Volcanism of the Baikal rift zone

Kiselev, A. I.

doi:10.1016/0040-1951(87)90093-x

Cited by 40 publications

(33 citation statements)

References 12 publications

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“…Miocene to Pliocene basaltic plateaus and fields cover a huge area of Central Asia, Mongolia and Trans Baikal (Kiselev, 1987;Kepezhinskas, 1979;Dobretsov and Ashchepkov, 1991;Ionov et al, 1992Ionov and Hofmann, 2007;Ashchepkov et al, 2003;Johnson et al, 2005). The Vitim basalt plateau was formed mainly in Miocene times, and is the largest of the Cenozoic plateaus in Trans Baikal.…”

Section: Location and Geologymentioning

confidence: 96%

Pyroxenites and megacrysts from Vitim picrite-basalts (Russia): Polybaric fractionation of rising melts in the mantle?

Ashchepkov

André

Downes

et al. 2011

Journal of Asian Earth Sciences

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Section: Location and Geologymentioning

confidence: 96%

Pyroxenites and megacrysts from Vitim picrite-basalts (Russia): Polybaric fractionation of rising melts in the mantle?

Ashchepkov

André

Downes

et al. 2011

Journal of Asian Earth Sciences

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“…A similar pattern is observed during the evolution of the Red Sea Rift, where ∼25-Myr-old rift-parallel dykes focus near the ∼30-Myr-old rift margins and the youngest volcanoes focus along the ridge axis 11 . Even in far less magmatically active settings, such as the Baikal Rift (Siberia) or the Chaine des Puys (CdP) in the Cenozoic rift system of France, off-rift volcanism occurred after the onset of rifting 7,8 .During rift initiation, the lithosphere thins by ductile stretching beneath a rift valley formed from normal faulting 12 . The upwelling asthenosphere melts by adiabatic decompression, with the greatest degree of partial melting beneath the most thinned rift valley 1,2 .…”

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Off-rift volcanism in rift zones determined by crustal unloading

et al. 2014

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When continents are stretched over a long period of time, deep elongated rift valleys form at Earth's surface and zones of ponded magma, centred beneath the rift, form at the crust-mantle boundary 1,2 . Ascending magma sometimes erupts within the rift valley 3,4 or, counterintuitively, at volcanic fields away from the rift valley that are o set by tens of kilometres from the source of magma at depth 5-8 . The controls on the distribution of this o -rift volcanism are unclear. Here we use a numerical model of magmatic dyke propagation during rifting to investigate why some dykes reach the surface outside the rift valley, whereas others are confined to the valley. We find that the location of magmatism is governed by the competition between tectonic stretching and gravitational unloading pressure, caused by crustal thinning and faulting along the rift borders. When gravitational unloading dominates over tectonic stretching forces, dykes ascending from the ponded magma are steered towards the rift sides, eventually causing o -rift eruptions. Our model also predicts the formation of stacked magma sills in the lower crust above the magma-ponding zone, as well as the along-rift propagation of shallow dykes during rifting events, consistent with observations of magmatism and volcanism in rift zones globally. We conclude that rift topography-induced stress changes provide a fundamental control on the transfer of magma from depth to the surface.Continental rifts are commonly flanked by magmatism during their early stages 5,6 . In the Miocene-Recent Main Ethiopian Rift (MER), for example, many Pliocene volcanoes lie outside the Miocene rift border faults 9,10 ( Fig. 1). As the cumulative extension has increased, magmatism has become focused within the rift axis 3 . A similar pattern is observed during the evolution of the Red Sea Rift, where ∼25-Myr-old rift-parallel dykes focus near the ∼30-Myr-old rift margins and the youngest volcanoes focus along the ridge axis 11 . Even in far less magmatically active settings, such as the Baikal Rift (Siberia) or the Chaine des Puys (CdP) in the Cenozoic rift system of France, off-rift volcanism occurred after the onset of rifting 7,8 .During rift initiation, the lithosphere thins by ductile stretching beneath a rift valley formed from normal faulting 12 . The upwelling asthenosphere melts by adiabatic decompression, with the greatest degree of partial melting beneath the most thinned rift valley 1,2 . Although most studies focus on in-rift magmatism 3,4 , a model is needed to explain how off-rift volcanoes are fed. Progressive rift spreading results in the oldest volcanoes being transported away from the rift axis. However, such a process does not explain off-rift volcanism, with volcanoes located outside the rift border faults. Previous models for off-rift volcanoes include low-angle detachments tapping the asthenosphere to the sides of highly asymmetric rifts 13 , or the flexural response at the base of the footwall of the active rift border faults 5 . These models are unsatisfac...

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“…National borders are drawn in gray. Locations of the major Cenozoic volcanic fields (shown in red, b) and of major faults outside Lake Baikal are taken from [22]. Fig.…”

Section: Introductionmentioning

confidence: 99%

Asthenospheric flow and origin of volcanism in the Baikal Rift area

Lebedev

Meier

Hilst

2006

Earth and Planetary Science Letters

110

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The origin of low-volume, hotspot-like volcanism often observed in continental rift areas is debated, as is the nature of the flow in the mantle beneath. In this paper we assemble seismic constraints on the mantle flow below the Baikal Rift Zone. We combine new evidence from upper-mantle tomography and from a radially anisotropic shear-velocity profile measured beneath and SE of the rift with published shear-wave-splitting constraints on azimuthal anisotropy. Fast directions of azimuthal anisotropy are perpendicular to the rift on both of its sides. Stable Siberian-Platform lithosphere on the northern side extends down to 200 km; on the southern side, the lithosphere is only 60-70 km thick. This asymmetry, with the thick cratonic root forming a barrier to convective flow, inhibits a mid-ocean-ridge-like flow pattern. The radially anisotropic profile yields evidence for horizontal flow in the upper asthenosphere (60-100 km) SE of the rift but no evidence for vertical flow. These results are consistent with horizontal asthenospheric flow NW to SE perpendicular to the rift, from beneath the thick Siberian towards the thin Baikal-Mongolian lithosphere. When asthenosphere ascends from the 200-km depth beneath the craton to shallower depths beneath the rift, decompression melting of embedded veins of enriched rock can produce the hotspot-like basaltic volcanism observed. The occurrence of such veins of enriched mantle in sub-cratonic asthenosphere has been predicted by geochemical mantle models; we propose that sub-horizontal asthenospheric flow from beneath cratons is a common cause for hotspot-like volcanism in continental rift zones.

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Volcanism of the Baikal rift zone

Cited by 40 publications

References 12 publications

Pyroxenites and megacrysts from Vitim picrite-basalts (Russia): Polybaric fractionation of rising melts in the mantle?

Pyroxenites and megacrysts from Vitim picrite-basalts (Russia): Polybaric fractionation of rising melts in the mantle?

Off-rift volcanism in rift zones determined by crustal unloading

Asthenospheric flow and origin of volcanism in the Baikal Rift area

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