Continental and oceanic core complexes

Whitney, Donna L.; Teyssier, Christian; Rey, Patrice; Buck, W. Roger

doi:10.1130/b30754.1

Cited by 302 publications

(308 citation statements)

References 194 publications

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“…Whitney et al, 2013). However, the combination of crustal metamorphic rocks and mantle rocks is unusual and conforms to neither continent or oceanic core complex endmember models.…”

Section: Discussionmentioning

confidence: 99%

Extreme extension across Seram and Ambon, eastern Indonesia: evidence for Banda slab rollback

2013

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Abstract. The island of Seram, which lies in the northern part of the 180 • -curved Banda Arc, has previously been interpreted as a fold-and-thrust belt formed during arc-continent collision, which incorporates ophiolites intruded by granites thought to have been produced by anatexis within a metamorphic sole. However, new geological mapping and a re-examination of the field relations cause us to question this model. We instead propose that there is evidence for recent and rapid N-S extension that has caused the hightemperature exhumation of lherzolites beneath low-angle lithospheric detachment faults that induced high-temperature metamorphism and melting in overlying crustal rocks. These "Kobipoto Complex" migmatites include highly residual AlMg-rich garnet + cordierite + sillimanite + spinel + corundum granulites (exposed in the Kobipoto Mountains) which contain coexisting spinel + quartz, indicating that peak metamorphic temperatures likely approached 900 • C. Associated with these residual granulites are voluminous MioPliocene granitic diatexites, or "cordierite granites", which crop out on Ambon, western Seram, and in the Kobipoto Mountains and incorporate abundant schlieren of spineland sillimanite-bearing residuum. Quaternary "ambonites" (cordierite + garnet dacites) emplaced on Ambon were also evidently sourced from the Kobipoto Complex migmatites as demonstrated by granulite-inherited xenoliths. Exhumation of the hot peridotites and granulite-facies Kobipoto Complex migmatites to shallower structural levels caused greenschistto lower-amphibolite facies metapelites and amphibolites of the Tehoru Formation to be overprinted by sillimanite-grade metamorphism, migmatisation, and limited localised anatexis to form the Taunusa Complex. The extreme extension required to have driven Kobipoto Complex exhumation evidently occurred throughout Seram and along much of the northern Banda Arc. The lherzolites must have been juxtaposed against the crust at typical lithospheric mantle temperatures in order to account for such high-temperature metamorphism and therefore could not have been part of a cooled ophiolite. In central Seram, lenses of peridotites are incorporated with a major left-lateral strike-slip shear zone (the "Kawa Shear Zone"), demonstrating that strike-slip motions likely initiated shortly after the mantle had been partly exhumed by detachment faulting and that the main strike-slip faults may themselves be reactivated and steepened lowangle detachments. The geodynamic driver for mantle exhumation along the detachment faults and strike-slip faulting in central Seram is very likely the same; we interpret the extreme extension to be the result of eastward slab rollback into the Banda Embayment as outlined by the latest plate reconstructions for Banda Arc evolution.

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“…Whitney et al, 2013). However, the combination of crustal metamorphic rocks and mantle rocks is unusual and conforms to neither continent or oceanic core complex endmember models.…”

Section: Discussionmentioning

confidence: 99%

Extreme extension across Seram and Ambon, eastern Indonesia: evidence for Banda slab rollback

2013

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“…by Blackman et al, 2009 andWhitney et al, 2013). Conversely, this concept is seldom used to describe mantle exhumation at MPPM (e.g.…”

Section: Extension Of the Core Complex Concept To Mantle Exhumationmentioning

confidence: 99%

“…Whitney et al, 2013) tend to overlook mantle exhumation at MPPM. However, the processes of mantle rocks exhumation at both spreading ridges and MPPM have been considered together for their potential to interpret Tethyan ophiolites (Lagabrielle and Lemoine, 1997;Lagabrielle, 2009).…”

Section: Extension Of the Core Complex Concept To Mantle Exhumationmentioning

confidence: 99%

Crustal versus mantle core complexes

et al. 2018

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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. Contrary to what is commonly believed, it is argued from analogue and numerical models that detachments that accommodate exhumation of core complexes do not initiate at the onset of extension but in the course of progressive extension when the exhuming ductile crust reaches the surface. In models, convex upward detachments result from a rolling hinge process. A C C E P T E D M A N U S C R I P TMantle core complexes develop in either the oceanic lithosphere, at slow and ultra-slow spreading ridges, or in continental lithospheres, whose initial Moho temperature is lower than 750°C, with "sub-Moho mantle-dominated" strength profiles. It is argued that the mechanism of mantle exhumation at passive margins is a nearly symmetrical necking process at ACCEPTED MANUSCRIPTA C C E P T E D M A N U S C R I P T 2 lithosphere scale without major and permanent detachment, except if strong strain localization could occur in the lithosphere mantle. Distributed crustal extension, by upper crust faulting above a décollement along the ductile crust increases toward the rift axis up to crustal breakup.Mantle rocks exhume in the zone of crustal breakup accommodated by conjugate mantle shear zones that migrate with the rift axis, during increasing extension.

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“…A major limitation of this theory is that for brittle layer thicknesses typical of most continental rift zones only small offset faults are predicted, yet faulting in these regions range from short-lived faults to long-lived detachments forming metamorphic core complexes [e.g., Whitney et al, 2013]. Additional controls such as rapid hydrothermal cooling [Lavier and Buck, 2002] and magmatic processes [Buck et al, 2005] have been proposed to explain large offset faulting, but those are more relevant to mid-ocean ridge settings and thus cannot explain this discrepancy between the models and observations in continental rifts.…”

Section: Introductionmentioning

confidence: 99%

“…Broadly speaking, fault life span determines whether the "building block" of a rift system is a half-graben structure (characteristic offset smaller than the faulted layer thickness, typically a few km), a long-lived, low-angle detachment fault (with offset in the 10-50 km range, resulting in surficial exposure of lower crustal units), or a combination of both [e.g., Morley, 1995;Lavier et al, 2000;Lavier and Buck, 2002;Whitney et al, 2013]. Over the past two decades a robust conceptual framework has been assembled to identify the first-order controls on the modes of extensional faulting [e.g., Forsyth, 1992;Buck, 1993;Lavier et al, 2000;Lavier and Buck, 2002;Behn and Ito, 2008;Olive and Behn, 2014].…”

Section: Introductionmentioning

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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Continental and oceanic core complexes

Cited by 302 publications

References 194 publications

Extreme extension across Seram and Ambon, eastern Indonesia: evidence for Banda slab rollback

Extreme extension across Seram and Ambon, eastern Indonesia: evidence for Banda slab rollback

Crustal versus mantle core complexes

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

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