Synorogenic crustal fluid infiltration in the Idaho-Montana thrust belt

G. E. Bebout, D. J. Anastasio, J. E. Holl

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Mississippian carbonates in the Sevier thrust belt in Idaho-Montana show shifts in δ18OV-SMOW, from marine carbonate values to as low as +11‰, which are best explained by exchange with externally-derived, low-δ18O fluids. Late-stage, synkinematic calcite veins are depleted in 18O relative to the host-rocks and earlier-formed veins, many having δ18O of +5 to +10‰. These veins could have equilibrated with H2O with δ18O of -7.5 to +2.5‰, perhaps reflecting infiltration of the Sevier thrust wedge by nearshore meteoric waters to depths of ∼10 km. Calcite veins in the hangingwall and footwall of the Pioneer Metamorphic Core Complex, produced during later Paleogene extension, have δ18O of -8.7 to +1.4‰ consistent with equilibration with meteoric waters with δ18O as low as -14‰. Transition from a Cretaceous crustal fluid regime influenced by the nearby Western Interior Seaway to one influenced by lower-δ18O, more inland meteoric waters is consistent with seaway retreat during thrust wedge emergence and Paleogene uplift and subaerial volcanism.

Original languageEnglish
Pages (from-to)4295-4298
Number of pages4
JournalGeophysical Research Letters
Volume28
Issue number22
DOIs
Publication statusPublished - Nov 15 2001
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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