Lithodiversity and Its Spatial Association with Metallic Mineral Sites, Great Basin of Nevada
Tóm tắt
Geographical information system (GIS) techniques were used to investigate the spatial association between metallic mineral sites and lithodiversity in Nevada. Mineral site data sets include various size and type subsets of about 5,500 metal-bearing occurrences and deposits. Lithodiversity was calculated by counting the number of unique geological map units within four sizes of square-shaped sample neighborhoods (2.5-by-2.5, 5-by-5, 10-by-10, and 20-by-20 km) on three different scales of geological maps (national, 1:2,500,000; state, 1:500,000; county, 1:250,000). The spatial association between mineral sites and lithodiversity was observed to increase with increasing lithodiversity. This relationship is consistent for (1) both basin-range and range-only regions, (2) four sizes of sample neighborhoods, (3) various mineral site subsets, (4) the three scales of geological maps, and (5) areas not covered by large-scale maps. A map scale of 1:500,000 and lithodiversity sampling neighborhood of 5-by-5 km was determined to best describe the association. Positive associations occurred for areas having >3 geological map units per neighborhood, with the strongest observed at approximately >7 units. Areas in Nevada with more than three geological map units per 5-by-5 km neighborhood contain more mineral sites than would be expected resulting from chance. High lithodiversity likely reflects the occurrence of complex structural, stratigraphic, and intrusive relationships that are thought to control, focus, localize, or expose mineralization. The application of lithodiversity measurements to areas that are not well explored may help delineate regional-scale exploration targets and provide GIS-supported mineral resource assessment and exploration activity another method that makes use of widely available geological map data.
Tài liệu tham khảo
Agterberg, F. P., Bonham-Carter, G. F., and Wright, D. F., 1990, Statistical pattern integration for mineral exploration, in Gaál, G., and Merriam, D. F., eds., Computer Applications in Resource Estimation Prediction and Assessment of Metals and Petroleum: Pergamon Press, Oxford, p. 1–12.
Bonham-Carter, G. F., 1994, Geographic Information Systems for geoscientists: modelling with GIS: Pergamon Press/Elsevier Science Publications, Tarrytown, New York, 398 p.
Bonham-Carter, G. F., and Agterberg, F. P., 1999, Arc-WofE: a GIS tool for statistical integration of mineral exploration datasets: Proc. 52nd Session of Intern. Statistical Inst. (Helsinki, Finland) unpaginated, [http://www.stat.fi/isi99/proceedings. html].
Bonham-Carter, G. F., Agterberg, F. P., and Wright, D. F., 1989, Weights of evidence modelling: a new approach to mapping mineral potential, in Agterberg, F. P., and Bonham-Carter, G. F., eds., Statistical Applications in the Earth Science: Geol. Survey Canada, Paper 89–9, p. 171–183.
Cox, D. P., Barton, P. B., and Singer, D. E., 1986, Introduction, in Cox, D. P., and Singer, D. A., eds., Mineral Deposit Models: U. S. Geol. Survey Bull. 1693, p. 1–6.
Geologic Data Systems, 1998, The Nevada County geological map series: 1600 Emerson Street, Denver, CO, 80218.
Goodchild, M. F., 1995, Error estimates: Workshop for Geomatics 95, Ottawa, Congress Centre, Geomatics Workshop, 42 p.
Granger, A. E., Bell, M.M., Simmons, G. C., and Lee, F., 1957, Geology and mineral resources of Elko County, Nevada: Nevada Bur. Mines and Geology Bull. 54, 190 p.
Griffiths, J. C., 1978, Mineral resource assessment using the unit regional value concept: Math. Geology, v. 10, no. 5, p. 441–472.
Griffiths, J. C., and Smith, C. M., 1992, Mineral resources versus geologic diversity in small areas: Computers & Geosciences, v. 18, no. 5, p. 477–486.
Griffiths, J. C., Pilant, A. D., and Smith, C. M., 1997, Quantitative estimates of the geology of large regions and their application to mineral-resource assessment: Nonrenewable Resources, v. 6, no. 3, p. 157–236.
Griffiths, J. C., Watson, A. T., and Menzie, W. D., 1980, Relationship between mineral resources and geologic diversity, in Miall, A. D., ed., Facts and Principles of World Petroleum Occurrence: Can. Soc. Petroleum Geology Mem. 6, p. 329–341.
Hose, R. K., Blake, M. C., Jr., and Smith, R. M., 1976, Geology and mineral resources of White Pine County, Nevada: Nevada Bur. Mines and Geology Bull. 85, 105 p.
Johnson, M. G., 1977, Geology and mineral deposits of Pershing County, Nevada: Nevada Bur. Mines and Geology Bull. 89, 115 p.
King, P. B., and Beikman, H. M., 1974a, Explanatory text to accompany the geologic map of the United States: U.S. Geol. Survey Prof. Paper 901, 40 p.
King, P.B., and Beikman, H. M., 1974b, Geologic map of the United States: U.S. Geol. Survey, scale 1:2,500,000, 3 sheets.
Klimowicz, J., Johnson, G. L., and Hess, R. H., 1997, Interactive index of geological mapping in Nevada: Nevada Bur. Mines and Geology Open-File Rept. 97–2, CD-ROM.
Long, K. R., De Young, J. H., Jr., and Ludington, S. D., 1998, Database of significant deposits of gold, silver, copper, lead, and zinc in the United States; Part A, Database description and analysis; Part B, Digital database:U.S. Geol. Survey Open-File Rept. 98–206, 35 p., one 3.5 inch diskette.
McFaul, E. J., Mason, Jr., G. T., Ferguson, W. B., and Lipin, B. R., 2000,U. S. Geological Survey Mineral Databases—MRDS and MAS/MILS: U.S. Geol. Survey Digital Data Series DDS-52, 2 CD-ROMs.
Mihalasky, M. J., 1999, Mineral potential modelling of gold and silver mineralization in the Nevada Great Basin—a GIS-based analysis using weights of evidence: unpubl. doctoral dissertation, Univ. Ottawa, 360 p.
Mihalasky, M. J., and Bonham-Carter, G. F., 1999, The spatial relationship between mineral deposits and lithologic diversity in the Nevada Great Basin, in Lippard, S. J., Naess, A., and Sinding-Larsen, R., eds., Proc. IAMG '99 (Trondheim, Norway), p. 369–374.
Raines, G. L., Sawatzky, D. L., and Connors, K. A., 1996, Great Basin geoscience data base: U.S. Geol. Survey Digital Data Series DDS–41, two CD-ROMs.
Roberts, R. J., Montgomery, K. M., and Lehner, R. E., 1967, Geology and mineral resources of Eureka County, Nevada: Nevada Bur. Mines and Geology Bull. 64, 152 p.
Schruben, P. G., Arndt, R. E., and Bawiec, W. J., 1997, Geology of the conterminous United States at 1:2,500,000 Scale– A Digital Representation of the 1974 P. B. King and H. M. Beikman Map: U.S. Geol. Survey Digital Data Series DDS– 11 (Release 2), CD-ROM (available on World Wide Web at http://minerals.usgs.gov/kb/).
Singer, D. A., 1995,World class base-and precious-metal deposits— a quantitative analysis: Econ. Geology, v. 90, no. 1, p. 88–104.
Stewart, J. H., and Carlson, J. E., 1978, Geologic map of Nevada: U.S. Geol. Survey and Nevada Bur. Mines and Geology Map, scale 1:500,000.
Stewart, J. H., McKee, E. H., and Stager, H. K., 1977, Geology and mineral deposits of Lander County, Nevada: Nevada Bur. Mines and Geology Bull. 88, 106 p.
Wallace, A. R., 1991, Effect of Late Miocene extension on the exposure of gold deposits in north-central Nevada, in Raines, G. L., Lisle, R. E., Schafer, R. W., and Wilkinson, W. H., eds., Geology and Ore Deposits of the Great Basin, Symp. Proc. Volume 1: Geol. Soc. Nevada, Reno/Sparks, Nevada, p. 179–183.
Willden, R., 1964, Geology and mineral deposits of Humboldt County, Nevada: Nevada Bur. Mines and Geology Bull. 59, 154 p.