Zirconology of the Lherzolite Block of the Nurali Massif (South Urals)
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Mantle xenoliths in Oligocene–Miocene alkaline lavas in Lower Silesia (SW Poland) and adjacent part of Upper Lusatia (SE Germany) are samples of the subcontinental lithospheric mantle at the time of culmination of rifting in the Eger Rift (Bohemian Massif, Central Europe). The xenoliths come from the spinel mantle facies and show that two major lithologies occur in the area: A—highly magnesian (olivine Fo 90.5–92.0) harzburgites, and B—less magnesian (olivine Fo 84.0–90.0) harzburgites. The protolith of group A was clinopyroxene-free harzburgite being the residue after extensive melting. It was affected by chromatographic carbonatite/silicate melt metasomatism, with the carbonatite metasomatism only recorded in distal parts of the chromatographic systems. The B harzburgites were penetratively metasomatised by percolating alkaline silicate melts at the time of volcanism. That metasomatism was mostly anhydrous and typically cryptic; it lowered the Mg/(Mg + Fe) ratio of olivine and orthopyroxene in the peridotites subjected to melt percolation and led in places to dissolution of clinopyroxene. The mostly harzburgitic subcontinental mantle lithospheric domain beneath Lower Silesia and Upper Lusatia differs from the lherzolitic/harzburgitic ones located to W and SW beneath other parts of European Variscan orogen.
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The Ronda ultramafic massif constitutes the Earth’s largest outcrop of peridotites (~ 300 km2) of the subcontinental lithospheric mantle (SCLM). This massif is located in the westernmost part of the Málaga province in SW Spain, and mainly consists of peridotites (lherzolites and harzburgites with lesser amounts of dunites) and mafic pyroxenite layers (usually <10 %). These rocks are arranged in a petrologic and geochemical zoning consisting, from the top to the bottom of the mantle section, of the following domains: (1) spinel (±garnet) tectonite corresponding to the exhumed SCLM roots, (2) granular peridotite formed by thermal erosion of pre-existing spinel (±garnet) tectonite due to upwelling of the asthenosphere during unroofing, and (3) plagioclase tectonite corresponding to shear zones originated shortly before or contemporaneously to the crustal emplacement. The rocks forming these three domains exhibit contrasting degrees of fertility in a wide suite of elements, offering an unequal opportunity to evaluate the impact that different bedrocks have for the distribution of High-Tech Critical Metals in soils.We performed bulk-rock analyses of around 70 samples from 10 soil profiles above peridotites from the three aforementioned petrological domains. Regardless of the original bedrock, all the analyzed soils show a common trend of progressive enrichment of Fe2O3 and Al2O3 and depletion of MgO from bedrock to the atop of the profile. Minor elements such as MnO, TiO2, Na2O and K2O overall increase from bottom to top, whereas SiO2 remains generally unchanged. Interestingly, there is positive correlations between Fe2O3 and MnO as well as other transition metals such as Cr (up to ~9000 pm),  Co (up to 310 ppm), V (up to 181 ppm), Zn (up to 136 ppm) and Sc (up to 38 ppm). A general increasing of total REE (up to ~20 ppm) is also observed in most profiles with a significant enrichment of LREE over HREE.
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