L'association glauconites—Phosphates—Carbonates (Albien de la Sierra de Espuña, Espagne méridionale)

Abstract

The authors have studied an Albian glauconite—phosphate—carbonate ore in the Sierra de Espuña (Murcia), situated in the betic Cordilleras, nappe of Malaga. The geochemical data concern 76 samples from which the following elements were titrated by spectro-photometric methods: P, Fe, Ti, Al, Mg, Mn, Ca, Na, K, Zn, Li, Ni, Cr and Sr. The percentages of SiO 2, P 2O 5, Al 2O 3, K 2O and total Fe with respect to the insoluble fraction and the CaCO 3, Mn, P 2O 5 amounts permit of partly explaining the phosphate—glauconite bond. The pH and Eh conditions, deduced from vertical variations in the chemistry, are associated with the mineralogic evolution of the glauconites. The authors define the paleoenvironment of this glauconite—phosphate ore deposit. They clearly separate the environment of the genesis from that of sedimentation of the grains. The sedimentation of carbonate—phosphate—glauconitic particles occurred in a confined environment without continental debris. These grains were formed in proximity of the shelf edge. The phosphate and carbonate supplies are attributed to upwelling of deep waters.