Oscillatory Zoned Chrome Lawsonite in the Tavşanlı Zone, Northwest Turkey

S. C. Sherlock1, † and A. I. Okay2
1 Department of Earth Sciences, The Open University, Milton Keynes, UK
2 ITÜ, Maden Fakültesi, Jeoloji Bölümü, Ayazaga 80624, Istanbul, Turkey
Present address: Geological Survey of Norway, Leiv Eirikssons vei 39, 7491-Trondheim, Norway

Abstract: Blueschist-facies metabasite rocks from the Tavşanlı Zone of northwest Turkey have been found to contain an abundance of lawsonite displaying oscillatory zoning. Lawsonite normally adheres to the ideal composition of CaAl2[Si2O7](OH)2.H2O. In two samples from the Tavşanlıt Zone, Al3+-Cr3+ substitution has occurred. The Cr3+ was probably present in the protolith as magmatic chromite, became incorporated into lawsonite during subduction, and is a metamorphic feature resulting from quantities of Cr in the protolith and local fluid conditions.

Keywords: lawsonite • oscillatory zoning • metamorphic rocks • Tavşanlıt zone • Turkey

Mineralogical Magazine; October 1999 v. 63; no. 5; p. 687-692; DOI: 10.1180/002646199548844
© 1999, The Mineralogical Society
Mineralogical Society (www.minersoc.org)