Compositional and Hydrothermal Frictional Strength Data for Five Chlorite Gouges

A series of hydrothermal frictional strength experiments was conducted on synthetic gouges prepared from five chlorite-rich samples of varying composition. We present chlorite mineral compositions obtained by electron microprobe techniques, and X-ray diffraction and bulk chemical analyses of the gouges that were prepared by hand-grinding each sample to less than 90-µm grain diameter. Major and minor element gouge analyses were conducted in the Geology, Geophysics, and Geochemistry Science Center laboratory of the U. S. Geological Survey in Lakewood, CO. All of the other data were collected in the earthquake Science Center laboratories, which were located at that time in Menlo Park, CA. Chlorite samples tested: Fe-chlorite. Chlorite-garnet schist of unknown origin. The millimeter-scale euhedral garnets were removed from the sample prior to grinding. Ore14-1. Chlorite blackwall, the inner zone of a metasomatic alteration rind surrounding a high-grade mafic blueschist block in Coos Counry, southwest Oregon. Location: 42.9883°N, 124.3811°W. LP14-3a. Large, chlorite-rich clast exposed in an exhumed shear on the west side of Lake Pillsbury, Mendocino County, California. Location: 39.4072°N, 122.9575°W. CCa-2. Ripidolite chlorite, obtained from the Clay Minerals Society Special Clay Minerals Collection. Flagstaff Hill, El Dorado County, California. Location: 38.7648°N, 121.0839°W. Russian chlorite. Clinochlore cleavage flakes from Achmativ Mine, a famous skarn deposit located near Zlatonst in the Southern Urals, Russia. Location: 55.3042°N, 59.6561°E.