| Title | Basin and Rift Structure of the Central Black Rock Desert, Utah, and Initial Thermal Implications, from 3D Magnetotellurics |
|---|---|
| Authors | Wannamaker, Philip E.; Maris, Virginie; Hardwick, Christian L. |
| Year | 2013 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Sedimentary basins; Great Basin; rift structure; magnetotellurics |
| Abstract | A magnetotelluric (MT) survey of 93 soundings was acquired spanning an area of ~1500 km2 over the central Black Rock Desert of western Utah to assess sedimentary thicknesses, rift structure and thermal regime. A 3D image of electrical resistivity from depths of ~100 m to nearly 20 km in the deep crust was derived from the soundings using a finite-differenced based, Gauss- Newton regularized inversion algorithm. Electrically conductive late Tertiary sediments appear to approach 3 km thickness in a N-S band along the middle of the survey area corresponding closely to a pronounced trend of low gravity. Beneath the late Tertiary section, a near-vertical stem of low resistivity extends into the dominantly Paleozoic carbonate basement to depths exceeding 6 km. Toward greater depths, this step bifurcates into west- and east-dipping conductive zones with intervening high resistivity until they connect with a pervasive, quasi-horizontal low resistivity zone in the lower crust believed to represent regional, episodic magmatic underplating and fluid release. An area of enhanced heat flow associated with the Pavant Butte basaltic center corresponds to a modest amplification of the low resistivity stem and may also lie at the intersection with a secondary conductive trend entering from the east at depths of 3 km and above. The dipping, deeper bifurcated conductor may represent fluidized, high-strain zones predicted in continuum rifting deformation models and provide pathways for the N-S trend of Quaternary basaltic eruptions along the central Black Rock Desert. |