Evaluation for suitability for geochronology, Ngalia Basin samples

Abstract

Samples were sent to Amdel from Magellan Petroleum to evaluate the suitability of them for geochronology. Thin section samples were prepared and examined with a polarising microscope. To determine the time of deposition of a sediment, the sample must contain an authigenic mineral that formed during the deposition process or immediately after, during diagenesis. The authigenic mineral must also contain K or Rb in sufficient abundance to produce detectable amounts of the radiogenic isotope (Ar or Sr) and the mineral must have remained a closed chemical system since its time of formation.

The samples do not contain any authigenic minerals that could be used for geochronology. The chlorite matrix would not contain K or Rb and has a poor retentivity for the radiogenic isotopes. The samples are therefore unsuitable for dating.