HYPERSPECTRAL REMOTE SENSING AND FIELD SPECTRAL ANALYSIS OF THE STRATIGRAPHY, STRUCTURE, AND METAMORPHISM OF CUPRIFEROUS VOLCANOGENIC MASSIVE SULFIDE OCCURRENCES NEAR GOROB, DAMARA OROGEN, WEST-CENTRAL NAMIBIA

Cupriferous volcanogenic massive sulfide mineralization occurs in at least eight lenses associated with the Matchless amphibolite belt near Gorob, west-central Namibia. The sequence of metatholeiites, banded and stringer ore, magnetite quartzite (ferruginous chert), and enclosing metaturbidites was deposited (~600-750 Ma) in an intracratonic rift and multiply deformed, overturned, and metamorphosed to staurolite+kyanite±sillimanite grade during the ~500-650 Ma Damara Orogeny. Dikes and sills of post-tectonic granite are common in the northern and western parts of the study area, and late faults intersect several of the sulfide lenses with minor offset. Airborne hyperspectral surveys (126 channel, 5-m resolution) accompanied by field and laboratory visible and near-infrared spectroscopic measurements provide valuable information on the mineralogy, stratigraphy, alteration, and structure of the sulfide lenses and host rocks. The remotely-sensed imagery differentiates amphibolite units that correspond to metabasalt and intrusive metagabbro/diorite, and it also highlights subtle variations in the muscovite-biotite ratio in metaturbidites. Near the sulfide lenses the imagery shows thin, concordant zones of iron oxide/hydroxide (goethite) and phyllosilicate (sericite and kaolinite) alteration. The sulfide lenses are separated from the main amphibolite by 100-200 m of metaturbidites; within this interval the imagery shows discordant zones of staurolite-rich schist interpreted to represent syngenetic alteration in the feeder system beneath the exhalative banded sulfides and ferruginous cherts. Post-tectonic leucogranite dikes and sills are marked by high muscovite content and late-stage fault zones are delineated by chlorite and/or goethite. In addition to previously-known copper sulfide occurrences, the remotely-sensed imagery indicates several anomalies with similar spectral characteristics that had not been documented previously.