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Airborne geophysics and geochemistry provide new insights in the intracontinental evolution of the Mesoproterozoic Kibaran belt (Central Africa)

Published online by Cambridge University Press:  01 March 1998

M. FERNANDEZ-ALONSO  and
K. THEUNISSEN
M. FERNANDEZ-ALONSO
Affiliation:
Royal Museum for Central Africa, Department of Geology, Steenweg op Leuven 13, B-3080 Tervuren, Belgium
K. THEUNISSEN
Affiliation:
Royal Museum for Central Africa, Department of Geology, Steenweg op Leuven 13, B-3080 Tervuren, Belgium
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Abstract

The Mesoproterozoic Kibaran belt in southwest Rwanda (Central Africa) consists of two contrasting metamorphic sequences. The first is essentially composed of weakly deformed, low-grade pelitic rocks with many quartzitic intercalations and some volcano-sedimentary sequences. The second consists of medium- to high-grade metamorphic metasediments and gneisses, intruded by sheared granitoids. Existing geological maps are of limited use in understanding the evolution of this part of the Kibaran belt. A combination of airborne γ-spectrometry data with Landsat TM imagery readily distinguishes known lithologies, and in particular detects two distinct granite types. Trace element data for one granite type does not correspond with known petrochemical trends of Kibaran granites, and may belong to a pre-Kibaran basement. The combining of these data with a recently published schematic geological map of the northeast Kibaran belt and re-interpreted field structural data, suggests a model for the Kibaran orogenic evolution in terms of extensional detachment tectonics and associated metamorphic core complexes.

Type
Research Article
Information
Geological Magazine , Volume 135 , Issue 2 , March 1998 , pp. 203 - 216
Copyright
© 1998 Cambridge University Press

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