Eliminación de fosfatos en muestras palinológicas

Abstract

The observation of palynological material from siliceous sediments needs separation and isolation techniques, which include a preliminary chemical treatment to eliminate mineral phases. The final residue, obtained after several treatments, is composed by a mixture of organic, vegetal and animal materials. In some cases the presence of mineral phases such as crystalline phosphates formed during the chemical attack is also confirmed. The elimination of these compounds from the palynological materials is very important for an adequate observation, study and count under the optical microscope. The aim of this work is to study and describe the newly formed phosphates during chemical treatment and to formulate a valid method for its elimination without damage of the playnological material. Two samples (Keuper facies, Upper Triassic) have been selected due to their content in the previously described problematic phosphate phases. XRD, XRF and optical microscopy data show that the newly formed phosphate phases, after the acid attack with HF (40% dissolution), are crandallite-gorceixite. After several laboratory attempts, the elimination of the problematic phases has been made successfully treating the samples with a final dissolution of HCl at 33%. All the morphological characteristics of the palynological material have been preserved properly.