The Kunene anorthosite complex, Namibia, and its satellite intrusions : geochemistry, geochronology, and economic potential

The Kunene Complex of Namibia-Angola is one of the largest anorthosite massifs on Earth (up to 18,000 km (super 2) ), consisting of several distinct anorthosite and leucotroctolite intrusions. The Namibian portion of the Kunene Complex measures approximately 80 x 50 km, approximately 4,000 km (super 2) , and is dominated by the Zebra Mountain lobe, a approximately 16-km-thick dome-like mass of interlayered, relatively unaltered dark leucotroctolite with relatively altered, "white," anorthosite. Past studies and the present work have found evidence for intrusion of two distinct phases of dark leucotroctolite into the white anorthosite, namely a relatively early, deformed, phase dated at 1363 + or - 17 Ma (U-Pb in baddelyite), and a relatively later and undeformed phase whose absolute age remains unknown. The Kunene leucotroctolites are among the least evolved troctolites known from anorthosite complexes, with olivine containing 59 to 77 mol % forsterite and up to 1,700 ppm Ni, and plagioclase containing 56 to 69 mol % anorthosite. Our isotope data from the troctolites indicate a relatively small crustal component (delta (super 18) O, approximately 5.3-7.3; delta (super 34) S, 0.5-1; and epsilon Nd (sub T) , 0.9-1.8), whereas Nd and oxygen isotope data from the white anorthosites, published by other workers, showed a slightly larger crustal component (e.g., epsilon Nd (sub T) as low as -3; delta (super 18) O up to 7.5 per mil). In the periphery of the Kunene Complex are several, relatively small (