Oscillatory zoned chrome lawsonite in the Tavsanli Zone, northwest Turkey

Blueschist-facies metabasite rocks from the TavSanli Zone of northwest Turk ey have been found to contain an abundance of lawsonite displaying oscillat ory zoning. Lawsonite normally adheres to the ideal composition of CaAl2[Si 2O7](OH)(2). H2O. In two samples from the Tavsanli Zone, Al3+-Cr3+ substitu tion has occurred. The Cr3+ was probably present in the protolith as magmat ic chromite, became incorporated into lawsonite during subduction, and is a metamorphic feature resulting from quantities of Cr in the protolith and l ocal fluid conditions.