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Minerals
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Mineralogical and Geochemical Characteristics of Chromitites
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Mineralogical and Geochemical Characteristics of Chromitites

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

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 4893

Special Issue Editors

Dr. Fahui Xiong

E-Mail Website
Guest Editor
1. Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
2. Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Minerals, Shandong University of Science and Technology, Qingdao 266590, China
Interests: ophiolite; mantle peridotite; chromitite; minerals; inclusions
Dr. Xiaohan Gong

E-Mail Website
Guest Editor
School of Ocean Sciences, China University of Geosciences (Beijing) , Beijing 100083, China
Interests: ophiolite; chromitite; evolution of oceanic lithosphere; mantle geochemistry; subduction processes and dynamics

Special Issue Information

Dear Colleagues,

Chromium is an irreplaceable element of industrial raw materials, especially for the production of alloys and refractory materials. Chromitite deposits, hosted in ultramafic intrusions and in ophiolite, are the main sources of chromium in Nature. They have provided valuable information on various mantle processes, including melt–mantle reaction, deep-seated magmatic evolution, and mantle dynamics. Especially, the genesis of podiform chromitites has become confused, and must be re-established by incorporating the genesis of UHP minerals hosted in chromitites. Therefore, studies on the ore-forming process, characteristics, and mechanism of podiform chromitites are popular for geologists. However, two main kinds of chromitites may have similar characteristics (e.g., silicate inclusions). This Special Issue covers the topics of the mineral and/or geochemistry, geochronology, petrogenesis, and metallogenic mechanisms of stratiform and podiform chromitites. In particular, comparative studies are welcome. We also welcome contributions on the applications of new methods and/or techniques (e.g., for non-traditional stable isotopes, in-situ mineral dating, isotopes of chromitites). This Special Issue aims to provide a further understanding of the genesis of these two kinds of chromitite.

Dr. Fahui Xiong
Dr. Xiaohan Gong
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • chromitites
  • geochemistry
  • petrogenesis
  • inclusions

Published Papers (4 papers)

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Research

20 pages, 7915 KiB  
Article
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
Viewed by 894
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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22 pages, 8108 KiB  
Article
Geochemistry and Mineralogy of Peridotites and Chromitites from Zhaheba Ophiolite Complex, Eastern Junggar, NW China: Implications for the Tectonic Environment and Genesis
by Zhaolin Wang, Jiayong Yan, Hejun Tang, Yandong Xiao, Zhen Deng, Guixiang Meng, Hui Sun, Yaogang Qi and Lulu Yuan
Minerals 2023, 13(8), 1074; https://doi.org/10.3390/min13081074 - 13 Aug 2023
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Abstract
The Zhaheba ophiolite is an ocean relic of the Zhaheba-Aermantai oceanic slab, a branch of the early Paleozoic Paleo-Asian Ocean. The peridotites consist mainly of harzburgite, lherzolite and minor dunite, chromitite. This study describes the whole-rock geochemistry and mineral chemistry of the Zhaheba [...] Read more.
The Zhaheba ophiolite is an ocean relic of the Zhaheba-Aermantai oceanic slab, a branch of the early Paleozoic Paleo-Asian Ocean. The peridotites consist mainly of harzburgite, lherzolite and minor dunite, chromitite. This study describes the whole-rock geochemistry and mineral chemistry of the Zhaheba peridotite and chromitite for the purpose of constraining their tectonic environment and genesis. The major oxides and the trace element concentrations of the peridotites are comparable with abyssal peridotite, but fall outside the field of SSZ (suprasubduction zone) peridotite and the fore-arc peridotite. The massive chromites belong to the high-Cr group, with an average Cr# (Cr/(Cr + Al)) atomic ratio) value of chromian spinel of 0.77, whereas the average Mg# value is 0.60. The disseminated chromites give a lower concentration of Cr2O3 (38.96–42.15 wt.%, average 40.35 wt.%) and lower Cr# values (0.50–0.56, average 0.53), but slightly higher contents of MgO (13.23 wt.%) and Mg# (0.61) than the massive chromites. In the diagrams of Cr#-Mg#, NiO-Cr# and TiO2-Cr#, the massive chromites fall in the field of boninite, and the disseminated chromite in the peridotite plot fall in the field of abyssal peridotite and mid-oceanic ridge basalt (MORB). The massive chromitites, with high-Cr, display a boninite affinity, whereas the disseminated chromite plot in the high-Al and abyssal peridotite type field may be generated by the extension of the Zhaheba ocean in the MOR environment then experienced deep subduction and exhumation. The calculated degrees of partial melting for the massive chromites are 21%−22%, and for the disseminated chromites in peridotites the degrees are 17%−18%. The calculated values of fO2 for the massive chromites range from −1.44 to +0.20, and the values for the disseminated chromites range from −0.32 to +0.18. The inferred parental melt composition for massive chromitite falls in the field of boninite in an arc setting, whereas the disseminated chromite in peridotites are in the field of a MORB setting. This indicates that the parental magmas of the former were more refractory than the latter. A two-stage evolution model for the chromites was proposed, in which disseminated chromites were first formed in an MOR environment and then modified by later-stage melts and fluids, and formed massive chromites were formed in an SSZ setting during intra-oceanic subduction. Full article
(This article belongs to the Special Issue Mineralogical and Geochemical Characteristics of Chromitites)
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17 pages, 8925 KiB  
Article
Petrogenesis and Geochronology of the Shazuoquan Ophiolite, Beishan Orogenic Belt: Constraints on the Evolution of the Beishan Ocean
by Yong Meng, Xin Zhang, Jianke Bai, Kai Wang, Yaogang Qi, Haibo Zhao and Yuan Han
Minerals 2023, 13(8), 1067; https://doi.org/10.3390/min13081067 - 11 Aug 2023
Viewed by 893
Abstract
The ophiolites in the Beishan Orogenic Belt provide important information about the evolution of the Beishan Ocean in the Paleozoic Era. We studied ophiolite petrology, geochemistry and isotopic chronology. The Shazouquan ophiolites consist of dunites, wehrlites, gabbros and anorthosites. Ophiolitic mélange belts are [...] Read more.
The ophiolites in the Beishan Orogenic Belt provide important information about the evolution of the Beishan Ocean in the Paleozoic Era. We studied ophiolite petrology, geochemistry and isotopic chronology. The Shazouquan ophiolites consist of dunites, wehrlites, gabbros and anorthosites. Ophiolitic mélange belts are composed of matrixes and blocks, and different rocks are fault-bounded. Dunites and wehrlites are high in Mg#, Cr# and MgO, low in TiO2, relatively depleted in large-ion lithophile elements (Ti and P) and enriched in high-strength elements (U, Zr and Hf). They have a total REE of 1.25 × 10–6−5.39 × 10−6 and δEu of 1.12–3.54, which are similar to those of SSZ-type ophiolites, indicating that their parent magma source region may be a weakly depleted mantle source region. The anorthosite and gabbro are high in Al2O3, MgO and Mg#, low in TiO2, enriched in large-ion lithophile elements (Rb and Sr), and depleted in high-strength elements (Nb, Ta and Ti), but enriched in Zr and Hf. They have similar geochemical signatures to those of arc magmatic rocks. They are derived from the mantle peridotite formed against the tectonic background of subduction and modified by the fluid materials in the subduction zone. We collected anorthosite and gabbro, which were produced as ophiolite for U-Pb dating. The anorthosite yields a zircon U-Pb, aged 394 ± 11 Ma (MSWD = 0.84), and a gabbro zircon U-Pb, aged 466 ± 12 Ma (MSWD = 3.2), indicating that the Shazouquan ophiolite was formed in the Middle Ordovician–Early Devonian eras. Combining the above evidence, we conclude that the Beishan Ocean was in a subduction tectonic background from the Middle Ordovician to Early Devonian periods. Full article
(This article belongs to the Special Issue Mineralogical and Geochemical Characteristics of Chromitites)
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22 pages, 8372 KiB  
Article
Accessory Minerals in the Chromitite Ores of Dzharlybutak Ore Group of Kempirsai Massif (Southern Urals, Kazakhstan): Clues for Ore Genesis
by Dmitry E. Saveliev, Darkhan K. Makatov, Andrey V. Vishnevskiy and Ruslan A. Gataullin
Minerals 2023, 13(2), 263; https://doi.org/10.3390/min13020263 - 13 Feb 2023
Cited by 1 | Viewed by 1421
Abstract
The paper provides results of a detailed mineralogical study of some chromitite ores from two deposits in the Southern Urals of Kazakhstan: Almaz-Zhemchuzhina and Geofizicheskoe-VII. It is revealed that the main ore minerals are Cr-spinel with high Cr# (Cr/(Cr + Al) = 0.8–0.83), [...] Read more.
The paper provides results of a detailed mineralogical study of some chromitite ores from two deposits in the Southern Urals of Kazakhstan: Almaz-Zhemchuzhina and Geofizicheskoe-VII. It is revealed that the main ore minerals are Cr-spinel with high Cr# (Cr/(Cr + Al) = 0.8–0.83), as well as serpentine and chlorite, replacing primary olivine. Chromium spinel grains contain mineral inclusions, which are distributed rather unevenly. The most common mineral inclusions are olivine (serpentine) and amphibole; phlogopite, pyroxenes, and base metal sulfides are rare. Olivine from inclusions in chromite is the highest in magnesium (Fo97–98), and is anomalously high in nickel (up to 1.8 wt.% NiO). The closure of exchange reactions between olivine and chromite occurred in the temperature range of 700–850 °C and in the oxygen fugacity range of −1.04 … +2.8 ΔFMQ, which most likely corresponds to the upper mantle settings of the fore-arc basin. A few tens of monomineral grains and polymineral intergrowths of platinum group minerals (PGMs) were found in chromite aggregates. Notably, monomineral grains are mainly represented by Ru, Os, and Ir disulfides, while in polymineral inclusions, iridium prevails (with widespread native phases, sulfides, and sulfoarsenides). PGM grains included in chromite are often associated with hydrous silicates: amphibole, and less often with phlogopite or chlorite. Discussed in the paper is the possible genesis of ores and inclusions. As a preliminary conclusion, we suggest that the solid-phase processes played the most significant role in the crystallization of Cr-spinel in the investigated chromitite ores. Full article
(This article belongs to the Special Issue Mineralogical and Geochemical Characteristics of Chromitites)
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