Subjects -> MINES AND MINING INDUSTRY (Total: 82 journals)
Showing 1 - 42 of 42 Journals sorted alphabetically
Applied Earth Science : Transactions of the Institutions of Mining and Metallurgy     Hybrid Journal   (Followers: 4)
Archives of Mining Sciences     Open Access   (Followers: 1)
BHM Berg- und Hüttenmännische Monatshefte     Hybrid Journal   (Followers: 1)
Canadian Mineralogist     Full-text available via subscription   (Followers: 5)
CIM Journal     Hybrid Journal  
Clay Minerals     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 11)
Environmental Geochemistry and Health     Hybrid Journal   (Followers: 2)
European Journal of Mineralogy     Hybrid Journal   (Followers: 12)
Extractive Industries and Society     Hybrid Journal   (Followers: 2)
Gems & Gemology     Full-text available via subscription   (Followers: 1)
Geology of Ore Deposits     Hybrid Journal   (Followers: 3)
Geomaterials     Open Access   (Followers: 2)
Geotechnical and Geological Engineering     Hybrid Journal   (Followers: 8)
Ghana Mining Journal     Full-text available via subscription   (Followers: 3)
Gold Bulletin     Hybrid Journal  
International Journal of Coal Geology     Hybrid Journal   (Followers: 2)
International Journal of Coal Preparation and Utilization     Hybrid Journal   (Followers: 1)
International Journal of Coal Science & Technology     Open Access   (Followers: 1)
International Journal of Hospitality & Tourism Administration     Hybrid Journal   (Followers: 14)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 8)
International Journal of Mining and Geo-Engineering     Open Access  
International Journal of Mining and Mineral Engineering     Hybrid Journal   (Followers: 5)
International Journal of Mining Engineering and Mineral Processing     Open Access   (Followers: 5)
International Journal of Mining Science and Technology     Open Access   (Followers: 4)
International Journal of Mining, Reclamation and Environment     Hybrid Journal   (Followers: 4)
International Journal of Rock Mechanics and Mining Sciences     Hybrid Journal   (Followers: 6)
Journal of Analytical and Numerical Methods in Mining Engineering     Open Access  
Journal of Applied Geophysics     Hybrid Journal   (Followers: 15)
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of China Coal Society     Open Access  
Journal of Convention & Event Tourism     Hybrid Journal   (Followers: 4)
Journal of Geology and Mining Research     Open Access   (Followers: 11)
Journal of Human Resources in Hospitality & Tourism     Hybrid Journal   (Followers: 8)
Journal of Materials Research and Technology     Open Access   (Followers: 2)
Journal of Metamorphic Geology     Hybrid Journal   (Followers: 15)
Journal of Mining Institute     Open Access  
Journal of Mining Science     Hybrid Journal   (Followers: 2)
Journal of Quality Assurance in Hospitality & Tourism     Hybrid Journal   (Followers: 5)
Journal of Sustainable Mining     Open Access   (Followers: 2)
Journal of the Southern African Institute of Mining and Metallurgy     Open Access   (Followers: 5)
Lithology and Mineral Resources     Hybrid Journal   (Followers: 3)
Lithos     Hybrid Journal   (Followers: 9)
Mine Water and the Environment     Hybrid Journal   (Followers: 4)
Mineral Economics     Hybrid Journal  
Mineral Processing and Extractive Metallurgy : Transactions of the Institutions of Mining and Metallurgy     Hybrid Journal   (Followers: 11)
Mineral Processing and Extractive Metallurgy Review     Hybrid Journal   (Followers: 4)
Mineralium Deposita     Hybrid Journal   (Followers: 4)
Mineralogia     Open Access   (Followers: 2)
Mineralogical Magazine     Hybrid Journal   (Followers: 1)
Mineralogy and Petrology     Hybrid Journal   (Followers: 2)
Minerals     Open Access  
Minerals & Energy - Raw Materials Report     Hybrid Journal  
Minerals Engineering     Hybrid Journal   (Followers: 9)
Mining Engineering     Full-text available via subscription   (Followers: 5)
Mining Journal     Full-text available via subscription   (Followers: 3)
Mining Report     Hybrid Journal   (Followers: 2)
Mining Technology : Transactions of the Institutions of Mining and Metallurgy     Hybrid Journal   (Followers: 2)
Mining, Metallurgy & Exploration     Hybrid Journal  
Natural Resources & Engineering     Hybrid Journal  
Natural Resources Research     Hybrid Journal   (Followers: 8)
Neues Jahrbuch für Mineralogie - Abhandlungen     Full-text available via subscription   (Followers: 1)
Physics and Chemistry of Minerals     Hybrid Journal   (Followers: 4)
Podzemni Radovi     Open Access  
Rangeland Journal     Hybrid Journal   (Followers: 1)
Réalités industrielles     Full-text available via subscription  
Resources Policy     Hybrid Journal   (Followers: 4)
Reviews in Mineralogy and Geochemistry     Hybrid Journal   (Followers: 4)
Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica     Open Access  
Rock Mechanics and Rock Engineering     Hybrid Journal   (Followers: 6)
Rocks & Minerals     Hybrid Journal   (Followers: 2)
Rudarsko-geološko-naftni Zbornik     Open Access  
Stainless Steel World     Full-text available via subscription   (Followers: 17)
Transactions of Nonferrous Metals Society of China     Hybrid Journal   (Followers: 9)
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Mineralogy and Petrology
Journal Prestige (SJR): 0.833
Citation Impact (citeScore): 2
Number of Followers: 2  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1438-1168 - ISSN (Online) 0930-0708
Published by Springer-Verlag Homepage  [2469 journals]
  • Orthopyroxene megacrysts from the Chilka Lake anorthosite massif, Eastern
           Ghats, India: a clue to magmatic evolution

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      Abstract: Abstract The present study reports the occurrence of orthopyroxene megacrysts from the Chilka Lake anorthosite massif, Eastern Ghats, India. An insight into the mineral chemistry of different phases, coupled with detailed field and petrographic evidences from this study, shed light on a long debate on the origin of orthopyroxene megacrysts in anorthosite massifs. The megacrysts contain exsolved lamellae of plagioclase and opaque oxides (ilmenite, rutile) oriented along orthopyroxene cleavage planes. The trace element distribution patterns of the megacryst and matrix plagioclase are mirror reflections of each other and mutually complementary. The calculated compositions of melts in equilibrium with these two phases show comparable patterns for LREE (light rare earth elements, La–Sm), but differ markedly in terms of HREE (heavy rare earth elements, Eu–Lu), suggesting that the megacrysts and matrix plagioclases did not crystallize simultaneously. We infer that the orthopyroxene megacrysts have a longer crystallization history, initially as a low-Ca non-quad member of the pyroxene group at pressure ≥ 10 kbar, incorporating some amount of Ca, Al and Ti in their structure. Subsequently, they have been carried by a plagioclase crystal mush to mid-crustal levels at pressure ~ 4–6 kbar following a near-isothermal decompression that may be linked to the emplacement of the anorthosite massif, giving rise to the exsolution lamellae of plagioclase and opaque oxides.
      PubDate: 2022-05-23
       
  • Geochemistry of granitoids from the Austroalpine Seckau Complex: a key for
           revealing the pre-Alpine evolution of the Eastern Alps

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      Abstract: Abstract Recent studies revealed that the calc-alkaline metagranitoids of the Seckau Complex comprise both (1) a Late Cambrian to Early Ordovician and (2) a Late Devonian to Early Carboniferous (early Variscan) intrusive complex. The older rocks of the Hochreichart Plutonic Suite reflect I to S-type affinity and are peraluminous and characterized by a general decrease in TiO2, Al2O3, MgO, CaO, P2O5, FeOt and MnO with increasing SiO2. Chondrite-normalized rare earth element (REE) plots display a slight enrichment in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) as well as negative Eu anomalies ((Eu/Eu*)N = 0.15- 0.77). The whole-rock initial 87Sr/86Sr ratios calculated back to the time of emplacement (~ 496 Ma) vary between 0.7056 to 0.7061. The early Variscan rocks of the Hintertal Plutonic Suite can be subdivided into (a) the meta- to peraluminous granodioritic suite of the Pletzen Pluton and (b) the peraluminous granitic suite of the Griessstein Pluton. The Pletzen Pluton shows typical magmatic fractionation trends for most of the major oxides and trace elements plotted against SiO2. On a chondrite-normalized diagram, metagranitoids are strongly enriched in LREE and show no significant negative Eu anomaly. Metagranitoids of the Griessstein Pluton have a more peraluminous character and similar major and trace element fractionation trends compared to the Pletzen Pluton. However, the contents in SiO2, major and trace elements clearly point towards a more evolved melt with generally lower TiO2, Al2O3, MgO and CaO values and higher K2O content. Metagranitoids of the Griessstein Pluton are additionally characterized by a slight negative Eu anomaly of about 0.81 on a chondrite-normalized REE plot. Initial 87Sr/86Sr values calculated back to the time of emplacement (~ 353 Ma) of the Pletzen Pluton and the Griessstein Pluton vary between 0.7051—0.7061 and 0.7054—0.7063, respectively, and suggest the same magmatic source for both units. Application of rhyolite-MELTS modelling to the Hintertal Plutonic Suite revealed that the Griessstein Pluton formed by fractional crystallization (~ 30%) from the more primitive Pletzen Pluton. Our geochemical data from the Hochreichart Suite granitoids suggest the existence of a Late Cambrian to Early Ordovician active margin with its remnants now exposed in the Seckau Complex. The early Variscan grainitoids of the Seckau Complex are inferred as part of a magmatic arc along the southern Bohemian active continental margin that was related to the subduction of differently termed oceanic domains (Galicia-Moldanubian Ocean or Paleotethys), prior to the final collision of Gondwana and Laurussia. The general paleogeographic position of the Seckau Complex during the Variscan orogeny is considered to be south to southeast of the Bohemian Massif, adjacent to the eastern Hohe Tauern, the Schladming Tauern, and the Western Carpathians.
      PubDate: 2022-05-19
       
  • Early Cretaceous ultramafic-alkaline-carbonatite magmatism in the Shillong
           Plateau-Mikir Hills, northeastern India – a synthesis

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      Abstract: Abstract A comprehensive mineralogical, geochemical and isotopic review of six ultramafic-alkaline-carbonatite magmatic intrusions of the Shillong Plateau (Sung Valley, Jasra, Swangkre-Rongjeng, and Mawpyut) and Mikir Hills (Samchampi-Samteran and Barpung) is presented here, using the published data. These intrusions emplaced ca. 115–102 Ma ago, thus are significantly younger than the tholeiitic flood basalts erupted in Rajmahal-Sylhet province (ca. 118–115 Ma). The intrusive lithologies vary from ultramafic (dunites, clinopyroxenites, melilitolites) to mafic (ijolites, gabbros sensu lato, shonkinites), to felsic (syenites, nepheline syenites) and carbonatites (mostly calcite-rich varieties). The volcanic-subvolcanic facies (lamprophyres, phonolites) are not abundant. The range of chemical compositions of the magmatic phases in the various assemblages is notable; the intrusive rocks are thus the result of crystallization of magmas from variably evolved, independent liquid-lines-of descent, generally of alkaline/strongly alkaline lineages and sodic-to-potassic in affinity. The large variations of the Sr–Nd isotopic ratios of the silicate intrusive rocks (sensu lato) suggest a role of shallow-level crustal contamination during their formation. The carbonatites of the Sung Valley and Samchampi-Samteran have different isotope ratios than the associated silicate rocks, have some isotopic affinity with the Group I tholeiitic basalts of Rajmahal Traps and have an ultimate genesis in a carbonate-bearing lithospheric mantle.
      PubDate: 2022-04-05
       
  • Estimation of Li and OH contents in (Li,Al)-bearing tourmalines from Raman
           spectra

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      Abstract: Abstract Six Al- and Li-bearing tourmaline crystals from pegmatites were structurally and chemically characterized. These samples can be assigned to elbaite, fluor-elbaite and rossmanite. Quantitative analyses of light elements such as Li, B and H are not always easily accessible. Therefore a method for the calculation of Li and OH would be of a general interest for the Geosciences. In the present work we test whether relatively accurate Li and OH estimations are possible based on the deconvolution of the O–H stretching vibration modes in a Raman spectrum on common (Al, Li)-rich tourmalines. We use the short-range arrangement model in our band interpretation as this model, in contrast to other models, provides the ability to evaluate an additional parameter by analyzing the OH stretching modes that can be used in the formula calculation process, which ultimately leads to the estimation of Li and OH with high accuracy. We also compare microprobe and Raman spectroscopy results, which we combine, with optimized data derived from microprobe and single-crystal structure refinement by using the same crystals. Based on our investigations, where the Raman spectra were recorded on non-oriented crystal sections, we conclude that we produce more accurate estimations, when the effects of the section orientation are considered. Therefore, we also propose a new method to correct the influence of the orientation of the crystal section.
      PubDate: 2022-04-04
       
  • Impact diamonds from meteorite craters and Neogene placers in Ukraine

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      Abstract: Abstract There are seven meteorite craters and several Neogene placers in the Ukrainian Shield containing impact apographitic diamond. In this work impact diamonds from the Bilylivka meteorite crater and from the Samotkan’ Neogene titanium-zirconium placer were studied in detail. The results of a comprehensive study of impact diamond crystals — morphology, microtopography, microstructure, carbon isotope composition, photoluminescence, optical, infrared, and Raman spectroscopy — are presented. The size of the impact diamonds is up to 0.5 mm. Impact diamond crystals are mostly two- or three-phase polycrystalline aggregates (diamond, lonsdaleite, graphite). They show external morphological and internal microstructural features of solid-state phase transition of graphite to diamond during impact shock metamorphism – they are paramorphoses on graphite crystals. Microstructural features of the graphite-diamond transition in the studied crystals of impact diamonds are their polysynthetic (11 \(\overline{2}\) 1) twinning and the polycrystalline structure of the twins themselves. The carbon isotopic composition of impact diamonds ranges: for Bilylivka diamonds – from –14.80 to –21.84 ‰ δ13C VPDB, with an average value of –17.21 ‰ δ13C and for Samotkan’ diamonds – from –10.35 to –23.06 ‰ δ13C VPDB, with an average value of –17.64 ‰ δ13C. The photo luminescent and spectroscopic features of the studied diamonds indicate the absence of nitrogen defects in crystals that are characteristic for mantle diamond. The location of the source rocks and potential routes how diamond have been incorporated into the Samotkan’ placer are discussed.
      PubDate: 2022-03-29
       
  • Magma hybridization and crystallization in coexisting gabbroic and
           granitic bodies in the mid-crust, Akechi district, central Japan

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      Abstract: Abstract Petrological and geochemical features of gabbros and fine-grained mafic rocks (mafic microgranular enclaves; MMEs) in the Inagawa Granite of the Ryoke Plutonic Complex were investigated to assess the interactions between coexisting mafic and silicic magmas, and the petrogenetic relationships between the MMEs and surrounding gabbros. The MMEs exhibit mingling textures that imply the coexistence of mafic and silicic magmas that did not undergo complete mixing, but the geochemical compositions of the MMEs require substantial hybridization and homogenization. The gabbroic rocks exhibit disequilibrium textures and mineral compositions, such as quartz–hornblende ocellar textures and patchy plagioclase crystals with bimodal anorthite contents. These textures and compositions record an abrupt decrease in crystallization temperature and mechanical mixing between crystallizing gabbroic mush and silicic (granitic) melt. Geochemical variations of the gabbroic rocks can be explained by hybridization and fractional crystallization (HFC) processes between crystallizing gabbroic mush and granitic melt. Extrapolation of the mixing trend to a basaltic composition suggests that the primitive mafic end-member was a low-K basaltic magma. Given that HFC yields magnesian andesite by the addition of a small amount of silicic melt to a primitive mafic end-member, the compositional modification of mafic magmas by magma mixing might be an essential process in the formation of andesitic magma in arc crust.
      PubDate: 2022-03-23
       
  • Geochemistry of rhodonite in the Luziyuan Pb − Zn skarn deposit,
           Southwestern China

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      Abstract: Abstract The Luziyuan skarn deposit is the second largest Pb − Zn deposit in the Baoshan block, Yunnan Province, Southwestern China. Rhodonite is a widespread skarn mineral in the host rock, occurring as coarse-grained crystals and veins, and is closely associated with Pb − Zn mineralization. In-situ elemental analysis of rhodonite from three levels (1220 m, 1265 m and 1495 m above sea level) by laser ablation-inductively coupled plasma-mass spectrometry and Sm − Nd isotopic dating of the rhodonite − calcite pair were conducted to constrain the compositions and the timing of Pb − Zn mineralization. The new Sm − Nd isotopic data reveal that the Luziyuan deposit formed during the Early Jurassic (183 ± 2.3 Ma; MSWD = 0.72). These chronological constraints, combined with regional tectonic evolution, suggest that the Luziyuan Pb − Zn mineralization is genetically linked to eastward subduction of the Shan Boundary Ocean beneath the Baoshan block during the Meso-Tethys period. Furthermore, all examined rhodonite samples contain relatively high concentrations of MnO (34.7 − 43.0 wt%) and Zn (536 − 2117 ppm), but generally low contents of FeO (1.07 − 6.08 wt%), Cu, Co, Ni, Ga, Mo, Sn, W and Pb. A positive correlation between Zn and MnO contents among different skarn deposits and nearly chondritic Y/Ho ratio (~ 28) in the Luziyuan rhodonite suggests that this mineral formed from magmatic fluids and its Zn enrichment was controlled by the fluid chemistry. The same data also suggest that Zn-rich rhodonite in skarns may be used as an indicator mineral for Zn exploration when combined with other geological, geophysical, and geochemical criteria.
      PubDate: 2022-03-09
      DOI: 10.1007/s00710-022-00776-0
       
  • Orthopyroxene rim growth during reaction of (Co, Ni, Mn, Zn)-doped
           forsterite and quartz: Experimental constraints on element distribution
           and grain boundary diffusion

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      Abstract: Abstract Mantle metasomatism is an important process in subduction zones in which fluids from the dehydrating oceanic slab interact with the overlying upper mantle resulting in a chemical alteration of the mantle. Consequently, this fluid-rock interaction may influence the mantle rock's physical properties such as the deformation behavior. In order to study element redistribution during mantle metasomatism in the laboratory, we used the simplified model reaction olivine + quartz = orthopyroxene, where olivine acts as representative for the upper mantle and quartz as proxy for the metasomatizing agent. We conducted piston-cylinder experiments at 1.5 GPa and 950 to 1400 °C, lasting between 48 and 288 h, on samples containing a mixture of quartz and one set of synthesized forsterite samples doped with either Co, Ni, Mn, or Zn. Additionally, we tested the influence of either nominally anhydrous or hydrous experimental conditions on the chemical distribution of the respective dopant element by using either crushable alumina or natural CaF2 as pressure medium. Results of the chemical analyses of the recovered samples show dopant specific partitioning between doped forsterite and orthopyroxene independent of the confining pressure medium; except for the runs in which Ni-doped forsterite samples were used. The observed Ni- and Co-enrichment in forsterite samples may be used to identify mantle rocks that underwent mantle metasomatism in nature.
      PubDate: 2022-02-25
      DOI: 10.1007/s00710-022-00773-3
       
  • Chevkinite-group minerals in selected intrusions of the Mazury Complex,
           North-Eastern Poland: insights into the formation of a titanite-like phase
           by hydrothermal alteration

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      Abstract: Abstract Chevkinite-group minerals forming large and common (up to 0.03 vol%) accessory phases in monzodiorites and granodiorites from the Mesoproterozoic anorthosite-mangerite-charnockite-granite (AMCG) suite intrusions, Mazury Complex, north-eastern Poland, range from pristine magmatic types to hydrothermally altered varieties. The unaltered phase is perrierite-(Ce), with the uncommon feature of having Al dominant in the C site. Hydrothermal alteration of the perrierite-(Ce) followed two main trends: one shows depletion in Ca, Fe, Si, Al and Mg, and increasing Ti contents; the other shows increases in Si, Ti and Ca and decreases in light rare-earth elements (LREE), Y and Mg, at about constant Fe content. The second trend resulted in the formation of a phase compositionally similar to titanite. Result of chemical analyses show that the transition from perrierite-(Ce) to the titanite-like phase is sharp; an electron back-scatter diffraction (EBSD) study shows the titanite- like material to be amorphous. The hydrothermal alteration of a chevkinite-group mineral to titanite has commonly been reported in natural sequences but this is the first record of the identification of a titanite-like phase made on the basis of a structural analysis.
      PubDate: 2022-01-20
      DOI: 10.1007/s00710-022-00772-4
       
  • On the incorporation of strontium into the crystal structure of bredigite:
           structural effects and phase transition

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      Abstract: Abstract Sr-substitution in the crystal structure of bredigite has been studied in detail. Samples of a hypothetical solid-solution series with nominal composition Ca7-xSrxMg[SiO4]4 (x = 0, 2, …,7) have been prepared from sinter reactions in the temperature range between 1275 and 1325 °C and characterized using powder and single-crystal X-ray diffraction. Synthesis runs between x = 1 and x = 4 resulted in compounds with increasing Sr contents, for which single-crystal diffraction studies revealed the following Sr/(Sr + Ca) atomic ratios: 0.133,0.268, 0.409 and 0.559. They are isostructural to the pure calcium end-member (x = 0) and adopt the orthorhombic space group Pnnm. Evolution of the unit-cell parameters and cell volumes of the solid-solution series are defined by linear or nearly linear trends when plotted against the Sr/(Sr + Ca) atomic ratio. Replacement of calcium with strontium atoms on the different sites shows clear preferences for specific positions. For the experiment with x = 5, formation of bredigite-related single-crystals with Sr/(Sr + Ca) = 0.675 was observed. These samples, however, exhibited a halved c lattice parameter when compared with the corresponding value in the Pnnm structure, pointing to a compositionally induced phase transition somewhere in region between Sr/(Sr + Ca) = 0.559 and 0.675. The crystal structure of this new phase with composition Ca2.32Sr4.82Mg0.86[SiO4]4 was successfully determined in space group Pbam. Basic crystallographic data are as follows: a = 18.869(2) Å, b = 6.9445(8) Å, c = 5.5426(6) Å, V = 726.28(14) Å3, Z = 2. Structure determination was accomplished using charge flipping. Subsequent least-squares refinements resulted in a residual of R( F ) = 2.70% for 822 independent reflections and 87 parameters. The Pbam- and the Pnnm-structures are in a group-subgroup relationship and topologically related. Both are based on so-called pinwheel-like MSi6O24 clusters consisting of a central magnesium-dominated [MO6]-octahedron as well as six attached [SiO4]-tetrahedra. The clusters are linked into chain-like elements running along [001]. Linkage between the chains is provided by mixed Sr/Ca positions with 6 to 10 oxygen ligands. Differences between the two phases result from changes in Sr-Ca site occupancies in combination with displacements of the atoms and tilts of the tetrahedra. The distortion pattern has been studied using group-theoretical methods including mode analysis. Notably, for the samples with x = 6 and x = 7—the latter corresponding to the hypothetical pure strontium end-member composition—no bredigite-type phases could be identified, indicating that there is an upper limit for the Sr-uptake.
      PubDate: 2021-12-03
      DOI: 10.1007/s00710-021-00771-x
       
  • Genesis of Zn-Pb-(Ba-Sr) mineralization in the peridiapiric cover of Jebel
           El Akhouat, Ech Chehid salt dome, Northern Tunisia

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      Abstract: Abstract The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted mainly in the organic matter-rich Albian and Cenomanian–Turonian rocks. The orebodies occur mainly as open-space fillings and are structurally-controlled. The paragenetic sequence consists of three stages, which reflect three ore events. Three discrete stages of Zn-Pb sulfide and/or Zn-Pb-Ba-Sr sulfide-sulfate ores are identified. Fluid inclusion study carried out on selected minerals of different stages reveals that sphalerite, galena, marcasite, celestine, barite, and fluorite precipitated as a result of mixing between a hydrothermal, saline, metal-rich basinal fluid and a low-temperature, less saline, metal-depleted, sulfur- or sulfate-rich fluid with the intermittent involvement of hydrocarbons. Based on sulfur isotope data, sulfur of sulfides was derived from the reduction of the dissolved Triassic sulfates primary through thermochemical sulfate reduction with a contribution of bacterial sulfate reduction. The Pb isotopic composition of galena samples and trace elements data of the host carbonate rocks suggest that metals were derived primarily from the Paleozoic siliciclastic rocks with a contribution of the organic matter-rich Albian and Cenomanian–Turonian rocks. The Alpine orogeny triggered the migration of the metalliferous fluids from the deep parts of the basin towards the peridiapiric paleohigh of Ech Chehid diapir through major faults towards the loci of deposition.
      PubDate: 2021-11-23
      DOI: 10.1007/s00710-021-00767-7
       
  • A simple and robust method for calculating temperatures of granitoid
           magmas

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      Abstract: Abstract Calculating the temperatures of magmas from which granitoid rocks solidify is a key task of studying their petrogenesis, but few geothermometers are satisfactory. Zircon saturation thermometry has been the most widely used because it is conceptually simple and practically convenient, and because it is based on experimental calibrations with significant correlation of the calculated zircon saturation temperature (TZr) with zirconium (Zr) content in the granitic melt (i.e., TZr ∝ ZrMELT). However, application of this thermometry to natural rocks can be misleading, resulting in the calculated TZr having no geological significance. This thermometry requires Zr content and a compound bulk compositional parameter M of the melt as input variables. As the Zr and M information of the melt is not available, petrologists simply use bulk-rock Zr content (ZrBULK-ROCK) and M to calculate TZr. In the experimental calibration, TZr shows no correlation with M, thus the calculated TZr is only a function of ZrMELT. Because granitoid rocks represent cumulates or mixtures of melt with crystals before magma solidification and because significant amount Zr in the bulk-rock sample reside in zircon crystals of varying origin (liquidus, captured or inherited crystals) with unknown modal abundance, ZrBULK-ROCK cannot be equated with ZrMELT that is unknown. Hence, the calculated magma temperatures TZr using ZrBULK-ROCK have no significance in both theory and practice. As an alternative, we propose to use the empirical equation \(T_{SiO_{2}}\)  (°C) = -14.16 × SiO2 + 1723 for granitoid studies, not to rely on exact values for individual samples but focus on the similarities and differences between samples and sample suites for comparison. This simple and robust thermometry is based on experimentally determined phase equilibria with T ∝ 1/SiO2.
      PubDate: 2021-11-22
      DOI: 10.1007/s00710-021-00769-5
       
  • The genesis of Guanting Pb–Zn deposits in the Jianshui area, Yunnan
           Province, SW China: Constraints from geochronology, S isotopes and trace
           elements

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      Abstract: Abstract The Guanting Pb–Zn deposits in the Jianshui area, southern Yunnan Province, SW China, are located in the conjunction of the Yangtze Block, Cathaysian Block and Sanjiang Block, and they belong to part of the Sichuan-Yunnan-Guizhou (SYG) Pb–Zn metallogenic province. The Pb–Zn orebodies occur in basaltic and limestone breccia at the interfaces between the Maokou limestone and Emeishan basalt. Here, we use zircon U–Pb dating, Rb–Sr dating, trace elements and S isotope data of sulfides to constrain the ages and genesis of deposits. Petrological investigations reveal two main stages of mineralization. Early-stage sphalerites yield a Rb–Sr age of 251.1 ± 8.5 Ma, and it is contemporaneous with the Guanting basalt within the range of error, which has a concordant age of 247.3 ± 4.2 Ma. This metallogenic age indicates that early-stage mineralization may be related to Emeishan volcanic hydrothermal activity. Initial value of 87Sr/86Sr (0.709) and rare earth elements (REE) patterns of minerals suggest that ore-forming materials were likely derived from mixed mantle-crust sources, and paleo-seawater participated in deposition of Pb–Zn ore. There are two peaks of sulfur isotope (δ34S) in the Huangtian and Xinzhai deposits. The δ34S of early-stage sulfide is concentrated at + 1.1‰ VCDT to + 3.9‰ VCDT, suggesting that the sulfur was directly supplied by basaltic volcanic activity. Late-stage colloidal sulfides have δ34S ranging from + 6‰ VCDT to + 9‰ VCDT, suggesting marine sulfur origin, and that reduced sulfur derived from carbonate strata by thermochemical sulfate reduction (TSR). According to the geochemical characteristics, geochronology and regional geodynamic setting, we assume that early-stage mineralization in the Guanting Pb–Zn deposits is Emeishan volcanic hydrothermal mineralization, and late-stage mineralization is similar with Mississippi Valley-type (MVT) deposit. Our results provide new evidence for understanding hydrothermal mineralization associated with the Emeishan flood basalts in the SYG area.
      PubDate: 2021-11-17
      DOI: 10.1007/s00710-021-00768-6
       
  • The key role of µH2O gradients in deciphering microstructures and mineral
           assemblages of mylonites: examples from the Calabria polymetamorphic
           terrane

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      Abstract: Abstract A careful petrologic analysis of mylonites’ mineral assemblages is crucial for a thorough comprehension of the rheologic behaviour of ductile shear zones active during an orogenesis. In this view, understanding the way new minerals form in rocks sheared in a ductile manner and why relict porphyroblasts are preserved in zones where mineral reactions are generally supposed to be deformation-assisted, is essential. To this goal, the role of chemical potential gradients, particularly that of H2O (µH2O), was examined here through phase equilibrium modelling of syn-kinematic mineral assemblages developed in three distinct mylonites from the Calabria polymetamorphic terrane. Results revealed that gradients in chemical potentials have effects on the mineral assemblages of the studied mylonites, and that new syn-kinematic minerals formed in higher-µH2O conditions than the surroundings. In each case study, the banded fabric of the mylonites is related to the fluid availability in the system, with the fluid that was internally generated by the breakdown of OH-bearing minerals. The gradients in µH2O favoured the origin of bands enriched in hydrated minerals alternated with bands where anhydrous minerals were preserved even during exhumation. Thermodynamic modelling highlights that during the prograde stage of metamorphism, high-µH2O was necessary to form new minerals while relict, anhydrous porphyroblasts remained stable in condition of low-µH2O even during exhumation. Hence, the approach used in this contribution is an in-depth investigation of the fluid-present/-deficient conditions that affected mylonites during their activity, and provides a more robust interpretation of their microstructures, finally helping to explain the rheologic behaviour of ductile shear zones.
      PubDate: 2021-10-20
      DOI: 10.1007/s00710-021-00766-8
       
  • Amphibole-rich xenoliths from Devonian igneous rocks of the Pripyat rift,
           Southeastern Belarus: a window into cratonic lower-crust–upper-mantle
           boundary

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      Abstract: Abstract To obtain new insights into the composition and geological history of the crust–mantle boundary beneath a continental rift, we have investigated a suite of amphibole-rich xenoliths in comparison with amphibole-bearing granulite xenoliths, and amphibole megacrysts from Devonian volcanic rocks of the Pripyat rift in Belarus, East European Craton (EEC), for mineralogy, geochemistry and Sr–Nd isotope composition. Hornblendite, clinopyroxene hornblendite and hornblende melagabbro xenoliths are characterised by cumulate textures. Amphibole is mostly zoned magnesio-hastingsite. Two types of melts in equilibrium with this amphibole were calculated: those having more primitive composition than the host rocks of the hornblendite xenolith and those having composition similar to the host rocks of the clinopyroxene hornblendite and hornblende melagabbro xenoliths. Sr–Nd-isotopic compositions of these xenoliths confirm their affinity with the Devonian igneous rocks of the Pripyat rift. Temperature and pressure conditions were estimated as 1056 °C–1083 °C and 12–14 kbars for the clinopyroxene hornblendite xenolith, 1022 °C–1039 °C and 12–15 kbars for the hornblende melagabbro xenolith, and 1050 °C–1065 °C and 13–14 kbars for the cores of the amphibole megacrysts. The hornblendite xenolith represents a cumulate from an earlier batch of ultramafic alkaline magma, the clinopyroxene hornblendite xenolith could be a cumulate derived from the erupted Devonian alkaline magmas, and the hornblende melagabbro probably was crystallised from an unerupted batch of more-evolved magma. A granoblastic garnet–biotite–amphibole xenolith is composed mostly of unzoned ferrisadanagaite amphibole. Its bulk rock multielement pattern has positive large-ion lithophile element (LILE) and negative high field strength element (HFSE) anomalies. Mineral chemistry and bulk rock Sr–Nd isotope compositions indicate a Palaeoproterozoic granulite protolith, similar to suprasubduction magmatic rocks of the nearby ~ 2.0–1.95-Ga old Osnitsk–Mikashevichi Igneous belt (OMIB). Based on our results, we proposed a model for the evolution of the crust–mantle boundary beneath the Pripyat rift. The crust–mantle boundary beneath the Pripyat rift was formed during the Palaeoproterozoic (2.0–1.95-Ga) orogeny by emplacement of a mafic underplate and was reworked by subsequent post-orogenic events. Magmatism during Devonian rifting introduced hornblendite veins and amphibole-rich bodies, while amphibole-producing metasomatism developed from intraplate rift-related magmatism.
      PubDate: 2021-09-13
      DOI: 10.1007/s00710-021-00765-9
       
  • Syn-metamorphic sulfidation of the Gamsberg zinc deposit, South Africa

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      Abstract: Abstract The Mesoproterozoic Aggeneys-Gamsberg ore district, South Africa, is one of the world´s largest sulfidic base metal concentrations and well-known as a prime example of Broken Hill-type base metal deposits, traditionally interpreted as metamorphosed SEDEX deposits. Within this district, the Gamsberg deposit stands out for its huge size and strongly Zn-dominated ore ( >14 Mt contained Zn). New electron microprobe analyses and element abundance maps of sulfides and silicates point to fluid-driven sulfidation during retrograde metamorphism. Differences in the chemistry of sulfide inclusions within zoned garnet grains reflect different degrees of interaction of sulfides with high metal/sulfur-ratio with a sulfur-rich metamorphic fluid. Independent evidence of sulfidation during retrograde metamorphism comes from graphic-textured sulfide aggregates that previously have been interpreted as quenched sulfidic melts, replacement of pyrrhotite by pyrite along micro-fractures, and sulfides in phyllic alteration zones. Limited availability of fluid under retrograde conditions caused locally different degrees of segregation of Fe-rich sphalerite into Zn-rich sphalerite and pyrite, and thus considerable heterogeneity in sphalerite chemistry. The invoked sulfur-rich metamorphic fluids would have been able to sulfidize base metal-rich zones in the whole deposit and thus camouflage a potential pre-metamorphic oxidation. These findings support the recently established hypothesis of a pre-Klondikean weathering-induced oxidation event and challenge the traditional explanation of Broken Hill-type deposits as merely metamorphosed SEDEX deposits. Instead, we suggest that the massive sulfide deposits experienced a complex history, starting with initial SEDEX-type mineralization, followed by near-surface oxidation with spatial metal separation, and then sulfidation of this oxidized ore during medium- to high-grade metamorphism.
      PubDate: 2021-09-06
      DOI: 10.1007/s00710-021-00764-w
       
  • Isomorphism in pyroxmangite-type pyroxenoids: Mg-rich pyroxmangite from
           sanidinite of the Eifel paleovolcanic region, Rhineland-Palatinate,
           Germany

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      Abstract: Abstract The crystal structure of Mg-rich pyroxmangite from sanidinite of the Laach Lake (Laacher See) Volcano, Eifel paleovolcanic region, Rhineland-Palatinate, Germany has been solved based on single-crystal X-ray diffraction data, the final R indices for all data are: R1 = 0.0302, wR2 = 0.0617. Parameters of the triclinic unit cell are: a = 9.6410(4), b = 10.4328(6), c = 17.3419(9) Å, α = 112.256(5), β = 102.806(4), γ = 82.935(4)°, V = 1572.72(15) Å3. Space group is C-1. The empirical formula of the studied sample is Mn3.48Mg1.78Fe1.61Ca0.13(Si7.00O21), and the refined crystal-chemical formula is M1[(Mn,Fe)0.90Mg0.10] M2[(Mn,Fe)0.93Mg0.07] M3[(Mn,Fe)0.84Mg0.16] M4[(Mn,Fe)0.63Mg0.37] M5[(Mn,Fe)0.74Mg0.26] M1[(Mn,Fe)0.69Mg0.31] M1[(Mn,Fe)0.54Mg0.46] [Si7O21]. This sample is characterized by a stronger disordering of Mg among the M sites as compared to Mg-rich members of the pyroxmangite-pyroxferroite solid-solution series from xenoliths hosted by basalt of the Bellerberg volcano, Eifel. The genetic factors which could influence to the cation ordering in pyroxmangite-type minerals are discussed.
      PubDate: 2021-08-30
      DOI: 10.1007/s00710-021-00763-x
       
  • Water contents of nominally anhydrous orthopyroxenes from oceanic
           peridotites determined by SIMS and FTIR

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      Abstract: Abstract This study presents new secondary ion mass spectrometry (SIMS) reference materials (RMs) for measuring water contents in nominally anhydrous orthopyroxenes from upper mantle peridotites. The enstatitic reference orthopyroxenes from spinel peridotite xenoliths have Mg#s between 0.83 and 0.86, Al2O3 ranges between 4.02 and 5.56 wt%, and Cr2O3 ranges between 0.21 and 0.69 wt%. Based on Fourier-transform infrared spectroscopy (FTIR) characterizations, the water contents of the eleven reference orthopyroxenes vary from dry to 249 ± 6 µg/g H2O. Using these reference grains, a set of orthopyroxene samples obtained from variably altered abyssal spinel peridotites from the Atlantic and Arctic Ridges as well as from the Izu-Bonin-Mariana forearc region was analyzed by SIMS and FTIR regarding their incorporation of water. The major element composition of the sample orthopyroxenes is typical of spinel peridotites from the upper mantle, characterized by Mg#s between 0.90 and 0.92, Al2O3 between 1.66 and 5.34 wt%, and Cr2O3 between 0.62 and 0.96 wt%. Water contents as measured by SIMS range from 68 ± 7 to 261 ± 11 µg/g H2O and correlate well with Al2O3 contents (r = 0.80) and Cr#s (r. = -0.89). We also describe in detail an optimized strategy, employing both SIMS and FTIR, for quantifying structural water in highly altered samples such as abyssal peridotite. This approach first analyzes individual oriented grains by polarized FTIR, which provides an overview of alteration. Subsequently, the same grain along with others of the same sample is measured using SIMS, thereby gaining information about homogeneity at the hand sample scale, which is key for understanding the geological history of these rocks.
      PubDate: 2021-08-27
      DOI: 10.1007/s00710-021-00757-9
       
  • Petrogenesis of Early Paleozoic adakitic granitoids in the eastern Qilian
           Block, northwest China: implications for the South Qilian Ocean subduction
           

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      Abstract: Abstract The geodynamic mechanism responsible for the generation of Early Paleozoic magmatism within the Qilian Block, northwest China, remains controversial. In this paper, we present new geochronological, mineralogical, and geochemical data for the Hejiashan (HJS) granite and Lajishan (LJS) quartz diorite from the eastern Qilian Block, to constrain their origin and the regional evolutionary history. Laser abalation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) zircon U–Pb dating results show that the HJS granites and LJS quartz diorites were emplaced between 445 and 438 Myr ago. The HJS granites are high-K calc-alkaline, metaluminous to weakly peraluminous, with K2O/Na2O weight ratios of 0.84–1.12. The LJS quartz diorites are calc-alkaline and metaluminous with K2O/Na2O weight ratios of 0.34–0.46. Both have similar whole-rock Sr–Nd isotopic compositions. They are characterized by low heavy rare earth elements (HREEs) and Y concentrations, and high Sr/Y and La/Yb ratios, similar to adakitic rocks. Notably, the LJS quartz diorites are more depleted in HREEs and Y, and have much higher Mg# [= 100 × Mg/(Mg + Fe)], La/Yb, Sr/Y, and zircon εHf(t) values, and MgO, Cr, Co and Ni concentrations than those of the HJS granites. The HJS granites were most likely derived from partial melting of a thickened juvenile lower crust with amphibole and minor plagioclase as residual phases in the magma source. Conversely, the LJS quartz diorites were produced by partial melting of the subducted oceanic slab and minor sedimentary materials in the garnet and rutile stability field. Combined data from this and previous studies suggest that the Early Paleozoic magmatism within the Qilian Block mainly occurred ca. 464–402 Myr ago as a response to post-collisional extension. Break-off of the northward subducted South Qilian oceanic slab after continental collision between the Qaidam and Qilian Blocks was the primary dynamic mechanism responsible for the Early Paleozoic extensive crust-mantle interaction and magmatism within the Qilian Block.
      PubDate: 2021-08-27
      DOI: 10.1007/s00710-021-00762-y
       
  • Origin and evolution of the Masjed Daghi Cu-Au-Mo porphyry and gold
           epithermal vein system, NW Iran: constraints from fluid inclusions and
           sulfur isotope studies

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      Abstract: Abstract The Masjed Daghi porphyry-epithermal Cu-Au-Mo deposit in the northern Arabian-Eurasian collision zone of the Alborz Magmatic Assemblage, NW Iran, is hosted by an early Miocene quartz monzodiorite to diorite intrusion that intruded Eocene volcanic rocks. Potassic, phyllic, argillic, and propylitic alterations associated with four stages of porphyry mineralization (I to IV) are distinguished. Late high-sulfidation epithermal veins of mainly quartz or quartz-barite are enclosed in concentric zones of advanced argillic, argillic, silicic, and propylitic alterations. Poly-phase brine inclusions from the stage ΙΙ porphyry mineralization have homogenization temperatures (Th) between 305 and 600 ºC, with salinity from 30.2 to 73.9 wt% NaCl equivalent. Brines inclusions of stages ΙΙΙ and ΙV have Th from 192 to 466 ºC and salinity from 20.6 to 59.2 wt% NaCl equivalent. These brine inclusions were trapped with vapor-rich inclusions, which have Th from 122 to 318 ºC and low-moderate salinity of 0.3 to 22.3 wt% NaCl equivalent. Fluid inclusions from quartz and sphalerite in epithermal veins yielded Th ranges of 123–298 °C and 121–218 °C, and salinity ranges of 1.9–12.8 and 1.9–11.2 wt% NaCl equivalent, respectively. The δ34S values of sulfide minerals from stages ΙΙ and ΙΙΙ porphyry mineralization vary from + 0.9 to + 2.3‰, whereas the δ34S values of sulfides from the late epithermal veins range from + 1.2 to -1.1‰. These characteristics are consistent with a similar magmatic source for both the fluids of porphyry mineralization and subsequent high-sulfidation epithermal veins. The Masjed Daghi deposit that represents a telescoped porphyry-epithermal system of copper–gold mineralization in the center and peripherals of the early Miocene intrusive stocks shows both similarities and differences to other Tethyan deposits in the Alpine-Himalayan orogenic belt.
      PubDate: 2021-08-20
      DOI: 10.1007/s00710-021-00761-z
       
 
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