Mineralogy of the tertiary clay deposits in Makkah and Rabigh quadrangles, west central Arabian shield, Saudi Arabia

Abstract EN

The mineralogy of the Tertiary clay deposits in Makkah and Rabigh quadrangles was thoroughly investigated by X-ray diffraction and differential thermal and thermo gravimetric analyses in addition to other techniques.

Results show that the investigated samples are predominantly composed of montmorillonite (Ca++ and/or Mg++ rich variety) and kaolinite, associated with subordinate elite and minor chlorite.

Mixed layer montmorillonite-illite is recorded only in two samples.

The relative abundance of these minerals by X-ray diffraction analysis showed that the studied clay deposits are of three types.

The first, which is the most common, is highly montmorillonitic, the second is made up of a mixture of montmorillonite followed by kaolinite and iolite and the third is highly kaolinitic with some montmorillonite.

Generally, kaolinite shows a southward increase in Makkah quadrangle while chlorite, as a minor component, shows a northward increase in Rabigh quadrangle.