HR: 0800h
AN: T31C-0590    [Abstracts]
TI: Deciphering monazite ages in the Menderes Massif in Western Turkey, using cathodoluminescence, electron microprobe and ion microprobe techniques
AU: * Baker, C B
EM: b.baker@okstate.edu
AF: Oklahoma State University, School of Geology 105 NRC, Stillwater, OK 74078, United States
AU: Catlos, E J
EM: ej.catlos@okstate.edu
AF: Oklahoma State University, School of Geology 105 NRC, Stillwater, OK 74078, United States
AU: Sorensen, S S
EM: sorenesens@si.edu
AF: Smithsonian Institution Museum of Natural History, PO Box 37012, MRC 119, Washington, DC 20013, United States
AU: Cemen, I
EM: ibrahim.cemen@okstate.edu
AF: Oklahoma State University, School of Geology 105 NRC, Stillwater, OK 74078, United States
AB: The Menderes Massif is a key Aegean metamorphic core complex, exposing over 40,000 km² of metamorphic and igneous rocks via large-scale extension. Granites cut by the Alasehir detachment surface, which bounds the northern edge of the core complex, contain monazite grains than range from 9.6±1.6 Ma to 21.7±4.5 Ma (±1σ). The grains were dated in thin section using an ion microprobe (Th-Pb). To understand the reason for the ~10 m.y. discrepancy, we applied backscattered and secondary electron imaging, cathodoluminescence (CL), and X-ray element (REE, Th, Y, Ca) mapping. Monazite does not luminesce, however surrounding minerals show CL evidence of fluid flow that indicate the likelihood of dissolution/reprecipitation reactions and aid in the interpretation of the monazite ages. The CL images show the granites contain plagioclase with corroded cores and distinct rims, and quartz in some samples show evidence for brecciation and subsequent recrystallization. Feldspars are not only zoned in CL from core to rim, but also show differences in color along twin planes. Radiation haloes surround many monazite grains. The CL was also useful for identifying shear sense indicators not always seen using light microscopy or electron microprobe imaging. The dated monazite grains are chemically zoned, but the mineral's composition does not always represent a different age. The granites visibly range in degree of alteration, depending on their proximity to the Alasehir detachment. Whole and trace element rock chemistry from the granites show they experienced a complicated magmatic history, consistent with the CL images. The combination of electron microprobe, ion microprobe and CL techniques are useful for deciphering the complicated history of the granites exposed along the Alasehir detachment, and can be applied to elsewhere to regions that have experienced a polyphase magmatic and tectonic history.
DE: 1100 GEOCHRONOLOGY
DE: 1194 Instruments and techniques
DE: 8109 Continental tectonics: extensional (0905)
DE: 8178 Tectonics and magmatism
SC: Tectonophysics [T]
MN: 2007 Fall Meeting