Controls on the magmatic fraction of extension at mid-ocean ridges

Olive, Jean‐Arthur; Dublanchet, Pierre

doi:10.1016/j.epsl.2020.116541

Cited by 46 publications

(55 citation statements)

References 59 publications

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“…If the eruption interval of 18 years is uniform across all three segments, then 50%–75% of plate spreading would need to be accommodated by faulting at segments 4–5 and 6–7 in order to make up for the inferred deficit in spreading accommodated by dike intrusion. Although such a high degree of fault‐accommodated spreading is unlikely in such a high magma‐supply and spreading rate ridge segment (e.g., Buck et al., 2005; Olive & Dublanchet, 2020), faulting may play a role when considered over multiple eruptive cycles, although earthquake data to test this idea are not yet available. A more likely explanation is that over longer time scales than the ∼30 years of observations at the EPR 9°50′N system, magmatic events occur episodically (i.e., at irregular time intervals), and that magmatic episode time interval varies between segments.…”

Section: Discussionmentioning

confidence: 99%

Extent and Volume of Lava Flows Erupted at 9°50′N, East Pacific Rise in 2005–2006 From Autonomous Underwater Vehicle Surveys

Parnell‐Turner

Fornari

et al. 2022

Geochem Geophys Geosyst

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Seafloor volcanic eruptions are difficult to directly observe due to lengthy eruption cycles and the remote location of mid‐ocean ridges. Volcanic eruptions in 2005–2006 at 9°50′N on the East Pacific Rise have been well documented, but the lava volume and flow extent remain uncertain because of the limited near‐bottom bathymetric data. We present near‐bottom data collected during 19 autonomous underwater vehicle (AUV) Sentry dives at 9°50′N in 2018, 2019, and 2021. The resulting 1 m‐resolution bathymetric grid and 20 cm‐resolution sidescan sonar images cover 115 km2, and span the entire area of the 2005–2006 eruptions, including an 8 km2 pre‐eruption survey collected with AUV ABE in 2001. Pre‐ and post‐eruption surveys, combined with sidescan sonar images and seismo‐acoustic impulsive events recorded during the eruptions, are used to quantify the lava flow extent and to estimate changes in seafloor depth caused by lava emplacement. During the 2005–2006 eruptions, lava flowed up to ∼3 km away from the axial summit trough, covering an area of ∼20.8 km2; ∼50% larger than previously thought. Where pre‐ and post‐eruption surveys overlap, individual flow lobes can be resolved, confirming that lava thickness varies from ∼1 to 10 m, and increases with distance from eruptive fissures. The resulting lava volume estimate indicates that ∼57% of the melt extracted from the axial melt lens probably remained in the subsurface as dikes. These observations provide insights into recharge cycles in the subsurface magma system, and are a baseline for studying future eruptions at the 9°50′N area.

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Section: Discussionmentioning

confidence: 99%

Extent and Volume of Lava Flows Erupted at 9°50′N, East Pacific Rise in 2005–2006 From Autonomous Underwater Vehicle Surveys

Parnell‐Turner

Fornari

et al. 2022

Geochem Geophys Geosyst

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“…Across the OSC, <23% of the extension is clearly shown to be accommodated by magmatic intrusion (along the SRZ). This indicate that the OSC is 2-3 times more tectonic-accommodated extension than expected based on the longer timescale average suggested by the ratio of magmatic extension (M) at intermediate-spreading rate ridges which ranges from 0.7 to 0.95 Olive & Dublanchet, 2020). Such variations likely result from temporal variations in volcanic and tectonic activity and therefore in the underlying plumbing system.…”

Section: Asymmetry Of the Extension And Short-term Extension Ratementioning

confidence: 72%

Faulting and Magmatic Accretion Across the Overlapping Spreading Center Between Vance Segment and Axial South Rift, Juan de Fuca Ridge

Saout

Clague

Paduan

2022

Geochem Geophys Geosyst

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Plate divergence along mid-oceans ridges is accommodated through faulting and magmatic accretion (e.g., Bohnenstiehl & Carbotte, 2001;Cowie et al., 1993;Escartín et al., 2007). Studies have shown that the long-term proportion of tectonic versus magmatic extension is highly variable and sensitive to spreading rate (Buck et al., 1998), with the ratio of magmatic accretion over faulting higher along fast-spreading ridges (

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“…The resulting seafloor morphology is the so-called smooth seafloor 4 , with extensive exposure of mantle-derived peridotites and only patches of hummocky basalts 2 . This newly-discovered seafloor spreading mode differs from the "classic" detachment-volcanic and volcanicvolcanic modes at slow spreading ridges and at more magmatically-robust portions of ultraslow spreading ridges, where at least one plate is dominated by abyssal-hill volcanic seafloor [4][5][6][7][8][9][10] .…”

mentioning

confidence: 68%

Microseismicity and lithosphere thickness at a nearly amagmatic mid-ocean ridge

Chen

Crawford

Cannat³

2021

Preprint

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Successive flip-flop detachment faults in a nearly-amagmatic region of the ultraslow-spreading Southwest Indian Ridge (SWIR) at 64°30'E accommodate ~100% of plate divergence, with mostly ultramafic seafloor. As magma is the main heat carrier to the oceanic lithosphere, the nearly-amagmatic SWIR 64°30'E is expected to have a very thick lithosphere. Here, our microseismicity data shows a 15-km thick seismogenic lithosphere, actually thinner than the more magmatic SWIR Dragon Flag detachment with the same spreading rate. This challenges current models of how spreading rate and melt supply control the thermal regime of mid-ocean ridges. Microearthquakes with normal focal mechanisms are colocated with seismically imaged damage zones of the detachment and reveal hanging-wall normal faulting, which is not seen at more magmatic detachments at the SWIR or the Mid-Atlantic Ridge. We also document a two-day seismic swarm, interpret as caused by an upward-migrating melt intrusion in the detachment footwall (6-11 km), triggering a sequence of shallower (~1.5 km) tectonic earthquakes in the detachment fault plane. This points to a possible link between sparse magmatism and tectonic failure at melt-poor ultraslow ridges.

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Controls on the magmatic fraction of extension at mid-ocean ridges

Cited by 46 publications

References 59 publications

Extent and Volume of Lava Flows Erupted at 9°50′N, East Pacific Rise in 2005–2006 From Autonomous Underwater Vehicle Surveys

Extent and Volume of Lava Flows Erupted at 9°50′N, East Pacific Rise in 2005–2006 From Autonomous Underwater Vehicle Surveys

Faulting and Magmatic Accretion Across the Overlapping Spreading Center Between Vance Segment and Axial South Rift, Juan de Fuca Ridge

Microseismicity and lithosphere thickness at a nearly amagmatic mid-ocean ridge

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