Minerals

20 pages, 7915 KiB

Open AccessArticle

Coexisting High-Al and High-Cr Chromitites in the Dingqing Ophiolite (SE Tibet): Inferences to Compositional Heterogeneity in the Tethyan Upper Mantle

by Boyang Zhang, Basem Zoheir, Chenjie Zhang, Xiaoping Mu, Xiangzhen Xu, Tian Qiu and Fahui Xiong

Minerals 2023, 13(9), 1234; https://doi.org/10.3390/min13091234 - 21 Sep 2023

Cited by 1 | Viewed by 1303

Abstract

The Dingqing ophiolite represents a significant allochthonous ophiolite nappe in the eastern segment of the Bangong–Nujiang suture zone in southeastern Tibet. The microanalytical data of associated podiform chromitites classify them into two distinct varieties: high-Al and high-Cr. The coexistence of both high-Cr and [...] Read more.

The Dingqing ophiolite represents a significant allochthonous ophiolite nappe in the eastern segment of the Bangong–Nujiang suture zone in southeastern Tibet. The microanalytical data of associated podiform chromitites classify them into two distinct varieties: high-Al and high-Cr. The coexistence of both high-Cr and high-Al chromitites in the Dingqing ophiolite suggests a complex or multistage evolutionary history of the host rocks. New petrological and geochemical analyses are used herein to unravel the interrelationships between the chromitite ores and host rocks and assess the mechanism of formation. The Dingqing ophiolitic nappe is made up mainly of harzburgite, dunite, and less abundant pyroxenite and gabbro. Several small lens-shaped bodies of chromitite ore are mostly confined to the harzburgite rocks, with ore textures varying from massive to sparsely disseminated chromite. In addition to magnesiochromite, the orebodies contain minor amounts of olivine, amphibole, and serpentine. The textural relationships provide compelling evidence of plastic deformation and partial melting of the associated peridotites. Detailed examination of the Cr-spinel grains reveals a wide range of composition, spanning from high-Al (Cr# = 3.18–59.5) to high-Cr (Cr# 60.3–87.32). The abundances of the platinum-group element (PGE) in chromitites are significantly variable (93 to 274 ppb). Formation of the Dingqing peridotites most likely took place in a mid-ocean ridge (MOR) setting, and subsequent modifications by supra-subduction zone (SSZ) melts resulted in heterogenous or mixed geochemical characteristics of these rocks. Chemistry of the spinel–olivine–clinopyroxene assemblage demonstrates multiple stages of partial melting of the source mantle rocks, including an early phase of restricted partial melting (~20%–30%) and a later phase of extensive partial melting (>40%). The formation of the high-Al chromitite type was associated with the early phase (constrained melting), whereas extensive partial melting in the late stages likely led to the accumulation of high-Cr podiform chromitite bodies. Full article

(This article belongs to the Special Issue Mineralogical and Geochemical Characteristics of Chromitites)

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13 pages, 18457 KiB

Open AccessArticle

Types and Genesis of Siderite in the Coal-Bearing Beds of the Late Permian Xuanwei Formation in Eastern Yunnan, China

by Hailei Tang, Qing Zhao, Bo Liu, Shucheng Tan and Kaibo Shi

Minerals 2023, 13(9), 1233; https://doi.org/10.3390/min13091233 - 21 Sep 2023

Viewed by 1507

Abstract

The Late Permian strata of the Xuanwei Formation in the eastern Yunnan region exhibit extensive diverse morphological features within siderite deposits. These variations in siderite deposits suggest potential differences in their formation processes. In this study, fieldwork and comprehensive indoor studies revealed four [...] Read more.

The Late Permian strata of the Xuanwei Formation in the eastern Yunnan region exhibit extensive diverse morphological features within siderite deposits. These variations in siderite deposits suggest potential differences in their formation processes. In this study, fieldwork and comprehensive indoor studies revealed four distinct forms of siderite deposits: stratiform-laminated, lens-like nodule, sandstone cementation, and fracture filling. The stratiform-laminated siderite, varying in color from bluish-grey to dark grey, is composed of uniformly sized microcrystalline to fine-grained siderite along with detrital matter, displaying precise layering and banding structures that suggest direct deposition from cyclic iron-rich seawater under reducing conditions. Lens-like-nodule siderite, which appears grey-yellow, is composed of mud microcrystalline siderite, medium to coarse-grained pseudo-ooids, and glauconite. It shows conformable distribution characteristics resulting from the diagenetic differentiation of iron-rich sediments under reducing conditions during the diagenetic and early diagenetic periods. Siderite as sandstone cementation exhibits a yellow-brown color and consists of dispersed colloidal siderite and cemented siderite clumps that fill intergranular pores of detrital particles. It precipitated under reducing conditions within those intergranular pores. Siderite filling fractures typically appear as vein-like or network-like structures intersecting bedding at large angles. They exhibit grain structures with significant variations in size. These siderite deposits exhibit exceptional purity and result from siderite dissolution during sedimentary periods, followed by reprecipitation within regional extensional fractures during the diagenetic phase. The primary occurrence of siderite deposits in the study area is within coal-bearing strata, as revealed by the integration of sedimentary profiles and sedimentary facies analysis. The coal-bearing strata, influenced by the Emeishan large igneous province, underwent iron enrichment during and after volcanic eruptions while developing a reducing environment, which was facilitated by abundant vegetation. Consequently, geological processes led to siderite layers, lens-like siderite nodules, and siderite cementation. The Yanshan orogeny induced extensive high-angle fracture development in epigenetic coal-bearing strata, facilitating fluid circulation and the redistribution of soluble siderite. This geological activity resulted in the formation of vein-like structures composed of siderite. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Coal-Bearing Rocks, 2nd Edition)

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Regional tectonic and sedimentary zoning of the study area. (A) Simplified structural chart of tectonic zoning in southern China and the study area’s structural map (modified from [<a href="#B21-minerals-13-01233" class="html-bibr">21</a>]); (B) geological map of eastern Yunnan (redrawn from the 1:200,000 geological map of Yunnan Province, 1965); (C) comprehensive lithostratigraphic and chronostratigraphic chart of Permian rocks in southwestern China (modified from [<a href="#B22-minerals-13-01233" class="html-bibr">22</a>,<a href="#B23-minerals-13-01233" class="html-bibr">23</a>]); (D) Late Permian Xuanwei Formation sedimentary paleogeography and distribution of the Emeishan large igneous province in western Yunnan and eastern Guizhou (modified from [<a href="#B24-minerals-13-01233" class="html-bibr">24</a>,<a href="#B25-minerals-13-01233" class="html-bibr">25</a>]). Full article ">Figure 2
Microscopic characteristics of stratiform-banded siderite in the Hamazhai section of Qujing City. (A) The outcrop of stratiform-banded siderite in the coal-bearing rock series is observed at a macroscopic level, accompanied by a lithological column illustration on the left side; (B) the siderite, distributed in a banded pattern within the coal-bearing strata, exhibits a yellowish-brown coloration; (C) a magnified photograph of a specific area from (B) is provided; (D) the microcrystalline to fine-grained siderite contains bioclasts, such as foraminifera and algae, HM-8, ×5; (E) the microcrystalline to fine-grained siderite exhibits lamination and banded structures, HM-13, ×5; (F) an aggregation of micro-powdery siderite is observed, HM-15, ×5. Full article ">Figure 3
Macroscopic and microscopic features of lens-like and nodule siderite at the Geyi section are examined. (A) The coal-bearing rock series of siderite is macroscopically exposed, with the lithological column illustrated in the left-side sketch; (B) macroscopic photograph of lens-like siderite, displaying a fresh bluish-gray surface; (C) microscopic phenomena of lens-like siderite, coexisting with glauconite and apatite, HM-22, ×5; (D) macroscopic photograph of nodular siderite is presented; (E) microscopic phenomena of nodular siderite, consisting of microcrystalline siderite, SG-5, ×5; (F) photograph of large-grained siderite nodules is presented, SG-13; (G) microscopic phenomena of nodular siderite, exhibiting medium to coarse-grained siderite, ×5. Full article ">Figure 4
Macroscopic and microscopic characteristics of siderite as a cementing material in sandstone at the Huchang Town section. (A,B) Coal-bearing strata expose a layer of siderite—the accompanying left-hand sketch illustrates the lithological column; (C) macroscopic photograph of sandstone containing rhombohedral iron, SG-10; (D) microscopic characteristics of agglomerated colloform siderite, SG-8, ×5; (E) microscopic features of dispersed agglomerated siderite, SG-10, ×5. Full article ">Figure 5
The macroscopic and microscopic characteristics of siderite developed within tectonic fractures. (A) Siderite developed within fractures and joint surfaces; (B) photograph of mesh-like structured siderite; (C) Microscopic characteristics of grape-like siderite, SG-7, ×5; (D) microscopic characteristics of grape-like siderite coexisting with infiltrated sand, SG-14, ×5; (E) microscopic characteristics of grape-like siderite coexisting with laminated fine to medium-sized siderite, SG-15, ×5. Full article ">Figure 6
Comprehensive geochemical characterization map of siderite in the Late Permian Xuanwei Formation coal-bearing strata in Eastern Yunnan. (A) Siderite’s major-element binary diagram of MgO and CaO; (B) distribution map of transition elements’ V/Cr and V (V + Ni) ratios in siderite; (C) binary diagram of major elements Al2O3 and TiO2 in siderite; (D) Al2O3/TiO2-TiO2 diagram of major elements in siderite and comparisons with Emeishan igneous rock composition. Full article ">

19 pages, 10429 KiB

Open AccessArticle

Clinopyroxene Compositions of E-MORB-Type Gabbro from Bingdaban Ophiolites in Central Tianshan, NW China: Insights into the Evolution of the Magmatic System and Geodynamic Setting

by Yujia Song, Xijun Liu, Yao Xiao, Xiao Liu and Hao Tian

Minerals 2023, 13(9), 1232; https://doi.org/10.3390/min13091232 - 20 Sep 2023

Cited by 2 | Viewed by 1459

Abstract

Clinopyroxene, one of the primary rock-forming minerals in mafic rocks, is the major host of lithophile elements in the mantle lithosphere and plays a crucial role in understanding mantle evolution and rock petrogenesis. Taking the Bingdaban ophiolite as an example, this study employed [...] Read more.

Clinopyroxene, one of the primary rock-forming minerals in mafic rocks, is the major host of lithophile elements in the mantle lithosphere and plays a crucial role in understanding mantle evolution and rock petrogenesis. Taking the Bingdaban ophiolite as an example, this study employed electron probe microanalysis and in situ trace element analysis to investigate the geochemistry of clinopyroxene in gabbros to determine the magma series and evolution, constrain the physicochemical conditions of the magmatic processes and explore the petrogenesis and tectonic setting. Representative gabbro samples were subjected to zircon U–Pb isotopic analysis, yielding an age of 424.3 ± 5.9 Ma. Geochemical investigations revealed that the Bingdaban gabbros exhibit tholeiitic composition, suggesting a genesis associated with enriched mid-ocean ridge basalt (E-MORB). Mineralogical analyses indicated that the clinopyroxene in the gabbros was Mg-rich, Fe-poor, and alkali-poor, representing a subalkaline series. The compositional end members of clinopyroxene were calculated as Wo_38.9–48.0En_30.9–48.1Fs_10.4–24.4, indicating a predominance of diopside with a minor amount of augite. Temperature–pressure conditions imply that these rocks formed in a high-temperature, low-pressure, and shallow-source environment. Compositional estimates of the melt in equilibrium with clinopyroxene are consistent with the overall characteristics of the host rock, reflecting an E-MORB setting. The Bingdaban gabbro likely originated from an initially depleted mantle source that later received an input of enriched mantle material, indicating formation in either an initial oceanic or immature back-arc basin tectonic setting. Full article

(This article belongs to the Special Issue On the Formation and Alteration of Ophiolites and Oceanic Lithospheres)

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11 pages, 5016 KiB

Open AccessArticle

Effects of Sec-Octanol and Terpineol on Froth Properties and Flotation Selectivity Index for Microcrystalline Graphite

by Xuexia Wang, Juan Zhang, Muhammad Bilal, Xiangning Bu and Yemin Wang

Minerals 2023, 13(9), 1231; https://doi.org/10.3390/min13091231 - 20 Sep 2023

Cited by 1 | Viewed by 1188

Abstract

Microcrystalline graphite is a valuable non-metallic mineral that can be separated by flotation, a physico-chemical processing method that uses air bubbles to capture mineral particles. The size and stability of the bubbles, which depend on the type and amount of frother added, affect [...] Read more.

Microcrystalline graphite is a valuable non-metallic mineral that can be separated by flotation, a physico-chemical processing method that uses air bubbles to capture mineral particles. The size and stability of the bubbles, which depend on the type and amount of frother added, affect the flotation performance and the recovery of water from the froth layer. However, the effects of different types of frother on the froth properties and water recovery of microcrystalline graphite flotation are not well understood. In this study, two common frothers, sec-octanol and terpineol, were compared in terms of their effects on the bubble size, froth layer height, water recovery, and flotation selectivity index (SI) of microcrystalline graphite flotation. It was found that sec-octanol produced smaller bubbles than terpineol, but also a slightly lower froth layer height. The water recovery was higher with sec-octanol than with terpineol. The SI values were similar for both frothers, indicating comparable flotation performance. This study revealed the differences between sec-octanol and terpineol in terms of their effects on the froth properties and water recovery of microcrystalline graphite flotation. These findings can help optimize the choice and dosage of frother for this important mineral processing method. Full article

(This article belongs to the Special Issue Recent Advances in Flotation Process)

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13 pages, 3082 KiB

Open AccessArticle

Simulating the Impact of Ore and Water Quality on Flotation Recovery during the Life of a Mine

by Annukka Aaltonen, Caroline Izart, Mikko Lyyra, Aleksandra Lang, Eija Saari and Olli Dahl

Minerals 2023, 13(9), 1230; https://doi.org/10.3390/min13091230 - 19 Sep 2023

Viewed by 1681

Abstract

Blending of different ore types in the concentrator feed contributes significantly to maintaining a high recovery of valuable minerals with required grades in the concentrate. It is feasible to develop an ore-blending scheme over the life of a mine already in the design [...] Read more.

Blending of different ore types in the concentrator feed contributes significantly to maintaining a high recovery of valuable minerals with required grades in the concentrate. It is feasible to develop an ore-blending scheme over the life of a mine already in the design phase of the plant. In addition to ore characteristics, water quality is known to impact mineral recovery. A blending plan could also be developed for the different water streams of a future concentrator. This paper describes a novel modeling and simulation approach to predict metallurgical response combining ore types and water quality. The model is based on kinetic laboratory flotation test data, and it was tested on a case study. As a result, rougher flotation grade-recovery curves dependent on ore types and water quality are presented over the predicted life of the mine. The simulation results can be exploited in project design to maximize the recovery of valuable minerals and to ensure environmentally sound and profitable mining operations. Overall, the developed modeling tool can be applied widely for minerals processed by using froth flotation and water types available for kinetic laboratory flotation tests. Full article

(This article belongs to the Special Issue Recent Advances in Flotation Process)

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10 pages, 5554 KiB

Open AccessArticle

Novel Second-Order Derivative-Based Filters for Edge and Ridge/Valley Detection in Geophysical Data

by Gordon Robert John Cooper

Minerals 2023, 13(9), 1229; https://doi.org/10.3390/min13091229 - 19 Sep 2023

Cited by 1 | Viewed by 906

Abstract

Derivative-based high-pass filters of various types are commonly applied to potential field data to reveal subtle or hard-to-see structures in the quest for mineral exploration. One approach is to exploit the fact that data have an amplitude and phase component in the space [...] Read more.

Derivative-based high-pass filters of various types are commonly applied to potential field data to reveal subtle or hard-to-see structures in the quest for mineral exploration. One approach is to exploit the fact that data have an amplitude and phase component in the space domain. In the past, this has been used to produce first-order derivative-based enhanced datasets with minimal noise issues. The work is extended here to second-order derivative-based filters, which are useful in enhancing not just edges but also ridges and valleys in data. The filters compare favourably with existing second-order derivative-based filters that were applied to gravity and magnetic datasets from South Africa. Full article

(This article belongs to the Special Issue Applications of Gravity and Magnetics to Mineral Exploration)

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15 pages, 37269 KiB

Open AccessArticle

Characterisation and Environmental Significance of Glauconite from Mining Waste of the Egorievsk Phosphorite Deposit

by Natalia Kalinina, Prokopiy Maximov, Boris Makarov, Evan Dasi and Maxim Rudmin

Minerals 2023, 13(9), 1228; https://doi.org/10.3390/min13091228 - 19 Sep 2023

Cited by 3 | Viewed by 2226

Abstract

This article presents the results of a study of glauconite obtained from phosphate rock waste. The aim is to study the morphological, structural and chemical characteristics of glauconite and to determine the potential for secondary use of mining waste in the agricultural sector. [...] Read more.

This article presents the results of a study of glauconite obtained from phosphate rock waste. The aim is to study the morphological, structural and chemical characteristics of glauconite and to determine the potential for secondary use of mining waste in the agricultural sector. The electromagnetic separation method was used to obtain glauconite concentrate. The optimum parameters for obtaining the maximum mineral content in the concentrate were determined. Studies have shown that glauconite is characterised by globular, granular grains of the highly mature variety. Glauconite almost invariably contains inclusions of pyrite and apatite, which significantly improve the characteristics of the fertiliser. Laboratory experiments have shown that glauconite waste and glauconite concentrate have a positive effect on plant growth and development. The high potassium content, the favourable globular shape of the grains, and the presence of apatite and pyrite inclusions indicate the potential use of glauconite from mining waste as a potash fertiliser. Application of glauconite fertiliser to the soil will provide an opportunity to improve its texture, providing better moisture and aeration. The use of glauconite fertiliser is particularly valuable on acidic soils where apatite can be dissolved, making phosphorus available to plants. This nutrient additionally favours plant growth, as well as reducing the risk of heavy metal accumulation in the soil. Thus, glauconite from the waste of the Egorievsk deposit represents a promising fertiliser for improving soil quality and increasing crop yields. Full article

(This article belongs to the Special Issue Reuse and Recycling of Phosphate Mine Wastes)

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11 pages, 1425 KiB

Open AccessEditor’s ChoiceArticle

Insights into the Heterogeneity of the Mercury Isotopic Fingerprint of the Idrija Mine (Slovenia)

by Dominik Božič, Igor Živković, Tatjana Dizdarević, Martina Peljhan, Marko Štrok and Milena Horvat

Minerals 2023, 13(9), 1227; https://doi.org/10.3390/min13091227 - 18 Sep 2023

Viewed by 1044

Abstract

To determine the range of the isotopic composition of mercury (Hg) from the Idrija mine, samples from the mine itself and from the Mercury Heritage Management Centre geological collection were analyzed. Samples from various geological periods, genesis types, ore types, formations, and excavation [...] Read more.

To determine the range of the isotopic composition of mercury (Hg) from the Idrija mine, samples from the mine itself and from the Mercury Heritage Management Centre geological collection were analyzed. Samples from various geological periods, genesis types, ore types, formations, and excavation fields and levels were analyzed. Both Hg concentration and isotopic composition were measured. The δ²⁰²Hg ranged from −1.35‰ to 0.46‰, and the Δ¹⁹⁹Hg ranged from −0.18‰ to 0.16‰. A relatively homogenous ore fingerprint was obtained from one of the excavation fields; otherwise, the isotopic fingerprint of the Idrija mine seems to be heterogenous. This study presents the first statistically robust constraints on the isotopic composition of Hg from the Idrija mine, which may help in further studies of the isotopic composition of similar ore bodies or the potential tracing of Hg from the mine to the environment in the vicinity or downstream of the mine. Full article

(This article belongs to the Special Issue Isotope Geochemical Analysis Technology and Its Applications)

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11 pages, 3306 KiB

Open AccessArticle

Real-Time Atomic Scale Kinetics of a Dynamic Event in a Model Ionic Crystal

by Pat Kalita, Paul E. Specht, Justin L. Brown, Lena M. Pacheco, Josh M. Usher and Christopher T. Seagle

Minerals 2023, 13(9), 1226; https://doi.org/10.3390/min13091226 - 18 Sep 2023

Cited by 1 | Viewed by 939

Abstract

The mineral CaF₂ is the archetype of the α fluorite structure and its high-pressure phase transition to γ cotunnite is an ideal test bed for exploring the effects of kinetics. The inter-disciplinary topic of the kinetics of dynamically driven phase transitions is [...] Read more.

The mineral CaF₂ is the archetype of the α fluorite structure and its high-pressure phase transition to γ cotunnite is an ideal test bed for exploring the effects of kinetics. The inter-disciplinary topic of the kinetics of dynamically driven phase transitions is at the forefront of condensed matter physics, both for its theoretical importance and its relevance to technological applications at extreme conditions of pressure and temperature. Here we probe the α → γ → α structural transformations taking place over the nanosecond timescale of a dynamic event, beginning-to-end: from the principal shock Hugoniot state, followed by a quasi-steady off-Hugoniot release state, and finally the unsteady return to near-ambient conditions. We present quantitative, atomic-scale data of the unfolding of the dynamically driven phase transition and its subsequent reversal close to the α/γ phase boundary. Dynamic loading with a two-stage gas gun is coupled with in situ time-resolved synchrotron X-ray diffraction and with continuum scale velocimetry at the Dynamic Compression Sector (DCS), Advanced Photon Source, Argonne National Laboratory. Our results demonstrate the time dependence of phase transitions and highlight the need for modeling of transition kinetics in dynamically driven processes. Full article

(This article belongs to the Special Issue Crystal Structures and Phase Transitions of Minerals at Extreme Conditions)

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Phase diagram of CaF2. The principal Hugoniot is indicated with a black line [<a href="#B2-minerals-13-01226" class="html-bibr">2</a>]. The two initial Hugoniot states examined in this work are marked with stars (14 GPa and 19 GPa on the Hugoniot). Phase boundaries are from reference [<a href="#B10-minerals-13-01226" class="html-bibr">10</a>], and specifically the α/γ boundary is from DAC data and first principles simulations. Full article ">Figure 2
Experimental setup for nanosecond-scale DXRD at the Advanced Photon Source, Sector 35, DCS, and an example ICCD image of the CaF2 sample showing diffracted Debye rings. Simulations of stress states within the sample (discussed below) were obtained along the path of the X-ray beam. Full article ">Figure 3
Example results of the DXRD experiments: X-ray diffraction patterns prior to impact (t-0) and after impact (t-1 to t-4). Patterns illustrate the forward α → γ phase transition and the backwards γ → α phase transition caused by the evolution of stress states over the time of the dynamic experiment. Grey bands indicate the regions where new peaks of the γ phase appear. Full article ">Figure 4
Rietveld full profile structural refinement of XRD patterns in <a href="#minerals-13-01226-f003" class="html-fig">Figure 3</a> at selected times: (a) at time t-2, and (b) later on at time t-4, illustrating the phase composition of α fluorite and γ cotunnite phases along the measured XRD pattern, the modelled (refined) pattern, background, and Miller indices for the two phases. Full article ">Figure 4 Cont.
Rietveld full profile structural refinement of XRD patterns in <a href="#minerals-13-01226-f003" class="html-fig">Figure 3</a> at selected times: (a) at time t-2, and (b) later on at time t-4, illustrating the phase composition of α fluorite and γ cotunnite phases along the measured XRD pattern, the modelled (refined) pattern, background, and Miller indices for the two phases. Full article ">Figure 5
Dynamic compression to an over pressurized principal Hugoniot state (~19 GPa) and the corresponding kinetics of the α → γ → α phase transitions. (a) Hydrodynamic simulations of the stress distribution in the dynamically compressed sample, along the path of the X-ray beam over the entire ~600 ns shock event, start-to-end. At any point in time, a hypothetical vertical line drawn across the figure gives the stress distribution in the sample, as seen by the X-ray beam at that instant. (b) Kinetics of the α → γ → α phase transitions: quantitative fractions of α and γ-CaF2 phases. Fractions were obtained from Rietveld refinements of the four DXRD snapshots collected on dynamic compression to 19 GPa. (c) Comparison of experimental vs. equilibrium expected percentage of γ phase, assuming a scenario where the phase transition was instantaneous and started at a stress of at least 9 GPa (vs. 10.5 GPa on the phase diagram) to account for simulation uncertainties, shock heating, and the negative Clapeyron slope of the α → γ phase transition. In all panels, the timescale axes are identical and vertical dashed lines are placed at the same time marks. Numbers 1, 2, and 3 identify the three stress regions discussed below: 1—principal Hugoniot state; 2—off-Hugoniot state, and 3—return to near-ambient conditions. Full article ">Figure 6
Dynamic compression at the edge of the equilibrium α/γ phase boundary (principal Hugoniot state of ~14 GPa) and the corresponding kinetics of the α → γ → α phase transitions. (a) Hydrodynamic simulations of the stress distribution in the dynamically compressed sample along the path of the X-ray beam over the entire ~600 ns shock event, start-to-end. At any point in time, a hypothetical vertical line drawn across the figure gives the stress distribution in the sample, as seen in the X-ray beam at that instant. (b) Kinetics of the α → γ → α phase transitions: quantitative fractions of α and γ-CaF2 phases. Fractions were obtained from Rietveld refinements of the four DXRD snapshots collected on dynamic compression to 19 GPa. (c) Comparison of experimental vs. equilibrium expected percentage of γ phase, assuming a scenario where the phase transition is instantaneous and starts at a stress of at least 9 GPa (vs. 10.5 GPa on the phase diagram) to account for simulation uncertainties, shock heating, and the negative Clapeyron slope of the α → γ phase transition. In all panels the timescale axes are identical and vertical dashed lines are placed at the same time marks. Numbers 1, 2, and 3 identify the three stress regions discussed below: 1—principal Hugoniot state; 2—off-Hugoniot state, and 3—return to near-ambient conditions. Full article ">Figure 6 Cont.
Dynamic compression at the edge of the equilibrium α/γ phase boundary (principal Hugoniot state of ~14 GPa) and the corresponding kinetics of the α → γ → α phase transitions. (a) Hydrodynamic simulations of the stress distribution in the dynamically compressed sample along the path of the X-ray beam over the entire ~600 ns shock event, start-to-end. At any point in time, a hypothetical vertical line drawn across the figure gives the stress distribution in the sample, as seen in the X-ray beam at that instant. (b) Kinetics of the α → γ → α phase transitions: quantitative fractions of α and γ-CaF2 phases. Fractions were obtained from Rietveld refinements of the four DXRD snapshots collected on dynamic compression to 19 GPa. (c) Comparison of experimental vs. equilibrium expected percentage of γ phase, assuming a scenario where the phase transition is instantaneous and starts at a stress of at least 9 GPa (vs. 10.5 GPa on the phase diagram) to account for simulation uncertainties, shock heating, and the negative Clapeyron slope of the α → γ phase transition. In all panels the timescale axes are identical and vertical dashed lines are placed at the same time marks. Numbers 1, 2, and 3 identify the three stress regions discussed below: 1—principal Hugoniot state; 2—off-Hugoniot state, and 3—return to near-ambient conditions. Full article ">

17 pages, 12062 KiB

Open AccessArticle

Montbrayite from the Svetlinsk Gold–Telluride Deposit (South Urals, Russia): Composition Variability and Decomposition

by Olga V. Vikent’eva, Vladimir V. Shilovskikh, Vasily D. Shcherbakov, Tatyana N. Moroz, Ilya V. Vikentyev and Nikolay S. Bortnikov

Minerals 2023, 13(9), 1225; https://doi.org/10.3390/min13091225 - 18 Sep 2023

Cited by 2 | Viewed by 1301

Abstract

A rare gold–telluride montbrayite from the large Svetlinsk gold–telluride deposit (South Urals, Russia) was comprehensively studied using optical microscopy, scanning electron microscopy, electron microprobe analysis, reflectance measurements, electron backscatter diffraction, and Raman spectroscopy. Significant variations in the composition of the mineral were revealed [...] Read more.

A rare gold–telluride montbrayite from the large Svetlinsk gold–telluride deposit (South Urals, Russia) was comprehensively studied using optical microscopy, scanning electron microscopy, electron microprobe analysis, reflectance measurements, electron backscatter diffraction, and Raman spectroscopy. Significant variations in the composition of the mineral were revealed (in wt%): Au 36.98–48.66, Te 43.35–56.53, Sb 2.49–8.10, Ag up to 4.56, Pb up to 2.04, Bi up to 0.33, Cu up to 1.42. There are two distinct groups with much more-limited variation within the observed compositional interval (in wt%): (1) Au 36.98–41.22, Te 49.35–56.53, Sb 2.49–5.57; (2) Au 47.86–48.66, Te 43.35–44.92, Sb 7.15–8.10. The empirical formula calculated on the basis of 61 apfu is Au_{16.43–23.28}Sb_1.79–6.09Te_{32.01–38.89}Ag_0–3.69Bi_0–0.14Pb_0–0.90Cu_0–1.96. Two substitution mechanisms for antimony are proposed in the studied montbrayite grains: Sb→Au (2.5–5.6 wt% Sb) and Sb→Te (7–8 wt% Sb). The dependence of the reflection spectra and Raman spectra on the antimony content and its substitution mechanism, respectively, was found in the mineral. The slope of the reflectance spectra decreases and the curve in the blue–green region of the spectrum disappears with increasing Sb content in montbrayite. Raman spectra are reported for the first time for this mineral. The average positions of the peak with high-intensity are ~64 cm⁻¹ and ~90 cm⁻¹ for montbrayite with Sb→Te and Sb→Au, respectively. Two grains of montbrayite demonstrate decomposition according to two schemes: (1) montbrayite (7 wt% Sb) → native gold + calaverite ± altaite, and (2) montbrayite (5 wt% Sb) → native gold + tellurantimony ± altaite. A combination of melting and dissolution–precipitation processes may be responsible for the formation of these decomposition textures. Full article

(This article belongs to the Special Issue Native Gold as a Specific Indicator Mineral for Gold Deposits, 2nd Edition)

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11 pages, 4585 KiB

Open AccessArticle

Identification of the Pigments on the Mural Paintings from an Ancient Chinese Tomb of Tang Dynasty Using Micro-Raman and Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy Analysis

by Zhaojun Liu, Wenzhong Xu, Yongjian Zhang, Yingying Wang and Jinwei Li

Minerals 2023, 13(9), 1224; https://doi.org/10.3390/min13091224 - 18 Sep 2023

Cited by 5 | Viewed by 1963

Abstract

The tomb of Hanxiu, a prime minister of the Tang dynasty who died in 740 CE, was decorated with elaborate mural paintings. The pigments used in the mural paintings were collected from representative colours before a restoration process and analyzed using micro-Raman and [...] Read more.

The tomb of Hanxiu, a prime minister of the Tang dynasty who died in 740 CE, was decorated with elaborate mural paintings. The pigments used in the mural paintings were collected from representative colours before a restoration process and analyzed using micro-Raman and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDS) analysis to characterize the chemical compositions. The results reveal the chromatic palette and the painting technique used in the mural paintings. Most of the pigments are natural mineral pigments similar to those excavated in previous archaeological works, except the yellow pigment is unusual. A rare mineral pigment, vanadinite [Pb₅(VO₄)₃Cl], was employed in a large amount as the yellow pigment. This phenomenon was analyzed and compared with tomb mural paintings from varied periods and locations in ancient China. Notably, the identification of vanadinite via Raman spectra has to be performed carefully and combined with an elemental analysis to avoid misidentification. Full article

(This article belongs to the Special Issue Colours in Minerals and Rocks, Volume II)

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15 pages, 1565 KiB

Open AccessReview

Development Review on Leaching Technology and Leaching Agents of Weathered Crust Elution-Deposited Rare Earth Ores

by Zhigao Xu, Gang Li, Huifang Yang, Aoyang Sha, Zhengyan He, Yuchen Tang, Ming Wu and Jun Qu

Minerals 2023, 13(9), 1223; https://doi.org/10.3390/min13091223 - 17 Sep 2023

Cited by 5 | Viewed by 2702

Abstract

Weathered crust elution-deposited rare earth ores are key strategic resources and the main source of medium and heavy rare earths. This paper summarizes the development of leaching technology of rare earth ores, compares the advantages and disadvantages of the three generations of leaching [...] Read more.

Weathered crust elution-deposited rare earth ores are key strategic resources and the main source of medium and heavy rare earths. This paper summarizes the development of leaching technology of rare earth ores, compares the advantages and disadvantages of the three generations of leaching technology, and introduces the improved heap leaching technology and the new technology of the leaching–extraction integration and enhanced leaching, focusing on the leaching of weathered crust elution-deposited rare earth ores. In this paper, the development of the leaching agents is expounded, and the research status and the development trend of the composite ammonium salt leaching agent, impurity inhibition leaching agent, swelling inhibition leaching agent, and seepage-promotion leaching agent are also introduced. And this paper summarizes the leaching mechanism and the development direction of leaching agents. Moreover, the future key research direction of weathered crust elution-deposited rare earth ores is proposed, which is green, efficient, safe development and utilization. Full article

(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)

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21 pages, 6185 KiB

Open AccessArticle

Early Triassic (Griesbachian) Deposits of High-Energy Events at the Northwestern Upper Yangtze Region, China

by Dan Qiao, Xiong Duan and Zhiqiang Shi

Minerals 2023, 13(9), 1222; https://doi.org/10.3390/min13091222 - 17 Sep 2023

Viewed by 1125

Abstract

Following the latest Permian mass extinction (LPME), the ocean experienced turbulent conditions due to elevated temperatures during the Griesbachian (Early Triassic). These adverse conditions resulted in a prolonged delay in biotic recovery. However, the current understanding of the sedimentological responses of the ocean [...] Read more.

Following the latest Permian mass extinction (LPME), the ocean experienced turbulent conditions due to elevated temperatures during the Griesbachian (Early Triassic). These adverse conditions resulted in a prolonged delay in biotic recovery. However, the current understanding of the sedimentological responses of the ocean at that time to these adverse conditions remains incomplete. The Griesbachian harsh ocean conditions led to the formation of abnormal carbonate rocks (known as anachronistic facies) all around the world. These facies were influenced by a combination of environmental conditions, biotic factors, and actualistic sedimentological processes (e.g., waves and currents, sedimentation). However, the role of actualistic sedimentological processes in forming anachronistic facies during the Griesbachian has been underemphasized in the existing studies. In this research, we examine calcirudite beds, such as flat-pebble conglomerates, from Member 1 of the Feixianguan Formation across multiple sections, including Shangsi, Yudongzi, Dagouli, and Jianfeng in the Upper Yangtze Region. Our analysis is grounded in field investigations, thin-section observations, and the study of triggering mechanisms and formation processes. We identified and described five calcirudite beds (S1–S5) in the Shangsi section, two beds (D1–D2) in the Dagouli section, one at Jianfeng (J1), and one (Y1) in the Yudongzi section. Bed S1 features matrix-supported flat pebbles with a normal grading, interpreted as the result of a debris flow mass-transport process. Beds S2, S3, D1, and J1 contain large mud rip-up clasts, ooids, and bioclasts, suggesting a potential link with tsunami backwash. Beds S4, D2, and Y1 display hummocky cross-stratification and ‘chrysanthemum-shaped’ flat pebbles, indicating storm influence. The presence of vermicular limestones in Bed S5 suggests harsh marine environmental conditions. Collectively, this evidence suggests that high-energy oceanic conditions, including tsunamis and frequent storms, potentially influenced Early Triassic biotic recovery. Full article

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21 pages, 25486 KiB

Open AccessArticle

Revealing the Secrets behind the Color and Sea-Wave Patterns of Larimar

by Hao-Ming Huang, Yu-Hong Shih, Huei-Fen Chen, Hao-Yang Lee, Jiann-Neng Fang, Chuan-Chou Shen and Bing-Sheng Yu

Minerals 2023, 13(9), 1221; https://doi.org/10.3390/min13091221 - 17 Sep 2023

Cited by 2 | Viewed by 3169

Abstract

In the last century, a blue–green colored gemstone known as Larimar with a special sea-wave pattern was discovered in the Dominican Republic. Larimar is composed of the mineral pectolite, which has a chemical composition of NaCa₂Si₃O₈(OH) and [...] Read more.

In the last century, a blue–green colored gemstone known as Larimar with a special sea-wave pattern was discovered in the Dominican Republic. Larimar is composed of the mineral pectolite, which has a chemical composition of NaCa₂Si₃O₈(OH) and is usually white in color. Cu²⁺ has always been considered to be the primary genesis of the blue color shown in Larimar, because native copper often grows together with Larimar. To clarify whether copper is the main reason for the origin of blue–green pectolite, we utilized laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) techniques to analyze trace elements in the pectolite samples and compared the relationship between elements and colors. The results show that vanadium and iron are the main origins of the sky-blue and green color of Larimar. We also discovered that it is not only the chemical elements that affect the color shades of the mineral, but the orientation of the radial fiber crystals also plays a critical role. The sea-wave pattern and the changes in the color saturation of radial pectolite are due to the transmittance of visible light through different viewed angles under changing crystal orientations. Our results reveal the chemical and physical factors behind the color and sea-wave pattern of Larimar. In addition, to our knowledge, this is the first time that the formation age of Larimar has been proven to be approximately equal to or younger than 40 ka, using the U-Th dating of calcite growth together with pectolite. Full article

(This article belongs to the Special Issue Gem Deposits: Mineralogical and Gemological Aspects)

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27 pages, 6832 KiB

Open AccessArticle

Pore Characteristics, Oil Contents and Factors Influencing Laminated Shale in the First Member of the Qingshankou Formation in the Gulong Sag, Northern Songliao Basin

by Yuxuan Zhang, Huifang Pan, Yubin Bai, Guolong Chen, Jinglan Luo and Yang Zhang

Minerals 2023, 13(9), 1220; https://doi.org/10.3390/min13091220 - 17 Sep 2023

Cited by 5 | Viewed by 1279

Abstract

To clarify the reservoir characteristics of laminated shale, the occurrence mechanism of shale oil and its influencing factors in the Gulong Sag, northern Songliao Basin, are studied to better guide the exploration and development of shale oil there. First, X-ray diffraction (XRD) and [...] Read more.

To clarify the reservoir characteristics of laminated shale, the occurrence mechanism of shale oil and its influencing factors in the Gulong Sag, northern Songliao Basin, are studied to better guide the exploration and development of shale oil there. First, X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) are used to characterize the pore types, pore geneses and factors influencing the pore volume in the study area. Second, the organic matter of the samples is extracted with a mixture of dichloromethane and methanol. Total organic carbon (TOC), nitrogen adsorption and Rock-Eval tests are performed on the samples before and after extraction to reveal the pore size distribution after extraction. The factors influencing free and adsorbed shale oil and the lower limit of pore size are discussed in detail. The results show that interparticle pores (interP pores), intraparticle pores (intraP pores), organic matter pores (OM pores) and microfractures can be found in the laminated shale (Q1) in the Gulong Sag, Songliao Basin, and that the interP pores and intercrystalline pores in clay minerals are the main pores. The FE-SEM results show that the diameters of interP pores vary from several hundred nanometers to several microns, and their morphologies are mainly triangular, strip-shaped or irregular. The morphology of the intercrystalline pores in the clay minerals is generally irregular, depending on the crystal type and arrangement of clay minerals. According to the characteristics of the nitrogen adsorption and desorption curves, the pore morphologies are mainly slit-shaped pores, parallel-plate-shaped pores and ink-bottle-shaped pores. The pore size distribution is mostly bimodal, and the pore volume contribution is the greatest in the pore size range of 10~20 nm. Before and after extraction, the overall characteristics of the pore size distribution change only slightly, but the number of micropores increases significantly. Different minerals have different degrees of influence on the proportions of micropores, mesopores and macropores. Quartz mainly inhibits the formation of micropores, while the overall effect on mesopores and macropores is positive depending on the diagenetic period. Feldspar has a strong positive correlation with the micropore and mesopore proportions but is not highly correlated with the macropore proportions. The influence of the carbonate mineral content on the pore volume is not obvious because of its complex composition. The TOC content and vitrinite reflectance (Ro) are the two most important factors controlling free oil and adsorbed oil, and the contents of mineral components, such as felsic minerals, carbonate minerals and clay minerals, have no obvious correlation with shale oil content. With increasing pore volume, the contents of free oil and adsorbed oil increase, but the proportion of adsorbed oil decreases gradually. The correlation between the specific surface area and adsorbed oil content is poor. At normal temperatures and pressures, the lower limit of the pore diameters that can contain free oil is 4 nm, and the lower limit of the pore diameters that can contain movable oil is 10 nm. Full article

(This article belongs to the Special Issue Geochemical Characterization of Source Rocks in Oil and Gas Fields)

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2 pages, 188 KiB

Open AccessEditorial

Editorial for Special Issue “Hydrodynamics and Gas Dispersion in Flotation”

by Luis Vinnett and César O. Gómez

Minerals 2023, 13(9), 1219; https://doi.org/10.3390/min13091219 - 17 Sep 2023

Viewed by 828

Abstract

Gas dispersion, the breakage of a mass of gas into a population of small bubbles, is one of the most important subprocesses occurring in flotation machines [...] Full article

(This article belongs to the Special Issue Hydrodynamics and Gas Dispersion in Flotation)

13 pages, 6239 KiB

Open AccessTechnical Note

Direct Tensile Measurement for Cemented Paste Backfill

by Andrew Pan and Murray Grabinsky

Minerals 2023, 13(9), 1218; https://doi.org/10.3390/min13091218 - 16 Sep 2023

Viewed by 1116

Abstract

Tensile strength is a crucial parameter involved in the design and analysis of cemented paste backfill (CPB). The ability of CPB to withstand tensile forces is essential for the stability of the backfilled stopes, particularly in areas with high stress or deformation. The [...] Read more.

Tensile strength is a crucial parameter involved in the design and analysis of cemented paste backfill (CPB). The ability of CPB to withstand tensile forces is essential for the stability of the backfilled stopes, particularly in areas with high stress or deformation. The tensile strength is a critical design parameter used in sill mats to perform underhand cut-and-fill operations. This study presents a novel technique that utilizes rectangular dog-bone specimens and compression to tensile load converters to perform the direct determination of tensile strength. This study indicates that the prevailing assumption regarding the ratio of unconfined compressive strength (UCS) to tensile strength (i.e., 10:1 or 12:1) underestimates the strength. The results suggest a ratio closer to 3:1 or 4:1. The findings indicate that the ratio varies with the curing interval. Specifically, the tensile-to-compressive strength ratios were higher in early-age specimens, as tensile strength values do not increase at the same rate as those of compressive strength. This disparity has notable implications, as underestimating tensile strength via traditional UCS-to-tensile strength ratios could potentially inflate binder consumption. Our study underscores the importance of using direct tensile strength measurements to optimize mining operations. Full article

(This article belongs to the Special Issue Cemented Mine Waste Backfill: Experiment and Modelling)

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14 pages, 3223 KiB

Open AccessArticle

Distinct Groups of Low- and High-Fe Ferropericlase Inclusions in Super-Deep Diamonds: An Example from the Juina Area, Brazil

by Felix V. Kaminsky, Dmitry A. Zedgenizov, Vyacheslav S. Sevastyanov and Olga V. Kuznetsova

Minerals 2023, 13(9), 1217; https://doi.org/10.3390/min13091217 - 15 Sep 2023

Viewed by 1126

Abstract

Diamonds from the Rio Sorriso placer in the Juina area, Mato Grosso State, Brazil, contain mineral inclusions of ferropericlase associated with MgSiO₃, CaSiO₃, magnesite, merrillite, and other minerals. The ferropericlase inclusions in Rio Sorriso diamonds are resolved into two [...] Read more.

Diamonds from the Rio Sorriso placer in the Juina area, Mato Grosso State, Brazil, contain mineral inclusions of ferropericlase associated with MgSiO₃, CaSiO₃, magnesite, merrillite, and other minerals. The ferropericlase inclusions in Rio Sorriso diamonds are resolved into two distinct genetic and compositional groups: (1) protogenetic, high-Ni and low-Fe (Ni = 8270–10,660 ppm; mg# = 0.756–0.842) ferropericlases, and (2) syngenetic, low-Ni and high-Fe (Ni = 600–3050 ppm; mg# = 0.477–0.718) ferropericlases. Based on the crystallographic orientation relationships between natural ferropericlase inclusions and host diamonds, high-Ni and low-Fe ferropericlases originate in the upper part of the lower mantle, while low-Ni and high-Fe ferropericlases, most likely, originate in the lithosphere. Mineral inclusions form the ultramafic lower-mantle (MgSiO₃, which we suggest as bridgmanite, CaSiO₃, which we suggest as CaSi-perovskite, and high-Ni and low-Fe ferropericlase) and lithospheric (CaSiO₃, which we suggest as breyite, Ca(Si,Ti)O₃, and low-Ni and high-Fe ferropericlase) associations. The presence of magnesite and merrillite inclusions in association with ferropericlase confirmed the existence of a deep-seated carbonatitic association. Diamonds hosting high-Ni and low-Ni ferropericlase have different carbon-isotopic compositions (δ¹³C = −5.52 ± 0.75‰ versus −7.07 ± 1.23‰ VPDB, respectively). It implies the carbon-isotopic stratification of the mantle: in the lower mantle, the carbon-isotopic composition tends to become isotopically heavier (less depleted in ¹³C) than in lithospheric diamonds. These regularities may characterize deep-seated diamonds and ferropericlases not only in the Juina area of Brazil but also in other parts of the world. Full article

(This article belongs to the Special Issue Kimberlites and Related Rocks: New Insight into Petrogenesis and Diamond Potential of Deeply-Derived Mantle Magmas)

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Crystals of ferropericlase included in the Rio Sorriso diamonds. (a) Sample #2.2.1. (b) Sample #3.1.3b. (c) Sample #3.1.3c (all high-Ni and low-Fe). (d) Sample #3.6.3a (low-Ni and high-Fe). Full article ">Figure 2
Distribution of the Mg index (mg#) in ferropericlase grains. The arrows indicate the positions of average mg# values for two groups of ferropericlase. Full article ">Figure 3
Ni content vs. Mg index (mg#) in ferropericlase grains. Full article ">Figure 4
Magnesite in touching association with ferropericlase included in Rio Sorriso diamond #1.2.4. (a)—Electronic image. (b)—Its Raman spectrum. Full article ">Figure 5
Inclusions of merrillite in diamond #3.10.2 from the Rio Sorriso area. From [<a href="#B21-minerals-13-01217" class="html-bibr">21</a>], with permission from the Mineralogical Society of America. Full article ">Figure 6
Raman spectra of merrillite. (a) From sample 3.6.2. (b) From sample 3.10.2. From [<a href="#B21-minerals-13-01217" class="html-bibr">21</a>], with permission from the Mineralogical Society of America. Full article ">Figure 7
Carbon isotopic composition in Rio Sorriso diamonds. (a) With low-Ni and high-Fe ferropericlase inclusions. (b) With high-Ni and low-Fe ferropericlase inclusions. (c) All diamonds studied. Full article ">

16 pages, 5167 KiB

Open AccessArticle

The Mineralogy, Geochemistry and Origin of the Supergene Manganese Occurrences in the Southern Minas Gerais, Brazil

by Davi Diorio Parrotti, Fabiano Tomazini da Conceição and Guillermo Rafael Beltran Navarro

Minerals 2023, 13(9), 1216; https://doi.org/10.3390/min13091216 - 15 Sep 2023

Viewed by 1642

Abstract

In equatorial and tropical regions, supergene mineral deposits created during water/rock interactions are found. Simply put, these supergene deposits are formed through the accumulation of low solubility ions or through the preservation of primary minerals. The supergene manganese (Mn) deposits are examples of [...] Read more.

In equatorial and tropical regions, supergene mineral deposits created during water/rock interactions are found. Simply put, these supergene deposits are formed through the accumulation of low solubility ions or through the preservation of primary minerals. The supergene manganese (Mn) deposits are examples of the economic importance associated with the chemical weathering processes. In Brazil, the Southern Brasilia Orogen (SBO) was generated during the collision between the Paranapanema Craton and the passive margin of the São Francisco Craton. In the southern Minas Gerais (MG), several supergene Mn occurrences are hosted in the SBO, which were originated during the chemical weathering of gondites belonging to the Amparo Complex. Here, we studied the supergene Mn occurrences in the southern MG, more specifically in the municipalities of Ouro Fino and Careaçu. The MnO contents ranged from 25.50 to 28.40 wt% at Ouro Fino and from 16.80 to 21.20 wt% at Careaçu. These supergene Mn deposits have a diverse mineral assemblage, being composed of spessartine, quartz, Mn-oxides, goethite and kaolinite. The various Mn minerals formed due to spessartine incongruent dissolution were hollandites, cryptomelanes, romanechites, pyrolusites and lithiophorites. Both study areas are relevant for the possible opening of mines for the commercialization of Mn. Full article

(This article belongs to the Special Issue Weathering in the Tropics: A Multidisciplinary Approach)

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Map of eastern South America showing the main geological units relative to the Cratons, Orogenic Belts and Paraná Sedimentary Basin (modified from Hasui [<a href="#B19-minerals-13-01216" class="html-bibr">19</a>]) (a). MT, MS, RS, SC, PR, SP, GO, MG, RJ, ES and BA are the states of Mato Grosso, Mato Grosso do Sul, Rio Grande do Sul, Santa Catarina, Paraná, São Paulo, Goiás, Minas Gerais, Rio de Janeiro, Espírito Santo and Bahia, respectively Simplified geological map and supergene manganese occurrences in the southeastern São Paulo and southern MG regions (modified from Veríssimo [<a href="#B17-minerals-13-01216" class="html-bibr">17</a>]) (b). Full article ">Figure 2
Location of sampling points at Ouro Fino (O3—22°16′06.79″ S and 46°29′45.54″ W and O10—22°15′30.30″ S and 46°32′22.88″ W) and Careaçu (C1—22°03′08.60″ S and 45°40′53.40″ W and C2—22°02′46.90″ S and 45°39′58.87″ W) (image from Google Earth Pro—June 2021) (a). Landscape overview at sampling points O3 (b) and C2 (c). Outcrops of supergene manganese occurrences where samples O10 (d) and C1 (e) were collected (in detail, the massive structure of supergene manganese, with color black to dark gray). Full article ">Figure 3
Photomicrographs showing the supergene minerals between the grains of spessartine (Grt) and quartz (Qtz), such as Mn oxides (MnOx) (a–c), goethite (Gth) (b) and kaolinite (Kln) (d). MnOx was used during the petrography, because the optical microscopy does not allow us to identify their different mineral phases. Full article ">Figure 4
X-ray diffraction (XRD) patterns of supergene manganese occurrences collected at Ouro Fino (sample O10) (a) and Careaçu (sample C1) (b). Spessartine = Grt, quartz = Qtz. Full article ">Figure 5
SEM photomicrograph illustrating the supergene manganese occurrences collected at Ouro Fino (sample O3) (a,b) and Careaçu (sample C2) (c,d), with grains of spessartine (Grt), quartz (Qtz), hollandite (Hll) and cryptomelane (Cpm). The red spots were characterized for EDS. Full article ">Figure 6
Mn-(Fe + Ca) (a) and Mn-K (b) contents in the supergene manganese occurrences and spessartite, respectively, collected at Ouro Fino and at Careaçu. Full article ">Figure 7
Scheme illustrating the origin of the supergene Mn occurrences in the SBO: the basement reaches the Earth’s surface (a); beginning of chemical weathering of gneisses, where meteoric waters enrich in alkaline and alkaline earth elements (b); over a sufficient period of time, a deep stratified weathering profile is formed and the supergene Mn occurrences are originated (c); removal of the upper soil horizons, with the supergene Mn occurrences emerging on the Earth’s surface (d). The concomitant presence of soil and supergene Mn occurrences at Careaçu (e) and Ouro Fino (f). Full article ">

20 pages, 8994 KiB

Open AccessArticle

The Influence of Multi-Size Basalt Fiber on Cemented Paste Backfill Mechanical Properties and Meso-Structure Characteristics

by Xi Chen, Huazhe Jiao, Juanhong Liu, Yixuan Yang, Xinming Chen, Liuhua Yang, Wenxiang Zhang and Tongyi Yang

Minerals 2023, 13(9), 1215; https://doi.org/10.3390/min13091215 - 15 Sep 2023

Cited by 3 | Viewed by 1026

Abstract

As the mine enters the deep mining stage, there is a need to enhance the compressive strength and toughness of the backfill. The objective of this study is to examine the mechanical properties of cemented tailings backfill after the incorporation of multi-size fibers [...] Read more.

As the mine enters the deep mining stage, there is a need to enhance the compressive strength and toughness of the backfill. The objective of this study is to examine the mechanical properties of cemented tailings backfill after the incorporation of multi-size fibers and to validate the toughening mechanism of basalt fibers (BFs). To achieve this, a series of basic mechanical property tests for multi-size BFs mixing were devised, accompanied by industrial computerized tomography (CT) scanning and discrete element simulation. This study shows that the compressive strength increases and then decreases with the increase of BF dosage at a certain percentage of each size, and the splitting tensile strength gradually increases with the increase of BF dosage. The compressive strength tends to decrease and then increase, and the splitting tensile strength increases and then decreases as the fiber size ratio changes. The distribution of cemented tailings backfill and BF within the discrete element model is random. A few BF cannot play a bridging role; however, a moderate amount of BF is relatively uniformly distributed in the model to form a network structure, which generates a bond between the particles and the matrix and can effectively limit the expansion path of cracks and enhance the toughness. Full article

(This article belongs to the Special Issue Cemented Mine Waste Backfill: Experiment and Modelling)

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9 pages, 1819 KiB

Open AccessEditor’s ChoiceCommunication

Discovery of Mafic Granulites in the Muzhaerte Area, SW Tianshan, China

by Jun Yan, Ying Cui and Xiaoyu Liu

Minerals 2023, 13(9), 1214; https://doi.org/10.3390/min13091214 - 15 Sep 2023

Cited by 1 | Viewed by 972

Abstract

Accretionary and collisional orogeny are often accompanied by the disturbance of the geothermal gradient, leading to high-temperature metamorphism. High-temperature metamorphic rocks are significant in their ability to help the reconstruction of the thermal histories of orogenic belts. The Tianshan Orogenic Belt, at the [...] Read more.

Accretionary and collisional orogeny are often accompanied by the disturbance of the geothermal gradient, leading to high-temperature metamorphism. High-temperature metamorphic rocks are significant in their ability to help the reconstruction of the thermal histories of orogenic belts. The Tianshan Orogenic Belt, at the southwest margin of the Central Asian Orogenic Belt, is a record of the long-term subduction–collision–post-collision orogenic process that has taken place in the Phanerozoic Eon. Here, we report the discovery of mafic granulites in the Muzhaerte area, SW Tianshan. Petrographic observation reveals that the mafic granulites underwent two metamorphic stages. The peak mineral assemblage of the first stage is dominated by clinopyroxene + orthopyroxene + plagioclase + quartz + hornblende (hb¹) ± biotite, and the post-peak mineral assemblage of the second stage is dominated by clinopyroxene + plagioclase + quartz + hornblende (hb²) + biotite. The calculated results obtained from the two-pyroxene thermobarometers and the Al-in-hornblende barometer for the mafic granulites indicate that the metamorphic conditions of mafic granulites are 760–860 °C, <0.39–0.41 Gpa. The mafic granulites recorded a high-grade granulite facies thermal metamorphic event with the highest temperature limit currently recorded in the Central Tianshan Block. Full article

(This article belongs to the Special Issue Experimental Petrology: Metamorphic Evolution of Eclogite)

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Geological structure sketch of the Muzhaerte area, geological sketch and sampling location (modified after [<a href="#B43-minerals-13-01214" class="html-bibr">43</a>,<a href="#B48-minerals-13-01214" class="html-bibr">48</a>]). Full article ">Figure 2
Photomicrographs of the mafic granulites in the Muzhaerte area. (a) Equigranular granoblastic texture of granulites (taken in plane polarized light). (b) Anhedral crystal forms of the two pyroxenes (taken in plane polarized light). (c) Two pyroxenes have retrogressive amphibole reaction rims (taken in plane polarized light). (d) The clinopyroxene occurs as rounded porphyroblasts, containing biotite, hornblende and plagioclase inclusions (backscatter photo by JCM-6000PLUS). (e) Clinopyroxene develops oriented orthopyroxene rods along the c-axis (backscatter photo by JCM-6000PLUS). (f) The hornblende (hb2) formed at the rim of pyroxene or in the form of huge grains that contain some anhydrous inclusions (taken in plane polarized light). Mineral code: cpx—clinopyroxene; opx—orthopyroxene; hb—hornblende; bi—biotite; pl—plagioclase; q—quartz; ap—apatite; ilm—ilmenite. Full article ">Figure 3
Conjectural metamorphic P-T trajectory of the mafic granulites in the Muzhaerte area (modified after [<a href="#B58-minerals-13-01214" class="html-bibr">58</a>]). The mafic granulites underwent at least two metamorphic stages of peak and post-peak metamorphism. Metamorphic facies code: GR—granulite facies; HAM: high-amphibolite facies. Full article ">

16 pages, 9665 KiB

Open AccessArticle

Changing the Pulp Properties and Surface Hydrophilicity of Galena and Pyrite by Selecting the Appropriate Grinding Media Towards Their Selective Separation

by Qilin Zhai, Runqing Liu, Jia Li, Wei Sun and Yuehua Hu

Minerals 2023, 13(9), 1213; https://doi.org/10.3390/min13091213 - 15 Sep 2023

Cited by 4 | Viewed by 1134

Abstract

The grinding process plays a crucial role in the floatability of mineral. The present study proposes a scheme to assist in the flotation separation of galena and pyrite by optimizing the choice of grinding media. The effects of grinding media (cast iron balls, [...] Read more.

The grinding process plays a crucial role in the floatability of mineral. The present study proposes a scheme to assist in the flotation separation of galena and pyrite by optimizing the choice of grinding media. The effects of grinding media (cast iron balls, steel balls containing 18% chromium, and steel balls containing 12% chromium) on the pulp properties and hydrophilicity of galena and pyrite were evaluated using grinding tests, micro-flotation tests, X-ray photoelectron spectroscopy, and adsorption capacity analyses. The results showed significant differences in the pH, potential, and dissolved oxygen content of the galena or pyrite pulp with different grinding media, resulting in significant differences in the flotation behavior of galena and pyrite. The use of cast iron balls in the grinding process was more favorable for the flotation separation of galena and pyrite. The pyrite surfaces adsorbed less butyl xanthate when cast iron balls were used as grinding media due to the presence of more hydrophilic hydroxyl iron. Therefore, cast iron balls as grinding media are favorable for broadening the surface hydrophilic differences between galena and pyrite. Full article

(This article belongs to the Special Issue Recent Advances in Extractive Metallurgy)

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14 pages, 13311 KiB

Open AccessArticle

Rare Earth Element Characteristics in Coal Ash from the Jungar Energy Gangue Power Plant, Inner Mongolia, China

by Shaoqing Huang, Shuzheng Ning, Degao Zhang, Yuan Cai, Xiaoyun Yan, Kang Liu and Xiaotao Xu

Minerals 2023, 13(9), 1212; https://doi.org/10.3390/min13091212 - 15 Sep 2023

Cited by 4 | Viewed by 1550

Abstract

The coal and coal-bearing measures in the Jungar Coalfield in Inner Mongolia are characterized by rare earth element (REE) enrichment. Combustion in coal-fired power plants can lead to further enrichment of REEs in coal ash, which serves as a new potential source for [...] Read more.

The coal and coal-bearing measures in the Jungar Coalfield in Inner Mongolia are characterized by rare earth element (REE) enrichment. Combustion in coal-fired power plants can lead to further enrichment of REEs in coal ash, which serves as a new potential source for REE extraction and smelting. Further, investigating the content, modes of occurrence, and transformation behavior of REEs during coal combustion may help in better understanding REE differentiation during coal combustion and facilitate the development of economically feasible REE recovery technologies. Therefore, in this study, we analyzed coal ash from the Jungar Energy Gangue Power Plant in Inner Mongolia via inductively coupled plasma mass spectrometry, X-ray diffraction, and scanning electron microscopy combined with energy-dispersive spectroscopy. Our results showed that the REE content of the feed coal was 220 μg/g, slightly higher than the average for global coal. Additionally, fly ash had a higher REE content (898 μg/g) than bottom ash, and its rare earth oxide content was approximately 1152 μg/g, which meets the industrial requirements. Bottom and fly ashes contained similar minerals; however, their relative abundances were different. Specifically, mullite, quartz, calcite, and gypsum were slightly more abundant in fly ash than in bottom ash, whereas amorphous solids were slightly more abundant in bottom ash than in fly ash. Furthermore, fly ash, dominated by Si- and Al-rich minerals, was composed of irregular particles of different shapes and sizes. It also contained monazite and REE fluoro-oxides, which possibly originated from the feed coal and had mineral structures that remained unchanged during coal combustion. Thus, the REE fluoro-oxides possibly resulted from the conversion of bastnaesite in the feed coal during combustion and thereafter became attached to the edge of the Si–Al minerals in the fly ash. Full article

(This article belongs to the Special Issue Critical Metal Minerals in Coal)

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14 pages, 12958 KiB

Open AccessArticle

External Reflection FTIR Spectroscopy Applied to Archaeological Pottery: A Non-Invasive Investigation about Provenance and Firing Temperature

by Silvia Bruni, Margherita Longoni, Francesca De Filippi, Noemi Calore and Giovanna Bagnasco Gianni

Minerals 2023, 13(9), 1211; https://doi.org/10.3390/min13091211 - 15 Sep 2023

Cited by 1 | Viewed by 1741

Abstract

The mineralogical composition of archaeological pottery is closely related to the raw material and the firing conditions, thus constituting a source of information both on the origin and the manufacturing technology of ceramic artefacts. The techniques used to clarify the composition of the [...] Read more.

The mineralogical composition of archaeological pottery is closely related to the raw material and the firing conditions, thus constituting a source of information both on the origin and the manufacturing technology of ceramic artefacts. The techniques used to clarify the composition of the ceramic material from the point of view of the mineralogical phases include X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and petrographic analysis. Such techniques normally require the taking of a sample from the object, thus often limiting their applicability to sherds rather than intact vessels. The present study aims to investigate the possibility of applying reflection FTIR spectroscopy in the mid- and near-IR to the non-invasive analysis of the mineralogical composition of archaeological pottery, with reference to a set of Etruscan ceramic materials from the excavation of Tarquinia (Italy). Full article

(This article belongs to the Special Issue Application of Spectrometric Analyses to Cultural Heritage)

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(Left) External reflection FTIR spectra on intact sherds and (right) transmission FTIR spectra on KBr pellets of samples: (a) 80/25 (Etrusco-geometric); (b) 274/7 (Etrusco-geometric); (c) 186/2 Etrusco-Corinthian); (d) 227/35 (Etrusco-geometric); (e) 3/612 (black-gloss); (f) 170/2 (Etrusco-Corinthian); (g) 3/73 (black-gloss); (h) 3/607 (black-gloss); (i) 199/3 (Etrusco-Corinthian). The bands due to calcite, quartz and the silicates anorthite and diopside are highlighted in blue, light red and green, respectively. The part of the spectra where the combination band of calcite at 2504 cm−1 is found (left box) has been expanded in intensity by a factor of 2. Note: transmission FTIR spectra were not available for samples 274/7 and 3/612. Full article ">Figure 2
(Left) External reflection FTIR spectra on intact sherds and (right) diffuse reflectance spectra on powdered ceramic in the NIR region of samples: (a) 80/25 (Etrusco-geometric); (b) 274/7 (Etrusco-geometric); (c) 227/35 (Etrusco-geometric); (d) 186/2 Etrusco-Corinthian); (e) 3/612 (black-gloss); (f) 3/73 (black-gloss); (g) 3/607 (black-gloss); (h) 170/2 (Etrusco-Corinthian); (i) 199/3 (Etrusco-Corinthian). Note: the diffuse reflectance NIR spectrum was not available for sample 3/612. Full article ">Figure 3
(Top) External reflection FTIR spectra on intact sherds and (bottom) transmission FTIR spectra on KBr pellets of locally produced bucchero samples (a) 12/163, (b) 845/2, (c) 437/122, (d) 125/22, (e) 779/1, and of imported bucchero samples (f) 197/6, (g) 763/1, (h) 681/49, (i) 663/2, (j) Ac10/23. Full article ">

26 pages, 13959 KiB

Open AccessArticle

Two-Stage Superimposed Gold Mineralization in the Xiejiagou Gold Deposit, Shandong Province: Insights from Fluid Inclusions, H-O-S Isotopes, and Trace Elements

by Ze-Zhong Du, Zhi-Zhong Cheng, Xiao-Feng Yao and Xing-Long Bao

Minerals 2023, 13(9), 1210; https://doi.org/10.3390/min13091210 - 15 Sep 2023

Cited by 1 | Viewed by 1309

Abstract

The Xiejiagou gold deposit located in the Zhaoyuan-Laizhou gold belt is composed of altered-rock-type gold mineralization and superposed auriferous quartz veins, showing unique two-stage gold mineralization. Oxygen and hydrogen isotopic analyses yielded the following results: δ¹⁸O_H2O = 0.8‰ to 4.4‰ [...] Read more.

The Xiejiagou gold deposit located in the Zhaoyuan-Laizhou gold belt is composed of altered-rock-type gold mineralization and superposed auriferous quartz veins, showing unique two-stage gold mineralization. Oxygen and hydrogen isotopic analyses yielded the following results: δ¹⁸O_H2O = 0.8‰ to 4.4‰ and δD = −106‰ to −85‰ for altered-rock-type mineralization, and δ¹⁸O_H2O = 3.6‰ to 5.6‰ and δD = −98‰ to −89‰ for auriferous quartz-veins. Combined studies on Co/Ni, Sb/Bi and As/Ag ratios of pyrites, it can be inferred that the ore-forming fluids were dominated by magmatic water mixed with very little meteoric water. The fractured altered rocks in the ore-hosting fault zones are characterized by mylonitization, cataclastic lithification, and structural lenses, reflecting a compressional (closed) ore-forming system. In contrast, the occurrence of auriferous quartz veins in fissures of altered-rock-type orebodies and the fact that altered-rock-type ores commonly occur as breccias cemented by auriferous quartz veins that reflect an extensional (open) ore-forming system for the vein mineralization. The increase in δ³⁴S values from stage I (5.8‰–7.2‰) to stage II (6.6‰–9.0‰) indicate that the altered-rock-type mineralization was the result of intense water–rock interaction, while the occurrence of immiscible inclusions in auriferous quartz veins demonstrates that fluid immiscibility contributes significantly to gold deposition in the vein-type mineralization. Fluid-inclusion microthermometric data indicate that the fluids for the altered-rock-type mineralization are characterized by moderate-to-high temperature (262–368 °C), and low-to-moderate salinity (4.3–10.8 wt.% NaCl equivalent). In contrast, halite-bearing inclusions are found in auriferous quartz veins, and its fluids are characterized by moderate-to-high temperature (290–376 °C) and moderate-to-high salinity (5.1–41.9 wt.% NaCl equivalent). From early stages (I and II) to the late stage (III), homogenization temperature and high temperature element (W, Sn, and Mo) concentrations in pyrite first decrease and then increase, δ³⁴S values and metallization-related element (Au, Ag, and Bi) concentrations in pyrite first increase and then decrease. Therefore, it can be inferred that the two distinct types of gold mineralization in the Xiejiagou gold deposit may be two separate mineralization events. The presence of magnetite in the auriferous veins suggests an increase in oxidation state during the vein mineralization. Importantly, the Xiejiagou gold deposit preserves two types of mineralization in a single deposit and uniquely records a metallogenic transition from a compressional, reduced environment to an extensional, oxidized environment, as a result of a regional stress field transition that occurred in the Zhaoyuan-Laizhou gold belt at ca. 120 Ma. Full article

(This article belongs to the Special Issue Genesis of the Gold Deposits: News from Geology, Fluid Inclusions and Isotopes)

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13 pages, 2755 KiB

Open AccessArticle

Particle Swarm Optimization (PSO) of High-Quality Magnetic Data of the Obudu Basement Complex, Nigeria

by Stephen E. Ekwok, Ahmed M. Eldosouky, Khalid S. Essa, Anthony M. George, Kamal Abdelrahman, Mohammed S. Fnais, Peter Andráš, Emmanuel I. Akaerue and Anthony E. Akpan

Minerals 2023, 13(9), 1209; https://doi.org/10.3390/min13091209 - 14 Sep 2023

Cited by 12 | Viewed by 1173

Abstract

The particle swamp optimization procedure was applied to high-quality magnetic data acquired from the Precambrian Obudu basement complex in Nigeria with the object of estimating the distinctive body parameters (depth (z), index angle (θ), amplitude coefficient (K), shape factor (Sf), and location of [...] Read more.

The particle swamp optimization procedure was applied to high-quality magnetic data acquired from the Precambrian Obudu basement complex in Nigeria with the object of estimating the distinctive body parameters (depth (z), index angle (θ), amplitude coefficient (K), shape factor (Sf), and location of the origin (x₀)) of magnetic models. The magnetic models were obtained from four profiles that ran perpendicular to the observed magnetic anomalies within the study area. Profile A–A’ with a length of 2600 m is characterized by inverted model parameters of K = 315.67 nT, z = 425.34 m, θ = 43°, Sf = 1.15, and x₀ = 1554.86 m, while profile B–B’ with a length of 5600 m is described by K = 257.71 nT, z = 543.75 m, θ = 54°, Sf = 0.96, and x₀ = 3645.42 m model parameters. Similarly, profile C–C’ with a length of 3000 m is defined by K = 189.53 nT, z = 560.87 m, θ = 48, Sf = 1.2, and x₀ = 1950 m. Profile D–D’, which is well-defined by a 2500 m length, started at the crest of the observed magnetic anomaly and displays inverted model parameters of 247.23 nT, 394.16 m, 39°, 1.26, and 165.41 m. Correlatively, the estimated shape factor of the four models (Sf = 1.15, 0.96, 1.2, and 1.26) shows that the magnetic models are linked to thin sheets. Furthermore, quantitative interpretations of the models show that the PSO operation is rapid and proficient. Full article

(This article belongs to the Special Issue Application of Geophysical Data Interpretation in Geological and Mineral Potential Mapping)

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12 pages, 2692 KiB

Open AccessArticle

Quartz Fine Particle Processing: Hydrophobic Aggregation by Shear Flocculation

by Francielle Nogueira, Karine Rodrigues, Carlos Pereira, André Carlos Silva, Elenice M. Schons Silva, Asghar Azizi and Ahmad Hassanzadeh

Minerals 2023, 13(9), 1208; https://doi.org/10.3390/min13091208 - 14 Sep 2023

Viewed by 1399

Abstract

This study investigates the hydrophobic aggregation of fine quartz particles through shear flocculation induced by dodecylamine in aqueous solutions. The effect of stirring speed, collector concentration, flocculation time, and pH were investigated. The results showed that the impact of stirring speed on particle [...] Read more.

This study investigates the hydrophobic aggregation of fine quartz particles through shear flocculation induced by dodecylamine in aqueous solutions. The effect of stirring speed, collector concentration, flocculation time, and pH were investigated. The results showed that the impact of stirring speed on particle aggregation in the absence of a collector is very limited. Quantitative analyses demonstrated that the variation of collector concentration intensified the flocculation process more than the stirring rate. Numerical optimization showed that the large volume occupied by the flocs was 12.3 mL, achieved with a stirring speed of 2135 rpm and dodecylamine concentration of 1.39 × 10⁻² mol·L⁻¹. The highest quartz particle aggregation was observed at pH 10.5, corroborating the importance of the non-dissociated amine molecules for particle hydrophobization. High zeta potential values did not result in reducing aggregation, indicating that hydrophobicity was the governing factor in the shear flocculation process. Full article

(This article belongs to the Special Issue Recent Advances in Flotation Process)

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Schematic representation of shear flocculation. Full article ">Figure 2
Particle size distribution of quartz sample. Full article ">Figure 3
Zeta potential measurements for the quartz particles in the absence (NaCl −10−3 mol·L−1) and presence of DDA (at 1 × 10−3 mol·L−1) as a function of the solution pH. Full article ">Figure 4
Influence of the stirring speed and DDA dosage on the floc volume in the Imhoff cone at pH 10.5: (a) contour plot; and (b) response surface. Full article ">Figure 5
Influence of the stirring speed and sedimentation time on the DoA for the quartz particles with DDA at 10−3 mol·L−1 and pH 10.5: (a) Contour plot; (b) Response surface. Full article ">Figure 6
The volume of sedimented quartz flocs as a function of conditioning time [min] using DDA at 1 × 10−3 mol·L−1, pH 10.5, and 2000 rpm stirring speed. Full article ">Figure 7
Sedimented quartz flocs volume as a function of the solution pH, in the presence of DDA (at 1 × 10−3 mol·L−1), both with and without stirring at 2000 rpm. Full article ">

26 pages, 53372 KiB

Open AccessArticle

The Impacts of Molybdenum Exploration on Cd and Zn Contents in Surface Water: Evidence from a Molybdenum Mine in the Xiaoqinling Mountains

by Min Yang, Weishun Fu, Huaqing Chen, Xin Zhang, Aning Zhao and Youning Xu

Minerals 2023, 13(9), 1207; https://doi.org/10.3390/min13091207 - 13 Sep 2023

Viewed by 1245

Abstract

In order to study the impact of molybdenum ore development in a large molybdenum mining area in the Xiaoqinling Mountains on the water and sediment quality of the Wenyu stream, surface water, sediment, and surrounding rock samples were collected, and the Cd and [...] Read more.

In order to study the impact of molybdenum ore development in a large molybdenum mining area in the Xiaoqinling Mountains on the water and sediment quality of the Wenyu stream, surface water, sediment, and surrounding rock samples were collected, and the Cd and Zn contents were analyzed. The pollution status and ecological risk degree of river water and sediment samples in the Wenyu stream watershed were evaluated using the single element pollution index method, geoaccumulation index method, Hakanson potential ecological risk assessment method, potentially toxic elements (PTEs) health risk assessment, and PTEs pollution comprehensive index method. Finally, the impact of mining development on the contents of Cd and Zn in the Wenyu stream were discussed, and the sources of pollution were identified. The study revealed that the levels of Cd and Zn in 23 water samples collected from the primary channel of the Wenyu stream were markedly higher compared to the unaffected contrast area. Similarly, the concentrations of Cd and Zn in the 17 sediment samples were significantly elevated compared to the average values in the reference area. These findings indicated that The Wenyu stream was heavily impacted by the molybdenum mining activities, resulting in a high ecological risk associated with the sediment in the primary channel. Acid mine drainage in the mining area, sediment release activities, and atmospheric dust fall are considered to be the main sources of PTEs polluting the Wenyu stream watershed. Relevant personnel should complete a thorough river water quality investigation and perform ecological environment restoration so as to ensure sustainable economic development. Full article

(This article belongs to the Special Issue Environmental Impact of Mining: Soil and Water Contamination)

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16 pages, 9097 KiB

Open AccessArticle

Petrogenesis of Late Cretaceous Muscovite-Bearing Peraluminous Granites in the Youjiang Basin, South China Block: Implications for Tin Mineralization

by Ping Li, Xijun Liu and Lei Liu

Minerals 2023, 13(9), 1206; https://doi.org/10.3390/min13091206 - 13 Sep 2023

Viewed by 1306

Abstract

Most primary Sn deposits worldwide are associated with muscovite-bearing peraluminous granites, commonly believed to originate from the partial melting of metasedimentary rocks. We studied the whole-rock geochemistry and Sm–Nd isotopes of Late Cretaceous (~90 Ma) Laojunshan muscovite-bearing peraluminous granites in the Youjiang Basin, [...] Read more.

Most primary Sn deposits worldwide are associated with muscovite-bearing peraluminous granites, commonly believed to originate from the partial melting of metasedimentary rocks. We studied the whole-rock geochemistry and Sm–Nd isotopes of Late Cretaceous (~90 Ma) Laojunshan muscovite-bearing peraluminous granites in the Youjiang Basin, South China Block. The globally significant Dulong tin mineralization was co-genetic with the Laojunshan muscovite-bearing monzogranites. The Laojunshan granites exhibit slightly higher εNd(t) values than the Precambrian basement, indicating a hybrid crustal source comprising both Precambrian rock and juvenile components. Characterized by weakly peraluminous compositions, these granites display highly evolved geochemical features: notably low levels of Ca, P, Mg, Fe, and Ti contents, elevated Si content, a high FeO^T/MgO ratio, and a low Zr/Hf ratio. These distinctive geochemical features can be attributed to the differentiation of plagioclase, biotite, and zircons, with the remarkably low Nb/Ta and K/Rb ratios further suggesting a fluid exsolution process. The geochemical data propose that tin-enriched Laojunshan granites originate from mineral differentiation and fluid exsolution of crust-derived melts during magmatic evolution. By integrating these novel findings with existing data on coeval muscovite-bearing granites co-genetic with tin mineralization in the Youjiang Basin, it is deduced that these granites share a unified origin. Their genesis can be attributed to mineral differentiation and fluid exsolution of crust-derived melts rather than a direct melting of metasedimentary rocks. Full article

(This article belongs to the Special Issue Petrogenesis, Geochronology, Mineralization and Geochemistry of Granite Rocks)

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22 pages, 15962 KiB

Open AccessArticle

Metallogenic Prediction of the Zaozigou Gold Deposit Using 3D Geological and Geochemical Modeling

by Cheng Li, Bingli Liu, Keyan Xiao, Yunhui Kong, Lu Wang, Rui Tang, Miao Xie and Yixiao Wu

Minerals 2023, 13(9), 1205; https://doi.org/10.3390/min13091205 - 13 Sep 2023

Cited by 2 | Viewed by 1494

Abstract

Deep-seated mineralization prediction is an important scientific problem in the area of mineral resources exploration. The 3D metallogenic information extraction of geology and geochemistry can be of great help. This study uses 3D modeling technology to intuitively depict the spatial distribution of orebodies, [...] Read more.

Deep-seated mineralization prediction is an important scientific problem in the area of mineral resources exploration. The 3D metallogenic information extraction of geology and geochemistry can be of great help. This study uses 3D modeling technology to intuitively depict the spatial distribution of orebodies, fractures, and intrusive rocks. In particular, the geochemical models of 12 elements are established for geochemical metallogenic information extraction. Subsequently, the front halo element association of As-Sb-Hg, the near-ore halo element association of Au-Ag-Cu-Pb-Zn, and the tail halo element association of W-Mo-Bi are identified. Upon this foundation, the 3D convolutional neural network model is built and used for deep-seated mineralization prediction, which expresses a high performance (AUC = 0.99). Associated with the metallogenic regularity, two mineral exploration targets are delineated, which might be able to serve as beneficial achievements for deep exploration in the Zaozigou gold deposit. Full article

(This article belongs to the Special Issue Advances in 3D Geological Modeling and Metallogenic Prediction)

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