Lithospheric low-velocity zones associated with a magmatic segment of the Tanzanian rift, East Africa

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dc.contributor.authorPlasman, M.
dc.contributor.authorTiberi, C.
dc.contributor.authorEbinger, C.
dc.contributor.authorGautier, S.
dc.contributor.authorAlbaric, J.
dc.contributor.authorPeyrat, S.
dc.contributor.authorDéverchère, J.
dc.contributor.authorLe Gall, B.
dc.contributor.authorTarits, P.
dc.contributor.authorRoecker, S.
dc.contributor.authorWambura, F.
dc.contributor.authorMuzuka, A.
dc.contributor.authorMulibo, G.
dc.contributor.authorMtelela, K.
dc.contributor.authorMsabi, M.
dc.contributor.authorKianji, G.
dc.contributor.authorHautot, S.
dc.contributor.authorPerrot, J.
dc.contributor.authorGama, R.
dc.date.accessioned2020-03-24T12:06:39Z
dc.date.available2020-03-24T12:06:39Z
dc.date.issued2017
dc.descriptionAbstract. Full Text Article available at https://doi.org/10.1093/gji/ggx177en_US
dc.description.abstractRifting 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 × 200 km2 area encompassing the South Kenya magmatic rift, the NTD and the Ngorongoro-Kilimanjaro transverse volcanic chain. Cratonic nature of the lithosphere is clearly evinced through thick (up to ca. 40 km) homogeneous crust beneath the rift shoulders. Where rifting is present, Moho rises up to 27 km depth and the crust is strongly layered with clear velocity contrasts in the RF signal. The Vp/Vs ratio reaches its highest values (ca. 1.9) beneath volcanic edifices location and thinner crust, advocating for melting within the crust. We also clearly identify two major low-velocity zones (LVZs) within the NTD, one in the lower crust and the second in the upper part of the mantle. The first one starts at 15–18 km depth and correlates well with recent tomographic models. This LVZ does not always coexist with high Vp/Vs ratio, pleading for a supplementary source of velocity decrease, such as temperature or composition. At a greater depth of ca. 60 km, a mid-lithospheric discontinuity roughly mimics the step-like and symmetrically outward-dipping geometry of the Moho but with a more slanting direction (NE–SW) compared to the NS rift. By comparison with synthetic RF, we estimate the associated velocity reduction to be 8–9 per cent. We relate this interface to melt ponding, possibly favouring here deformation process such as grain-boundary sliding (EAGBS) due to lithospheric strain. Its geometry might have been controlled by inherited lithospheric fabrics and heterogeneous upper mantle structure. We evidence that crustal and mantle magmatic processes represent first order mechanisms to ease and locate the deformation during the first stage of a cratonic lithospheric breakup.en_US
dc.identifier.citationPlasman, M., Tiberi, C., Ebinger, C., Gautier, S., Albaric, J., Peyrat, S., ... & Wambura, F. (2017). Lithospheric low-velocity zones associated with a magmatic segment of the Tanzanian Rift, East Africa. Geophysical Journal International, 210(1), 465-481.en_US
dc.identifier.otherhttps://doi.org/10.1093/gji/ggx177
dc.identifier.urihttp://hdl.handle.net/20.500.12661/2347
dc.language.isoenen_US
dc.publisherOxford University Pressen_US
dc.subjectLithospheric strainen_US
dc.subjectCrust/mantle rheologyen_US
dc.subjectSeismic sedimentologyen_US
dc.subjectMagmatic branchen_US
dc.subjectInherited structureen_US
dc.subjectStress regimeen_US
dc.subjectTeleseismic dataen_US
dc.subjectCrustal thicknessen_US
dc.subjectCratonic lithosphereen_US
dc.titleLithospheric low-velocity zones associated with a magmatic segment of the Tanzanian rift, East Africaen_US
dc.typeArticleen_US
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