Paper No. 6
Presentation Time: 8:00 AM-6:00 PM
EXHUMATION OF MEDIUM-PRESSURE AMPHIBOLITE WITHIN A HIGH-PRESSURE REGION: THE IZMIR-ANKARA SUTURE, ORHANELI AREA, TURKEY
GARRAFFA, Alfred1, TERRY, Michael P.
2, LISENBEE, Alvis L.
3 and YILDIZ, Umit
3, (1)Geology and Geological Engineering, South Dakota School of Mines and Technology, 501 East Saint Joseph Street, Rapid City, SD 57701, (2)Department of Geology and Geological Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57702, (3)Dept. of Geology and Geological Engineering, South Dakota School of Mines and Technology, 501 E. St. Joseph St, Rapid City, SD 57701, alfred.garraffa@mines.sdsmt.edu
The Tavsanli zone of high-pressure metamorphic rocks lies at the northern, subducted margin of the Anatolide-Tauride block within the Izmir-Ankara suture. Near the town of Orhaneli, blueschist facies rocks composed of blue schist, likely meta-basalt, marble, graphitic schist, and white mica schist are juxtaposed against dunite, harzburgite, and serpentine of the Burhan peridotite complex, the latter of apparent sub-oceanic mantle origin. Near the peridotite contact a unit composed of garnet, hornblende and plagioclase amphibolite, as well as a Na-amphibole-bearing schist (also composed of sub-euhedral almandine-pyrope garnet, phengite, paragonite, zoisite, rutile and quartz) is shown by detailed mapping to be enclosed within the peridotite. The unit is east-trending, and 1050 m by 115 m in extent. Based upon preliminary petrographic studies, this unit formed under medium-grade conditions of metamorphism. The fabric, defined by elongate amphibolite grains as well as the alignment of mica grains, is clearly visible in both thin section and hand samples, and there are several kinematic indicators, such as pulled apart garnets.
This field and laboratory study examines the amphibolite and surrounding units to determine the emplacement mechanism by which lower-pressure metamorphic rock came in contact with those formed at significantly higher pressures. We will examine the mineralogy and texture of the samples, and obtain chemical data from the SEM and microprobe in order to calculate metamorphic conditions for all units within the area, with emphasis on the amphibolite. A significant aspect will be determination of the kinematics using oriented samples and structural data obtained from field mapping during the 2010 field season. The amphibolite shows a N-S fabric which contrasts with the more NE-SW fabric present in the surrounding units. Previous studies interpreted the amphibolite to be emplaced by southward thrusting. Recently collected hand specimens, however, appear to have top-to-the-north, sigma-type garnet porphyroblasts, possibly resulting from regional extension. Further analytical work should constrain the metamorphic history of the unit and provide insight into the emplacement of amphibolite facies rock within mantle material adjacent to the blue schist facies terrane.
