Lithospheric structure, evolution and diamond prospectivity of the Rehoboth Terrane and western Kaapvaal Craton, southern Africa: Constraints from broadband magnetotellurics

Müller, Mark; Jones, Alan G.; Evans, Robert; Grütter, Herman; Hatton, C. J.; García, Xavier; Hamilton, Mark P.; Miensopust, M. P.; Cole, P.; Ngwisanyi, T.; Hutchins, David A.; Fourie, C.J.S.; Jelsma, Hielke A.; Evans, Shane; Aravanis, T.; Pettit, W.; Webb, S. J.; Wasborg, Jan

doi:10.1016/j.lithos.2009.06.023

Cited by 93 publications

(101 citation statements)

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“…This 600 km long profile consists of 31 broad band MT sites and crosses the Magondi Mobile Belt and the Ghanzi-Chobe Belt as well as some marginal parts of the Zimbabwe Craton. Similar to the KIM-NAM profile discussed by Muller et al (2009), the Zimbabwe Craton is associated with a resistive lithospheric mantle indicating the coolest geotherm and thus the thickest lithosphere. Thinner lithosphere interpreted on the basis of lower electrical resistivities are found below the mobile belts.…”

Section: Making a Continent -Case Studiessupporting

confidence: 58%

“…Constable, 2006, and references therein), a lower bulk resistivity is indicative of a hotter geotherm, which is associated with a thinner lithosphere. Muller et al (2009) compared the geotherms derived from the electrical resistivity profiles to geotherms recorded in xenoliths from kimberlite pipes, which represent thermal conditions during eruption. Miensopust et al (2011) show 2D inversion results of a second profile (ZIM) of the SAMTEX data set (Figures 3 and 4b)).…”

Section: Making a Continent -Case Studiesmentioning

confidence: 99%

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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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Section: Making a Continent -Case Studiessupporting

confidence: 58%

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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“…This lithospheric thickness is typical for orogenic belts [Khoza et al, 2013;Miensopust et al, 2011;Muller et al, 2009], which, taken by itself, supports the notion that the Irumide Belt formed entirely during the Irumide Orogeny of the late Mesoproterozoic -Neoproterozoic age. However, U-Pb geochronology on detrital…”

Section: Elua Precambrian Lithospheric Structuresupporting

confidence: 79%

“…On the eastern edge of the WLUA profile, the resistive mantle thins to 180 km depth, suggesting that the Lufilian Belt SCLM is thinner than the SCLM beneath the Bangweulu Block and is typical for the SCLM of an orogenic belt [Khoza et al, 2013;Miensopust et al, 2011;Muller et al, 2009]. The resistivities of this feature range from 100s to well over 10,000 Ωm requiring an anhydrous, cold SCLM.…”

Section: Magnetotelluric Resultsmentioning

confidence: 96%

“…MT maps the lateral and vertical subsurface resistivity structure, and is sensitive to variations in temperature, composition, and interconnected conductors, such as fluid, melt, or metals. As a result, MT is a powerful tool to investigate lithospheric structure Alan G Jones, 1999;Khoza et al, 2013;Miensopust et al, 2011;Muller et al, 2009]. In addition to the mantle-probing MT data, we also use high-resolution aeromagnetic data over the Mwembeshi Shear Zone and surrounding Irumide and Southern Irumide Belts provided by the Geological Survey Department of Zambia to unveil the upper crustal structure (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Geophysical and petrological constraints on ocean plate dynamics

Sarafian¹

2017

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This thesis investigates the formation and subsequent motion of oceanic lithospheric plates through geophysical and petrological methods. Ocean crust and lithosphere forms at mid-ocean ridges as the underlying asthenosphere rises, melts, and flows away from the ridge axis. In Chapters 2 and 3, I present the results from partial melting experiments of mantle peridotite that were conducted in order to examine the mantle melting point, or solidus, beneath a mid-ocean ridge. Chapter 2 determines the peridotite solidus at a single pressure of 1.5 GPa and concludes that the oceanic mantle potential temperature must be ~60 ºC hotter than current estimates. Chapter 3 goes further to provide a more accurate parameterization of the anhydrous mantle solidus from experiments over a range of pressures. This chapter concludes that the range of potential temperatures of the mantle beneath mid-ocean ridges and plumes is smaller than currently estimated. Once formed, the oceanic plate moves atop the underlying asthenosphere away from the ridge axis. Chapter 4 uses seafloor magnetotelluric data to investigate the mechanism responsible for plate motion at the lithosphere-asthenosphere boundary. The resulting two dimensional conductivity model shows a simple layered structure. By applying petrological constraints, I conclude that the upper asthenosphere does not contain substantial melt, which suggests that either a thermal or hydration mechanism supports plate motion. Oceanic plate motion has dramatically changed the surface of the Earth over time, and evidence for ancient plate motion is obvious from detailed studies of the longer lived continental lithosphere. In Chapter 5, I investigate past plate motion by inverting magnetotelluric data collected over eastern Zambia. The conductivity model probes the Zambian lithosphere and reveals an ancient subduction zone previously suspected from surface studies. This chapter elucidates the complex lithospheric structure of eastern Zambia and the geometry of the tectonic elements in the region, which collided as a result of past oceanic plate motion. Combined, the chapters of this thesis provide critical constraints on ocean plate dynamics.

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Magnetotelluric investigations of the lithosphere beneath the central Rae craton, mainland Nunavut, Canada

Spratt¹,

Skulski

Craven

et al. 2014

JGR Solid Earth

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New magnetotelluric soundings at 64 locations throughout the central Rae craton on mainland Nunavut constrain 2-D resistivity models of the crust and lithospheric mantle beneath three regional transects. Responses determined from colocated broadband and long-period magnetotelluric recording instruments enabled resistivity imaging to depths of > 300 km. Strike analysis and distortion decomposition on all data reveal a regional trend of 45-53°, but locally the geoelectric strike angle varies laterally and with depth. The 2-D models reveal a resistive upper crust to depths of 15-35 km that is underlain by a conductive layer that appears to be discontinuous at or near major mapped geological boundaries. Surface projections of the conductive layer coincide with areas of high grade, Archean metasedimentary rocks. Tectonic burial of these rocks and thickening of the crust occurred during the Paleoproterozoic Arrowsmith (2.3 Ga) and Trans-Hudson orogenies (1.85 Ga). Overall, the uppermost mantle of the Rae craton shows resistivity values that range from 3000 Ω m in the northeast (beneath Baffin Island and the Melville Peninsula) to~10,000 Ω m beneath the central Rae craton, to >50,000 Ω m in the south near the Hearne Domain. Near-vertical zones of reduced resistivity are identified within the uppermost mantle lithosphere that may be related to areas affected by mantle melt or metasomatism associated with emplacement of Hudsonian granites. A regional decrease in resistivities to values of~500 Ω m at depths of 180-220 km, increasing to 300 km near the southern margin of the Rae craton, is interpreted as the lithosphere-asthenosphere boundary.

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Lithospheric structure, evolution and diamond prospectivity of the Rehoboth Terrane and western Kaapvaal Craton, southern Africa: Constraints from broadband magnetotellurics

Cited by 93 publications

References 50 publications

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

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

Geophysical and petrological constraints on ocean plate dynamics

Magnetotelluric investigations of the lithosphere beneath the central Rae craton, mainland Nunavut, Canada

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