Abstract
The Edessa ophiolite complex of northern Greece consists of remnants of oceanic lithosphere emplaced during the Upper Jurassic-Lower Cretaceous onto the Palaeozoic-Mesozoic continental margin of Eurasia. This study presents new data on mineral compositions of mantle peridotites from this ophiolite, especially serpentinised harzburgite and minor lherzolite. Lherzolite formed by low to moderate degrees of partial melting and subsequent melt-rock reaction in an oceanic spreading setting. On the other hand, refractory harzburgite formed by high degrees of partial melting in a supra-subduction zone (SSZ) setting. These SSZ mantle peridotites contain Cr-rich spinel residual after partial melting of more fertile (abyssal) lherzolite with Al-rich spinel. Chromite with Cr# > 60 in harzburgite resulted from chemical modification of residual Cr-spinel and, along with the presence of euhedral chromite, is indicative of late melt-peridotite interaction in the mantle wedge. Mineral compositions suggest that the Edessa oceanic mantle evolved from a typical mid-ocean ridge (MOR) oceanic basin to the mantle wedge of a SSZ. This scenario explains the higher degrees of partial melting recorded in harzburgite, as well as the overprint of primary mineralogical characteristics in the Edessa peridotites.
Highlights
Ophiolites are fragments of oceanic lithosphere that have been emplaced tectonically along continental margins in accretionary prisms during orogenic processes
The lhezolite is considered as the product of a first stage melting that occurred probably in a mid-ocean ridge environment
Harzburgites were formed by more complicated processes including higher degrees (12–20%) of melting and additional modification by melt-rock interaction, in a supra-subduction zone (SSZ) environment
Summary
Ophiolites are fragments of oceanic lithosphere that have been emplaced tectonically along continental margins in accretionary prisms during orogenic processes. The chemical composition of ophiolitic rocks is commonly used for recognising a variety of different tectonic settings, as well as the nature of mantle sources These tectonic settings include oceanic spreading centers, hot spots, backarc and forearc basins (supra-subduction zone environments), arcs and other extensional magmatic settings including those in association with plumes [3,7,8,9,10,11,12]. They provide information about magmatic, metamorphic and tectonic processes of the oceanic crust and upper mantle [3,13,14]. Mantle rocks of ophiolitic origin provide significant information for the paleotectonic evolution of the oceanic
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