The potential for environmentally sound development of marine...

The potential for environmentally sound development of marine deposits of potassic and phosphatic minerals offshore, southern Africa
Auteur(s) / Author(s)
COLES S. K. P. (1) ; WRIGHT C. I. (1) ; SINCLAIR D. A. (1) ; VAN DEN BOSSCHE P. (1) ;
Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)
(1) Council for Geoscience, Marine Geoscience Unit, Bellville, AFRIQUE DU SUD

Résumé / Abstract
Extensive potassium and phosphorous-rich mineralization occurs on the outer continental shelf of the southern and west coasts of South Africa and Nambia. This article reviews the potential of exploiting these deposits in an environmentally sound manner for the manufacture of fertilizer. At present, reserves of potash and phosphate fertilizer are exploited from terresterial deposits, the majority being surface mined. The use of fertilizer in South Africa has shown no growth in the past 13 years, and, in some years, usage has even declined. On average, over the last decade, South Africa has consumed 2 million Mt of fertilizer (including nitrogen) per annum, the vast majority of phosphate fertilizer being produced by FOSKOR from the Phalaborwa Igneous Complex. Potash fertilizer is imported into South Africa. Although fertilizer consumption is expected to decrease in the short-term, there are good future prospects for the domestic and international fertilizer market. Considerable research into both glauconitic (containing K2O) and phosphatic deposits along the southern African continental shelf indicate that these sedimentary deposits have a complex genesis and mineralization. Of the total K2O reserves of 1300 million Mt on the southern African margin, 1000 million Mt is located off the southern African west coast, and the remainder situated on the Agulhas Bank. The largest glauconite concentration (±300 million Mt K2O) off southern Africa lies west of Saldanha Bay, South Africa. The distribution of P2O5 off southern Africa is dominated by the vast deposit between Walvis Bay and Luderitz, Nambia. This reserve is estimated to contain 1000 million Mt of greater than 5% P2O5 in a relatively small area of about 10000 km2. The phosphorite deposit south of Saldanha Bay constitutes a reserve of ±3500 million Mt of apatite and the deposit on the Agulhas Bank comprises 5500 million Mt. The phosphate deposit off Saldanha Bay occurs as an extensive, low to edium grade deposit. Although vast resources of potash and phosphatic minerals occur along thesouthern African outer continental shelf the expensive nature of marine exploitation may render most of these deposits, especially the phosphates, subeconomic. The low price of fertilizer andextensive nature on the onland deposits, although confined to a small number of countries, mean that it will not be financially viable to extract these deposits. Assuming high grade glauconitic sand with the right composition can be located, the high market price indicates good future prospects for these potash deposits.

Revue / Journal Title
Marine georesources & geotechnology ISSN 1064-119X

http://cat.inist.fr/?aModele=afficheN&cpsidt=13839730