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Title: Geologic and geophysical investigations of the Zuni-Bandera volcanic field, New Mexico

Geologic and geophysical investigations of the Zuni-Bandera volcanic field, New Mexico A positive, northeast-trending gravity anomaly, 90 km long and 30 km wide, extends southwest from the Zuni uplift, New Mexico. The Zuni-Bandera volcanic field, an alignment of 74 basaltic vents, is parallel to the eastern edge of the anomaly. Lavas display a bimodal distribution of tholeiitic and alkalic compositions, and were erupted over a period from 4 Myr to present. A residual gravity profile taken perpendicular to the major axis of the anomaly was analyzed using linear programming and ideal body theory to obtain bounds on the density contrast, depth, and minimum thickness of the gravity body. Two-dimensionality was assumed. The limiting case where the anomalous body reaches the surface gives 0.1 g/cm/sup 3/ as the greatest lower bound on the maximum density contrast. If 0.4 g/cm/sup 3/ is taken as the geologically reasonable upper limit on the maximum density contrast, the least upper bound on the depth of burial is 3.5 km and minimum thickness is 2 km. A shallow mafic intrusion, emplaced sometime before Laramide deformation, is proposed to account for the positive gravity anomaly. Analysis of a magnetotelluric survey suggests that the intrusion is not due to recent basaltic magma associated with the Zuni-Bandera volcanic field. This more » large basement structure has controlled the development of the volcanic field; vent orientations have changed somewhat through time, but the trend of the volcanic chain followed the edge of the basement structure. It has also exhibited some control on deformation of the sedimentary section. « less
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Publication Date:
OSTI Identifier:OSTI ID: 6516124
Report Number(s):LA-8827-MS
ON: DE81023984
DOE Contract Number:W-7405-ENG-36
Resource Type:Technical Report
Research Org:Los Alamos National Lab., NM (USA); Sandia National Labs., Albuquerque, NM (USA); New Mexico Univ., Albuquerque (USA). Dept. of Geology
Country of Publication:United States
Language:English
Subject: 15 GEOTHERMAL ENERGY; NEW MEXICO; GRAVITY SURVEYS; MAGNETOTELLURIC SURVEYS; RESISTIVITY SURVEYS; BASALT; BASEMENT ROCK; DATA ANALYSIS; EXPERIMENTAL DATA; GEOLOGIC FAULTS; GEOPHYSICAL SURVEYS; GEOTHERMAL EXPLORATION; LAVA; MAGMA; VOLCANIC REGIONS; DATA; ELECTRICAL SURVEYS; ELECTROMAGNETIC SURVEYS; EXPLORATION; GEOLOGIC STRUCTURES; IGNEOUS ROCKS; INFORMATION; NORTH AMERICA; NUMERICAL DATA; ROCKS; SOUTHWEST REGION; SURVEYS; USA; VOLCANIC ROCKS Geothermal Legacy 150301* -- Geothermal Exploration & Exploration Technology-- Geophysical Techniques & Surveys; 150201 -- Geology & Hydrology of Geothermal Systems-- USA-- (-1989)