Pyrenees peridotites

Interesting differences in sulfur isotope compositions are observed when comparing high-S peridotitic tectonites with low-S peridotite xenoliths (Fig. 3.7). Tec-tonites from the Pyrenees predominantly have negative 5 " S-values of around —5%c, whereas low-S xenoliths from Mongoha have largely positive 8 S-values of up to - -l%o. Ionov et al. (1992) determined sulfur contents and isotopic compositions in... 

An overall description of the peridotite bodies may be found in Fabrics et al. (1991), completed by Fabrics et al. (1998) for the central and western Pyrenees. These papers also synthetize our knowledge on the origin and evolution of Pyrenean peridotites and related rocks. The peridotite... 

Peridotite fertilization may also result from the fractional solidihcation of exotic (deep-seated) melts inhltrated in wall rocks of translithospheric magma conduits. This process was hrst described in composite mantle xenoliths (Wilshire and Shervais, 1975 Gurney and Harte, 1980 Irving, 1980 Wilshire et al., 1980 Boivin, 1982 Harte, 1983 Harte et al, 1993 Menzies et ah, 1987), where it is referred to as modal metasomatism when new (generally hydrous) minerals are precipitated (Dawson, 1984 Kempton, 1987), or Fe-Ti metasomatism (Menzies et al., 1987) when the attention is focused on chemical enrichment. In contrast with ultramafic xenoliths, the tectonically emplaced and oceanic peridotites contain only sparse rock types attributable to mantle metasomatism by deep-seated melts. Examples of wall-rock, modal, and Fe-Ti metasomatism were nevertheless described in IP orogenic Iherzolites, notably in the Pyrenees (Fabrics et al., 1989 Bodinier et al., 1988, 1990, 2003 McPherson et al., 1996 Woodland et al., 1996). 

Figure 12 Chondrite-normalized abundances of REEs in representative unmetasomatized orogenic peridotites from Ronda, Pyrenees, and Lanzo (whole-rock analyses). Data from Bodinier (1988, 1989, unpublished), Bodinier et al. (1988), Remaidi (1993), GerviUa and Remai di (1993), McPherson (1994), McPherson et al. (1996), and Fabrics et al. (1998). Normalizing values after Sun and McDonough (1989).

Figure 14 Chondrite-normalized abundances of REEs in metasomatized orogenic peridotites from the Eastern Pyrenees (whole-rock analyses). Data from Bodinier et al. (1988, 1990) and Fabries et al. (1989). Normalizing values...

Figure 22 Chondrite-normalized abundances of REEs in cUnopyroxene separated from representative peridotite samples from the Fontete Rouge massif, in the Eastern Pyrenees (Downes et al., 1991). Normalizing values after...

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 30 Simplified geological map of the Lherz orogenic peridotite (Eastern Pyrenees), after Conquere (1978) and Monchoux (unpublished data), showing the hazburgite layering concordant with peridotite foliation. Based on their enriched Nd-Sr isotopic composition (e.g., Downes et al, 1991), the harzburgite layers are interpreted as residual strips of aged, isotopically enriched, but refractory, mantle lithosphere, embedded into younger, depleted but fertile, asthenospheric mantle (spinel Iherzolites). This marble cake stmcture is tentatively ascribed to thermomechanical erosion of lithospheric mantle by upwelling asthenosphere.

Ave LaUemant H. G. (1967) Structural and petrographic analysis of an Alpine-type peridotite the Iherzolite of the French Pyrenees. Leid. Geol. Med. 42, 1 -57. 

Conquere F. and Fabries J. (1984) Chemical disequilibrium and its thermal significance in spinel peridotites from the Lherz and Freychinede ultramafic bodies (Ariege, French Pyrenees). In Kimberlites II. The Mantle and Crust-Mantle Relationships (ed. J. Kornprobst). Elsevier, Amsterdam, The Netherlands, pp. 319-331. 

Lacroix A. (1917) Les peridotites des Pyrenees et les autres roches intrusives non feldspathiques qui les accompagnent. C. R. Acad. Set Paris 165, 381-387. 

Lx)rand J.-P., Bodinier J.-L., Dupuy C., and Dostal J. (1989) Abundances and distribution of gold in the orogenic-type spinel peridotites from Ariege (Northeastern Pyrenees, France). Geochim. Cosmochim. Acta S3, 3085—3090. 

Mukasa S. B., Shervais J. W., Wilshire H. G., and Nielson J. E. (1991) Intrinsic Nd, Pb and Sr isotopic heterogeneities exhibited by the Lherz alpine peridotite massif, French Pyrenees. In Orogenic Lherzolites and Mantle Processes. Spec. Vol. J. Petrol, (eds. M. A. Menzies, C. Dupuy, and A. Nicolas). Oxford University Press, Oxford, UK, pp. 117-134. 

Lorand J. P. (1989) Mineralogy and chemistry of Cu-Fe-Ni sulfides in mantle-derived spinel peridotite bodies from Ariege (northeastern Pyrenees, France). Contrib. Mineral. Petrol. 103, 335-345. 

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