PAN-AFRICAN STRUCTURES AND METAMORPHISM IN THE MAKUTI GROUP, NORTH-WEST ZIMBABWE

Makuti Group is composed of arkosic gneisses, amphibolites, marbles, c alc-silicate rocks and minor pelitic schists and forms part of the Pan -African supracrustal sequence within the Zambezi belt in northwest Zi mbabwe. The group was affected by two generations of folds (D-Z1 and D -Z2). The D-Z1 folds are isoclinal and plunge gently to the NW and SE. D-Z2 folds are upright and refold D-Z1 folds on an almost coincident axis giving rise to a type III fold interference pattern. Metamorphism within the Makuti Group is syn-D-Z1 and pre-D-Z2. Temperatures calcul ated from garnet-biotite (grt-bt) geothermometers increase to the sout h from 538+/-49 degrees C in upper greenschist/low amphibolite fades, to 595+/-46 degrees C for mid-amphibolite fades and 718+/-30 degrees C for the upper amphibolite grade. Upper amphibolite grt-bt temperature s are supported by amphibole-plagioclase and garnet-hornblende (grt-hb l) temperatures. Compositional zoning is reflected by high anorthite c ontent in plagioclase rims (An(24-30)) relative to the cores (An(10-16 )) and by high X(gro-sps) cores and low X(pyp+alm) cores relative to t he rims in garnets. Temperatures calculated using garnet and plagiocla se rim compositions are 50 degrees C higher than core temperatures. Th us growth zoning in plagioclase and garnet preserve a portion of the p rograde P-T path. The metamorphic and structural data concur with the southward thrusting of the Zambezi belt.