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Mineral Exploration in Weathered and Covered Terrains

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

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 28782

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Special Issue Editors

Dr. Walid Salama

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Guest Editor

CSIRO Mineral Resources, Perth, WA, Australia
Interests: mineral exploration; weathering processes; regolith mapping and landscpae evolution
Special Issues, Collections and Topics in MDPI journals

Dr. Caroline Tiddy

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Guest Editor

Mineral Exploration CRC (MinEx CRC); Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia
Interests: mineral exploration; exploration geochemistry; element dispersion processes; resistate minerals; lithogeochemistry; Proterozoic tectonics; ore genesis

Dr. Ryan Noble

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Guest Editor

CSIRO Mineral Resources, Perth, Western Australia, Australia
Interests: exploration geochemistry; hydrogeochemistry; soil gases; and biogeochemistry

Special Issue Information

Dear Colleagues,

Shallow mineral deposit discoveries are becoming less common, and many world-class deposits are either mined out or decreasing in production. One of the fundamental challenges for the mineral exploration industry in this century is targeting deeper concealed mineral deposits under the Critical Zone. The global increase in demand for mineral resources is driving investment in developing new geochemical tools for vectoring to concealed mineral deposits in weathered and covered terrains. Extensive older terrains of Australia, India, West Africa, Brazil, and China are deeply weathered, and others, such as Canada and Scandinavia, are overlain by recent glacial sediments. Thus, signatures of the mineralisation are obscured, providing challenges for exploring these terrains.

We aim to publish a Special Issue of the journal Minerals that presents a set of articles on “Mineral Exploration in Weathered and Covered Terrains”. The focus of the Special Issue will be on interdisciplinary integrated approaches applied to mineral exploration and targeting deeper buried minerals deposits in and through the Critical Zone. Our Special Issue will cover a broad range of relevant topics of interest, such as:

Landscape evolution of the sedimentary cover sequences in weathered terrains;
Cover mapping using geophysical hyperspectral, remote sensing techniques and machine learning;
Dispersion mechanisms (mechanical, hydromorphic and biological) releasing and enriching ore and pathfinder elements in the Critical Zone;
Laterite and supergene ore deposits;
Near-surface geochemical exploration techniques such as soil, vegetation and termite mounds;
New innovative exploration methods for vectoring toward concealed mineral deposits in weathered and covered terrains;
Mineral exploration in areas covered by glacial sedimentary cover using indicator mineralogy;
Recent advances in hydro-, bio-, isotope geochemistry applied to mineral exploration in weathered terrains.

Thank you and we look forward to receiving your contributions.
The first round of submissions deadline is 30 December 2020.

Dr. Walid Salama
Dr. Caroline Tiddy
Dr. Ryan Noble
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

critical zone
weathering
transported cover
cover mapping
mineral exploration
geochemistry
metal dispersion
indicator minerals
exploration methods

Published Papers (10 papers)

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Research

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14 pages, 6360 KiB

Open AccessArticle

Targeting Paleovalley-Related Ferricrete Units in Yilgarn Craton Using High-Resolution Aeromagnetic Data and Spatial Machine Learning

by Hassan Talebi, Jelena Markov, Walid Salama, Alex Otto, Vasek Metelka, Ravi Anand and Dave Cole

Minerals 2022, 12(7), 879; https://doi.org/10.3390/min12070879 - 13 Jul 2022

Viewed by 1637

Abstract

The ferricrete units (Fe oxide cemented colluvial-alluvial sediment) of the Yilgarn Craton in Western Australia formed during the humid tropical and sub-tropical climates of the Cenozoic. Ferricretes are generally developed on long-lived paleodrainage systems and are products of the ferruginisation of detritus provided by the continuous erosion of upslopes. These iron-rich accumulations can become Au-enriched, as is the case in several locations previously discovered in the Yilgarn Craton; many of these host economic secondary gold deposits (e.g., Moolart Well, Mt Gibson, and Bulchina), typically occurring downslope of low saprolite hills and near paleovalleys (i.e., inset-valleys). Inset-valleys are a common paleotopographic feature buried under Quaternary alluvial and colluvial sedimentary cover. Maps of these ancient channel networks can be used as a proxy for targeting ferricrete gold deposits. These inset-valley systems generally form dendritic and noisy patterns in high-resolution aeromagnetic data due to the presence of maghemite-rich nodules and detrital magnetic pisoliths on their flanks. The main aim of this study was to use high-resolution aeromagnetic data to target ferricrete units related to inset-valleys systems across the Yilgarn Craton. A spatial predictive model was used to learn and predict the geological units of interest from pre-processed aeromagnetic data. The predicted inset-valleys systems were able to confine the exploration space and define a new exploration frontier for ferricrete gold deposits. Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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17 pages, 5912 KiB

Open AccessArticle

Application of the Fine-Grained Soil Prospecting Method in Typical Covered Terrains of Northern China

by Hanliang Liu, Bimin Zhang, Xueqiu Wang, Zhixuan Han, Baoyun Zhang and Guoli Yuan

Minerals 2021, 11(12), 1383; https://doi.org/10.3390/min11121383 - 8 Dec 2021

Cited by 3 | Viewed by 2102

Abstract

In recent years, mineral resources near the surface are becoming scarce, causing focused mineral exploration on concealed deposits in covered terrains. In northern China, covered terrains are widespread and conceal bedrock sequences and mineralization. These represent geochemical challenges for mineral exploration in China. As a deep-penetrating geochemical technology that can reflect the information of deep anomalies, the fine-grained soil prospecting method has achieved ideal test results in arid Gobi Desert covered terrain, semi-arid grassland covered terrain, and alluvium soil covered terrain of northern China. The anomaly range indicated by the fine-grained soil prospecting method is very good with the known ore body location. The corresponding relationship can effectively indicate deep ore bodies and delineate anomalies in unknown areas. Overall, the fine-grained soil prospecting method can be applied to geochemical prospecting and exploration in covered terrains. Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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21 pages, 4875 KiB

Open AccessArticle

Multi-Media Geochemical Exploration in the Critical Zone: A Case Study over the Prairie and Wolf Zn–Pb Deposits, Capricorn Orogen, Western Australia

by Anicia Henne, Nathan Reid, Robert L. Thorne, Samuel C. Spinks, Tenten Pinchand and Alistair White

Minerals 2021, 11(11), 1174; https://doi.org/10.3390/min11111174 - 22 Oct 2021

Cited by 1 | Viewed by 1637

Abstract

In this study, we compared traditional lithochemical sample media (soil) with hydrochemical (groundwater), biogeochemical (plant matter of mulga and spinifex), and other near-surface sample media (ferro-manganese crust), in a case study applied to mineral exploration in weathered terrain, through the critical zone at the fault-hosted Prairie and Wolf Zn–Pb (Ag) deposits in Western Australia. We used multi-element geochemistry analyses to spatially identify geochemical anomalies in samples over known mineralization, and investigated metal dispersion processes. In all near-surface sample media, high concentrations of the metals of interest (Zn, Pb, Ag) coincided with samples proximal to the mineralization at depth. However, the lateral dispersion of these elements differed from regional (several km; groundwater) to local (several 100′s of meters; solid sample media) scales. Zinc in spinifex leaves over the Prairie and Wolf deposits exceeded the total concentrations in all other sample media, while the metal concentrations in mulga phyllodes were not as pronounced, except for Ag, which exceeded the concentrations in all other sample media. These observations indicate potential preferential metal-specific uptake by different media. Pathfinder elements in vegetation and groundwater samples also indicated the Prairie Downs fault zone at the regional (groundwater) and local (vegetation) scale, and are, therefore, potentially useful tools to trace fault systems that host structurally controlled, hydrothermal Zn–Pb mineralization. Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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31 pages, 20117 KiB

Open AccessArticle

Interface Sampling and Indicator Minerals for Detecting the Footprint of the Lancefield North Gold Deposit under the Permian Glacial Cover in Western Australia

by Walid Salama, Michael Verrall, Kirsty Culver and Ravi Anand

Minerals 2021, 11(10), 1131; https://doi.org/10.3390/min11101131 - 14 Oct 2021

Cited by 2 | Viewed by 2493

Abstract

Areas under a thick Permian glacial cover in Western Australia formed as glaciers gouged fresh bedrock and deposited diamictites in disconnected valleys and basins. These areas now present the greatest challenge for mineral exploration in the northeast Yilgarn Craton. At the Lancefield North gold prospect, in the southern part of the Duketon Greenstone Belt, Permian diamictites on average 40 m thick cover unweathered basalt hosting gold mineralization. The basal Permian diamictites consist of fresh, very poorly sorted, angular to rounded, pebble- to boulder-sized, polymictic clasts supported by a matrix of coarse-grained sand and mud. The framework and matrix are cemented by calcite, dolomite, chlorite, and pyrite. These diamictites are stable under alkaline and reducing conditions below the water table. Detrital; fresh sulfides; gold; and opaque oxides, such as pyrite, pyrrhotite, chalcopyrite, sphalerite, arsenopyrite, gersdorffite, cobaltite, pentlandite, scheelite and galena, chromite, ilmenite, and magnetite, are identified in the framework and matrix of the fresh diamictites, and these are identical to those in the primary gold mineralization. Weathering of diamictites and oxidation of detrital and diagenetic sulfides above the water table produced several Fe- and Mn-rich redox fronts and secondary chalcocite and bornite. Interface sampling across the Archean–Permian unconformity shows Au, As, Zn, Ni, Co, and Cd anomalism over the mineralization compared to the background. However, these elements are low in concentration in the redox fronts, where Fe is correlated with As, Cu, Mo, and Sb and Mn is correlated with Co, Ni, and Ba. Gold shows elevated levels in the fresh basal diamictites and decreases in the weathered diamictites over the mineralization. A sampling at or near the Archean–Permian unconformity (interface sampling) only delineates gold mineralization, with no hydromorphic dispersion halo beyond the peripheries. At the Lancefield North prospect, the detrital indicator sulfides are mechanically dispersed up to 500 m to the east of the mineralization in the direction of ice flow. This dispersal distance is controlled by the rough topography of the Archean–Permian unconformity, and it may be greater, but the estimation of the actual distance of transport is limited by the distribution of drill hole locations. Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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21 pages, 6520 KiB

Open AccessArticle

Recognising Mineral Deposits from Cover; A Case Study Using Zircon Chemistry in the Gawler Craton, South Australia

by Adrienne Brotodewo, Caroline Tiddy, Diana Zivak, Adrian Fabris, David Giles, Shaun Light and Ben Forster

Minerals 2021, 11(9), 916; https://doi.org/10.3390/min11090916 - 25 Aug 2021

Cited by 1 | Viewed by 2278

Abstract

Detrital zircon grains preserved within clasts and the matrix of a basal diamictite sequence directly overlying the Carrapateena IOCG deposit in the Gawler Craton, South Australia are shown here to preserve U–Pb ages and geochemical signatures that can be related to underlying mineralisation. The zircon geochemical signature is characterised by elevated heavy rare-earth element fractionation values (Gd_N/Yb_N ≥ 0.15) and high Eu ratios (Eu/Eu* ≥ 0.6). This geochemical signature has previously been recognised within zircon derived from within the Carrapateena orebody and can be used to distinguish zircon associated with IOCG mineralisation from background zircon preserved within stratigraphically equivalent regionally unaltered and altered samples. The results demonstrate that zircon chemistry is preserved through processes of weathering, erosion, transport, and incorporation into cover sequence materials and, therefore, may be dispersed within the cover sequence, effectively increasing the geochemical footprint of the IOCG mineralisation. The zircon geochemical criteria have potential to be applied to whole-rock geochemical data for the cover sequence diamictite in the Carrapateena area; however, this requires understanding of the presence of minerals that may influence the HREE fractionation (Gd_N/Yb_N) and/or Eu/Eu* results (e.g., xenotime, feldspar). Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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27 pages, 10546 KiB

Open AccessArticle

Monazite as an Exploration Tool for Iron Oxide-Copper-Gold Mineralisation in the Gawler Craton, South Australia

by Caroline Tiddy, Diana Zivak, June Hill, David Giles, Jim Hodgkison, Mitchell Neumann and Adrienne Brotodewo

Minerals 2021, 11(8), 809; https://doi.org/10.3390/min11080809 - 26 Jul 2021

Cited by 3 | Viewed by 3316

Abstract

The chemistry of hydrothermal monazite from the Carrapateena and Prominent Hill iron oxide-copper-gold (IOCG) deposits in the IOCG-rich Gawler Craton, South Australia, is used here to define geochemical criteria for IOCG exploration in the Gawler Craton as follows: Monazite associated with IOCG mineralisation: La + Ce > 63 wt% (where La > 22.5 wt% and Ce > 37 wt%), Y and/or Th < 1 wt% and Nd < 12.5 wt%; Intermediate composition monazite (between background and ore-related compositions): 45 wt% < La + Ce < 63 wt%, Y and/or Th < 1 wt%. Intermediate monazite compositions preserving Nd > 12.5 wt% are considered indicative of Carrapateena-style mineralisation; Background compositions: La + Ce < 45 wt% or Y or Th > 1 wt%. Mineralisation-related monazite compositions are recognised within monazite hosted within cover sequence materials that directly overly IOCG mineralisation at Carrapateena. Similar observations have been made at Prominent Hill. Recognition of these signatures within cover sequence materials demonstrates that the geochemical signatures can survive processes of weathering, erosion, transport and redeposition into younger cover sequence materials that overlie older, mineralised basement rocks. The monazite geochemical signatures therefore have the potential to be dispersed within the cover sequence, effectively increasing the geochemical footprint of mineralisation. Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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14 pages, 5338 KiB

Open AccessArticle

Nickel Uptake by Cypress Pine (Callitris glaucophylla) in the Miandetta Area, Australia: Implications for Use in Biogeochemical Exploration

by Kenneth G. McQueen, Augustine Alorbi, Joseph A. Schifano and David R. Cohen

Minerals 2021, 11(8), 808; https://doi.org/10.3390/min11080808 - 26 Jul 2021

Cited by 3 | Viewed by 1831

Abstract

The uptake of Ni and other elements by Callitris glaucophylla (white cypress pine), from weathered ultramafic rocks under varying depths of transported regolith cover, is examined at two sites in the Miandetta area, New South Wales, Australia. Results show that C. glaucophylla can accumulate elevated Ni concentrations in the needles (leaves or phyllodes) from underlying Ni-enriched regolith up to two orders of magnitude above the normal micronutrient levels required for the species. Such uptake levels occur in areas with high total Ni in the soil and regolith despite the relatively low mobility of the Ni due to its presence in a low availability form. This highlights the importance of biotic processes in extracting Ni from soil. The needles of C. glaucophylla could provide an effective and convenient sampling medium for reconnaissance biogeochemical exploration for Ni mineralisation and anomalies where transported regolith is less than ~3 m thick. The study has also demonstrated the potential for in situ analysis of Ni and other elements in the needles by portable XRF. Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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31 pages, 23020 KiB

Open AccessArticle

The (U-Th)/He Chronology and Geochemistry of Ferruginous Nodules and Pisoliths Formed in the Paleochannel Environments at the Garden Well Gold Deposit, Yilgarn Craton of Western Australia: Implications for Landscape Evolution and Geochemical Exploration

by Ravi R. Anand, Martin A. Wells, Melvyn J. Lintern, Louise Schoneveld, Martin Danišík, Walid Salama, Ryan R. P. Noble, Vasek Metelka and Nathan Reid

Minerals 2021, 11(7), 679; https://doi.org/10.3390/min11070679 - 25 Jun 2021

Cited by 2 | Viewed by 4095

Abstract

Ferruginous nodules and pisoliths that cap deeply weathered profiles and transported cover are characteristic of the Yilgarn Craton, Western Australia. Here we show how ferruginous nodules and pisoliths formed in the paleochannel sediments during Miocene can be used to locate buried Au mineralization. Three types of ferruginous nodules and pisoliths were identified in paleochannel sediments and saprolite, representing different parent materials and environments covering the Garden Well Au deposit: (i) ferruginous nodules formed in saprolite on the flanks of the paleochannel (NSP), (ii) ferruginous pisoliths formed in the Perkolilli Shale in the middle of the paleochannel (PPS) and (iii) ferruginous nodules formed in the Wollubar Sandstone at the bottom of the paleochannel (NWS). The appearance, mineralogy and geochemistry of ferruginous nodules and pisoliths vary according to their origin. The PPS and NWS are goethite-rich whereas NSP is a mixture of goethite and hematite which make them all suitable for (U–Th)/He dating. The average age of goethite in the NSP is 14.8 Ma, in the NWS is 11.2 Ma and in the PPS is 18.6 and 14 Ma. The goethite ages in ferruginous nodules and pisoliths are thought to be younger than the underlying saprolite (Paleocene-Eocene) and were formed in different environmental conditions than the underlying saprolite. Anomalous concentrations of Au, As, Cu, Sb, In, Se, Bi, and S in the cores and cortices of the NWS and the PPS reflect the underlying Au mineralization, and thus these nodules and pisoliths are useful sample media for geochemical exploration in this area. These elements originating in mineralized saprolite have migrated both upwards and laterally into the NWS and the PPS, to form spatially large targets for mineral exploration. Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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26 pages, 19980 KiB

Open AccessFeature PaperArticle

Automated Indicator Mineral Analysis of Fine-Grained Till Associated with the Sisson W-Mo Deposit, New Brunswick, Canada

by H. Donald Lougheed, M. Beth McClenaghan, Daniel Layton-Matthews, Matthew I. Leybourne and Agatha Natalie Dobosz

Minerals 2021, 11(2), 103; https://doi.org/10.3390/min11020103 - 21 Jan 2021

Cited by 8 | Viewed by 2274

Abstract

Exploration under thick glacial sediment cover is an important facet of modern mineral exploration in Canada and northern Europe. Till heavy mineral concentrate (HMC) indicator mineral methods are well established in exploration for diamonds, gold, and base metals in glaciated terrain. Traditional methods rely on visual examination of >250 µm HMC material. This study applies mineral liberation analysis (MLA) to investigate the finer (<250 µm) fraction of till HMC. Automated mineralogy (e.g., MLA) of finer material allows for the rapid collection of precise compositional and morphological data from a large number (10,000–100,000) of heavy mineral grains in a single sample. The Sisson W-Mo deposit has a previously documented dispersal train containing the ore minerals scheelite, wolframite, and molybdenite, along with sulfide and other accessory minerals, and was used as a test site for this study. Wolframite is identified in till samples up to 10 km down ice, whereas in previous work on the coarse fraction of till it was only identified directly overlying mineralization. Chalcopyrite and pyrite are found up to 10 km down ice, an increase over 2.5 and 5 km, respectively, achieved in previous work on the coarse fraction of the same HMC. Galena, sphalerite, arsenopyrite, and pyrrhotite are also found up to 10 km down ice after only being identified immediately overlying mineralization using the >250 µm fraction of HMC. Many of these sulfide grains are present only as inclusions in more chemically and robust minerals and would not be identified using optical methods. The extension of the wolframite dispersal train highlights the ability of MLA to identify minerals that lack distinguishing physical characteristics to aid visual identification. Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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Review

Jump to: Research

27 pages, 11414 KiB

Open AccessReview

Current Techniques and Applications of Mineral Chemistry to Mineral Exploration; Examples from Glaciated Terrain: A Review

by Daniel Layton-Matthews and M. Beth McClenaghan

Minerals 2022, 12(1), 59; https://doi.org/10.3390/min12010059 - 31 Dec 2021

Cited by 9 | Viewed by 5200

Abstract

This paper provides a summary of traditional, current, and developing exploration techniques using indicator minerals derived from glacial sediments, with a focus on Canadian case studies. The 0.25 to 2.0 mm fraction of heavy mineral concentrates (HMC) from surficial sediments is typically used for indicator mineral surveys, with the finer (0.25–0.50 mm) fraction used as the default grain size for heavy mineral concentrate studies due to the ease of concentration and separation and subsequent mineralogical identification. Similarly, commonly used indicator minerals (e.g., Kimberlite Indicator Minerals—KIMs) are well known because of ease of optical identification and their ability to survive glacial transport. Herein, we review the last 15 years of the rapidly growing application of Automated Mineralogy (e.g., MLA, QEMSCAN, TIMA, etc) to indicator mineral studies of several ore deposit types, including Ni-Cu-PGE, Volcanogenic Massive Sulfides, and a variety of porphyry systems and glacial sediments down ice of these deposits. These studies have expanded the indicator mineral species that can be applied to mineral exploration and decreased the size of the grains examined down to ~10 microns. Chemical and isotopic fertility indexes developed for bedrock can now be applied to indicator mineral grains in glacial sediments and these methods will influence the next generation of indicator mineral studies. Full article

(This article belongs to the Special Issue Mineral Exploration in Weathered and Covered Terrains)

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