain by a mafic volcano-sedimentary package. Lithogeochemistry on igneous rocks, X-ray diffraction on altered felsic units, and electron probe microanalysis and secondary ion mass spectrometry on illite and quartz were applied to explore the volcanogenic massive sulfide (VMS) potential, characterize alteration, and determine fluid conditions at the A6 Anomaly. Lithogeochemistry revealed calc-alkaline rhyodacite to trachyte of predominantly FII type, tholeiitic basalts with Nb/Yb < 1.6 (i.e., Group A), and transitional to calc-alkaline basalts and andesites with Nb/Yb > 2.2 (i.e., Group B). The felsic units showed weakly to moderately phyllic alteration (quartz–illite with minor orthoclase and trace chlorite–pyrite–calcite–barite–rutile). Illite ranged in composition from illite/smectite (K = 0.5–0.69 apfu) to almost endmember illite (K = 0.69–0.8 apfu), and formed from feldspar destruction by mildly acidic, relatively low temperature, oxidized hydrothermal fluids. The average δ18O composition was 10.7 ± 3.0‰ and 13.4 ± 1.3‰ relative to Vienna Standard Mean Ocean Water for illite and quartz, respectively. Geothermometry involving illite composition and oxygen isotope composition on illite and quartz yielded average fluid temperatures of predominantly 200–250 °C. Lithogeochemical results showed that the A6 Anomaly occurred in a late-Early to Middle Jurassic evolving back-arc basin, further east then previously recognized and in which transitional to calc-alkaline units formed by crustal assimilation to enriched Mid-Ocean Ridge Basalt (EMORB) (i.e., felsic units, Group B), followed by thinning of the crust resulting in tholeiitic normalized MORB basalts (i.e., Group A) with a minor crustal component. The alteration assemblage is representative of distal footwall alteration, and metal transport in this zone was limited despite favorable temperature, pH, and redox state, indicating a metal depleted source (i.e., felsic units). Full article
(This article belongs to the Special Issue Mineralogical, Geochemical, Hyperspectral and Isotopic Constraints on the Formation and Discovery of VMS Deposits)
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18 pages, 7102 KiB  
Article
Identification of Two New Hydrothermal Fields and Sulfide Deposits on the Mid-Atlantic Ridge as a Result of the Combined Use of Exploration Methods: Methane Detection, Water Column Chemistry, Ore Sample Analysis, and Camera Surveys
by Sergei Sudarikov, Egor Narkevsky and Vladimir Petrov
Minerals 2021, 11(7), 726; https://doi.org/10.3390/min11070726 - 05 Jul 2021
Cited by 6 | Viewed by 2370
Abstract
In 2018–2020 the research vessel (R/V) Professor Logachev (cruises 39 and 41) carried out geological and geochemical studies in the bottom waters of the Mid-Atlantic Ridge hydrothermal fields at 14°45’ N, 13°07’ N, and 13°09’ N. Two new hydrothermal fields were discovered—the Molodezhnoye [...] Read more.
In 2018–2020 the research vessel (R/V) Professor Logachev (cruises 39 and 41) carried out geological and geochemical studies in the bottom waters of the Mid-Atlantic Ridge hydrothermal fields at 14°45’ N, 13°07’ N, and 13°09’ N. Two new hydrothermal fields were discovered—the Molodezhnoye and Koralovoye. Standard conductivity, temperature, and depth (CTD) sounding with a methane sensor was accompanied by video surveillance and sampling of rocks and water. The rocks were characterized by a zonal composition with opal and sulfides of copper and zinc. An increase in methane concentration values was accompanied by CTD anomalies in the bottom waters. The methane anomaly was formed within the hydrothermal plume of both high-temperature and low-temperature systems. Methane was almost absent in the plume of neutral buoyancy and was associated in all the studied manifestations with the ascending flow of hot waters over the hydrothermal vents. The hydrothermal plumes were characterized by increased Cu, Zn, and Fe concentrations at background Mn concentrations. Signs of low-temperature hydrothermal activity were also observed. Different sources and mechanisms are required to explain the elevated concentrations of base metals and methane in the hydrothermal plumes. Full article
(This article belongs to the Special Issue Mineralogical, Geochemical, Hyperspectral and Isotopic Constraints on the Formation and Discovery of VMS Deposits)
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16 pages, 6047 KiB  
Article
Mineralogy, Mineral Chemistry and SWIR Spectral Reflectance of Chlorite and White Mica
by Jonathan Cloutier, Stephen J. Piercey and Jonathan Huntington
Minerals 2021, 11(5), 471; https://doi.org/10.3390/min11050471 - 30 Apr 2021
Cited by 17 | Viewed by 5788
Abstract
Hyperspectral reflectance has the potential to provide rapid and low-cost mineralogical and chemical information that can be used to vector in mineral systems. However, the spectral signature of white mica and chlorite, despite numerous studies, is not fully understood. In this study, we [...] Read more.
Hyperspectral reflectance has the potential to provide rapid and low-cost mineralogical and chemical information that can be used to vector in mineral systems. However, the spectral signature of white mica and chlorite, despite numerous studies, is not fully understood. In this study, we review the mineralogy and chemistry of different white mica and chlorite types and investigate what mineralogical and chemical changes are responsible for the apparent shifts in the shortwave infrared (SWIR) spectroscopic absorption features. We demonstrate that the spectral signature of white mica is more complex than previously documented and is influenced by the Tschermak substitution, as well as the sum of interlayer cations. We show that an increase in the interlayer deficiencies towards illite is associated with a change from steep to shallow slopes between the wavelength position of the 2200 nm feature (2200 W) and Mg, Al(VI) and Si. These changes in slope imply that white micas with different elemental chemistry may be associated with the same 2200 W values and vice versa, contrary to traditional interpretation. We recommend that traditional interpretations should only be used in true white mica with sum interlayer cations (I) > 0.95. The spectral signature of trioctahedral chlorite (clinochlore, sheridanite, chamosite and ripidolite) record similar spectral relationships to those observed in previous studies. However, dioctahedral Al-rich chlorite (sudoite, cookeite and donbassite) has a different spectral response with Mg increasing with 2250 W, which is the opposite of traditional trioctahedral chlorite spectral interpretation. In addition, it was shown that dioctahedral chlorite has a 2200 W absorption feature that may introduce erroneous spectral interpretations of white mica and chlorite mixtures. Therefore, care should be used when interpreting the spectral signature of chlorite. We recommend that spectral studies should be complemented with electron microprobe analyses on a subset of at least 30 samples to identify the type of muscovite and chlorite. This will allow the sum I of white mica to be obtained, as well as estimate the slope of 2200 W absorption trends with Mg, Al(vi), and Si. Preliminary probe data will allow more accurate spectral interpretations and allow the user to understand the limitations in their hyperspectral datasets. Full article
(This article belongs to the Special Issue Mineralogical, Geochemical, Hyperspectral and Isotopic Constraints on the Formation and Discovery of VMS Deposits)
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35 pages, 12276 KiB  
Article
Lithogeochemical and Hyperspectral Halos to Ag-Zn-Au Mineralization at Nimbus in the Eastern Goldfields Superterrane, Western Australia
by Steven P. Hollis, Sabri Foury, Stefano Caruso, Sean Johnson, Vitor Barrote and Andrew Pumphrey
Minerals 2021, 11(3), 254; https://doi.org/10.3390/min11030254 - 28 Feb 2021
Cited by 2 | Viewed by 3587
Abstract
With new advances in rapid-acquisition geochemical and hyperspectral techniques, exploration companies are now able to detect subtle halos surrounding orebodies at minimal expense. The Nimbus Ag-Zn-(Au) deposit is unique in the Archean Yilgarn Craton of Western Australia. Due to its mineralogy, alteration assemblages, [...] Read more.
With new advances in rapid-acquisition geochemical and hyperspectral techniques, exploration companies are now able to detect subtle halos surrounding orebodies at minimal expense. The Nimbus Ag-Zn-(Au) deposit is unique in the Archean Yilgarn Craton of Western Australia. Due to its mineralogy, alteration assemblages, geochemical affinity, and tectonic setting, it is interpreted to represent a shallow water (~650 mbsl) and low-temperature (<250 °C) volcanogenic massive sulfide (VMS) deposit with epithermal characteristics (i.e., a hybrid bimodal felsic deposit). We present a detailed paragenetic account of the Nimbus deposit, and establish lithogeochemical and hyperspectral halos to mineralization to aid exploration. Mineralization at Nimbus is characterized by early units of barren massive pyrite that replace glassy dacitic lavas, and underlying zones of polymetallic sulfides that replace autoclastic monomict dacite breccias. The latter are dominated by pyrite-sphalerite-galena, a diverse suite of Ag-Sb ± Pb ± As ± (Cu)-bearing sulfosalts, minor pyrrhotite, arsenopyrite, and rare chalcopyrite. The main sulfosalt suite is characterized by pyrargyrite, and Ag-rich varieties of boulangerite, tetrahedrite, and bournonite. Zones of sulfide mineralization in quartz-sericite(±carbonate)-altered dacite are marked by significant mass gains in Fe, S, Zn, Pb, Sb, Ag, As, Cd, Ni, Cu, Ba, Co, Cr, Tl, Bi, and Au. Basaltic rocks show reduced mass gains in most elements, with zones of intense quartz-chlorite-carbonate±fuchsite alteration restricted to thick sequences of hyaloclastite, and near contacts with dacitic rocks. Broad zones of intense silica-sericite alteration surround mineralization in dacite, and are marked by high Alteration Index and Chlorite-Carbonate-Pyrite Index (CCPI) values, strong Na-Ca depletion, and an absence of feldspar (albite) in thermal infrared (TIR) data. White mica compositions are predominantly muscovitic in weakly altered sections of the dacitic footwall sequence. More paragonitic compositions are associated with zones of increased sericitization and high-grade polymetallic sulfide mineralization. Chlorite in dacitic rocks often occurs adjacent to zones of sulfide mineralization and is restricted to narrow intervals. Carbonate abundance is sporadic in dacite, but is most abundant outside the main zones of Na-Ca depletion. Basaltic rocks are characterized by strongly paragonitic white mica compositions, and abundant chlorite and carbonate. Shifts from Ca carbonates and Fe-rich chlorites to more Mg-rich compositions of both minerals occur in more intensely hydrothermally altered basaltic hyaloclastite, and near contacts with dacitic rocks. Hanging-wall polymict conglomerates are characterized by minor amounts of muscovitic to phengitic white mica (2205–2220 nm), and an absence of chlorite and carbonate alteration. Full article
(This article belongs to the Special Issue Mineralogical, Geochemical, Hyperspectral and Isotopic Constraints on the Formation and Discovery of VMS Deposits)
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21 pages, 9634 KiB  
Article
Reconstruction of Hydrothermal Processes in the Cyprus Type Fe-Cu-Zn Deposits of the Italian Northern Apennines: Results of Combined Fluid Inclusion Microthermometry, SEM-CL Imaging and Trace Element Analyses by LA-ICP-MS
by Gabriella B. Kiss, Zsolt Bendő, Giorgio Garuti, Federica Zaccarini, Edit Király and Ferenc Molnár
Minerals 2021, 11(2), 165; https://doi.org/10.3390/min11020165 - 05 Feb 2021
Cited by 5 | Viewed by 2509
Abstract
Quartz from the stockwork zone of various Cyprus type volcanogenic massive sulfide deposits (Boccassuolo, Reppia, Campegli, Bargone and Vigonzano) from the unmetamorphosed, Jurassic Northern Apennine ophiolites was studied in order to provide details on the submarine hydrothermal conditions and the characteristics for ore [...] Read more.
Quartz from the stockwork zone of various Cyprus type volcanogenic massive sulfide deposits (Boccassuolo, Reppia, Campegli, Bargone and Vigonzano) from the unmetamorphosed, Jurassic Northern Apennine ophiolites was studied in order to provide details on the submarine hydrothermal conditions and the characteristics for ore formation. Our detailed SEM-CL investigation of quartz contributed to a robust characterization and interpretation of primary fluid inclusions and microthermometry data. SEM-CL imaging was also useful for reconstructing the consecutive steps of quartz precipitation. The determination of trace element contents according to growth zoning in quartz by LA-ICP-MS constrained the compositional variations of parent fluids during the hydrothermal activity. A continuously cooling fluid regime characterized each studied volcanogenic massive sulfide (VMS) occurrence although the minimum formation temperatures were different (Bargone: 110–270 °C; Boccassuolo: 60–360 °C; Campegli: 110–225 °C; Reppia: 50–205 °C; Vigonzano: 260–330 °C), the range of temperature most probably depends on the original position of sampling in relation to the centers of the hydrothermal systems. Compositional changes are reflected by variations in the methane content (0.13–0.33 mol/kg) and salinity (2.6–9.3 NaCl equiv. wt. %) in the fluid inclusions of quartz and calcite as well as a changeable Al content (11–1526 ppm) in quartz. This study demonstrates that the combined use of SEM-CL imaging and LA-ICP-MS analyses, coupled with fluid inclusion microthermometry, can constrain the different fluid conditions of ore forming and the barren stages of evolving submarine hydrothermal systems. Full article
(This article belongs to the Special Issue Mineralogical, Geochemical, Hyperspectral and Isotopic Constraints on the Formation and Discovery of VMS Deposits)
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