Search Results (3)

This study investigates the mineral chemistry and iron isotope composition of the Pertek Fe-skarn deposit in the Eastern Taurides, Turkey, to elucidate skarn formation and ore genesis through chemical and isotopic parameters. The deposit consists of substantial and dispersed magnetite ores formed by the intrusion of a dioritic suite into marbles. Mineral assemblages, including hematite, goethite, andradite garnet, hedenbergite pyroxene, calcite, and quartz, exhibit compositional variations at different depths within the ore body. Magnetite is commonly associated with hematite, goethite, garnet, pyroxene, calcite, and quartz. Extensive LA–ICP–MS analysis of magnetite chemistry reveals elevated trace element concentrations of titanium (Ti), aluminum (Al), vanadium (V), and magnesium (Mg), distinguishing Pertek magnetite from low-temperature hydrothermal deposits. The enrichment of Ti (>300 ppm) and V (>200 ppm), along with the presence of Al and Mg, suggests formation from high-temperature hydrothermal fluids exceeding 300 °C. Discriminant diagrams, such as Al+Mn versus Ti+V, classify Pertek magnetite within the skarn deposit domain, affirming its medium- to high-temperature hydrothermal origin (200–500 °C), characteristic of skarn-type deposits. Magnetite thermometry calculations yield an average formation temperature of 414.53 °C. Geochemical classification diagrams, including Ni/(Cr+Mn) versus Ti+V and TiO₂-Al₂O₃-MgO+MnO, further support the skarn-type genesis of the deposit, distinguishing Pertek magnetite from other iron oxide deposits. The Fe-skarn ore samples display low total REE concentrations, variable Eu anomalies, enrichment in LREEs, and depletion in HREEs, consistent with fluid–rock interactions in a magmatic–hydrothermal system. The δ⁵⁶Fe values of magnetite range from 0.272‰ to 0.361‰, while the calculated δ⁵⁶Fe_aq values (0.479‰ to 0.568‰) suggest a magmatic–hydrothermal origin. The δ⁵⁷Fe values (0.419‰ to 0.530‰) and the calculated 10³lnβ value of 0.006397 indicate re-equilibration of the magmatic–hydrothermal fluid during ore formation. Full article

Intensively metasomatized rocks from serpentinized ultramafic tectonic fragments in Dobšiná, Western Carpathians, consist of typical rodingite mineral association: hydrated garnet, vesuvianite, diopside and clinochlore. Electron microprobe analysis (EMPA) and Micro-Raman analyses of the main minerals evidence complex mineralogical evolution and variable mineral chemistry. Garnet solid solution is dominated by grossular-andradite series, which demonstrates a significant degree of hydration, mainly for grossular rich garnet cores. Garnet is locally enriched in TiO₂ (up to 13 wt%), possibly indicating a chemical relic of a Ti-oxide mineral. Younger, andradite-richer garnet rims demonstrate a low degree of hydration, suggesting a harder incorporation of an (OH)⁻ anion into its crystal structure. Garnet chemical variations display an ideal negative correlation between Al and (Fe³⁺ + Ti). The most recent mineral phase is represented by euhedral vesuvianite (± chlorite), which crystallizes at the expense of the garnet solid solution. This reaction shows a well-equilibrated character and indicates a high extent of rodingitization process. Chlorite thermometry models suggest an average temperature of late rodingite (trans) formation of about 265 °C. Full article

The Kunene Intrusive Complex (KIC), in NW Namibia and SW Angola, is one of the largest Proterozoic anorthosite massif-type exposures in the world. A geochemical, mineralogical and petrological study of four Fe–Ti(–V) oxide bodies located in the understudied Angolan part of the KIC has been performed. The massive Fe–Ti(–V) oxide bodies, locally apatite-rich (nelsonites), are lenticular or dike-like. They consist mostly of titaniferous magnetite, ilmenite and minor aluminous spinel, apatite, olivine and graphite. Titaniferous magnetite displays a wide variety of subsolvus features, including aluminous spinel–magnetite–ulvöspinel exsolutions and ilmenite (Trellis) exsolutions. This work estimated the composition of the titaniferous magnetite prior to the exsolution, in order to calculate the temperature and oxygen fugacity of the different lithologies of each ore body. The thermo-oxybarometry results obtained range from 600 °C to 820 °C and fO₂ from 10^−24.7 to 10^−14.7. These values do not correspond to magmatic crystallization in equilibrium, but to a later re-equilibration. In addition, the mineralogical and geochemical results indicate that the studied ore bodies contain economic reserves of Ti, V, and possibly of P and REE. Full article