Abstract:
The Banana Zone Cu-Ag Prospect is within the SW-NE trending Ghanzi-Chobe Belt
(GCB), which extends from the Namibia-Botswana border in the south to Shinamba Hills
in the north near the Botswana-Zambia border. The Banana Zone is also part of the Ghanzi
Project owned by Khoemacau Copper Mining and situated between the Ghanzi and Maun
townships, in Botswana. The Banana Zone has inferred resource of over 225.4 million
metric tonnes (Mt) grading 0.64% Cu and 8.1 g/t Ag. The GCB consists of deformed and
metamorphosed (greenschist) metasedimentary rocks of the Ghanzi Group, that is
commonly subdivided into four formations: the Kuke Formation, Ngwako Pan Formation,
D’Kar Formation, and Mamuno Formation, in ascending stratigraphic order. In this study
only two formations including the Ngwako Pan and the D’Kar Formations were
investigated. The Ngwako Pan Formation is made up of continental siliciclastic sediments,
mainly immature to submature sandstone with siltstone and shale intercalations, while the
D'Kar Formation contains shallow marine to lacustrine grey-green and locally carbonaceous mudrocks (siltstone and mudstone/shale) with fine-grained sandstone and
minor limestone to marlstone. The Cu-Ag mineralisation is hosted at the contact between
hematite-rich Ngwako Pan and reduced organic matter-bearing D'Kar Formations. The
presence of reduced organic matter is likely to have controlled Cu-Ag precipitation by
providing a reducing environment required for the precipitation of sulphides.
Petrographic and geochemical data were combined in order to decipher the petrogenesis of
the Neoproterozoic clastic sedimentary succession of the Ngwako Pan and the D’Kar
Formations associated with the Banana Zone Cu-Ag mineralisation. Sandstone of the
Ngwako Pan and the D’Kar Formations is arkose and subarkose, composed of quartz (Q),feldspars (F), and lithic fragments (L). Moreover, geochemically the sandstone of the
Ngwako Pan and the D’Kar Formations is considered as potassic and classified as arkose.
Therefore, sandstone of both the Ngwako Pan and the D’Kar Formations is chemically and
compositionally immature. On the other hand, mudrocks of the D’Kar Formation are
finely laminated and are dominated by muscovite, sericite, chlorite, and quartz. The
carbonate rocks of the D’Kar Formation are composed of pinkish-white crystalline
limestone and yellowish grey or greyish black marlstone characterised by laminations that are marked by undulating marly and silty layers that give the rock a “zebra-skin”
appearance. The marlstone exhibits variable degree of deformation from shearing to
folding and recrystallisation.
The modified chemical index of weathering (CIW’) values indicated an intense chemical
weathering of the source rock. The dominance of detrital quartz and feldspar grains
coupled with Al2O3/TiO2 ratios (average 29.67 and 24.52 for the sandstone of the Ngwako
Pan and D’Kar Formations, respectively) and Ni and Cr depletion in this sandstone,
suggests a dominant felsic source. However, high concentrations of Ni and Cr and a low
Al2O3/TiO2 ratio (
Tebogo, K (2024). Geology, mineralogy, geochemistry and alteration patterns of Banana zone copper-silver mineralisation , Ghanzi-Chobe belt, northwest-Botswana. Afribary. Retrieved from https://afribary.com/works/geology-mineralogy-geochemistry-and-alteration-patterns-of-banana-zone-copper-silver-mineralisation-ghanzi-chobe-belt-northwest-botswana
Tebogo, Kelepile "Geology, mineralogy, geochemistry and alteration patterns of Banana zone copper-silver mineralisation , Ghanzi-Chobe belt, northwest-Botswana" Afribary. Afribary, 30 Mar. 2024, https://afribary.com/works/geology-mineralogy-geochemistry-and-alteration-patterns-of-banana-zone-copper-silver-mineralisation-ghanzi-chobe-belt-northwest-botswana. Accessed 13 Oct. 2024.
Tebogo, Kelepile . "Geology, mineralogy, geochemistry and alteration patterns of Banana zone copper-silver mineralisation , Ghanzi-Chobe belt, northwest-Botswana". Afribary, Afribary, 30 Mar. 2024. Web. 13 Oct. 2024. < https://afribary.com/works/geology-mineralogy-geochemistry-and-alteration-patterns-of-banana-zone-copper-silver-mineralisation-ghanzi-chobe-belt-northwest-botswana >.
Tebogo, Kelepile . "Geology, mineralogy, geochemistry and alteration patterns of Banana zone copper-silver mineralisation , Ghanzi-Chobe belt, northwest-Botswana" Afribary (2024). Accessed October 13, 2024. https://afribary.com/works/geology-mineralogy-geochemistry-and-alteration-patterns-of-banana-zone-copper-silver-mineralisation-ghanzi-chobe-belt-northwest-botswana