Description

The Brandberg is one of the Cretaceous anorogenic complexes of northwestern Namibia, and from a spacecraft, it is one of the most eye-catching circular features visible on Earth. The isolated massif of granite, with approximate dimensions of 26 by 21 km, rises more than 2000 m above the surrounding peneplain of the Namib Desert. The edges of the roughly cupola-shaped plutonic body are dissected by numerous gorges, which penetrate the central part of the complex to form a radial drainage system. The summit, named Königstein, at 2573 m above sea level is the highest elevation in Namibia. The reddish colour of the weathered granite surfaces led to its German name “burning mountain” as well as its original Damara name “Doreb” meaning a pile of ash. The Brandberg is a National Monument, and the main access is via the road from Uis leading to the “White Lady” rock painting in the Tsisab Gorge.

The dominant plutonic rock type of the Brandberg is a medium grained biotite-hornblende granite showing little textural variation. Fine-grained enclaves near the contact are interpreted as a chilled margin facies. Segregations of a chemically evolved biotite-leucogranite locally form apophyses within the main granite. Numerous leucocratic dykes cut the granite massif and the adjacent country rocks. These dykes range in size from a few centimeters to about 3 m in width. Another plutonic variety is a coarse-grained pyroxene-bearing monzonite which is exposed in the western interior of the massif. Contact relations suggest that the monzonite is older than the biotite-hornblende granite. Quartz-hornblende porphyries occur in the central south-eastern part of the mountain. The youngest intrusive phase is a small arfvedsonite granite sill, which crops out in the Amis Valley at the southwestern edge of Brandberg. This granite carries the amphibole arfvedsonite as the main dark mineral and is highly variable in mode and texture. An indurated hematised variety forms the prominent cliffs in the inner part of the Amis Valley. Related aplitic to pegmatitic dykes intruded the biotite-hornblende granite and the marginal Karoo volcanics in an area up to 1 km distance from the contact zone.

The dominantly medium-grained granite of the main intrusion is reddish on weathered surfaces but appears gray-greenish when fresh. Fine-grained rounded enclaves of similar composition range in size from a few cm to about 50 cm and are common in the marginal facies of the granite. Miarolitic vugs filled with coarse K-feldspar or quartz are occasionally present. In hand specimen, one can observe tabular plagioclase which are often rimmed by whitish K-feldspar. Biotite and hornblende are the most abundant dark minerals. Opaque minerals are titano-magnetite and ilmenite and accessory minerals include apatite, zircon, titanite, monazite and the rare titanite variety cheffkinite. The textures and compositions of the minerals indicate that the Brandberg granite crystallized from a relatively hot and dry magma. Differentiation of the magma produced late-stage leucogranites. These contain biotite as the almost only mafic mineral, although tourmaline is also occasionally present. Macroscopically visible granophyric intergrowth of quartz and orthoclase are common in the leucogranitic dykes, which indicates crystal growth during rapid cooling.

Radiometric dating of the main Brandberg granite has yielded an age of about 130 million years (Schmitt et al., in preparation). This immediately post-dates the peak volcanic activity in the Etendeka flood-basalt province, and the surrounding Goboboseb Mountains, as well as the intrusion of the Messum Complex. Field evidence clearly indicates that the Brandberg post-dates at least the lowermost units of the Etendeka lavas.

A series of dark coloured trachydacitic ring-dykes is present to the north and northeast of the massif in the Gomatserab area. These dykes are sub-parallel to the rim of the intrusion and dip about 30° to 50° towards the center. In the uppermost reaches of the massif, few rafts of dark volcanic hornblende and quartz porphyries are preserved. These and the trachydacite ring-dykes can be related to the early volcanic phase of the Brandberg.

The surrounding country rocks of the Brandberg intrusion consist of Damaran granites and metasediments and overlying Karoo Sequence sediments and volcanics. The sediments comprise siltstones, altered to black hornfels in the contact aureole of the Brandberg, which are overlain by white, quartz-rich coarse conglomerates. They are in turn overlain by basalts capped by quartz latites. Remnants of the Karoo rocks are preserved in a collar along the western and southern margin of the massif and are down-faulted towards the contact. The angle of dip increases as the contact is approached and is near vertical at the contact, where clasts of country rocks occur within the granite forming a magmatic breccia.

A likely scenario for the genesis of the Brandberg is that heating and subsequent partial melting within the crust was triggered by emplacement of mantle-derived basaltic magma. Assimilation of crust-derived partial melts by the cooling and crystallizing basic magmas led to the formation of a hot and anhydrous hybrid granitic magma, which was capable of rising up to near-surface level.

On the way to the parking lot at the eastern edge of Brandberg, the trachydacite dykes can be seen to the N of the road, forming smooth dark hills weathered out of the older Damaran granites. Small roadside outcrops are present near the contact of the Brandberg massif. The trachydacite is a gray porphyritic rock with plagioclase phenocrysts up to 3 cm in length. The mafic mineral assemblage comprises pyroxene and hornblende, set in a fine-grained matrix of intergrown K-feldspar and quartz. Dolerite dyke swarms which cut the Damaran granites are also present close to the road. The dark, highly altered holocrystalline dolerites have a fibrous texture of plagioclase and contain relics of decomposed olivine phenocrysts. Similar dolerite dykes cutting the Brandberg granite have been described from the interior of the massif in the Tsisab Gorge and Bushman Valley (Diehl, 1990).

The interior of the Tsisab Gorge is filled with debris, which carries huge granite boulders up to 3 m in diameter. The higher flanks of the gorge display well exposed surfaces of granite polished by erosion. At the lower flanks, multiple stages of onion-skin weathering typical for granites can be observed.

Along the southern margin of the Brandberg along the road to the defunct Brandberg West Mine, one can find highly altered pyrophyllite bearing Karoo siltstones within the Brandberg metamorphic aureole, which are locally quarried and manufactured into ornaments.

Ecological variety of rare and remarkable plant species that live in isolation at high altitudes; large variety of animal life due to the numerous water sources, rare birds and insects. Harald Pager discovered and recorded more than 1,000 sites with rock art and 43,000 individual pictures, including the famous "White Lady", which is fenced.

Brief History

About 130 million years ago volcanic activity pushed through the earth’s crust causing an up-doming of the overlaying rocks, the eventual breakthrough and resultant collapse caused the formation, following 100 million years over 1000m of the mountain and its surroundings eroded away leaving only the granite core, the brandberg mountain. Remnants of the lava plateau can still be seen. The name describes the lighting effect of the sunrise and sunset on the mountain. The archaeology of the Brandberg has been the subject of serious research for more than eighty years. Detailed surveys of the rock art have recorded more than 1000 sites, some with a hundred or more individual paintings. Although the most famous site, the Maack or “White Lady” Shelter, has given rise to several fanciful interpretations, systematic excavations in other parts of the mountain show that the area was inhabited by hunter-gatherer communities until the first appearance of nomadic livestock farming about 1000 years ago. Small bands of hunters evidently lived in the upper parts of the mountain during the dry season when little water or food could be obtained in the surrounding desert. The structural geology of the mountain, with its well-developed sheet joints, provides many small aquifers and where these emerge, rock painting sites are never far away. In the rock art of Brandberg, human figures comprise more than 40% of the images and among the many animal species depicted giraffe are often the most numerous. Few of the animals featured in the paintings are represented in bones recovered from archaeological excavations. Indeed, very few of the species in the paintings actually occur on the mountain itself which is far too rugged for most of them to ascend. This and other evidence, such as artifacts of crystalline quartz, marine shells and some metal objects, suggests that the people who inhabited the Brandberg also inhabited a far wider area. A clearer pattern of movement arose with the development of pastoralism when stock camps were established at remote waterholes and the herds were pastured far into the Namib Desert after the summer rain. In the dry season, however, pastoral communities would retreat to the upper Brandberg with its reliable waterholes and nutritious pastures, usually camping in the same places as their hunter-gatherer predecessors.