Title:

Host-rock geology of the metamorphosed massive sulfide deposits at Gorob in the Pan-African Damara Orogen, Namibia

Author(s):
Publication Year:
1990
Abstract:

Massive sulfide deposits in the Gorob-Hope area, Namibia are hosted by pelitic and psammitic schists of the Kuiseb Formation and are associated with amphibolites of the Matchless Member. The metasediments at Gorob are interpreted as turbidites metamorphosed at staurolite-kyanite/sillimanite grade. Only one prograde event of regional metamorphism can be recognized and the conditions are estimated to about 600°C at 6 kb. Four phases of ductile deformation produced two early generations of isoclinal folds (F1 and F2), ductile shear zones (D2 and D3) and later large open folds (F4). The four major sulfide lenses and a number of smaller occurrences are arranged around the limbs of a large F4 synform, the Hope Synform. Despite the complex structural situation and the strong overprint by regional metamorphism, the original shape of the ore-bodies and their alteration zones can be reconstructed. The deposits can be classified as submarine volcanogenetic-exhalative, similar to Besshi-type deposits. The zonation of the ore-bodies with magnetite-quartzites in the structural footwall, massive pyrrhotite-chalcopyrite-pyrite lenses and chalcopyrite stringer-mineralization within the alteration zones in the structural hanging wall indicates that the deposits are overturned. The rocks of the alteration zones exhibit mineral assemblages which are exceptional in this area. This can be attributed to the presumed pre-metamorphic mobility of Si, Fe, Mg, K, Na and Ca during the metallogenetic processes. A generally increased number of mineral phases has also been recorded in these rocks.

Publication Title:

Journal of African Earth Sciences (and the Middle East)

Volume:
10
Issue:
4
Pages:
717-732
Item Type:
Journal Article
Language:
en