11 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...

Inverse modelling of transport distance to reduce ambiguities of microbial and chemical source tracking in karst catchments

Johannes Zirlewagen, Ferry Schiperski , Tobias Licha & Traugott Scheytt
The identification of contamination sources is vital for water protection, especially in highly vulnerable karst aquifers. Contamination sources might be distinguished by host-specific DNA markers of bacteria (Microbial Source Tracking, MST) or source-specific indicator compounds (Chemical Source Tracking, CST). These methods can help to identify a type of contamination source but fail to distinguish similar contaminant signals from different origins, e.g. multiple points of wastewater infiltration. Transport modelling can reduce these ambiguities by considering the...

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...

Tectonic and environmental perturbations at the Permian-Triassic boundary: insights from the Blue Nile River Basin in central Ethiopia

Maryam Mansouri , Matthias Hinderer , Laura Stutenbecker , Guido Meinhold , Enkurie L. Dawit , Jasper Berndt & Robert Bussert
The Blue Nile River Basin contains a thick fluvio-lacustrine sediment succession of Permian to Jurassic age. Its evolution is linked to extensional tectonics during break-up of Pangea in the aftermath of the Carboniferous-Permian glaciation. We collected sandstone samples from several sections in order to study the tectonic evolution and possible impacts of environmental perturbation around the Permian-Triassic boundary. Based on thin-section petrography, bulk-rock geochemistry, heavy mineral spectra, and detrital zircon U-Pb ages we are able...

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...

Paleoclimate reconstruction using Pleistocene paleosols along the middle Atbara River in Eastern Sudan

M. Mohammednoor, Robert Bussert , S. Tsukamoto , M. Richter , O. El Bedri , B. Kraatz , K. Salih , J. Müller , A. Eisawi & F. Bibi
Along the middle Atbara River, Pleistocene alluvial sediments dated to ~200 to 20 ka are exposed in eastern Sudan over a length of about 200 km with a maximum thickness of 50 m. The Atbara River today has its headwaters in the northern Ethiopian Plateau and is the last major tributary of the Nile before it flows through the Sahara. Previous studies and our fieldwork since 2018 have resulted in extensive finds of fossil terrestrial...

How minerals govern the advance of weathering: comparison of a shallow and a deep weathering profile in different climatic zones (Chilean Coastal Cordillera)

Ferdinand Jakob Hampl , Ferry Schiperski , Nicole Stroncik , Michael Facklam , Friedhelm von Blanckenburg & Thomas Neumann
Weathering is the fundamental precondition for erosion and soil formation which sculpture Earth´s surface. It is a complex interplay of minerals, rock fabric, tectonical fractures, climate, and organic activity. To explore the dependences between these factors two weathering profiles on magmatic bedrock were compared using six-meter-deep soil pits and drill cores in both a humid and a Mediterranean climate regime of Chile. Detailed mineralogical and geochemical investigations of soil and saprolite were combined with spatially...

Comparison of high-resolution SIMS profiles with maximum resolution IRMS stable isotope data

Tobias Kluge , Philipp Holz , Elisabeth Eiche , Thomas Neumann , Alexander Land , Maximilian Schuh , Mario Trieloff & Axel K. Schmitt
High-resolution speleothem paleoclimate records with annual to seasonal resolution are helpful for detailed analysis of climatic changes with limited duration (e.g., volcanic climate impacts), but also for longer-duration events (e.g., at 8.2 ka or 4.2 ka). A high resolution paleoclimate data set is also mandatory for meaningful comparison with archaeological or historical records. Low stalagmite growth rates could impede the acquisition of high-resolution isotope data with the classical micro-milling approach and isotope ratio mass spectrometry...

The Pleistocene sediments of the Palaeoatbara in eastern Sudan as an archive for the evolution of the Nile river system

Robert Bussert , Mosab Mohammednoor , Faysal Bibi , Faysal Bibi , Sumiko Tsukamoto , Omar Bedri , Brian Kraatz , Ignacio Lazagabaster , Johannes Müller , Khalaf Salih & Ali Eisawi
Geological evidence and geodynamic modelling suggest that the Nile river system has been largely stable since its origins ~30 Ma. The Nile could have provided a long-term migration route for vertebrates including hominins between Eastern and Northern Africa. However, other geological data contradict such an old stabilisation of the course of the Nile. Fieldwork along the middle stretches of the Atbara River, the last tributary to the Nile before it crosses the Sahara, provides evidence...

Mutual effects of pH and ionic strength on the mobility of metoprolol in saturated quartz sand

Joshua Sawall & Ferry Schiperski
Emerging micropollutants such as lifestyle drugs, pesticides, and pharmaceuticals are increasingly detected in the aquatic environment. To counter possible threats posed by these pollutants, their transport behaviour needs to be thoroughly understood. In this study, 22 laboratory column transport experiments were conducted at selected pH and Na+ concentrations with natural quartz sand as sorbent to determine transport behaviour of the beta-blocker metoprolol (MTP, pKa=9.67) at various conditions. MTP breakthrough curves were measured at pH 3,...

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
    11

Resource Types

  • Text
    11

Affiliations

  • Technical University of Berlin
    10
  • Karlsruhe Institute of Technology
    5
  • University of the Free State
    4
  • University of Tübingen
    3
  • //ror.org/02jbayz55:Faculty of Minerals and Oil, International University of Africa, Madani St, Khartoum 12223, Sudan
    1
  • //ror.org/05167c961:Department of Anatomy, Western University of Health Sciences, Pomona, CA 91711, USA
    1
  • Keele University
    1
  • University of Hohenheim
    1
  • University of Münster
    1
  • University of Alberta
    1