RE-EVALUATION OF THE SPATIAL AND TEMPORAL DISTRIBUTION OF SEDIMENTARY PHOSPHATE DEPOSITS IN THE LIGHT OF PLATE TECTONICS

A new compilation of paleolatitudes of sedimentary phosphate deposits using worldwide paleomagnetic data confirms the hypothesis that the majority formed at low-latitude locations. A number of Jurassic and possibly some Cambrian deposits formed at intermediate latitudes (30°-50°). Phosphorites range in age from lower Proterozoic to Recent. There has been sporadic deposition of phosphate during this time, as continents drifted into low-latitude locations. It is proposed that there is no direct genetic link between periods of volcanism, orogenesis, formation of evaporites, and episodes of phosphogenesis. All these features are indirectly genetically related through plate tectonics to particular phases in the rifting and separation of continental and oceanic components of plates. In the case of diverging plates, volcanism and tectonism are an early-stage feature, evaporites intermediate-, and phosphorites late-stage features. Models are developed to explain the different sedimentary sequences that develop in north-south and east-west seaways. No model is presently available for epeiric seas. A temporal model is also proposed to explain the distribution of phosphorus in sediments in the last 3,400 m.y. The association of phosphorus with iron and organic matter in the hydrosphere is particularly critical to the model. Even the temporal model is influenced to some extent by plate tectonics. © 1979 Society of Economic Geologists, Inc.