Original paper

Upper mantle xenoliths from alkali basalts of the Vogelsberg, Germany: implications for mantle upwelling and metasomatism

Witt-Eickschen, Gudrun

European Journal of Mineralogy Volume 5 Number 2 (1993), p. 361 - 376

50 references

published: Apr 27, 1993
manuscript accepted: Dec 1, 1992
manuscript received: Jun 19, 1992

DOI: 10.1127/ejm/5/2/0361

BibTeX file

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Abstract Alkali basalt-hosted mantle xenoliths of type I (Frey & Prinz, 1978) from the Vogelsberg area (W Germany) cover a compositional range from mildly depleted lherzolites (19 wt.% clinopyroxene) to harzburgites (3 wt.% clinopyroxene), whereas dunites and pyroxenites seem to be extremely rare. Due to partial melting and magma extraction, major and moderately incompatible trace-element compositions of bulk rocks and minerals correlate with the variable modal clinopyroxene abundance, indicating a degree of ~ 30% partial melting for the most depleting harzburgites. Even though these peridotites represent residues of partial melting, some harzburgites show light rare-earth-element enrichment and a Sr-Nd isotopic signature similar to that of the Vogelsberg basanites. The xenoliths equilibrated in narrow temperature intervals typical for each locality (1125, 1025, and 925 °C), with exception of xenoliths from one outcrop, which reveal a bimodal temperature distribution (1050 and 900 °C). The elevation of the thermal condition above that expected for a stable continental shield appears to be the result of mantle uplift and heating due to magma intrusion. The presence of "spinelpyroxene- clusters" interpreted as former garnet suggests the rise of asthenospheric mantle into the lithosphere. The peridotite/magma interaction is deduced from Fe-Ti-metasomatism observed in high-temperature xenoliths (1020-1070 °C) considered as parts of thermal aureoles adjacent to local magma conduits


petrologyperidotite xenolithsmantle upwellingmetasomatismVogelsbergGermany