EXHUMATION AND STRUCTURAL EVOLUTION OF HIGH PRESSURE BLUESCHISTS ALONG A TETHYAN SUTURE ZONE IN ORHANELI, BURSA PROVINCE, TURKEY

The Izmir-Ankara suture, including blueschist facies rocks near Orhaneli in Bursa Province, Turkey, formed during the mid-Cretaceous. Extensive exposures of lawsonite blueschist, graphitic mica schist, white mica schist, and marble there indicate high-pressure and low-temperature conditions of formation. In addition to the blueschist facies rocks, mélange of an accretionary complex, including radiolarian chert, greenstone and serpentinite is present. Locally, large masses of quartz separate blueschist facies marble from mantle peridotite, mainly dunite and harzburgite, have an Albian age. Minor Eocene granodiorite bodies are also present. Diabase dikes within the peridotite units trend generally E-W. The original composition of the dikes (plagioclase, hypersthene, pyrite and sphene) is altered to clay, secondary hornblende, albite and minor biotite indicative of greenschist metamorphism. Schistosity within the high-pressure rocks generally strikes north although elongated marble pebbles within white mica schist and mineral elongation lineations within the lawsonite blueschist trend NNW. A younger deformation event is indicated by NW-SE trending, sub-horizontal slickenlines on left lateral strike slip faults. A better understanding of the kinematics will be attempted using oriented samples taken during the 2010 field campaign. We will also study detailed chemical analyses of representative minerals from selected rock samples in order to reveal metamorphic conditions. Together these field and laboratory will be integrated to attempt a kinematic and temporal model to help explain how blueschist-grade rocks were exhumed from approximately 80 km and juxtaposed against both accretionary deposits and mantle material. The purpose of this study is to better understand the exhumation mechanisms of the high pressure low temperature rocks.