Main empirical regularities of the phosphorus geochemistry in the hypergenesis

Research subject. The study investigates the distribution of phosphorus (as percentages of P 2 O 5 and P) and 4 phosphorus modules introduced by the authors - phosphorus-titanium FTM (P 2 O 5 /TiO 2 ), phosphorus-calcium FCM (P 2 O 5 /CaO), phos-phorus-iron FIM (P2O5/Fe 2 O 3 ) and phosphorus-general-iron FGiM (P 2 O 5 /(Fe2O 3 + FeO)) - in the main types of sedimentary rocks, such as psammites, pelites, carbonates, silicites, in volcanic-sedimentary rocks (tuffoids), as well as in soils, sediments and such specific rocks as nodules and weathering crusts. Methods. On the basis of a large data bank (several tens of thousands of silicate analyses), new clarks of phosphorus were calculated. Clark estimates were based on average median contents for all the above-mentioned rock groups. For the first time, lithochemistry methods were successfully applied to characterize the composition of phosphorites. Correlation analysis was used to identify forms of phosphorus in rocks. Only the most reliable linear correlation coefficients of phosphorus and phosphorus modules with rock-forming components were considered significant - with a significance level no greater than 0.01 and 0.05. Results and conclusions . In some cases, new estimates of clarks differed markedly from the estimates of our predecessors. For a number of objects, clarks were determined for the first time. Interpretation of the revealed relationships allowed us to identify the following main correlations and corresponding forms of phosphorus in sedimentary rocks and their analogues (soils and sediments): positive correlation with CaO - phosphorus in the form of accessory apatite or francolite dominated; positive correlation with Fe 2 O 3 - phosphorus sorbed on iron hydroxides dominates; positive correlation with MgO - phosphorus dominated in the composition of smectite or chlorite, initially sorbed on the clay substance of precipitation; positive correlation with TiO 2 - phosphate sorbed on leucoxene, dominates. Thus, in addition to the previously known calcium and iron hydroxide, a titanium geochemical barrier for phosphorus was first identified.