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UNCORRECTED Syntectonic infiltration by meteoric waters along the Sevier
 

Summary: UNCORRECTED
PROOF
Syntectonic infiltration by meteoric waters along the Sevier
thrust front, southwest Montana
A. C. RYGEL*, D. J. ANASTASIO AND G. E. BEBOUT
Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, PA, USA
ABSTRACT
Structural, petrographic, and isotopic data for calcite veins and carbonate host-rocks from the Sevier thrust front
of SW Montana record syntectonic infiltration by H2O-rich fluids with meteoric oxygen isotope compositions.
Multiple generations of calcite veins record protracted fluid flow associated with regional Cretaceous contraction
and subsequent Eocene extension. Vein mineralization occurred during single and multiple mineralization events,
at times under elevated fluid pressures. Low salinity (Tm )0.6C to +3.6C, as NaCl equivalent salinities) and
low temperature (estimated 5080C for Cretaceous veins, 6080C for Eocene veins) fluids interacted with wall-
rock carbonates at shallow depths (34 km in the Cretaceous, 23 km in the Eocene) during deformation. Shear
and extensional veins of all ages show significant intra- and inter-vein variation in d18
O and d13
C. Carbonate
host-rocks have a mean d18
OV-SMOW value of +22.2 3& (1r), and both the Cretaceous veins and Eocene veins
have d18

  

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

 

Collections: Geosciences