INTERNATIONAL GEOLOGY REVIEW, cilt.48, ss.420-442, 2006 (SCI İndekslerine Giren Dergi)
Platinum-group-clement (PGE) studies of peridotites from the: supra-subduction zone (SSZ) ophiolites of northwest Anatolia provide evidence for the nature of melt extraction within the uppermost mantle, and interactions between subduction-related magma and oceanic lithosphere. The peridotite samples from the mantle section of the ophiolites are mainly spinel-harzburgites and dunites, accompanied by subordinate amounts of spinel-Iherzolite. Whole-rock major-trace. element and mineral chemical characteristics indicate that the peridotites originated as the solid residues of varying degrees of partial Inciting (similar to 5 to similar to 20%), and were subsequently modified by interaction with metasomatizing melts. The samples have non-chondritic, fractionated chondrite-normalized PGE patterns. Melt-depleted (e.g., low Al2O3 and CaO contents) mantle harzburgites and dunites show moderate to strong enrichments in the palladium group relative to the iridium group PGEs (Pd-N/Ir-N = 1.81 +/- 0.23; N = Cl-chondrite normalized), and in most samples, pronounced Rh and Pd enhancements relative to Pt (Rh-N/Pt-N = 2.31 +/- 0.66; Pd-N/Pt-N = 7.93 +/- 0.20). These signatures cannot be reconciled with a simple in situ melt extraction and removal of sulfide phases, but most likely reflect a multi-stage petrogenetic process that selectively enriched the local mantle environment in incompatible and less refractory siderophile elements that are mobilized during continuous melt percolation, while relatively depleting the mantle wedge in Pt, which was not as effectively mobilized by silicate melts (or fluids).