Formation of Igneous Layering in the Lower Oceanic Crust From the Samail Ophiolite, Sultanate of Oman

Mock, Dominik; Neave, David A.; Müller, Samuel; Garbe‐Schönberg, Dieter; Namur, Olivier; Ildefonse, Benoı̂t; Koepke, Jürgen

doi:10.1029/2020jb019573

Cited by 18 publications

(33 citation statements)

References 121 publications

(190 reference statements)

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“…The observed features are very similar to those in the layered gabbros described by Mock et al. (2020) in Wadi Somerah (Sumail block); they suggested as a formation mechanism that the layers were deposited by density currents of crystal‐laden magma within a sill environment. Much more abundant within the Layered Gabbro Unit are gabbros showing cryptic layering, where the establishment of a stratiform layering is not visible.…”

Section: Resultssupporting

confidence: 84%

A Reference Section Through Fast‐Spread Lower Oceanic Crust, Wadi Gideah, Samail Ophiolite (Sultanate of Oman): Petrography and Petrology

et al. 2022

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In the absence of a complete profile through fast‐spreading modern oceanic crust, we established a reference profile through the whole paleo crust of the Samail ophiolite (Sultanate of Oman), which is regarded as the best analogue for fast‐spreading oceanic crust on land. To establish a coherent data set, we sampled the Wadi Gideah in the Wadi‐Tayin massif from the mantle section up to the sheeted dikes and performed different analytical and structural investigations on the same suite of samples. This paper reports our studies of the lower crust, a 5 km thick pile of gabbros, focusing on petrographic features and on the results of mineral analyses. Depth profiles of mineral compositions combined with petrological modeling reveal insights into the mode of magmatic formation of fast‐spreading lower oceanic crust, implying a hybrid accretion mechanism. The lower two thirds of the crust, mainly consisting of layered gabbros, formed via the injection of melt sills and in situ crystallization. Here, upward moving fractionated melts mixed with more primitive melts through melt replenishments, resulting in a slight but distinct upward differentiation trend. The upper third of the gabbroic crust is significantly more differentiated, in accord with a model of downward differentiation of a primitive parental melt originated from the axial melt lens located at the top of the gabbroic crust. Our hybrid model for crustal accretion requires a system to cool the deep crust, which was established by hydrothermal fault zones, initially formed on‐axis at very high temperatures.

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Section: Resultssupporting

confidence: 84%

A Reference Section Through Fast‐Spread Lower Oceanic Crust, Wadi Gideah, Samail Ophiolite (Sultanate of Oman): Petrography and Petrology

et al. 2022

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“…(2004) and supported by Mock et al. (2021). “Full Sheeted Sills' model is proposed in this study, melts derived directly from the mantle are shown in red; orange‐yellow regions correspond to mixtures of primitive melts and evolved melt emplaced in the upper gabbros after fractional crystallization in the lower gabbros.…”

Section: Discussionsupporting

confidence: 55%

“…Mock et al. (2021) argued for a Hybrid‐style model similar to Maclennan et al. (2004) and Kelemen et al.…”

Section: Discussionmentioning

confidence: 77%

The Composition of the Lower Oceanic Crust in the Wadi Khafifah Section of the Southern Samail (Oman) Ophiolite

et al. 2021

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“…They determined fast and near uniform cooling rates with depth (∼1-10 −2 °C/y), and inferred that hydrothermal circulation cooled the entire Hess Deep lithosphere, which accreted from solidification of periodically replenished magma bodies (sills). Mock et al (2021) investigated gabbros from the mid-plutonic and lowermost crust at the southern Oman ophiolite (Samail and Wadi Tayin massifs, respectively), recovering cooling rates of ∼10 −2 °C/y and ∼10 −1 °C/y through Ca-in-olivine and Mg-in-plagioclase closure temperatures, and demonstrating efficient heat loss from the lowermost crust, perhaps by deep hydrothermal circulation.…”

Section: Results From Previous Investigations That Constrained Cooling Rate Variations In Oceanic Lithospherementioning

confidence: 99%

Thermal History of Lithosphere Formed Beneath Fast Spreading Ridges: Constraints From the Mantle Transition Zone of the East Pacific Rise at Hess Deep and Oman Drilling Project, Wadi Zeeb, Samail Ophiolite

et al. 2022

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We investigate the cooling histories of peridotites and gabbros from localities that expose oceanic lithosphere formed beneath two fast seafloor spreading centers: Hess Deep as recovered from IODP Expedition 345 and ODP Leg 147, and the Oman Ophiolite as sampled by the Oman Drilling Project, ICDP Expedition 5057 (OmanDP). At these locations, relict crust‐mantle transition zones are directly sampled, enabling characterization of the thermal history of the crust‐mantle transition, and by inference, the depth extent of hydrothermal circulation beneath spreading centers. We measured major and trace element abundances in crustal gabbros and mantle peridotites from Hess Deep and OmanDP, and applied major and trace element‐based thermometers. Geospeedometric interpretation of the temperatures suggests similar cooling histories at both locations; cooling rates ranged from 0.02 to 2.6 °C/y from peak temperatures up to 1,350°C. The rates are consistent on either side of the paleo‐Moho (i.e., in the crust and mantle). Models for conductive cooling of the lower oceanic crust predict rates more than two orders of magnitude slower at the crust‐mantle transition zone, while thermal models that invoke deep and efficient hydrothermal circulation throughout the entire crustal section predict rates consistent with our observations. We infer that hydrothermal cooling extended to or near the petrologic Moho beneath the East Pacific Rise and the OmanDP paleo‐spreading center, consistent with the Sheeted Sills model for crustal accretion. Comparison with previously published rates recalculated using the methods we employed suggests the oceanic lower crust is cooled hydrothermally in some places and by conduction at others.

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Formation of Igneous Layering in the Lower Oceanic Crust From the Samail Ophiolite, Sultanate of Oman

Cited by 18 publications

References 121 publications

A Reference Section Through Fast‐Spread Lower Oceanic Crust, Wadi Gideah, Samail Ophiolite (Sultanate of Oman): Petrography and Petrology

A Reference Section Through Fast‐Spread Lower Oceanic Crust, Wadi Gideah, Samail Ophiolite (Sultanate of Oman): Petrography and Petrology

The Composition of the Lower Oceanic Crust in the Wadi Khafifah Section of the Southern Samail (Oman) Ophiolite

Thermal History of Lithosphere Formed Beneath Fast Spreading Ridges: Constraints From the Mantle Transition Zone of the East Pacific Rise at Hess Deep and Oman Drilling Project, Wadi Zeeb, Samail Ophiolite

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