gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/002646199548844 Oscillatory Zoned Chrome Lawsonite in the Tavşanlı Zone, Northwest Turkey Sherlock S. C. 1 † Okay A. I. 2 Department of Earth Sciences, The Open University, Milton Keynes, UK ITÜ, Maden Fakültesi, Jeoloji Bölümü, Ayazaga 80624, Istanbul, Turkey

Present address: Geological Survey of Norway, Leiv Eirikssons vei 39, 7491-Trondheim, Norway

 10 1999 63 5 687 692 26 8 1998 9 3 1999 Copyright © 1999, The Mineralogical Society 1999 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