Life cycle of oceanic core complexes

MacLeod, C. J.; Searle, R. C.; Murton, Bramley J.; Casey, John F.; Mallows, C.; Unsworth, S.; Achenbach, K. L.; Harris, Michelle

doi:10.1016/j.epsl.2009.08.016

Cited by 258 publications

(400 citation statements)

References 46 publications

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“…While large-offset, low-angle extensional faults have long been suspected of exhuming gabbros and mantle peridotites at slow and ultraslow ocean ridges (e.g., Dick et al, 1981), only in the last decade or so have these features become a focus of attention. Investigation shows that extension can become localized along 'detachment faults' for several million years and expose large areas (hundreds of square kilometers) of lower crustal gabbros and mantle peridotites on the seafloor, creating smoothly corrugated topographic highs known as 'megamullions' or 'oceanic core complexes ' (e.g., Blackman et al, 1998;MacLeod et al, 2009;Smith et al, 2006). In these areas, spreading becomes asymmetric.…”

mentioning

confidence: 99%

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Composition of the Oceanic Crust

White

Klein²

2014

Treatise on Geochemistry

190

160

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confidence: 99%

“…It was initially thought that core complexes were amagmatic; it is now recognized that magmatism, and volcanism, may persist during core complex development. In that case, magma is generally emplaced into the footwall of the detachment fault, explaining the frequent presence of gabbro bodies at these core complexes MacLeod et al, 2009). …”

mentioning

confidence: 99%

Composition of the Oceanic Crust

White

Klein²

2014

Treatise on Geochemistry

190

160

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“…However, an increasing body of evidence points to systematically faster extension on the OCC side than on the conjugate side [Baines et aL., 2008;Dick et al, 2008;MacLeod et al, 2009], which should be a major focus of future modeling studies. Symmetric emplacement of the lower-crust in our model is a direct consequence of two assumptions that will have to be relaxed in future studies.…”

Section: ]mentioning

confidence: 99%

Mechanical and geological controls on the long-term evolution of normal faults

Olive¹

2015

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This thesis investigates the long-term evolution of rift-bounding normal faults. To first order, the observed diversity of extensional tectonic styles reflects differences in the maximum offset that can be accommodated on individual faults during their life span. My main objective is to develop a theoretical framework that explains these differences in terms of a few key mechanical and geological controls. I start by laying out the energy cost associated with slip on a normal fault, which consists of (1) overcoming the frictional resistance on the fault, (2) bending the faulted layer and (3) sustaining the growth of topography. In Chapter 2, I propose that flexural rotation of the active fault plane enables faults to evolve along a path of minimal energy, thereby enhancing their life span. Flexural rotation occurs more rapidly in thinner faulted layers, and can potentially explain the wide range of normal fault dips documented with focal mechanisms. In Chapter 3, I show that surface processes can enhance the life span of continental normal faults by reducing the energy cost associated with topography buildup. In Chapter 4, I focus on lithospheric bending induced by fault growth, which is well described by elasto-plastic flexure models. I demonstrate that numerical models that treat the lithosphere as a visco-plastic solid can properly predict fault evolution only when the rate-dependent viscous flexural wavelength of the lithosphere is accommodated within the numerical domain. In Chapter 5, I consider the interplay of faulting and crustal emplacement at a slow mid-ocean ridge. I show that a depth-variable rate of magma emplacement can reconcile the formation of long-lived detachment faults, which requires a moderate melt supply, and the exhumation of large volumes of lower crustal material. Finally, in Chapter 6 I investigate the three-dimensional interactions between normal faults in a lithosphere of varying thickness. I suggest that large along-axis gradients in lithospheric thickness can prevent the growth of continuous faults along-axis, and instead decouple the modes of faulting at the segment center and at the segment end. AcknowledgementsIt all started seven years ago when Dr. Mark Behn from the Woods Hole Oceanographic Institution received yet another random student email asking for a research internship. Little did I know at the time that this email would pass all of Mark's background checks (1/ "he has funding ", 2/ "my French friends approve of him") and open a whole new chapter of my life -a chapter filled with exciting science, trips to exotic locations, and lots of espressos (an estimated 3800). And now here we are. I may still not know much about baseball or the proper use of m-dashes, but I am walking out of grad school as an independent (and slightly sarcastic) scientist, which is perhaps what I am most grateful for. I look forward to future collaborations on proving that grain size reduction is the key to a good espresso, if not to Plate Tectonics, life on Earth, and the meaning of exi...

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“…The general view about OCC suggests that they form in a tectonic regime with very low magma supply (e.g. MacLeod et al 2009). Detailed studies of OCCs at the Mid-Atlantic Ridge (e.g.…”

Section: Soifs and Oceanic Crust Formationmentioning

confidence: 99%

“…Oceanic core complexes are bathymetric features composed (1) the magnetic anomaly grid (Gaina et al, this volume, in review); (2) the crustal thickness derived from seismic refraction data (Funck et al 2016); (3) the crustal thickness from gravity inversion (Haase et al, this volume, in press); (4) half seafloor spreading rates; and (5) seafloor spreading asymmetry (Gaina et al, this volume, in review of mantle rocks exposed on the seafloor by large detachment faulting. These tectonic features can have lengths up to 150 km and widths up to 15 km, with a height of between 500 and 1500 km (MacLeod et al 2009). It has been postulated that OCCs can be associated with serpentinized peridotites and, therefore, have very weak magnetization (e.g.…”

Section: Soifs and Oceanic Crust Formationmentioning

confidence: 99%

Seamounts and oceanic igneous features in the NE Atlantic: a link between plate motions and mantle dynamics

Gaina

Blischke

Geissler

et al. 2016

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A new regional compilation of seamount-like oceanic igneous features (SOIFs) in the NE Atlantic points to three distinct oceanic areas of abundant seamount clusters. Seamounts on oceanic crust dated 54-50 Ma are formed on smooth oceanic basement, which resulted from high spreading rates and magmatic productivity enhanced by higher than usual mantle plume activity. Late Eocene-Early Miocene SOIF clusters are located close to newly formed tectonic features on rough oceanic crust in the Irminger, Iceland and Norway basins, reflecting an unstable tectonic regime prone to local readjustments of mid-ocean ridge and fracture zone segments accompanied by extra igneous activity. A SOIF population observed on Mid-Miocene-Present rough oceanic basement in the Greenland and Lofoten basins, and on conjugate Kolbeinsey Ridge flanks, coincides with an increase in spreading rate and magmatic productivity. We suggest that both tectonic/kinematic and magmatic triggers produced Mid-Miocene-Present SOIFs, but the Early Miocene westwards ridge relocation may have played a role in delaying SOIF formation south of the Jan Mayen Fracture Zone. We conclude that Iceland plume episodic activity combined with regional changes in relative plate motion led to local mid-ocean ridge readjustments, which enhanced the likelihood of seamount formation.

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Life cycle of oceanic core complexes

Cited by 258 publications

References 46 publications

Composition of the Oceanic Crust

Composition of the Oceanic Crust

Mechanical and geological controls on the long-term evolution of normal faults

Seamounts and oceanic igneous features in the NE Atlantic: a link between plate motions and mantle dynamics

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