14 Works

Sediment production in the Coastal Cordillera of Chile from detrital apatite geochemistry and thermochronology

Andrea Madella , Christoph Glotzbach & Todd A. Ehlers
We study spatial patterns of sediment production in two catchments of the Coastal Cordillera (Chile) situated in semi-arid and mediterranean bioclimates. To do so, we measure bedrock and detrital apatite trace elements as well as apatite cooling ages with the U/Pb, fission track, U-Th(-Sm)/He thermochronometric systems. The compositional and geochronologic data measured in bedrock are run through a Principal Component Analysis and a Support Vector Machine clustering algorithm to find the parameters that are best...

Exhumation pulses in the Southern Patagonian Andes (Torres del Paine, 51°S)

Nevena Andrić-Tomasevic, Sarah Falkowski, Alireza Aghakhani & Todd A. Ehlers
University of Tuebingen, Germany

The Cenozoic exhumational evolution of the Southern Patagonian Andes and its potential tectonic and climatic controls remain poorly constrained. Here, we integrate 21 new and 73 published bedrock thermochronological ages with 3D thermo-kinematic modelling (Pecube) to quantify exhumation pulses in the Torres del Paine area. This approach is used to identify temporal and spatial variations in exhumation rates before and after the start of Late Miocene glaciation. Our new...

Molybdenum isotope evidence for forearc mantle recycling at the Tongan subduction zone

Qasid Ahmad , Martin Wille , Stephan König , Carolina Rosca , Angela Hensel , Thomas Pettke & Jörg Hermann
Molybdenum isotope ratios (δ98/95Mo) of marine sediments constitute an important tracer for paleoredox reconstructions of the ancient ocean. Due to its redox-sensitivity, significant mass-dependent Mo isotope fractionation is induced in present-day low temperature environments leading to distinct Mo concentrations and isotope compositions in different marine lithologies. Subduction and recycling of such fractionated material can thus be potentially traced in arc magmas. Indeed, Mo isotope variations are observed in mafic arc lavas that are attributed to...

Granulometric and lithologic control on apatite and zircon concentrations in Alpine fluvial sediment

Daniela Krieg, Laura Stutenbecker , Ariane Djahansouzi & Christoph Glotzbach
Detrital heavy mineral compositions are controlled by many factors such as mineral fertility in the source rocks and hydraulic sorting. Quantifying and understanding the resulting bias is crucial especially for the correct interpretation of single-grain analyses such as apatite or zircon geochronology in provenance studies. In this study, an inter- and intrasample comparison of apatite and zircon concentrations is conducted on modern Alpine fluvial sands from five mono-lithological catchments draining granitoid, ophiolitic, metamorphic and sedimentary...

Nephelinites from the Gregory Rift

Michael Marks, Michelle Siegel , Mika Henzler , Thomas Binder , Simon Braunger, Thomas Wenzel , Anatoly Zaitsev , Andrei Arzamastsev & Gregor Markl
Nephelinites are strongly SiO2-undersaturated volcanic rocks that are often associated with phonolites and carbonatites. In the Gregory Rift in East Africa several major nephelinitic-phonolitic volcanoes occur, with some of them being associated with carbonatitic rocks (e.g., Oldoinyo Lengai, Kerimas, Mosonik, Shombole, Meru), while others lack carbonatites (e.g, Sadiman, Essimingor, Burko). We characterize the magmatic evolution of the Burko volcano and compare our results with published data from spatially associated nephelinite-phonolite±carbonatite associations in the Gregory Rift...

Structural modelling of Agbada (Tertiary) sandstone reservoirs in “Atled Creek”, Onshore Niger Delta, Nigeria

Olajide Jonathan Adamolekun , Benjamin Busch , Idongesit Akwaowoh , Michael P. Suess & Christoph Hilgers
The distribution of rocks and rock properties is an important part of an overall strategy for reservoir development, placement of new wells and prediction of future production. It also provides a detailed look into the local development of a sedimentary basin. Here we present a case-study from the “Atled Creek” concession, onshore Nigeria. A 3D structural reservoir model of the concession was prepared from available industry seismic data and well logs. Four sandstone reservoirs within...

Exhumation and erosion rates in the flat-topped Nock Mountains in the Eastern Alps constrained by low-temperature and cosmogenic 10Be data

Andreas Wölfler , Andrea Hampel , Christoph Glotzbach & István Dunkl
Constraining rates of landscape evolution is a necessary pre-requisite for reconstructing the spatiotemporal evolution of the Earth´s surface. In our study, we present new zircon and apatite fission track and (U-Th)/He ages as well as catchment-wide 10Be-derived erosion rates to determine exhumation and erosion rates in the Nock Mountains, an elevated-low relief landscape in the Eastern Alps. Zircon fission track and zircon (U-Th)/He analyses yielded cooling ages of ~90 and ~80 Ma, respectively, which we...

Along-strike variations in the timing of exhumation in the eastern Peruvian Andes

Sarah Falkowski & Todd A. Ehlers
Different controls and couplings between tectonics and climate-driven erosion have been suggested to explain the topographic and structural architecture of the Andes. One aspect of controversial discussions is the late Neogene incision of the Central Andean Plateau margin that has been interpreted as either the effect of climate change and increased river discharge on an already high plateau, or the effect of relatively young surface uplift. On the eastern flank of the Andean Plateau, ~4...

Drivers of Topography in Fold-thrust Belts: A Perspective from Central Nepal

Paul R Eizenhöfer, Nadine McQuarrie & Suryodoy Ghoshal(
Topography in fold-thrust belts over geologic time reflects the development of an orogenic Coulomb wedge that represents a balance of tectonic and erosional forcings. The establishment of critically tapered topography is generally viewed under two contrasting mechanical frameworks: (i) shortening and rock uplift are occurring everywhere suggesting an orogenic wedge under mechanical failure everywhere; and (ii) rock displacement takes place along discrete fault planes, including the translation of uplifted topography laterally. Here we investigate whether...

Intragranular halogen (F, Cl, Br), S and δ37Cl variability as determined by SIMS in sodalite and eudialyte from the Ilímaussaq intrusion, South Greenland

Hans G. M. Eggenkamp, Michael A. W. Marks , Thomas Ludwig & Gregor Markl
Halogen (F, Cl and Br), S and δ37Cl variations within grains of Cl-rich minerals sodalite and eudialyte from peralkaline rocks of the Ilímaussaq intrusion were determined using Secondary Ion Mass Spectrometry (SIMS). Samples show either sodalite and eudialyte in direct contact, or sodalite/eudialyte embedded in Cl-free minerals (nepheline, feldspar). Comparing samples allows deciphering potential halogen and S exchange between these minerals during rock cooling. Results suggest that sodalite (7 wt%) and eudialyte (1.2 wt%) have...

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...

Petrology and Geochronology of foidites and melilitites in SW Germany and E France

Thomas Binder , Benjamin F. Walter & Michael A. W. Marks
Foidites and melilitites are strongly SiO2-undersaturated rocks that form by extremely low degrees of partial melting of the metasomatically overprinted lithospheric mantle. In Central Europe, they occur in volcanic fields, dike swarms or as isolated stocks and diatremes. Our detailed study on foidites from SW Germany indicates two distinct age groups with marked differences in mineralogy and mineral chemistry: Based on in-situ U Pb age data (apatite, perovskite, zircon) a Miocene cohort (~ 9–19 Ma)...

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...

Granulometric and lithologic control on heavy mineral distribution in Alpine fluvial sediment

Ariane Djahansouzi, Laura Stutenbecker, Daniela Krieg & Christoph Glotzbach
Heavy mineral studies are dependent on many variables that should be considered in order to avoid erroneous provenance interpretations. Firstly, sediment transported and deposited by larger rivers is the result of the erosion of several lithological units present in the catchment with potentially differing mineral fertilities. Secondly, possible bias arises from the narrow sand-size window that is typically considered for single-grain analysis in sedimentary provenance studies. Quantifying and understanding the resulting bias is crucial for...

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