Recent U-Pb high-precision geochronological studies have shown rapid emplacement of the intrusive doleritic component of the Karoo Large Igneous Province (KLIP) in Southern Africa. However, these studies focused on a relatively small geographic and altitudinal region of the KLIP. Additionally, the timing of initiation of extrusive volcanism, preserved in the Drakensberg-Lesotho highlands and its relationship to the intrusive suite, has only been imprecisely constrained by Ar-Ar dates. Here, we present new high-resolution U-Pb zircon ages on dolerite sills and dykes from across the central eastern Karoo Basin (South Africa) at elevations between mean sea level and 1 560 m, as well as U-Pb detrital zircon data that can be used to estimate the maximum age of volcaniclastic deposition near the base of the extrusive component of the KLIP. Dolerite samples were taken across two areas: (1) thick dykes exposed along the coast of the Indian Ocean to-1 600 m flanking the Drakensberg Escarpment in the Eastern Cape; and (2) sills between 20 and 220 m below surface, in a borehole core within the interior of the Karoo Basin, 400 km hinterland from the coastline. Our estimated dolerite emplacement ages span a range of ca. 80 thousand years (Kyr), between 183.122 +/- 0.029/-0.061 and 183.042 +/- 0.042/-0.072 million years ago (Ma), and fall within the 331 +60/-54 Kyr age range previously established for magmatism related to the KLIP, despite the marked increase in sampling coverage in terms of area and altitude in this study. Therefore, KLIP geochronology is consistent with other LIPS such as the Siberian and Deccan Traps that supports the hypothesis of rapid emplacement timescales (<1 Myr). Additionally, these data are consistent with, but better delineate that the KLIP in southern Africa appears to be ca. 500 Kyr older than the main phase of magmatism in the Ferrar LIP of Antarctica. Detrital zircons from the basal volcanic sequence of the Drakensberg Group exhibit age peaks at ca. 1 and 0.5 Ga, typical of the surrounding Namaqua-Natal and Pan-African basement rocks, as well as younger peaks at ca. 260 and 200 Ma that likely relate to source provenances from south-western Gondwana and reworking of the Karoo Supergroup sedimentary rocks. High-precision U-Pb dates of the youngest zircon grains result in a maximum depositional age for the basal pyroclastics of 185.25 +/- 0.25 Ma, allowing for a ca. 2 Myr offset with the intrusive Karoo dolerite suite.

Contact metamorphism along widespread dolerite sills and dykes, emplaced at 182 to 183 Ma through the sedimentary host rocks of the Karoo Basin, triggered devolatilization of carbon-rich shales of the Lower Ecca Group. Hornfel samples collected from drill cores that intersect dolerite sills were analyzed for mineral phase equilibria, chemistry and porosity to characterize thermal aureoles at various distances from sill intrusions. Andalusite-chiastolite and cordierite porphyroblasts with biotite and muscovite occur within 10 to 20 m of many intrusive contacts. These metamorphic minerals crystallized when host shales attained maximum temperatures ranging between 450 and 600 degrees C. Scanning electron microscopy imaging confirms that the hornfels are compact and that their metamorphic minerals limit porosity along grain boundaries. In few cases intra-mineral porosity occurs within individual crystals such as calcite, andalusite and cordierite. Disequilibrium metamorphic textures such as irregular grain boundaries, and inclusions in andalusite and cordierite reveal that the elevated temperatures were too short-lived to accomplish complete (re)crystallization. Thermal modeling results are consistent with the observed metamorphic mineral assemblages. Gas leakage calculations along a 7 m and a 47 m thick dolerite sill that intrude toward the top of the Whitehill Formation suggest that methane volumes ranging between 8 to 15 Tcf were generated during the sill emplacement. Methane was likely released into the atmosphere through hydrothermal vent complexes that are well preserved in the western Karoo Basin. If such loss was widespread across the entire basin, the implications for paleoclimate change and preserved shale gas reserves in the Karoo Basin of South Africa would be significant.

New field mapping has discovered numerous sections of pillow lavas with hyaloclastites at the lowest levels of Jurassic Karoo volcanic sequences across Lesotho and South Africa. Vesicularity (content and size) and geochemistry of the ca. 1 to 50 m thick pillow lavas sequences presently preserved at 1 670 to 2 150 m asl reveal they originated below 500 m of water. Most of the initial 87Sr/86Sr ratios of the pillow lavas scatter around ca. 0.708, which is also the value of Jurassic seawater. There is an increase in the δ18O values concomitantly with increasing alteration, a well-known feature at low-temperature when marine basalts alter to high-δ18O bearing minerals, such as clays and zeolites, stripping 18O by mass balance from seawater. This feature, combined with element behavior of the most altered samples, as well as the Sr-isotope signatures, suggest that the Karoo pillow lavas and hyaloclastites most likely altered under low-temperature conditions in seawater. Geochemistry of the major oxides and trace elements of the Karoo pillow lavas reveal they define tholeiitic basalt with minor basaltic andesite. The pillow lavas define Th/Yb-ratios well above the mantle array indicating derivation from subduction-related components, and their Ti-V relations are similar to mid-oceanic ridge basalt (MORB). The Nd-Sr isotope data for the pillow lavas indicate that the primary magma assimilated ca. 10 to 15% of continental crust. This is consistent with knowledge from mapping that sills and dykes cover close to 50% of the surface geology surrounding the sub-horizontal pillow lava sequences, and from drill-cores that these dolerites reached a minimum crustal depth of ca. 6 km below Jurassic sea level. The Karoo pillow lavas erupted between 186 and 184 Ma in relatively deep seawater of a possible rift system linked to fragmented continental lithosphere surrounded by ocean spreading domains, such as at the open-end of the East African rift across the Afar. By 183 Ma, Karoo volcanics extruded above sea level and after 182 Ma the pillow lavas were uplifted by at least 1 700 m. Thereafter, during farther up warping across the Karoo Large Igneous Province (KLIP), lavas across Lesotho reached heights over 3 500 masl by 140 Ma, and then eroded to their near present heights around 120 to 100 Ma as determined through a number of thermo-chronology and offshore sedimentation analyses. Thus, unlike the volcanics of the Ethiopian LIP, which erupted across continental crust at 2 000 masl ca. 30 to 40 million years prior to extensional tectonism across the Afar triple junction, KLIP reached its highest topography ca. 30 to 40 Myrs after early initiation across a triple junction system well-below sea level. This difference in timing between crustal extension and epeirogeny has implications for geodynamic and geochemical models that trace dispersal across southern Gondwana between Africa and Antarctica.

New tools and algorithms for geological femote Sensing are developed and verified at test sites throughout the world in preparation of the German hyperspectral satellite Mission (EnMAP), which is an Environmental Mapping and Analysis Program.The aggeneys Cu-Pb-Zn deposit, situated in the arid north western part of South Africa, represents a unique field laboratory for testing these new tools. Here spaceborne hyperspectral data covering the Swartberg, and hyperspectral spaceborne data can be demonkrated, such as the Iron Feature Depth index (IFD), which has recently been proposed for mine waste mapping in the North West Province of South Africa and for gossan detection at Haib River in South Namibia.The work presented here explores the potential of the IFD for gossan mapping and characterization at Gamsberg and Big Syncline, from EO-1 ALI and Landsat-8 OLI data together with mineral maps from expert systems such as the United States Geological Survey (USGS) Material Identification and Characterization Algorithm (MICA), and first results from EnMAPs EnGeoMAP algorithm. Field spectroscopic measurements and field sampling were carried out to validate and calibrate the results from the expert systems and the IFD. This ground truthing is a necessary complementary step to link the results from the expert systems and the IFD to in-situ field spectroscopy.Future mineral exploration initiatives may benefit from the techniques described here, because they can significantly narrow the expensive, exploration activities such as hyperspectral airborne data, field activities and drilling, by identifying the most promising mineral anomalies in an area from the spaceborne data.