Evidence of Eocene high-temperature/high-pressure metamorphism of ophiolitic rocks and granitoid intrusion related to Neotethyan subduction processes (Doğanşehir area, SE Anatolia)

Abstract

Abstract New data for regionally important granulite facies metaophiolitic rocks and cross-cutting granitoids rocks are presented and discussed. The high-temperature/high-pressure Berit metaophiolite is cut by unmetamorphosed Eocene (51–45 Ma) granitoid rocks. The highest metamorphic grade occurs in blocks of mafic granulites. Enveloping amphibolite facies rocks reflect retrograde metamorphism related to exhumation. Sm–Nd (pyroxene–garnet–amphibole–whole rock) isochron ages of 52–50 Ma for the granulite facies rocks are interpreted to represent the time of cooling of the granulite facies rocks. The over-riding Malatya metamorphic unit to the north is also intruded by Eocene granitoid rocks. The granulite facies metamorphism of the meta-ophiolitic rocks is inferred to have formed in the roots of an Eocene magmatic arc, with accentuated heat flow being provided by subduction of a spreading ridge, or rupture of the subducting slab. The high-temperature/high-pressure metamorphism was followed by exhumation, as indicated by field structural relations and the evidence of retrograde metamorphism. The Eocene arc magmatism can best be explained by northward subduction of the Southern Neotethys, which persisted after the time of latest Cretaceous regional ophiolite emplacement until the collision of the Eurasian (Anatolian) and Arabian continents during the Early–Mid Miocene. Subsequent Plio-Quaternary left-lateral strike-slip strongly affected the area. Supplementary-material: Four supplementary tables giving the whole rock geochemistry of the granitoids, mineral geochemistry of the granulite facies rocks, LA-MC-ICP-MS zircon U–Pb data belonging to granitoids and Sm–Nd data belonging to granulite facies rocks and two documents giving the detailed analytical procedures and detailed petrography of the granitoids are available at www.geolsoc.org.uk/SUP18588