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Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance

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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 (20 May 2019) | Viewed by 50668

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Prof. Dr. Harilaos Tsikos

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Guest Editor

Department of Geology, Rhodes University, Grahamstown 6140, South Africa
Interests: genesis of sedimentary ore deposits; stable isotope geochemistry; paleoceanography

Dr. Albertus Smith

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Guest Editor

Department of Geology, University of Johannesburg, Johannesburg PO Box 524, South Africa
Interests: iron and manganese formations; economic geology and ore-forming processes; geometallurgy

Special Issue Information

Dear Colleagues,

This Special Issue of Minerals, entitled “Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance”, is dedicated to those metalliferous ore deposits that owe their origin to (a combination of) marine and terrestrial sedimentary processes (chemical, biochemical, organic, detrital), as well as metal enrichment processes that typify the supergene weathering environment. These deposits include (but are not restricted to), sedimentary ores of iron and manganese, sedimentary-exhalative massive sulphide deposits, metalliferous black shales, coal, placers and laterites. Improved understanding of the origin of sedimentary ore deposits through time, not only plays a key role in terms of exploration for new resources and optimum exploitation of known ones, but also provides unrivalled windows into the tectonic, climatic and biological evolution of our planet. This Special Issue aims to provide a forum for the latest advances in sedimentary ore deposit research, with special emphasis on the significance of sedimentary ore deposits as archives of ancient and modern biogeochemical cycling and redox evolution; links between classic sedimentary/supergene processes and crustal fluid-flow towards ore-genesis; exploration for and discovery of new resources, including those at the modern seafloor; and novel methodologies in ore extraction and beneficiation.

The first round submission deadline is 30 November 2018.

Prof. Dr. Harilaos Tsikos
Dr. Albertus Smith
Guest Editors

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Keywords

sedimentary ore deposits
ore-genesis
earth evolution
paleoenvironments
exploration
geometallurgy

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Published Papers (8 papers)

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Research

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15 pages, 5357 KiB

Open AccessArticle

Geochemical Study of Weathered Coal, a Co-Substrate for Bioremediation of South African Coal Discard Dumps

by Yvonne van Breugel, Ashton Keith Cowan and Harilaos Tsikos

Minerals 2019, 9(12), 772; https://doi.org/10.3390/min9120772 - 11 Dec 2019

Cited by 3 | Viewed by 6211

Abstract

Coal mining creates large volumes of waste in the form of discard coal that is stockpiled. In South Africa, rehabilitation of coal discard dumps remains a challenge due to reliance on topsoil for establishment of vegetation. Exploitation of fungal bio liquefaction/degradation of coal resulted in the emergence of Fungcoal as a bioprocess for the rehabilitation of coal discard dumps and opencast spoils. In this process, a suite of fungi is used to bio liquefy/degrade recalcitrant waste coal to form a soil-like material which promotes reinvigoration of the microbial component, grass growth, and re-vegetation. Here, the role of outcrop weathered coal as a mineral/carbon source to ensure biologically induced humic acid-like substance enrichment of discard and spoil to increase efficacy of fungi-plant mutualism and stimulate revegetation without the need for topsoil was investigated. Mineralogical, elemental, and pyrolysis gas chromatography-mass spectroscopic analyses show that outcrop weathered coal has decreased volatile material and increased humics, ash, and mineral bound water in comparison to bituminous coal. These changes occur coincidently with decreased C, N, and H contents, and a substantial increase in O concentration. No apparent stoichiometric relationship between sulphur and iron oxide content of weathered coal could be discerned suggesting little residual pyrite in this material and a dominance of oxy-hydroxides of Fe. Organic analysis showed weathered coal to be enriched in C-16 and C-18 fatty acids and the presence of the indicator, 17α(H),21β(H)-homohopane but not the β,β-stereoisomer, was interpreted to indicate that bacteria may only have been active prior to transformation of hard coal into weathered coal. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

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28 pages, 11301 KiB

Open AccessArticle

The Role of Hydrothermal Activity in the Formation of Karst-Hosted Manganese Deposits of the Postmasburg Mn Field, Northern Cape Province, South Africa

by Brenton J. Fairey, Martin J. Timmerman, Masafumi Sudo and Harilaos Tsikos

Minerals 2019, 9(7), 408; https://doi.org/10.3390/min9070408 - 3 Jul 2019

Cited by 5 | Viewed by 7258

Abstract

The Postmasburg Manganese Field (PMF), Northern Cape Province, South Africa, once represented one of the largest sources of manganese ore worldwide. Two belts of manganese ore deposits have been distinguished in the PMF, namely the Western Belt of ferruginous manganese ores and the Eastern Belt of siliceous manganese ores. Prevailing models of ore formation in these two belts invoke karstification of manganese-rich dolomites and residual accumulation of manganese wad which later underwent diagenetic and low-grade metamorphic processes. For the most part, the role of hydrothermal processes and metasomatic alteration towards ore formation has not been adequately discussed. Here we report an abundance of common and some rare Al-, Na-, K- and Ba-bearing minerals, particularly aegirine, albite, microcline, banalsite, sérandite-pectolite, paragonite and natrolite in Mn ores of the PMF, indicative of hydrothermal influence. Enrichments in Na, K and/or Ba in the ores are generally on a percentage level for most samples analysed through bulk-rock techniques. The presence of As-rich tokyoite also suggests the presence of As and V in the hydrothermal fluid. The fluid was likely oxidized and alkaline in nature, akin to a mature basinal brine. Various replacement textures, particularly of Na- and K- rich minerals by Ba-bearing phases, suggest sequential deposition of gangue as well as ore-minerals from the hydrothermal fluid, with Ba phases being deposited at a later stage. The stratigraphic variability of the studied ores and their deviation from the strict classification of ferruginous and siliceous ores in the literature, suggests that a re-evaluation of genetic models is warranted. New Ar-Ar ages for K-feldspars suggest a late Neoproterozoic timing for hydrothermal activity. This corroborates previous geochronological evidence for regional hydrothermal activity that affected Mn ores at the PMF but also, possibly, the high-grade Mn ores of the Kalahari Manganese Field to the north. A revised, all-encompassing model for the development of the manganese deposits of the PMF is then proposed, whereby the source of metals is attributed to underlying carbonate rocks beyond the Reivilo Formation of the Campbellrand Subgroup. The main process by which metals are primarily accumulated is attributed to karstification of the dolomitic substrate. The overlying Asbestos Hills Subgroup banded iron formation (BIF) is suggested as a potential source of alkali metals, which also provides a mechanism for leaching of these BIFs to form high-grade residual iron ore deposits. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

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33 pages, 5915 KiB

Open AccessArticle

Stable Isotope (S, Mg, B) Constraints on the Origin of the Early Precambrian Zhaoanzhuang Serpentine-Magnetite Deposit, Southern North China Craton

by Jie Meng, Houmin Li, Yanhe Li, Zhaochong Zhang, Lixing Li and Zhe Song

Minerals 2019, 9(6), 377; https://doi.org/10.3390/min9060377 - 22 Jun 2019

Cited by 7 | Viewed by 4227

Abstract

The origin of the Zhaoanzhuang serpentine-magnetite deposit in the southern North China Craton (NCC) is highly disputed, with some investigators having proposed an ultramafic origin, whereas others favor a chemical sedimentary origin. These discrepancies are largely due to the difficulty in determining the protolithic characteristics of the highly metamorphosed rocks. Sulfur, magnesium, and boron isotope geochemistry combined with detailed petrography was carried out in this study to constrain the original composition of the Zhaoanzhuang iron orebodies. Anhydrite is present as coarse crystals intergrown with magnetite, indicating that the anhydrite formed simultaneously with the magnetite during metamorphism rather than as a product of later hydrothermal alteration. The anhydrite has a narrow range of positive δ³⁴S values from +19.8 to +22.5‰ with a mean value of +21.1‰. These values are significantly higher than that of typical magmatic sulfur (δ³⁴S = 0 ± 5‰) and deviate away from primary igneous anhydrite towards mantle-sulfur isotopic values, but they are similar to those of marine evaporitic anhydrite and gypsum (~+21‰). The sulfur isotopic compositions of several samples show obvious signs of mass-independent sulfur fractionation (Δ³³S = −0.47‰ to +0.90‰), suggesting that they were influenced by an external sulfur source through a photochemical reaction at low oxygen concentrations, which is consistent with the Neoarchean-Paleoproterozoic atmosphere. Coarse-grained tourmaline from the tourmaline-rich interlayers of the orebodies occurs closely with Mg-rich minerals such as phlogopite, talc, and diopside, indicating that it has a metamorphic origin. The δ¹¹B values of the tourmaline range from −0.2‰ to +3.6‰ with a mean value of +2.0‰, which is much positive relative to that of magmatic tourmaline but is consistent with that of carbonate-derived tourmaline. The magnesium isotopic analyses of the serpentine–magnetite ores and the magnesium-rich wall rocks revealed a wide range of very negative δ²⁶Mg values from −1.20‰ to −0.34‰ with an average value of −0.80‰. The value is higher than that of ultramafic rocks (δ²⁶Mg = −0.25‰) and exhibits minor Mg isotopic fractionation. However, these values are consistent with those of marine carbonate rocks, which have lower δ²⁶Mg values and larger Mg isotopic variations (δ²⁶Mg = −0.45‰ to −4.5‰). Collectively, the S–Mg–B isotopic characteristics of the Zhaoanzhuang iron orebodies clearly indicate a chemical sedimentary origin. The protoliths of these orebodies most likely reflect a series of Fe–Si–Mg-rich marine carbonate rocks with a considerable evaporite component, indicating a carbonate-rich superior-type banded iron formation precipitated in an evaporitic shallow marine sedimentary environment. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

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23 pages, 6886 KiB

Open AccessArticle

The Role of Organic Matter on Uranium Precipitation in Zoovch Ovoo, Mongolia

by Dimitrios Rallakis, Raymond Michels, Marc Brouand, Olivier Parize and Michel Cathelineau

Minerals 2019, 9(5), 310; https://doi.org/10.3390/min9050310 - 18 May 2019

Cited by 36 | Viewed by 5352

Abstract

The Zoovch Ovoo uranium deposit is located in East Gobi Basin in Mongolia. It is hosted in the Sainshand Formation, a Late Cretaceous siliciclastic reservoir, in the lower part of the post-rift infilling of the Mesozoic East Gobi Basin. The Sainshand Formation corresponds to poorly consolidated medium-grained sandy intervals and clay layers deposited in fluvial-lacustrine settings. The uranium deposit is confined within a 60- to 80-m-thick siliciclastic reservoir inside aquifer driven systems, assimilated to roll-fronts. As assessed by vitrinite reflectance (%Rr < 0.4) and molecular geochemistry, the formation has never experienced significant thermal maturation. Detrital organic matter (type III and IV kerogens) is abundant in the Zoovch Ovoo depocenter. In this framework, uranium occurs as: (i) U-rich macerals without any distinguishable U-phase under SEM observation, containing up to 40 wt % U; (ii) U expressed as UO₂ at the rims of large (several millimeters) macerals and (iii) U oxides partially to entirely replacing macerals, while preserving the inherited plant texture. Thus, uranium is accumulated gradually in the macerals through an organic carbon–uranium epigenization process, in respect to the maceral’s chemistry and permeability. Most macerals are rich in S and, to a lesser extent, in Fe. Frequently, Fe and S contents do not fit the stoichiometry of pyrite, although pyrite also occurs as small inclusions within the macerals. The organic matter appears thus as a major redox trap for uranium in this kind of geological setting. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

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17 pages, 8015 KiB

Open AccessArticle

Geochemical Investigations of Fe-Si-Mn Oxyhydroxides Deposits in Wocan Hydrothermal Field on the Slow-Spreading Carlsberg Ridge, Indian Ocean: Constraints on Their Types and Origin

by Samuel Olatunde Popoola, Xiqiu Han, Yejian Wang, Zhongyan Qiu and Ying Ye

Minerals 2019, 9(1), 19; https://doi.org/10.3390/min9010019 - 28 Dec 2018

Cited by 18 | Viewed by 6577

Abstract

We have studied morphology, mineralogy and geochemical characteristics of Fe-oxyhydroxide deposits from metal-enriched sediments of the active (Wocan-1) and inactive (Wocan-2) hydrothermal sites (Carlsberg Ridge, Northwest Indian Ocean). Fe-oxyhydroxide deposits on the Wocan-1 site are reddish-brownish, amorphous and subangular. They occur in association with sulfides (e.g., pyrite, chalcopyrite and sphalerite) and sulfate minerals (e.g., gypsum and barite). The geochemical composition shows enrichment in transition metals (Ʃ (Cu + Co + Zn + Ni) = ~1.19 wt. %) and low (<0.4 wt. %) values of Al/(Al + Fe + Mn) ratio. The Wocan-2 samples show poorly crystallized reddish brown and yellowish Fe-oxyhydroxide, with minor peaks of goethite and manganese oxide minerals. The mineral assemblage includes sulfide and sulfate phases. The geochemical compositions show two distinct types (type-1 and type-2). The type-1 Fe-oxyhydroxides are enriched in transition metals (up to ~1.23 wt. %), with low values of Fe/Ti vs. Al/(Al + Fe + Mn) ratio similar to the Wocan-1 Fe-oxyhydroxides. The type-2 Fe-oxyhydroxides are depleted in transition metals, with Al/(Al + Fe + Mn) ratio of 0.003–0.58 (mean value, 0.04). The ridge flank oxyhydroxides exhibit an extremely low (mean value ~ 0.01) Fe/Mn ratio and a depleted concentration of transition metals. Our results revealed that the Wocan-1 Fe-oxyhydroxides and type-1 Fe-oxyhydroxides of the Wocan-2 site are in the range of Fe-oxyhydroxides deposits that are precipitated by mass wasting and corrosion of pre-existing sulfides. The type-2 Fe-oxyhydroxides are precipitated from sulfide alteration by seawater in an oxygenated environment relative to type-1. The association of biogenic detritus with the oxyhydroxides of the ridge flanks and the low Fe/Mn ratio suggests hydrogenous/biogenic processes of formation and masked hydrothermal signatures with distance away from the Wocan hydrothermal field. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

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19 pages, 6596 KiB

Open AccessArticle

Distribution of Rare Earth Elements plus Yttrium among Major Mineral Phases of Marine Fe–Mn Crusts from the South China Sea and Western Pacific Ocean: A Comparative Study

by Yingzhi Ren, Xiaoming Sun, Yao Guan, Zhenglian Xiao, Ying Liu, Jianlin Liao and Zhengxing Guo

Minerals 2019, 9(1), 8; https://doi.org/10.3390/min9010008 - 23 Dec 2018

Cited by 25 | Viewed by 6850

Abstract

Marine hydrogenetic Fe–Mn crusts on seamounts are known as potential mineral resources of rare earth elements plus yttrium (REY). In recent years, increasing numbers of deposits of Fe–Mn crusts and nodules were discovered in the South China Sea (SCS), yet the enrichment mechanism of REY is yet to be sufficiently addressed. In this study, hydrogenetic Fe–Mn crusts from the South China Sea (SCS) and the Western Pacific Ocean (WPO) were comparatively studied with mineralogy and geochemistry. In addition, we used an in situ REY distribution mapping method, implementing laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and a sequential leaching procedure to investigate the partitioning behavior of REY in the Fe–Mn crusts. The typical Fe–Mn crusts from SCS were mainly composed of quartz, calcite, vernadite (δ-MnO₂), and amorphous Fe oxides/hydroxides (FeOOH). The Fe–Mn crusts from the Central SCS Basin and the WPO contained quartz, δ-MnO₂, FeOOH, todorokite, and phillipsite. Furthermore, geochemical analysis indicated that the typical SCS crusts had a higher growth rate and lower REY concentrations. The LA-ICP-MS mapping results showed that the δ-MnO₂ and FeOOH dominated the occurrence phases of REY in the SCS crusts. Four mineral phases (i.e., easily exchangeable and carbonate, Mn-oxide, amorphous FeOOH, and residual aluminosilicates) in these Fe–Mn crusts were separated by a sequential leaching procedure. In the SCS and WPO crusts, the majority of total REY (ΣREY) was distributed in the Mn-oxide and amorphous FeOOH phases. The post-Archean Australian shale-normalized REY patterns showed that light REY (LREY) and heavy REY (HREY) were preferentially adsorbed onto δ-MnO₂ and FeOOH, respectively. It is noteworthy that ~27% of ΣREY was associated with the residual aluminosilicates phase of the WPO crusts. The La/Al ratios in the aluminosilicates phase of the typical SCS crusts were the values of the upper crust. We conclude that large amounts of terrigenous materials dilute the abundance of REY in the SCS crusts. In addition, the growth rates of Fe–Mn crusts have a negative correlation with the FeOOH-bound and aluminosilicate-bound REY. As a result of the fast growth rates, the SCS crusts contain relatively low concentrations of REY. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

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10 pages, 10453 KiB

Open AccessArticle

Pinnoite Deposit in DaQaidam Saline Lake, Qaidam Basin, China: Hydroclimatic, Sedimentologic, and Geochemical Constraints

by JunQing Yu, Rongchang Hong, Chunliang Gao, Aiying Cheng and Lisa Zhang

Minerals 2018, 8(6), 258; https://doi.org/10.3390/min8060258 - 19 Jun 2018

Cited by 7 | Viewed by 3881

Abstract

Mg-borates were traditionally thought to be diagenetic products of other primary borate minerals. Here we report results from the study of pinnoite deposit from DaQaidam saline lake, indicating that pinnoite minerals are primary in origin. Within the detecting limit of X-ray powder diffraction analysis (XRD) analysis, no other borate minerals than pinnoite are detected from the Mg-borate deposit. The cemented pinnoite orebody shows the sedimentary structure of light-dark lamination couplets, which signal marked seasonal variations in brine chemistry. The scanning electronic microscopy coupled with an energy dispersive X-ray spectrometer (SEM-EDX) examination reveals that all pinnoite minerals displayed euhedral, giving no indication of diagenetic origin. A marked shift in lithology from clastic sediment to evaporitic deposit reflects a critical change in sedimentation regime associated with abrupt changes in hydroclimatic conditions. The deposition of the pinnoite ore-layer containing abundant hydromagnesite marked the beginning of the evaporite formation and the end of the clastic deposition. This suggests that aridification occurred abruptly and the saline lake was much more alkaline than today in the early-stage of the evaporite deposition. The intensified summer evaporation and seasonal variations in water chemistry brought about a shallow to nearly desiccated paleo-lake with pH exceeding 9.3, Mg/Ca ratio >39, and boron concentration >600 mg/L, which favored pinnoite precipitation and the formation of pinnoite deposit in the central DaQaidam saline lake. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

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Review

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20 pages, 6142 KiB

Open AccessReview

The Potential for REE and Associated Critical Metals in Coastal Sand (Placer) Deposits of Greece: A Review

by Argyrios Papadopoulos, Ioannis T. Tzifas and Harilaos Tsikos

Minerals 2019, 9(8), 469; https://doi.org/10.3390/min9080469 - 31 Jul 2019

Cited by 14 | Viewed by 8771

Abstract

The rare earth elements (REEs) are characterized by the European Union (EU) as critical raw materials with a significant risk of supply because of their broad utility in both traditional and emerging technological applications. The growing demand for REE has caused a flurry in the search for new REE deposits in Europe and elsewhere in the world, and is also linked to rising exploitation efforts in a variety of geological settings. To this end, Greece appears to be a promising candidate to become a leading EU country in terms of REE by virtue of its natural endowment in sedimentary heavy mineral deposits (placers) along its long coastline. The present review focuses on the distribution, abundance, and bulk geochemistry of REEs and other critical metals (Ta, Nb, Co) associated with placer deposits of Greece, and specifically with geologically young heavy mineral sand accumulations developed proximal to felsic plutonic source rocks. These deposits are also enriched in the actinides uranium (U) and thorium (Th), as both of these metals are typically associated with REE-rich minerals such as xenotime, monazite, thorite, allanite, and zircon. Previous studies have employed a variety of analytical techniques down to nano-meter scale with the aim to elucidate the mineralogy and distribution of REE and associated actinides in Greek beach placers. In view of this mineralogically-intensive background, the present review focuses chiefly on bulk geochemical characteristics of the same deposits and the variations thereof between two major geographical regions (northern Greece, southern Aegean) and across individual placer occurrences within them. In this framework, we present comprehensive compositional comparisons between the different deposits, highlighting the geological sub-environments wherein they occur, their distinctive sources and geochemical signatures, and their potential economic significance in terms of REE and other critical metal enrichments where applicable. Full article

(This article belongs to the Special Issue Sedimentary Ore Deposits: Origin, Exploitation, Paleoenvironmental Significance)

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