Geology

The Mumbwa licence area falls within a larger tectonic province referred to as the Lufilian Arc or Lufilian Belt.

The Lufilian Arc is described as a large arcuate structure covering eastern Angola, the southern Democratic Republic of Congo (DRC) and northwestern Zambia. This Neoproterozoic-Lower Palaeozoic arc forms a segment of a system of Pan-African orogenic belts traversing central and southern Africa. The Mwembeshi Shear Zone (MSZ), a prominent, crustal scale east-northeast trending shear zone extends across Central Zambia, and separates the Lufilian Arc from the Zambezi Belt in the south. To the west it is flanked by the mesoproterozoic (1.4 - 1.0 Ga) Kibaran Belt and to the southeast by the Mesoproterozoic Irumide Belt.

There are three major deformation phases for the Lufilian Arc. The first phase (D1) represents a major fold and thrust deformation throughout the Lufilian Arc. These folds have a northwest/southeast trend and are predominately northeastward verging in the eastern part of the Lufilian Arc, trend northeast/southwest with a northwestward vergence in the western part and trend east-west in the central and northernmost part.

The second deformation phase (D2) is related to eastnortheast/west-southwest strike-slip faulting with the Mwembeshi Dislocation Zone representing the southern boundary of the Lufilian arc. Several other dislocation zones with similar trends are related to this deformation event. A third deformation phase (D3) is described as late transverse folding, which is characterised by large, open, upright folds trending north-northeast/south-southwest to east-northeast/westsouthwest and north/south and east/west trending faults.

Most of the work on the Lufilian Arc has been concentrated on the northern areas of the arc around the Copper Belt region. The question therefore does exist as to how applicable these structural and stratigraphic interpretations are to the southern part of the Lufilian Arc where the Mumbwa Licence Area is situated.

local geology

The central and northern parts of the project area are underlain by sedimentary rocks of the upper units of the Neoproterozoic Katanga Supergroup. These are comprised essentially of carbonates and calc-arenites interlayered with shales and siltstones (Billiton, 1999). The western and southwestern part of the licence area is dominated by intrusive granitoids of the Hook Massif (Billiton, 1999). Both the sediments and the Hook granitoids are intruded by late to post-tectonic, A-type syenites, quartz syenites, quartz-feldspar-porphyries, granites, granodiorites, diorites and gabbros (Billiton, 1999).

Falcon^TM Survey

Falcon^TM is a proprietary airbonrne system that can identify significant anomalies rapidly and cost effectively over a large area. Blackthorn has been able to draw on the expertise of BHP Billiton and their proprietary SolidEarth^TM software to undertake direct 3D inversion of this Falcon^TM gravity gradient, magnetic and radiometric data. 

SOLIDEARTH^TM

The result is improved 3D inversion models, which are then analysed using SolidEarth^TM neural network techniques to highlight zones of anomalism. The data was inverted on a 100m lateral and 25m vertical resolution, with models extending to approximately 2km below surface. With this approach, dense bodies that lie adjacent to or even proximal to magnetic zones are also considered valid IOCG targets.