Issue: The Walker Lane structural zone in the western Great Basin contains numerous Miocene gold-silver (Au-Ag) deposits, several of which are world-class or uncommonly high-grade. These magmatic-hydrothermal deposits formed during continuous subduction-related magmatism but represent markedly different styles of mineralization. Although close temporal relationships among magmatism and hydrothermal systems have been established, the specific magmatic-hydrothermal processes and structural regimes that controlled formation (and concealment) of these often juxtaposed deposits are not precisely known. In order to identify additional resources in the districts and to predict concealed deposits (the future supplies of most mineral resources), it is necessary to conduct detailed stratigraphic, structural and geochronologic investigations of these districts and apply modern concepts of magma generation, magmatic-hydrothermal transitions, volcanic stratigraphy, and regional tectonism.
Project objectives: We are conducting linked investigations to address the magmatic-hydrothermal evolution, post-mineralization structural histories, and sources of host rocks and hydrothermal mineral components of three significant, subduction-related, Au-Ag districts. Two of the districts we are investigating, Tonopah, and Goldfield, NV, are among the largest or highest grade representatives of the quartz-adularia ("low sulfidation") and quartz-alunite ("high-sulfidation") deposit types. A third area we are characterizing is the Bodie Hills volcanic field, CA-NV, which contains two significant quartz-adularia vein systems (Bodie and Aurora districts), and extensive areas of quartz-alunite alteration, one of which was mined for Au and Ag (Masonic district). Collectively, the districts provide age (~21-8 Ma) and size (hundreds of millions to thousands of oz. Au+Ag) diversity, in addition to varied styles of mineralization.
Project Relevance: The geologic and isotopic characterization will enable comparison of source and process models for Walker Lane precious metal districts to those of Miocene precious metal deposits in the northern Great Basin that have been linked to a mantle plume and continental rifting. The results of this investigation will provide new geologic and tectonic maps of important districts in the Walker Lane, reduce uncertainty in sources of elements in ore deposits, improve precious metal deposits models, and refine provincial and local scale targeting of resource exploration.
du Bray, E.A., John, D.A., Box, S.E., Vikre, P.G., Fleck, R.J., and Cousens, B.L., 2016, Petrographic and geochemical data for Cenozoic volcanic rocks of the Bodie Hills, California and Nevada (ver. 1.1, August 2016): U.S. Geological Survey Data Series 764, 10 p., http://dx.doi.org/10.3133/ds764.
du Bray, E.A., John, D.A., and Cousens, B.L., 2014, Petrologic, tectonic, and metallogenic evolution of the southern segment of the ancestral Cascades magmatic arc, California and Nevada: Geosphere, 10(1), p. 1-39, https://doi.org/10.1130/GES00944.1.
du Bray, E.A., John, D.A., Cousens, B.L., Hayden, L.A., and Vikre, P.G., 2016, Geochemistry, petrologic evolution, and ore deposits of the Miocene Bodie Hills Volcanic Field, California and Nevada: American Mineralogist, 101(3), p. 644-677, https://doi.org/10.2138/am-2016-5440.
Fleck, R.J., du Bray, E.A., John, D.A., Vikre, P.G., Cosca, M.A., Snee, L.W., and Box, S.E., 2015, Geochronology of Cenozoic rocks in the Bodie Hills, California and Nevada: U.S. Geological Survey Data Series 916, 26 p., https://dx.doi.org/10.3133/ds916.
John, D.A., du Bray, E.A., Box, S.E., Vikre, P.G., Rytuba, J.J., Fleck, R.J., and Moring, B.C., 2015, Geologic map of the Bodie Hills, California and Nevada: U.S. Geological Survey Scientific Investigations Map 3318, 64 p., 2 sheets, scale 1:50,000, https://dx.doi.org/10.3133/sim3318.
Shawe, D.R., Snee, L.W., Byers, F.M., Jr., and du Bray, E.A., 2014, Geochronology and correlation of Tertiary volcanic and intrusive rocks in part of the southern Toquima Range, Nye County, Nevada: U.S. Geological Survey Scientific Investigations Report 2013–5206, 105 p., 1 plate, http://dx.doi.org/10.3133/sir20135206.
Vikre, P.G., John, D.A., du Bray, E.A., and Fleck, R.J., 2015, Gold-silver mining districts, alteration zones, and paleolandforms in the Miocene Bodie Hills volcanic field, California and Nevada: U.S. Geological Survey Scientific Investigations Report 2015–5012, 160 p., http://dx.doi.org/10.3133/sir20155012.
Henry, C.D., and John, D.A., 2015, The relationship between Cenozoic rollback magmatism and mineral deposits in the Great Basin, USA: 2015 Geological Society of Nevada Symposium, May 14-23, Reno, NV.
Hofstra, A.H., and Manning, A.H., 2013, Helium isotope data from the Goldfield epithermal system, Nevada: Evidence for volatile input from a primitive mantle source during ore formation: Abstract V31C-02 presented at 2013 Fall Meeting, AGU, San Francisco, Calif., 9-13 Dec. View Hofstra 2013 AGU abstract.
John, D.A., du Bray, E.A., Box, S.E., Blakely, R.J., Fleck, R.J., Vikre, P.G., Cousens, B., and Moring, B.C., 2012, Late Cenozoic Magmatic and Tectonic Evolution of the Ancestral Cascade Arc in the Bodie Hills, California and Nevada: Insights from Integrated Geologic, Geophysical, Geochemical and Geochronologic Studies: Abstract V33B-2860 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec. View John 2012 AGU abstract.
John, D.A., du Bray, E.A., Henry, C.D., and Vikre, P.G., 2015, Cenozoic magmatism and epithermal gold-silver deposits of the southern ancestral Cascade Arc, western Nevada and eastern California, in Pennell, W.M., and Garside, L.J., eds., New Concepts and Discoveries, Geological Society of Nevada Symposium Proceedings, May 14-23, Reno, NV, p. 611-635.
Kingdon, S.A., Cousens, B.L., John, D.A., and du Bray, E.A., 2014, Pliocene to late Pleistocene magmatism in the Aurora Volcanic Field, Basin and Range province, Nevada and California, USA: GAC-MAC 2014, 21-23 May 2014, Fredericton, NB, p. 139-140. View GAC-MAC 2014 Abstract Volume. [PDF file, 9.2 MB]
Kingdon, S., Cousens, B., John, D.A., and du Bray, E.A., 2013, Pliocene to late Pleistocene magmatism in the Aurora Volcanic Field, Nevada and California, USA: Abstract V13G-2700 presented at 2013 Fall Meeting, AGU, San Francisco, Calif., 9-13 Dec. View Kingdon 2013 AGU abstract.
Manning, A., and Hofstra, A., 2014, Helium isotope data from the Goldfield epithermal deposit, Nevada: Evidence for volatile input from a primitive mantle source during ore formation: PACROFI XII, 2-6 June 2014, Fort Collins, CO.
Pietruszka, A.J., and Neymark, L.A., 2014, Advanced techniques for determining elemental composition, isotopic abundance, and radioisotopic age using bulk and microanalysis II: Abstract V34A-01 presented at 2014 Fall Meeting, AGU, San Francisco, Calif., 15-19 Dec. View Pietruszka 2014 AGU abstract.
Vikre, P.G., 2013, Close time-space relationships among diverse quartz-adularia Au+Ag veins, quartz-alunite Au+Ag±Cu deposits and alteration zones, and stratiform S° deposits in Miocene volcanic fields, CA-NV, U.S.A.: Society for Economic Geologists Whister 2013: Geoscience for Discovery, 24-27 September, Whistler, BC.
Vikre, P.G., Premo, W.R., and Cosca, M.A., 2014, Linkages between crustal stratigraphy, magmatic-hydrothermal evolution and sources of components of gold-silver deposits in the adjoining Goldfield and Tonopah Districts, Nevada: Geological Society of America Abstracts with Programs, Vol. 46, No. 6, p. 249. View Vikre 2014 GSA abstract.
Vikre, P.G., Premo, W.R., Hayden, L.A., Koenig, A.E., and Pribil, M.J., 2013, Sources of host rocks and hydrothermal mineral components in the Miocene Goldfield, Tonopah, and Comstock Lode Au-Ag-(Cu) districts, NV: Geological Society of America Abstracts with Programs, Vol. 45, No. 7, p. 536. View Vikre 2013 GSA abstract.
Geology, Minerals, Energy, and Geophysics Science Center