A tale of two domes: Neogene to recent volcanism and dynamic uplift of northeast Brazil and southwest Africa
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
Topographic domes that are distant from active plate boundaries are often characterised by rapid, youthful uplift, contemporaneous mafic volcanism, radial drainage patterns, and positive long-wavelength gravity anomalies. There is increasing evidence that they are underlain by anomalously low sub-plate seismic velocities. Despite their well-known geomorphological expression, the origin of these epeirogenic features remains enigmatic and is much debated. Here, we investigate potential mechanisms for rapid regional uplift by combining disparate observations from the Borborema and Angolan plateaux that straddle the Brazilian and southwest African margins, respectively. Oceanic residual depth measurements, drainage analysis, stratigraphic architecture, emergent marine terraces and basement denudation are used to constrain their regional uplift histories. In both cases, the bulk of topographic growth occurred within the last 30 Ma in the absence of significant tectonic deformation. We estimate present-day mantle temperature and lithospheric thickness from Neogene to recent volcanic trace element compositions and upper mantle shear wave velocities. Volcanic geochemistry in northeast Brazil is compatible with decompression melting of warm asthenosphere and potentially a minor contribution from metasomatised lithospheric mantle. In Angola, melting of metasomatised lithosphere is probably triggered by injection of small-degree asthenospheric-derived melts. We find no evidence for an asthenospheric thermal anomaly >50 °C above ambient beneath either region. Present-day lithospheric thickness is ∼100 km beneath Angola and could be as thin as 60 km in the Borborema Province. For Angola, thermobarometry on mantle xenocrysts from Cretaceous kimberlites is used to estimate palaeogeothermal gradients. Results indicate a pre-existing gradient in lithospheric thickness between the edge of the Congo craton and the centre of the Angolan dome at ∼120 Ma. This gradient likely steepened as a result of additional Neogene thinning by km beneath the centre of the dome. We conclude that the mechanism for Neogene epeirogenic uplift of the Borborema and Angolan domes is the introduction of a small positive temperature anomaly into the asthenosphere that causes thermomechanical thinning of the overlying lithospheric mantle.
Date Issued
2020-10-01
Date Acceptance
2020-07-05
Citation
Earth and Planetary Science Letters, 2020, 547, pp.1-13
ISSN
0012-821X
Publisher
Elsevier BV
Start Page
1
End Page
13
Journal / Book Title
Earth and Planetary Science Letters
Volume
547
Copyright Statement
© 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor
Imperial College London
Schmidt Science Fellows
Identifier
https://www.sciencedirect.com/science/article/pii/S0012821X20304088?via%3Dihub
Subjects
Science & Technology
Physical Sciences
Geochemistry & Geophysics
dynamic topography
landscape evolution
intraplate magmatism
xenolith thermobarometry
asthenospheric temperature
lithospheric structure
FERNANDO-DE-NORONHA
PERIDOTITE XENOLITHS
UPPER-MANTLE
BORBOREMA PROVINCE
LITHOSPHERE
GEOCHEMISTRY
GEOCHRONOLOGY
TOPOGRAPHY
PETROLOGY
ATLANTIC
Geochemistry & Geophysics
02 Physical Sciences
04 Earth Sciences
Publication Status
Published online
Article Number
116464
Date Publish Online
2020-07-23