Project Title: Linking Cenozoic Uplift and Basin Development to the Formation of Mineral, Energy, and Water Resources in the Northern Great Basin
Mendenhall Fellow: Joseph Colgan, (650) 329-5461, email@example.com
Duty Station: Menlo Park, California
Start Date: January 9, 2006
Ph.D., Stanford University, 2005
Research Advisor: David John, (650) 329-5424, firstname.lastname@example.org; Keith Howard, (650) 329-4943, email@example.com; Alan Wallace (775) 784-5789, firstname.lastname@example.org; Tom Moore, (650) 329-5713, email@example.com
Project Description: The northern Basin and Range Province is the Nation's premier mining region, famous for the world-class gold deposits of the Carlin trend, but also hosting silver, base-metal, and diatomite deposits, along with significant petroleum, geothermal, and water resources. Despite decades of study, many fundamental questions remain concerning the origin of the Carlin trend and other precious-metal deposits, but uncertainty in the timing and kinematics of Cenozoic extension is currently a major roadblock to answering these questions (John and others, 2003). Not only did extensional faults and basins play a key role in the formation of mineral and other resources, but poorly-understood systems of normal faults have also significantly displaced many deposits from their original locations, obscuring the original geologic relationships that are critical for understanding the regional structure and environment in which the deposits formed (for example, Muntean and others, 2001).
The goal of this project is to develop a clearer understanding of extensional faulting the Elko-Carlin region, specifically, where are the major extensional faults, how much displacement do they represent, and when were the faults active? This work is based on geologic field studies of exposed faults and Tertiary rocks involved in faulting, 40Ar/39Ar dating of key Tertiary unconformities, and integrated apatite fission-track and (U-Th)/He studies of tilted fault blocks to constrain the timing and rate of faulting as well as the pre-extensional thermal history of the crust. These data will be synthesized with existing geophysical data to construct detailed, retro-deformable, crustal-scale geologic cross-sections along two primary E-W transects in north-central Nevada (fig. 1), with additional cross sections through more highly-deformed areas. By providing a more detailed understanding of the pre-extensional (early Cenozoic) structure of north-central Nevada and its modification by subsequent faulting and basin formation, these data will enable the USGS to evaluate more detailed models for the formation and evolution of the region’s mineral, geothermal, petroleum, and groundwater resources.
Figure 1. Geologic map of north-central Nevada, emphaisizing Cenozoic geology and structures (older rocks shown in gray). Major mineral deposits highlighted by green squares, and areas of focus for this study shown as heavy gray boxes. Geology simplified from Stewart and Carlson (1978); Northern Nevada rift from John and others (2000); mineral deposits from John and others (2003).
Figure 2. View north across Rocky Pass in the northern Toiyabe Range. The 33.8 Ma Caetano tuff in the foreground (being sampled by Dave John) crops out in the southern part of the study area and provides an important datum for restoring slip on the major normal faults.
John, D.A., Hofstra, A.H., and Theodore, T.G., 2003, Preface to special issues devoted to gold deposits in northern Nevada: Part 1, regional studies and epithermal deposits: Economic Geology, v. 98, p. 225-234.
John, D.A., Wallace, A.R., Ponce, D.A., Fleck, R.B., and Conrad, J.E., 2000, New perspectives on the geology and origin of the Northern Nevada rift, in Cluer, J.K., et al., eds., Geology and ore deposits 2000: The Great Basin and beyond: The Geological Society of Nevada, Reno, Nevada, p. 127–154.
Muntean, J., Tarnocai, C., Coward, M., Rouby, D., and Jackson, A., 2001, Styles and restorations of Tertiary extension in north-central Nevada, in Shaddrick, et al., eds., Regional tectonics and structural controls of ore: The major gold trends of northern Nevada, Geological Society of Nevada, Special Publication no. 33, p. 55–69.
Stewart, J. H., and Carlson, J. E., 1978, Geologic map of Nevada: U. S. Geological Survey, scale 1:500,000.
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