PAN-AFRICAN GRANULITE-FACIES METAMORPHISM IN THE MOZAMBIQUE BELT OF TANZANIA - U-PB ZIRCON GEOCHRONOLOGY

Two new U-Pb concordia zircon ages are reported for granulite-facies rocks from the Mozambique Orogenic Belt in eastern Tanzania. These rocks are thought to have been generated during collision-related crustal thickening process and exhumed by deep erosion. A two-pyroxene granulite sample from the Pare Mountains has yielded a concordia upper intercept age of 645 +/- 10 Ma, whereas a granulite-facies meta-anorthosite sample from the Uluguru Mountains has given an upper intercept age of 695 +/- 4 Ma. Evidence for the involvement of older crustal material (pre-Late Proterozoic) was not found. These zircon data indicate crystallization during the peak of granulite-facies metamorphism during the Pan-African orogeny (c. 950 to c. 550 Ma) consistent with a subduction-collisional environment.