Geochronological and geochemical constraints and origin of the Tavşanlı Zone plutonic rocks (NW Turkey)

Abstract

In the Tavşanlı Zone, the Eocene magmatism led to NW-SE trending plutons located just south of the İzmir-Ankara-Erzincan Suture Zone in Turkey. The Middle Eocene-aged Günyüzü Intrusive Complex (Karacaören, Tekören, Dinek, Kadıncık) is one of these plutonic rocks and has metaluminous to peraluminous, medium-K calc-alkaline to shoshonitic and mainly I-type granite characteristics. The plutonic rocks consist of mainly granodiorite and granite, and their mafic microgranular enclaves are widespread in these rocks. Mineral assemblages in the host rocks and enclaves also are quite similar (quartz, plagioclase, K-feldspar, biotite, and hornblende), but the latter are more enriched in mafic minerals. The enclaves have disequilibrium textures such as oscillatory zoning and resorbed rims, indicating magma mixing/mingling. In the chondrite-normalized REEs patterns of the plutonic rocks are moderately fractionated and have small negative Eu anomalies. They are enriched in LILEs and LREEs relative to HFSEs, showing characteristics of subductionrelated granitoids. The enclaves also have similar geochemical characteristics, indicating equilibration between the mafic and felsic magmas. Whole-rock geochemical data show that the parental magmas in the Günyüzü area were produced by partial melting from mafic crustal rocks and also magma mixing/mingling from enriched lithospheric mantle. Slab break-off is the likely mechanism for the initiation of the postcollisional magmatism in the Tavşanlı Zone.