Paper No. 19
Presentation Time: 8:00 AM-12:00 PM
STRUCTURAL AND LITHOLOGIC CONSTRAINTS TO METALOGENESIS IN THE BODIE HILLS, NEVADA AND CALIFORNIA, INTERPRETED WITH GEOPHYSICAL AND GEOSTATISTICAL METHODS
Using a multifaceted geophysical and geostatistical approach to investigate the geology and metalogenesis is a novel approach towards understanding factors influencing regional- and local-scale metalogenesis. The Aurora and Bodie mining districts are located in the Miocene volcanics of the Bodie Hills, north of Mono Lake, on the opposite sides of the Nevada-California state line. From the standpoint of economic geology, both deposits are structurally controlled, low-sulfidation, quartz-adularia-sericite precious metal vein deposits with an extensive alteration halo. Using detailed field mapping and a combined array of geophysical data in conjunction with traditional field mapping and GIS-based Weights of Evidence (WofE) modeling was utilized to attain better understanding of the districts in the local and regional framework. The gravity data suggests a NE-trending, positive anomaly, resulting from a density contrast between the presumably uplifted pre-Tertiary basement and Miocene volcanic assemblage in the Bodie Hills. The aeromagnetic data are dominated by the strong signature of the Miocene volcanism (vents, flows, etc.) and suggests that the volcanic activity is concentrated along the northeasterly corridor of basement uplift. Multispectral, spaceborne imagery (Landsat ETM, ASTER) shows the regional structural setting, which is dominated by NNE and NE-trending lineaments and major alteration trends in the Bodie Hills. Individual segments of the regional-to-local geophysical survey are field checked and spatially integrated using WofE. The interpretation and WofE modeling of the geophysical data and detailed geologic field mapping reveal a close relationship between the basement uplift (source for metals), NE-trending structures (conduits), volcanic activity (energy), hydrothermal activity (genesis) and mineralization in Aurora and Bodie. This study confirms that the deposits in the Bodie Hills represent low-sulfidation systems hosted in a strike-slip influenced vein systems, which may be genetically associated with the initial phase of Miocene extension and stress accommodation in Western Great Basin during 15 8 Ma.