Publicaties

Fernandez-Alonso, M.,  Lavreau, J. & Klerkx, J. 1986. ‘GEOCHEMISTRY AND GEOCHRONOLOGY OF THE KIBARAN GRANITES IN BURUNDI, CENTRAL-AFRICA - IMPLICATIONS FOR THE KIBARAN OROGENY’. Chemical Geology 57 (1-2): 217-234. Amsterdam : Elsevier science bv. ISSN: 0009-2541. DOI: 10.1016/0009-2541(86)90104-x.  (PR).

Article in a scientific Journal / Article in a Journal

Recent geological mapping in Burundi defined several generations of granite intrusions in the Burundi Group (middle Proterozoic) according to their structural and geochemical characteristics. Early (Gr1) and synkinematic (Gr2) peraluminous granites are related to an extensional tectonic phase D1 with horizontal deformation and consequent foliation which occurred from ∼ 1400 to ∼ 1260 Ma ago. Peraluminous Gr3 granites (1185 Ma old) are syntectonic to a compressional phase D2 which is characterized by upright folds in NNE and NNW directions. Subsequent alkalic Gr4 granites (∼ 1100 Ma) are associated with transcurrent faults (D′2) of lithospheric scale. The Gr1–3 granitoids display variable initial ratios (0.707–0.735) reflecting the effects of high-level contamination and, to a lesser extent, the composition of their source-region. From isotopic and rare-earth element (REE) data, a large-ion lithophile (LIL)-enriched source of possible Eburnean age, which produced silicic magmas mainly through plagioclase fractionation, is inferred for some granites; however, for most of them the contribution of supracrustal rocks was important. The Gr4 granites have low Sr initial ratios, suggesting a mantle origin.