Other Deposits in and Benefits from Impact Structures

Scrap Gold Business Model

Gold Prospecting and Mining

Get Instant Access

Besides metallic and mineral deposits, as discussed in detail in the above, impact structures may have much potential for other commercial or economic interests. Building materials have - for centuries - been obtained from impact structures, as, for example, witnessed by the century-old churches in Nordlingen in the Ries Crater of southern Germany and in Rochechouart in the meteorite crater of same name in the Haut-Limousin province of southwestern France. Like the medieval castle at Rochechouart, both historical churches have been erected, to a large degree, with blocks of suevite impact breccia. Impact melt rock has been utilised for the construction of a large hotel in the northern part of the Lappajarvi crater in Finland.

Dellen Impact Structure
Fig. 11. Structure map for the region of the Avak impact structure, Alaska, with oil and gas fields superimposed (after Grieve and Masaitis 1994).

Dimension stone has also been quarried in the Vredefort dome, the central uplift region of the Vredefort impact structure (Reimold 1992). Prominent local applications of these granitic gneisses can be viewed in the main terminal building of Johannesburg International Airport, where many supporting columns also display highly instructive "exposures" of pseudotachylitic breccia veinlets, and in the entrance hall to the Council of Mineral Technology (MINTEK) in Randburg. Even the focal point of the Voortrekker historical monument near Pretoria, the sarcophagus, has been constructed from Vredefort granite gneiss. Dimension stone quarrying was abandoned in the Vredefort dome in the late 1990s, but the faces in the remaining quarries provide some of the best and most instructive exposures of Archean basement of the Kaapvaal craton and macro- and meso-deformation of the interior of a central uplift of a large impact structure.

In the Ries crater, suevite impact breccia has found a use in the manufacture of the so-called trass cement. This product has proven particularly useful for repair work on degraded stone monuments. Masaitis (1989) mentioned that some water-rich impact glasses could potentially become useful as swelling materials, along the lines of perlite applications. In Gardnos, a 5-km-diameter, ca. 500 Ma old, impact structure in Norway, a peculiar impact breccia known as Gardnos Breccia (French et al. 1998) is transformed into a variety of utility objects and jewellery. Jewellery has also been made, for several centuries, from tektites, especially Central European tektites (moldavites) from the Czech Republic, Germany, and Austria (see, e.g., papers in Konta 1988). Important sources for drinking or mineralized waters are the Manson structure (Iowa, USA), the Kaluga impact crater (15 km, 380 Ma, Russia), and the Vepriaj crater (8 km, 160 Ma, Lithuania), where high-porosity impact breccias are utilized as storage media. At Logoisk (17 km, 40 Ma, Belarus), thick layers of sand deposited in the crater lake form a useful local groundwater recharge basin and constitute an important source of water (Masaitis 1989). The Manicouagan reservoir in the 100 km wide Manicouagan impact structure in Quebec (Canada) is part of a large hydroelectric power development, and Lake Bosumtwi in Ghana, a 8.5 km diameter lake in the 10.5 km Bosumtwi impact crater, provides the livelihood for a large number of fishing communities along its shore.

Bosumtwi has additional potential in providing a unique recreational-educational area in a rather densely populated area of Ghana, near the major town of Kumasi. Already, a large lake in the Rochechouart structure of France that has been declared a protected national park (Geo-Parc) area is attracting thousands of tourists. The Tswaing meteorite crater in South Africa provides recreational and educational facilities and construction of a museum building is well under way. A number of meteorite craters in Scandinavia are recreational centers for summer as well as winter sports (the Dellen and Siljan areas in Sweden are favourite cross-country skiing areas).

A major tourist attraction is the museum at Meteor Crater in Arizona, and a thriving museum has also been developed in Nordlingen (Ries Crater). Museums and educational displays have either been established already at other impact structures (for example, at Lappajarvi one finds a jogging trail with a series of instructive plaques, and at Steinheim a very instructive and beautifully designed museum can be visited by appointment), or are being developed (e.g., at Tswaing in South Africa where hiking-trails have been laid out, game resettled, and a museum building is constructed; efforts are also made to establish a museum at Bosumtwi in Ghana). In this context, it is particularly evident that meteorite structures in developing countries, even if they are totally devoid of mineralization, may turn out to be highly profitable with regard to their potential as tourist attractions and suitable as outdoor classrooms - both of which are largely lacking in such countries. The large Popigai structure in Siberia has been suggested for World Heritage Site status, because of its unique combination of world-class geology and impact-diamond deposits, for which the term "national treasury" has been coined (Deutsch et al. 2000). However, it is understood that this proposal has not been taken further. In contrast, parts of the Vredefort Dome have been earmarked for dedicated eco-tourism development, have already been declared a national conservancy, and an application for World Heritage status - based on a unique combination of geological, cultural (iron age archaeology) and historic (early gold mining in the Ventersdorp gold field as well as AngloBoer War history) heritage - was submitted to UNESCO in January 2003.

The economic, touristic, and educational potential of meteorite impact structures in all parts of the world cannot be underestimated. Not only do many of the known structures have the potential to generate value in the future, but the commercial gain already derived from active mining of impact structures should make for powerful incentive to consider the prospective benefits of further exploration for still unknown impact structures.

Was this article helpful?

0 0

Post a comment