GEOPHYSICAL INVESTIGATIONS OF SHIP ROCK AND THUMB IGNEOUS CENTERS, NEW MEXICO

Imaging the subsurface structure of two important volcanic centers of the mid-Tertiary Navajo Volcanic Field, on the Colorado Plateau, serves several purposes. Besides having specific implications for the formation of these particular features, our project will aid in understanding similar structures across the Colorado Plateau. Various researchers [e.g., Rubin, 1991; Meriaux and Jaupart, 1998; Segall et al., 2001] imagine the emplacement of a dike as vertical movement through host rock, often along preexisting faults or cracks, driven by magma pressure, and modified by the change in stress regime with depth. Other models [e.g., Delaney and Pollard, 1981; Quareni et al., 2001] allow magma to flow in pipes in addition to, and possibly following, its emplacement in dikes. Our results will provide valuable data against which to test such competing models of magma emplacement, and – in a wider sense – aid in understanding diverse processes like hydraulic fracturing, tensile fracturing, and dike-generated seismicity [Baer, 1991].