Grieve presents a chapter that represents an update of previous reviews (e.g. Grieve and Masaitis, 1994 ; Grieve, 2005 ; Reimold et al ., 2005 ) of natural resources associated with some terrestrial impact structures. This chapter, however, is not totally comprehensive with respect to the full economic value of terrestrial impact structures. A more comprehensive list is given in Reimold et al., which lists 56 impact structures with ‘economic interests’ , including structures that provide sites for recreational activities and/or serve as tourist attractions. This chapter also does not consider those structures that have been, or are being, exploited as a source of aggregate, lime or stone for building material (e.g. Ries in Germany, Rouchechouart in France) or are a source of groundwater or serve as reservoirs for hydro - electric power generation (e.g. Manicouagan in Canada, Puchezh - Katunki in Russia). The economic value of such impact structures, however, can be considerable. For example, the electricity generated by the Manicouagan reservoir can reach the order of 5000 GWh yr − 1 sufficient to supply power to a small city and worth approximately US$300 million per year, at current residential electricity prices in Canada.
Previously, Grieve and Masaitis (1994) and Grieve (2005) considered resource deposits at terrestrial impact structures in the following order: progenetic, syngenetic, epigenetic. Progenetic economic deposits are those that originated prior to the impact event by purely terrestrial concentration mechanisms. The impact event caused spatial redistribution of these deposits and, in some cases, brought them to a surface or near - surface position, from where they can be exploited. Syngenetic deposits are those that originated during the impact event, or immediately afterwards, as a direct result of impact processes. They owe their origin to energy deposition in the local environment from the impact event, resulting in phase changes and melting. In recent years, there has been greater recognition of the role for post - impact hydrothermal activity at impact structures
Post - impact hydrothermal deposits are a logical result of heating due to the impact process and, thus, are considered here as syngenetic deposits. Thus, the remobilization of some progenetic deposits has blurred the separation between progenetic and syngenetic deposits. Epigenetic deposits result from the formation of an enclosed topographic basin, with restricted sedimentation, or the long - term flow of fluids into structural traps formed by impact structures. Commercial accumulations of hydrocarbons at terrestrial impact structures can result from a number of processes related to impact and are considered separately.
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