Rare earth and high field strength element partitioning behaviour in diagenetically precipitated titanites

Titanite occurs as a pore filling cement phase in Permian sandstones at the Cock of Arran, Scotland. Wavelength dispersive-electron probe microanalysis and ion probe microanalysis reveals that the titanites contain appreciable concentrations of rare earth and high field strength elements which are partitioned between well developed sector zones. Sector zoning occurs as a result of differential incorporation of impurity elements between different growing titanite crystal faces. In this example the sector zonation is considered to be the result of different crystal faces exposing different lattice site configurations to the growth medium with different propensities for impurity element incorporation. Temporal variations in rare earth element chemistry are also present and suggest that the effective partition coefficients (mineral/fluid) are significantly higher for the HREE than the LREE in this system.