Curie Point Depth Estimates from Aeromagnetic Data from Death Valley and Surrounding Regions, California
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Pure and Applied Geophysics
Curie Point Depth Estimates from Aeromagnetic Data from Death Valley and Surrounding Regions, California MUSA HUSSEIN,1,3 KEVIN MICKUS,2 and LAURA F. SERPA1 Abstract—Aeromagnetic data were analyzed to determine the Curie point depth (CPD) by power density spectral and threedimensional inversion methods within and surrounding Death Valley in southern California. We calculated the CPD for 0.5° regions using 2D power density spectral methods and found that the CPDs varied between 8 and 17 km. However, the 0.5° region may average areas that include shallow and deep CPDs, and because of this limitation, we used the 3D inversion method to determine if this method may provide better resolution of the CPDs. The final 3D model indicates that the depth to the bottom of the magnetic susceptible bodies varies between 5 and 23 km. Even though both methods produced roughly similar results, the 3D inversion method produced a higher lateral resolution of the CPDs. The shallowest CPDs occur within the central and southern Death Valley, Panamint Valley, Coso geothermal field and the Tecopa hot springs region. Deeper ([15 km) CPDs occur over outcropping granitic and Precambrian lithologies in the Panamint Range, Grapevine Mountains, Black Mountains and the Argus Range. The shallowest CPD occurs within the central Death Valley over a possible seismically imaged magma body and slightly deeper values occur within the Panamint Valley, southern Death Valley and Tecopa Hot Springs. The shallow CPD values suggest that partially molten material may also be found in these latter regions. The CPD computed heat flow values for the region suggest that the entire area has high heat flow values ([100 mW m-2), on the other hand, locally extremely high values ([200 mW m-2) occur within the Panamint Valley, the southern and central Death Valley and Tecopa Hot Springs region. These locally high heat flow values may be related to midcrustal magma bodies; but additional geophysical experiments are needed to determine if the magma bodies exist. Key words: Aeromagnetic anomalies, Curie point depth, heat flow, inversion, spectral methods, Death Valley.
1 Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968-0555, USA. 2 Department of Geography, Geology and Planning, Missouri State University, Springfield, MO 65897, USA. E-mail: [email protected] 3 Present Address: Currently at New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA.
1. Introduction The thermal structure of the Earth is an important parameter in determining the tectonic environment of a region (CHAPMAN and FURLONG 1992). However, in determining the thermal structure of the crust or lithosphere, it is common to use borehole measurements to directly determine the heat flow. The problem with these measurements is that they are more than 1 km deep and not uniformly spaced, and if the measurements are more than 100 km apart then heat flow values could be affected by near surface features (e.g., groundwater flo
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