|
Daud Jamal, Eduardo Mondlane University (Mozambique)
Amadeu Muchangos, Eduardo Mondlane University (Mozambique)
Daniel Ibraimo, Eduardo Mondlane University (Mozambique)
J. Cossa, Eduardo Mondlane University (Mozambique)
R. Coutinho, Eduardo Mondlane University (Mozambique)
Rune Larsen B., Norwegian University of Science and Technology (Norway)
|
|
The Atchiza Suite is part of Early Pan-African intrusive rocks in northern Tete Province, Mozambique, and covers an area of ∼ 330 km2. (Hunting, 1984; DNG and GTZ, 2006). It is covered to the southeast by Karroo sediments. In the northwestern and northeastern edges it shows tectonic and intrusive contacts with the mafic volcanics Fingoè Supergroup. Massive porphyritic biotite granites, syenites and dolerite dykes intrude the Suite. Locally, the Suite were extensively sheared. The Atchiza Suite is a layered igneous complex, which consist of a lower ultramafic succession, comprising serpentinite/dunite and pyroxenite, covered by an upper sequence, of gabbro, norite and diorite. The layering complexities are indicative of multiple magmatic processes such as injection of different magma compositions, magma mixing, crystal fractionation, etc. (DNG and GTZ, 2006).
Rocks from the Atchiza show a high positive anomaly on the low-density total field aeromagnetic image. In the northern part, an incipient magnetic banding was observed that possibly reflect the magmatic field. Granite-syenite intrusions disturb the magnetic pattern in the south. NE-SW linear anomalies across the Suite are interpreted as tectonic features associated with Pan-African overprint. A Sm-Nd isochron yielded of 864± 30 Ma that is interpreted as the crystallization age of the mafic-ultramafic rocks. (DNG and GTZ, 2006). However, the origin of the Atchiza Suite is yet to be understood. A layered intrusive origin has been attributed to the Atchiza Suite, based on the petrological studies (Hunting 1984) and on the limited geochronological, geochemical, structural data (DNG and GTZ, 2006).
Mineral deposit interest on the Atchiza Suite have been initially associated with mafic and ultramafic rocks which bear some similarities with other layered intrusions (e.g. Stilwater in Canada) . On the other hand, given the setting along the Great Dyke strike it was once interpreted as an extension of the Great Dyke of Zimbabwe (McConnell, 1974), but this was refuted on the basis of recent petrographic studies and geochronology (DNG and GTZ, 2006). The knowledge of mineral potential within the Atchiza Suite is scarce. Cromite seams and Ni-sulphides from serpentinites, and Cu-sulphides and -carbonates and Co-sulphides (DNG and GTZ, 2006) are the few mineralizations recorded on the unpublished internal report at the Geological Survey of Mozambique (DNG). Our ongoing research project aims to unravel the petrogenetic and ore-forming process in the Atchiza Suite with implications for mineral potential
|
