SHRIMP U-Pb zircon ages of granitoids from the Western Domain of the Kaapvaal Craton, Southeastern Botswana: implications for crustal evolution

Abstract

SHRIMP U-Pb zircon dating of granitoids from borehole cores from the Amalia-Kraaipan granite-greenstone terrain of southeast Botswana yielded dates of: 2939±9 Ma for the biotite granite gneiss, 2943±9 Ma for the pink granite and 2782±6 Ma for the red granite. These dates define two main granite magmatic events in the Western Domain of the Kaapvaal Craton at ~2.96 to ~2.94 Ga and ~2.78 Ga. In the Kaapvaal Shield the main magmatic events are dated at ~3.5 to ~3.3, ~3.2 to ~3.1, ~2.96 to ~2.94 and ~2.78 Ga. The two domains were therefore affected by coeval igneous events at ~2.96 to ~2.94 Ga and ~2.78 Ga and therefore the age of ~2.96 to ~2.94 Ga is taken to date their amalgamation along the Colesberg lineament. The ages of ~2.78 Ga correspond to the emplacement of the Gaborone Igneous Complex of southeast Botswana, which is possibly related to the reactivation of or renewed igneous activity along the Colesberg lineament.

Geophysical and Hydrogeological Groundwater Prospectivity Mapping in the Kraaipan Granite-Greenstone Terrain, Southeast Botswana

“…The Kraaipan granite-greenstone terrain constitutes the western central part of [19]. The greenstones consist of three narrow NNW-striking belts (Stella, Kraaipan, Madibe; Figure 1) dominated by mafic metavolcanic rocks interlayered with ferruginous and siliceous metasedimentary rocks, mainly BIF and ferruginous chert [19] [21].…”

“…The greenstones consist of three narrow NNW-striking belts (Stella, Kraaipan, Madibe; Figure 1) dominated by mafic metavolcanic rocks interlayered with ferruginous and siliceous metasedimentary rocks, mainly BIF and ferruginous chert [19] [21]. The surrounding granitoid rocks include tonalitic and trondhjemitic gneisses (TTG), granodiorites and adamellites [17].…”

“…The surrounding granitoid rocks include tonalitic and trondhjemitic gneisses (TTG), granodiorites and adamellites [17]. The terrain is intruded by the Neoarchaean Gaborone Igneous Complex that includes A-type granitoids, anorthosites, rhyolites and subsidiary mafic rocks, represented by the Mmathethe granite [19] [22]. The generalized lithostratigraphy in the area is summarised in Table 1.…”

“…Narrow and higher amplitude magnetic anomalies in western and the central parts coincided with gravity highs, particularly at Phitshane-Molopo and Mabule, suggest the existence of mafic volcanic rocks. Field investigation reveals that the rocks in these areas are made up mainly of banded iron formations (BIF), magnetite quartzites and metavolcanic rocks [19]. The borehole yields ( Figure 3) were also gridded using a minimum curvature technique resulting in a relatively smooth grid ( Figure 11) for correlation with the gravity and magnetic zones and structures.…”

Geophysical Modelling of the Molopo Farms Complex in Southern Botswana; Implications for Its Emplacement Within the 2 Ga Large Igneous Provinces of Southern and Central Africa

“…Almost 3000 million years of sedimentation, igneous activity, metamorphism and deformation are recorded in the rocks that now underlie the Kalahari beds of southern Botswana (Table 1; Crockett and Jones, 1975;Gould et al, 1987;Carney et al, 1994;Key et al, 1996;Key and Ayres, 2000;Mapeo et al, 2004). Three major periods of postArchaean folding have eastwest axes which suggest re-activation of older crustal structures throughout the recorded post-Archaean geological record (Silver et al, 2004).…”