Abstract

A meeting on ‘Phosphatic and Glauconitic Sediments‘; is particularly appropriate in view of the considerable but often widely scattered literature, both published and unpublished, that has become available on this subject in recent years. Phosphatic and glauconitic sediments are those in which the calcium phosphate mineral, francolite, a variety of apatite and the hydrated potassium-iron silicate, glauconite, are prominent constituents. As such they have intrigued geologists for many years, particularly in connection with the nature of the chemical reactions responsible for their formation and the relative importance of individual parameters controlling these reactions. These sediments are widely distributed in the geological column, particularly in strata of Cambrian, Cretaceous–Lower Tertiary, and, in the case of phosphatic sediments, Permian and Miocene–Pliocene age. The association of apatite and glauconite in sediments has frequently been reported but integrated studies of the two minerals have, until recently, been comparatively few. These have shown that the minerals form by direct precipitation from sea water at the sediment/water interface, or diagenetically by interstitial replacement or replacement of pre-existing sediment.

Phosphatic sediments are of great economic importance since they provide most of the raw material, known commercially by the imprecise term ‘phosphate rock’, for the manufacture of phosphate fertilizers and some phosphorus-based chemicals. For example, sedimentary formations accounted for c. 16 million tonnes (c.89%) of the total world output of c. 18 million tones of P in 1978. Although production is dominated by USA, the USSR and Morocco, there are other important producers of phosphate rock. In marked

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