Exploration for Epithermal Gold Deposits

Hedenquist, Jeffrey W.; Arribas, R Antonio; Gonzalez-Urien, Eliseo

doi:10.5382/rev.13.07

Cited by 169 publications

(12 citation statements)

References 67 publications

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“…17,18 This diagnostic variation is advantageous in exploration for highsulfidation epithermal deposits since it can enable compositional discrimination between alunite minerals formed by hypogene and supergene processes. 2,4…”

Section: Alunitementioning

confidence: 99%

“…2 Low-sulfidation epithermal Ag-Au deposits contain vein and selvage alteration minerals formed from neutral and reducing hydrothermal fluids. 4,5 Hydrothermal alteration zoning includes a highly quartz-altered (i.e., silicified) inner alteration zone characterized by the presence of chalcedony, sericite, adularia, and mixed layered illite-smectite. 4 This proximal alteration is most often surrounded by an outer alteration halo comprising chlorite, calcite, and epidote.…”

Section: Introductionmentioning

confidence: 99%

“…4 This proximal alteration is most often surrounded by an outer alteration halo comprising chlorite, calcite, and epidote. 4 A third epithermal mineralization style, intermediate-sulfidation epithermal deposits, share many features with low-sulfidation epithermal deposits, but display an intermediate sulfidation-state assemblage indicated by minerals such as tetrahedrite/tennantite and low-Fe sphalerite. 4 Multiple studies have focused on the mineralogical and chemical characterization of hydrothermal alteration in epithermal systems through a combination of optical microscopy, scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and/or X-ray diffraction (XRD).…”

Section: Introductionmentioning

confidence: 99%

“…4 A third epithermal mineralization style, intermediate-sulfidation epithermal deposits, share many features with low-sulfidation epithermal deposits, but display an intermediate sulfidation-state assemblage indicated by minerals such as tetrahedrite/tennantite and low-Fe sphalerite. 4 Multiple studies have focused on the mineralogical and chemical characterization of hydrothermal alteration in epithermal systems through a combination of optical microscopy, scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and/or X-ray diffraction (XRD). 2,3,8À11 However, powder X-ray diffraction is a destructive technique, which does not preserve textural and paragenetic information, and the separation of finegrained clay fraction minerals (mainly phyllosilicates) is a labor-intensive process that has only been implemented in a handful of hydrothermal alteration studies.…”

Section: Introductionmentioning

confidence: 99%

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Raman Spectroscopy Coupled with Reflectance Spectroscopy as a Tool for the Characterization of Key Hydrothermal Alteration Minerals in Epithermal Au–Ag Systems: Utility and Implications for Mineral Exploration

Arbiol

Layne

2021

Appl Spectrosc

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Raman spectroscopy of fine-grained hydrothermal alteration minerals, and phyllosilicates in particular, presents certain challenges. However, given the increasingly widespread recognition of field portable visible–near infrared–shortwave infrared (Vis-NIR-SWIR) spectroscopy as a valuable tool in the mineral exploration industry, Raman microspectroscopy has promise as an approach for developing detailed complementary information on hydrothermal alteration phases in ore-forming systems. Here we present exemplar high-quality Raman and Vis-NIR-SWIR spectra of four key hydrothermal alteration minerals (pyrophyllite, white mica, chlorite, and alunite) that are common in precious metal epithermal systems, from deposits on the island of Newfoundland, Canada. The results reported here demonstrate that Raman microspectroscopy can accurately characterize pyrophyllite, white mica, chlorite, and alunite and provide details on their compositional variation at the microscale. In particular, spectral differences in the 1000–1150 cm−1 white mica Raman band allows the distinction between low-Tschermak phases (muscovite, paragonite) and phases with higher degrees of Tschermak substitution (phengitic white mica composition). The peak position of the main chlorite Raman band shifts between 683 cm−1 for Mg-rich chlorite and 665 cm−1 for Fe-rich chlorite and can be therefore used for semiquantitative estimation of the Fe2+ content in chlorite. Furthermore, while Vis-NIR-SWIR macrospectroscopy allows the rapid identification of the overall composition of the most abundant hydrothermal alteration mineral in a given sample, Raman microspectroscopy provides an in-depth spectral and chemical characterization of individual mineral grains, preserving the spatial and paragenetic context of each mineral and allowing for the distinction of chemical variation between (and within) different mineral grains. This is particularly useful in the case of alunite, white mica, and chlorite, minerals with extensive solid solution, where microscale characterization can provide information on the alteration zonation useful for mineral exploration and provide insight into mineral deposit genesis.

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Section: Alunitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Raman Spectroscopy Coupled with Reflectance Spectroscopy as a Tool for the Characterization of Key Hydrothermal Alteration Minerals in Epithermal Au–Ag Systems: Utility and Implications for Mineral Exploration

Arbiol

Layne

2021

Appl Spectrosc

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“…Originally, epithermal deposits were defined by Lindgren (1922) as precious or base metal deposits forming at shallow depth and low temperature-pressure conditions. Recent data indicate that the most epithermal ores form at temperatures between 100 o C and 300 o C and depths up to 750-800 m. Epithermal gold deposits were divided into high, intermediate and low sufidation subtypes (Hedenquist et al ,2000;Sillitoe and Hedenquist, 2003), but the intermediate sulfidation seems to be rather a transitional term between high and low degree of system sulfidation closer to sulfide-poor style.…”

Section: Epithermal Depositsmentioning

confidence: 99%

A novel conceptual model of intrusion related gold bearing systems and exploration tools

Orlandea¹,

Vlad²

2020

Studia UBB Geologia

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Despite numerous debates conducted in the last two decades, the concept of intrusion related gold systems IRGS remains controversial and sometimes befuddling. The key issue drifts from case to case, i.e., initial to subsequent proposed classifications, presence of gold in reduced fluids-porphyritic environments, non-porphyry gold in orogenic terrains and participation of non-magmatic gold fluids in depositional processes. Trying to avoid atypical or particular aspects of certain deposits, a genuine metallogenetic depiction intends to enhance the intrusion related systems meaning. Gold is either a major constituent or a mere byproduct. A vertical metal zonation develops from surface to depth:

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Gallium and Gallium Compounds

Gray¹,

Kramer²,

Bliss³

2005

Kirk-Othmer Encyclopedia of Chemical Technology

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Gallium is a scarce but not a rare element. It is found most commonly in association with its immediate neighbors in the Periodic Table, ie, zinc, germanium, and aluminum. The concentration of gallium in the earth’s crust, 10–20 g/t (10–20 ppm), is comparable to that of lead and arsenic. There is an abundance of aluminum ores and alumina plants, and less importantly to gallium production zinc ores and plants; these are the main sources of gallium. The physical properties of gallium, especially its thermal properties, are exceptional. It is easily supercooled. In accordance with its normal potential, gallium is chemically similar to zinc and is somewhat less reactive than aluminum. A minor amount of gallium is extracted as a by‐product from the zinc industry. The significant amount of primary gallium is recovered from the alumina industry. The main source is the sodium aluminate liquor from Bayer‐process plants that produce large quantities of alumina. A large part of the wastes from the gallium arsenide industry is recovered for both economical and environmental reasons. Several processes are effective and are being used to recover both the gallium either as a metal, a salt, or a hydroxide for recycling, and the arsenic in some form for recycling or disposal. Gallium either comes from mining sources or is recycled from scrap. Gallium has complete miscibility in the liquid state with aluminum, indium, tin, and zinc. No compounds are formed. Numerous intermetallic gallium–transition element compounds have been reported. The toxicity of metallic gallium or gallium salts is very low. Gallium is used in the production of electronics and magnets, in medicine, as a petroleum industry catalyst, and in the solar reactions experiment.

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Exploration for Epithermal Gold Deposits

Cited by 169 publications

References 67 publications

Raman Spectroscopy Coupled with Reflectance Spectroscopy as a Tool for the Characterization of Key Hydrothermal Alteration Minerals in Epithermal Au–Ag Systems: Utility and Implications for Mineral Exploration

Raman Spectroscopy Coupled with Reflectance Spectroscopy as a Tool for the Characterization of Key Hydrothermal Alteration Minerals in Epithermal Au–Ag Systems: Utility and Implications for Mineral Exploration

A novel conceptual model of intrusion related gold bearing systems and exploration tools

Gallium and Gallium Compounds

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