TY - JOUR
T1 - Geochemistry of Woranso–Mille Pliocene basalts from west-central Afar, Ethiopia
T2 - Implications for mantle source characteristics and rift evolution
AU - Alene, Mulugeta
AU - Hart, William K.
AU - Saylor, Beverly Z.
AU - Deino, Alan
AU - Mertzman, Stanley
AU - Haile-Selassie, Yohannes
AU - Gibert, Luis B.
N1 - Funding Information:
This work has been supported by the National Science Foundation grant number BCS 1124716 to Beverly Saylor. M. Alene gratefully acknowledges support for this work from the Fulbright Senior Research Scholars grant. W.K. Hart acknowledges financial support from the Janet & Elliot Baines Professorship and the assistance of Dr. John Morton and David Kuentz in the acquisition of the ICP-MS trace element and TIMS isotope data, respectively. Mertzman thanks Karen R. Mertzman for her ongoing meticulous work in the X-ray lab without which there would be much less high quality data in the world. NSF-EAR 0923224 awarded to Franklin and Marshall College facilitated a substantial upgrade of the X-ray laboratory.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/6/1
Y1 - 2017/6/1
N2 - The Woranso–Mille (WORMIL) area in the west-central Afar, Ethiopia, contains several Pliocene basalt flows, tuffs, and fossiliferous volcaniclastic beds. We present whole-rock major- and trace-element data including REE, and Sr–Nd–Pb isotope ratios from these basalts to characterize the geochemistry, constrain petrogenetic processes, and infer mantle sources. Six basalt groups are distinguished stratigraphically and geochemically within the interval from ~ 3.8 to ~ 3 Ma. The elemental and isotopic data show intra- and inter-group variations derived primarily from source heterogeneity and polybaric crystallization ± crustal inputs. The combined Sr–Nd–Pb isotope data indicate the involvement of three main reservoirs: the Afar plume, depleted mantle, and enriched continental lithosphere (mantle ± crust). Trace element patterns and ratios further indicate the basalts were generated from spinel-dominated shallow melting, consistent with significantly thinned Pliocene lithosphere in western Afar. The on-land continuation of the Aden rift into western Afar during the Pliocene is reexamined in the context of the new geochemistry and age constraints of the WORMIL basalts. The new data reinforce previous interpretations that progressive rifting and transformation of the continental lithosphere to oceanic lithosphere allows for increasing asthenospheric inputs through time as the continental lithosphere is thinned.
AB - The Woranso–Mille (WORMIL) area in the west-central Afar, Ethiopia, contains several Pliocene basalt flows, tuffs, and fossiliferous volcaniclastic beds. We present whole-rock major- and trace-element data including REE, and Sr–Nd–Pb isotope ratios from these basalts to characterize the geochemistry, constrain petrogenetic processes, and infer mantle sources. Six basalt groups are distinguished stratigraphically and geochemically within the interval from ~ 3.8 to ~ 3 Ma. The elemental and isotopic data show intra- and inter-group variations derived primarily from source heterogeneity and polybaric crystallization ± crustal inputs. The combined Sr–Nd–Pb isotope data indicate the involvement of three main reservoirs: the Afar plume, depleted mantle, and enriched continental lithosphere (mantle ± crust). Trace element patterns and ratios further indicate the basalts were generated from spinel-dominated shallow melting, consistent with significantly thinned Pliocene lithosphere in western Afar. The on-land continuation of the Aden rift into western Afar during the Pliocene is reexamined in the context of the new geochemistry and age constraints of the WORMIL basalts. The new data reinforce previous interpretations that progressive rifting and transformation of the continental lithosphere to oceanic lithosphere allows for increasing asthenospheric inputs through time as the continental lithosphere is thinned.
KW - Afar rift
KW - Basalt
KW - Geochemistry
KW - Lithosphere
KW - Mantle Plume
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U2 - 10.1016/j.lithos.2017.03.005
DO - 10.1016/j.lithos.2017.03.005
M3 - Article
AN - SCOPUS:85016452597
SN - 0024-4937
VL - 282-283
SP - 187
EP - 200
JO - LITHOS
JF - LITHOS
ER -