Universität zu Köln

Ball, P. W., White, N. J., Masoud, A., Nixon, S., Hoggard, M. J., Maclennan, J., Stuart, F. M., Oppenheimer, C. and Kroepelin, S. (2019). Quantifying Asthenospheric and Lithospheric Controls on Mafic Magmatism Across North Africa. Geochem. Geophys. Geosyst., 20 (7). S. 3520 - 3556. WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 1525-2027

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Abstract

African basin-and-swell morphology is often attributed to the planform of subplate mantle convection. Across North Africa, the coincidence of Neogene and Quaternary (i.e., <23Ma) magmatism, topographic swells, long wavelength gravity anomalies, and slow shear wave velocity anomalies within the asthenosphere provides observational constraints for this hypothesis. Admittance analysis of topographic and gravity fields corroborates the existence of subplate support. To investigate quantitative relationships between intraplate magmatism, shear wave velocity, and asthenospheric temperature, we collected and analyzed a suite of 224 lava samples from Tibesti, Jabal Eghei, Haruj, Sawda/Hasawinah, and Gharyan volcanic centers of Libya and Chad. Forward and inverse modeling of major, trace, and rare Earth elements was used for thermobarometric studies and to determine melt fraction as a function of depth. At each center, mafic magmatism is modeled by assuming adiabatic decompression of dry peridotite with asthenospheric potential temperatures of 1300-1360 degrees C. Surprisingly, the highest temperatures are associated with the low-lying Haruj volcanic center rather than with the more prominent Tibesti swell. Our results are consistent with earthquake tomographic models which show that the slowest shear wave anomalies within the upper mantle occur directly beneath the Haruj center. This inference is corroborated by converting observed velocities into potential temperatures, which are in good agreement with those determined by geochemical inverse modeling. Our results suggest that North African volcanic swells are primarily generated by thermal anomalies located beneath thinned lithosphere.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Ball, P. W. UNSPECIFIED UNSPECIFIED UNSPECIFIED White, N. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Masoud, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Nixon, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hoggard, M. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Maclennan, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Stuart, F. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Oppenheimer, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kroepelin, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-135947
DOI:	10.1029/2019GC008303
Journal or Publication Title:	Geochem. Geophys. Geosyst.
Volume:	20
Number:	7
Page Range:	S. 3520 - 3556
Date:	2019
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	1525-2027
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language CENOZOIC VOLCANIC AREAS; GRAVITY-FIELD MODEL; SHEAR-WAVE VELOCITY; THERMAL STRUCTURE; TRACE-ELEMENTS; GEOCHEMICAL EVIDENCE; TIBESTI MASSIF; MANTLE PLUMES; ARC BASALTS; SIRT BASIN Multiple languages Geochemistry & Geophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/13594