Title:

Regional controls on sediment-hosted Pb-Zn (Ba-Cu) occurrences within the Pan-African orogenic belts of Namibia

Author(s):
Publication Year:
2000
Abstract:

The three branches of the Pan-African (Damaran) orogenic belt in Namibia host numerous sediment-hosted (massive) sulphide (SHMS) deposits and occurrences. Genetically, these occurrences can be grouped as sedex-type, impregnation (Maubach-Mechernich-Laisvall) type, breccia pipe hosted (Tsumeb type), and possibly MVTs sensu lato in platformal domains. For the first group, regional distribution patterns are closely linked to the original, tectonically controlled basin geometry. The principal regional controls are the basin margins of the initial Damaran rifts and the subsequently widening basins. High-angle, second-order grabens, flanked by basement highs, can be identified along the major basin margins and have acted as funnels for metalliferous brines during sediment compaction and basin dewatering. Transform/transfer faults have provided vertically and laterally extensive pathways for fluid migration. Early Damaran volcanic rocks have provided a local source for Cu and Zn and document an anomalously high heat flow, whereas the sedimentary infill of the basins, and local basement rocks within them, provided the source for Pb, Zn, and Ba. Saline brine provinces give evidence that Cl-rich brines have probably leached, stored, transported and finally precipitated base metals in physical and chemical traps. The positions of the deposit types can be attributed to: i) early rift basin margins; ii) first- and second-order basin margins and high-angle sub-basins during basin subsidence; and iii) platform onlaps onto cratonic regions. It is primarily the pre-collisional basin geometry which has largely determined the distribution and location of the base metal occurrences within the basins, along their margins and on the adjacent platforms.

Publication Title:

Communications of the Geological Survey of Namibia

Publisher:
Geological Survey of Namibia
Volume:
12
Pages:
239-249
Item Type:
Journal Article
Language:
en
Keywords:

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