HR: 08:15h
AN: T41G-02    [Abstracts]
TI: Overview of Research on the Origin of Syntectonic Veins
AU: * Wiltschko, D
EM: d.wiltschko@tamu.edu
AF: Texas A&M University, Dept. of Geology and Geohysics, Center for Tectonophysics, College Station, TX 77843-3115 United States
AB: The making of a syntectonic vein requires placing the vein components in a mobile form, transporting them to the vein site and then precipitating them accompanying dilation. The commingling in space and time of dissolution features such as pressure solution cleavage and veins suggest a genetic link. Dissolution has received considerable attention in the literature with regard to cleavage formation. Transport is generally held to be by diffusion; the alternative, advection, leads to mass balance problems in that the amount of fluid needed to precipitate observed vein volumes is huge, with little ancillary evidence of large flow. Coupled dilation and precipitation in veins has received relatively little analytical scrutiny. Competing models include the action of elevated fluid pressure to crack and hold open the rock during precipitation, force of crystallization dilating the rock as the vein grows, and a variety of processes having to do with location in a particular larger structure (e.g., outer arc of a fold hinge). All of these may play a role to one extent or another, depending upon the stage of vein growth. Field evidence from syntectonic vein the Benton Uplift, Ouachitas Mtns, for instance, shows that boundinage in the semi-brittle regime resulted in organized, repeated dilation that scales with the thickness of the competent bed. Several orders of boundinage are present, analogous to orders of folding in layered km-scale folds, leading to a spectrum of vein spacings and lengths. Vein width is controlled by the extent to which beds extended after the individual pinched regions were broken and separated by subsequent deformation of the larger structure.
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8108 Continental tectonics: compressional
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: Fall Meeting 2005