Abstract
Geologic maps are a fundamental data source used to define mineral-resource potential tracts for the first step of a mineral resource assessment. Further, it is generally believed that the scale of the geologic map is a critical consideration. Previously published research has demonstrated that the U.S. Geological Survey porphyry tracts identified for the United States, which are based on 1:500,000-scale geology and larger scale data and published at 1:1,000,000 scale, can be approximated using a more generalized 1:2,500,000-scale geologic map. Comparison of the USGS porphyry tracts for the United States with weights-of-evidence models made using a 1:10,000,000-scale geologic map, which was made for petroleum applications, and a 1:35,000,000-scale geologic map, which was created as context for the distribution of porphyry deposits, demonstrates that, again, the USGS US porphyry tracts identified are similar to tracts defined on features from these small scale maps. In fact, the results using the 1:35,000,000-scale map show a slightly higher correlation with the USGS US tract definition, probably because the conceptual context for this small-scale map is more appropriate for porphyry tract definition than either of the other maps. This finding demonstrates that geologic maps are conceptual maps. The map information shown in each map is selected and generalized for the map to display the concepts deemed important for the map maker’s purpose. Some geologic maps of small scale prove to be useful for regional mineral-resource tract definition, despite the decrease in spatial accuracy with decreasing scale. The utility of a particular geologic map for a particular application is critically dependent on the alignment of the intention of the map maker with the application.
Similar content being viewed by others
References
Bonham-Carter G. F. 1994, Geographic Information Systems for geoscientists: Modelling with GIS. Pergamon Press, Oxford, p 398
Chorlton, L. B., compiler, 2004a, Generalized geology of the world: Felsic and/or intermediate magmatic domains subdivided by age: Geol. Survey Canada, Available by Request, Intended Scale: 1:35,000,000
Chorlton, L. B., compiler, 2004b, Generalized geology of the world: Vector and attribute data for bedrock domains in GIS Format; Geol. Survey Canada, unpubl., Intended Scale: 1:35,000,000
Chorlton, L. B., Sinclair W. D., and Laramée, R. M., 2002, Databases of known deposits; World minerals geoscience database project, in Schulz, K. S., and Briskey, J. A., eds., Agenda, Extended Abstracts, and Biographies for a Workshop on Deposit Modeling, Mineral resource Assessment, and the use in Sustainable Development: U. S. Geol. Survey, Open-File Rept. 02-423, p. 74–75
Kemp, L. D., Bonham-Carter, G. F., Raines, G. L., and Looney, C. G., 2001, Arc-SDM: Arcview extension for spatial data modelling using weights of evidence, logistic regression, fuzzy logic and neural network analysis. http://www.ige.unicamp.br/sdm/default_e.htm, last accessed 28 December 2006
King, P. B., and Beikman H. M., 1974, Geologic map of United States: U.S. Geol. Survey, 3 sheets, scale 1:2,500,000
Landis J. R., Koch G. G. 1977, The measurement of observer agreement for categorical data Biometrics 33:159–174
Levin S. A. 1992, The problem of pattern and scale in ecology: The Robert H. MacArthur Award Lecture Ecology 73(6):1943–1967
Mutschler, F. E., Ludington S., and Bookstrom A. A., 1999, Giant porphyry-related metal camps of the world––a database: http://geopubs.wr.usgs.gov/open-file/of99-556/ and database, last accessed 28 December 2006
Nykänen, V., and Raines G. L., 2007, Quantitative analysis of scale of aeromagnetic data raises questions about geologic-map scale: Natural Resources Research, v. 15, no. 4, p. 213–222
Raines, G. L., and Bonham-Carter, G. F., 2006, Exploratory spatial modelling demonstration for Carlin- type deposits, central Nevada, USA, using Arc-SDM, in Harris, J. R., ed., GIS Applications in Earth Sciences: Geol. Assoc. Canada, Spec. Pub. 44, p. 23–52
Raines G. L., Mihalasky M. J. 2002, A reconnaissance method for regional-scale mineral-resource assessment, based exclusively on geologic-map data Natural Resources Research 11(4):241–248
U.S. Geological Survey National Mineral Assessment Team, 1998, Assessment of undiscovered deposits of gold, silver, copper, lead, and zinc in the United States: U.S. Geol. Survey Circ. 1178, 29 p. and database
Acknowledgments
We would like to acknowledge the thoughtful and helpful advice that Rob Robinson of the USGS provided in the course of this research.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Raines, G.L., Connors, K.A. & Chorlton, L.B. Porphyry Copper Deposit Tract Definition – A Global Analysis Comparing Geologic Map Scales. Nat Resour Res 16, 191–198 (2007). https://doi.org/10.1007/s11053-007-9042-9
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11053-007-9042-9