Latitude: 39°27'N
Longitude: 31°34'E
The Sivrihisar Massif is comprised of blueschist and eclogite facies metasedimentary and metabasaltic rocks. Abundant metre- to centimetre-scale eclogite pods occur in blueschist facies metabasalt, marble and quartz-rich rocks. Eclogites and blueschists have similar bulk composition, but record different P-T conditions: ∼26 kbar, 500°C (lawsonite eclogite); 18 kbar, 600°C (epidote eclogite); 12 kbar, 380°C (lawsonite blueschist); and 15-16 kbar, 480-500°C (lawsonite-epidote blueschist). Pressures for the Sivrihisar lawsonite eclogite are among the highest reported for this rock type, which is rarely exposed at the Earth's surface. Some rocks were metamorphosed entirely within the lawsonite stability field.
Regionally metamorphosed, muscovite-bearing quartzites contain coexisting andalusite, kyanite, and sillimanite. Textural relations and relative deformation features among the three polymorphs suggest the crystallization sequence andalusite-kyanite-sillimanite. The stable coexistence of staurolite + sillimanite at peak metamorphic conditions suggests a maximum pressure of 5.5 kbar. The three polymorphs grew sequentially along a clockwise P-T path that looped around the Al2SiO5 triple point during incipient subduction of a continental margin sequence.
References
- Whitney, D.L. (2002): Coexisting andalusite, kyanite, and sillimanite: Sequential formation of three Al2SiO5 polymorphs during progressive metamorphism near the triple point, Sivrihisar, Turkey. American Mineralogist 87, 405-416.
- Davis, P.B., and Whitney, D.L. (2006): Petrogenesis of lawsonite and epidote eclogite and blueschist, Sivrihisar Massif, Turkey. Journal of Metamorphic Geology 24(9), 823-849.
- Çetinkaplan, M., Candan, O., Oberhänsli, R., and Bousquet, R. (2007): Pressure–temperature evolution of lawsonite eclogite in Sivrihisar; Tavşanlı Zone–Turkey. Lithos 104(1-4), 12-32.
- Mineralogical Magazine 1997 61 : 835-843
Mineral List
14 entries listed. 12 valid minerals.
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