Evolution of the Upper Mantle beneath the Pyrenees: Evidence from Orogenic Spinel Lherzolite Massifs

Petrology, Mineral and Isotope Geochemistry of the External Liguride Peridotites (Northern Apennines, Italy)

“…They are particularly abundant within the Suvero and Mt Aiona bodies. On the basis of petrographic and petrological studies, these pyroxenites have been interpreted (Piccardo, 1976;Rampone, 1987) as high-pressure cumulates from basaltic melts, in agreement with the interpretation of mafic layers in orogenic subcontinental-type peridotites and pyroxenite xenoliths in alkaline basalts (Bodinier et al, 1987;Menzies & Hawkesworth, 1987;Fabries et al, 1991).…”

High-temperature metamorphism during extreme thinning of the continental crust: a reappraisal of the North Pyrenean passive paleomargin

“…For the eastern NPZ peridotites, Fabriès et al (1991) identified a single and rapid decompression and cooling step attributed to their ascent from 50-45 km depth to the surface. In contrast, for the western NPZ peridotites, Fabriès et al (1998) identified a slower decompression and cooling from 25-15 km depth up to the surface (see Fig.…”

Orogenic, Ophiolitic, and Abyssal Peridotites

“…In this respect, the current terminology diverges from the distinction made by Den Tex. The well-known Lherz peridotite body in the French Pyrenees is now viewed as a typical 'orogenic lherzolite' massif, considered to represent subcontinental lithospheric mantle (Fabriès et al, 1991), whereas it was classified by Den Tex as an 'ophiolitic peridotite' ('¼truly Alpine-type peridotite').…”

“…Further exceptions are the HP and ultrahigh-pressure (UHP) garnet peridotites that display a range in composition from dunites to pyroxenites, through harzburgites and lherzolites. The orogenic peridotites vary in size from small blocks (1-10 m) embedded in metamorphic sediments (e.g., some of the Pyrenean lherzolites, see Table 1 in Fabriès et al, 1991) to large ultramafic exposures (up to 300 km 2 ) forming the main body of overthrusted tectonic units (e.g., the Ronda massif, southern Spain - Tubia and Cuevas, 1986). However, the vast majority of the lherzolite massifs are intermediate in size between these extremes.…”

“…The metasomatic features may partly overprint the deformation. In Lherz, for instance, the amphibole-pyroxenite veins crosscut the mafic layering (Wilshire et al, 1980) and are incompletely transposed in the peridotite foliation (Fabriès et al, 1991;Vétil et al, 1988).…”