A magnetotelluric study of the Damara Belt in Namibia

Ritter, O.; Weckmann, U.; Vietor, Tim; Haak, V.

doi:10.1016/s0031-9201(03)00078-5

Cited by 58 publications

(57 citation statements)

References 53 publications

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“…In a more recent study, densely spaced (4-12 km) MT stations were deployed across the western end of the conductor (Figure 7a) by Ritter et al (2003). Similar to earlier studies, an anomalous highly conductive middle to lower crust (resistivity as low as 5 Ωm) and a resistive upper crust (5000-15,000 Ωm) were detected (Figure 7b).…”

Section: Previous Crustal Conductivity Studies In Northern Namibia Ansupporting

confidence: 71%

An audio-magnetotelluric investigation of the Otjiwarongo and Katima Mulilo regions, Namibia

Jones

Müller

et al. 2014

GEOPHYSICS

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As an additional opportunistic component to the southern African magnetotelluric experiment, natural-source audiomagnetotelluric (AMT) data were acquired during phase IV to investigate the local-scale electric conductivity subsurface structure in the Otjiwarongo and Katima Mulilo regions (Namibia) as an aid in locating the installation points for high-voltage direct current earth electrodes. The study showed that the shallow subsurface of areas containing one measurement site in the Otjiwarongo region and three sites in the Katima Mulilo region have appropriate high conductivities for the optimal placement of the earth electrodes. Both of the AMT surveys are situated close to the edge of the orogenic Neo-Proterozoic Damara mobile belt (DMB). Previous studies all suggest the existence of a highly conductive midcrustal zone, which correlates well with the spatial location of the DMB. Two-dimensional inverse modeling of the Otjiwarongo AMT data confirms the existence of the high-conductive zone at midcrustal depths (10-15 km). The high conductivity of the DMB is explained by the presence of interconnected graphite in the marble units present. The Katima Mulilo inversion results are characterized by a conductive upper crustal layer that does not form part of the DMB conductive belt. It was deduced that at the uppermost subsurface (maximum ∼200 m), Kalahari sediments are responsible for the high conductivity observed, whereas at greater depth (up to 6 km), its cause remains enigmatic, albeit the hypothesis of ironstone or graphite being present and causing the observed conductive upper crust.

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Section: Previous Crustal Conductivity Studies In Northern Namibia Ansupporting

confidence: 71%

An audio-magnetotelluric investigation of the Otjiwarongo and Katima Mulilo regions, Namibia

Jones

Müller

et al. 2014

GEOPHYSICS

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“…In the same region through the Damara Belt in Namibia (see Figure 3), high resolution MT measurements were conducted by Ritter et al (2003b) and Weckmann et al (2003b) to study characteristics of the remnants of the continental collision in the Early Cambrian. Within two different experiments the regional structure of the Damara Belt with its high conductivity belt (de Beer et al, 1982b;van Zijl and de Beer, 1983) was investigated and a high resolution study of one of the major fault zones, the Waterberg Fault / Omaruru Lineament (WF/OL) was conducted.…”

Section: Making a Continent -Case Studiesmentioning

confidence: 99%

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

Weckmann

2011

Surv Geophys

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The African continent inherits a long history of continental accretion and breakup. The stage of "making" a continent goes back to the Archean, when the first continental masses formed cratons which mostly remained stable ever since. Subsequent collision of weaker continental masses was followed by several extension and compression episodes that resulted in the formation of supercontinents. After the assemblage of Gondwana, a period of predominantly "breaking" , i.e. the breakup of supercontinents, took over. The modern day African continent exhibits different types of margins; continental rifting occurs side by side with recent collision. Since the late 1960's Magnetotelluric (MT) experiments have played an important role in studies of the electrical conductivity structure of Africa. The early results significantly shaped the MT community's understanding of continental scale conductivity belts and basic characteristics of cratons and mobile belts on both crustal and lithospheric mantle scale for some decades. Modern MT studies in Africa have generally supported earlier results with high resistivities observed on cratons and low resistivities observed across mobile belts. Advances in instrumentation, data processing and interpretation resulted in higher resolution images of the lithosphere which in consequence induce an improved understanding of tectonic processes and geological prerequisites for the occurrence of natural resources. The high electrical conductivity of mobile belts and their relation to reactivated fault and detachment zones were often interpreted to characterize mobile belts as tectonic weak zones, which can accommodate stress and constitute zones along which continents can break. Recent breaking of the African continent can be studied on land across the East African rift; however, the lack of amphibian MT experiments across today's margins does not allow for good resolution of remnants of continental break-up processes. Naturally, the regions and the focus of the MT studies in Africa are diverse, but they all contribute to the story of making and breaking a continent.

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“…As bulk electrical conductivity is strongly dependent upon temperature, magnetotellurics offers an independent means of estimating subsurface temperature. Sutures, the remnants of plate collisions, have been found to be conductive over geologic time scales for reasons that are not fully understood (Tauber et al 2003;Ritter et al 2003b;Almeida et al 2005;Boerner et al 1996;Park et al 1991). The late Jurassic-early Cretaceous Bangong-Nujiang Suture in Central Tibet is located within an active continentcontinent collision zone, and hence its conductivity distribution may also reflect ongoing tectonic processes.…”

Section: Studies Of Physical Thermal and Compositional Statementioning

confidence: 99%

MT+, Integrating Magnetotellurics to Determine Earth Structure, Physical State, and Processes

Bedrosian

2007

Surv Geophys

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As one of the few deep-earth imaging techniques, magnetotellurics provides information on both the structure and physical state of the crust and upper mantle. Magnetotellurics is sensitive to electrical conductivity, which varies within the earth by many orders of magnitude and is modified by a range of earth processes. As with all geophysical techniques, magnetotellurics has a non-unique inverse problem and has limitations in resolution and sensitivity. As such, an integrated approach, either via the joint interpretation of independent geophysical models, or through the simultaneous inversion of independent data sets is valuable, and at times essential to an accurate interpretation. Magnetotelluric data and models are increasingly integrated with geological, geophysical and geochemical information. This review considers recent studies that illustrate the ways in which such information is combined, from qualitative comparisons to statistical correlation studies to multi-property inversions. Also emphasized are the range of problems addressed by these integrated approaches, and their value in elucidating earth structure, physical state, and processes.

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A magnetotelluric study of the Damara Belt in Namibia

Cited by 58 publications

References 53 publications

An audio-magnetotelluric investigation of the Otjiwarongo and Katima Mulilo regions, Namibia

An audio-magnetotelluric investigation of the Otjiwarongo and Katima Mulilo regions, Namibia

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

MT+, Integrating Magnetotellurics to Determine Earth Structure, Physical State, and Processes

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