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Langer Heinrich |
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Namibia |
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U
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Super Porphyry Cu and Au
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The Langer Heinrich calcrete hosted uranium deposit is located in the Gawib River valley, between the Langer Heinrich mountain and the Schieferberge, around 85 km ENE of Walvis Bay in Namibia (#Location: 22° 48' 40"S, 15° 19' 41'E).
The basement is composed of metaquartzite and schists of the Neoproterozoic Nosib and Swakop Groups which are intruded by the late-syntectonic to post-tectonic Bloedkoppie Granite and numerous pegmatites. The Bloedkoppie Granite is a medium- to locally coarse-grained leucogranite with quartz, microcline, plagioclase and biotite as the main constituents and is interpretted to be the main source of Uranium with an average of 18 ppm U and a Th:U ratio of 0.9 to 2.6.
The Gawib valley is filled by the Miocene Langer Heinrich and Recent to Pliocene Bloedkoppie Formations now exposed in erosional channels and represent the palaeo-channel of the ancient Gawib River. The channel is variably developed and preserved with up to 45 m of sediments. Uranium mineralisation as carnotite, is associated with calcrete developed predominantly within the Langer Heinrich Formation and to a lesser degree within the younger Bloedkoppie Formation.
The deposit is developed over a 15 km interval in the main channel in seven higher grade pods which are enveloped by lower grade material. The carnotite occurs as thin films lining cavities and and fracture planes and as grain coatings and as disseminations in the calcrete. Mineralisation is largely near surface, is 1 to 30 m thick and developed over widths of 50 to 1100 m (depending on the width of the palaeochannel).
The distribution of the mineralisation is only partially controlled by permeability barriers or constrictions, but is mainly the result of the direct precipitation of carnotite based on solubility. Uranium appears to be largely concentrated in the central core of the channel and not necessarily related to the present day water table. Following calcrete development (formed by the near surface precipitation of limestone under arid to semi-arid climatic conditions) and subsequent carnotite deposition, parts of the host sediments were uplifted and eroded. The present day Gawib River has dissected and modified both the calcrete and carnotite mineralisation, while the subsequent ephemeral drainage has blanketed the deposit with up to 8 m of alluvial sands and scree.
At a 250 ppm U3O8 cutoff, the total mineral reource (2006) is calculated as 72.3 Mt @ 0.06 to 0.07% U3O8 comprising 44 000 tonnes of U3O8. Of this, 46% is Measured and Indicated Resource and 54% is Inferred Resource under the JORC code.
The title to the deposit is owned by Paladin Resources Ltd through Langer Heinrich Uranium Pty Ltd.
The most recent source geological information used to prepare this decription was dated: 2006.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Langer Heinrich
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Selected References:
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Hambleton-Jones B B, Levin M and Wagener G F, 1986 - Uraniferous surficial deposits in southern Africa: in Anhaeusser C R, Maske S, (Eds.), 1986 Mineral Deposits of South Africa Geol. Soc. South Africa, Johannesburg v2 pp 2269-2287
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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