SEG 45 Final_qx4 - Society of Economic Geologists

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14 SEG NEWSLETTER No 63 • OCTOBER 2005 ... from 13 Exploring for Deposits Under Deep Cover Using Geochemistry (Continued) WEST Cu Soil Anomalies EAST Water Table Gravel Andesite Basement Saline Water minerals, or held within secondary minerals, such as carbonates or iron and manganese oxides. The objective is to maximize the anomaly/background contrast. For both Spence and other sites in Chile, and for Mike the response of five selective leaches: deionized water, Enzyme Leach, MMI, ammonium acetate, and hydroxylamine, plus one non-selective leach, aqua regia, were compared (Cameron et al., 2004). At the Chile sites selective leaches give better anomaly/background contrast than aqua regia. This is consistent with Fracture Zone Cu Deposit Porphyry Meteoric Water FIGURE 7. Conceptual model for groundwater flow and generation of soil anomalies over the Spence deposit. Saline formation waters from depth migrate up a fracture zone coincident with the deposit. In the deposit and gravel aquifer they mix with meteoric waters derived from precipitation in the Andes to the east. During earthquakes, saline waters are pumped to the surface entraining Cu from the deposit. Salts derived from the evaporation of water reaching the surface are largely preserved in the hyper-arid climate of the Atacama desert. the model that anomalous elements, such as Cu, have been transferred to the surface dissolved in water, and soil forming processes have yet to incorporate these in more resistant minerals that are dissolved by aqua regia. At Mike, the contrast shown by selective leaches and aqua regia are similar. Given the locus of the anomalies at Mike—on the interpreted scarp slope of the Nebulous fault zone—the soil anomalies may have been derived from mineralized fault rock, not directly from water. ACKNOWLEDGEMENTS At Mike, Robert Jackson of Newmont Inc. provided a great deal of help and advice. Our sampling there was carried out with Mary Doherty and Kevin Creel. John Norby kindly provided much additional information on the geology of Mike. At Spence, Ollie Bonham and Jack Currie of RioChilex provided many courtesies. EMC and MIL were assisted in the field in Chile with enthusiasm and humour by Daniel Salinas and Alexi Ramirez. George Steele of Rio Tinto generously gave logistical support for the Chile work. We thank CAMIRO and 26 company sponsors for their support and encouragement throughout the project. REFERENCES Aravena, R., Suzuki, O, Pena, H., Pollastri, A., Fuenzalida, H. and Grilli, A., 1999, Isotopic composition and origin of the precipitation in northern Chile: Applied Geochemistry, v. 14, p. 411–422. Bawden, T.M., Einaudi, M.T., Bostick, B.C., Meiborn, A., Wooden, J., Norby, J.W., Orobono, M.J.T. and Chamberlain, C.P., 2003, Extreme 34 S depletions in ZnS at the Mike gold deposit, Carlin trend, Nevada: Evidence for bacteriogenic supergene sphalerite: Geology, v. 31, p. 913–916. Briggs, R.C. and Troxell, H.C., 1955, Effect of Arvin-Tehachapi earthquake on spring and stream flow, in Oakeshott, G.B., ed., Earthquakes in Kern County, California, during 1952. Part 1: California Department of Natural Resources, Division of Mines Bulletin, v. 171, p. 81–98. Cameron, E.M. and Doherty, M.E., 2001, Geochemical data from a soil traverse across the Mike gold-copper deposit, Carlin, Nevada: Canadian Mining Industry Research Organization (CAMIRO) Report, 17 p. JOSEPH R. ANZMAN Exploration Geophysicist • consulting • interpretation • project management • geophysical surveys • domestic & foreign P.O. Box 370526 303-337-4559 Denver, Colorado 80237 telephone/fax PAID ADVERTISEMENT PAID ADVERTISEMENT
OCTOBER 2005 • No 63 SEG NEWSLETTER 15 Cameron, E.M. and Leybourne, M.I., 2005, Relationship between groundwater geochemistry and soil geochemical anomalies at the Spence copper porphyry deposit, Chile: Geochemistry: Exploration, Environment, Analysis, v. 5, p. 135–145. Cameron, E.M., Leybourne, M.I. and Kelley, D.L., 2002, Exploring for deeply covered mineral deposits: Formation of geochemical anomalies in northern Chile by earthquake-induced surface flooding of mineralized groundwaters: Geology, v. 30, p. 1007–1010. Cameron E.M., Hamilton S.M., Leybourne M.I., Hall G.E.M. and McClenaghan B.E., 2004, Finding deeply buried deposits using geochemistry: Geochemistry: Exploration, Environment, Analysis, v. 4, p. 1–26. Dohrenwend, J.C. and Moring, B.C. 1991, Reconnaissance photogeological map of young faults in the Winnemucca 1° by 2° quadrangle, Nevada: U.S. Geological Survey, Miscellaneous Field Studies Map MF-2175. Dublyansky, Y.V., Smirnov, S.Z. and Pashenko, S.E., 2003, Identification of the deep-seated component in paleo fluids circulating through a potential nuclear waste disposal site: Yucca Mountain, Nevada, USA: Journal of Geochemical Exploration, v. 78, p. 39–43. Hamilton, S.M., 1998, Electrochemical mass transport in overburden: a new model to account for the formation of selective leach geochemical anomalies in glacial terrain: Journal of Geochemical Exploration, v. 63, p. 155–172. Hoefs, J., 2004, Stable Isotope Geochemistry: Berlin, Springer, 244 p. Muir-Wood, R. 1994, Earthquakes, straincycling and the mobilization of fluids, in Parnell, J., ed., Geofluids: Origin, migration and evolution of fluids in sedimentary Basins: Geological Society Special Publication, v. 78, p. 85–98. Norby, J.W. and Orobona, M.J.T., 2002, Geology and mineral systems of the Mike deposit, in Thompson, T.B., Teal, L., and Meeuwig, R.O, eds., Gold deposits of the Carlin Trend: Nevada Bureau of Mines and Geology, Bulletin 111, p. 143–167. Piatak, N.M., Seal, R.R., and Hammarstrom, J.M., 2004, Environmental significance of cadmium and other trace-element concentrations in sphalerite from mineral deposits: Geological Society of America Abstracts with Programs, v. 36, no. 5, p. 27. Sibson, R.H., 1981, Fluid flow accompanying faulting: Field evidence and models, in Simpson, D.W. and Richards, P.G., eds., Earthquake predication: An international review: American Geophysical Union, Maurice Ewing Series, v. 4, p. 593–603. Smee, B., 2003, Theory behind the use of soil pH measurements as an inexpensive guide to buried mineralization, with examples: Explore, no. 118, p. 1, 14–18. Taylor, H.P., 1974, The application of oxygen and hydrogen isotope studies to problems of hydrothermal alteration and ore deposition: Economic Geology, v. 69, p. 843–883. Teal, L. and Branham, A., 1997, Geology of the Mike gold-copper deposit, Eureka County, Nevada: Society of Economic Geologists Guidebook Series, v. 28, p. 257–276. Tchalenko, J.S., 1973, The Kashmar (Turshiz) 1903 and Torbat-e Heidariyeh (South) 1923 earthquakes in Central Khorassan (Iran): Annali di Geofisica, v. 26, p. 29–40. Woodall, R., 2005, The challenge of discovering mineral deposits under cover: What can we learn from the past?: Society of Economic Geologists Newsletter, no. 60, p. 35–36. 1 Geophysical Consulting, Survey Design, Data Interpretation Subsurface Structural Mapping Ground Water Delineation Minerals Exploration Rentals GEOPHYSICAL SERVICES Equipment Sales Physical Properties Lab Electromagnetic (EM) Techniques, Induced Polarization (IP) Techniques, Gravity, Magnetics, Shallow Seismic, & Downhole Techniques ZONGE ENGINEERING & RESEARCH ORGANIZATION 1-800-523-9913 or 520-327-5501 Fax 520-325-1588, seg@zonge.com, www.zonge.com Offices World Wide USA: -Tucson, Arizona -Sparks, Nevada -Anchorage & Fairbanks, Alaska Other: -Australia -Chile -Brazil -Indonesia PAID ADVERTISEMENT PAID ADVERTISEMENT
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