Minerals

27 pages, 5472 KiB

Open AccessArticle

Abyssal Peridotite as a Component of Forearc Mantle: Inference from a New Mantle Xenolith Suite of Bankawa in the Southwest Japan Arc

by Shoji Arai, Akihiro Tamura, Makoto Miura and Kazuma Seike

Minerals 2018, 8(11), 540; https://doi.org/10.3390/min8110540 - 21 Nov 2018

Cited by 17 | Viewed by 7202

Abstract

Lithology and petrologic nature of the forearc mantle have been left unclear due to the very limited sampling to date. Here, we present petrological data on a forearc peridotite suite obtained as xenoliths in an alkali basalt dike (7.5 Ma) from the Bankawa [...] Read more.

Lithology and petrologic nature of the forearc mantle have been left unclear due to the very limited sampling to date. Here, we present petrological data on a forearc peridotite suite obtained as xenoliths in an alkali basalt dike (7.5 Ma) from the Bankawa area in the Southwest Japan arc for our better understanding of the forearc mantle. The host alkali basalt is of asthenosphere origin, and passed through a slab window with slight chemical modification by the slab-derived component. The Bankawa peridotite suite is comprised of lherzolites, which contain various amounts of secondary phlogopite and were metasomatized to various degrees. The least metasomatized lherzolite exhibits Fo₉₁ of olivine, Cr/(Cr + Al) = 0.3 of chromian spinel, and depletion of middle to light rare-earth elements in clinopyroxene, and is overall similar to an abyssal lherzolite. It had originally formed at the proto-Pacific Ocean and then was trapped at a eastern margin of Eurasian continent by initiation of subduction. The forearc mantle peridotite formed as a residue of proto-arc magma formation is depleted harzburgite as represented by the peridotites obtained from the forearc seafloor, but can be less depleted abyssal peridotite if being devoid of partial melting or reaction with magmas after entrapment. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Mineralogy of the Mantle as Tools to Read Messages from the Earth’s Interior)

► Show Figures

Figure 1

20 pages, 8533 KiB

Open AccessArticle

In Vivo X-ray Computed Tomography Investigations of Crack Damage Evolution of Cemented Waste Rock Backfills (CWRB) under Uniaxial Deformation

by Yu Wang, Changhong Li, Zhiqiang Hou, Xuefeng Yi and Xiaoming Wei

Minerals 2018, 8(11), 539; https://doi.org/10.3390/min8110539 - 21 Nov 2018

Cited by 15 | Viewed by 3438

Abstract

Cemented waste rock backfill (CWRB), which is a mixture of tailings, waste rock, cement, and water, is subjected to combination actions in underground mining operations and has been widely used in deep resource mining. While the strength requirement and macroscopic deformation behaviors of [...] Read more.

Cemented waste rock backfill (CWRB), which is a mixture of tailings, waste rock, cement, and water, is subjected to combination actions in underground mining operations and has been widely used in deep resource mining. While the strength requirement and macroscopic deformation behaviors of CWRB have been well studied, the mesoscopic damage evolution mechanisms are still not well understood. In this work, a CWRB sample with a waste rock proportion of 30% was studied with a uniaxial compression test under tomographic monitoring, using a 450 kV industrial X-ray computed tomography (CT). Clear CT images, CT value analysis, crack identification, and extraction reveal that CWRB damage evolution is extremely inhomogeneous and affected by the waste rock size, shape, and distribution. Furthermore, the crack initiation, propagation, and coalescence behaviors are limited to the existing waste rocks. When deformation grows to a certain extent, the cracks demonstrate an interlocking phenomenon and their propagation paths are affected by the waste rocks, which may improve the ability to resist compressive deformation. Volumetric dilatancy caused by the damage and cracking behavior has closed a link with the meso-structural changes, which are controlled by the interactions between the waste rocks and the cemented tailing paste. Full article

(This article belongs to the Special Issue Backfilling Materials for Underground Mining)

► Show Figures

Figure 1

21 pages, 45558 KiB

Open AccessEditor’s ChoiceArticle

Underground Vertical Seismic Profiling with Conventional and Fiber-Optic Systems for Exploration in the Kylylahti Polymetallic Mine, Eastern Finland

by Marko Riedel, Calin Cosma, Nicoleta Enescu, Emilia Koivisto, Kari Komminaho, Katri Vaittinen and Michał Malinowski

Minerals 2018, 8(11), 538; https://doi.org/10.3390/min8110538 - 20 Nov 2018

Cited by 21 | Viewed by 6520

Abstract

Seismic reflection methods have been used for the exploration of mineral resources for several decades. However, despite their unmatched spatial resolution and depth penetration, they only have played a minor role in mineral discoveries so far. Instead, mining and exploration companies have traditionally [...] Read more.

Seismic reflection methods have been used for the exploration of mineral resources for several decades. However, despite their unmatched spatial resolution and depth penetration, they only have played a minor role in mineral discoveries so far. Instead, mining and exploration companies have traditionally focused more on the use of potential field, electric and electromagnetic methods. In this context, we present a case study of an underground Vertical Seismic Profiling (VSP) experiment, which was designed to image a (semi-)massive sulfide deposit located in the Kylylahti polymetallic mine in eastern Finland. For the measurement, we used a conventional VSP with three-component geophones and a novel fiber-optic Distributed Acoustic Sensing (DAS) system. Both systems were deployed in boreholes located nearby the target sulfide deposit, and used in combination with an active seismic source that was fired from within the underground tunnels. With this setup, we successfully recorded seismic reflections from the deposit and its nearby geological contrasts. The recording systems provided data with a good signal-to-noise ratio and high spatial resolution. In addition to the measurements, we generated a realistic synthetic dataset based on a detailed geological model derived from extensive drilling data and petrophysical laboratory analysis. Specific processing and imaging of the acquired and synthetic datasets yielded high-resolution reflectivity images. Joint analysis of these images and cross-validation with lithological logging data from 135 nearby boreholes led to successful interpretation of key geological contacts including the target sulfide mineralization. In conclusion, our experiment demonstrates the value of in-mine VSP measurements for detailed resource delineation in a complex geological setting. In particular, we emphasize the potential benefit of using fiber-optic DAS systems, which provide reflection data at sufficient quality with less logistical effort and a higher acquisition rate. This amounts to a lower total acquisition cost, which makes DAS a valuable tool for future mineral exploration activities. Full article

(This article belongs to the Special Issue Seismic Methods in Mineral Exploration)

► Show Figures

Figure 1

23 pages, 13843 KiB

Open AccessArticle

Mineralogical and Geochemical Constraints on Magma Evolution and Late-Stage Crystallization History of the Breivikbotn Silicocarbonatite, Seiland Igneous Province in Northern Norway: Prerequisites for Zeolite Deposits in Carbonatite Complexes

by Dmitry R. Zozulya, Kåre Kullerud, Erling K. Ravna, Yevgeny E. Savchenko, Ekaterina A. Selivanova and Marina G. Timofeeva

Minerals 2018, 8(11), 537; https://doi.org/10.3390/min8110537 - 20 Nov 2018

Cited by 3 | Viewed by 5158

Abstract

The present work reports on new mineralogical and whole-rock geochemical data from the Breivikbotn silicocarbonatite (Seiland igneous province, North Norway), allowing conclusions to be drawn concerning its origin and the role of late fluid alteration. The rock shows a rare mineral association: calcite [...] Read more.

The present work reports on new mineralogical and whole-rock geochemical data from the Breivikbotn silicocarbonatite (Seiland igneous province, North Norway), allowing conclusions to be drawn concerning its origin and the role of late fluid alteration. The rock shows a rare mineral association: calcite + pyroxene + amphibole + zeolite group minerals + garnet + titanite, with apatite, allanite, magnetite and zircon as minor and accessory minerals, and it is classified as silicocarbonatite. Calcite, titanite and pyroxene (Di_36–46 Acm_22–37 Hd_14–21) are primarily magmatic minerals. Amphibole of mainly hastingsitic composition has formed after pyroxene at a late-magmatic stage. Zeolite group minerals (natrolite, gonnardite, Sr-rich thomsonite-(Ca)) were formed during hydrothermal alteration of primary nepheline by fluids/solutions with high Si-Al-Ca activities. Poikilitic garnet (Ti-bearing andradite) has inclusions of all primary minerals, amphibole and zeolites, and presumably crystallized metasomatically during a late metamorphic event (Caledonian orogeny). Whole-rock chemical compositions of the silicocarbonatite differs from the global average of calciocarbonatites by elevated silica, aluminium, sodium and iron, but show comparable contents of trace elements (REE, Sr, Ba). Trace element distributions and abundances indicate within-plate tectonic setting of the carbonatite. The spatial proximity of carbonatite and alkaline ultramafic rock (melteigite), the presence of “primary nepheline” in carbonatite together with the trace element distributions indicate that the carbonatite was derived by crystal fractionation of a parental carbonated foidite magma. The main prerequisites for the extensive formation of zeolite group minerals in silicocarbonatite are revealed. Full article

(This article belongs to the Special Issue Arctic Mineral Resources: Science and Technology)

► Show Figures

Figure 1

23 pages, 4732 KiB

Open AccessArticle

Simulation of a Mining Value Chain with a Synthetic Ore Body Model: Iron Ore Example

by Viktor Lishchuk, Cecilia Lund, Pertti Lamberg and Elena Miroshnikova

Minerals 2018, 8(11), 536; https://doi.org/10.3390/min8110536 - 18 Nov 2018

Cited by 11 | Viewed by 10451

Abstract

Reconciliation of geological, mining and mineral processing information is a costly and time demanding procedure with high uncertainty due to incomplete information, especially during the early stages of a project, i.e., pre-feasibility, feasibility studies. Lack of information at those project stages can be [...] Read more.

Reconciliation of geological, mining and mineral processing information is a costly and time demanding procedure with high uncertainty due to incomplete information, especially during the early stages of a project, i.e., pre-feasibility, feasibility studies. Lack of information at those project stages can be overcome by applying synthetic data for investigating different scenarios. Generation of the synthetic data requires some minimum sparse knowledge already available from other parts of the mining value chain, i.e., geology, mining, mineral processing. The aim of the paper is to describe how to establish and construct a synthetic testing environment, or “synthetic ore body model” for data integration by using a synthetic deposit, mine production, constrained by a mine plan, and a simulated beneficiation process. The approach uses quantitative mineralogical data and liberation information for process simulation. The results of geological and process data integration are compared with the real case data of an apatite iron ore. The discussed approach allows for studying the implications in downstream processes caused by changes in upstream parts of the mining value chain. It also opens the possibility of optimising sampling campaigns by investigating different synthetic drilling scenarios including changes to the spacing between synthetic drill holes, composite length, drill hole orientation and assayed parameters. A synthetic deposit model can be a suitable tool for testing different scenarios for implementation of geometallurgical programs and also an educational tool for universities and companies. Full article

(This article belongs to the Special Issue Geometallurgy)

► Show Figures

Figure 1

10 pages, 4175 KiB

Open AccessArticle

Lead–Antimony Sulfosalts from Tuscany (Italy). XXIV. Crystal Structure of Thallium-Bearing Chovanite, TlPb₂₆(Sb,As)₃₁S₇₂O, from the Monte Arsiccio Mine, Apuan Alps

by Cristian Biagioni, Yves Moëlo, Natale Perchiazzi, Nicola Demitri and Giovanni Orazio Lepore

Minerals 2018, 8(11), 535; https://doi.org/10.3390/min8110535 - 18 Nov 2018

Cited by 4 | Viewed by 3933

Abstract

A thallium-bearing variety of the lead–antimony oxysulfosalt chovanite from the Monte Arsiccio mine (Apuan Alps, Tuscany, Italy) has been reexamined. It occurs as thin, ribbon-like crystals, black in color, up to 5 mm in length in vugs of dolomite ± baryte ± quartz [...] Read more.

A thallium-bearing variety of the lead–antimony oxysulfosalt chovanite from the Monte Arsiccio mine (Apuan Alps, Tuscany, Italy) has been reexamined. It occurs as thin, ribbon-like crystals, black in color, up to 5 mm in length in vugs of dolomite ± baryte ± quartz veins embedded in the metadolostone of the Sant’Olga level. Associated minerals are rouxelite, robinsonite, sphalerite, valentinite, baryte, dolomite, quartz, and Ba-rich K-feldspar. Chemical analysis pointed to contents of Tl up to 0.86 apfu, corresponding to the ideal chemical formula TlPb₂₆(Sb,As)₃₁S₇₂O. The structural role of thallium has been investigated using single-crystal X-ray diffraction using synchrotron radiation (λ = 0.59040 Å). Thallium-rich chovanite is monoclinic, space group P2₁/c, with unit-cell parameters a = 34.280(3), b = 8.2430(7), c = 48.457(4) Å, β = 106.290(4)°, and V = 13143(2) Å³. The crystal structure was refined to a final R₁ = 0.083 for 12,052 reflections with F_o > 4σ(F_o) and 1210 refined parameters. The general features of thallium-rich chovanite agree with those of chovanite. Thallium is present as Tl⁺; it is disordered among two mixed (Pb/Tl) positions, with a Tl/Pb atomic ratio below 1, that precludes this compound to be a new species. Full article

(This article belongs to the Special Issue Thallium: Mineralogy, Geochemistry and Ore Processes)

► Show Figures

Figure 1

20 pages, 6803 KiB

Open AccessArticle

Synergistic Use of UAV and USV Data and Petrographic Analyses for the Investigation of Beachrock Formations: A Case Study from Syros Island, Aegean Sea, Greece

by Konstantinos G. Nikolakopoulos, Paraskevi Lampropoulou, Elias Fakiris, Dimitris Sardelianos and George Papatheodorou

Minerals 2018, 8(11), 534; https://doi.org/10.3390/min8110534 - 17 Nov 2018

Cited by 39 | Viewed by 5127

Abstract

Up until the last ten years, remote sensing data and especially high-resolution satellite data and airphotos were mainly used in shallow water mapping. The evolution and low cost of unmanned aerial vehicles (UAVs) provides a new tool for coastal area monitoring. This paper [...] Read more.

Up until the last ten years, remote sensing data and especially high-resolution satellite data and airphotos were mainly used in shallow water mapping. The evolution and low cost of unmanned aerial vehicles (UAVs) provides a new tool for coastal area monitoring. This paper presents the synergistic use of a small commercial UAV and an unmanned surface vehicle (USV) for beachrock mapping in Syros Island, Greece. RGB images collected with a quadcopter were processed using Structure from Motion (SFM) photogrammetry in order to create digital surface models (DSMs) and orthophotos of the coastline. A beachrock lying in shallow waters was detected and mapped using the UAV derived products. At the same time, a USV equipped with a compact side scan sonar (SSS) and bathymetric sonar system, provided the shape of the beachrock by mosaicking the backscatter strength of the SSS. In order to evaluate the results of the UAV and USV data derivatives, the beachrock perimeter and its depth were also mapped using a differential global navigation satellite system (GNSS) receiver. During the fieldwork, samples from the beachrock were collected and analyzed in the laboratory. The mineralogical composition of the bulk samples was determined by powder X-ray diffraction (XRD). Further petrographic study was also performed by petrographic polarizing microscope, macroscope, and scanning electron microscopy (SEM). Beachrock samples are classified as fine to medium grain sandstones and conglomerates. The mineral compositions of their grains and lithoclasts reflect the bedrocks of Syros Island (mainly metamorphic rocks) while a micritic high-Mg calcite constitutes the cement of these rocks. Full article

(This article belongs to the Special Issue Unmanned Aerial Systems (UAS) in Geology and Environmental Modelling)

► Show Figures

Figure 1

22 pages, 17886 KiB

Open AccessArticle

Depositional Architecture and Facies of a Complete Reef Complex Succession: A Case Study of the Permian Jiantianba Reefs, Western Hubei, South China

by Beichen Chen, Xinong Xie, Ihsan S. Al-Aasm, Wu Feng and Mo Zhou

Minerals 2018, 8(11), 533; https://doi.org/10.3390/min8110533 - 16 Nov 2018

Cited by 3 | Viewed by 6459

Abstract

The Upper Permian Changhsingian Jiantissanba reef complex is a well-known platform marginal reef, located in the western Hubei Province, China. Based on field observations and lithological analysis of the entire exposed reef complex, 12 reef facies have been distinguished according to their sedimentary [...] Read more.

The Upper Permian Changhsingian Jiantissanba reef complex is a well-known platform marginal reef, located in the western Hubei Province, China. Based on field observations and lithological analysis of the entire exposed reef complex, 12 reef facies have been distinguished according to their sedimentary components and growth fabrics. Each of the lithofacies is associated with a specific marine environment. Vertically traceable stratal patterns reveal 4 types of the lithologic associations of the Jiantianba reef: (1) heterozoan reef core association: developed in the deep marginal platform with muddy composition; (2) photozoan reef core association developed within the photic zone; (3) tide-controlled reef crest association with tidal-dominated characteristic of lithofacies in the shallow water; and (4) reef-bank association dominated by bioclastic components. The entire reef complex shows a complete reef succession revealing a function of the wave-resistant and morphological units. This study displays a complete sedimentary succession of Jiantianba reef, which provides a more accurate and comprehensive description of the reef lithofacies and a better understanding of the structure and composition of organic reefs. Full article

(This article belongs to the Special Issue Mineralogy, Petrology, Geochemistry and Diagenesis of Carbonate Minerals and Rocks)

► Show Figures

Figure 1

13 pages, 6159 KiB

Open AccessArticle

Chemical Composition and Petrogenetic Implications of Apatite in the Khibiny Apatite-Nepheline Deposits (Kola Peninsula)

by Lia Kogarko

Minerals 2018, 8(11), 532; https://doi.org/10.3390/min8110532 - 16 Nov 2018

Cited by 31 | Viewed by 6090

Abstract

Khibiny, one of the largest of the world’s peralkaline intrusions, hosts gigantic apatite deposits. Apatite is represented by F-apatite and it contains exceptionally high concentration of SrO. (4.5 wt % on average) and increased amounts of rare earth elements (REEs; up to 8891 [...] Read more.

Khibiny, one of the largest of the world’s peralkaline intrusions, hosts gigantic apatite deposits. Apatite is represented by F-apatite and it contains exceptionally high concentration of SrO. (4.5 wt % on average) and increased amounts of rare earth elements (REEs; up to 8891 ppm). Such enrichment of apatite ores in REEs defined Khibiny deposit as world-class deposit with resources reaching several millions tons REE₂O₃. Apatite from the Khibina alkaline complex is characterized by the significant enrichment in light REEs relative to the heavy REEs (with average Ce/Yb ratio of 682) and the absence of a negative Eu anomaly. The obtained geochemical signature of apatite suggests a residual character of the Khibiny alkaline magma and it indicates that the differentiation of the primary olivine-melanephelinitic magma developed without fractionation of plagioclase which is the main mineral-concentrator of Sr and Eu in basaltic magmatic systems. The compositional evolution of the Khibiny apatite in the vertical section of the intrusion reflects primary fractionation processes in the alkaline magma that differentiated in situ. The main mechanism for the formation of the apatite-nepheline deposits was the gravitational settling of large nepheline crystals in the lower part of the magma chamber, while very small apatite crystals were suspended in a convective magma, and, together with the melt, were concentrated in its upper part of the magmatic chamber. Full article

(This article belongs to the Special Issue Arctic Mineral Resources: Science and Technology)

► Show Figures

Figure 1

16 pages, 4080 KiB

Open AccessArticle

The Gersdorffite-Bismuthinite-Native Gold Association and the Skarn-Porphyry Mineralization in the Kamariza Mining District, Lavrion, Greece

by Panagiotis Voudouris, Constantinos Mavrogonatos, Branko Rieck, Uwe Kolitsch, Paul G. Spry, Christophe Scheffer, Alexandre Tarantola, Olivier Vanderhaeghe, Emmanouil Galanos, Vasilios Melfos, Stefanos Zaimis, Konstantinos Soukis and Adonis Photiades

Minerals 2018, 8(11), 531; https://doi.org/10.3390/min8110531 - 16 Nov 2018

Cited by 12 | Viewed by 6166

Abstract

Vein-type Pb-Ni-Bi-Au-Ag mineralization at the Clemence deposit in the Kamariza and “km3” in the Lavrion area, was synchronous with the intrusion of a Miocene granodiorite body and related felsic and mafic dikes and sills within marbles and schists in the footwall of (and [...] Read more.

Vein-type Pb-Ni-Bi-Au-Ag mineralization at the Clemence deposit in the Kamariza and “km3” in the Lavrion area, was synchronous with the intrusion of a Miocene granodiorite body and related felsic and mafic dikes and sills within marbles and schists in the footwall of (and within) the Western Cycladic detachment system. In the Serpieri deposit (Kamariza area), a porphyry-style pyrrhotite-arsenopyrite mineralized microgranitic dike is genetically related to a garnet-wollastonite bearing skarn characterized by a similar base metal and Ni (up to 219 ppm) enrichment. The Ni–Bi–Au association in the Clemence deposit consists of initial deposition of pyrite and arsenopyrite followed by an intergrowth of native gold-bismuthinite and oscillatory zoned gersdorffite. The zoning is related to variable As, Ni, and Fe contents, indicating fluctuations of arsenic and sulfur fugacity in the hydrothermal fluid. A late evolution towards higher sulfur fugacity in the mineralization is evident by the deposition of chalcopyrite, tennantite, enargite, and galena rimming gersdorffite. At the “km3” locality, Ni sulfides and sulfarsenides, vaesite, millerite, ullmannite, and polydymite, are enclosed in gersdorffite and/or galena. The gersdorffite is homogenous and contains less Fe (up to 2 wt.%) than that from the Clemence deposit (up to 9 wt.%). Bulk ore analyses of the Clemence ore reveal Au and Ag grades both exceeding 100 g/t, Pb and Zn > 1 wt.%, Ni up to 9700 ppm, Co up to 118 ppm, Sn > 100 ppm, and Bi > 2000 ppm. The “km3” mineralization is enriched in Mo (up to 36 ppm), Ni (>1 wt.%), and Co (up to 1290 ppm). Our data further support a magmatic contribution to the ore-forming fluids, although remobilization and leaching of metals from previous mineralization and/or host rocks, through the late involvement of non-magmatic fluid in the ore system, cannot be excluded. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Mineral Science)

► Show Figures

Figure 1

16 pages, 7168 KiB

Open AccessArticle

Spatial Mapping of the Rock Quality Designation Using Multi-Gaussian Kriging Method

by Nasser Madani, Saffet Yagiz and Amoussou Coffi Adoko

Minerals 2018, 8(11), 530; https://doi.org/10.3390/min8110530 - 15 Nov 2018

Cited by 11 | Viewed by 4830

Abstract

The rock quality designation is an important input for the analysis and design of rock structures as reliable spatial modeling of the rock quality designation (RQD) can assist in designing and planning mines more efficiently. The aim of this paper is to model [...] Read more.

The rock quality designation is an important input for the analysis and design of rock structures as reliable spatial modeling of the rock quality designation (RQD) can assist in designing and planning mines more efficiently. The aim of this paper is to model the spatial distribution of the RQD using the multi-Gaussian kriging approach as an alternative to the non-linear geostatistical technique which has shown some limitations. To this end, 470 RQD datasets were collected from 9 boreholes pertaining to the Gazestan ore deposit in Iran. The datasets were declustered then transformed into Gaussian distribution. To ensure the model spatial continuity, variogram analysis was first performed. The elevation 150 m with a grid of 5 m × 5 m × 5 m was selected to illustrate the methodology. Surface maps showing the RQD classes (very poor, poor, fair, good, and very good) with their associated probability were established. A cross-validation method was used to check the obtained model. The validation results indicated good prediction of the local variability. In addition, the associated uncertainty was quantified on the basis of the conditional distributions and the accuracy plot agreed with the overall results. It is concluded that the proposed model could be used to produce a reliable RQD map. Full article

► Show Figures

Figure 1

12 pages, 2728 KiB

Open AccessFeature PaperArticle

Silician Magnetite from the Copiapó Nordeste Prospect of Northern Chile and Its Implication for Ore-Forming Conditions of Iron Oxide–Copper–Gold Deposits

by Elías González, Shoji Kojima, Yoshihiko Ichii, Takayuki Tanaka, Yoshikazu Fujimoto and Takeyuki Ogata

Minerals 2018, 8(11), 529; https://doi.org/10.3390/min8110529 - 14 Nov 2018

Cited by 7 | Viewed by 5214

Abstract

Silica-bearing magnetite was recognized in the Copiapó Nordeste prospect as the first documented occurrence in Chilean iron oxide–copper–gold (IOCG) deposits. The SiO₂-rich magnetite termed silician magnetite occurs in early calcic to potassic alteration zones as orderly oscillatory layers in polyhedral magnetite [...] Read more.

Silica-bearing magnetite was recognized in the Copiapó Nordeste prospect as the first documented occurrence in Chilean iron oxide–copper–gold (IOCG) deposits. The SiO₂-rich magnetite termed silician magnetite occurs in early calcic to potassic alteration zones as orderly oscillatory layers in polyhedral magnetite and as isolated discrete grains, displaying perceptible optical differences in color and reflectance compared to normal magnetite. Micro-X-ray fluorescence and electron microprobe analyses reveal that silician magnetite has a significant SiO₂ content with small amounts of other “impure” components, such as Al₂O₃, CaO, MgO, TiO₂, and MnO. The oscillatory-zoned magnetite is generally enriched in SiO₂ (up to 7.5 wt %) compared to the discrete grains. The formation of silician magnetite is explained by the exchange reactions between 2Fe (III) and Si (IV) + Fe (II), with the subordinate reactions between Fe (III) and Al (III) and between 2Fe (II) and Ca (II) + Mg (II). Silician magnetite with high concentrations of SiO₂ (3.8–8.9 wt %) was similarly noted in intrusion-related magmatic–hydrothermal deposits including porphyry- and skarn-type deposits. This characteristic suggests that a hydrothermal system of relatively high-temperature and hypersaline fluids could be a substantial factor in the formation of silician magnetite with high SiO₂ contents. Full article

(This article belongs to the Special Issue Iron Oxide-Copper-gold (IOCG) Deposits)

► Show Figures

Figure 1

26 pages, 8678 KiB

Open AccessArticle

Petrology, Geochronology and Geochemistry of Late Triassic Alkaline Rocks of the Bailinchuan District in Liaodong Peninsula, Northeast China

by Xihui Cheng, Jiuhua Xu, Hao Wei, Fuquan Yang, Hui Zhang and Guorui Zhang

Minerals 2018, 8(11), 528; https://doi.org/10.3390/min8110528 - 13 Nov 2018

Cited by 7 | Viewed by 5154

Abstract

The Bailinchuan alkaline syenite (BAS) is located in the easternmost part of the Triassic alkaline magmatic belt along the northern North China Craton (NCC). Based on a detailed study of the zircon U–Pb age, petrological, and geochemical data of the complex, the characteristics [...] Read more.

The Bailinchuan alkaline syenite (BAS) is located in the easternmost part of the Triassic alkaline magmatic belt along the northern North China Craton (NCC). Based on a detailed study of the zircon U–Pb age, petrological, and geochemical data of the complex, the characteristics of the magmas system, petrogenesis and the nature of mantle source provide new constraints on the origin and tectonic setting of the Triassic alkaline belt. The BAS is composed of alkaline syenite and/or aegirine-nepheline syenite, with zircon U–Pb age of 226–229 Ma. Aegirine, Na-rich augite, biotite, orthoclase, and nepheline are the major minerals. Most of the zircons selected for the analysis show fine-scale to weak oscillatory growth zoning in CL images, suggesting a magmatic origin. Mineralogy, petrology and geochemical studies show that the parental magma of the BAS is SiO₂-undersaturated, potassic, and is characterized by high contents of CaO, Fe₂O₃, K₂O, Na₂O. The BAS originated from a phlogopite-rich, enriched lithospheric mantle source in a garnet-stable area. The occurrence of the BAS, together with many other alkaline complexes of similar ages (235–209 Ma) in the northern NCC during the Late Triassic implies that the lithospheric mantle beneath the northern NCC was previously metasomatized by melts/fluids. Bailinchuan Late Triassic syenites were formed in a post-collisional extensional setting, which provides time constraints on the major geodynamic setting at the northern NCC. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

► Show Figures

Graphical abstract

14 pages, 6194 KiB

Open AccessArticle

Breakage Characterization of Grinding Media Based on Energy Consumption and Particle Size Distribution: Hexagons versus Cylpebs

by Caibin Wu, Ningning Liao, Guiming Shi and Liangliang Zhu

Minerals 2018, 8(11), 527; https://doi.org/10.3390/min8110527 - 13 Nov 2018

Cited by 7 | Viewed by 4253

Abstract

The grinding performance of hexagon grinding media particles has been compared with that of cylpebs grinding media particles. A batch grinding test was conducted using equal masses of hexagons and cylpebs. The particle size distribution and energy consumption during grinding of the ground [...] Read more.

The grinding performance of hexagon grinding media particles has been compared with that of cylpebs grinding media particles. A batch grinding test was conducted using equal masses of hexagons and cylpebs. The particle size distribution and energy consumption during grinding of the ground product were analyzed, and the relationships among the specific surface area, bulk density, energy consumption, and t₁₀ value are discussed. Under the same grinding conditions, the grinding capacity of hexagons was inferior to that of cylpebs. However, as the particle size of the feed became finer, the grinding effect of hexagons became more apparent. At the same time, the qualified particles content in the ground product was higher when using hexagons than when using cylpebs. The relationship between the specific surface area and energy consumption during grinding was consistent with the regular pattern of grinding fineness and energy consumption. In addition, the bulk density of minerals decreases with an increase in grinding energy. The same conclusion was obtained when −0.425 mm tungsten ore was used as a sample for validation. The flotation experiment result has carried out that hexagons as grinding media have a better flotation indicator than cylpebs in the same grinding fineness. It is demonstrated that although the grinding capacity of hexagons is inferior to that of cylpebs, less overgrinding occurs when using hexagons than when using cylpebs. For tungsten ore grinding, hexagons act as a finer grinding media than cylpebs. Full article

(This article belongs to the Special Issue Selected Papers from “The 2nd International Conference of Young Scholars in Mineral Processing”)

► Show Figures

Graphical abstract

21 pages, 9625 KiB

Open AccessFeature PaperArticle

Trace Metal Distribution in Sulfide Minerals from Ultramafic-Hosted Hydrothermal Systems: Examples from the Kairei Vent Field, Central Indian Ridge

by Yejian Wang, Xiqiu Han, Sven Petersen, Matthias Frische, Zhongyan Qiu, Yiyang Cai and Peng Zhou

Minerals 2018, 8(11), 526; https://doi.org/10.3390/min8110526 - 11 Nov 2018

Cited by 29 | Viewed by 6086

Abstract

The ultramafic-hosted Kairei vent field is located at 25°19′ S, 70°02′ E, towards the Northern end of segment 1 of the Central Indian Ridge (CIR-S1) at a water depth of ~2450 m. This study aims to investigate the distribution of trace elements among [...] Read more.

The ultramafic-hosted Kairei vent field is located at 25°19′ S, 70°02′ E, towards the Northern end of segment 1 of the Central Indian Ridge (CIR-S1) at a water depth of ~2450 m. This study aims to investigate the distribution of trace elements among sulfide minerals of differing textures and to examine the possible factors controlling the trace element distribution in those minerals using LA-ICP-MS spot and line scan analyses. Our results show that there are distinct systematic differences in trace element distributions throughout the different minerals, as follows: (1) pyrite is divided into three types at Kairei, including early-stage euhedral pyrite (py-I), sub-euhedral pyrite (py-II), and colloform pyrite (py-III). Pyrite is generally enriched with Mo, Au, As, Tl, Mn, and U. Pyrite-I has high contents of Se, Te, Bi, and Ni when compared to the other types; py-II is enriched in Au relative to py-I and py-III, but poor in Ni; py-III is enriched in Mo, Pb, and U but is poor in Se, Te, Bi, and Au relative to py-I and py-II. Variations in the concentrations of Se, Te, and Bi in pyrite are most likely governed by the strong temperature gradient. There is generally a lower concentration of nickel than Co in pyrite, indicating that our samples precipitated at high temperatures, whereas the extreme Co enrichment is likely from a magmatic heat source combined with an influence of serpentinization reactions. (2) Chalcopyrite is characterized by high concentrations of Co, Se, and Te. The abundance of Se and Te in chalcopyrite over the other minerals is interpreted to have been caused by the high solubilities of Se and Te in the chalcopyrite lattice at high temperatures. The concentrations of Sb, As, and Au are relatively low in chalcopyrite from the Kairei vent field. (3) Sphalerite from Zn-rich chimneys is characterized by high concentrations of Sn, Co, Ga, Ge, Ag, Pb, Sb, As, and Cd, but is depleted in Se, Te, Bi, Mo, Au, Ni, Tl, Mn, Ba, V, and U in comparison with the other minerals. The high concentrations of Cd and Co are likely caused by the substitution of Cd²⁺ and Co²⁺ for Zn²⁺ in sphalerite. A high concentration of Pb accompanied by a high Ag concentration in sphalerite indicates that Ag occurs as Pb–Ag sulfosalts. Gold is generally low in sphalerite and strongly correlates with Pb, suggesting its presence in microinclusions of galena. The strong correlation of As with Ge in sphalerite from Kairei suggests that they might precipitate at medium temperatures and under moderately reduced conditions. (4) Bornite–digenite has very low concentrations of most trace elements, except for Co, Se, and Bi. Serpentinization in ultramafic-hosted hydrothermal systems might play an important role in Au enrichment in pyrite with low As contents. Compared to felsic-hosted seafloor massive sulfide deposits, sulfide minerals from ultramafic-hosted deposits show higher concentrations of Se and Te, but lower As, Sb, and Au concentrations, the latter often attributed to the contribution of magmatic volatiles. As with typical ultramafic-hosted seafloor massive sulfide deposits, Se enrichment in chalcopyrite from Kairei indicates that the primary factor that controls the Se enrichment is temperature-controlled mobility in vent fluids. Full article

(This article belongs to the Special Issue Deep-Sea Minerals and Gas Hydrates)

► Show Figures

Figure 1

18 pages, 9161 KiB

Open AccessEditor’s ChoiceArticle

Petrology of Chromitites in the Higashi-Akaishi Ultrahigh-Pressure (UHP) Peridotite Complex, Japan: Toward Understanding of General Features of the UHP Chromitites

by Makoto Miura, Shoji Arai, Tomoyuki Mizukami, Vladimir R. Shmelev and Satoko Ishimaru

Minerals 2018, 8(11), 525; https://doi.org/10.3390/min8110525 - 11 Nov 2018

Cited by 5 | Viewed by 4813

Abstract

Ultrahigh-pressure (UHP) chromitites containing UHP minerals such as coesite and diamond have been reported from some ophiolites in Tibet and the Polar Urals. Their nature, i.e., origin, P-T path and abundance, however, are still controversial and left unclear. Here we describe chromitites in [...] Read more.

Ultrahigh-pressure (UHP) chromitites containing UHP minerals such as coesite and diamond have been reported from some ophiolites in Tibet and the Polar Urals. Their nature, i.e., origin, P-T path and abundance, however, are still controversial and left unclear. Here we describe chromitites in the Higashi-akaishi (HA) ultramafic complex in the Cretaceous Sanbagawa metamorphic belt, Japan, which experienced UHP condition (up to 3.8 GPa) at the peak metamorphism via subduction, in order to understand the nature of UHP chromitites. The HA peridotites typically contain garnets and are associated with eclogites, and their associated chromitites are expected to have experienced the UHP metamorphism. The Higashi-akaishi (HA) chromitites show banded to massive structures and are concordant to foliation of the surrounding peridotite. Chromian spinels in the chromitite and surrounding peridotites were sometimes fractured by deformation, and contain various inclusions, i.e., blade- and needle-like diopside lamellae, and minute inclusions of pyroxenes, olivine, and pargasite. The peculiar UHP minerals, such as coesite and diamond, have not been found under the microscope and the Raman spectrometer. Spinels in the HA chromitites show high Cr#s (0.7 to 0.85), and low Ti contents (<0.1 wt %), suggesting a genetic linkage to an arc magma. The HA chromitites share the basic petrographic and chemical features (i.e., diopside lamellae and arc-related spinel chemistry) with the UHP chromitites from Tibet and the Polar Urals. This suggests that some of the characteristics of the UHP chromitite can be obtained by compression, possibly via deep subduction, of low-P chromitite. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Mineralogy of the Mantle as Tools to Read Messages from the Earth’s Interior)

► Show Figures

Figure 1

19 pages, 9738 KiB

Open AccessArticle

Microwave Treatment of Ultramafic Nickel Ores: Heating Behavior, Mineralogy, and Comminution Effects

by Erin R. Bobicki, Qingxia Liu and Zhenghe Xu

Minerals 2018, 8(11), 524; https://doi.org/10.3390/min8110524 - 11 Nov 2018

Cited by 29 | Viewed by 6919

Abstract

Ultramafic nickel ores are difficult to process because they contain serpentine, an anisotropic mineral with a nonspherical morphology and multiple pH-dependent surface charges. Dehydroxylation of serpentine in ultramafic nickel ores by microwave treatment is proposed to improve the processability of these ores. Upon [...] Read more.

Ultramafic nickel ores are difficult to process because they contain serpentine, an anisotropic mineral with a nonspherical morphology and multiple pH-dependent surface charges. Dehydroxylation of serpentine in ultramafic nickel ores by microwave treatment is proposed to improve the processability of these ores. Upon heating, serpentine is converted to olivine, an isotropic mineral that is benign in mineral processing circuits. The microwave heating of two ultramafic nickel ores is explored in this paper, as well as effects on mineralogy and grindability. The first ore was sourced from the Okanogan nickel deposit in Washington State, USA, while the second ore was obtained from the Vale-owned Pipe deposit located in the Thomson Nickel Belt in Manitoba, Canada. The ultramafic nickel ores were found to heat well upon exposure to microwave radiation and the heating behaviors were a function of the imaginary permittivities. The temperatures achieved during microwave treatment were sufficient to dehydroxylate serpentine, and the serpentine content in ultramafic nickel ores was reduced by 63–84%. The grindability of ore with consistent texture (OK ore) improved dramatically with microwave treatment, whereas the grindability of ore with inconsistent texture (Pipe ore) was found to decrease. Pentlandite liberation and specific surface area improved for both ores with microwave treatment. Ultimately, microwave pretreatment did not decrease the energy required for grinding under the conditions studied. However, energy savings may be realized when overall process improvements are considered (e.g., grinding, rheology, flotation, material handling, dewatering and tailings treatment). Full article

(This article belongs to the Special Issue Towards Sustainability in Extractive Metallurgy)

► Show Figures

Graphical abstract

16 pages, 5229 KiB

Open AccessArticle

Thermal Pre-Treatment of Polymetallic Nodules to Create Metal (Ni, Cu, Co)-Rich Individual Particles for Further Processing

by Anna V. Wegorzewski, Martin Köpcke, Thomas Kuhn, Maria A. Sitnikova and Hermann Wotruba

Minerals 2018, 8(11), 523; https://doi.org/10.3390/min8110523 - 11 Nov 2018

Cited by 21 | Viewed by 6084

Abstract

Polymetallic nodules are a potential source of industrially demanded metals such as Ni, Co, Cu, and Mo (up to 3 wt %). Even if there is no deep-sea mining of manganese nodules today, a forecasted gap between metal demand and supply as well [...] Read more.

Polymetallic nodules are a potential source of industrially demanded metals such as Ni, Co, Cu, and Mo (up to 3 wt %). Even if there is no deep-sea mining of manganese nodules today, a forecasted gap between metal demand and supply as well as continuously high metal prices may make seabed mining economically viable in the future. Up to now, a well-established industrial-scale extraction method for manganese nodules has been missing. Therefore, the aim of this study is to explore how economically interesting metals can be extracted from the nodules in a cost- and energy-efficient way. Polymetallic nodules have a heterogeneous chemical and structural composition without individual metal-rich particles. The economically interesting metals are distributed between different mineral phases (Mn-Fe-(oxy)hydroxides) as well as different growth structures that are intergrown with each other on a nm‒µm scale. Because of that a typical ore processing with the beneficiation of valuable particles is not feasible. The process presented here starts with a pyro-metallurgical pre-treatment of the polymetallic nodules, with the aim of creating artificial metal-rich (Ni, Cu, Co, Mo) particles with enrichment factors up to 10 compared to the original average metal contents. Afterwards, these particles should be beneficiated by conventional mineral processing steps to create a concentrate while reducing the mass stream in the process. The resulting metal particles can be further treated in conventional hydrometallurgical and/or pyro-metallurgical processes. Full article

(This article belongs to the Special Issue Marine Minerals of the Deep Sea: Mineralogy, Crystallography and Their Use for Tailored Processing and Metal Extraction)

► Show Figures

Figure 1

19 pages, 5122 KiB

Open AccessArticle

Graphite and Diamond Formation in the Carbide–Oxide–Carbonate Interactions (Experimental Modeling under Mantle P,T-Conditions)

by Yuliya Bataleva, Yuri Palyanov, Yuri Borzdov, Ivan Novoselov and Oleg Bayukov

Minerals 2018, 8(11), 522; https://doi.org/10.3390/min8110522 - 11 Nov 2018

Cited by 5 | Viewed by 3706

Abstract

Experimental modeling of the formation of graphite and diamond as a result of carbide–fluid interactions was performed in the Fe₃C–SiO₂–Al₂O₃–(Mg,Ca)CO₃ systems at 6.3 and 7.5 GPa and 1100–1650 °C. In the experiments with ƒO [...] Read more.

Experimental modeling of the formation of graphite and diamond as a result of carbide–fluid interactions was performed in the Fe₃C–SiO₂–Al₂O₃–(Mg,Ca)CO₃ systems at 6.3 and 7.5 GPa and 1100–1650 °C. In the experiments with ƒO₂-gradient (7.5 GPa, 1250–1350 °C), graphite + magnesiowüstite + garnet ± cohenite assemblage was formed. Graphite was produced through the redox interactions of carbide with carbonate or CO₂ (reducing conditions), and redox reactions of magnesiowüstite and CO₂ (oxidizing conditions). At 1450–1650 °C, crystallization of graphite, garnet, magnesiowüstite and ferrospinel, as well as generation of Fe^2+,3+-rich carbonate–silicate melt occurred. This melt, saturated with carbon, acted as a medium of graphite crystallization and diamond growth on seeds. In the experiments without ƒO₂-gradient (6.3 GPa), decarbonation reactions with the formation of CO₂-fluid and Fe,Mg,Ca-silicates, as well as C⁰-producing redox reactions of CO₂-fluid with cohenite were simultaneously realized. As a result, graphite (± diamond growth) was formed in assemblage with Fe²⁺,Fe³⁺,Mg-silicates and magnetite (1100–1200 °C), or with Fe³⁺-rich garnet and orthopyroxene (1300–1500 °C). It has been established that a potential mechanism for the crystallization of graphite or diamond growth is the oxidation of cohenite by CO₂-fluid to FeO and Fe₃O₄, accompanied by the extraction of carbon from Fe₃C and the corresponding reduction of CO₂ to C⁰. Full article

(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)

► Show Figures

Figure 1

14 pages, 6402 KiB

Open AccessArticle

One-Step Synthesis of Hydroxysodalite Using Natural Bentonite at Moderate Temperatures

by Bo Liu, Hongjuan Sun, Tongjiang Peng and Qian He

Minerals 2018, 8(11), 521; https://doi.org/10.3390/min8110521 - 9 Nov 2018

Cited by 12 | Viewed by 4983

Abstract

Ca-bentonite was used as the feedstock material for the synthesis of hydroxysodalite due to its high Al, Si content, good chemical reactivity, and natural abundance. A one-step method is proposed here to fabricate hydroxysodalite in a water bath at moderate temperature. The effects [...] Read more.

Ca-bentonite was used as the feedstock material for the synthesis of hydroxysodalite due to its high Al, Si content, good chemical reactivity, and natural abundance. A one-step method is proposed here to fabricate hydroxysodalite in a water bath at moderate temperature. The effects of the Na/Si molar ratio, Si/Al molar ratio, reaction time, and reaction temperature on the synthesis of hydroxysodalite have been systematically investigated here. The crystallizing phases and morphology of the synthetic products were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results showed that the Na/Si molar ratio and reaction temperature both played important roles in controlling the degree of crystallinity of the synthetic hydroxysodalite. The Si/Al molar ratio and reaction time both affect the purity of the synthetic hydroxysodalite. Optimum conditions for synthesizing hydroxysodalite using a one-step water-bath method at moderate temperature are as follows: a Na/Si molar ratio of 12, a Si/Al molar ratio of 1.0, a reaction temperature of 90 °C, and a reaction time of 12 h. Full article

(This article belongs to the Special Issue Nanomineralogy)

► Show Figures

Figure 1

22 pages, 5101 KiB

Open AccessReview

An Overview of Authigenic Magnesian Clays

by Manuel Pozo and José Pedro Calvo

Minerals 2018, 8(11), 520; https://doi.org/10.3390/min8110520 - 9 Nov 2018

Cited by 74 | Viewed by 10443

Abstract

Clay authigenesis mostly concerns: (a) the formation of clays by direct precipitation from solution, called “neoformation” and (b) development of clays by transformation of precursor minerals. Precipitation from solution implies that a new mineral structure crystallizes, so that a prior mineral structure is [...] Read more.

Clay authigenesis mostly concerns: (a) the formation of clays by direct precipitation from solution, called “neoformation” and (b) development of clays by transformation of precursor minerals. Precipitation from solution implies that a new mineral structure crystallizes, so that a prior mineral structure is not inherited. Transformation of precursor detrital minerals, a process also termed “neoformation by addition”, can be conducted whether throughout precipitation on pre-existing natural surfaces or transformation and reaction on pre-existing surfaces. Both processes have been recognized as effective mechanisms in the formation of Mg-clays, which mostly include 2:1 clay minerals, such as talc-kerolite and Mg-smectites, as well as fibrous clays (sepiolite, palygorskite). Authigenic Mg-clay minerals occur in both modern and ancient marine and non-marine depositional environments, although formation of these clays in hydrothermal continental and seafloor settings must be also outlined. Most favourable conditions for the formation of Mg-clays on earth surface are found in evaporitic depositional environments, especially where parent rocks are enriched in ferromagnesian minerals. In these settings, Mg-clays are important constituent of weathering profiles and soils and can form thick deposits of significant economic interest. Based on this review of authigenic clay deposits, we propose three geochemical pathways, mainly related to continental environments, for the origin of authigenic Mg-clays: formation of Al-bearing Mg-clays (pathway 1), formation of Al-free Mg clays (pathway 2) and formation of sepiolite from other Mg-clay minerals (pathway 3). Full article

(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)

► Show Figures

Figure 1

12 pages, 1834 KiB

Open AccessTechnical Note

Critical Metal Particles in Copper Sulfides from the Supergiant Río Blanco Porphyry Cu–Mo Deposit, Chile

by Jorge Crespo, Martin Reich, Fernando Barra, Juan José Verdugo and Claudio Martínez

Minerals 2018, 8(11), 519; https://doi.org/10.3390/min8110519 - 9 Nov 2018

Cited by 26 | Viewed by 5924

Abstract

Porphyry copper–molybdenum deposits (PCDs) are the world’s most important source of copper, molybdenum and rhenium. Previous studies have reported that some PCDs can have sub-economic to economic grades of critical metals, i.e., those elements that are both essential for modern societies and subject [...] Read more.

Porphyry copper–molybdenum deposits (PCDs) are the world’s most important source of copper, molybdenum and rhenium. Previous studies have reported that some PCDs can have sub-economic to economic grades of critical metals, i.e., those elements that are both essential for modern societies and subject to the risk of supply restriction (e.g., platinum group elements (PGE), rare earth elements (REE), In, Co, Te, Ge, Ga, among others). Even though some studies have reported measured concentrations of Pd and Pt in PCDs, their occurrence and mineralogical forms remain poorly constrained. Furthermore, these reconnaissance studies have focused predominantly on porphyry Cu–Au deposits, but very limited information is available for porphyry Cu–Mo systems. In this contribution, we report the occurrence of critical metal (Pd, Pt, Au, Ag, and Te) inclusions in copper sulfides from one of the largest PCDs in the world, the supergiant Río Blanco-Los Bronces deposit in central Chile. Field emission scanning electron microscope (FESEM) observations of chalcopyrite and bornite from the potassic alteration zone reveal the presence of micro- to nano-sized particles (<1–10 μm) containing noble metals, most notably Pd, Au, and Ag. The mineralogical data show that these inclusions are mostly tellurides, such as merenskyite ((Pd, Pt) (Bi, Te)₂), Pd-rich hessite (Ag₂Te), sylvanite ((Ag,Au)Te₂) and petzite (Ag₃AuTe₂). The data point to Pd (and probably Pt) partitioning in copper sulfides during the high-temperature potassic alteration stage, opening new avenues of research aimed at investigating not only the mobility of PGE during mineralization and partitioning into sulfides, but also at exploring the occurrence of critical metals in porphyry Cu–Mo deposits. Full article

(This article belongs to the Special Issue Minerals Down to the Nanoscale: A Glimpse at Ore-Forming Processes)

► Show Figures

Figure 1

22 pages, 9380 KiB

Open AccessArticle

New Perspectives for UAV-Based Modelling the Roman Gold Mining Infrastructure in NW Spain

by Javier Fernández-Lozano, Alberto González-Díez, Gabriel Gutiérrez-Alonso, Rosa M. Carrasco, Javier Pedraza, Jacinta García-Talegón, Gaspar Alonso-Gavilán, Juan Remondo, Jaime Bonachea and Mario Morellón

Minerals 2018, 8(11), 518; https://doi.org/10.3390/min8110518 - 9 Nov 2018

Cited by 22 | Viewed by 10755

Abstract

This contribution discusses the potential of UAV-assisted (unmanned aerial vehicles) photogrammetry for the study and preservation of mining heritage sites using the example of Roman gold mining infrastructure in northwestern Spain. The study area represents the largest gold area in Roman times and [...] Read more.

This contribution discusses the potential of UAV-assisted (unmanned aerial vehicles) photogrammetry for the study and preservation of mining heritage sites using the example of Roman gold mining infrastructure in northwestern Spain. The study area represents the largest gold area in Roman times and comprises 7 mining elements of interest that characterize the most representative examples of such ancient works. UAV technology provides a non-invasive procedure valuable for the acquisition of digital information in remote, difficult to access areas or under the risk of destruction. The proposed approach is a cost-effective, robust and rapid method for image processing in remote areas were no traditional surveying technologies are available. It is based on a combination of data provided by aerial orthoimage and LiDAR (Light Detection and Ranging) to improve the accuracy of UAV derived data. The results provide high-resolution orthomosaic, DEMs and 3D textured models that aim for the documentation of ancient mining scenarios, providing high-resolution digital information that improves the identification, description and interpretation of mining elements such as the hydraulic infrastructure, the presence of open-cast mines which exemplifies the different exploitation methods, and settlements. However, beyond the scientific and technical information provided by the data, the 3D documentation of ancient mining scenarios is a powerful tool for an effective and wider public diffusion ensuring the visualization, preservation and awareness over the importance and conservation of world mining heritage sites. Full article

(This article belongs to the Special Issue Unmanned Aerial Systems (UAS) in Geology and Environmental Modelling)

► Show Figures

Graphical abstract

12 pages, 1011 KiB

Open AccessArticle

Separation of Copper from Electric Cable Waste Based on Mineral Processing Methods: A Case Study

by Fernando Pita and Ana Castilho

Minerals 2018, 8(11), 517; https://doi.org/10.3390/min8110517 - 8 Nov 2018

Cited by 21 | Viewed by 5083

Abstract

Recycling of electrical cable waste requires a separation between the metal and the insulating material. The objective of this work was to separate the copper from the plastic in electrical cable waste previously ground below 2 mm, using jigging, shaking table and froth [...] Read more.

Recycling of electrical cable waste requires a separation between the metal and the insulating material. The objective of this work was to separate the copper from the plastic in electrical cable waste previously ground below 2 mm, using jigging, shaking table and froth flotation techniques. The effect of particle size was also analysed. Jigging and shaking table proved to be effective in the separation of copper from plastics. The result was a copper concentrate with a copper grade of about 97% by both methods and a copper recovery of about 97%. Jigging separation had similar separation efficiencies in the seven-sized fractions, but in shaking table, the separation efficiency improved with an increase in particles size. The separation achieved by froth flotation had lower efficiencies (85%), because plastics are naturally hydrophobic and copper presents some hydrophobic behaviour. In this technique, the addition of depressant agents was mandatory for the depression of copper, even at low concentrations. The best results were obtained with concentrations of 10⁻¹ mg/L of sodium sulfide (407410 Sigma-Aldrich, Sigma-Aldrich Corporation, St. Louis, MO, USA) and meso-2,3-Dimercaptosuccinic acid (D7881 Sigma-Aldrich). Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

► Show Figures

Figure 1

29 pages, 69075 KiB

Open AccessArticle

Ore Genesis and Geodynamic Setting of Laochang Ag-Pb-Zn-Cu Deposit, Southern Sanjiang Tethys Metallogenic Belt, China: Constraints from Whole Rock Geochemistry, Trace Elements in Sphalerite, Zircon U-Pb Dating and Pb Isotopes

by Chen Wei, Lin Ye, Zhilong Huang, Wei Gao, Yusi Hu, Zhenli Li and Jiawei Zhang

Minerals 2018, 8(11), 516; https://doi.org/10.3390/min8110516 - 8 Nov 2018

Cited by 23 | Viewed by 6936

Abstract

The Laochang Ag-Pb-Zn-Cu deposit, located in the southern margin of the Sanjiang Tethys Metallogenic Belt (STMB), is the typical Ag-Pb-Zn-Cu deposit in this region. Its orebodies are hosted in the Carboniferous Yiliu Formation volcanic-sedimentary cycle and occur as stratiform, stratoid and lenticular. Whether [...] Read more.

The Laochang Ag-Pb-Zn-Cu deposit, located in the southern margin of the Sanjiang Tethys Metallogenic Belt (STMB), is the typical Ag-Pb-Zn-Cu deposit in this region. Its orebodies are hosted in the Carboniferous Yiliu Formation volcanic-sedimentary cycle and occur as stratiform, stratoid and lenticular. Whether or not the stratabound ore belong to the volcanogenic massive sulfide (VMS) deposit remains unclear and controversial. In this paper, the whole rock geochemistry, trace elements in sphalerite, U-Pb zircon chronology and Pb isotopes were investigated, aiming to provide significant insights into the genesis and geodynamic setting of the Laochang deposit. Lead isotope ratios of pyrite and sphalerite from the stratabound ore are 18.341 to 18.915 for ²⁰⁶Pb/²⁰⁴Pb; 15.376 to 15.770 for ²⁰⁷Pb/²⁰⁴Pb; and 38.159 to 39.200 for ²⁰⁸Pb/²⁰⁴Pb—which display a steep linear trend on Pb-Pb diagrams. This indicates a binary mixing of lead components derived from leaching between the host volcanic rock and mantle reservoir. Sphalerite from stratabound ores is relatively enriched in Fe, Mn, In, Sn, and Ga—similar to typical VMS deposits. Moreover, the Carboniferous volcanic rock hosting the stratabound Ag-Pb-Zn-Cu ores has a zircon U-Pb age of 312 ± 4 Ma; together with previous geochronological and geological evidences, thus, we consider that the stratabound mineralization occur in the Late Paleozoic (~323–308 Ma). Collectively, these geologic, geochemical, and isotopic data confirm that the stratabound ores should be assigned to Carboniferous VMS mineralization. In addition, volcanic rocks hosting the stratabound ore exhibit elevated high field strength elements (HFSEs, Nb, Ta, Zr and Hf) abundance, slight enrichment of light rare earth element (LREE), and depletion of Ba and Sr with obvious Nb-Ta anomalies. Such characteristics suggest that their magma is similar to typical oceanic island basalt. In addition, the oceanic island basalt (OIB)-like volcanic rocks were formed at Late Paleozoic, which could be approximately synchronous with the VMS mineralization at Laochang. Thus, it is suggested that the Laochang VMS mineralization was generated in the oceanic island setting prior to the initial subduction of the Changning-Menglian Paleo-Tethys Ocean. Full article

(This article belongs to the Special Issue Massive Sulfide Deposits all around the World)

► Show Figures

Figure 1

16 pages, 18873 KiB

Open AccessArticle

Mantle Evolution from Ocean to Arc: The Record in Spinel Peridotite Xenoliths in Mt. Pinatubo, Philippines

by Betchaida D. Payot, Shoji Arai, Masako Yoshikawa, Akihiro Tamura, Mitsuru Okuno and Danikko John V. Rivera

Minerals 2018, 8(11), 515; https://doi.org/10.3390/min8110515 - 8 Nov 2018

Cited by 13 | Viewed by 9075

Abstract

A suite of peridotite xenoliths were collected from lahar flow deposits located close to the summit of Mt. Pinatubo. Spinel harzburgite is the most dominant lithology among dunites, pyroxenites and websterites. A rare spinel lherzolite xenolith (P12-7) is also present in this suite. [...] Read more.

A suite of peridotite xenoliths were collected from lahar flow deposits located close to the summit of Mt. Pinatubo. Spinel harzburgite is the most dominant lithology among dunites, pyroxenites and websterites. A rare spinel lherzolite xenolith (P12-7) is also present in this suite. The spinel lherzolite has well-preserved protogranular texture with very minimal presence of secondary amphibole, low Cr# in the chromian spinel, and depleted and hump shaped patterns of chondrite-normalized rare earth element (REE) patterns for the clinopyroxenes. In contrast, the spinel harzburgites contain abundant secondary amphiboles and orthopyroxenes, higher Cr# in the spinel, and slightly elevated patterns for the chondrite-normalized REE patterns for the amphiboles. The spinel lherzolite also exhibits higher olivine Fo content for a given spinel Cr# compared to the spinel harzburgites. The spinel lherzolite is interpreted as a typical residue from partial melting of abyssal peridotites whereas the spinel harzburgites may have formed via partial melting with subsequent modification during the influx of fluids in the mantle wedge. Our results suggest that fragments of MOR-derived lithosphere exist in the mantle wedge beneath the Philippine island arc. This work provides evidence for the conversion of abyssal to arc peridotites in the mantle wedge. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Mineralogy of the Mantle as Tools to Read Messages from the Earth’s Interior)

► Show Figures

Figure 1

22 pages, 9843 KiB

Open AccessArticle

Copper-Containing Magnesioferrite in Vesicular Trachyandesite in a Lava Tube from the 2012–2013 Eruption of the Tolbachik Volcano, Kamchatka, Russia

by Victor V. Sharygin, Vadim S. Kamenetsky, Liudmila M. Zhitova, Alexander B. Belousov and Adam Abersteiner

Minerals 2018, 8(11), 514; https://doi.org/10.3390/min8110514 - 8 Nov 2018

Cited by 6 | Viewed by 5539

Abstract

Cu-rich magnesioferrite was found in vesicular basaltic trachyandesite in one of lava tubes (Duplex) that formed during the 2012–2013 eruption of the Tolbachik volcano, Kamchatka. This mineral is commonly associated with hematite, tenorite, halite, sylvite, and Ca-rich silicates (mainly, esseneite and Na-rich melilite) [...] Read more.

Cu-rich magnesioferrite was found in vesicular basaltic trachyandesite in one of lava tubes (Duplex) that formed during the 2012–2013 eruption of the Tolbachik volcano, Kamchatka. This mineral is commonly associated with hematite, tenorite, halite, sylvite, and Ca-rich silicates (mainly, esseneite and Na-rich melilite) in high-temperature (800–1000 °C) reactionary zones (up to 100 µm) covering vesicular rocks and lava stalactites in the Duplex tube. The mineral relationships of this assemblage indicate the following crystallization sequence: Ca-rich silicates + hematite → Cu-rich magnesioferrite → tenorite → chlorides. This formed due to the reaction of hot gases containing Cu, alkalis, and Cl with solidified lava rock. The composition of magnesioferrite varies strongly in CuO (5.8–17.3 wt %; cuprospinel end-member—15–47 mol %), whereas the contents of other oxides are minor, indicating the main isomorphic substitution is Mg²⁺ ↔ Cu²⁺. Compositions with maximal CuO content nominally belong to Mg-rich cuprospinel: (Cu_0.48Mg_0.41Mn_0.09Zn_0.02Ca_0.02) (Fe³⁺_1.94Al_0.03Ti_0.02)O₄. Increasing CuO content of the Duplex Cu-rich magnesioferrite is reflected in Raman spectra by moderate right shifting bands at ≈700–710 and 200–210 cm⁻¹ and the appearance of an additional band at 596 cm⁻¹. This supports the main isomorphic scheme and may indicate a degree of inversion in the spinel structure. Full article

(This article belongs to the Special Issue Spinel Group Minerals)

► Show Figures

Figure 1

19 pages, 4232 KiB

Open AccessArticle

Understanding Heterogeneity of a Slag-Derived Weathered Material: The Role of Automated SEM-EDS Analyses

by Anna Pietranik, Jakub Kierczak, Rafał Tyszka and Bernhard Schulz

Minerals 2018, 8(11), 513; https://doi.org/10.3390/min8110513 - 8 Nov 2018

Cited by 18 | Viewed by 3986

Abstract

Slag heaps over years may evolve into complexly weathered zones, which are a challenging material for analyses as they contain phases from numerous sources and at different stages of weathering. However, the weathered zones are important parts of slag heaps, because they contain [...] Read more.

Slag heaps over years may evolve into complexly weathered zones, which are a challenging material for analyses as they contain phases from numerous sources and at different stages of weathering. However, the weathered zones are important parts of slag heaps, because they contain both primary and secondary phases enriched in metal(oid)s that may become soluble under specific conditions. The weathering reactions related to metal release or precipitation may be recorded in a heavy mineral fraction as the fraction contains predominately minerals with elevated toxic elements concentrations. Therefore, an automated SEM analysis on a polished section of included heavy mineral particles was applied in this paper for a rapid recognition of phases in a complex setting and their classification into detrital, primary and secondary phases. The approach was applied to a slag heap in Świętochłowice (Upper Silesia, Poland) and it consisted of analyzing magnetic and non-magnetic heavy mineral fractions from three distinct horizons noted A, B and C. Materials had been previously interpreted as being sourced from the heap itself (lowermost horizon C) and from artificially added materials used later for superficial site remediation (upper horizons A and B). Instead, automated SEM analysis demonstrated that horizon C is derived from the slag heap weathering, horizon B is derived predominately from the artificially added materials, whereas horizon A is a mixture of the B and C horizons. Additionally, when slag particles in horizons A and C are compared, the lowermost horizon C contains more slag-derived secondary phases, whereas horizon A contains more primary slag phases. Therefore, horizon A remains the most prone to releasing toxic elements because, considering its position as the uppermost horizon, it can be submitted to climatic solicitation (fast water circulation). Full article

(This article belongs to the Special Issue Metallurgical Slags)

► Show Figures

Figure 1

22 pages, 1861 KiB

Open AccessArticle

He–Ar–S Isotopic Compositions of Polymetallic Sulphides from Hydrothermal Vent Fields along the Ultraslow-Spreading Southwest Indian Ridge and Their Geological Implications

by Yan Wang, Zhongwei Wu, Xiaoming Sun, Xiguang Deng, Yao Guan, Li Xu, Yi Huang and Kaijun Cao

Minerals 2018, 8(11), 512; https://doi.org/10.3390/min8110512 - 7 Nov 2018

Cited by 4 | Viewed by 5402

Abstract

Noble gases have become a powerful tool to constrain the origin and evolution of ore-forming fluids in seafloor hydrothermal systems. The aim of this study was to apply these tracers to understand the genesis of newly discovered polymetallic sulphide deposits along the ultraslow-spreading [...] Read more.

Noble gases have become a powerful tool to constrain the origin and evolution of ore-forming fluids in seafloor hydrothermal systems. The aim of this study was to apply these tracers to understand the genesis of newly discovered polymetallic sulphide deposits along the ultraslow-spreading Southwest Indian Ridge (SWIR). The helium, argon, and sulphur isotope compositions of metal sulphide minerals were measured for a number of active/inactive vent fields in the Indian Ocean. The helium concentrations and isotopic ratios in these ore samples are variable (⁴He: 0.09–2.42 × 10⁻⁸ cm³STP∙g⁻¹; ³He: 0.06–3.28 × 10⁻¹³ cm³STP∙g⁻¹; ³He/⁴He: 1.12–9.67 R_a) and generally greater than the modern atmosphere, but significantly lower than those in massive sulphides from the fast-spreading East Pacific Rise (EPR), especially for three Cu–Fe-rich samples from the ultramafic-hosted Tianzuo and Kairei vent fields. On the contrary, most of the SWIR sulphide deposits have somewhat higher ⁴⁰Ar/³⁶Ar ratios of trapped fluids (ranging from 290.6 to 303.4) when compared to the EPR ore samples. Moreover, the majority of sulphide minerals from the Indian Ocean have much higher δ³⁴S values (3.0‰–9.8‰, ~5.9 on average, n = 49) than other basaltic-hosted active hydrothermal systems on the EPR. Overall, these He–Ar–S results are well within the range of seafloor massive sulphide deposits at global sediment-starved mid-ocean ridges (MORs), lying between those of air-saturated water (ASW) and mid-ocean ridge basalt (MORB) end members. Therefore, our study suggests that the helium was derived mainly from the MORB mantle by degassing during the high-temperature stage of hydrothermal activity, as well as from a mixture of vent fluids with variable amounts of ambient seawater during either earlier or late-stage low-temperature hydrothermal episodes, whereas the argon in ore-forming fluids trapped within sulphide minerals was predominantly derived from deep-sea water. Additionally, relatively high δ³⁴S values exhibit a great estimated proportion (up to nearly 40%) of seawater-derived components. In summary, sub-seafloor extensive fluid circulation, pervasive low-temperature alteration, shallow seawater entrainment, and mixing processes, may make a larger contribution to the SWIR hydrothermal ore-forming systems, compared to fast-spreading centres. Full article

(This article belongs to the Special Issue Deep-Sea Minerals and Gas Hydrates)

► Show Figures

Figure 1

16 pages, 3890 KiB

Open AccessArticle

Paddlewheelite, a New Uranyl Carbonate from the Jáchymov District, Bohemia, Czech Republic

by Travis A. Olds, Jakub Plášil, Anthony R. Kampf, Fabrice Dal Bo and Peter C. Burns

Minerals 2018, 8(11), 511; https://doi.org/10.3390/min8110511 - 7 Nov 2018

Cited by 13 | Viewed by 4720

Abstract

Paddlewheelite, MgCa₅Cu₂[(UO₂)(CO₃)₃]₄·33H₂O, is a new uranyl carbonate mineral found underground in the Svornost mine, Jáchymov District, Bohemia, Czech Republic, where it occurs as a secondary oxidation product of uraninite. [...] Read more.

Paddlewheelite, MgCa₅Cu₂[(UO₂)(CO₃)₃]₄·33H₂O, is a new uranyl carbonate mineral found underground in the Svornost mine, Jáchymov District, Bohemia, Czech Republic, where it occurs as a secondary oxidation product of uraninite. The conditions leading to its crystallization are complex, likely requiring concomitant dissolution of uraninite, calcite, dolomite, chalcopyrite, and andersonite. Paddlewheelite is named after its distinctive structure, which consists of paddle-wheel clusters of uranyl tricarbonate units bound by square pyramidal copper “axles” and a cubic calcium cation “gearbox.” Paddle wheels share edges with calcium polyhedra to form open sheets that are held together solely by hydrogen bonding interactions. The new mineral is monoclinic, Pc, a = 22.052(4), b = 17.118(3), c = 19.354(3) Å, β = 90.474(2)°, V = 7306(2) Å³ and Z = 4. Paddlewheelite is the second-most structurally complex uranyl carbonate mineral known after ewingite and its structure may provide insights into the insufficiently described mineral voglite, as well as Cu–U–CO₃ equilibrium in general. Full article

(This article belongs to the Special Issue Actinide Mineralogy and Crystallography)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Minerals, Volume 8, Issue 11 (November 2018) – 67 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI