Geochemistry and Geochronology of Mineral Deposits

A special issue of Geosciences (ISSN 2076-3263). This special issue belongs to the section "Geochemistry".

Deadline for manuscript submissions: closed (25 January 2023) | Viewed by 11944

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Department of Geology, Brandon University, 270 – 18th Street, Brandon, MB R7A 6A9, Canada
Interests: metallogeny; exploration; geochemistry; mineralogy
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Special Issue Information

Dear Colleagues,

Geochemistry and geochronology are powerful yet elegant techniques helping us to decipher the formation processes and conditions of a variety of mineral deposits. This Special Issue of Geosciences invites submissions that apply geochemistry (major and trace elements, stable and radiogenic isotopes, both on whole rock and on minerals) and geochronology (40Ar/39Ar, U/Pb, Rb/Sr) on a wide variety of mineral deposits and in a novel and original way. Submissions on novel developments, techniques and applications, review and critique papers, and papers documenting examples of successful applications are all welcome.

Dr. Paul Alexandre
Guest Editor

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Keywords

  • geochemistry
  • geochronology
  • mineral deposits
  • isotopes
  • mineral chemistry

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Published Papers (5 papers)

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Research

20 pages, 17830 KiB  
Article
Characterization of Gold of the Murcielago Fluvial Placer (Central Honduras) and Its Possible Primary Sources
by Sabrina Nazzareni, Simona Alunno, Federica Zaccarini, Michele Mattioli, Alessandro Murroni, Alessandro Di Michele and Alberto Renzulli
Geosciences 2023, 13(6), 175; https://doi.org/10.3390/geosciences13060175 - 10 Jun 2023
Viewed by 1543
Abstract
The Murcielago gold placer is located in the Lepaguare Valley, Olancho Department (Central Honduras). The placer mineralogy includes silicates (quartz, garnets, amphibole, Ca-pyroxene, micas, epidote, and tourmaline); calcite; and in the heavy fraction, zircon, ilmenite–rutile, magnetite, hematite, cassiterite, and cinnabar. Gold grains recovered [...] Read more.
The Murcielago gold placer is located in the Lepaguare Valley, Olancho Department (Central Honduras). The placer mineralogy includes silicates (quartz, garnets, amphibole, Ca-pyroxene, micas, epidote, and tourmaline); calcite; and in the heavy fraction, zircon, ilmenite–rutile, magnetite, hematite, cassiterite, and cinnabar. Gold grains recovered from the Murcielago placer production plant are mainly flattened grains with a moderately to high elliptical shape. The composition of the gold grains varies continuously in the range Au46Ag54 to Au88Ag12. Few of them are characterized by Au-rich rims of a few microns in size (Ag 3-1 atoms percent (at%)). Gold from the Canan lode deposit, a nearby hydrothermal Au mineralization area, has a composition (from Au54Ag44 to Au81Ag19) overlapping the composition of the Murcielago grains. Inclusions in the alluvial gold particles are arsenopyrite, pyrite, acanthite, sphalerite, and hematite. On the basis of the placer mineralogy and the gold grains analyses, possible gold source(s) include the Canan lode and skarn gold deposits in the area. We obtained new data on the Murcielago gold placer that will be the basis for an exploration of the potential sources of gold in the area. Full article
(This article belongs to the Special Issue Geochemistry and Geochronology of Mineral Deposits)
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21 pages, 15648 KiB  
Article
Copper, Uranium and REE Mineralisation in an Exhumed Oil Reservoir, Southwest Orkney, Scotland
by Eleanor A. Heptinstall, John Parnell, Joseph G. T. Armstrong, Andrea Schito and Temitope O. Akinsanpe
Geosciences 2023, 13(5), 151; https://doi.org/10.3390/geosciences13050151 - 20 May 2023
Cited by 2 | Viewed by 2208
Abstract
Copper, uranium, and rare earth element (REE) mineralisation occurs in hydrocarbon-bearing Devonian continental sandstones in southwest Orkney, Scotland. The aeolian Yesnaby Sandstone Formation and fluvial Harra Ebb Sandstone Formation were mineralised following oil emplacement. The REE-bearing APS mineral florencite is particularly associated with [...] Read more.
Copper, uranium, and rare earth element (REE) mineralisation occurs in hydrocarbon-bearing Devonian continental sandstones in southwest Orkney, Scotland. The aeolian Yesnaby Sandstone Formation and fluvial Harra Ebb Sandstone Formation were mineralised following oil emplacement. The REE-bearing APS mineral florencite is particularly associated with bituminous nodules, many of which contain brannerite. Subsequently hydrothermal copper and other sulphides, and barite, further mineralised the oil reservoir at a temperature of ~190 °C. Oil was mobilised through mineralised fractures at this stage. Biodegradation of the oil occurred later, following the Carboniferous-Permian uplift. The occurrence confirms that Cu-APS mineralisation is possible in relatively low-temperature regimes in sedimentary basins. Full article
(This article belongs to the Special Issue Geochemistry and Geochronology of Mineral Deposits)
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15 pages, 1853 KiB  
Article
How Can Technical Aspects Help Improving K-Ar Isotopic Data of Illite-Rich Clay Materials into Meaningful Ages? The Case of the Dominique Peter Uranium Deposit (Saskatchewan, Canada)
by Norbert Clauer
Geosciences 2020, 10(8), 285; https://doi.org/10.3390/geosciences10080285 - 27 Jul 2020
Cited by 5 | Viewed by 2166
Abstract
Previously published K-Ar dating results of <2 μm illite separates from uranium-hosting and associated barren rocks from Dominique Peter district of the Carswell circular structure in the Athabasca Basin (Canada) were considered to trace four distinct tectonic-thermal events at 1447 ± 45, 1282 [...] Read more.
Previously published K-Ar dating results of <2 μm illite separates from uranium-hosting and associated barren rocks from Dominique Peter district of the Carswell circular structure in the Athabasca Basin (Canada) were considered to trace four distinct tectonic-thermal events at 1447 ± 45, 1282 ± 40 and 1184 ± 15 (all errors at ± 2 Ma, with a younger, less constrained episode at ~900 Ma. Recent analyses of K-Ar ages of additional <0.2 μm illite fractions from a few initial samples demonstrate that the intermediate ages at ~1280 and ~1185 Ma result, in fact, from mixing of two generations of illite that precipitated at ~1450 and ~900 Ma. They have, therefore, no stratigraphic value, while the two tectonic-thermal episodes at 1448 ± 48 and 937 ± 39 Ma appear to be historically sound. In fact, the analytical procedure of isotopic dating clay materials is of more importance than is often stated. For instance, a safe way to evaluate and constrain best numerical isotopic data of clay separates into ages is combining data of two size splits from several samples. If such age data, especially from size fractions of indurated host rocks, are scattered and point towards the higher data of the coarser fractions, they are potentially enriched in earlier crystallized K-rich components, and should consequently be discarded. The occurrence of detrital or early-crystallized components in clay-rich separates becomes a serious concern when comparing ages generated by various isotopic methods on mineral separates of various whole rocks. It is especially verified in very old, metal-rich deposits such as the uranium-rich deposits of the Saskatchewan Basin. These deposits and their host rocks were studied extensively by a large spectrum of isotopic methods on many types of rocks in a widely dispersed area, and for which the numerical statistics became, sometimes, more central in the interpretation than the specificity of the successive events in the host rocks. Full article
(This article belongs to the Special Issue Geochemistry and Geochronology of Mineral Deposits)
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13 pages, 8416 KiB  
Article
Silification of the Mesozoic Rocks Accompanying the Bełchatów Lignite Deposit, Central Poland
by Agnieszka Pękala
Geosciences 2020, 10(4), 141; https://doi.org/10.3390/geosciences10040141 - 12 Apr 2020
Cited by 5 | Viewed by 2665
Abstract
Fieldwork and exploratory study of Poland’s Bełchatów lignite deposit reveals that the Jurassic and Cretaceous sediments with overlying Neogene clays include rocks of greater hardness than the primary composition would indicate. Mineralogical and petrographic tests show the impact of secondary mineralization involving silification [...] Read more.
Fieldwork and exploratory study of Poland’s Bełchatów lignite deposit reveals that the Jurassic and Cretaceous sediments with overlying Neogene clays include rocks of greater hardness than the primary composition would indicate. Mineralogical and petrographic tests show the impact of secondary mineralization involving silification in particular. Transitional and carbonate rocks observed microscopically and subjected to X-ray examination show numerous polymorphic forms of silica replacing carbonate minerals. Opal types A and CT, chalcedony, quartz and microcrystalline quartz are all present. The process of silification observed is a selective and multistage one, with selective activity entailing the displacement and replacement of carbonates from older rocks, mainly Cretaceous opoka-rocks and marls, and Jurassic limestones. The opal fills tectonic fractures and has cemented cracked grains. Cathodoluminescence analysis identifies several generations of silica. The rocks have undergone advanced diagenesis as is evidenced by the recorded metasomatic reactions between minerals. They can further be assumed to be in the locomorphic stage. Such observations are relevant to efforts to reconstruct the origin of the rock matrix, and to the study of its textural features. In addition, the tests run on rocks of the lignite series would seem to be of significant value in identifying and developing associated rocks. Full article
(This article belongs to the Special Issue Geochemistry and Geochronology of Mineral Deposits)
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9 pages, 1412 KiB  
Article
Using Petrogeochemical Modeling to Understand the Relationship between Paleozoic Magmatism in the Kola Region and Its Precambrian History
by Nikolay E. Kozlov, Nikolay O. Sorokhtin and Eugeny V. Martynov
Geosciences 2020, 10(1), 11; https://doi.org/10.3390/geosciences10010011 - 26 Dec 2019
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Abstract
The Kola region hosts numerous Paleozoic massifs of ultrabasic alkaline rocks and carbonatites with deposits of commercially valuable metals, such as iron, tantalum, niobium, and rare earth elements. These magmatic complexes are characterized by high contents of alkaline elements at generally low contents [...] Read more.
The Kola region hosts numerous Paleozoic massifs of ultrabasic alkaline rocks and carbonatites with deposits of commercially valuable metals, such as iron, tantalum, niobium, and rare earth elements. These magmatic complexes are characterized by high contents of alkaline elements at generally low contents of SiO2 and/or Al2O3. In this study, we examined the precursors to the formation of the unique Paleozoic alkaline province through studying the early Precambrian stages in the evolution of the Kola collision area, from where these unique features probably originated. We mathematically modeled the changes in the chemical composition of these rocks. The obtained data can be used for metallogenic forecasting, which indicated a number of Precambrian objects in the region, namely, the Lapland Granulite Belt of the Kola region and granulite belts in Eurasia. The mathematical modeling performed during this research depicted a linear trend that defined the style of the changes in the chemical composition at the transition from the metaultrabasic-basic rocks of the Lapland granulite belt to the group of belts in Eurasia. These differences are statistically significant with respect to the obtained trend (chemical composition projected on the trend), mainly manifested as increased SiO2 and Al2O3 contents with a decreasing total alkalis content, which is opposite to the indicated trends of the changing chemical composition in the Paleozoic alkaline rock units of the Kola region. We concluded that one of the reasons for the unique composition of the Paleozoic magmatism products could be a specific feature of the earlier Neoarchean stages of the tectonic-magmatic activity in the northeastern Baltic Shield, which implies a close relationship between later geological events and the early Precambrian history, at least in the study area. Full article
(This article belongs to the Special Issue Geochemistry and Geochronology of Mineral Deposits)
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