Preferential localized thinning of lithospheric mantle in the melt-poor Malawi Rift

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dc.contributor.authorHopper, Emily
dc.contributor.authorGaherty, James B
dc.contributor.authorShillington, Donna J
dc.contributor.authorAccardo, Natalie J
dc.contributor.authorNyblade, Andrew A
dc.contributor.authorHoltzman, Benjamin K
dc.contributor.authorHavlin, Christopher
dc.contributor.authorScholz, Christopher A
dc.contributor.authorChindandali, Patrick R. N
dc.contributor.authorFerdinand, Richard W
dc.contributor.authorMulibo, Gabriel D
dc.contributor.authorMbogoni, Gabriel
dc.date.accessioned2021-04-20T13:36:46Z
dc.date.available2021-04-20T13:36:46Z
dc.date.issued2020-08
dc.description.abstractThe forces required to initiate rifting in cratonic plates far exceed the available tectonic forces. High temperatures and resul- tant melts can weaken the lithosphere, but these factors do not readily explain the extension of old and strong lithosphere in magma-poor rifts, such as the Malawi Rift. Here, new seismic converted-wave imaging shows that even in this magma-poor rift, upper-crustal rift basins are associated with localized preferential thinning of the lithospheric mantle. We calculated the beta factor, the ratio between current and prerift thickness, beneath the rift axis and found crustal beta of 1.7 ± 0.3 and lithospheric-mantle beta of 3.8 ± 1.7. Purely mechanical stretching cannot explain the preferential lithospheric mantle thin- ning—instead, thinning of the rheological lithosphere was probably augmented by thermochemical rejuvenation and erosion. Although local surface-wave-derived shear-wave velocities preclude a substantially elevated temperature and partial melt today, fusible materials preserved in the lower lithosphere that underlie the Ubendian Belt and its bounding subduction-related sutures in which the Malawi Rift nucleated may have provided an early supply of melt that enabled localized lithospheric altera- tion and/or removal. A plume-related or other asthenospheric perturbation would preferentially melt the more fusible litho- spheric materials and the rising melts would heat and weaken progressively shallower parts of the lithosphere, which spatially localizes weakening (hence the lithospheric-mantle thinning) and enables the onset of rifting.en_US
dc.description.sponsorshipFunding for this work was provided by the NSF Continental Dynamics Program, with grants EAR-1110921, 1109293 and 1110882.en_US
dc.identifier.citationHopper, E., Gaherty, J.B., Shillington, D.J. et al. Preferential localized thinning of lithospheric mantle in the melt-poor Malawi Rift. Nat. Geosci. 13, 584–589 (2020). https://doi.org/10.1038/s41561-020-0609-yen_US
dc.identifier.doidoi.org/10.1038/s41561-020-0609-y
dc.identifier.urihttp://hdl.handle.net/20.500.11810/5628
dc.language.isoenen_US
dc.publisherNatureen_US
dc.titlePreferential localized thinning of lithospheric mantle in the melt-poor Malawi Riften_US
dc.typeJournal Article, Peer Revieweden_US
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