Petrogenesis of strongly peraluminous plutonic rocks of the Eastern Sakarya Zone (Trabzon, Turkey): implications for crustal melting and evolution

Abstract

The Eastern Sakarya Zone in northeastern Turkey contributes for a natural laboratory to study subduction- to collision-related intrusive rocks. This paper presents data on a Carboniferous-aged Duzkoy pluton containing mainly peraluminous granitoids. In addition to plagioclase, K-feldspar and quartz, the rocks include biotite, zircon, apatite and opaque minerals. Sericitization, chloritization, epidotization, and carbonatization are  the main alteration types. The rocks display generally enrichment in large-ion lithophile elements (Rb, Th, U, K), and depletion in high field strength elements (Sr, Nb, Ta, P) in the primitive mantle-normalized trace element diagrams. The Duzkoy samples show mainly light rare earth elements-enriched patterns with marked negative Eu anomalies in the chondrite-normalized rare earth elements diagrams. The compositions of the Duzkoy plutonic rocks are consistent with their origin via partial melting of amphibolites or metagreywackes. Crystal fractionation is also likely an important process in the formation of these rocks. The origin of these rocks could be related to the delamination or slab breakoff processes during the Variscan orogeny.