Magnesium-rich Phyllosilicates in Creeping Faults: A Study of the Maacama Fault Zone, Mendocino County, California

The Maacama Fault Zone in Mendocino County, California consists of multiple fault gouges with varying mineralogy, making this an ideal location to study the potential relationship between the magnesium phyllosilicate content of a fault gouge and fault creep. This study uses the presence of magnesium-rich phyllosilicates to test the hypothesis that faults to the northeast of Little Lake Valley in Mendocino County are accommodating strain on the Maacama Fault Zone through creep. Analytical work expands the work of Schroeder (2010) to more completely address the relationship between fault creep and mineralogy by sampling three fault gouges in the Maacama Fault Zone. The mineralogical content and textures of these gouges were characterized using petrographic analysis, x-ray diffraction, and scanning electron/energy dispersive spectrometry. Corrensite, a chlorite-smectite interlayer clay that has been found in creeping faults, was found within one of the fault gouges, along with chlorite, suggesting aseismic activity may be present on these faults.