Vol.:(0123456789) 1 3 Contributions to Mineralogy and Petrology (2018) 173:37 https://doi.org/10.1007/s00410-018-1460-7 ORIGINAL PAPER From initiation to termination: a petrostratigraphic tour of the Ethiopian Low-Ti Flood Basalt Province S. R. Krans 1  · T. O. Rooney 1  · J. Kappelman 2  · G. Yirgu 3  · D. Ayalew 3 Received: 14 September 2017 / Accepted: 28 March 2018 / Published online: 19 April 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Continental food basalts (CFBs), thought to preserve the magmatic record of an impinging mantle plume head, ofer spatial and temporal insights into melt generation processes in large igneous provinces (LIPs). Despite the utility of CFBs in probing mantle plume composition, these basalts typically erupt fractionated compositions, suggestive of signifcant residence time in the continental lithosphere. The location and duration of residence within the lithosphere provide additional insights into the fux of plume-related magmas. The NW Ethiopian plateau ofers a well-preserved stratigraphic sequence from food basalt initiation to termination, and is thus an important target for study of CFBs. This study examines modal observations within a stratigraphic framework and places these observations within the context of the magmatic evolution of the Ethiopian CFB province. Data demonstrate multiple pulses of magma recharge punctuated by brief shut-down events, with initial fows fed by magmas that experienced deeper fractionation (lower crust). Broad changes in modal mineralogy and fow cyclicity are consistent with fuctuating changes in magmatic fux through a complex plumbing system, indicating pulsed magma fux and an overall shallowing of the magmatic plumbing system over time. The composition of plagioclase megacrysts suggests a constant replenishing of new primitive magma recharging the shallow plumbing system during the main phase of volcan- ism, reaching an apex prior to food basalt termination. The petrostratigraphic data sets presented in this paper provide new insight into the evolution of a magma plumbing system in a CFB province. Keywords Flood basalt · Ethiopia · Stratigraphy · Petrography · Cumulophyric · Megacrystic plagioclase · Magma plumbing system Introduction The most signifcant manifestation of the interaction between an upwelling thermo-chemical anomaly and the continental lithosphere is the formation of a continental food basalt (CFB) province (Ernst 2014). CFBs are voluminous out- pourings of dominantly basaltic lava (> 100,000 km 2 area, ≥ 1-km thick) that erupt over geologically short-time inter- vals (1–5 Ma, with the greatest volume erupted over ~ 1 Ma) (Self et al. 1997; Jerram and Widdowson 2005). Much focus has been placed on constraining the intensive and extensive parameters of melt generation associated with upwelling plumes (Kogiso et al. 2003; Davaille et al. 2005; Herzberg and Asimow 2008; Kimura and Kawabata 2015). However, lavas erupted in CFBs are rarely primary, and exhibit geo- chemical evidence of extended residence time in the conti- nental crust (Cox 1980; Villiger et al. 2004). It is thus appar- ent that CFB lavas, which are preserved as well-constrained temporal sequences, reveal insights into the development of the magmatic plumbing system of a large igneous province (LIP), and by extension, the mechanisms of plume–litho- sphere interaction. Constraints as to the processes active within the plumbing system of CFBs have relied upon the extensive geochemical Communicated by Mark S Ghiorso. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00410-018-1460-7) contains supplementary material, which is available to authorized users. * S. R. Krans kranssus@msu.edu 1 Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI 48824, USA 2 Department of Anthropology and Department of Geological Sciences, University of Texas, Austin, TX 78712, USA 3 Department of Earth Sciences, Addis Ababa University, Addis Ababa, Ethiopia