Rutile geochemistry and thermometry of eclogites and associated garnet-mica schists in the Biga Peninsula, NW Turkey

In northwest Turkey, high-pressure metamorphic rocks occur as exotic blocks within the cetmi m lange located on the south of the Biga Peninsula. Rutile chemistry and rutile thermometry obtained from the eclogite and associated garnet-mica schist in the cetmi m lange indicate significant trace element behaviour of subducted oceanic crust and source-rock lithology of detrital rutiles. Cr and Nb contents in detrital rutile from garnet-mica schist vary from 355 to 1026 pzig and 323 and 3319 g/g, respectively. According to the Cr-Nb discrimination diagram, the results show that 85% of the detrital rutiles derived from metapelitic and 15% from metamafic rocks. Temperatures calculated for detrital rutiles and rutiles in eclogite range from 540 degrees C to 624 degrees C with an average of 586 degrees C and 611 degrees C to 659 degrees C with an average of 630 degrees C at P = 2.3 GPa, respectively. The calculated formation temperatures suggest that detrital rutiles are derived from amphibolite- and eclogite-facies metamorphic rocks. Amphibolite-facies rocks of the Kazdag Massif could be the primary source rocks for the rutiles in the garnet-mica schist from the cetmi m lange. Nb/Ta ratios of metapelitic and metamafic rutiles fall between 7-24 and 11-25, respectively. Nb/Ta characteristics in detrital rutiles may reflect a change in source-rock lithology. However, Nb/Ta ratios of rutiles in eclogite vary from 9 to 22. The rutile grains from eclogites are dominated by subchondritic Nb/Ta ratios. It can be noted that subchondritic Nb/Ta may record rutile growth from local sinks of aqueous fluids from metamorphic dehydration. (C) 2017 Elsevier GmbH. All rights reserved.