Subjects -> MINES AND MINING INDUSTRY (Total: 82 journals)
Showing 1 - 42 of 42 Journals sorted alphabetically
American Mineralogist     Hybrid Journal   (Followers: 16)
Applied Earth Science : Transactions of the Institutions of Mining and Metallurgy     Hybrid Journal   (Followers: 4)
Archives of Mining Sciences     Open Access   (Followers: 3)
AusiMM Bulletin     Full-text available via subscription   (Followers: 1)
BHM Berg- und Hüttenmännische Monatshefte     Hybrid Journal   (Followers: 2)
Canadian Mineralogist     Full-text available via subscription   (Followers: 7)
CIM Journal     Hybrid Journal  
Clay Minerals     Hybrid Journal   (Followers: 9)
Clays and Clay Minerals     Hybrid Journal   (Followers: 5)
Coal Science and Technology     Full-text available via subscription   (Followers: 4)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 14)
Environmental Geochemistry and Health     Hybrid Journal   (Followers: 3)
European Journal of Mineralogy     Hybrid Journal   (Followers: 14)
Exploration and Mining Geology     Full-text available via subscription   (Followers: 3)
Extractive Industries and Society     Hybrid Journal   (Followers: 2)
Gems & Gemology     Full-text available via subscription   (Followers: 2)
Geology of Ore Deposits     Hybrid Journal   (Followers: 5)
Geomaterials     Open Access   (Followers: 3)
Geotechnical and Geological Engineering     Hybrid Journal   (Followers: 9)
Ghana Mining Journal     Full-text available via subscription   (Followers: 3)
Gold Bulletin     Hybrid Journal   (Followers: 2)
Inside Mining     Full-text available via subscription  
International Journal of Coal Geology     Hybrid Journal   (Followers: 4)
International Journal of Coal Preparation and Utilization     Hybrid Journal   (Followers: 2)
International Journal of Coal Science & Technology     Open Access   (Followers: 1)
International Journal of Hospitality & Tourism Administration     Hybrid Journal   (Followers: 16)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 12)
International Journal of Mining and Geo-Engineering     Open Access   (Followers: 4)
International Journal of Mining and Mineral Engineering     Hybrid Journal   (Followers: 8)
International Journal of Mining Engineering and Mineral Processing     Open Access   (Followers: 6)
International Journal of Mining Science and Technology     Open Access   (Followers: 4)
International Journal of Mining, Reclamation and Environment     Hybrid Journal   (Followers: 6)
International Journal of Rock Mechanics and Mining Sciences     Hybrid Journal   (Followers: 9)
Journal of Analytical and Numerical Methods in Mining Engineering     Open Access  
Journal of Applied Geophysics     Hybrid Journal   (Followers: 18)
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of China Coal Society     Open Access  
Journal of China University of Mining and Technology     Full-text available via subscription   (Followers: 1)
Journal of Convention & Event Tourism     Hybrid Journal   (Followers: 6)
Journal of Geology and Mining Research     Open Access   (Followers: 10)
Journal of Human Resources in Hospitality & Tourism     Hybrid Journal   (Followers: 9)
Journal of Materials Research and Technology     Open Access   (Followers: 2)
Journal of Metamorphic Geology     Hybrid Journal   (Followers: 17)
Journal of Mining Institute     Open Access  
Journal of Mining Science     Hybrid Journal   (Followers: 5)
Journal of Quality Assurance in Hospitality & Tourism     Hybrid Journal   (Followers: 6)
Journal of Sustainable Mining     Open Access   (Followers: 3)
Journal of the Southern African Institute of Mining and Metallurgy     Open Access   (Followers: 6)
Lithology and Mineral Resources     Hybrid Journal   (Followers: 4)
Lithos     Hybrid Journal   (Followers: 11)
Mine Water and the Environment     Hybrid Journal   (Followers: 6)
Mineral Economics     Hybrid Journal   (Followers: 2)
Mineral Processing and Extractive Metallurgy : Transactions of the Institutions of Mining and Metallurgy     Hybrid Journal   (Followers: 14)
Mineral Processing and Extractive Metallurgy Review     Hybrid Journal   (Followers: 5)
Mineralium Deposita     Hybrid Journal   (Followers: 4)
Mineralogia     Open Access   (Followers: 2)
Mineralogical Magazine     Hybrid Journal   (Followers: 1)
Mineralogy and Petrology     Hybrid Journal   (Followers: 5)
Minerals     Open Access   (Followers: 2)
Minerals & Energy - Raw Materials Report     Hybrid Journal   (Followers: 1)
Minerals Engineering     Hybrid Journal   (Followers: 14)
Mining Engineering     Full-text available via subscription   (Followers: 7)
Mining Journal     Full-text available via subscription   (Followers: 4)
Mining Report     Hybrid Journal   (Followers: 3)
Mining Technology : Transactions of the Institutions of Mining and Metallurgy     Hybrid Journal   (Followers: 4)
Mining, Metallurgy & Exploration     Hybrid Journal  
Natural Resources & Engineering     Hybrid Journal  
Natural Resources Research     Hybrid Journal   (Followers: 5)
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: 4)
Réalités industrielles     Full-text available via subscription  
Rem : Revista Escola de Minas     Open Access  
Resources Policy     Hybrid Journal   (Followers: 4)
Reviews in Mineralogy and Geochemistry     Hybrid Journal   (Followers: 5)
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: 9)
Rocks & Minerals     Hybrid Journal   (Followers: 5)
Rudarsko-geološko-naftni Zbornik     Open Access  
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: 5  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1438-1168 - ISSN (Online) 0930-0708
Published by Springer-Verlag Homepage  [2656 journals]
  • Chromian spinel neomineralisations and the microstructure of plastically
           deformed ophiolitic peridotites (Kraka massifs, Southern Urals, Russia)
    • Abstract: Results of a microstructural study of spinel peridotite samples obtained from the Kraka massif in the Southern Urals, involving findings of Cr-spinel neomineralisations within intensive ductile deformed silicates (olivine and orthopyroxene), are presented. The new-formed Cr-spinel grains show different stages of syn-deformation growth as evidenced by investigations combining petrography, decorated dislocation structure analysis, scanning electron microscopy and electron backscatter diffraction (EBSD). Initial precipitations appearing as rods or lamellae are observed to form around structural defects of host silicate grains (olivine and orthopyroxene) by means of impurity segregation or heterogeneous nucleation in the most distorted lattice regions (i.e., in the predominant recrystallisation zones). Syn-deformational crystal growth leads to a complication and coarsening of the grain morphology by coalescence due to a reduction in grain boundary (interfacial) energy. While in the process of growing, the Cr-spinel grains capture fragments of silicate matrix in the solid-state process. The final stage of Cr-spinel growth involves a change in morphology resulting in their characteristic crystallographic forms (spheroidisation). The presence of euhedral Cr-spinel grains, typical for ophiolitic dunite bodies, is a result of interfacial energy reduction in areas of grain boundaries of the hardest phase. The general trend of the observed stages relates closely with the localisation of deformation zones in the upwelling upper mantle (diapir), which are composed by the weakest phase of olivine (dunites). The concentration of the weakest olivine phase in the mobile zones, which is energetically beneficial, explains why dunite bodies having euhedral chromite grains comprise the dynamic equilibrium rocks in the plastic flow localisation zones in upper mantle diapirs. Conversely, assemblages having pyroxene phases, which are stronger and larger in size compared to olivine, are not stable in these zones.
      PubDate: 2021-04-10
       
  • Chemical composition of magnetite and chlorite from the stringer zone of
           the Nudeh volcanogenic massive sulfide (VMS) deposit, Iran: geological
           implications
    • Abstract: The southwest Sabzevar basin situated in the Sabzevar zone is considered to be an attractive metallogenic province in Iran that hosts both volcanogenic massive sulfide (VMS) and stratiform manganese deposits. The Nudeh Besshi-type VMS deposit is located in the Lower Late Cretaceous volcano-sedimentary sequence. The ore mineralization in this deposit is hosted in the alkali olivine basalt flow and tuffaceous silty sandstone rocks. The Nudeh VMS deposit consists of 2 million metric tons of Cu-Zn massive sulfide overlying a Cu-Fe-rich stringer. The massive sulfide orebody consists dominantly of pyrite, chalcopyrite, friedrichite, magnetite, and sphalerite, together with minor quartz, chlorite, and sericite. Chloritization, silicification, and sericitization are the main wall-rock alteration types; alteration intensity increases towards the stringer zone. Chloritized footwall rocks extend up to 20 m below the stringer zone. The quartz-bearing stringer veins also contain pyrite, chalcopyrite, magnetite, and bornite. Magnetite crystals from the stringer ores show variable contents of many elements, such as MgO (0.05 wt%), Al2O3 (0.63 wt%), TiO2 (0.07 wt%), V2O3 (0.045 wt%), SiO2 (0.65 wt%), CoO (0.10 wt%), NiO (0.009 wt%), ZnO (0.023 wt%), and CaO (0.03 wt%). The moderate to high V contents are interpreted to result from relatively reduced, seafloor hydrothermal activiy. Compositional variations of magnetite are possibly related to variations in oxygen fugacity, temperature, and water/rock interaction. Within the stringer zone, chlorite 2 (Chl-2) in the vein-veinlets and chlorite 1 (Chl-1) in the chloritized alkali olivine basalt rock are chemically indistinguishable, with 26.92–34.67 wt% FeO and 5.99–14.01 wt% MgO. Chlorite geothermometer studies indicate crystallization formation temperatures of 414 °C (Chl-1) and 303 °C (Chl-2), respectively.
      PubDate: 2021-04-01
       
  • Multiphase intrusion at the giant Pulang porphyry Cu-Au deposit in western
           Yunnan (Southwestern China): comparison between ore-causative and barren
           intrusions
    • Abstract: Porphyry Cu-Au deposits (PCDs) have commonly multiphase porphyry intrusions, yet only one (or a few) of the intrusive phase is/are ore-causative. Understanding the criteria to form ore-causative porphyry is important for both ore deposit research and PCD exploration. At the giant Pulang PCD in western Yunnan, there are three generations of porphyries, i.e., (from oldest to youngest) the quartz diorite porphyry (QDP), quartz monzonite porphyry (QMP) and granite porphyry (GP), and only the QMP has major mineralization. Based on ore deposit geology, and zircon U–Pb–Hf–O isotope systematics, we suggested that the QMP is spatially and temporally ore-related. Oxygen fugacity of the QMP and GP magmas is estimated to be higher than that of the QDP. In addition, Hf–O isotope compositions of the QMP and GP are close to those of the average mantle. We suggested that with the continuous Late Triassic subduction of the Garzê–Litang ocean basin, the subducted-slab dehydration and the addition of mantle-wedge materials to the ore-forming magmas increased gradually. The younger magmas (e.g., QMP and GP) are thus more oxidized, and have higher water and ore-material contents, giving them higher ore-forming potential. The reason maybe that the late GP is barren may be due to the depletion of ore-forming materials by the main-stage mineralization during the QMP intrusion.
      PubDate: 2021-04-01
       
  • Unusual green Type Ib–Iab Dniester–type diamond from Ukrainian
           placers
    • Abstract: Among placer diamond occurrences in Ukraine, a group of microdiamonds have been distinguished that have specific morphological, color and spectral characteristics, not observed in other natural diamonds. These diamonds, termed “Dniester–type diamonds”, have tetrahexahedroidal and rhombododecahedroidal morphologies, green coloration, and high concentrations of single–atom, unaggregated nitrogen in the form of C–centers (66–74% of all N atoms), along with low ratios of nitrogen aggregation (0–13% agrregation ratio) and high total nitrogen content (892–1493 atomic ppm). With these characteristics, Dniester–type diamonds are approximate the Type Ib-Iab classification. The predominance of single–atom, unaggregated nitrogen indicates a short residence time under high–temperature conditions. These Dniester–type diamonds have a narrow range of carbon isotopic compositions, from δ13С = -10.52‰ VPDB tо -12.82‰ VPDB (average δ13С = -11.85‰ VPDB). They are distributed in Quaternary and Neogene sediments of the southwestern part of the Ukrainian Shield. This distribution forms a local halo within the Dniester and Southern Bug rivers interfluve and Black Sea beach sediments, approximately 650 km in length. This implies their endemic character and the likely nearby presence of primary source(s) of unknown, possibly non–kimberlitic type.
      PubDate: 2021-04-01
       
  • Primary inclusions of burbankite in carbonatites from the Fen complex,
           southern Norway
    • Abstract: Carbonatites in the Fen intrusive complex (southern Norway) contain abundant burbankite (confirmed by Raman microspectroscopy) as inclusions in calcite, dolomite and, less commonly, fluorapatite and pyrochlore. Typically the inclusions occur in the core of calcite or dolomite grains relatively unaffected by subsolidus processes, and are associated with Fe-poor dolomite or Sr-rich calcite, respectively. Burbankite does not exceed 30 × 50 μm in size and is characteristically absent from the peripheral areas of carbonate grains affected by recrystallization or interaction with fluids. Compositionally, the mineral falls within the following range: (Na1.51–2.16Ca0.58–1.21)(Sr1.50–2.42Ca0.28–0.57LREE0.05–0.64Ba0.06–0.41)(CO3)5 and contains low Th, but no detectable Mg, Fe or F (LREE = light rare-earth elements: Ce > La > Nd > Pr > Sm). Burbankite inclusions at Fen are interpreted as primary and indicative of Na enrichment in their parental carbonatitic magma. Dissociation of burbankite during subsolidus re-equilibration of its host phases with fluids undoubtedly served as one of the sources of LREE for the development of late-stage mineralization in the Fen complex.
      PubDate: 2021-04-01
       
  • Evolution of lithospheric mantle beneath the Maguan region, southwestern
           margin of the South China block based on mantle xenoliths in Miocene
           alkaline volcanic rocks
    • Abstract: The Maguan (MG) region in the southwestern part of the South China Block contains many Neogene potassic basaltic volcanic rocks along the Ailao Shan–Red River (ASRR) shear zone. These alkaline volcanic rocks contain abundant peridotite xenoliths which are mostly spinel (Spl)-facies lherzolite. We examined xenoliths in young, ~12 Ma, alkaline basalts. Most contain clinopyroxene (Cpx), >15 vol%, and minor xenoliths contain low Cpx, ~10 vol%. Olivine (Ol) shows forsterite components ranging from 88.6 to 90.1 in most lherzolite and from 90.4 to 90.8 in depleted lherzolite, Spl Cr# (=Cr/(Cr + Al)) between 0.08–0.11 for lherzolite and 0.17–0.22 for depleted lherzolite. Platinum group elements (PGE) show a near flat primitive mantle-normalized pattern; the ratios of IPGE/PPGE are 1.3–1.8 for lherzolite and 2.1 for depleted lherzolite. The xenoliths do not contain metasomatic minerals, but Cpx in depleted lherzolite samples is enriched in light rare earth elements (LREE; (La/Sm)N = 0.97–1.74). Two pyroxene geothermometry gives the temperatures ranging from 1029 °C to 1148 °C (average 1087 °C, n = 13). Spl–Ol geothermobarometry yields the oxidation state ranging from FMQ −1.5 to −0.25 with an average value of FMQ −0.59 (n = 13), which is comparable to those of abyssal peridotite and the asthenospheric mantle. The calculated temperatures and oxidation state are similar among samples independent of mineralogy and mineral chemistry, suggesting that partial melting and the cryptic metasomatism did not change the oxidation conditions. The data suggest that the subcontinental lithospheric mantle (SCLM) beneath the region formed from the asthenosphere mantle. Since the South China Block is generally underlain by Proterozoic SCLM, the data obtained this study suggest that the ancient lithosphere was replaced by the asthenospheric mantle in the local extension along the ASRR shear zone.
      PubDate: 2021-04-01
       
  • Petrogenesis of Cenozoic high-Mg (picritic) volcanic rocks in the České
           středohoří Mts. (Bohemian Massif, Czech Republic)
    • Abstract: Representative samples of high-Mg (picritic) rocks of Eocene to Oligocene age (38 to 21 Ma) from the České středohoří Mts. (CSM) in the Ohře/Eger Rift were studied and compared with Cenozoic high-Mg rocks from the Bohemian Massif. The picritic rocks of the CSM correspond to picrite, meimechite and basanite to tephrite. Individual petrographic types are characterised by the association of mafic minerals: magnesian olivine (Fo86–80) + clinopyroxene (aluminian diopside) ± amphibole (pargasite/kaersutite) ± dark mica (ferroan phlogopite). The contents of incompatible elements, such as Nb, Ta, U, Th, the LaN/YbN ratios, and the overall Sr–Nd–Pb isotope signatures of the high-Mg rocks partly overlap the basanites of the Ústí Formation, also showing a similar age (44–21 Ma). The Pb isotope signature for all recognised high-Mg rock types is compatible with a variable contribution from an inherited (Variscan) orogenic Pb component preserved in their lithospheric mantle source. Both the high-Mg volcanic rocks from the CSM and from other areas of the Bohemian Massif require the involvement of a heterogenous lithospheric source. Their parental melts were generated by variable degree of melting of an olivine-rich peridotitic mantle, containing clinopyroxene–amphibole (± phlogopite) vein assemblages with highly radiogenic Sr and Pb signatures.
      PubDate: 2021-04-01
       
  • In situ observation of chrysotile decomposition in the presence of
           NaCl-bearing aqueous fluid up to 5 GPa and 400 °C
    • Abstract: Natural occurrence of chrysotile, a rock-forming serpentine mineral, is largely associated with fluid-rich environments, thus making the fluid chemistry an important factor governing chrysotile growth and stability. Paper examines the effect of alkali chlorides, lowering the H2O activity in fluid, on chrysotile stability at high pressure. The behavior of natural chrysotile (Thetford) in the presence of concentrated NaCl-H2O fluids was studied up to 5 GPa and 400 °C using in-situ Raman spectroscopy and X-ray diffraction combined with resistively heated diamond anvil cell. Reference experiments were also performed on salt-free samples. In salt-free H2O-saturated conditions, chrysotile is stable within the whole temperature range at 1.5–5 GPa. The presence of NaCl in the fluid at XNaCl = mole NaCl/(NaCl+H2O) ≈ 0.1–0.15 strongly suppresses the temperature of chrysotile dehydration at 2–4 GPa to 380 °C, which is about 170 °C lower compared to the equilibrium data for H2O-saturated salt-free system. Talc/talc-like phase only crystallizes at HP-HT conditions as product of the reaction “chrysotile → forsterite + talc”, whereas forsterite appears after the P,T release. This indicates an enhanced solubility of forsterite in supercritical NaCl-H2O fluid at HP-HT conditions. Chrysotile shows disordering/amorphization at unusually low temperature of 150 °C. The shift of the chrysotile dehydration to lower temperatures in saline environment makes this process more operable in natural metamorphic processes in serpentinites. This effect can be extended to other serpentine minerals, including antigorite, a common participant of HP-HT metamorphic reactions in subduction zones.
      PubDate: 2021-04-01
       
  • Cl-rich amphiboles and micas in rocks of the Middle Riphean Kusa-Kopan
           complex of mafic layered intrusions (southern Urals, Russia)
    • Abstract: High-Cl amphiboles and micas were found in rocks of the Kusa-Kopan complex of the Middle Riphean layered ore-bearing (Ti, Fe, V) mafic intrusions in the Southern Urals, Russia. Chloro-hastingsite (3.30–4.57 wt% Cl) was found in garnet-bearing orthoamphibolite in the Medvedevsky massif. Compositions of Cl-rich (3.26–4.84 wt% Cl) amphibole from borehole # 2 of the Kusinsky massif located to the north, correspond to “potassic-ferro-chloro-pargasite”, in some cases to potassic-chloro-hastingsite. Thus, in addition to the high-K trend in the evolution of Cl-rich amphiboles, a tendency to low-K content was revealed. Apart from amphibole, biotite with Cl content from 1.73 to 2.32 wt% corresponding to the annite-phlogopite series was observed. Calculations showed that Cl content reached 1.4 wt% in the melt/fluid during the crystallization of the high-Cl amphiboles of the Kusa part of the layered intrusion, and was about 6000 ppm during the crystallization of the “chloro-hastingsite” from the Medvedevsky massif. The same effect could be seen in lower-Cl varieties, where the differences reached a factor of three. The Cl content in the initial melt did not exceed 400 ppm, locally increasing up to 1000–4000 ppm. Chlorine-rich amphiboles are the result of a local excess concentration of chlorinated compounds of complex composition at the final stage of the magmatic system development (under subsolidus conditions). The emergence of an open system cannot be ruled out, in which Cl content in the fluid increases over time resulting from an external source, which is enriched in Cl due to the addition of mobilized brines from the host rocks additionally enriched with CO2.
      PubDate: 2021-03-18
       
  • Mafic to intermediate composition intrusions from the Kahak area, central
           Urumieh-Dokhtar arc of Iran: transition from Eocene to Miocene intra-arc
           extensional magmatism
    • Abstract: Several gabbro, gabbroic diorite, and diorite intrusions were emplaced in the Neotethyan Urumieh-Dokhtar magmatic arc in the Kahak area of the Zagros Orogen. The plutonic rocks intruded Cenozoic volcanic and pyroclastic succession. U-Pb dating via LA-ICP-MS of zircon yields early to middle Eocene ages of ~53 to 38 Ma for the diorite and gabbroic diorite in Veshnaveh and Naragh areas and Miocene ages of 23 to 20 Ma for gabbroic rocks in the Kerogan and Fordou areas. The Eocene magmatic phase occurred quite possibly as three continuous pulses. The Eocene and Miocene intrusions have negative Nb-Ta anomalies like those of subduction-related magmas. The Pb isotopic compositions show the involvement of subducted sediment in the source of the studied samples. The Eocene intrusions are tholeiitic and enriched in incompatible-trace-elements (especially the HFSE) compared to the Miocene intrusions which are calc-alkaline and have lower concentrations of most incompatible trace elements. Sr-Nd isotopic compositions of the Eocene rocks lie close to the mantle array and near Bulk Silicate Earth, but the Miocene suite is shifted to higher (87Sr/86Sr)i. The higher (87Sr/86Sr)i, along with larger Ba, K, Pb, and Sr anomalies, in the Miocene suite imply more slab fluid input and/or crustal contamination. Apparently, the Eocene mafic magmas formed in slightly metasomatized sub-continental lithospheric mantle (SCLM), whereas the Miocene suite was derived from highly metasomatized, deeper levels of the SCLM. We suggest that slab roll back occurred between the Eocene and Miocene and transferred the location of mantle partial melting to greater depths.
      PubDate: 2021-03-18
       
  • Origin of andradite in the Quaternary volcanic Andahua Group, Central
           Volcanic Zone, Peruvian Andes
    • Abstract: Euhedral andradite crystals were found in trachyandesitic (latitic) lavas of the volcanic Andahua Group (AG) in the Central Andes. The AG comprises around 150 volcanic centers, most of wich are monogenetic. The studied andradite is complexly zoned (enriched in Ca and Al in its core and mantle, and in Fe in this compositionally homogenous rim). The core-mantle regions contain inclusions of anhydrite, halite, S- and Cl-bearing silicate glass, quartz, anorthite, wollastonite magnetite and clinopyroxene. The chemical compositions of the garnet and its inclusions suggest their contact metamorphic to pyrometamorphic origin. The observed zoning pattern and changes in the type and abundance of inclusions are indicative of an abrupt change in temperature and subsequent devolatilization of sulfates and halides during the garnet growth. This process is interpreted to have taken place entirely within a captured xenolith of evaporite-bearing wall rock in the host trachyandesitic magma. The devolitilization of sediments, especially sulfur-bearing phases, may have resulted in occasional but voluminous emissions of gases and may be regarded as a potential hazard associated with the AG volcanism.
      PubDate: 2021-03-13
       
  • An age-integrated geochemical and computational phase-equilibria study
           from the Wangtu Gneissic Complex, N-W Himalaya, and its paleogeographic
           implications in Columbia assembly
    • Abstract: The Paleoproterozoic thermal evolution of the north-Indian continental margin is debatable as the Lesser Himalaya granites are interpreted either as a subduction-zone volcanic arc or rift-related magmatism during Columbia assembly or disintegration processes, respectively. Integrated mineralogical, geochemical investigations, temperature estimates from Ti solubility in biotite and zircon, and computational phase equilibria modeling from the Wangtu Gneissic complex (WGC), Himachal Himalaya reveal peraluminous nature for most of the WGC rocks that crystallize at ~650 °C and ~ 1.0–1.1 GPa. The U-Pb ages from magmatic zircons from the WGC exhibit two prominent age clusters at 1867 Ma and 2487 Ma. The U-Pb zircon data and modeled phase equilibria for metasedimentary rock reveal the generation of S-type peraluminous magma parental to the WGC, through melting of preexisting supracrustal rocks at ~1800 Ma, within ~850–900 °C and 1.1–1.2 GPa, similar to P-T conditions observed in modern-day subduction zone settings. The results obtained from this study reveal the north Indian continental margin was an active subduction zone during the Paleoproterozoic Columbia supercontinent assembly that extends across the Himalayas.
      PubDate: 2021-03-11
       
  • Geology and genesis of the Qi191 granite-hosted gold deposit in the
           southern margin of the North China Craton: constraints from SIMS zircon
           U–Pb, sericite 40 Ar– 39 Ar, in-situ trace elements, and in-situ
           S–Pb isotopes
    • Abstract: The Qi191 Au deposit is a newly discovered granite-hosted Au deposit in the Qiyugou Au orefield, located in the southern margin of the North China Craton (NCC). Gold ore bodies are hosted by both the Qi191 hornblende monzogranite and the Taihua Complex and are composed of disseminations and sparse veins. K-feldspar, quartz-sericite, and sericite-chlorite alteration formed outward from the center to the periphery of the mineralized granite. Principal ore minerals include galena, pyrite, and chalcopyrite, with minor sphalerite, hematite, pyrrhotite, gold, famatinite, and hessite. The Qi191 Au deposit formed over four successive stages of hydrothermal mineralization: a quartz stage (I), a quartz-pyrite-galena stage (II), an economic quartz-calcite-galena-pyrite stage (III), and a quartz-calcite stage (IV). The Qi191 hornblende monzogranite yields a SIMS zircon U–Pb age of 131.3 ± 1.0 Ma. Hydrothermal sericite yields a plateau 40Ar–39Ar age of 132.9 ± 1.4 Ma, which is consistent with the zircon U–Pb age, suggesting that the Qi191 Au deposit is generically related to the hornblende monzogranite. Trace element contents and S isotopic compositions of sulfides indicate that metals and S entered the hydrothermal fluid as pulses. The equilibrium temperature of S and the isotopic compositions of S–Pb reflect a magmatic source. Gold mainly precipitated as native gold in a relatively acidic and reducing environment. This work suggests that further exploration for magmatic hydrothermal gold deposits in the Qiyugou and more widely in the southern margin of the NCC should target hornblende monzogranites such as the Qi191 and Qi189 granitoids.
      PubDate: 2021-02-26
       
  • Evolution of spinel-bearing ultrahigh-temperature granulite in the Jining
           complex, North China Craton: constrained by phase equilibria and Monte
           Carlo methods
    • Abstract: The peak temperature and timescale of ultrahigh-temperature (UHT) metamorphism are significant for understanding its thermal budget and geodynamic evolution. The spinel-bearing (sapphirine-absent) UHT granulite at the Xuwujia area in the Jining complex, North China Craton was revealed to have undergone a metamorphic evolution that involves the pre-Tmax (maximum temperature) heating decompression to the Tmax stage with an extreme temperature of ~1125 °C, the post-Tmax cooling to the fluid-absent solidus (~860 °C) at 0.8–0.9 GPa, and sub-solidus decompression. The Tmax condition was recorded by the inferred feldspar-absent peak assemblage of spinel ± garnet. The post-Tmax cooling evolution was indicated by the sequential appearances of plagioclase, K-feldspar, sillimanite and biotite, as well as the core-to-rim ascending grossular component in garnet. Moreover, some texturally zoned spinel has exsolved lamellae of magnetite in the core and shows rim-ward increase of Mg and Al, which suggests a temperature decrease from >1100 °C in local domains isolated from quartz. Spinel with exsolved magnetite lamellae or low Al/(Al + Fe3+) is therefore proposed as an indicator for UHT conditions in metapelites. Probability simulation on the collected zircon ages yields a timescale of ~40 Myr (95% confidence; during 1.90–1.94 Ga) for the supra-solidus cooling stage of the UHT metamorphism in the Jining complex. This extreme UHT metamorphism has reached the rock’s dry solidus (~1125 °C) and undergone slow cooling, which is interpreted to result from a post-orogenic plume activity with sufficient advective heating from hyperthermal mafic intrusions.
      PubDate: 2021-02-25
       
  • Late Jurassic Maofengshan two‐mica granites in Guangzhou, South China:
           fractional crystallization products of metasedimentary‐rock‐derived
           magmas
    • Abstract: Late Jurassic (~ 160 Ma) granitoids are widely distributed across the South China Block. These granitoids are mainly biotite granites, with subordinate amphibole-bearing and two-mica or muscovite-bearing granites. Previous studies have shown that a clear negative correlation exists between SiO2 and P2O5 contents in the amphibole-bearing, biotite, two-mica, and muscovite-bearing granites, and suggested that these granitoids are I-type (metaigneous-rock-derived) or fractionated I-type granites. However, whether the Late Jurassic two-mica granites were formed by fractional crystallization of S-type (metasedimentary-rock-derived) granitic magmas in addition to fractional crystallization of I-type granitic magmas, and the role of mantle-derived magma in the generation of the Late Jurassic granitoids, are still debated. We present data for two-mica granites in the Maofengshan area of Guangzhou, Guangdong Province, southeastern China. Zircon U–Pb ages show that these rocks were formed during the Late Jurassic (159 Ma). The Maofengshan two-mica granites have high SiO2 contents (73.1–74.1 wt.%) and peraluminous compositions (A/CNK = 1.08–1.11). They are enriched in Rb, Th, U, and Pb, depleted in Ba, Sr, Nb, and Ti, and have pronounced negative Eu anomalies. The Maofengshan granites also have enriched Sr–Nd–Hf isotopic compositions [(87Sr/86Sr)i = 0.7103–0.7118, εNd(t) = − 10.3 to − 10.1, and εHf(t) = − 14.2 to − 7.5)] and heavy zircon O isotopic compositions (δ18O = 8.2‰–10.2‰). We suggest that these granites were formed by fractional crystallization of metasedimentary-rock-derived granitic magmas in the middle crust (16.5–20.0 km), as they have similar major and trace element and isotopic characteristics to S-type granites and show relatively higher FeOT/MgO (5.2–5.6 > 4), (K2O + Na2O)/CaO (8.2–9.3 > 7), Rb/Sr (5.4–6.4), and Rb/Ba (1.2–1.5) and lower Nb/Ta (5.6–7.3 < 11) ratios than normal unfractionated granites. Mantle-derived mafic magma mainly provided the heat for their generation.
      PubDate: 2021-02-22
       
  • Fluorellestadite from burned coal dumps: crystal structure refinement,
           vibrational spectroscopy data and thermal behavior
    • Abstract: Nine different samples of fluorellestadite from Chelyabinsk, Kizel and Kuznetsk coal basins were studied by single-crystal X-ray diffraction analysis, thermal X-ray diffraction (25–800 °C), Infrared (IR) and Raman spectroscopy. Fluorellestadite is hexagonal, space group P63/m, the unit-cell parameters for the nine samples studied vary within rather small ranges: a = 9.415(5) – 9.4808(7) Å, c = 6.906(2) – 6.938(8) Å, V = 530.3(4) – 538.41(9) Å3. The mineral is isotypic with apatite, the structure is based upon isolated TO4 tetrahedra, where the T position is statistically occupied by Si4+ and S6+ with the ideal ratio Si:S equal to 1:1. The fluorine atoms are located in channels of the Ca4[(S,Si)O4]6 framework oriented parallel to the c axis. The thermal expansion of fluorellestadite is almost isotropic in the temperature range 25–800 °C (for ambient temperature: αa = 12.0·10−6 °C−1, αc = 11.9·10−6 °C−1; for 800 °C: αa = 18.2·10−6 °C−1, αc = 18.6·10−6 °C−1). A similar thermal behavior had been observed for fluorapatite. Despite the same structure motifs and close conditions of formation, the samples of fluorellestadite show different S/Si/P occupancies for T site and the F/Cl/OH (X-position) ratios.
      PubDate: 2021-02-18
       
  • Early Cretaceous granitoids and gabbro in the Liaodong Peninsula:
           implications for delamination of the North China Craton and Paleo-Pacific
           Plate subduction
    • Abstract: New petrological, whole-rock geochemical, zircon U–Pb geochronological, and zircon Lu–Hf isotopic data have been reported for Early Cretaceous intrusive rocks in the Wulong region of the Liaodong Peninsula on the North China Craton. The zircon U-Pb chronology shows that the crystallization age of six groups of intrusive rocks from this region is 129–123 Myr ago. These intrusive rocks can be categorized into A-type granite (granodiorite), K-rich adakite (porphyritic-like monzogranite), highly fractionated I-type granites (porphyritic-like biotite monzogranite, porphyritic-like syenogranite, and syenogranite), and gabbro. These granitoids are shown to have negative zircon εHf(t) values(-21.0 to -11.1) with old two-stage Hf model ages (TDM2(Hf)) (1.88–2.50 Ga), while gabbro has higher zircon εHf(t) values(-14.3 to -9.4) with younger TDM2(Hf) (1.77–2.08 Ga) model ages. According to our results, we believe that the porphyritic-like monzogranite was produced through partial melting of the thickened eclogitic lower crust, the gabbro was generated by partial melting of a source formed by the mixing of enriched lithospheric mantle and delaminated eclogitic lower crust, the granodiorite was formed by mixing crust materials and mafic melts, the porphyritic-like biotite monzogranite, porphyritic-like syenogranite, and syenogranite originated from the medium- to high-K basaltic lower crust. The bimodal intrusive rocks (gabbro, porphyritic-like monzogranite, and porphyritic-like biotite monzogranite) and A-type granites (granodiorite) were emplaced in an extensional setting associated with Paleo-Pacific Plate subduction. We also determined that the tectonic setting changed from extension to transpression during 125–120 Myr ago (porphyritic-like syenogranite and syenogranite). Moreover, we confirmed the hypothesis that the Early Cretaceous delamination is the result of Paleo-Pacific Plate subduction.
      PubDate: 2021-02-18
       
  • Multi-stage magmatic history of olivine–leucite lamproite dykes from
           Banganapalle, Dharwar craton, India: evidence from compositional zoning of
           spinel
    • Abstract: Mesoproterozoic lamproite dykes occurring in the Banganapalle Lamproite Field of southern India show extensive hydrothermal alteration, but preserve fresh spinel, apatite and rutile in the groundmass. Spinels belong to three genetic populations. Spinels of the first population, which form crystal cores with overgrowth rims of later spinels, are Al-rich chromites derived from disaggregated mantle peridotite. Spinels of the second population include spongy-textured grains and alteration rims of titanian magnesian aluminous chromites that formed by metasomatic interactions between mantle wall-rocks and precursor lamproite melts before their entrainment into the erupting lamproite magma. Spinels that crystallised directly from the lamproite magma constitute the third population and show five distinct compositional subtypes (spinel-IIIa to IIIe), which represent discrete stages of crystal growth. First stage magmatic spinel (spinel-IIIa) includes continuously zoned macrocrysts of magnesian aluminous chromite, which formed together with Al–Cr-rich phlogopite macrocrysts from an earlier pulse of lamproite magma at mantle depth. Crystallisation of spinel during the other four identified stages occurred during magma emplacement at crustal levels. Titanian magnesian chromites (spinel-IIIb) form either discrete crystals or overgrowth rims on spinel-IIIa cores. Further generations of overgrowth rims comprise titanian magnesian aluminous chromite (spinel-IIIc), magnetite with ulvöspinel component (spinel-IIId) and lastly pure magnetite (spinel-IIIe). Abrupt changes of the compositions between successive zones of magmatic spinel indicate either a hiatus in the crystallisation history or co-crystallisation of other groundmass phases, or possibly magma mixing. This study highlights how different textural and compositional populations of spinel provide important insights into the complex evolution of lamproite magmas including clues to elusive precursor metasomatic events that affect cratonic mantle lithosphere.
      PubDate: 2021-02-01
       
  • Natural blue zircon from Vesuvius
    • Abstract: Zircon from syenitic ejecta of Vesuvius (Campania, Italy) is unusually blue, a property shared with gem zircon from Ratanakiri province (Cambodia), which turns from natural reddish-brown to blue when heated under reducing conditions. Here, the origins of these unusual crystals were traced through geochronology, trace elements, and O-Hf isotopic compositions. The causes of its colour were investigated through optical and electron microscopy, optical absorption spectroscopy, and Raman microspectroscopy. Colour stability upon heating and ultraviolet light (UV) exposure was tested using Ratanakiri zircon as a control. Vesuvius zircon contains vesiculated zones with abundant inclusions ~2.5 μm to <100 nm in diameter (mostly U-rich thorianite and pyrochlore-group minerals), while homogeneous zircon domains are high in Th and U (up to 5.9 and 1.8 wt%, respectively). Its blue colouration is stable under UV radiation, as well as heat-treatment under reducing conditions (1000 °C; >15 h). Turbid domains rich in large inclusions change to yellow-brown after heating under oxidizing conditions, while transparent domains remain pale blue or colourless. Optical absorption spectra display sharp absorption lines attributed to U4+, and slightly elevated absorption towards shorter wavelengths. The ~1007 cm−1 ν3(SiO4) Raman band is broadened due to lattice distortion by non-stoichiometric elements in high-Th/-U zircon, whereas narrow bands in inclusion-rich domains indicate a decrease in lattice strain due to inclusion precipitation. Blue colouration in Vesuvius zircon is explained by the effect of light scattering (Rayleigh and/or Mie scattering) on highly refractive actinide-rich inclusions ranging in size from <1/10 to few multiples of the wavelengths of visible light. Inclusions likely formed during fluid-mediated coupled dissolution-reprecipitation that locally transformed lattice-strained actinide-rich zircon within several hundreds of years prior to eruption.
      PubDate: 2021-02-01
       
  • The basal dunite of the Precambrian mafic-ultramafic Näränkävaara
           intrusion: Petrogenetic considerations and implications to exploration
    • Abstract: Several mafic-ultramafic layered intrusions were emplaced in the Fennoscandian Shield during wide-spread mantle-sourced magmatism at 2.5–2.4 Ga. The Näränkävaara intrusion (surface area 5 × 30 km2), northeastern Finland, contains a 1.5–2 km thick basal dunite (not dated), and a 1.5 km thick layered series (2436 ± 5 Ma). A newly discovered marginal series between the basal dunite and the layered series indicates that the basal dunite is older, and highlights the need for further study on their relationship. Along its southern basement contact, the basal dunite contains a 200–300 m thick zone of olivine ortho- and mesocumulates, but the bulk of it is composed of olivine adcumulates and lesser olivine-orthopyroxene heteradcumulates. Based on whole-rock geochemistry, the basal dunite is divided into a low-Fe zone (average FeOt 10.2 wt% and Ni 2250 ppm) and a high-Fe zone (average FeOt 12.5 wt% and Ni 1700 ppm). Both zones have high MgO (32–47 wt%) and varying Cr (830–5160 ppm) and Al2O3/TiO2 (16–26). Textural and geochemical layering is similar along the 30 km strike of the basal dunite. A LREE-enriched high-MgO basaltic parental magma composition (13–18 wt% MgO) is inferred for the basal dunite from olivine–melt mixing trends in orthocumulates. The dunite exhibits at least two geochemical reversals as well as abundant low-porosity adcumulates, poikilitic chromite, and bimodal olivine, suggesting formation in a high-volume open magmatic system. Significant similarity in major and trace element compositions with the Näränkävaara layered series and the Burakovsky intrusion and Vetreny belt extrusives in Russian Karelia suggests that the basal dunite belongs to the Fennoscandian 2.5–2.4 Ga mafic layered intrusions. An Archean komatiitic origin for the dunite body cannot be completely ruled out, however. Distinct Ni-depletion in olivine is found in the basal dunite from the low-Fe zone to the high-Fe zone (3200 versus 2200 ppm). This depletion does not correlate with Fo contents, which suggests that it is not related to olivine fractionation. The basal dunite may thus have potential for Ni-(Cu-Co-PGE) sulfide mineralization.
      PubDate: 2021-02-01
       
 
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