The NW trending Archean Tati Greenstone Belt is located in the southwestern part of the Zimbabwe Craton, in northeastern Botswana and consists of mafic to felsic volcanic rocks and metasediments. All rocks in the TGB have undergone greenschist facies metamorphism at 2630 ± 70 – 2570 ± 70 Ma and intrusion of granitoids that comprises of granodiorite, tonalites, quartz diorite and monzonite occurred at 2.65- 2.73 Ga. The TGB is host to numerous Au deposits including from NW to SE: Map Nora, Golden Eagle, Mupane and Signal Hill. In order to unravel the genetic relationships between the different Au mineralization areas and to track the sources of gold, Ar/Ar geochronology, U/Pb geochronology, Pb/Pb geochronology and Pb isotope analyses were carried out. The Pb/Pb dating of sulfides from the Mupane Au deposit yielded a Pb/Pb errorchron age of 2873 ± 140 Ma, pointing to a pre-metamorphic mineralization event, whereas Shashe sulfides (Map Nora and Golden Eagle), all sulfides and all arsenopyrite from both Mupane and Shashe deposits yielded overlapping and post-metamorphic Pb/Pb errorchron dates of 2250 ± 110 Ma, 2226 ± 66 Ma and 2220 ± 73 Ma, respectively. The U/Pb dating of hydrothermal almandine garnet that is spatially associated with the Mupane Au mineralization yielded overlapping concordia ages and a Tera-wasserburg lower intercept 206Pb/238U age of 2105 ± 24 Ma and 2119 ± 18 Ma, respectively. The ages also correspond to a post-metamorphic type of Au mineralization. Furthermore, phengite spatially associated with the Signal Hill Au mineralization yielded an Ar/Ar plateau age of 1987 ± 24 Ma and a weighted mean Ar/Ar ages of 1976 ± 31 Ma and 1987 ± 13 Ma, also suggesting a post-metamorphic (2630 ± 70 - 2570 ± 70 Ma) mineralization event. The 2873 ± 140 Ma Pb/Pb age of Mupane Au mineralization coincides within error with the age of BIF deposition (2.73 ± 0.15 Ga), intrusion of granitoids (2.65 - 2.73 Ga) in the TGB and also correlates within error with the ca 2.7 Ga first Limpopo-Orogeny (Limpopo-Liberian tectogenetic cycle). The phengite Ar/Ar ages coincide within error with the 1.95 - 2.05 Ga second Limpopo-Liberian tectogenetic cycle, which is here considered to have possibly triggered the Au mineralization in the Signal Hill Au deposit. The garnet ages do not correspond to any geotectonic event known both locally and regionally. The results clearly indicate that the Au mineralization across the TGB is of various ages and corresponds to at least three temporally distinct gold mineralization events, with two of them triggered by regional geotectonic events.iii Lead isotope compositions of both sulfides and whole rocks are heterogeneous. Sulfides show, 206Pb/204Pb ratios of 14.274 - 29.711, 207Pb/204Pb of 14.957 - 17.179 and 208Pb/204Pb ratios ranging from 33.962 - 65.243, whereas the whole rocks have 206Pb/204Pb ratiosrange from 13.491 - 17.739, 207Pb/204Pb from 14.550 - 15.538 and 208Pb/204Pb from 33.744 - 38.261. Lead isotope compositions of both whole rocks and sulfides from Golden Eagle, Mupane and Signal Hill Au deposits overlap and the possible sources of Pb are granodiorite from Signal Hill, schist from Mupane and Map Nora Au deposits. At Map Nora however, arsenopyrite has a wide range of Pb isotopic compositions, 206Pb/204Pb range from 29.011 - 29.711, 207Pb/204Pb from 17.118 - 17.179 and the 208Pb/204Pb range from 59.921 - 65.243, suggesting that the Au source rock is likely the black shale because is the more radiogenic lithology that is known to occur in the Map Nora area.

Thesis (MSc Geology)--Botswana International University of Science and Technology, 2020