Natural SciencesEarth SciencesGeologyGeochemistryInorganic ChemistryMineralogyCarbonate MineralogyCarbonate MineralsMineral ChemistryMineral GenesisMineral GeochemistryPhosphate MineralsApatite FormationApatite MineralogyCalcite MineralogyPhosphate Mineral ChemistryPhosphate Mineral GeochemistryPhosphorite DepositsPhosphorite Genesis
A portion of the system Na/sub 3/PO/sub n4/-CaCO/sub 3/)-H/sub 2/0 was investigated at low temperatures. The formation of a carbonate apatite by phosphate replacement of calcite in alkaline solutions and the structural positions of the carbonate groups are discussed. Data indicate calcite replacement by low concentrations of phosphate to be the principal mechanism of formation of marine phosphorite deposits. (auth)