Preliminary U-Pb Zircon Geochronology of the Eburnean Menongue Igneous Complex, Cassinga Zone, Angolan Shield
DOI:
https://doi.org/10.21701/bolgeomin/136.1/006Keywords:
Menongue Igneous Complex, Cassinga Zone, Angolan Shield, Eburnean Event, U-Pb zircon geochronologyAbstract
The Menongue Igneous Complex (MIC) consists of a set of previously undated plutonic and volcanic rocks located within the Cassinga Zone of the Angolan Shield. The complex comprises granodiorites, monzo- to syenogranites, and subordinate diorites, quartz-diorites, and leucogranites in the plutonic suite, along with andesitic to rhyolitic coherent and pyroclastic volcanic rocks in the volcanic suite. New U-Pb zircon geochronological data obtained as part of the National Geological Plan of Angola (PLANAGEO) reveal crystallization ages ranging from 1982.4±22.9 Ma to 1949.3±10.2 Ma, demonstrating that the magmatic activity responsible for the emplacement of the MIC occurred during the Paleoproterozoic Eburnean Event (ca. 2050 Ma to 1933 Ma in the Angolan Shield). Overlapping crystallization ages of a monzogranite (1968.8±6.2 Ma) and rhyolite (1963.9±2.8 Ma) support field evidence suggesting coeval emplacement of the volcanic and plutonic facies. Additionally, our data show that the magmatism of the MIC is coeval with granitoids and felsic volcanics from Conda, in the northwestern part of the Central Eburnean Zone (1978±11 Ma to 1964±9 Ma), but dismiss previously proposed correlations with felsic (sub)volcanics from Matala, in the Cassinga Zone, and from Chibia-Cainde (1814±8 Ma to 1804±7 Ma), in the southern part of the Central Eburnean Zone. Future detailed whole-rock geochemistry and zircon U-Pb and Lu-Hf studies of the Eburnean record in the Cassinga Zone will help establish the geotectonic significance of the Cassinga Zone in the evolution of the supercontinent Columbia.
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