Collaborative Research: Integrated Structural and Geochemical Investigation of Alternate Origins for 'Crack-Seal' Veins

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0107079 Wiltschko0107064 SharpBanded fibrous veins are common features in deformed rocks, and are classically interpreted to indicate operation of a crack-seal mechanism in which a crack event is immediately followed by a cement-precipitation event due to local pressure drop. However, recent results of mass-balance considerations have cast doubt on this being a valad mechanism. This project will examine the question of the formation of banded veins from a new perspective model that includes two simplifying processes - pressure exerted by growing crystals and geochemical self-organization whereby a nearly constant fluid composition at the vein-host walls leads to oscillations in precipitated species. A series of tests will be applied to veins sets using both geochemical/microthermometric data and textural information to understand chemical and mechanical processes responsible for these types of veins. Results will help improve understanding of vein formation and therefore their use in understanding the tectonic setting in which they formed.