https://commons.ru.ac.za/vital/access/manager/Index ${session.getAttribute("locale")} 5 https://commons.ru.ac.za/vital/access/manager/Repository/vital:20528 = 50 million carats at >= 95% gem quality, for example, the Orange-Vaal dispersal, off the Kaapvaal craton in South Africa. On craton placers are residual, and transient placers are eroded and deposited into the exit drainage, while terminal placers, the final depositories of diamonds with the highest chances of being mega-placers are deposited into terminal basins like oceans and foreland basins. Though data is limited at the moment, the Umkondo conglomerates caratage is likely to run into hundreds of millions of carats, with a diamond gem content of between twenty and twenty-five percent, as is indicated from recent diamond production data. The greater part of the Umkondo diamonds are likely to be lodged beneath the deep gravels of the Middle and Lower Save River basin, because small remnant tilted mountain blocks and inselbergs forming the caps of hills are what remains of the host conglomerate on the western margin of the Umkondo Basin. Areas to be examined in this document will be the geology; the mode of formation of the Umkondo basin and its sedimentary system; the regional kimberlite exploration around the basin; and diamond production in the Marange diamond field, in order to come up with indications of the provenance of the diamonds within the Umkondo conglomerates. The kimberlite clusters in and around the Umkondo sedimentary basin have all proved to be barren or only nominally diamondiferous and that the kimberlites are between 200Ma and 500Ma and thus much younger than the greater than 1.1Ga Umkondo diamondiferous conglomerates. Studies so far undertaken have not managed to point to the origin, or provenance, of the Umkondo or Marange diamonds, which were discovered on the western edge of the Umkondo Basin and in the east of the basin below the Chimanimani Mountains along the Haroni River. This paper is an attempt to clear up some of the misconceptions surrounding the Marange diamond deposit and to raise interest in the urgent rquirement to study and understand the Umkondo Basin and the origin of its diamonds. The only meaningful studies on diamond occurrence and diamond exploration of the basin were undertaken from 1996 to 2006 by Kimberlitic Searches Zimbabwe (Pvt) Ltd, the then Zimbabwe kimberlite exploration arm of De Beers, Zimbabwe, in their quest to find kimberlites, which were thought to be related to the Umkondo alluvial diamond deposit. As will be shown in the following chapters, many of the discovered kimberlites range from very low grade to non-diamondiferous, and are much younger than the Umkondo conglomerates, whose diamonds are in turn a great deal older. Thus the basic question concerning the origin or provenance of the Umkondo placer diamonds still remains unresolved. Because of the sheer size of the basin, modern, wide-area-coverage, geophysical exploration methods become appropriate to effectively generate diamond potential targets for further examination. This document will attempt to collate various data available to paint a true picture of the state of exploration within the Umkondo Basin.]]> Wed 12 May 2021 23:46:29 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:20354 Wed 12 May 2021 23:22:51 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5063 Wed 12 May 2021 23:21:52 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5079 Wed 12 May 2021 20:48:27 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:29250 Wed 12 May 2021 20:18:58 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:20380 Wed 12 May 2021 19:20:53 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:38115 Wed 12 May 2021 17:34:19 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:56820 Thu 29 Sep 2022 12:17:42 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:45201 Thu 23 Jun 2022 10:11:47 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:20762 Thu 13 May 2021 05:36:14 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:21248 Thu 13 May 2021 04:27:28 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4915 2 wt %) crystallise Fe-Ti oxides early whereas low H2O magmas (< 1 wt %) crystallise oxides late. Early pulses of H2O-poor magma crystallise a sequence of plag+cpx+Fe-Ti oxide (±ol). Later pulses of H2Orich magma subsequently intrude the partially crystallised cumulate sequence incorporating and consuming previously crystallised silicates with subsequent early crystallisation of Ti-magnetite and formation of ore layers. H2O-rich magmas likely have suspended Ti-magnetite microphenocrysts as well, which crystallise at depth in the plumbing system. This model can account for the various characteristic features of the Fe-Ti oxide ore layers at the Panzhihua intrusion as well as other Fe-Ti oxide ore bearing intrusions in the region.]]> Thu 13 May 2021 03:57:26 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:65357 Mon 03 Jul 2023 10:33:08 SAST ]]>