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Turkish Journal of Earth Sciences

DOI

-

Abstract

The Eocene Saraycık granodiorite, eastern Pontides, Turkey, is a small post-tectonic intrusive body (~11 km2), cross-cutting tectonically juxtaposed distinct metamorphic and non-metamorphic lithologies. A ~0.8 to 1-km-wide contact-metamorphic aureole has developed around the intrusion. Disequilibrium is prevalent in all lithologies, even in the inner zones of the contact aureole. Conditions of contact metamorphism are estimated by simple phase equilibria applied to microdomains in the metapelitic lithologies without obvious signs of disequilibrium: Shallow emplacement depths (0.21±0.05 GPa = ~5-8 km) are suggested by contact-metamorphic mineral assemblages (e.g., andalusite + corundum + K-feldspar), by Al-in-hornblende barometry on granodiorite and by partial melting within the stability field of andalusite near the intrusive contact. Peak temperatures during the contact metamorphism ranged from 430-520 ºC at the outer domains of the aureole (~400 m from the intrusive contact) to >=730 ºC at the immediate contact of the intrusion. Textural evidence for partial melting in the stability fields of both andalusite and sillimanite are observed in metapelitic lithologies at distances £30 m from the intrusive contact. Basic lithologies contain mostly foliation-parallel, 2-50-mm-thick layers with skarn-like mineralogy, which probably formed via infiltration of chemically reactive fluids. Prevalence of disequilibrium is predominantly related to temporal variation in temperature and/or fluid composition attending the contact metamorphism, rather than to the presence of some relict minerals from a pre-contact-metamorphic stage.

Keywords

contact metamorphism, disequilibrium, andalusite + melt stability, P-T estimates, Saraycık granodiorite, eastern Pontides, Turkey

First Page

75

Last Page

94

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