Melt-rock interactions

An alternative to this scenario is to envisage that some fertile orogenic Iherzolites have acquired their geochemical signature as a result of melting and melt-rock interaction processes associated with the thermomechanical erosion of lithospheric mantle by upweUing asthenosphere (e.g., Lenoir et al., 2001). In this scheme, refertilization of lithospheric peridotites by (and reequilibration with) MORB melts is an alternative to the small degrees of melt extraction to account for LREE depletion in otherwise fertile Iherzolites (e.g., Piccardo and Rampone, 2001). 

HIE and LREE enrichment due to melt rock interactions were advocated by Parkinson and Pearce (1998), and Pearce et al. (2000) for abyssal peridotites from forearc (Izu-Eonin-Mariana) and arc-basin (South Sandwich). In these rocks, however, interaction between arc magmas and pre-existing lithospheric peridotites may signihcantly contribute to the enrichment, hence resulting in a complex geochemical signature (Pearce et al., 2000). 

As it provides easy access to a variety of metasomatized mantle rocks, the Lherz massif has been recently the focus of detailed geochemical studies—as well as the source of debates—concerning melt infiltration and melt-rock interaction processes in wall rocks of... 

Bedini R. M., Bodinier J.-L., and Vernieres J. (2003) Numerical simulation of Ee—Mg partitioning drrring melting and melt-rock interactions in the upper mantle. In EGS— AGU—EUG Joint Assembly, Nice, Erance. 

Seyler M. and Bonatti E. (1997) Regional-scale melt-rock interaction in Iherzolitic mantle in the Romanche fracture zone (Atlantic Ocean). Earth Planet. Sci. Lett. 146, 273-287. 

Philippot P. (1993) Fluid-melt-rock interaction in mafic eclogites and coesite-bearing metasediments constraints on volatile recycling during subduction. Chem. Geol 108, 93-112. 

Fig. 4. Fractionation of PGE pattern (Pd/Ir)n v. AI2O3 for progressive melt removal and the effects of sulphide addition as a result of melt-rock interaction. Calculation of the melting trends follows the method of Lorand et al. (1999). Tick marks denote 5% melting intervals. The two curves shown depict starting compositions with 250 ppm (model 1) and 300 ppm (model 2) total sulphur. The trends terminate when residual sulphide disappears at 25 and 30% melting, respectively. The sulphide addition trends are general trends taken from Rehkamper et al. (1999).

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