FIELD RELATIONSHIPS AND AGE OF SUPRACRUSTAL BELT BRIDGE COMPLEX AND ASSOCIATED GRANITOID GNEISSES IN THE CENTRAL ZONE OF THE LIMPOPO BELT, SOUTH-AFRICA

Field relationships in the Sand River in the Central Zone of the Limpo po Belt show that the supracrustal rocks of the Belt Bridge Complex ar e intruded by granitoid phases of the Sand River Gneiss protoliths. Th is observation is confirmed by SHRIMP U-Pb zircon ages and a whole-roc k Nd mean crustal residence age: a sample of Belt Bridge metapelite co ntains detrital zircons with zircon ages ranging from 3358 to 3709 Ga. Two grains have metamorphic overgrowths with a mean age of 2023 +/- 1 2 Ma, identical to a zircon age of 2027 +/- 4 Ma previously establishe d for a peak of regional metamorphism in the Messina area of the Centr al Zone. The mean crustal residence age for this metapelite sample is 3580 Ma. Two samples of leucocratic and well-layered granitoid gneiss, termed Dorothy gneiss, contain concordant zircons with mean Pb-207/Pb -206 ages of 3239 +/- 2 and 3240 +/- 7 Ma, respectively. The former wa s collected in the Sand River on Verbaard farm where it cuts the folia tion of the interlayered metapelites, and the latter occurs further do wnstream in the Sand River at the Causeway locality. These leucogneiss es represent some of the oldest magmatic phases in the Central Zone of the Limpopo Belt dated so far.