(Garnet)-spinel peridotite xenoliths from Mega (Ethiopia): Evidence for rejuvenation and dynamic thinning of the lithosphere beneath the southern Main Ethiopian Rift

Casagli, Alessio; Frezzotti, Maria Luce; Peccerillo, Angelo; Tiepolo, Massimo; Astis, G. De

doi:10.1016/j.chemgeo.2016.11.001

Cited by 24 publications

(13 citation statements)

References 150 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Melting of easily fusible metasomes in the subcontinental lithospheric mantle (SCLM) has been posited as a key process in melt generation and strain localization within rifts (e.g., Rooney et al, ). Recent studies suggest abundant refertilization of the SCLM in southern and central Ethiopia by carbonate‐rich, hydrous metasomatic agents (Casagli et al, ; Rooney et al, ; Trestrail et al, ). Carbon stored in metasomatized mantle could represent a significant additional source for CO 2 degassing.…”

Section: Discussionmentioning

confidence: 99%

Spatially Variable CO₂ Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

Hunt

Zafu

Mather

et al. 2017

Geochem Geophys Geosyst

View full text Add to dashboard Cite

Deep carbon emissions from historically inactive volcanoes, hydrothermal, and tectonic structures are among the greatest unknowns in the long‐term (∼Myr) carbon cycle. Recent estimates of diffuse CO2 flux from the Eastern Rift of the East African Rift System (EARS) suggest this could equal emissions from the entire mid‐ocean ridge system. We report new CO2 surveys from the Main Ethiopian Rift (MER, northernmost EARS), and reassess the rift‐related CO2 flux. Since degassing in the MER is concentrated in discrete areas of volcanic and off‐edifice activity, characterization of such areas is important for extrapolation to a rift‐scale budget. Locations of hot springs and fumaroles along the rift show numerous geothermal areas away from volcanic edifices. With these new data, we estimate total CO2 emissions from the central and northern MER as 0.52–4.36 Mt yr−1. Our extrapolated flux from the Eastern Rift is 3.9–32.7 Mt yr−1 CO2, overlapping with lower end of the range presented in recent estimates. By scaling, we suggest that 6–18 Mt yr−1 CO2 flux can be accounted for by magmatic extension, which implies an important role for volatile‐enriched lithosphere, crustal assimilation, and/or additional magmatic intrusion to account for the upper range of flux estimates. Our results also have implications for the nature of volcanism in the MER. Many geothermal areas are found >10 km from the nearest volcanic center, suggesting ongoing hazards associated with regional volcanism.

show abstract

Section: Discussionmentioning

confidence: 99%

Spatially Variable CO₂ Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

Hunt

Zafu

Mather

et al. 2017

Geochem Geophys Geosyst

View full text Add to dashboard Cite

show abstract

“…Although detailed analyses were not performed on these nodules, their mineralogical and isotopic composition has been the subject of detailed previous works (e.g. Conticelli et al, 1999;Orlando et al, 2006;Casagli et al, 2017;Alemayehu et al, 2016Alemayehu et al, , 2017 and suggests an upper mantle provenance for this material. The abundance of these dense, mantle-derived xenoliths is suggestive of high magma ascent rates (> 0.5 ms -1 for a xenolith of 15 cm radius in a mafic magma; Spera, 1980), implying the lack of important intermediate reservoirs or stalling zones in which nodules would have sunk during the alkaline, more recent phase of activity in the two VFs.…”

Section: Rates Of Volcanismmentioning

confidence: 98%

Recent volcano-tectonic activity of the Ririba rift and the evolution of rifting in South Ethiopia

Franceschini

Cioni

Scaillet

et al. 2020

Journal of Volcanology and Geothermal Research

View full text Add to dashboard Cite

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

show abstract

“…The composition of former garnets can be reconstructed from the well‐preserved spinel‐pyroxene symplectites using the methods (see supporting information) described by Takahashi () and Casagli et al (). One well‐preserved symplectite in sample PL14C5 yields an ideal garnet composition approaching that of typical mantle garnets (moles of O = 12, Si = 2.99, Al + Cr = 2.02; supporting information, Table S6; Wood et al, ).…”

Section: Analytical Resultsmentioning

confidence: 99%

“…Spinel-pyroxene symplectites within upper-mantle tectonites and xenoliths are commonly interpreted as pseudomorphs of former garnet (Casagli et al, 2017;Morishita & Arai, 2003;Smith, 1977). However, alternative origins have been proposed (see summary in supporting information), including exsolution from Al-rich orthopyroxene (Basu & MacGregor, 1975), mineral unmixing and migration from nonstoichiometric Ca-Al-Cr rich clinopyroxene (Field & Haggerty, 1994), and precipitation from percolated and/or reacted melts (Suhr et al, 2008).…”

Section: Origin Of Symplectites and Host Lherzolitesmentioning

confidence: 99%

“Garnet” Lherzolites in the Purang Ophiolite, Tibet: Evidence for Exhumation of Deep Oceanic Lithospheric Mantle

Gong

Shi

et al. 2020

Geophysical Research Letters

View full text Add to dashboard Cite

Ophiolites commonly sample the uppermost parts (15–20 km) of fossil oceanic lithosphere. However, in recent years, the documentation of diamonds, super‐reducing (e.g., SiC), and other “unusual” minerals from several ophiolitic peridotites and chromitites (e.g., Tibet and the Polar Urals) has caused debate concerning their origin (i.e., deep vs. shallower upper mantle). Here we report on symplectite‐bearing lherzolites from the Purang ophiolite in Tibet, which preserve the first compelling evidence of garnet‐facies protoliths. These lherzolites were previously formed and stabilized at a depth of ~85–100 km, which is much deeper than generally suggested and approaches the depth (~120 km) required for stabilizing the diamonds. Combining with other key observations, we suggest the Purang garnet‐bearing peridotites may represent mixtures of oceanic lithosphere domains with diverse origins; they were rapidly exhumed at a variety of mantle depths within a subduction channel associated with oceanic slab retreat.

show abstract

(Garnet)-spinel peridotite xenoliths from Mega (Ethiopia): Evidence for rejuvenation and dynamic thinning of the lithosphere beneath the southern Main Ethiopian Rift

Cited by 24 publications

References 150 publications

Spatially Variable CO₂ Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

Spatially Variable CO₂ Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

Recent volcano-tectonic activity of the Ririba rift and the evolution of rifting in South Ethiopia

“Garnet” Lherzolites in the Purang Ophiolite, Tibet: Evidence for Exhumation of Deep Oceanic Lithospheric Mantle

Contact Info

Product

Resources

About

(Garnet)-spinel peridotite xenoliths from Mega (Ethiopia): Evidence for rejuvenation and dynamic thinning of the lithosphere beneath the southern Main Ethiopian Rift

Cited by 24 publications

References 150 publications

Spatially Variable CO2 Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

Spatially Variable CO2 Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

Recent volcano-tectonic activity of the Ririba rift and the evolution of rifting in South Ethiopia

“Garnet” Lherzolites in the Purang Ophiolite, Tibet: Evidence for Exhumation of Deep Oceanic Lithospheric Mantle

Contact Info

Product

Resources

About

Spatially Variable CO₂ Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

Spatially Variable CO₂ Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions