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The Sheahan Diamond Literature Reference Compilation - Scientific and Media Articles based on Major Keyword - Geophysics - Magnetotellurics
The Sheahan Diamond Literature Reference Compilation is compiled by Patricia Sheahan who publishes on a monthly basis a list of new scientific articles related to diamonds as well as media coverage and corporate announcements called the Sheahan Diamond Literature Service that is distributed as a free pdf to a list of followers. Pat has kindly agreed to allow her work to be made available as an online digital resource at Kaiser Research Online so that a broader community interested in diamonds and related geology can benefit. The references are for personal use information purposes only; when available a link is provided to an online location where the full article can be accessed or purchased directly. Reproduction of this compilation in part or in whole without permission from the Sheahan Diamond Literature Service is strictly prohibited. Return to Diamond Keyword Index
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
Each article reference in the SDLRC is tagged with one or more key words assigned by Pat Sheahan to highlight the main topics of the article. In an effort to make it easier for users to track down articles related to a specific topic, KRO has extracted these key words and developed a list of major key words presented in this Key Word Index to which individual key words used in the article reference have been assigned. In most of the individual Key Word Reports the references are in crhonological order, though in some such as Deposits the order is first by key word and then chronological. Only articles classified as "technical" (mainly scientific journal articles) and "media" (independent media articles) are included in the Key Word Index. References that were added in the most recent monthly update are highlighted in yellow.
Articles tagged Geophysics - Magnetotelluricsinvolve magnetotellurics, a geophysical method that involves measuring the earth's sub-surface conductivity by measuring magnetic field variation. Whatever this means, I am not there yet. I do know it has nothing to do with Magneto of the X-Men, about whom I think every time I hear this word.
Lithospheric structure, evolution and diamond prospectivity of the Rehoboth Terrane and western Kaapvaal Craton, southern Africa: constraints from broadband
Rodrigues Pinto, L.G., Banik de Padua, M., Ussami, N., Vitorello, I., Lopes Padhilha, A., Braitenberg, C.
Magnetotelluric deep soundings, gravity and geoid in the south Sao Francisco craton: geophysical indicators of cratonic lithosphere rejuvenation and crustal underplating.
Earth and Planetary Science Letters, Vol. 297, 3-4, pp. 423-434.
Rodrigues Pinto, L.G., Banik de Padua, M., Ussami, N., Vitorello, I., Lopes Padhilha, A., Braitenberg, C.
Magnetotelluric deep soundings, gravity and geoid in the south Sao Francisco craton: geophysical indicators of cratonic lithosphere rejuvenation and crustal underplating.
Earth and Planetary Science Letters, Vol. 297, 3-4, pp. 423-434.
Lithospheric structures and Precambrian terrane boundaries in northeastern Botswana revealed through magnetotelluric profiling as part of Southern Africa...
Journal of Geophysical Research, Vol. 116, B02401 21p.
Lithospheric structure of an Archean craton and adjacent mobile belt revealed from 2-D and 3-D inversion of magnetotelluric data: example from southern Congo craton in northern Namibia.
Journal of Geophysical Research, Vol. 118, 8, pp. 4378-4397.
Canadian Journal of Earth Sciences, Vol. 55, pp. 295-307.
Canada, Alberta
geophysics - electromagnetics, magnetotellurics
Abstract: The study of ancient plate boundaries can provide insights into the past and present-day tectonic processes. Here, we describe a magnetotellurics (MT) study of the Precambrian basement of the Hay River Fault (HRF) in northwest Alberta, which is the southwest segment of the Great Slave Lake shear zone. New broadband MT data were collected to give a clearer image of the crustal structure. The Western Canada Sedimentary Basin was imaged as a low-resistivity layer above the resistive crystalline basement. Four basement conductors were defined, and correlate with the terrane boundaries delineated with aeromagnetic data. These are (1) a major conductor in the Kiskatinaw domain, (2) a conductor on the boundary of the Ksituan and Chinchaga domains, (3) a conductor on the boundary of the Chinchaga and Buffalo Head domains, and (4) a conductor near the HRF. Both (1) and (2) correspond to areas of high seismic reflectivity. The low resistivity can be explained by interconnected grain boundary graphite or sulfide phases deposited by metamorphic fluid migration. The HRF was not definitively located in previous studies. The new data show that the HRF could be thin (1 km) or wide (10 km) and located at the boundary of the contrasting aeromagnetic anomalies or further to the north. Various tectonic processes are proposed to interpret the possible locations of the HRF. No electrical anisotropy structure is required to interpret the MT data in this study.
Journal of Asian Earth Sciences, Vol. 176, pp. 253-263.
India
geophysics - magnetotellurics
Abstract: The vertical extension and structure of the sub-continental lithospheric mantle beneath the Archean Dharwar craton is the main attraction of the work presented here. To delineate the electrical conductivity structure of the Dharwar craton, a magnetotelluric study is carried out. This study comprises magnetotelluric data at 22 stations along a west-east slanting profile. Inter-station spacing is approximately 15?km. This magnetotelluric study is initiated from Dandeli (in the west) to Sindhanur (in the east side). The preferable geoelectric strike directions for the crust and lithospheric mantle are N3°E and N16°E respectively. A 2-dimensional (2-D) resistivity model derived by using the crustal and lithospheric mantle strike azimuths, identified conductive features in the stable continental Dharwar craton. In the crust, prominent conductors are present in the eastern and western part of the profile. A conducting feature is present in the deeper crust associated with the Chitradurga shear zone (CSZ). The study infers a thick lithosphere beneath Dharwar craton as a preserved cratonic nucleus on the eastern and a few conductive anomalies in the western part of the Dharwar craton. The model shows two separate conductors in the depth range of 110-250?km. This study shows, the possibility of presence of kimberlite melt in the western Dharwar craton in the depth range of 110-150?km.
Minerals MDPI, Vol. 10, 1107, doi.10.3390/ min10121107 28p. Pdf
Mantle
geophysics - magnetotellurics
Abstract: Magnetotelluric (MT) surveys have identified anisotropic conductive anomalies in the mantle of the Cocos and Nazca oceanic plates, respectively, offshore Nicaragua and in the eastern neighborhood of the East Pacific Rise (EPR). Both the origin and nature of these anomalies are controversial as well as their role in plate tectonics. The high electrical conductivity has been hypothesized to originate from partial melting and melt pooling at the lithosphere-asthenosphere boundary (LAB). The anisotropic nature of the anomaly likely highlights high-conductivity channels in the spreading direction, which could be further interpreted as the persistence of a stable liquid silicate throughout the whole oceanic cycle, on which the lithospheric plates would slide by shearing. However, considering minor hydration, some mantle minerals can be as conductive as silicate melts. Here I show that the observed electrical anomaly offshore Nicaragua does not correlate with the LAB but instead with the top of the garnet stability field and that garnet networks suffice to explain the reported conductivity values. I further propose that this anomaly actually corresponds to the fossilized trace of the early-stage LAB that formed near the EPR about 23 million years ago. Melt-bearing channels and/or pyroxenite underplating at the bottom of the young Cocos plate would transform into garnet-rich pyroxenites with decreasing temperature, forming solid-state high-conductivity channels between 40 and 65 km depth (1.25-1.9 GPa, 1000-1100 °C), consistently with experimental petrology.
AGU Research Letter, 10.1029/2021GL092570 11p. Pdf
Africa, South Africa
geophysics - magnetotellurics
Abstract: Measuring the composition of the Earth’s mantle is important for understanding mantle processes like plate tectonics, but is surprisingly difficult. Our most accurate information comes from mantle rocks, called xenoliths, that have been brought to the surface during volcanic eruptions. However, these rocks only come from a handful of places. We tend to expect that the rest of the mantle has the same composition as the xenoliths but this might be incorrect. We tested whether xenolith compositions really are representative of the broader mantle by comparing them with compositions interpreted from electrical conductivity models of the mantle. We carried out this comparison in the Kimberley region, South Africa, because it has excellent xenolith and electrical conductivity data. Our results show that xenolith compositions do seem to be broadly representative but there are two important differences: Hydrous minerals found in some xenoliths may not be spatially extensive depending on temperature, and the water contents of some other minerals are different from the broader region. This means that the compositions of xenoliths are at least partly controlled by local processes. Electrical conductivity data may be more useful for measuring some aspects of the composition of the broader mantle, especially its water content.
Journal of Geophysical Research, 10.1029/2021JB023105, 28p.
Africa, South Africa
geophysics - magnetotellurics
Abstract: The present-day composition of Earth's tectonic plates results from past geological processes. We can learn about Earth's composition from deep rock samples that are carried to the surface during volcanic eruptions and by probing its physical properties, like electrical conductivity, with geophysics. In southern Africa, there are extensive deep rock samples, which have been brought to the surface by kimberlite volcanoes that also host diamonds, and also extensive geophysical data. In this article, we compare the rock compositions with electrical conductivity to learn more about Earth's composition. Our results show that the oldest parts of the plates, which retain compositions similar to their initial composition, appear resistive. On the other hand, regions that have been intruded by deep fluids or molten rock can be resistive or conductive, depending on the types of minerals that were formed during the intrusion. The kimberlite volcanoes mostly erupted through the edges of the most resistive parts of the plates and did not erupt through the conductors. These results will help us to make more accurate interpretations about the composition of parts of the Earth where we do not have deep rock samples.
