The geology of part of the Kunene basic complex, Kaokoveld, South West Africa

Abstract

Abstract provided by author:

Ring fractures, produced by northwest-southeast compression, and consequent large scale faulting in a near-easterly direction, combined with upward pressure of an intracrustal troctolitic anorthosite magma, enabled this magma to be intruded into the massive anorthosite in the form of a succession of concentric sheets, dipping steeply outward. The troctolitic anorthosite (Bushveld type) is Precambrian in age. Various late - to postkinematic basic and ultrabasic intrusives, consisting of dunite and peridotite, serpentinized equivalents of these, norite, troctolite, and anorthositic gabbro are described. These are considered to be products of remobilization of a deepseated differentiate of the Complex

Twenty-eight whole rock chemical analyses are presented and discussed : twenty-five of anorthosites, one of dunite, one of a mafic dyke, and one of troctolite

Geologically, the most significant rocks are the anorthosites since they, in part, make up a portion of the Kunene Basic Complex. In contrast to previous publications it was found desirable, on the basis of interpretation of field evidence, to separate the massive anorthosite from the Kunene Basic Complex, which in this thesis embraces the troctolitic anorthosite and some allied rocks only. An attempt is made to show how the undoubtedly older massive anorthosite (Adirondack type) may be the product of calcium metasomatism. Since there is no evidence of limestone metasomatism, the hypothesis is based on the contention that mixed gneiss constituted the parent rock