Abstract

Blueschist-facies metabasite rocks from the Tavsanli Zone of northwest Turkey have been found to contain an abundance of lawsonite displaying oscillatory zoning. Lawsonite normally adheres to the ideal composition of CaAl 2 [Si 2 O 7 ](OH)2.H 2 O. In two samples from the Tavsanli Zone, Al (super 3+) -Cr (super 3+) substitution has occurred. The Cr (super 3+) 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.

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