Orogenic peridotite massifs peridotites

We shall hereafter follow the current terminology. It is convenient to distinguish three main types of mantle occurrences and to examine them in the following sequence (i) orogenic peridotite massifs, (ii) ophiolitic mantle rocks, and (iii) oceanic peridotites. 

Based on their predominant petrological facies and/or on their P-T trajectory before the exhumation, the orogenic peridotite massifs may be subdivided in three main groups ... 

The chemical diversity of mantle pyroxenites is also patent from REE variations. Figure 26 shows the chondrite-normahzed REE patterns of representative pyroxenites from orogenic peridotite massifs in Eastern Pyrenees (Lherz and Freychi-nede) and the Betico-Rifean Belt (Ronda and Beni Bousera). These rocks show variable REE distributions, but some relationships are observed between the structural and/or mineralogical types of pyroxenites and the REE patterns ... 

Figure 26 Chondrite-nomialized abundances of REEs in representative mafic rocks from the Beni Bousera, Ronda, and Pyrenees orogenic peridotite massifs. Data from Bodinier et al. (1987a, 1987b, 1990), Bodinier (1989), Komprobst et al. (1990), Pearson et al. (1993), Remaidi (1993), McPherson (1994), Garrido (1995), McPherson et al. (1996), and Garrido and Bodinier (1999). Normalizing values after Sun and McDonough (1989).

Reisberg L. and Lorand J. P. (1995) Longevity of sub-continental mantle hthosphere from osmium isotope systematics in orogenic peridotite massifs. Nature 376, 159—162. 

The intermediate pressure (IP) orogenic peridotites include several massifs dominantly equilibrated in the spinel ( amphibole, phlogopite) peridotite facies, either in the Ariegite (garnet in mafic layers) or in the Seiland (mafic layers devoid of garnet) subfacies (O Hara, 1967a Obata, 1980). These massifs were generally... 

Western Alps. The LP orogenic peridotites are particularly well exposed in the Alps (Figure 2), where they form several large occurrences of ultramafic rocks (—100 km or more) along the Alpine and North Apennine mountain arc (Figure 2). In general, the massifs underline the sumre zone between the southern Alpine and European plates. The most significant bodies include ... 

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