Linking hematite (U-Th)/He dating with the microtextural record of seismicity in the Wasatch fault damage zone, Utah, USA

Alexis K. Ault, Peter W. Reiners, James P. Evans, Stuart N. Thomson

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Techniques directly dating fault slip are few, limiting the ability to interpret the rock record of seismicity. Hematite is commonly found in fault zones, amenable to (U-Th)/He dating, and slip surface hematite may be reset by shear heating events and/or recrystallization. Glossy hematite-coated fault surfaces in the Wasatch fault footwall damage zone, Utah (USA), exhibit evidence of hematite cataclasis and preserve Pliocene hematite (U-Th)/He dates. Apatite (UTh)/ He a d fission track data from the host gneiss indicate footwall unroofing through ~ 2 km by ca. 4.5 Ma. Internally reproducible but disparate hematite (U-Th)/He dates 4.5 Ma and younger from isolated locations on a single fault surface do not reflect ambient cooling. We hypothesize that these dates, and associated iridescence and annealed crystal texture, document rapid cooling from friction-generated heat during small seismic slip events between ca. 4.5 and 2.5 Ma. Thus, hematite(U-Th)/He dating offers the potential to decipher thermal anomalies in the rock record associated with slip on 105-106 yr time scales.

Original languageEnglish (US)
Pages (from-to)771-774
Number of pages4
JournalGeology
Volume43
Issue number9
DOIs
StatePublished - 2015

ASJC Scopus subject areas

  • Geology

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