Complex metasomatic history and exhumation-driven refertilization of subcontinental lithospheric mantle beneath Central Europe
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| Year of publication | 2024 |
| Type | Article in Proceedings |
| Conference | 4th European Mineralogical Conference |
| MU Faculty or unit | |
| Citation | |
| Web | https://emc-2024.org/ |
| Keywords | peridotite-pyroxenite association; mantle refertilization; chromatographic metasomatism; multiphase solid inclusions; Bohemian Massif |
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| Description | The peridotite-pyroxenite association records an extensive refertilization of the originally refractory subcontinental lithospheric mantle (SCLM). This resulted from reactive percolation of depleted MORB mantle-like (DMM) melts produced by decompression partial melting of the asthenosphere at exhumation related to lithospheric thinning [4]. The transformation of an original refractory protolith (likely harzburgite) to fertile lherzolite is documented by conspicuous LREE depletion, Sr–Nd isotopic signatures (87Sr/86Sr338 ? 0.7028; ?Nd338 7.3), high bulk CaO and Al2O3 contents reflecting relatively high modal amount of clinopyroxene (up to 9 vol%) of lherzolite. Trace element chemistry of clinopyroxene (e.g. high Ti/Eu and Ti/Nb) and garnet (elevated ?REE, Zr, Ti) along with whole-rock positive correlation between fluid-immobile incompatible elements (Zr, Yb, Sc, V) also record the SCLM refertilization. The percolation of DMM-like basaltic melts (87Sr/86Sr338 0.7025–0.7029; ?Nd338 ? 7.9) in wall-rock peridotite triggered various metasomatic reactions involving: (i) stealth metasomatism, recorded by extensive clinopyroxene and garnet crystallization in lherzolite, (ii) cryptic metasomatism, reflected by lower Mg# values of orthopyroxene and olivine in lherzolite, and (iii) modal metasomatism, resulting in crystallization of amphibole and phlogopite in lherzolite adjacent to the veins. The modal compositional imaging coupled with elemental distribution maps of the peridotite-pyroxenite interface revealed the main ways of migration of silicate melts through the upper mantle and strong element fractionation controlled by differentiation of the basaltic melt. Accordingly, we demonstrate that DMM-like melt can significantly fractionate during the reactive percolation, leading to the segregation of volatile-rich melt fractions that can migrate through large volumes of wall-rock peridotites and produce chromatographic SCLM enrichment in highly incompatible elements. |
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