New Industrial Genetic Type of the Ediacaran Aphanitic Phosphorite Deposits

Abstract

A new industrial genetic (“aphanitic”) type of phosphorite deposits has been identified. In terms of the genetic, tectonic, facies, and geochemical features, this type differs fundamentally from the known micrograined, granular, nodular, shelly, and pebbly phosphorite deposits. They are the first industrial accumulations of phosphorus matter in the history of our planet. Conditions for their accumulation existed only in the Ediacaran period, when mass phosphatization of sediments with the formation of phosphate nodules as ribbon-shaped layers took place under the influence of early diagenetic processes. Phosphates were accumulated in basins with synsedimentary block structure inherited from paleorift structures and seismically active tectonic environment. The multidirectional displacement of blocks generated a complex seafloor relief and facies heterogeneous complex of sediments ranging from reefogenic-stromatolitic sediments in the uplifting areas to pelitic sediments in the dipping areas. The latter areas were marked by a massive input of sedimentary material significantly enriched in the planktonic organic matter. Transformation of organophosphorus compounds during the sulfate reduction promoted the phosphatization of sediments and the formation of aphanitic phosphorites, which differ from other ore types by anomalously high concentrations of As, Sr, and Ba and by anomalously low contents of U and REE.