The Jemez Tomography Experiment (JTEX)

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The Jemez Tomography Experiment (JTEX) is a cooperative and interdisciplinary research program involving scientist from six major Universities, the Los Alamos National Laboratory with support from the DOE, and the U.S. Geological Survey. The Jemez Mountains volcanic field (JMVF) is a major Late Cenozoic silicic volcanic system. Perhaps its best-known feature is the Valles Caldera and associated 1.1 to 1.6 Ma explosive volcanic products including the Bandelier Tuff. The fundamental questions that relate to the JMVF and other recent silicic volcanic systems and which are addressed in the project are: 1. What is the nature and extent of crustal involvement and accompanying modifications of the crust during the volcanic activity in the JMVF? Are crustal intrusions, pluton, or underplated regions present in the crust beneath the Valles Caldera and Jemez Mountains? 2. How has the JMVF evolved through the last 15 Ma, culminating in eruption of the Bandelier rhyolite ignimbrite and caldera collapse? Petrologic models of silicic magma generation suggest that large volumes of mafic intrusions (on the order of ten times the volume of erupted material) are present in the crust beneath major silicic volcanic centers. Can we image these intrusions geophysically and interpret their relationships to the observed volcanic geology? In order to address these and other questions related specifically to the JMVF and generally to continental magmatism, the principal investigators will conduct intensive geophysical studies of the JMVF, analyze the data collected and interpret the results in concert with petrologic and geochemical information. The new geophysical data will include: seismic refraction/reflection, teleseismic delay time and waveform, gravity, magnetic, and magnetotelluric (MT) data. The program is designed to provide a three-dimensional image of the magmatically modified c rust beneath the JMVF. Tomographic inversion of the explosion seismic and teleseismic data and combined interpretation with the potential field, MT and geologic data will produce the most high resolution 3-D study of crustal scale features that is currently available.