Lateral variations of pressure-temperature evolution in non-cylindrical orogens and 3-D subduction dynamics: the Betic-Rif Cordillera example

The long-term Pressure-Temperature-time-deformation (P-T-t-d) evolution of the internal zones of orogens results from complex interactions between the subducting lithosphere, the overriding plate and the intervening asthenosphere. 2-D numerical models successfully reproduce natural P-T-t-d paths, but most orogens are non-cylindrical and the situation is far more complex because of 3-D pre-orogenic inheritance and 3-D subduction dynamics. The Mediterranean orogens are intrinsically non-cylindrical because of the complex shape of the Eurasian and African margins before convergence and because subducting slabs changed configuration during retreat, getting narrower through a series of tearing events leading to strongly arcuate finite geometries. The Betic-Rif belt is archetypal of this behavior. A synthesis of the tectonometamorphic evolution of the Internal Zones, also based on recent findings by our group in the framework of the Orogen Project (Alboran domain, including the Alpujárride and Nevado-Filabride complexes) shows the relations in space and time between deformation and P-T evolution. The reinterpretation of the contact between peridotite massifs and Mesozoic sediments as an extensional detachment leads to a discussion of the geodynamic setting and timing of mantle exhumation. We then find that the age of the HP-LT metamorphism is Eocene in all units, based on new 40Ar/39Ar ages in the Alpujarride complex and a discussion of published ages in the Nevado-Filabride complex. A first-order observation is the contrast between the well-preserved Eocene HP-LT blueschists-facies rocks of the eastern Alpujárride complex and the younger HT-LP conditions reaching partial melting recorded in the Western Alpujárride. We propose a model where the large longitudinal variations in the P-T evolution are mainly due to (i) differences in the timing of subduction and exhumation, (ii) the nature of the subducting lithosphere and (iii) a major change in subduction dynamics at ~20 Ma associated with a slab tearing event. The clustering of radiometric ages around 20 Ma results from a regional exhumation episode coeval with slab tearing, westward migration of the trench, back-arc extension and thrusting of the whole orogen onto the African and Iberian margins.

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Lateral variations of pressure-temperature evolution in non-cylindrical orogens and 3-D subduction dynamics: the Betic-Rif Cordillera example

10.5194/egusphere-egu21-7837 ◽

2021 ◽

Author(s):

Eloïse Bessière ◽

Laurent Jolivet ◽

Romain Augier ◽

Stéphane Scaillet ◽

Jacques Précigout ◽

...

Keyword(s):

Mediterranean Region ◽

Major Change ◽

Geodynamic Setting ◽

Time Deformation ◽

Complex Interactions ◽

Longitudinal Variations ◽

The Mediterranean ◽

Slab Tearing ◽

Mantle Exhumation

Orogens closely linked to 3-D subduction dynamics are frequently non-cylindrical and the Mediterranean region is a perfect natural laboratory to observe several of them, as well as their interactions. Through the succession of extension, subduction and sometimes collision events, the kinematic reconstructions of such orogens can be difficult and the subject of active debates. The internal zones are often non-consensual, especially when their long-term Pressure-Temperature-time-deformation (P-T-t-d) evolutions are studied. This complexity is mostly due to pre-orogenic inheritance or complex interactions between the subducting lithosphere, the overriding plate and the asthenosphere. All these elements are described and documented in Mediterranean orogens, i.e., a complex shape of the Eurasian and African margins in pre-orogenic times and a complex slab retreat and tearing dynamics. Their 3-D geometry results in strongly arcuate belts, such as the Betic-Rif Cordillera, located in the westernmost part of the Mediterranean region.Focused on the Internal Zones of the Betic-Rif Cordillera and based on recent findings (Orogen Project framework), a synthesis of the tectono-metamorphic evolution shows the relations in space and time between tectonic and P-T evolutions. The reinterpretation of the contact between peridotite massifs and Mesozoic sediments as an extensional detachment leads to a discussion of the geodynamic setting and timing of mantle exhumation. Based on new 40Ar/39Ar ages in the Alpuj&#225;rride Complex (metamorphic formations of the Betic Internal Zones) and a discussion of published ages in the Nevado-Filabride Complex (metamorphic formations of the Betic Internal Zones), we conclude that the age of the HP-LT metamorphism is Eocene in all the Internal Zones. A first-order observation is the contrast between the well-preserved Eocene HP-LT blueschists-facies rocks of the Eastern Alpuj&#225;rride-Sebtide Complex and the younger HT-LP conditions reaching partial melting recorded in the Western Alpuj&#225;rride. We propose a model where the large longitudinal variations in the P-T evolution are mainly due to (i) differences in the timing of subduction and exhumation, (ii) the nature of the subducting lithosphere and (iii) a major change in subduction dynamics at ~20 Ma associated with a slab-tearing event.

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The Pressure‐Temperature‐time‐deformation history of the Beni Mzala unit (Upper Sebtides, Rif belt, Morocco): Refining the Alpine tectono‐metamorphic evolution of the Alboran Domain of the Western Mediterranean

Journal of Metamorphic Geology ◽

10.1111/jmg.12587 ◽

2020 ◽

Author(s):

Sara Marrone ◽

Patrick Monié ◽

Federico Rossetti ◽

Federico Lucci ◽

Thomas Theye ◽

...

Keyword(s):

Western Mediterranean ◽

Deformation History ◽

Metamorphic Evolution ◽

Time Deformation ◽

Rif Belt ◽

History Of ◽

Temperature Time

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Petrology of lower-middle Miocene Zoumi Flysch Fm. (Mesorif sub-domain, Rif belt, Morocco): first evidence of mixed mode provenance and geodynamic setting

Arabian Journal of Geosciences ◽

10.1007/s12517-018-3485-7 ◽

2018 ◽

Vol 11 (9) ◽

Cited By ~ 1

Author(s):

Mohamed El Mourabet ◽

Ahmed Barakat ◽

Jamila Rais ◽

Mohamed Najib Zaghloul ◽

Achraf Atouabat

Keyword(s):

Mixed Mode ◽

Middle Miocene ◽

Geodynamic Setting ◽

Rif Belt

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Ridge Jumps and Mantle Exhumation in Back-Arc Basins

Geosciences ◽

10.3390/geosciences11110475 ◽

2021 ◽

Vol 11 (11) ◽

pp. 475

Author(s):

Valentina Magni ◽

John Naliboff ◽

Manel Prada ◽

Carmen Gaina

Keyword(s):

Continental Crust ◽

Oceanic Crust ◽

Numerical Models ◽

Spreading Ridge ◽

Transient Nature ◽

Mid Ocean Ridge ◽

Thinned Continental Crust ◽

Mantle Exhumation ◽

Back Arc ◽

Ocean Ridge

Back-arc basins in continental settings can develop into oceanic basins, when extension lasts long enough to break up the continental lithosphere and allow mantle melting that generates new oceanic crust. Often, the basement of these basins is not only composed of oceanic crust, but also of exhumed mantle, fragments of continental crust, intrusive magmatic bodies, and a complex mid-ocean ridge system characterised by distinct relocations of the spreading centre. To better understand the dynamics that lead to these characteristic structures in back-arc basins, we performed 2D numerical models of continental extension with asymmetric and time-dependent boundary conditions that simulate episodic trench retreat. We find that, in all models, episodic extension leads to rift and/or ridge jumps. In our parameter space, the length of the jump ranges between 1 and 65 km and the timing necessary to produce a new spreading ridge varies between 0.4 and 7 Myr. With the shortest duration of the first extensional phase, we observe a strong asymmetry in the margins of the basin, with the margin further from trench being characterised by outcropping lithospheric mantle and a long section of thinned continental crust. In other cases, ridge jump creates two consecutive oceanic basins, leaving a continental fragment and exhumed mantle in between the two basins. Finally, when the first extensional phase is long enough to form a well-developed oceanic basin (>35 km long), we observe a very short intra-oceanic ridge jump. Our models are able to reproduce many of the structures observed in back-arc basins today, showing that the transient nature of trench retreat that leads to episodes of fast and slow extension is the cause of ridge jumps, mantle exhumation, and continental fragments formation.

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Sensitivity and identifiability of rheological parameters in debris flow modeling

Natural Hazards and Earth System Science ◽

10.5194/nhess-20-1919-2020 ◽

2020 ◽

Vol 20 (7) ◽

pp. 1919-1930

Author(s):

Gerardo Zegers ◽

Pablo A. Mendoza ◽

Alex Garces ◽

Santiago Montserrat

Keyword(s):

Sensitivity Analysis ◽

Debris Flow ◽

Numerical Models ◽

Maximum Flow ◽

Rheological Parameters ◽

Model Parameters ◽

Maximum Height ◽

Complex Interactions ◽

Relevant Variables ◽

Distributed Evaluation

Abstract. Over the past decades, several numerical models have been developed to understand, simulate and predict debris flow events. Typically, these models simplify the complex interactions between water and solids using a single-phase approach and different rheological models to represent flow resistance. In this study, we perform a sensitivity analysis on the parameters of a debris flow numerical model (FLO-2D) for a suite of relevant variables (i.e., maximum flood area, maximum flow velocity, maximum height and deposit volume). Our aims are to (i) examine the degree of model overparameterization and (ii) assess the effectiveness of observational constraints to improve parameter identifiability. We use the Distributed Evaluation of Local Sensitivity Analysis (DELSA) method, which is a hybrid local–global technique. Specifically, we analyze two creeks in northern Chile (∼29∘ S, 70∘ W) that were affected by debris flows on 25 March 2015. Our results show that SD (surface detention) and β1 (a parameter related to viscosity) provide the largest sensitivities. Further, our results demonstrate that equifinality is present in FLO-2D and that the final deposited volume and maximum flood area contain considerable information to identify model parameters.

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Where’s the fat? Freeze-fracture analysis of ingredient interactions in food systems

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100146084 ◽

1993 ◽

Vol 51 ◽

pp. 48-49

Author(s):

Jean Fincher

Keyword(s):

Lipid Droplets ◽

Food Systems ◽

Food Industry ◽

Freeze Fracture ◽

Food Science ◽

Complex Interactions ◽

Fat Reduction ◽

Important Trend ◽

Conventional Foods ◽

Whipped Cream

An important trend in the food industry today is reduction in the amount of fat in manufactured foods. Often fat reduction is accomplished by replacing part of the natural fat with carbohydrates which serve to bind water and increase viscosity. It is in understanding the roles of these two major components of food, fats and carbohydrates, that freeze-fracture is so important. It is well known that conventional fixation procedures are inadequate for many food products, in particular, foods with carbohydrates as a predominant structural feature. For some food science applications the advantages of freeze-fracture preparation procedures include not only the avoidance of chemical fixatives, but also the opportunity to control the temperature of the sample just prior to rapid freezing.In conventional foods freeze-fracture has been used most successfully in analysis of milk and milk products. Milk gels depend on interactions between lipid droplets and proteins. Whipped emulsions, either whipped cream or ice cream, involve complex interactions between lipid, protein, air cell surfaces, and added emulsifiers.

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