Rb-Sr age from the Choma-Kalomo batholith, evidence for the irumide belt in southern Zambia, Africa
The northeast trending Irumide mobile belt (1100-1300 my) of eastern Zambia is generally believed to reappear southwest of the cross-cutting, west to northwest trending Zambezi-Katanga belt of Pan African age (350-700 my). The on-strike relationship of the two segments of the Irumide belt on either side of the Zambezi-Katanga belt is often cited as proof of an ensialic, rather than interplace, origin for the Zambezi-Katanga mobile belt. However, the two segments are correlated largely on the basis of similar lithology and structure and their parallel northeast-trending structural grain. Some K-Ar mineral dates (1100-1150 my) and a Rb-Sr whole-rock isochron age of 1355 +/- 28 my (Cahn and Snelling, 1984) establish an Irumide age for the northeastern segment, but a similar age for the southwestern segment is based on a single K-Ar muscovite date. No Irumide age basement rocks have been found within the Zambezi-Katanga belt between the two segments. The >7500 km/sup 2/ Choma-Kalomo batholith complex of southern Zambia intrudes the pronounced northeast-trending foliation and early isoclinal folds of the high-grade metamorphic rocks of the southwestern segment. Seven of eight whole-rock samples collected from a quarry near 30 km south of Choma define a linear array on a Rb-Sr evolution diagram with a Model III age of 1227 +/- 32 my, confirming the Irumide age of the southwestern segment. The relatively high initial /sup 87/Sr//sup 86/Sr ratio of 0.7120 +/- .0009 suggests the granitic magma was derived by partial melting of radiogenic continental crust.
- Research Organization:
- Lamont-Doherty Geological Observatory, Palisades, NY (USA)
- OSTI ID:
- 6649768
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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AFRICA
AGE ESTIMATION
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMISTRY
DEVELOPING COUNTRIES
GEOCHEMISTRY
GEOLOGIC MODELS
IGNEOUS ROCKS
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
PETROGENESIS
PLATE TECTONICS
PLUTONIC ROCKS
QUANTITATIVE CHEMICAL ANALYSIS
ROCKS
RUBIDIUM ISOTOPES
STRONTIUM ISOTOPES
TECTONICS
ZAMBIA