Photogeology and structure of the Mozambique orogenic front near Kolo, north-east Tanzania

Abstract

A regional investigation into part of the Mozambique Orogenic Belt in north-east Tanzania is based on photogeological interpretation supported by ground work at selected localities. A 15-mile traverse was made, near Kolo, from the granitoid Tanganyika Shield towards the adjacent orogen in order to establish the structure and tectonic relationships across the front. Three tectonic domains and two subsequent deformations were recognized. One of the domains (Kondoan) corresponds to the tectonically reworked margin of the Shield, which itself consists of a batholithic granite and a marginal series of gneisses (Parangan). Analysis of the structural data obtained on the ground shows that the tectonic domains which were postulated, in part photogeologically, on grounds of distinctive structural styles, display some degree of structural homogeneity. The western domains, which constitute the foreland, are deformed by shearing. The onset of tectonic reworking in the Kondoan domain converts the pre-existing rocks into flaggy gneisses dipping to the east. The axial planes of all the imposed folds dip eastwards towards the orogenic belt and the axes of deformation plunge predominantly towards the east-southeast and south-east, i.e. transverse to the general north-south trend of the orogenic belt. Comparison with other regions suggests that at similar tectonic levels folding, with stretching in the axial direction transverse to the orogenic front, is a common feature in the development of mountain chains.