Structure of the upper crust at the axis segmentation stage of rift evolution as revealed by gravity data: Case study of the Gedemsa magmatic segment, Main Ethiopian Rift

Nigussie, Wubamlak; Alemu, Abera; Kevin, Mickus; Muluneh, Ameha

doi:10.1016/j.jafrearsci.2022.104523

Cited by 8 publications

(10 citation statements)

References 36 publications

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“…The magmatic segments (Figure 4) are associated with one or more Quaternary rift volcanoes. The Gedemsa magmatic segment is associated with five rift volcanoes (Bora, Bericha, Tulu Moye, Gedemsa, and Boku) (Ebinger and Casey, 2001;Nigussie et al, 2022a). The rift margin volcanic zones identified in our study are the SDFZ and YVTL on the western rift flank and Frontiers in Earth Science frontiersin.org the Galema range on the southeastern rift flank, characterized by elongated gravity maxima.…”

Section: High Pass Filtered Gravity Anomaliesmentioning

confidence: 65%

Subsurface structure of magmatic segments during continental breakup: Perspectives from a gravity data analysis along the Main Ethiopian Rift

et al. 2023

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In magma-rich continental rifts, extension is commonly localized as dike injection in discrete magmatic segments which appear from surface geology to mimic the along-axis segmentation of ocean ridges. However, the subsurface morphology of these zones of localized magma injection is unclear, and whether and at what depth range they remain with discrete subvolcanic plumbing systems is not fully understood. In addition, the relationship between zones of magma injection and tectonic faulting is also debated. The Main Ethiopian Rift (MER) provides a unique opportunity to examine the spatial scale, locus, and subsurface geometries of magmatic localization in active continental rifts. We examined spatial variations in the structure of the crust in the MER using gravity data to better understand the subsurface pattern of magma injection. Results of our study reveal discrete Bouguer gravity highs in the centers of the distinct right-stepping magmatic segments of the MER (Aluto, Gedemsa, and Boseti), and interpreted as the locus of mafic intrusions. The gravity data show that the boundary between each magmatic segment is observed down to depths of ∼20 km, suggesting that magmatic segments have discrete subvolcanic plumbing systems at least down to the mid-crust. Additionally, incorporating the fault network shows that the densest faulting occurs at the tips of the zones of densest magma injection shown by Bouguer gravity highs. This is similar to the axial segmentation observed at slow and ultra-slow spreading ridges and suggests strong along-axis variations in deformation mechanism, with magma injection accommodating extension at the segment centers and faulting dominating towards the segment ends. In addition, rift margin volcanic zones (Siltie Debrezeit, Yerer Tulu, and Galema) are also inferred from bandpass gravity anomaly maps, supported by petrologic evidence, which implies that extension by dike injection has also occurred near the rift flanks.

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Section: High Pass Filtered Gravity Anomaliesmentioning

confidence: 65%

Subsurface structure of magmatic segments during continental breakup: Perspectives from a gravity data analysis along the Main Ethiopian Rift

et al. 2023

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“…Our samples are scoriae from the Quaternary basaltic cone field located in the Gedemsa magmatic segment of the MER adjacent to the Boku Volcanic Complex (Figure 1; Tadesse et al., 2019; Nigussie, Alemu, et al., 2023). Littering the remnants of the collapsed ∼500 ka Boku caldera, the later‐stage ∼200 ka basaltic cones and fissure flows are associated with seismic anomalies (e.g., Keranen et al., 2004), gravity anomalies (e.g., Nigussie et al., 2022; Nigussie, Mickus, et al., 2023), and rift‐aligned faults characteristic of MER magmatic segments (e.g., Rooney et al., 2011). Quarries provide access into the interiors of cones, where fresh glassy basaltic scoria can be sampled.…”

Section: Methodsmentioning

confidence: 99%

“…Low seismic moment earthquakes in northern MER magmatic segments are distributed within a narrow depth band between 8 and 16 km and have been interpreted as being triggered by movement or emplacement of mid-crustal melts (Daly et al, 2008;Keir et al, 2006). High-Vp, high-Vp/Vs and high-density bodies are inferred to be present at these depths under Boku and other MER segments (Cornwell et al, 2006;Daly et al, 2008;Keranen et al, 2004;Nigussie et al, 2022), as are high-conductivity crustal anomalies (Whaler & Hautot, 2006), all indicative of partially molten mid-crustal intrusions. Our results are also in good agreement with empirical observations relating MER cone clustering to intrusion depths (Mazzarini et al, 2013).…”

Section: Basaltic Melt Focusing In the Main Ethiopian Riftmentioning

confidence: 97%

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

Wong

Ferguson

Wieser

et al. 2023

Geophysical Research Letters

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“…To obtain better quantitative subsurface information, we reinterpreted the 2D gravity (Figure 11) and 3D geologic (Figure 12) models from Nigussie et al (2022a) in terms of subsurface volcanic networks and their link to the geothermal resource occurrences. The 2D model was constructed by forward modeling of the gravity data (Figure 11).…”

Section: Quantitative Interpretationmentioning

confidence: 99%

“…Low-frequency earthquakes occur at a depth and location coincident with the low resistivity anomaly beneath TM volcano and are therefore interpreted to be caused by melt motion (Greenfield et al, 2019). Despite several surface (Fontijn et al, 2018;Guծbrandsson et al, 2020;Kebede et al, 2023;Tadesse et al, 2023) and subsurface (e.g., Keranen et al, 2004;Maguire et al, 2006;Mickus et al, 2007;Cornwell et al, 2010;Samrock et al, 2018;Darge et al, 2019;Greenfield et al, 2019;Nigussie et al, 2022a;Nigussie et al, 2022b;Nigussie et al, 2023) studies on the structural setting and hydrothermal fluids of the area, the role of shallow subsurface structures on the occurrence of geothermal resources is not fully understood within the study area.…”

Section: Introductionmentioning

confidence: 99%

Subsurface structural control of geothermal resources in a magmatic rift: gravity and magnetic study of the Tulu Moye geothermal prospect, Main Ethiopian Rift

et al. 2023

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Since the Quaternary, extension and magmatism in the Main Ethiopian Rift (MER) have been mainly focused into narrow magmatic segments that have numerous volcanic centers and caldera collapses that offer favorable conditions for the occurrence of geothermal resources. However, the subsurface structure of the volcanic systems (0–10 km) and their link to the distribution of shallow geothermal resources remain unclear. To investigate the role of subsurface structures on the occurrence of these resources, we conducted gravity and magnetic studies combined with geological constraints within the Tulu Moye Geothermal Prospect (TMGP), one of the current geothermal prospects in the central MER associated with caldera collapses. Gravity data from the Global Gravity Model plus (GGMplus 2013) and ground magnetic data transformed into residual and derivative maps reveal that shallow magmatic intrusions occur under the volcanic centers (Tulu Moye, Bora, and Bericha). Our interpretation along with recent magnetotelluric model suggests that only the intrusion beneath Tulu Moye is currently magmatically active and includes partial melt, consistent with it being a primary heat source for the geothermal system. A new caldera formation model is proposed where the TMGP hosts an older large caldera (about 25 km diameter) within which there are several smaller nested caldera systems associated with the Bora, Bericha, and Tulu Moye volcanoes. Along with existing geologic, seismic, and magnetotelluric studies, our gravity and magnetic analysis indicate the interaction between NNE-SSW (rift-parallel) and NW-SE (cross-rift) trending faults, along with shallow magmatic intrusions and caldera systems, suggesting that such a large geothermal system is possible under these conditions.

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Structure of the upper crust at the axis segmentation stage of rift evolution as revealed by gravity data: Case study of the Gedemsa magmatic segment, Main Ethiopian Rift

Cited by 8 publications

References 36 publications

Subsurface structure of magmatic segments during continental breakup: Perspectives from a gravity data analysis along the Main Ethiopian Rift

Subsurface structure of magmatic segments during continental breakup: Perspectives from a gravity data analysis along the Main Ethiopian Rift

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

Subsurface structural control of geothermal resources in a magmatic rift: gravity and magnetic study of the Tulu Moye geothermal prospect, Main Ethiopian Rift

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