Mineral records of the pyroxenites formed within harzburgites (Ulaş, Sivas, Turkey): implications on petrogenesis and tectonic setting

Abstract

In this article, the petrological processes of the clinopyroxenite dykes and host peridotites occurring in Ulaş District (Sivas,mid-Anatolia, Turkey) are discussed. The new geochemical data from major minerals in the clinopyroxenite dykes and host harzburgitesrevealed differences to the supra-subduction zone (SSZ)-type pyroxenites and peridotites. In particular, the NiO content of olivinesin the host harzburgites showed the signature of the mantle, whereas rare olivines of the clinopyroxenites had a NiO content and Fonumber that were inferior to those of mantle peridotites. The high Mg-number of clinopyroxenes in the clinopyroxenites was likelyassociated with the partial remelting of the host harzburgites. Additionally, the rare earth element pattern of clinopyroxenes from thestudied clinopyroxenites exhibited a similar pattern to those of the other SSZ or fore-arc clinopyroxenes. Additionally, the low Mgnumber and relatively high Cr-number of spinels in the clinopyroxenites showed similarity to the subduction-related origin. Based ontextural and geochemical evidence, the harzburgites were interpreted as depleted mantle rock, which was modified by melt-peridotiteinteractions. Consequently, the pyroxenites likely occurred as a crystallizing or cumulative zone of the SSZ-type melt and the mineralswere gained from partial melting of the harzburgites through the interaction with such magma.