New, detailed petrographic work on samples taken from drill core at the Sentinel Cu deposit, located on the northeast margin of the Kabompo Dome, northwestern Zambia, suggests a much lower P-T evolution. The Sentinel deposit is hosted in the Katangan Supergroup, which also hosts the extensive occurrences of whiteschists, and consists of kyanite-bearing graphitic phyllite within quartz-feldspar-biotite schist that overlies a sequence of marbles and quartzites. Phyllite occurs as a single ~400m layer where deformation is more intense on its upper and lower margins in comparison to a lower strain core. Within the low-strain domain 0.5-1cm, un-aligned kyanite is directly associated with weakly deformed quartz-chalcopyrite veins that cut bedding and also occur parallel to axial planes of folds. In high-strain domains quartz-sulfide-kyanite veins are dismembered, with kyanite occurring as porphyroclasts in a mylonitic matrix. These textural relationships suggest that veining occurred either prior to, or early in deformation. Moreover, kyanite-vein association and the grain size difference between kyanite and the sub-millimeter phyllite matrix, suggests that kyanite growth is related to aluminum metasomatism during the veining event. Critically, no assemblage evidence exists in the kyanite-bearing phyllites or surrounding quartz-feldspar-biotite schist for high-pressure and/or high-temperature metamorphism as suggested by earlier workers. We suggest a much lower P-T evolution for metasediments of the domes region, and therefore a contrasting tectonometamorphic evolution of the Lufilian Arc relative to the High-P rocks of the Zambezi Belt.
John, T., Schenk, V., Mezger, K., Tembo, F., 2004. Journal of Geology, 112, 71-90.
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