Constraints on the evolution of the Mesohellenic Ophiolite from subophiolitic metamorphic rocks
Published:August 01, 2011
R. Myhill, 2011. "Constraints on the evolution of the Mesohellenic Ophiolite from subophiolitic metamorphic rocks", Mélanges: Processes of Formation and Societal Significance, John Wakabayashi, Yildirim Dilek
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Narrow, discontinuous bands of high-grade subophiolitic metamorphic rocks, comprising predominantly amphibolite facies metabasites with rare metasediments, are observed at the contact between the complexes and subjacent mélanges of the Mesohellenic Ophiolite exposed in northwestern Greece.
Both conventional and pseudosection thermobarometry have been used to yield estimated peak pressure-temperature (P-T) conditions of these tectonic sheets. Toward the leading edge of the ophiolite, subophiolitic rocks of the Vourinos Complex record peak metamorphic temperatures of 770 ± 100 °C. Pressures of 4 ± 1 kbar beneath the Vourinos are estimated on the basis of hornblende composition and are similar to the expected pressures from ophiolitic overburden.
Beneath the exposed Dramala Complex, at the trailing edge of the ophiolitic body southwest of the Vourinos, estimated temperatures reached 800 ± 40 °C and 12.00 ± 1.27 kbar at the top of an apparent inverted metamorphic gradient imposed by discrete phases of accretion. High pressure assemblages beneath ophiolitic bodies imply exhumation relative to the overlying ophiolite. Estimated homologous temperatures in the upper plate are similar to those inferred for channeled exhumation during continental collision.
Mineral assemblages lower in the Dramala sole indicate reduced temperatures and peak pressures. Similar pressures obtained within lower temperature sole rocks beneath Vourinos and Pindos suggest that a shallowly dipping thrust may have been responsible for obduction. Peak temperatures and pressures are in agreement with those estimated for secondary thrust propagation beneath a proto-arc after subduction in an intra-oceanic setting.