scholarly journals Melt volume at Atlantic volcanic rifted margins controlled by depth-dependent extension and mantle temperature

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gang Lu ◽  
Ritske S. Huismans
Keyword(s):  
Numerical Models ◽  
Potential Temperature ◽  
Analytical Prediction ◽  
Natural Systems ◽  
Passive Margins ◽  
Margin Width ◽  
Rifted Margins ◽  
Mantle Potential Temperature ◽  
Mantle Temperature ◽  
Rifted Margin

AbstractBreakup volcanism along rifted passive margins is highly variable in time and space. The factors controlling magmatic activity during continental rifting and breakup are not resolved and controversial. Here we use numerical models to investigate melt generation at rifted margins with contrasting rifting styles corresponding to those observed in natural systems. Our results demonstrate a surprising correlation of enhanced magmatism with margin width. This relationship is explained by depth-dependent extension, during which the lithospheric mantle ruptures earlier than the crust, and is confirmed by a semi-analytical prediction of melt volume over margin width. The results presented here show that the effect of increased mantle temperature at wide volcanic margins is likely over-estimated, and demonstrate that the large volumes of magmatism at volcanic rifted margin can be explained by depth-dependent extension and very moderate excess mantle potential temperature in the order of 50–80 °C, significantly smaller than previously suggested.

The effect of magma poor and magma rich rifted margins on continental collision dynamics

2021 ◽  
Author(s):  
Valeria Turino ◽  
Valentina Magni ◽  
Hans Jørgen Kjøll ◽  
Johannes Jakob
Keyword(s):  
Oceanic Lithosphere ◽  
Continental Collision ◽  
Passive Margin ◽  
Collision Dynamics ◽  
Large Variability ◽  
Passive Margins ◽  
Continental Plate ◽  
Rifted Margins ◽  
Wide Range ◽  
Rifted Margin

<p>The transition between continental and oceanic lithosphere in rifted margins can display a wide range of characteristics, which primarily depend on the regional tectonic evolution. Rifted margins form when continents rift apart and are commonly characterized by a thinned transition zone between the continental crust and the oceanic crust. The velocity and duration of the rifting process influence the dimensions and geometry of the passive margin. Rifted (or passive) margins are often subdivided in a magma-rich type and a magma-poor type, where the magma-rich are characterized by large input of mafic melt, derived from the mantle, into the crust. Magma-poor rifted margins on the other hand are characterized by much less magma production during the rifting process. This causes high variability in the geometry and rheology of passive margins.</p><p>The aim of this work is to understand how different types of passive margins can influence the dynamics of continental collision. We modelled subduction using the finite element code Citcom and to describe the dynamics of continental collision we mainly focused on the time and position of the slab break-off after the collision and on the fate of the passive margin material.</p><p>We compared these models as a function of various parameters (e.g., margin length, density, and viscosity), in order to understand how the architecture of a passive margin affects the dynamics of continental collision. We find that passive margins have a noticeable impact on subduction, as we observe a large variability in slab break-off times (about 10–70 Myr after continental collision) and depth (about 200–450 km). Furthermore, the factor that shows the largest impact on subduction dynamics is the rheology of the passive margin. Our results show that for both magma-poor and magma-rich margins, part of the margin does not subduct but, instead, exhumes and accretes to the overriding plate. Importantly, the amount of accreted material to the overriding plate is much larger when the passive margin is magma-poor compared to the magma-rich case. This is consistent with geological observations that fossil magma-poor passive margins are preserved in many mountain ranges, such as the Alps and the Scandinavian Caledonides, whereas remnants of magma-rich rifted margins are scarce. Because, in our models, the slab break-off occurs inboard of the LCB, magma-rich rifted margin may only be preserved when the density of the LCB is similar to that of the rest of the continental plate. Therefore magma-rich rifted margins are prone to be subducted and recycled into the mantle. Importantly, our results show that rifted margin type controls the architecture of the subsequent collisional phase of the Wilson cycle.</p>

scholarly journals Rheological inheritance controls the formation of segmented rifted margins in cratonic lithosphere

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
M. Gouiza ◽  
J. Naliboff
Keyword(s):  
Large Scale ◽  
Labrador Sea ◽  
Structural Domains ◽  
Continental Extension ◽  
Margin Width ◽  
Lithospheric Thickness ◽  
Rifted Margins ◽  
Tectonic History ◽  
Rifted Margin

AbstractObservations from rifted margins reveal that significant structural and crustal variability develops through the process of continental extension and breakup. While a clear link exists between distinct margin structural domains and specific phases of rifting, the origin of strong segmentation along the length of margins remains relatively ambiguous and may reflect multiple competing factors. Given that rifting frequently initiates on heterogenous basements with a complex tectonic history, the role of structural inheritance and shear zone reactivation is frequently examined. However, the link between large-scale variations in lithospheric structure and rheology and 3-D rifted margin geometries remains relatively unconstrained. Here, we use 3-D thermo-mechanical simulations of continental rifting, constrained by observations from the Labrador Sea, to unravel the effects of inherited variable lithospheric properties on margin segmentation. The modelling results demonstrate that variations in the initial crustal and lithospheric thickness, composition, and rheology produce sharp gradients in rifted margin width, the timing of breakup and its magmatic budget, leading to strong margin segmentation.

scholarly journals Continental basalts track secular cooling of the mantle and the onset of modern plate tectonics

2021 ◽  
Author(s):  
Qian Chen ◽  
He Liu ◽  
Tim Johnson ◽  
Michael Hartnady ◽  
Christopher Kirkland ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Plate Tectonics ◽  
Potential Temperature ◽  
Snowball Earth ◽  
Secular Changes ◽  
First Order ◽  
The Past ◽  
Mantle Potential Temperature ◽  
Mantle Temperature ◽  
Early Neoproterozoic

Abstract The temperature of the convecting mantle exerts a first-order control on the tectonic behaviour of Earth’s lithosphere. Although the mantle has likely been cooling since the Archaean eon (4.0–2.5 billion years ago), how mantle temperature evolved thereafter is poorly understood. Here, we apply a statistical analysis to secular changes in the alkali index (A.I. = whole-rock (Na2O + K2O)2/(SiO2 – 38) as weight%) of intracontinental basalts globally to constrain the evolution of mantle potential temperature (Tp) over the past billion years. During the early Neoproterozoic, Tp remained relatively constant at ~1450 °C until the Cryogenian (720 to 635 million years ago), when mantle temperature dropped by ~50 °C over <180 million years. This remarkable episode of cooling records the onset of modern-style plate tectonics, which has been suggested to have been triggered by a dramatic increase in the supply of sediments to lubricate trenches during the thawing of the Snowball Earth.

scholarly journals The role of inheritance in forming rifts and rifted margins and building collisional orogens: a Biscay-Pyrenean perspective

2021 ◽  
Author(s):  
Gianreto Manatschal ◽  
Pauline Chenin ◽  
Rodolphe Lescoutre ◽  
Jordi Miró ◽  
Patricia Cadenas ◽  
...  
Keyword(s):  
Numerical Models ◽  
Rift System ◽  
Rifted Margins ◽  
New Concepts ◽  
The Alps ◽  
Orogenic Cycle ◽  
Work Done ◽  
Collisional Orogens ◽  
Rifted Margin

The aim of this paper is to provide a conceptual framework that integrates the role of inheritance in the study of rifts, rifted margins and collisional orogens based on the work done in the OROGEN project, which focuses on the Biscay-Pyrenean system. The Biscay-Pyrenean rift system resulted from a complex multistage rift evolution that developed over a complex lithosphere pre-structured by the Variscan orogenic cycle. There is a general agreement that the Pyrenean-Cantabrian orogen resulted from the reactivation of an increasingly mature rift system along-strike, ranging from a mature rifted margin in the west to an immature and segmented hyperextended rift in the east. However, different models have been proposed to explain the preceding syn-rift evolution and its influence on the subsequent reactivation. Results from the OROGEN project show a sequential reactivation of rift inherited decoupling horizons and identify the specific role of exhumed mantle, hyperextended and necking domains during reactivation. They also highlight the contrasting fate of segment centres vs. segment boundaries during convergence, explaining the non-cylindricity of internal parts of collisional orogens. Results from the OROGEN project also suggest that the role of inheritance is more important during the initial stages of subduction and collision, which may explain the complexity of internal parts of orogenic systems. In contrast, once tectonic systems get more mature, orogenic evolution becomes mostly controlled by first-order physical processes as described in the Coulomb Wedge theory for instance. This may account for the simpler and more continuous architecture of external parts of collisional orogens. It may also explain why most numerical models can reproduce mature orogenic and rift architectures with better accuracy compared to the initial stages of such systems. Thus, while inheritance may not explain steady-state processes, it is a prerequisite for comprehending the initial stages of tectonic systems. The new concepts developed from the OROGEN research are now ready to be tested at other orogenic systems that result from the reactivation of rifted margins, such as the Alps, the Colombian cordilleras and the Caribbean, Taiwan, Oman, Zagros or Timor.

Passive-margin delta stratigraphy from source-to-sink numerical models: parametric studies and comparison with natural systems

2020 ◽  
Author(s):  
Brendan Simon ◽  
Cécile Robin ◽  
Delphine Rouby ◽  
Xiaoping Yuan ◽  
Laure Guerit ◽  
...  
Keyword(s):  
Landscape Evolution ◽  
Numerical Models ◽  
Input Parameter ◽  
Passive Margin ◽  
Geometrical Parameters ◽  
Natural Systems ◽  
Passive Margins ◽  
Source To Sink ◽  
Deposition Processes ◽  
The Impact

&lt;p&gt;One major and under-appreciated aspect of coupled erosion-deposition numerical modeling is the ranges of input parameter values used to simulate natural source to sink systems without considering their meaning in term of erosion, transport and deposition processes. Most of the time, numerical models are used as a semi-inversion tool based on a &amp;#8220;best-fit&amp;#8221; approach, especially in its marine part where it aims to reproduce well-constrained sedimentary architectures which are great recorders of landscape evolution through time.&lt;/p&gt;&lt;p&gt;In this study, we performed several simulations using a new numerical landscape evolution model that accounts for both erosion and deposition onshore, as well as sediment deposition in the marine domain (Yuan et al., 2019; COLORS project, funded by Total). In the marine domain, sediment dynamic is described by a diffusion equation and the diffusion or transport coefficient has been calibrated from natural delta geometries. This model is highly efficient and allows the separation of the different processes involved and exploration of various setups and parameters values in order to address a large variety of questions. Its efficiency also allows inverse simulations that are powerful to determine the best possible scenarios in terms of climatic or tectonic reconstructions, or to determine the evolution of several key parameters.&lt;/p&gt;&lt;p&gt;In order to evaluate the model reliability to reproduce realistic sedimentary geometries, we explore the impact of perturbations in climatic, eustatic or tectonic parameters of the model on the stratigraphic architecture of passive margins shelf-edge deltas and discuss its feedbacks with the erosion dynamic of the onshore domain. This sensitivity analysis also allowed us to define the most relevant geometrical parameters of observed or theoretical stratigraphic architectures that have to be include in the misfit function of the inversions and optimization scheme.&lt;/p&gt;&lt;p&gt;&lt;em&gt;This study is part of the COLORS project, funded by Total.&lt;/em&gt;&lt;/p&gt;

Role of kinematic thermomechanical modelling on constraining asymmetric continental break up

2021 ◽  
Author(s):  
Paul Perron ◽  
Laetitia Le Pourhiet ◽  
Anthony Jourdon ◽  
Tristan Cornu ◽  
Claude Gout
Keyword(s):  
Numerical Modelling ◽  
Cross Sections ◽  
Initial Conditions ◽  
Numerical Models ◽  
Mechanical Coupling ◽  
Lithospheric Thickness ◽  
Rifted Margins ◽  
Major Player ◽  
Long Time ◽  
Rifted Margin

&lt;p&gt;For a long time, the complexity of the lithosphere was ignored by numerical modelling because the inherited structural and compositional complexity of the &amp;#8220;real&amp;#8221; lithosphere is indeed mainly unknown to geologists so modeler preferred to understand first order parameters such as rate of extension, lithospheric thickness, mechanical coupling or decoupling at the Moho. These models were not representative of any particular region but they were helpful. As a wider community of geologist became interested in numerical modelling, a growing number of numerical models have attempted to account for a major player in structural geology: inheritance. However, the complexity of &amp;#8220;real&amp;#8221; Earth has been simplified and &amp;#8220;idealized&amp;#8221; where inherited &amp;#8220;anomalies&amp;#8221; (e.g. fault, pluton, craton) or a combination of them has been added without really knowing the exact initial conditions which are the unknown of the problem. Yet another approach has been to add a lot of them in a more or less random mater or to replace them by initial noise in the parameters. None of these approaches actually fulfil the need for end-users community to have predictive models.&lt;/p&gt;&lt;p&gt;Realizing that structural inheritance is some kind of kinematic forcing in the solution of the models but also that it is not possible to anticipate and identify all the geological structures that can be inherited in rifted margin lithospheres, we have developed a new approach, through the integration of a new kinematic module to pTatin2D thermomechanical code, permitting to understand the kinematics of deformation of the continental lithosphere and asthenosphere through time leading to the establishment of rifted margins. The method is settled and validated by fitting the architecture (i.e. basement, Moho, LAB, Tmax) and by solving the kinematics of a random unknow 2D cross section extracted from 3D thermomechanical rifted margin model.&lt;/p&gt;&lt;p&gt;This new tool aims to help geologists to better constrain and draw on their 2D geological cross sections the position of the Moho, the Lithosphere-Asthenosphere boundary (LAB), the temperature isotherms and the heat flux.&lt;/p&gt;&lt;p&gt;Key words: Kinematic thermomechanical modelling, asymmetric rifted margin architecture, modelling method.&lt;/p&gt;

scholarly journals Cenozoic magmatism in Indochina: lithosphere extension and mantle potential temperature

1993 ◽  
Vol 33 ◽  
pp. 211-222 ◽  
Author(s):  
Martin F.J. Flower ◽  
◽  
Hoang Nguyen ◽  
Trong Yem Nguyen ◽  
Xuan Bao Nguyen ◽  
...  
Keyword(s):  
Potential Temperature ◽  
Mantle Potential Temperature ◽  
Cenozoic Magmatism

Experimental constraints on the damp peridotite solidus and oceanic mantle potential temperature

Science ◽  
2017 ◽  
Vol 355 (6328) ◽  
pp. 942-945 ◽  
Author(s):  
Emily Sarafian ◽  
Glenn A. Gaetani ◽  
Erik H. Hauri ◽  
Adam R. Sarafian
Keyword(s):  
Potential Temperature ◽  
Mantle Potential Temperature

Rift inheritance controls the switch from thin- to thick-skinned thrusting and basal décollement re-localization at the subduction-to-collision transition

2021 ◽  
Author(s):  
Stefano Tavani ◽  
Pablo Granado ◽  
Amerigo Corradetti ◽  
Giovanni Camanni ◽  
Gianluca Vignaroli ◽  
...  
Keyword(s):  
Sedimentary Cover ◽  
Complete Removal ◽  
Lower Plate ◽  
Accretionary Wedge ◽  
Convergent Margins ◽  
Middle Crust ◽  
Rifted Margins ◽  
Thrust System ◽  
Structural Levels ◽  
Rifted Margin

In accretionary convergent margins, the subduction interface is formed by a lower plate décollement above which sediments are scraped off and incorporated into the accretionary wedge. During subduction, the basal décollement is typically located within or at the base of the sedimentary pile. However, the transition to collision implies the accretion of the lower plate continental crust and deformation of its inherited rifted margin architecture. During this stage, the basal décollement may remain confined to shallow structural levels as during subduction or re-localize into the lower plate middle-lower crust. Modes and timing of such re-localization are still poorly understood. We present cases from the Zagros, Apennines, Oman, and Taiwan belts, all of which involve a former rifted margin and point to a marked influence of inherited rift-related structures on the décollement re-localization. A deep décollement level occurs in the outer sectors of all of these belts, i.e., in the zone involving the proximal domain of pre-orogenic rift systems. Older—and shallower—décollement levels are preserved in the upper and inner zones of the tectonic pile, which include the base of the sedimentary cover of the distal portions of the former rifted margins. We propose that thinning of the ductile middle crust in the necking domains during rifting, and its complete removal in the hyperextended domains, hampered the development of deep-seated décollements during the inception of shortening. Progressive orogenic involvement of the proximal rift domains, where the ductile middle crust was preserved upon rifting, favors its reactivation as a décollement in the frontal portion of the thrust system. Such décollement eventually links to the main subduction interface, favoring underplating and the upward motion of internal metamorphic units, leading to their final emplacement onto the previously developed tectonic stack.

Modelling thermal lithospheric thickness along the conjugate South Atlantic passive margins implies asymmetric rift initiation

2021 ◽  
Author(s):  
Peter Haas ◽  
R. Dietmar Müller ◽  
Jörg Ebbing ◽  
Gregory A. Houseman ◽  
Nils-Peter Finger ◽  
...  
Keyword(s):  
South Atlantic ◽  
Heterogeneous Structure ◽  
South American ◽  
The South ◽  
Passive Margins ◽  
Margin Width ◽  
Lithospheric Thickness ◽  
Lithospheric Thinning ◽  
Tectonic Features ◽  
And Diffusion

&lt;p&gt;In this contribution, we examine the evolution of the South Atlantic passive margins, based on a new thermal lithosphere-asthenosphere-boundary (LAB) model. Our model is calculated by 1D advection and diffusion with rifting time, crustal thickness and stretching factors as input parameters. The initial lithospheric thickness is defined by isostatic equilibrium with laterally variable crustal and mantle density. We simulate the different rifting stages that caused the opening of the South Atlantic Ocean and pick the LAB as the T=1330&amp;#176; C isotherm. The modelled LAB shows a heterogeneous structure with deeper values at equatorial latitudes, as well as a more variable lithosphere along the southern part. This division reflects different stages of the South Atlantic opening: Initial opening of the southern South Atlantic caused substantial lithospheric thinning, followed by the rather oblique-oriented opening of the equatorial South Atlantic accompanied by severe thinning. Compared to global models, our LAB reflects a higher variability associated with tectonic features on a smaller scale. As an example, we identify anomalously high lithospheric thickness in the South American Santos Basin that is only poorly observed in global LAB models. Comparing the LAB of the conjugate South American and African passive margins in a Gondwana framework reveals a variable lithospheric architecture for the southern parts. Strong differences up to 80 km for selected margin segments correlate with strong gradients in margin width for conjugate pairs. This mutual asymmetry suggests highly asymmetric melting and lithospheric thinning prior to rifting.&lt;/p&gt;

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