4 Works

The Kieshöhe carbonatites in SW-Namibia – the role of silicatic xenoliths for REE exploration

Benjamin Florian Walter , R. Johannes Giebel , Alan Marlow , Michael Marks , Gregor Markl & Jochen Kolb
Exploration of carbonatite-associated REE-deposits is challenging due to heterogeneous ore distribution and variable and often complex ore mineralogy. The Kieshöhe carbonatite in SW Namibia represents a subvolcanic occurrence hosting dolomite, calcite and ankerite carbonatite dykes, ring dykes and diatremes. Petrography, whole rock geochemistry and microXRF imaging provide insights into the role of silicate xenoliths for the REE mineralization in a subvolcanic environment. Xenolith-rich carbonatites are relatively REE-poor with only minor monazite mineralization, whereas xenolith-free carbonatites...

Wall rock contamination and mineralogical modifications in carbonatite dykes of the Palabora Complex, South Africa

R. Johannes Giebel , Benjamin F. Walter , Michael A.W. Marks & Gregor Markl
Contamination of carbonatite melts is often neglected due to a fast magma ascent and low liquidus temperatures. However, increased silicate mineral formation observed in numerous carbonatite occurrences world-wide requires an external Si introduction. Our study demonstrates that carbonatite dykes penetrating different lithologies of Palabora (South Africa) shows different modes of mineralogical modification. In particular Al and Si-rich lithologies show the most significant effects. Besides silicate mineral formation Si introduction may cause directly and indirectly variations...

A global review of carbonatite-hosted fluid inclusions and the role of fluid release on carbonatite magma ascent

Benjamin Florian Walter , Johannes Giebel , Matthew Steele-MacInnis , Michael Marks , Jochen Kolb & Gregor Markl
Carbonatites crystallize from mantle-derived carbonate- and volatile-rich melts that exsolve large amounts of fluids during their ascent through and emplacement into the crust. A global review of available fluid inclusion data for carbonatitic systems from variable emplacement depths identified four types of fluid inclusions: (type-I) vapour-poor H2O-NaCl fluids with <50 wt.% salinity; (type-II) vapour-rich H2O-NaCl-CO2 fluids with <5 wt.% salinity; (type-III) multi-component fluids with high salinity without CO2; and (type-IV) multi-component fluids with high salinity...

The fate of crustal xenoliths in carbonatite dykes of the Gross Brukkaros, Namibia

Rebecca Ruwe , Johannes Giebel & Benjamin F. Walter
The Gross Brukkaros (Namibia) reflects a broad dome structure showing a crater-shaped depression with numerous peripheral beforsitic carbonatite dykes. These dykes frequently contain an extreme load of basement (Nama-group) xenoliths (> 60 vol.%) including shales, quartzites, granites and gneisses. While xenoliths of exposed country rocks (mainly shales) show an angular habit, a pronounced rounding of xenoliths from other lithologies proves a wide transport and strong abrasion. This consumption of xenolithic material may result in remarkable...

Registration Year

  • 2022
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  • Text
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Affiliations

  • University of the Free State
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  • Technical University of Berlin
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  • Karlsruhe Institute of Technology
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  • University of Tübingen
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  • University of Alberta
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