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| Tada, Noriko; Tarits, Pascal; Baba, Kiyoshi; Utada, Hisashi; Kasaya, Takafumi; Suetsugu, Daisuke. |
| We have conducted a seafloor magnetotelluric survey that images, for the first time, three-dimensional electrical conductivity structure in the upper mantle beneath the Society hotspot. A striking feature in our model is a high-conductivity anomaly a few hundred kilometers in diameter, which is continuous from the lowest part of the upper mantle to a depth of approximately 50km below sea level. Using theoretical and experimental results from mineral physics, we interpret the high-conductivity anomaly as evidence of the melt fraction up to 2.2vol.%, which is robust regardless of assumed temperature, and the existence of carbonated silicate melt beneath the hotspot. Our results suggest that the Society hotspot is a pathway for ascending volatiles from the... |
| Tipo: Text |
Palavras-chave: Hotspot; Marine magnetotellurics; Three-dimensional inversion; Volatiles; Partial melt. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00638/75054/75611.pdf |
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| Plasman, M.; Tiberi, C.; Ebinger, C.; Gautier, S; Albaric, J.; Peyrat, S.; Deverchere, Jacques; Le Gall, B.; Tarits, Pascal; Roecker, S.; Wambura, F.; Muzuka, A.; Mulibo, G.; Mtelela, K.; Msabi, M.; Kianji, G.; Hautot, S.; Perrot, J.; Gama, R.. |
| Rifting in a cratonic lithosphere is strongly controlled by several interacting processes including crust/mantle rheology, magmatism, inherited structure and stress regime. In order to better understand how these physical parameters interact, a 2 yr long seismological experiment has been carried out in the North Tanzanian Divergence (NTD), at the southern tip of the eastern magmatic branch of the East African rift, where the southward-propagating continental rift is at its earliest stage. We analyse teleseismic data from 38 broad-band stations ca. 25 km spaced and present here results from their receiver function (RF) analysis. The crustal thickness and Vp/Vs ratio are retrieved over a ca. 200 x 200 km(2) area encompassing the South Kenya magmatic rift,... |
| Tipo: Text |
Palavras-chave: Time-series analysis; Continental tectonics: extensional; Africa; Crustal imaging. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00638/75026/75673.pdf |
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| Plasman, Matthieu; Hautot, Sophie; Tarits, Pascal; Gautier, Stephanie; Tiberi, Christel; Le Gall, Bernard; Mtelela, Khalfan; Gama, Remigius. |
| Continental break-up is controlled by several parameters and processes (rheology, inherited structures, magmatism, etc). Their impact, chronology and interactions are still poorly known and debated, particularly when rifting interacts with cratons. In order to better understand the rifting initiation in a cratonic lithosphere, we analysed 22 magnetotelluric (MT) soundings collected along two East-West profiles in two different rift segments of the North Tanzanian Divergence. The North Tanzanian Divergence, where the East African Rift is at its earliest stage, is a remarkable example of the transition between magmatic to amagmatic rifting with two clearly identified segments. Only separated by a hundred kilometers, these segments, Natron (North) and Manyara... |
| Tipo: Text |
Palavras-chave: Magnetotellurics; 3-D inversion; North Tanzanian Divergence; East African rift; Lithospheric structure; CO2 content; Seismology; Joint interpretation. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74897/76062.pdf |
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| Leye, P. O.; Tarits, Pascal. |
| At and near the Earth surface, electromagnetic (EM) fields radiated from VLF transmitters are commonly used in geological exploration to determine the shallow Earth conductivity structure. Onboard satellites such as DEMETER, the electric and magnetic sensors detect the VLF signal in altitude. While we know for surface measurement that the VLF EM field recorded at some distance from the transmitter is a function of the ground conductivity, we do not know how this relationship changes when the field is measured at satellite altitude. Here we study the electromagnetic field radiated by a vertical electric dipole located on the Earth surface in the VLF range and measured at satellite altitude in a free space. We investigate the EM field as function of distance... |
| Tipo: Text |
Palavras-chave: VLF; Satellite; Earth. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00639/75141/75492.pdf |
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