Structural controls of auriferous quartz veins in the Karibib Area, southern central zone of the Pan-African Damara Belt, Namibia
Date
2008-12
Authors
Kitt, Shawn
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
Detailed geological mapping and a structural analysis of auriferous quartz veins were
undertaken in the Karibib region of the Pan-African Damara belt in central Namibia. The
study focuses on the formation and controls of quartz-vein sets and associated lodegold
mineralization in heterogeneous, siliciclastic- and marble- dominated amphibolitefacies
host rocks around the Navachab gold mine and adjacent areas. Two main arrays
of shallowly-dipping quartz veins can be distinguished that form a conjugate set. Steep,
bedding-parallel and high-angle cross-cutting veins also occur, but play a subordinate
role for mineralization. The orientation of the main conjugate set and progressive
deformation of these quartz veins indicate that veining occurred during the late stages
of the main phase of NW-SE directed, subhorizontal shortening (D2) and associated
NW-verging folding and top-to-the-NW thrusting. Cross-cutting relationships with
plutonic rocks indicate a timing of ca. 540 Ma for the mineralization.
The quartz veins sets show a consistent orientation irrespective of their location with
respect to NE-trending, NW-verging first-order fold structures that were previously
considered to be pertinent for the mineralization. The quartz vein sets also cross-cut
different lithologies at high angles. This suggests that the regional strain (D2) was the
first-order control of quartz vein formation. More localized lithological and/or
structural controls played, however, an important factor for the formation of economicgrade
mineralization. Thick and closely spaced quartz veins in steeply dipping rocks of
the Navachab open pit form a more than 150m thick economic-grade vein swarm. In
this structural situation and during layer-normal subhorizontal shortening, the host
rocks experienced high extensional strains in a vertical direction, favouring the
formation of subhorizontal extension fractures.
Description
Thesis (MSc (Earth Sciences))--Stellenbosch University, 2008.
Keywords
Gold, Quartz vein, Namibia, Navachab gold mine, Quartz -- Namibia, Dissertations -- Earth sciences, Theses -- Earth sciences