RODINGITE OCCURRENCES IN SOME ARCHAEAN ULTRAMAFIC COMPLEXES IN THE BARBERTON MOUNTAIN LAND, SOUTH-AFRICA

Archaean layered ultramafic complexes in the Barberton greenstone belt, South Africa, consisting mainly of serpentinized dunite, harzburgite, and orthopyroxenite, as well as websterite and gabbroic rocks, contain dykes and irregular pods and lenses of rodingite. The mineralogy of the rodingites includes the prominent development of a wide range of calcium-rich minerals such as hydrogrossular, hibschite, vesuvianite, diopside, nephrite, prehnite, zoisite, and others. In addition to providing eleven chemical analyses of rocks representative of the Stolzburg Ultramafic Complex, five analyses of rodingites from the vicinity are listed for comparison with similar rocks from elsewhere in the world. A brief review of the nature of rodingites, in general, as well as the various proposals that have been offered for their genesis, are included. It is concluded, from investigations of the chemistry and mineralogy of various rocks in the Barberton layered complexes, that Ca-metasomatism, related to serpentinization of the ultramafic country rocks, played a dominant role in the development of these rodingite occurrences. © 1979.