Isotope constraints on the involvement of fluids in the San Andreas Fault System, California

Conference · Wed Jul 01 04:00:00 EDT 1998

OSTI ID:842020

Pili, E ^[1]; Kennedy, B M; Conrad, S M; Gratier, J -P; Poitrasson, F

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1. LBNL Library

Fluids are suspected to play a major role in earthquake mechanics, especially in the case of the weak San Andreas Fault (SAF). Models developed to explain the weakness of the fault are similar but rely on different fluid sources. A recent study of groundwaters associated with the SAF has provided evidence for a geopressured mantle fluid source (Kennedy et al., 1997). We present here an isotope study comparing deformation zones (gouges, breccias, fault veins, slickensides, cataclasites), and vein fillings with their hosts and the fluids associated with these materials, as sampled by fluid inclusions. We are investigating ca. 250 samples from over 20 localities along the San Andreas and adjacent faults from South San Francisco to East Los Angeles. Samples from the exhumed San Gabriel Fault, a deeper equivalent of the SAF, are included as well as samples from the Santa Ynez Fault, another former strand of the SAF embedded in Miocene limestones. All the major lithologies (granites, gneisses, sandstones, limestones, marbles and serpentinites) have been sampled for isotope analyses of C, O, H, He, Ne, Ar, Sr, Nd, and Pb.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: USDOE Director, Office of Science (US)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 842020
• Report Number(s): LBNL--44964
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
DEFORMATION
EARTHQUAKES
GNEISSES
GRANITES
SANDSTONES
SERPENTINITES