The Monazite deposits of the Vanrhynsdorp division, Cape Province

Monazite occurs with apatite, zircon, iron and copper minerals in hydrothermal lodes in the Archaean Complex. The mineralisation appears to be related to structural features and hydrothermal alteration of a porphyroblastic granite-gneiss. There are three primary and two placer occurrences. The rare phenomenon the basal pinacoid, their properties. Except for monazite, which exhibits of polysynthetic twinning parallel to the ore-minerals are normal in all Geographically, the occurrences are near the southern extremities of the Kamiesberge where they disappear beneath the Knersvlakte peneplane, leaving an inselberg topography controlled by the semi-arid climate. Geologically the area is one in which the Archaean basement has been exposed through the removal of overlying Nama and younger sedimentary formations, some of which remain as outliers. The Archaean rocks, because they present certain features which are inconsistent with the intrusion of primary granites into metamorphic rocks, are believed to have formed by regional granitisation of the Malmesbury Formation. The truncation of one ore-body by the pre-Nama erosion surface indicates a pre-Nama age for the mineralisation, and placer deposits of monazite and zircon have been located in the Nama sediments. Controls have been established to guide the search for further primary occurrences of radioactive minerals, and suggestions are made accordingly for the continued survey of the area.Dissertation (MSc)--University of Pretoria, 1959.GeologyMScUnrestricte