https://ujcontent.uj.ac.za/vital/access/manager/Index ${session.getAttribute("locale")} 5 Basin analysis of the Mesoproterozoic Bushmanland group of the Namaqua Metamorphic Province, South Africa https://ujcontent.uj.ac.za/vital/access/manager/Repository/uj:2666 250°C), metalliferous hydrothermal fluids infiltrated and altered these hydrogenous Fe-Mnrich metasedimentary rocks, resulting in the deposition of base-metal sulfides, formation of magnetite-amphibolite-rich Fe-Mn-rich rocks, as well as hydrothermal alteration of the siliciclastic wall rocks to form coticules. The spatial restriction of epigenetic Fe-Mn-rich rocks to shear zones, high Fe2O3 T (ca. 65 wt %), low ΣREE (ca. 13 ppm), presence of recrystallized quartz crystals, elevated concentration of Cu in some occurrences and general similarities with some hydrothermal iron/iron-oxide copper-gold (IOCG) deposits, suggests that the epigenetic Fe-Mn-rich rocks may have formed during prograde metamorphism. Low concentrations of SrO (0.5 ± 0.2 wt %), highly radiogenic Sr/ Sr ratios (0.7164 ± 0.0028), elevated δ S (27.3 ± 4.9 ‰) and δ O (7.7 ± 3.1 ‰) values in the barites, as compared to contemporaneous Mesoproterozoic seawater, suggests precipitation of stratiform and stratabound barite layers in the Bushmanland Group occurred through mixing of an evolved continental crustal source and contemporaneous seawater sulfate, 87 86 34 18 modified by bacterial sulfate reduction. Most importantly, δ O values suggest possible minimum temperatures of formation ranging from 18 <150°C for the Gamsberg deposit to >250°C for occurrences in the Aggeneys area. These obvious differences in temperature of formation are in good agreement with the Cu-rich, Ba-poor nature of the sulfide mineralization characteristic of the Aggeneys deposits versus the Cu-poor, Ba-rich character of the Gamsberg deposit. In conjunction with this, the isotopic and petrographic arguments favor a sub-seafloor replacement model for the stratabound barite occurrences of the Aggeneys deposits, while at Gamsberg, deposition at the sediment-water interface as a true sedimentary exhalite appears more acceptable. Data obtained in the present study, combined with the results of previous investigations can be used to develop a comprehensive model for the geological evolution of the Aggeneys Terrain and Namaqua Metamorphic Province. The tectono-sedimentary evolution of the Aggeneys Terrain and Namaqua Metamorphic Province is marked by two important tectonic events separated by an episode of tectonic quiescence. Extrusion and deposition of the metavolcano-sedimentary rocks of the Orange River Group at 1908 Ma marks the start of the Orange River Orogeny. vii Prior to emplacement of the Vioolsdrift Intrusive Suite, the Orange River Group appears to have undergone a period of folding and low-grade metamorphism [D1/M1] that was subsequently followed by emplacement of the Main Phase Vioolsdrift Intrusive Suite roughly dated at 1890 Ma. Rapidly following emplacement of these intrusions, the lower crustal rocks of the Richtersveld Subprovince underwent a second, higher, amphibolite-facies metamorphic event [M1B] from 1870-1840 Ma. This event may have resulted in lower crustal melting and emplacement of the Gladkop Suite into an unknown package of metasediments or metasedimentary rocks south of the present day Orange River at roughly 1820 Ma. The Gladkop Suite was subsequently subjected to high-grade metamorphism at 1800 Ma. The Orange River Orogeny was terminated by emplacement of the Late Phase Vioolsdrift Intrusive Suite at approximately 1765 Ma and later northward-directed thrusting. Following termination of the Orange River Orogeny, deposition of the Bushmanland Group began in a tectonically stable environment marked by punctuated periods of tectonic activity that lasted until emplacement of the Little Namaqualand Suite at 1190 Ma. The detrital zircon populations of the Pella Quartzite Fm. and Koeris Fm. support (a) regional correlation of these stratigraphic units throughout the study area, (b) confirms sediment derivation from various local source terrains and (c) suggests a maximum depositional age of 1650 Ma. Furthermore, new age constraints reveal initiation of the O’okiepian Episode (Namaquan Orogeny), characterized by regional-scale mid- to high-grade contact metamorphism, was synchronous with emplacement of the Little Namaqualand Suite and deposition of the upper Kouboom Subgroup. Furthermore, the detrital zircon populations for the Driekop Fm. (upper Kouboom Subgroup) contain a large population of 1190 Ma (i.e. O’okiepian-age) detrital cores, suggesting a renewed period of tectonic uplift. Analogously, age constraints for the Koeris Fm. indicate a maximum depositional age of 1130 Ma, as well as derivation from a number of local and exotic source terrains indicating that deposition of the Koeris Fm. must have occurred in response to continental collision between the Rehoboth Inlier-Kaapvaal Craton and the Namaqua Metamorphic Province. Furthermore, these new age constraints also constrain the timing of D2-D3 deformation to between 1130-1080 Ma and regional peak metamorphism to 1020- 1040 Ma.]]> Sat 16 Sep 2017 02:23:49 SAST ]]> The origin of the Kheis Terrane and its relationship with the Archean Kaapvaal Craton and the Grenvillian Namaqua province in Southern Africa https://ujcontent.uj.ac.za/vital/access/manager/Repository/uj:14852 Sat 16 Sep 2017 01:10:05 SAST ]]> Medicinal ethnobotany of the Kamiesberg, Namaqualand, Northern Cape Province, South Africa https://ujcontent.uj.ac.za/vital/access/manager/Repository/uj:2843 Mon 31 Aug 2020 12:22:52 SAST ]]>