Revista Brasileira de Geofísica
Print version ISSN 0102-261X
MURTON, Bramley J.. A global review of non-living resources on the extended continental shelf. Rev. Bras. Geof. [online]. 2000, vol.18, n.3, pp. 281-306. ISSN 0102-261X. http://dx.doi.org/10.1590/S0102-261X2000000300007.
This contribution reviews the current state of knowledge of non-living resource potentials within the extended "legal " continental shelf (ELCS). The ELCS lies beyond the 200 nautical mile jurisdiction of nation states' exclusive economic zones, but within the outer limits defined by the criteria established under the 1982 United Nations Convention on the Law of the Sea, Article 76 (1982). The offshore non-living resource potentials are based on a statistical evaluation of known occurrences and reserves, the geologic environments favourable for their formation, models for sediment type and thickness, and basement composition. The result is an assessment of the potential for non-living marine resources to occur. The resources are divided into different types, based on their origin. Each is treated separately with a brief description of modes of formation followed by location, grade and resource estimate. Because placer deposits, comprising heavy minerals, gold and diamonds, are limited to near-shore areas they have negligible resource potential in the ELCS regions. Similarly, because phosphorite occurs mainly in the equatorial oceans between 400 m and 1,500 m depth, they too have limited resource potential in ELCS areas. Evaporite deposits occur on many continental margins. However, they only occur within ELCS regions off eastern North America and western central Africa, where their resource potential is low. Polymetallic sulphides (PMS) are formed at volcanically active plate boundaries. With the exception of parts of the west Pacific and off the western coast of North America, where volcanically active plate boundaries are close to the continental margin, PMS resources are low in the ELCS regions. The major resource potential within the ELCS regions is held in iron-manganese nodules and crusts, oil, gas and gas hydrates. Four elemental metals are the main components of value in manganese nodules and crusts: manganese, copper, nickel and cobalt. Extrapolating known occurrences world wide, the total amount of these nodules and crusts within the ELCS regions may be as much as thirteen billion tonnes. Conventional oil and gas comprise an estimated 106 b.b.o.e. (billion barrels of oil equivalent) with a similar estimate of 115 b.b.o.e. for gas hydrates. In total, the resource potential (excluding recovery and production costs) contained within the ELCS regions of the world amounts to an estimated US$ 11,934 trillions (at today's raw commodity prices).
Keywords : Extended "legal " continental shelf; Marine Minerals Resources.