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EXTRA-BASINAL FLUID INFILTRATION, MASS TRANSFER, AND VOLUME STRAIN DURING FOLDING: INSIGHTS FROM THE
 

Summary: EXTRA-BASINAL FLUID INFILTRATION, MASS TRANSFER, AND
VOLUME STRAIN DURING FOLDING: INSIGHTS FROM THE
IDAHO-MONTANA THRUST BELT
DAVID J. ANASTASIO*, GRAY E. BEBOUT*, and JAMES E. HOLL
*Department of Earth and Environmental Sciences, Lehigh University,
Bethlehem, Pennsylvania, 18015; dja2@lehigh.edu; geb0@lehigh.edu
ABSTRACT. Finite strain and geochemical variations along strain gradients were
used to study cleavage development in carbonates in the Lost River Range, Idaho.
Deformation accommodating layer-parallel shear was partitioned into thin deforma-
tion zones during folding of Willow Creek anticline. Cleavage intensity is strong to very
strong in deformation zones and weak in surrounding rocks. Strain magnitudes range
from es 0.32 (1.15:0.93:0.73; x, y, z, principal axes of strain) outside, to es 0.64
(1.29:0.80:0.52) inside, deformation zones. We found a positive linear correlation
between strain, cleavage development, and negative dilation. Volume loss, at a cubic
centimeter scale, ranges from 12 percent to 49 percent. Cleavage selvages are depleted
in Ca and 18
O and enriched in other elements relative to microlithons and less
deformed protolith carbonates. Mass-balance considerations indicate that cleavage
was formed by incongruent pressure solution leading to a passive concentration of less
soluble components during Ca loss and metasomatic additions of Si, Al, and K to

  

Source: Anastasio, David - Department of Earth and Environmental Sciences, Lehigh University

 

Collections: Geosciences