Die stollingskompleks Kaap Kruis, Suidwes-Afrika

Abstract

Abstract provided by author:

The inward dip of the layers of basalt, sills of felsite and a differentiated gabbro-sill, is attributed to the bending down of the layers during the gradual subsidence into a chamber of granitic magma. Granite extends over the central part of the Complex. Fractures caused by subsidence were passively filled by granitic magma

The cone-dykes of porphyric granophyre and micro-foyaite respectively, are situated in the northern portion of the Complex. Three plugs of alkali-syenite occur lineally arranged near to the sand-covered contact of the northern and southern portions of the Complex. Except for the cone-dyke of micro-foyaite, the felspathoid-bearing rocks are limited to a stockwork of foyaite with xenoliths of tinquaite and essexite

The tholeiitic magma is considered to have originated near to the mantle-zone of the earth The granitic magma has possibly formed in the mobilized roots of the Damara-orogenic. The writer accepts that a magmatic carbonatite played an important role during the petrogenesis of the felspathoid-bearing, leucocratic rocks

The geomorphological circumstances that caused the considerable deposits of halite in the Cape Cross pan, are controlled by the structure of the Igneous Complex

Some fourteen new rock-analyses are helpful in understanding the chemical affinity. The possible trend of differentiation and the relation between the tholeiitic, granitic and alkaline rocks is illustrated by a number of variation diagrams