HR: 09:30h
AN: T21D-06    [Abstracts]
TI: The behavior of monazite in pelitic assemblages from Menderes Massif, western Turkey: Implications for timing and deciphering rates of extension
AU: * Catlos, E J
EM: ej.catlos@okstate.edu
AF: Oklahoma State University, School of Geology 105 NRC, Stillwater, OK 74078, United States
AU: Baker, C B
EM: b.baker@okstate.edu
AF: Oklahoma State University, School of Geology 105 NRC, Stillwater, OK 74078, United States
AU: Sorensen, S S
EM: SorensenS@si.edu
AF: Smithsonian Institution Museum of Natural History, PO Box 37012, MRC 119, Washington, DC 20013-7012, 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 (Western Turkey) is one of several Aegean metamorphic core complexes, and understanding the geochronologic and thermobarometric history of its rocks provides information about the large- scale geodynamic processes that facilitate extension in the Earth's lithosphere. The region experienced compression during the Cambro-Ordovician and Eocene, followed by large-scale extension during the Oligocene. Here, we apply in situ ion microprobe monazite (REEThPO₄) dating of garnet-bearing pelites in an attempt to constrain the timing of extension in the Menderes Massif. Rocks exposed in the core complex rarely yield monazite ages consistent with a single population, ranging from the Cambro-Ordovician to Pliocene. As a further complication for extensional settings, the temperature of monazite crystallization in pelites can range from very low diagenetic to ultra-high conditions. These monazites also contain more common Pb than is usually present in the mineral. Monazite may form a variety of reactants, including rare-earth carbonates or oxides, allanite, even garnet. The presence of monazite in pelitic assemblages from the Menderes Massif does not appear related to the major or trace element chemistry of the rocks. As an extreme example, monazite inclusions in garnet in one sample are as much as 400 m.y. different than those in the matrix, suggesting non-equilibrium conditions and problematic P-T calculations. Cathodoluminescence images of the dated pelites show evidence for fluid flow that could have triggered dissolution-reprecipitation reactions for monazites not armored by garnet. Correlating the timing of tectonic events in the Menderes Massif to those occurring in metamorphic core complexes elsewhere in the Aegean is difficult without the use of other dating techniques, and confidence that minerals involved in thermobarometric calculations experienced equilibrium conditions.
DE: 1100 GEOCHRONOLOGY
DE: 1194 Instruments and techniques
DE: 3660 Metamorphic petrology
DE: 8109 Continental tectonics: extensional (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting