Volume Strain, Mass Transfer, and Fabric Development in Carbonates

NSF funded (EAR9316809) combination of geometrical (3D finite strain) and geochemical (major and trace element and stable isotope) techniques provides evidence for contemporaneous, volume loss (up to 50%) with metasomatic processes in localized deformation zones leading to the formation of cleavage in carbonate rocks. Within deformation zones, cleavage is associated with (1) increased strain which evolved from plane to prolate shapes, (2) increased volume losses (20-50%; at the 1cm3-scale, (3) passive concentration of some elements (Na, P, Fe, Mg) but metasomatic additions (Ti, Al, K, Si) and subtractions (Ca) of others, (4) neocrystallization of illite, kaolinite,     anatase, and quartz in selvages, and (5) increased fluid infiltration and isotopic exchange with increased strain and fabric development. Volume strains balance on scales larger than a few 100s m even though carbonate thrust sheets were flushed with meteoric water to15 km depth in the Idaho-Montana thrust belt. (Davidson et al. 1998, Anastasio et al. in press).