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In order to study magmatism and geothermal systems in The Geysers-Clear Lake region, we developed a detailed three-dimensional tomographic velocity model based on local earthquakes. This high-resolution model resolves the velocity structure of the crust in the region to depths of approximately 12 km. The most significant velocity contrasts in The Geysers-Clear Lake region occur in the steam production area, where high velocities are associated with a Quaternary granitic pluton, and in the Mount Hannah region, where low velocities occur in a 5-km-thick section of Mesozoic argillites. In addition, a more regional tomographic model was developed using traveltimes from earthquakes covering most of northern California....
It is important to know whether major mining districts in north-central Nevada are underlain by crust of the Archean Wyoming craton, known to contain major orogenic gold deposits or, alternatively, by accreted crust of the Paleoproterozoic Mojave province. Determining the location and orientation of the Archean-Proterozoic suture zone between these provinces is also important because it may influence subsequent patterns of sedimentation, deformation, magmatism, and hydrothermal activity. The suture zone is exposed in northeastern Utah and south-western Wyoming and exhibits a southwest strike. In the Great Basin, the suture zone strike is poorly constrained because it is largely concealed below a Neoproterozoic-Paleozoic...
Categories: Publication; Types: Citation; Tags: Geosphere
In the winter of 1811-12, three of the largest historic earthquakes in the United States occurred near New Madrid, Mo. Seismicity continues to the present day throughout a tightly clustered pattern of epicenters centered on the bootheel of Missouri, including parts of northeastern Arkansas, northwestern Tennessee, western Kentucky, and southern Illinois. In 1990, the New Madrid seismic zone/Central United States became the first seismically active region east of the Rocky Mountains to be designated a priority research area within the Natural Earthquake Hazards Reduction Program (NEHRP). This Professional Paper is a collection of papers, some published separately, presenting results of the newly intensified research...
Categories: Publication; Types: Citation; Tags: Professional Paper
We combined information from Sr and Pb isotope data and magnetotelluric models to develop a new magnetic and gravity interpretation of the crustal structure of north-central Nevada to better understand the origin of mineral trends. The new interpretation suggests a crustal structure that is composed of Precambrian continental crust, transitional crust, and primarily oceanic crust that are separated by northwest- and northeast-striking fault zones. The magnetic expression of the buried Precambrian continental crust is recognized for the first time. Low magnetic values primarily reflect magnetite-poor crystalline crust rather than elevated temperatures at depth. Northwest- and northeast-striking crustal boundaries...
Categories: Publication; Types: Citation; Tags: Economic Geology
The Albuquerque-Santa Fe region is rapidly growing. The Santa Fe Group aquifer in the Middle Rio Grande Basin (MRGB) is the main source of municipal water for the greater Albuquerque metropolitan area and is more limited than previously thought (Thorn et al., 1993). The MRGB, as defined hydrologically and used here, is the area within the Rio Grande Valley extending from Cochiti Dam downstream to the community of San Acacia (Figure 1). Because approximately 600,000 people (40 percent of the population of New Mexico) live in the study area (Bartolino, 1999), water shortfalls could have serious consequences for the state. Future growth and land management in the region depends on accurate assessment and protection...
Categories: Publication; Types: Citation; Tags: Open-File Report
Combined evidence from gravity, radiogenic isotope, and magnetotelluric (MT) data indicates a crustal fault zone that coincides with the northwest-trending Battle Mountain-Eureka (BME) mineral trend in north-central Nevada, USA. The BME crustal fault zone likely originated during Neoproterozoic-Early Paleozoic rifting of the continent and had a large influence on subsequent tectonic events, such as emplacement of allochthons and episodic deformation, magmatism, and mineralization throughout the Phanerozoic. MT models show the fault zone is about 10 km wide, 130-km long, and extends from 1 to 5 km below the surface to deep crustal levels. Isotope data and gravity models imply the fault zone separates crust of fundamentally...

    map background search result map search result map Tectonic controls on magmatism and geothermal resources in the Geysers-Clear Lake region, California; integration of new geologic, earthquake tomography, seismicity, gravity, and magnetotelluric data Tectonic controls on magmatism and geothermal resources in the Geysers-Clear Lake region, California; integration of new geologic, earthquake tomography, seismicity, gravity, and magnetotelluric data