Classification of sedimentary basins has undergone change with developments in plate tectonics and, in recent years, basin geodynamics. Basin classifications currently in existence were developed for different functions, mostly for petroleum exploration, but all such classifications are based on tectonics and geodynamics. Organic geochemical basin classifications are just now being proposed (Demaison and Huizinga, 1989). St. John et al. (1984) provided a map of both basins and sedimentary provinces and a review of two basin classifications oriented to volume of petroleum content. Their petroleum provinces included giant oil fields, pygmy fields, poor producers, and thick sediment accumulations not bounded by a basin, such as deltas or submarine fans. Although their map and basin summaries show one approach to organizing a classification of basins and petroleum reservoirs, different criteria of unequal weighting were mixed to organize their data set. To the writer's knowledge, the only attempt to approach sedimentary ore deposits on the basis of basin analysis was by Large (1988), who proposed that most sulfide mineralization in sedimentary basins occurs during the thermal stage of extensional basin subsidence (see Chapter 1). However, although Large (1988) has made a contribution by focusing attention on basin- forming processes, he did not consider the role of compres- sional basin formation processes in forming Mississippi Valley-type deposits, for instance (Bethke et al., 1988; Bethke and Marshak, 1990).
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Sedimentary and Diagenetic Mineral Deposits: A Basin Analysis Approach to Exploration
Major oil companies have been utilizing techniques of quantitative basin analysis in exploration for a decade or more. Ore-forming processes in stratiform, sediment-hosted ore deposits commonly involve sedimentary processes, diagenesis, basinal brines, and paleohydrology. Like the maturation and migration of hydrocarbons, their formation is an integral part of basin history. Consequently, applying comprehensive basin analysis to mineral exploration is a logical and helpful approach to understanding sediment- hosted ore deposits and predicting their occurrence, location, and origin.
When the Society of Economic Geologists' Short Course Committee contacted the writer in 1985 to develop a short course on sedimentary processes of ore formation, ft seemed to me that such a course would provide an excellent opportunity to introduce the concept of comprehensive basin analysis as an exploration tool for sediment-hosted mineral deposits. As Sawkins pointed out (1990, p. 333), “Meaningful exploration in extensional tectonic paleo-environments will increasingly require the integration of surface, subsurface, and geophysical data, and enlightened programs of basin analysis similar to those practiced by the petroleum industry will be increasingly needed.”
Sediment-hosted ore deposits include sedimentary gold and other heavy mineral accumulations; evaporites; syngenetic to late diagenetic base metal and barite deposits in clastic and carbonate rocks, including epiclastic volcanic rocks; banded iron formations; Clinton-minette-type iron and manganese ores; unconformity-related and sandstonetype uranium deposits; and Mississippi Valley-type leadzinc deposits. Some sediment -hosted ore deposits were formed at various stages of basin history and are multistage. This short course focuses on (1) the types of basins in which major sediment - hosted ore deposits occur, and (2) the controls of basin types on ore-hosting sedimentary environments and ore-forming processes.
The precise role of sedimentary processes in the formation of ore deposits has been debated by geologists around the world; this debate has affected the manner and success of exploration program s . Skinner (1979, 1987) traced the origins of the polarization of thought on the genesis of ore deposits to Agricola, who expounded on lateral secretion and precipitation of metals from circulating ground waters, and to Descartes, who perceived the earth as an outgassing star and believed that metals were not derived from host rocks. The neptunist theories of Werner (1750-1817) may have evolved from Agricola and the plutonist theories of Hutton (1726-1797) from Descartes. L. C. Graton, whom the Graton-Sales volume Ore Deposits in the United States 1933-1967