Economic Mineral Deposits in Impact Structures: A Review Wolf Uwe Reimold1, Christian Koeberl2, Roger L. Gibson1, and Burkhard O. Dressler1,3 1Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, P.O. Wits 2050, Johannesburg, South Africa ([email protected]; [email protected]) 2Department of Geological Sciences, University of Vienna, Althanstrasse. 14, A-1090 Vienna, Austria ([email protected]) 3185 Romfield Circuit, Thornhill, Ontario, Canada, L3T 3H7 ([email protected]) Abstract. Many large meteorite impact structures throughout the world host mineral resources that are either currently mined or have the potential to become important economic resources in the future. The giant Vredefort-Witwatersrand and Sudbury impact structures underline this statement, because of their enormous resources in gold and uranium, and nickel, copper, and PGEs, respectively. In relation to impact, three basic types of ore deposits in impact structure settings have been distinguished: (1) progenetic (i.e., pre-impact) deposits that already existed in the target regions prior to an impact event, but may have become accessible as a direct result of the impact; (2) syngenetic (syn-impact) deposits that owe their existence directly to the impact process, and (3) epigenetic (immediately post-impact) deposits that result from impact-induced thermal/hydrothermal activity. In addition to metalliferous ore deposits related to impact structures, impact structure-hosted epigenetic hydrocarbon deposits are reviewed and are shown to make a major contribution to the North American economies. Non-metallic resources, such as minerals derived from crater-lake deposits, dimension stone, and hydrological benefits, may also be derived from impact structures, and the educational and recreational value of many meteorite impact craters can be substantial. Undoubtedly, impact structures - at least those in excess of 5-10 km diameter - represent potential exploration targets for ore resources of economic magnitude. This important conclusion must be communicated to exploration geologists and geophysicists. On the other hand, impact workers ought to be familiar with already established fact concerning ore 480 Reimold et al. deposits in impact environments and must strive towards further understanding of the ore generating processes and styles of emplacement in impact structures. 1 Introduction Currently some 170 impact structures are known on Earth – presumably representing a mere fraction of the entire terrestrial cratering record for a meteorite impact structure list (e.g. Impact database) Other solid bodies of the Solar System display surfaces that have been thoroughly cratered, but have barely been accessible for detailed impact geological study. Only the Moon and Mars have been – and will in future be – targets of direct geological study, besides probing of large, impact-cratered asteroids. Future Space exploration, and perhaps habitation of other planetary bodies, will have to rely on natural resources obtained in Space. This also includes asteroids, the direct study of which has only been resumed in 2001 with the spectacular soft landing of the Shoemaker-NEAR spacecraft on the asteroid 433 Eros. The study of comets recently experienced a setback when NASA’s Contour probe perished shortly after take-off, but several other projects (e.g., NASA’s Stardust and ESA’s Rosetta missions) currently attempt to provide new insight into the composition of cometary bodies. Mining of Lunar and Martian surfaces, as well as of asteroidal bodies, for the procurement of raw materials required in Space, has been the subject of discussions for years (e.g., Lewis 1997, and references therein). Thus, a look at the economic potential of impact structures and impactites must be an integral part of any comprehensive treatise of impact phenomena. Grieve and Masaitis (1994), in their benchmark account of impact-related ore deposits, stated that “impact is an extraordinary geologic process involving vast amounts of energy, resulting in near instantaneous rises in temperature and pressure, and in the structural redistribution of target materials“. In essence, impact is catastrophic and destructive, but it leads to the formation of specific rock units and may – directly or indirectly − trigger mineralization processes, both of which may have considerable economic significance. Here, we provide a review of the existing knowledge about ore-forming processes related to impact and describe the mineralization environments known from quite a number of terrestrial impact structures. Table 1 provides some pertinent detail about those impact structures refered to in the text. Economic Mineral Deposits in Impact Structures: A Review 481 Table 1. (continued on next two pages) Some pertinent information about those impact structures discussed in the text. Diam. Age Crater Name Long. Lat. Country Economic Interest [km] [Ma] Ames 36o15'N 98o12'W Oklahoma 16 470±30 Hydrocarbons USA Avak 71o15'N 156o38'W Alaska USA 14 ca. 460 Hydrocarbons Beyenchime 71o00'N 121o40'E Russia 8 40±20 Pyrite (minor) Salaatin Boltysh 48o45'N 32o10'E Ukraine 24 65.2±0.6 Phosphorite; hydrocarbons Bosumtwi 06o30'N 01o25'W Ghana 10,5 1,07 Water reservoir; education /recreation; traces of agate; fishing Brent Crater 46o05'N 78o29'W Ontario 3,8 396±20 Crater sediment Canada Carswell 58o27'N 109o30'W Saskatch 39 115±10 Uranium Canada Charlevoix 47o32'N 70o18'W Quebec 54 342±15 Ilmenite Canada Chesapeake 37o17'N 76o01'W Virginia 80 35.5±0.3 Water reservoir; education Bay USA /recreation; traces of agate; fishing Chicxulub 21o20'N 89o30'W Mexico 180 65.00±0.05 Hydrocarbons; impact diamonds Cloud Creek 43o10.6'N 106o42.5'W Wyoming ca. 7 ca. 190±20 Hydrocarbons USA Crooked Creek 37o50'N 91o23'W Missouri 7 320±80 Pb-Zn USA Decaturville 37o54'N 92o43'W Missouri 6 <300 Pb-Zn USA Dellen 61o48'N 16o48'E Sweden 19 89.0±2.7 Summer/winter sport; hydropower reservoir Gardnos 60o39'N 09o00'E Norway 5 500±10 Gardnos Breccia (decorative arts) Houghton 75o22'N 89o41'W Nunavut 24 23±1 Epigenetic overprint Dome Canada Ilyenits 49o07'N 29o06'E Ukraine 8,5 378±5 Agate (traces) Kaluga 54o30'N 36o12'E Russia 15 380±5 Water 482 Reimold et al. Diam. Age Crater Name Long. Lat. Country Economic Interest [km] [Ma] Kara 69o06'N 64o09'E Russia 65 70.3±2.2 Impact diamonds, Pyrite (minor) Karla 54o55'N 48o02'E Russia 10 5±1 Mercury Kentland 40o45'N 87o24'W Indiana 13 97 Pb-Zn USA Lake St. Martin 51o47'N 98o32'W Manitoba 40 220±32 Gypsum, anhydrite Canada Lappajärvi 63o12'N 23o42'E Finland 23 73.3±5.3 Summer and winter sport; education/recreation; building stone Logoisk 54o12'N 27o48'E Belarus 15 42±1 Phosphorite; amber; groundwater recharge basin Lonar 19o58'N 76o31'E India 1,8 0.05±0.01 Trona; post impact hydrothermal alteration Manicouagan 51o23'N 68o42'W Quebec 100 214±1 Water reservoir; hydro Canada power Manson 42o35'N 94o33'W Iowa, USA 35 73.8±0.3 Epigenetic overprint Marquez Dome 31o17'N 96o18'W Texas, USA 12,7 58±2 Hydrocarbons Meteor Crater 35o02'N 111o01'W Arizona 1,2 0.049 Silica; museum USA ±0.003 Morokweng 26o28'S 23o32'E South Africa 70 145±1 None (suspected Ni/PGE mineralization) Newporte 48o58'N 101o58'W North 3,2 <500 Hydrocarbons Dakota USA Obolon 49o35'N 32o55'E Ukraine 20 169±7 Hydrocarbons (oil shale) Popigai 71o39'N 111o11'E Russia 100 35.7±0.2 Impact diamonds Puchezh- 56o58'N 43o43'E Russia 80 167±3 Impact diamonds, mercury; Katunki zeolite Ragozinka 58o44'N 61o48'E Russia 9 46±3 Diatomite Red-Wing 47o36'N 103o33'W North 9 200±25 Hydrocarbons Creek Dakota USA Ries 48o53'N 10o37'E Germany 24 15.1±0.1 Impact diamonds; (Nördlinger bentonite; lignite; building Ries) stone; museum; epigenetic overprint Economic Mineral Deposits in Impact Structures: A Review 483 Diam. Age Crater Name Long. Lat. Country Economic Interest [km] [Ma] Rochechouart 45o50'N 00o56'E France 23 214±8 Education/recreation/ Museum; building stone Rotmistrovka 49o00'N 32o00'E Ukraine 2.7 120±10 Hydrocarbons Sääksjärvi 61o24'N 22o24'E Finland 6 ca. 560 Agate (traces); recreation (summer/winter sport) Serpent Mound 39o02'N 83o24'W Ohio, USA 8 <320 Pb-Zn Sierra Madera 30o36'N 102o55' Texas USA 13 <100 Hydrocarbons Siljan 61o02'N 14o52'E Sweden 65 362±1 Pb-Zn; winter sport Steen River 59o30'N 117o30'W Alberta 25 91±7 Hydrocarbons Canada Steinheim 48o41'N 10o04'E Germany 3,8 15±1 Museum Basin Sudbury 46o36'N 81o11'W Ontario ±250 1850±3 Ni, Cu, PGE; minor Cu-Pb- Canada Zn; impact diamonds Ternovka 49o01'N 33o05'E Ukraine 11 280±10 Iron ore; impact diamonds; (Terny) uranium Tookoonooka 27o07'S 142o50'E Australia 55 128±5 Possible hydrocarbon target Tswaing 25o24'S 28o05'E South Africa 1.13 0.22±0.05 Trona; (Pretoria education/recreation/ Saltpan) Museum Ust-Kara 69o18'N 65o18'E Russia 25 70,3 Pyrite (minor) Vepriai 55o05'N 24o35'E Lithuania 8 160±10 Water reservoir Viewfield 49o35'N 103o04'W Sasketch 2,5 190±20 Hydrocarbons Canada Vredefort- 27o00'S 27o30'E South Africa 250-300 2020±5 Gold, uranium; Witwatersrand education/recreation; Kibaran bentonite Zapadnaya 49o44'N 29o00'E Ukraine 3,2 165±5 Impact diamonds Zhamanshin 48o24'N 60o58'E Kazakstan 14 0.9±0.1 Bauxite (Unconfirmed impact structures mentioned in the text are Bangui (Central African Republic/DR Congo), Calvin (Michigan, USA), and Pechenga (northern Scandinavia)). 484 Reimold et al. It was the interest in finding a potentially economic iron, nickel and platinum group element (PGE) deposit that, early in the last century, led Daniel Moreau Barringer to devote himself and his resources to the investigation of Meteor Crater in Arizona (Barringer 1906; Hoyt 1987).