HR: 0800h
AN: T21A-0452    [Abstracts]
TI: Elemental and Stable Isotope Chemistry of Cuttings and Core Samples From SAFOD Drill Hole
AU: * Kirschner, D L
EM: dkirschn@eas.slu.edu
AF: Saint Louis University, Earth and Atmospheric Sciences 3507 Laclede Ave., Saint Louis, MO 63103 United States
AU: Evans, J
EM: jpevans@cc.usu.edu
AF: Utah State University, Dept. of Geology 4505 Old Main Hill, Logan, UT 84322 United States
AU: Chester, J
EM: chesterj@geo.tamu.edu
AF: Texas A and M University, Dept of Geology and Geophysics M.T. Halbouty Building, College Station, TX 77843 United States
AU: Chester, F
EM: chesterf@geo.tamu.edu
AF: Texas A and M University, Dept of Geology and Geophysics M.T. Halbouty Building, College Station, TX 77843 United States
AU: Solum, J
EM: jsolum@usgs.gov
AF: United States Geological Survey, Earthquake Hazards Team, Menlo Park, CA 94025 United States
AU: Moore, D
EM: dmoore@usgs.gov
AF: United States Geological Survey, Earthquake Hazards Team, Menlo Park, CA 94025 United States
AB: We have analyzed the major and minor element chemistry and stable isotope composition of samples from the SAFOD drill hole in order to document fluid-rock interactions in the San Andreas and associated fault zones. To date, we have analyzed samples from three sections of the drill hole that contain faults, mineralogical changes, drilling breaks, and/or anomalous gas shows. The elemental chemistry of samples from 10450 to 10530 ft interval (measured depth, MD) does not vary significantly. Only magnesium, yttrium, and barium increase and calcium decreases moderately down hole across this interval. The yttrium and barium variability is potentially due to variable contamination of barite-bearing mud in the cuttings. In samples from 10860 to 11000 ft (MD), iron, magnesium, and potassium increase and calcium decreases moderately down hole. In sample interval 11400 to 11540 ft (MD), iron increases and calcium decreases slightly down hole. The other major and minor elements in the XRF analyses do not vary much across these three intervals. These variations in elemental chemistry correspond to mineralogy changes across these intervals. Carbon and oxygen isotope values of carbonate veins and breccias from the 10450 and 11400 ft intervals range from 0 to +8 per mil (carbon) and 14 to 20 per mil (oxygen), consistent with carbonate precipitation from fluids that had isotopically exchanged with silicates. More work is being done to elucidate the origin of the fluid and the extent of fluid-rock interactions in the fault zones.
DE: 8045 Role of fluids
DE: 8111 Continental tectonics: strike-slip and transform
SC: Tectonophysics [T]
MN: Fall Meeting 2005