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Phase and cryptic variation through the ultramafic-mafic cumulates in the Mersín ophiolite (southern Turkey)

Published inOfioliti, vol. 21, no. 2, p. 81-92
Publication date1996
Abstract

Mersin ophiolite, one of the Cretaceous Neo-Tethyan realm in eastern Mediterranean, is situated in the southern part of the Taurus calcareous axis in Turkey. Cumulate rocks, occupying an area approximately 15 km², crop out within the N-S oriented Sorgun valley (Mersin) in the western part of the ophiolitic massif. Cumulates have over 3 km thickness. They start with 800 m of ultramafic rocks at the bottom and continue into 2500 m of gabbroic rocks. They show tectonic contacts with mantle harzburgites at their base and with basaltic rocks at the top. Polycyclic cumulate feature is observed in the mafic and ultramafic cumulate rocks. Ultramafic cumulates, showing adcumulate-heteradcumulate texture, consist mainly of dunite, wehrlite and pyroxenite. Igneous lamination, size grading and rhythmic layering are observed as accumulation features in the ultramafic cumulates. Mafic cumulates, mainly of gabbro, leucogabbro, olivine gabbro and anorthosite, constitute almost 2/3 of the whole cumulate section. Mafic cumulate rocks are fresh and present adcumulate, mesocumuate and orthocumulate texture. Size grading and rhythmic layering are also seen in mafic cumulates. Cryptic variation is small throughout the entire thickness of the layered sequence. Olivine varies from Fo₉₁ to Fo₈₀, clinopyroxene from Mg# 93 to 77, and plagioclase from An₉₅ to An₉₁ through the 3 km vertical sequence. Adcumulate-mesocumulate growth in ultramafic and mafic cumulates indicates slow accumulation rate. Absence of zoning in the cumulus and intercumulus phase suggests a crystallization process bulk equilibrium condition at high temperature as confirmed by high Mg/Fe ratio and high Ca content of the plagioclase.

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Keywords
  • Cryptic-phase variation
  • Cumulate
  • Mersín, Turkey
Citation (ISO format)
PARLAK, Osman, DELALOYE, Michel, BÍNGÖL, Ergüzer. Phase and cryptic variation through the ultramafic-mafic cumulates in the Mersín ophiolite (southern Turkey). In: Ofioliti, 1996, vol. 21, n° 2, p. 81–92.
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Identifiers
  • PID : unige:157647
ISSN of the journal0391-2612
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