HR: 1340h
AN: T53C-1458    [Abstracts]
TI: A Model For Syntectonic Fibrous Vein Growth Inferred From Microtextures. Ouachitas Orogen, Arkansas
AU: * Cervantes, P
EM: pcervantes@tamu.edu
AF: Texas A&M University, Dept. of Geology and Geophysics Center for Tectonophysics, College Station, TX 77843-3115 United States
AU: Wiltschko, D V
EM: d.wiltschko@tamu.edu
AF: Texas A&M University, Dept. of Geology and Geophysics Center for Tectonophysics, College Station, TX 77843-3115 United States
AB: Veins from the Lower Ordovician Mazarn Formation in the Arkansas' Ouachitas show two processes of vein growth, 1) continuous localized fracturing and filling and 2) recrystallization, tied to the deformation history of the area under study. Evidence for continuous localized fracturing includes the presence of veinlets near or at the vein-host interface. Veinlets are long and narrow features parallel to the main body of the vein, filled mainly with quartz, between 5 and 25 μm wide. Veinlets cut and displaced host grains. Displacement of host grains is evident because the material precipitated on veinlets show different luminescence than host grains. Remnants of these veinlets are observed in completely recrystallized fibers. Evidence for recrystallization includes, 1) wide fibers (more than 100 μm) with fluid inclusion trails parallel to fiber length that span the entire fiber length, 2) luminescence in the central part of the vein is different than luminescence in the external part of the vein (close to host-vein interface), 3) remnants of original luminescence in the central part of the vein suggesting that recrystallization is a later process. We hypothesize that in this region folding followed by flattening gave rise to boudinage of resistant layers accompanying abundant pressure solution providing the vein forming material. Precipitation of material took place along necks of boudins, which fractured repeatedly allowing veins to grow in width and length. Late thrust faults led to open system conditions which gave rise to new vein growth and recrystallization. Recrystallization altered the shape of previously formed veins.
DE: 8005 Folds and folding
DE: 8015 Local crustal structure
DE: 8030 Microstructures
DE: 8045 Role of fluids
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: Fall Meeting 2005