Structure, age, and regional significance of syntectonic augen gneisses in the Pan-African Zambezi belt, south-central Zambia

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6594769

Hanson, R E; Wilson, T J; Wardlaw, M S

The Pan-African Zambezi belt in Zambia contains two major augen gneiss units that are elongated parallel to regional strike. These were previously regarded as slices of sialic basement structurally interleaved with Katangan metasedimentary rocks. New field and geochronologic evidence suggests that the gneisses are syntectonic granites intruded as large concordant sheets during main-phase (D/sub 1/) Pan-African deformation. A pervasive, horizontal or shallowly plunging mineral lineation on S/sub 1/ in the gneisses indicates that the parent granites were injected along major zones of transcurrent shear. The northern gneiss unit shows local discordant contacts against, and contains xenoliths of, adjacent Katangan rocks. Large, partly polygonized K-spar augen in the gneiss are wrapped around by S/sub 1/ and offset by microfractures antithetic to S/sub 1/. Finer grained granites intruding the gneiss are penetratively foliated to nondeformed, indicating that they were injected at various times relative to D/sub 1/. In the more intensely deformed southern gneiss unit, local pods of protomylonitic flaser gneiss grade into mylonites containing asymmetric K-spar augen set in a dynamically recrystallized matrix. U-Pb analyses of four fractions plus an air-abraded split of one fraction form a normal linear discordance pattern with an upper intercept of 820 +/- 7 Ma, taken as the age of igneous crystallization. Comparison with other available geochronologic data indicates that this age dates main-phase deformation in the Zambezi belt, and that deformation in the supposedly continuous Damaran belt to the SW was significantly younger.

• Research Organization: Univ. of Zambia, Lusaka
• OSTI ID: 6594769
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
580400 -- Geochemistry-- (-1989)
AFRICA
AGE ESTIMATION
CHEMICAL COMPOSITION
CHEMISTRY
DEFORMATION
DEVELOPING COUNTRIES
GEOCHEMISTRY
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GNEISSES
GRANITES
IGNEOUS ROCKS
METAMORPHIC ROCKS
METAMORPHISM
PETROGENESIS
PLATE TECTONICS
PLUTONIC ROCKS
ROCKS
TECTONICS
ZAMBIA