Helium isotopes at Rungwe Volcanic Province, Tanzania, and the origin of East African Plateaux

Hilton, David R.; Halldórsson, Sæmundur A.; Barry, Peter H.; Fischer, Tobias P.; Moor, J. Maarten de; Ramírez, Carlos; Mangasini, F.; Scarsi, P.

doi:10.1029/2011gl049589

Cited by 72 publications

(58 citation statements)

References 32 publications

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“…1b). Seismic tomography with existing sparse seismic data indicates a localized low-velocity zone in the mantle below Rungwe (O'Donnell et al, 2013), and isotopic analyses of recent volcanic rocks suggest a deep plume-influenced source, at least for the youngest magmatism (Hilton et al, 2011). However, the original cause of magmatism, the distribution of elevated temperatures and magma at depth beneath the Malawi rift, and the relationship between magmatism and extension remain unknown.…”

Section: Tectonic Backgroundmentioning

confidence: 99%

Acquisition of a Unique Onshore/Offshore Geophysical and Geochemical Dataset in the Northern Malawi (Nyasa) Rift

Shillington

Gaherty

Ebinger

et al. 2016

Seismological Research Letters

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The Study of Extension and maGmatism in Malawi aNd Tanzania (SEGMeNT) project acquired a comprehensive suite of geophysical and geochemical datasets across the northern Malawi (Nyasa) rift in the East Africa rift system. Onshore/offshore active and passive seismic data, long-period and wideband magnetotelluric data, continuous Global Positioning System data, and geochemical samples were acquired between 2012 and 2016. This combination of data is intended to elucidate the sedimentary, crustal, and upper-mantle architecture of the rift, patterns of active deformation, and the origin and age of rift-related magmatism. A unique component of our program was the acquisition of seismic data in Lake Malawi, including seismic reflection, onshore/offshore wide-angle seismic reflection/refraction, and broadband seismic data from lake-bottom seismometers, a towed streamer, and a large towed air-gun source. SCIENCE MOTIVATION AND EXPERIMENT SUMMARYThe primary scientific goal of the Study of Extension and maGmatism in Malawi aNd Tanzania (SEGMeNT) project is to examine the emergence and early evolution of two fundamental features of all divergent plate boundaries: magmatism and segmentation. Magmatism accommodates a significant percentage of plate separation at most midocean ridges and late-stage continental rifts. Likewise, transform faults demarcate discrete spreading segments in midocean ridges, which are broadly characterized by more robust magmatism at their centers than at their edges (Macdonald et al., 1988;Lin et al., 1990). Well-developed magmatic and tectonic segmentation is also observed in late-stage continental rifts and new ocean basins (Taylor et al., 1995;Ebinger and Casey, 2001;Keir et al., 2009), but little is known about the controls on the initiation and development of magmatism and segmentation in immature rifts. Our project is focused on addressing the following questions:• When, where, and why does magmatism initiate in rifts, and what is its role in accommodating extension? • What controls the development of tectonic segmentation in early-stage rifts? How is it manifested in 4D patterns of magmatism and deformation?To address the questions above, we acquired an integrated geophysical and geochemical dataset across the northern Malawi (Nyasa) rift in the southern part of the East Africa Rift system (EARS). Our team included universities and geological surveys in the United States, Malawi, and Tanzania. The following datasets were acquired as a part of the SEGMeNT project: onshore/offshore active and passive seismic data, long-period and wideband magnetotelluric (MT) data, continuous Global Positioning System (GPS) data, and geochemical samples. This is the first integrated geophysical and geochemical dataset acquired across and within any of the great African rift lakes that can constrain rift architecture and processes at a range of scales. TECTONIC BACKGROUNDThe northern Malawi (Nyasa) rift in the Western Branch of the EARS is an excellent locality to examine the early stages of rifting in str...

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Section: Tectonic Backgroundmentioning

confidence: 99%

Acquisition of a Unique Onshore/Offshore Geophysical and Geochemical Dataset in the Northern Malawi (Nyasa) Rift

Shillington

Gaherty

Ebinger

et al. 2016

Seismological Research Letters

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“…The second type invokes one or more plumes with plume head material ponded beneath the lithosphere fed by a narrow ($100-200 km diameter) plume tail [e.g., Green et al, 1991;Slack et al, 1994;Burke, 1996;Ebinger and Sleep, 1998;George et al, 1998;Chang and Van der Lee, 2011]. And the third grouping of models attributes the Cenozoic tectonism to a superplume [e.g., Hilton et al, 2011;Nyblade, 2011;Adams et al, 2012;Hansen et al, 2012]. If the African superplume is a through-going mantle structure then the latter type of model is obviously favored.…”

Section: Introductionmentioning

confidence: 99%

The P and S wave velocity structure of the mantle beneath eastern Africa and the African superplume anomaly

Mulibo

Nyblade

2013

Geochem Geophys Geosyst

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P and S relative arrival time residuals from teleseismic earthquakes recorded on over 60 temporary AfricaArray broadband seismic stations deployed in Uganda, Tanzania, and Zambia between 2007 and 2011 have been inverted, together with relative arrival time residuals from earthquakes recorded by previous deployments, for a tomographic image of mantle wave speed variations extending to a depth of 1200 km beneath eastern Africa. The image shows a low‐wave speed anomaly (LWA) well developed at shallow depths (100–200 km) beneath the Eastern and Western branches of the Cenozoic East African rift system and northwestern Zambia, and a fast wave speed anomaly at depths ≤ 350 km beneath the central and northern parts of the East African Plateau and the eastern and central parts of Zambia. At depths ≥350 km the LWA is most prominent under the central and southern parts of the East African Plateau and dips to the southwest beneath northern Zambia, extending to a depth of at least 900 km. The amplitude of the LWA is consistent with a ∼150–300 K thermal perturbation, and its depth extent indicates that the African superplume, originally identified as a lower mantle anomaly, is likely a whole mantle structure. A superplume extending from the core‐mantle boundary to the surface implies an origin for the Cenozoic extension, volcanism, and plateau uplift in eastern Africa rooted in the dynamics of the lower mantle.

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“…A superplume extending from the CMB to the surface implies an origin for the Cenozoic extension, volcanism and plateau uplift in eastern Africa rooted in the dynamics of the lower mantle (Mulibo and Nyblade 2013). Hilton et al (2011) reported helium isotope ratios of lavas and tephra of the Rungwe Volcanic Province in southern Tanzania. Values as high as 15 RA far exceed typical upper mantle values, which are attributed to the African superplume (Hilton et al 2011).…”

Section: African Hotspotsmentioning

confidence: 98%

“…Hilton et al (2011) reported helium isotope ratios of lavas and tephra of the Rungwe Volcanic Province in southern Tanzania. Values as high as 15 RA far exceed typical upper mantle values, which are attributed to the African superplume (Hilton et al 2011). Steinberger (2000) calculated the motion of hotspots in East Africa and the deformation of their underlying plume conduits using models of global mantle flow and suggested the presence of a comparatively broad upwelling rather than localized plumes.…”

Section: African Hotspotsmentioning

confidence: 98%

“…Because more and more seismographs including OBS stations will be deployed in the non-or lessinstrumented regions, and seismic imaging techniques will be further improved, we will be able to image the crust and mantle structure better and better. Geochemical studies (e.g., Courtier et al 2007;Hilton et al 2011;Wang et al 2013), laboratory experiments (e.g., Kumagai et al 2008;Druken et al 2013;Kincaid et al 2013), and numerical simulations (e.g., Leng and Gurnis 2012;Bossmann and van Keken 2013;van Keken et al 2013) are necessary and important for interpreting the seismological observations. Integrating all the multidisciplinary findings can greatly advance our understanding of the origin of hotspots and mantle plumes as well as deep Earth structure and dynamics.…”

Section: Implications For Mantle Dynamicsmentioning

confidence: 99%

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Hotspots and Mantle Plumes

Zhao

2015

Multiscale Seismic Tomography

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Seismic images under 62 possible hotspots are reviewed for understanding the origin of hotspots and mantle plumes. Plume-like, continuous low-velocity anomalies are visible beneath Hawaii, Tahiti, Louisville, Iceland, Cape Verde, Reunion, Kerguelen, Amsterdam, Afar, Eifel, Hainan, Yellowstone and Cobb hotspots, suggesting that they may be 13 whole-mantle plumes originating from the core-mantle boundary. These plumes exhibit tilted images, suggesting that plumes are not fixed in the mantle but can be deflected by the mantle flow. Upper-mantle plumes seem to exist beneath Cameroon, Easter, Azores, Vema, East Australia and Erebus hotspots. A mid-mantle plume may exist under the San Felix hotspot. Active intraplate volcanoes in Northeast Asia and Southwest China are caused by hot and wet upwelling flows in the big mantle wedge above the stagnant slab in the mantle transition zone. Although low-velocity zones appear at some depth under other hotspots, their plume features are not clear. The complex images under hotspots reflect strong lateral variations in temperature, viscosity and possibly composition of the mantle, which control the generation and ascent of mantle plumes and the flow pattern of mantle convection.

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Helium isotopes at Rungwe Volcanic Province, Tanzania, and the origin of East African Plateaux

Cited by 72 publications

References 32 publications

Acquisition of a Unique Onshore/Offshore Geophysical and Geochemical Dataset in the Northern Malawi (Nyasa) Rift

Acquisition of a Unique Onshore/Offshore Geophysical and Geochemical Dataset in the Northern Malawi (Nyasa) Rift

The P and S wave velocity structure of the mantle beneath eastern Africa and the African superplume anomaly

Hotspots and Mantle Plumes

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