Preservation of an extreme transient geotherm in the Raft River detachment shear zone

R. Gottardi, C. Teyssier, A. Mulch, T. W. Vennemann, M. L. Wells

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Extensional detachment systems separate hot footwalls from cool hanging walls, but the degree to which this thermal gradient is the product of ductile or brittle deformation or a preserved original transient geotherm is unclear. Oxygen isotope thermometry using recrystallized quartz-muscovite pairs indicates a smooth thermal gradient (140 °C/100 m) across the gently dipping, quartzite-dominated detachment zone that bounds the Raft River core complex in northwest Utah (United States). Hydrogen isotope values of muscovite (δDMs ~ -100‰) and fluid inclusions in quartz (δDFluid ~ -85‰) indicate the presence of meteoric fluids during detachment dynamics. Recrystallized grain-shape fabrics and quartz c-axis fabric patterns reveal a large component of coaxial strain (pure shear), consistent with thinning of the detachment section. Therefore, the high thermal gradient preserved in the Raft River detachment reflects the transient geotherm that developed owing to shearing, thinning, and the potentially prominent role of convective flow of surface fluids.

Original languageEnglish (US)
Pages (from-to)759-762
Number of pages4
JournalGeology
Volume39
Issue number8
DOIs
StatePublished - Aug 2011

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