Focused Mid‐Crustal Magma Intrusion During Continental Break‐Up in Ethiopia

Abstract

Continental rifting involves the rupture of strong continental lithosphere to form new ocean basins. Evidence from active continental rifts and passive margins suggests that continental break-up often involves intrusion of substantial volumes of magma into the rifting crust (e.g.,

Determining the Pressure – Temperature – Composition (P-T-X) conditions of magma storage

“…Figure 19 -Percent of the total melt inclusion CO 2 content held in the vapour bubbles from studies which have used an instrument-specific Raman calibration. Refs: Allison et al, 2021;Aster et al, 2016;DeVitre et al, 2023a;Hanyu et al, 2020;Hernandez Nava et al, 2021;Moore et al, 2021Moore et al, , 2018Moore et al, , 2015Wong et al, 2023. Raman spectroscopic analyses of CO 2 in vapour bubbles rely on the strong correlation between the density of CO 2 and the distance between the two strong CO 2 spectral peaks collectively termed the Fermi diad. This distance is commonly called the splitting, diad splitting, or diad separation (Δ, Fig.…”

“…The CO 2 density in these capsules was calculated from the mass of loaded CO 2 and the volume of the capillary, which allowed the calibration line to be determined at low densities (FSCCs ranged from 0.008-0.133 g/cm 3 ). Wieser et al (2021) calibrated their Raman at low densities using 19 synthetic fluid inclusions (SFI) in quartz standards (0.04-0.14 g/cm 3 ) which were measured on the calibrated Virginia Tech Raman, with the same calibration being used by Wong et al (2023). Mironov et al (2020) use a similar approach, developing a calibration line using 8 melt inclusion vapour bubbles measured at Virginia Tech with densities between 0.013-0.22 g/cm 3 .…”

“…Even with a room T of 25°C, many of the densities reported by uncalibrated studies are thermodynamically impossible. Refs: (Allison et al, 2021;Bali et al, 2018;Hartley et al, 2014;Moore et al, 2018Moore et al, , 2015Robidoux et al, 2018;Taracsák et al, 2019;Venugopal et al, 2020;Wieser et al, 2021;Wong et al, 2023).…”

Stratigraphy and eruptive history of Gedemsa caldera volcano, Central Main Ethiopian Rift

“…Previously, geophysical studies in the region (e.g in Boset, Northern MER) revealed the presence of crustal melt zones and seismicity, suggesting ongoing magmatic processes influencing the tectonic activity (Whaler and Hautot, 2006;Keir et al, 2009a;Bastow et al, 2010). In congruence with the geophysical studies, recent data from field and petrological investigations indicate that the intrusions in the MER are assisting the rift evolution by creating a mechanically weak crustal lithosphere (Nicotra et al, 2021;Chiasera et al, 2021;Oliveira et al, 2022;Wong et al, 2023). Similarly, evidence of repeated volcanic eruptions within the MER show that the onset and evolution of the MER have been heavily facilitated by the presence of melts within the crust.…”