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    Kaolinization – a tool to unravel the formation and unroofing of the Pleystein pegmatite-aplite system (SE Germany)

    Dill, H.G. and Dohrmann, R. and Kaufhold, S. and Balaban, Sorin-Ionut (2015) Kaolinization – a tool to unravel the formation and unroofing of the Pleystein pegmatite-aplite system (SE Germany). Ore Geology Reviews 69 , pp. 33-56. ISSN 0169-1368.

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    Abstract

    The Hagendorf-Pleystein Pegmatite Province, SE Germany, is known for the largest feldspar-quartz pegmatite in Central Europe and renowned for its rare elements, e.g., Li, Nb, Ta, giving rise to a spate of exotic minerals, mainly phosphates. Argillaceous rocks are scarce and eclipsed by the numerous mineralogical investigations on rare phosphates. These phosphate pegmatites are for the first time subjected to a clay mineralogical study, rendered possible by the newly discovered strongly kaolinized aplite near the Kreuzberg Quartz Pegmatite at Pleystein. The supergene kaolin akin to the residual kaolin deposit at Tirschenreuth, SE Germany, was analyzed for its major and minor elements by XRF and micro-chemically by EMPA. Mineralogical investigations involved XRD, IR spectroscopy, thermo analytical studies, CEC analyses and SEM-EDX. Supergene kaolinization forms a repository for heavy minerals critical for the interpretation of the emplacement of the Late Paleozoic pegmatites as well as a matrix for pegmatite-related trace elements and thereby may be used as an ore guide during exploration of these rare metal pegmatites. The resultant kaolin is also the protagonist in the story of exhumation and destruction of a pegmatite by weathering and erosion. Irrespective of the strength of kaolinization, Nb-Ta-Ti heavy minerals can be identified in the regolith atop the host pegmatite or aplite and used for genetic interpretation of the primary mineralization and the origin of the felsic intrusive. Nb-Ta solid solution series (s.s.s.) have to be treated cautiously because of the disposition of Ta-enriched Nb-Ta oxide s.s.s. to undergo corrosion in their tantalite lamellae more easily than in their niobium-enriched zones. Kaolinization may alter the primary Nb/Ta ratio but no to the extent that Ta is released completely. The most strongly kaolinized new aplite is the youngest member of a series of felsic intrusive rocks in the Pleystein pegmatite-aplite system. The supergene kaolinization extending from the Miocene through the Pliocene can easily be correlated by “minero-stratigraphy” with the larger Tirschenreuth kaolin deposit. The four stages established in the area furnish evidence of gradual alkalinisation of the meteoric pore fluids throughout the Neogene and the Quaternary. Youngest stages are found at Tirschenreuth, the oldest regolith stage is present at Pleystein.

    Metadata

    Item Type: Article
    Keyword(s) / Subject(s): Kaolin, regolith, pegmatite-aplite, ore guide, SE Germany
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Depositing User: Administrator
    Date Deposited: 28 Jan 2015 13:25
    Last Modified: 11 Mar 2015 13:36
    URI: http://eprints.bbk.ac.uk/id/eprint/11533

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