GD1.6

EDI
Multi-disciplinary perspectives on plume-plate interactions and geodynamic influences on topography

Over fifty years since the acceptance of plate tectonic theory the driving forces behind plate motion and plate boundary formation and evolution remain incompletely understood. In addition to plate boundary forces, mantle plumes are often invoked as a trigger for processes such as continental rifting and break-up, subduction initiation, microcontinent formation, readjustments of the world-encircling mid-ocean ridge system, and topography evolution (called dynamic topography). Moreover, the arrival of mantle plume heads at the base of the lithosphere has been invoked as the mechanism behind abrupt, short-lived changes in plate speeds and azimuths, by means of the introduction of “plume-push” forces. However, the validity of this hypothesis has recently been put into question.

In this session, we aim to bring together researchers interested in the forces driving plate tectonics, with particular emphasis on plate-plume interactions and covering cover a range of techniques from data-driven approaches to numerical modelling or laboratory experiments We welcome studies that address the links between mantle dynamics, modern-style plate tectonics, whole-lithosphere behaviour and topography, through deep time as well as during the Archaen.

We expect this session to include a diverse range of multi-disciplinary studies united by a common goal of understanding the dynamics of plate motions, mantle plumes, the plate-mantle system. and the influence on the evolution of the topography.

Convener: Lucia Perez-DiazECSECS | Co-conveners: Maelis ArnouldECSECS, Hans-Peter Bunge, Anke Friedrich, Prof. Dr. Ulrich Anton Glasmacher, Francois Guillocheau, Maria SetonECSECS
vPICO presentations
| Mon, 26 Apr, 09:00–10:30 (CEST)

vPICO presentations: Mon, 26 Apr

Chairpersons: Lucia Perez-Diaz, Prof. Dr. Ulrich Anton Glasmacher
09:00–09:05
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EGU21-13169
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ECS
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solicited
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Highlight
Kimberly Huppert, J. Taylor Perron, Leigh Royden, and Michael Toomey

Geologic evidence of island uplift and subsidence can provide important observational constraints on the rheology, thermal evolution, and dynamics of the lithosphere and mantle – all of which have implications for understanding Earth’s heat budget, the styles of deformation that develop at plate boundaries, and the surface expression of mantle convection. Hotspot ocean islands, like the Hawaiian Islands, result from mantle plumes, which may originate as deep as the core-mantle boundary. They often host paleoshorelines, which preserve a geologic record of surface deformation, and they can also be situated far from complex plate boundaries that obscure evidence of dynamic topography – long wavelength, low amplitude topography resulting from mantle flow. Ocean islands therefore provide a unique window to deep earth processes operating today and in the geologic past.

We examine the relative contribution of lithosphere and mantle processes to surface deflection at ocean hotspots. The seafloor surrounding ocean hotspots is typically 0.5 - 2 km shallower than expected for its age over areas hundreds to >1000 km wide, but the processes generating these bathymetric swells are uncertain. Swells may result from reheating and thinning of the lithosphere and the isostatic effect of replacing colder, denser lithosphere with hotter, less dense upper mantle. Alternately, they may be supported by upward flow of ascending mantle plumes and/or hot, buoyant plume material ponded beneath the lithosphere. Because these two end-member models predict different patterns of seafloor and island subsidence, swell morphology and the geologic record of island drowning may reveal which of these mechanisms dominates the process of swell uplift. We examine swell bathymetry and island drowning at 14 hotspots and find a correspondence between island lifespan and residence time atop swell bathymetry, implying that islands drown as tectonic plate motion transports them past mantle sources of uplift. This correspondence argues strongly for dynamic uplift of the lithosphere at ocean hotspots. Our results also explain global variations in island lifespan on fast- and slow-moving tectonic plates (e.g. drowned islands in the Galápagos <4 Myr old versus islands >20 Myr old above sea level in the Canary Islands), which strongly influence island topography, biodiversity, and climate.

Over shorter timescales, paleoshorelines on hotspot ocean islands may constrain transient changes in local swell morphology. Accounting for flexural isostatic adjustment of the lithosphere to volcanic loading, we also examine patterns in the residual deflection of paleoshorelines across the Hawaiian Islands that might correspond to non-steady state behavior of the Hawaiian plume. Together, these analyses highlight the unique constraints that island paleoshorelines and topo-bathymetry can place on plume-plate interactions at ocean hotspots.

How to cite: Huppert, K., Perron, J. T., Royden, L., and Toomey, M.: Characterizing plume-plate interactions at ocean hotspots from the vertical motion history of volcanic ocean islands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13169, https://doi.org/10.5194/egusphere-egu21-13169, 2021.

09:05–09:07
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EGU21-13277
Plume-induced subduction and plate fracturation, deep mantle overturn, and the onset of plate tectonics.
(withdrawn)
Anne Davaille
09:07–09:09
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EGU21-546
Douwe J. J. van Hinsbergen, Bernhard Steinberger, Carl Guilmette, Marco Maffione, Derya Gürer, Kalijn Peters, Alexis Plunder, Peter McPhee, Carmen Gaina, Eldert Advokaat, Reinoud Vissers, and Wim Spakman

The formation of a global network of plate boundaries surrounding a mosaic of lithospheric fragments was a key step in the emergence of Earth’s plate tectonics. So far, propositions for plate boundary formation are regional in nature but how plate boundaries are being created over 1000s of km in short periods of geological time remains elusive. Here, we show from geological observations that a >12,000 km long plate boundary formed between the Indian and African plates around 105 Ma with subduction segments from the eastern Mediterranean region to a newly established India-Africa rotation pole in the west-Indian ocean where it transitioned into a ridge between India and Madagascar. We find no plate tectonics-related potential triggers of this plate rotation and identify coeval mantle plume rise below Madagascar-India as the only viable driver. For this, we provide a proof of concept by torque balance modeling revealing that the Indian and African cratonic keels were important in determining plate rotation and subduction initiation in response to the spreading plume head. Our results show that plumes may provide a non-plate-tectonic mechanism for large plate rotation initiating divergent and convergent plate boundaries far away from the plume head that may even be an underlying cause of the emergence of modern plate tectonics.

How to cite: van Hinsbergen, D. J. J., Steinberger, B., Guilmette, C., Maffione, M., Gürer, D., Peters, K., Plunder, A., McPhee, P., Gaina, C., Advokaat, E., Vissers, R., and Spakman, W.: A record of plume-induced plate rotation triggering seafloor spreading and subduction initiation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-546, https://doi.org/10.5194/egusphere-egu21-546, 2021.

09:09–09:11
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EGU21-7763
Marzieh Baes, Stephan Sobolev, Taras Gerya, Robert Stern, and Sascha Brune

Subduction zones are key components of plate tectonics and plate tectonics could not begin until the first subduction zone formed. Plume-induced subduction initiation, which has been proposed as triggering the beginning of plate tectonics (Gerya et al., 2015), is one of the few scenarios that can break the lithosphere and recycle a stagnant lid without requiring any pre-existing weak zones. So far, two natural examples of plume-induced subduction initiation have been recognized. The first was found in southern and western margins of the Caribbean Plate (Whattam and Stern 2014). Initiation of the Cascadia subduction zone in Eocene times has been proposed to be the second example of plume-induced subduction initiation (Stern and Dumitru, 2019).

The focus of previous studies was to inspect plume-lithosphere interaction either for the case of stationary lithosphere (e.g., Gerya et al., 2015) or for moving lithosphere without considering the effect of lithospheric magmatic weakening above the plume head (e.g., Moore et al., 1998). In present study we investigate the response of moving oceanic lithosphere to the arrival of a rising mantle plume head including the effect of magmatic lithospheric weakening. We used 3D numerical thermo-mechanical modeling. Using I3ELVIS code, which is based on finite difference staggered grid and marker-in-cell with an efficient OpenMP multigrid solver (Gerya, 2010), we show that plate motion may affect the plume-induced subduction initiation only if a moderate size plume head (with a radius of 140 km in our experiments) impinges on a young but subductable lithosphere (with the age of 20 Myr). Outcomes indicate that lithospheric strength and plume buoyancy are key parameters in penetration of the plume and subduction initiation and that plate speed has a minor effect. We propose that eastward motion of the Farallon plate in Late Cretaceous time could play a key role in forming new subduction zones along the western and southern margin of the Caribbean plate.

 

References:

Gerya, T., 2010, Introduction to Numerical Geodynamic Modelling.. Cambridge University Press.

Gerya, T.V., Stern, R.J., Baes, M., Sobolev, S.V. and Whattam, S.A., 2015. Plume-induced subduction initiation triggered Plate Tectonics on Earth. Nature, 527, 221–225.

Moore, W. B., Schubert, G. and Tackley, P., 1998, Three-dimensional simulations of plume-lithosphere interaction at the Hawaiian swell. Science, 279, 1008-1011.

Stern, R.J., and Dumitru, T.A., 2019, Eocene initiation of the Cascadia subduction zone: A second example of plume-induced subduction initiation? Geosphere, v. 15, 659-681.

Whattam, S.A. and Stern, R.J., 2014. Late Cretaceous plume-induced subduction initiation along the southern margin of the Caribbean and NW South America: The first documented example with implications for the onset of plate tectonics. Gondwana Research, 27, doi: 10.1016/j.gr.2014.07.011.

How to cite: Baes, M., Sobolev, S., Gerya, T., Stern, R., and Brune, S.: Effect of plate motion on plume-induced subduction initiation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7763, https://doi.org/10.5194/egusphere-egu21-7763, 2021.

09:11–09:13
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EGU21-3726
Jyotirmoy Paul and Attreyee Ghosh

One of the fundamental characteristics of cratons is the presence of thick lithosphere of more than 200 km, whereas any standard non-cratonic lithosphere thickness is about 100 km thick. The thickness of Indian craton has remained quite controversial. Under the Indian plate, most seismic studies fail to recognise a thick lithosphere; however, a few studies using other geophysical methods (e.g., magnetotellurics) argue for a thick Indian craton. In the last 30 years, more than ten research articles estimated the thickness of the Indian craton that varied from less than 100 km to 260 km. Such controversy arose primarily because of the Reunion plume and Indian craton interaction at ~65 Ma. Some studies suggested that due to the Reunion plume's eruption underneath the Indian craton, the thick lithosphere of the Indian craton was thinned down. This thin lithosphere is attributed as one of the primary reasons for the acceleration of the Indian plate since 65 Ma. On the other hand, several studies advocated that the Reunion plume did not affect the thickness of the Indian craton. Still now, no study has actually investigated the nature of plume-craton interaction under the Indian plate and how the craton was deformed in the presence of a plume. In this study, we develop time-dependent global mantle convection models using CitcomS to understand the evolution of Indian craton for the last 100 Ma. The models are initiated at 100 Ma and are driven forward  up to the present day using reconstructed plate velocities at every 1 Myr interval. Our results show that it is possible to thin down the thicker cratonic lithosphere due to the eruption of the Reunion plume. We also observe that the plume could get bifurcated due to the craton, and eruptions could occur on both the eastern and western parts of the Indian continental lithosphere.

How to cite: Paul, J. and Ghosh, A.: Interaction of the Indian craton with the Reunion plume, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3726, https://doi.org/10.5194/egusphere-egu21-3726, 2021.

09:13–09:15
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EGU21-8496
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Highlight
Graeme Eagles, Lucía Pérez Díaz, and Karin Sigloch

Observations of the apparent links between plate speeds and the global distribution of plate boundary types have led to the suggestion that subduction may provide the largest component in the balance of torques maintaining plate motions. This would imply that plate speeds should not exceed the sinking rates of slabs into the upper mantle. Instances of this ‘speed limit’ having been broken may thus hint at the existence of driving mechanisms additional to those resulting from plate boundary forces. The arrival and emplacement of the Deccan-Réunion mantle plume beneath the Indian-African plate boundary in the 67-62 Ma period has been discussed in terms of one such additional driving mechanism, leading to the establishment of “plume-push” hypothesis, which in recent years has gained significant traction. We challenge the model-based observations that form the principal evidence in favour of plume-push: a late Cretaceous pulse of anticorrelating accelerations and decelerations in seafloor spreading rates around the African and Indian plates. Using existing and newly-calculated high-resolution models of plate motion, we instead document an increase in divergence rates at 67-64 Ma. Because of its ubiquity, we consider this increase to be the artefact of a timescale error affecting chrons 29-28. Corrected for this artefact, the evolution of plate speeds resembles a smooth continuation of pre-existing late Cretaceous trends, consistent with the idea that the arrival of the Réunion plume did not substantially affect the existing balance of plate boundary forces on the Indian and African plates. 

How to cite: Eagles, G., Pérez Díaz, L., and Sigloch, K.: No signal of a plume push force in Indo-Atlantic plate speeds before, during, or after Deccan plume arrival, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8496, https://doi.org/10.5194/egusphere-egu21-8496, 2021.

09:15–09:17
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EGU21-4669
Marianne Greff-Lefftz, Isabelle Panet, and Jean Besse

Hotspots are thermal instabilities that originate in the mantle and manifest themselves on the surface by volcanism, continental breaks or "traces" observed in the oceans. Theirs effects under the continents are still debated: in addition to a phase of activity associated with surface volcanism, a residual thermal anomaly could persist durably under the lithosphere along the trajectory of the hotspot.
For a simple model of thermal anomaly (parallelogram aligned in a fixed direction), we compute the perturbations of the geoid, of the gravity vector and of the associated gravity gradients. We show that in a coordinate system aligned with the parallelogram, gravity gradients have a characteristic signal with an order of magnitude of a few hundred mEotvos, well above the current data detection level. Thus for four real cases: in North Africa (with the Hoggar, Tibesti, Darfur and Cameroon hotspots), in Greenland (Iceland and Jan Mayen), in Australia (Cosgrove) and in Europe (Eifel), we calculate the paleo-positions of the hotspots during the last 100 Ma in a reference frame linked to the lithospheric plates, and we build maps of gravity gradients at different altitudes filtered at the spatial scale of a few hundred kilometers (scale of the hotspot) and oriented along the direction of the trajectory.
We clearly find signals aligned in the direction of the movement of the plates on spatial scales of a few hundred kilometers.
This signal is sometimes correlated with the topography and it is difficult to separate the sources resulting from volcanic edifices and their associated isostatic crustal roots from that induced by residual thermal anomaly. These results show that gradiometric data are able to detect and follow the tracks of hotspots in the continental lithosphere, during at least a few tens of millions of years, providing new clues to constrain their trajectory and improve reference frame tied to the mantle.

How to cite: Greff-Lefftz, M., Panet, I., and Besse, J.: Continental Hotspots Tracks from Analysis of GOCE Gravity Gradients Data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4669, https://doi.org/10.5194/egusphere-egu21-4669, 2021.

09:17–09:19
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EGU21-6857
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ECS
Ben Mather, Dietmar Muller, Maria Seton, Saskia Ruttor, Oliver Nebel, and Nick Mortimer

Long-lived, widespread intraplate volcanism without age progression is one of the most controversial features of plate tectonics. The eastern margin of Australia and Zealandia has experienced extensive mafic volcanism over the last 100 million years. A plume origin has been proposed for three distinct chains of volcanoes, however, the majority of eruptions exhibit no clear age progression. Previously proposed edge-driven convection, asthenospheric shear, and lithospheric detachment fail to explain the non age-progressive eruptions across the ~5000 km wide intraplate volcanic province from Eastern Australia to Zealandia. We model the subducted slab volume over 100 million years and find that slab flux drives volcanic eruption frequency, indicating stimulation of an enriched mantle transition zone reservoir. Volcanic isotope geochemistry allows us to distinguish a HIMU reservoir (>1 Ga old) in the slab-poor south, from a northern EM1/EM2 reservoir, reflecting a more recent voluminous influx of oceanic lithosphere into the mantle transition zone. We provide a unified theory linking plate boundary and slab volume reconstructions to upper mantle reservoirs and intraplate volcano geochemistry.

How to cite: Mather, B., Muller, D., Seton, M., Ruttor, S., Nebel, O., and Mortimer, N.: Intraplate volcanism triggered by bursts in slab flux, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6857, https://doi.org/10.5194/egusphere-egu21-6857, 2021.

09:19–09:21
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EGU21-7279
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Highlight
Hilmar von Eynatten, Jonas Kley, and István Dunkl

Large parts of Central Europe have experienced exhumation in Late Cretaceous to Paleogene time. Previous studies mainly focused on thrusted basement uplifts to unravel magnitude, processes and timing of exhumation. In this study we present a comprehensive thermochronological dataset from mostly Permo-Triassic strata exposed adjacent to and between the major basement uplifts in central Germany, comprising an area of at least some 250-300 km across. Results of apatite fission track and (U-Th)/He analyses from >100 new samples reveal that (i) km-scale exhumation affected the entire region, suggesting long-wavelength domal uplift, (ii) thrusting of basement blocks like the Harz Mountains and the Thuringian Forest focused in the Late Cretaceous (about 90-70 Ma) while superimposed domal uplift of central Germany appears slightly younger (about 75-55 Ma), and (iii) large parts of the domal uplift experienced removal of 3 to 4 km of Mesozoic strata. Using spatial extent, magnitude and timing as constraints we find that thrusting and crustal thickening alone can account for no more than half of the domal uplift. Most likely, dynamic topography caused by upwelling asthenosphere has contributed significantly to the observed pattern of exhumation in central Germany.

How to cite: von Eynatten, H., Kley, J., and Dunkl, I.: Late Cretaceous to Paleogene exhumation in Central Europe – localized inversion vs. large-scale domal uplift, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7279, https://doi.org/10.5194/egusphere-egu21-7279, 2021.

09:21–09:23
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EGU21-8199
The post-Caledonian thermo-tectonic evolution of Fennoscandia
(withdrawn)
Peter Japsen, Paul F. Green, Johan M. Bonow, James A. Chalmers, Ian Duddy, and Ilmo Kokkunen
09:23–09:25
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EGU21-10188
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ECS
Angela Maria Gomez Garcia, Eline Le Breton, Magdalena Scheck-Wenderoth, Gaspar Monsalve, and Denis Anikiev

Remnants of the Caribbean Large Igneous Plateau (C-LIP) are found as thickened zones of oceanic crust in the Caribbean Sea, that formed during strong pulses of magmatic activity around 90 Ma. Previous studies have proposed the Galápagos hotspot as the origin of the thermal anomaly responsible for the development of this igneous province. Particularly, geochemical signature relates accreted C-LIP fragments along northern South America with the well-known hotspot material.

In this research, we use 3D lithospheric-scale structural and density models of the Caribbean region, in which up-to-date geophysical datasets (i.e.: tomographic data, Moho depths, sedimentary thickness, and bathymetry) have been integrated. Based on the gravity residuals (modelled minus observed EIGEN6C-4 dataset), we reconstruct density heterogeneities both in the crust and the uppermost oceanic mantle (< 50km).

Our results suggest the presence of two positive mantle density anomalies in the Colombian and the Venezuelan basins, interpreted as the preserved plume material which migrated together with the Proto-Caribbean plate from the east Pacific. Such bodies have never been identified before, but a positive density trend is also observed in the mantle tomography, at least down to 75 km depth.

Using recently published regional plate kinematic models and absolute reference frames, we test the hypothesis of the C-LIP origin in the Galápagos hotspot. However, misfits of up to ~3000 km between the present hotspot location and the mantle anomalies, reconstructed back to 90 Ma, is observed, as other authors reported in the past.

Therefore, we discuss possible sources of error responsible for this offset and pose two possible interpretations: 1. The Galápagos hotspot migrated (~1200-3000 km) westward while the Proto-Caribbean moved to the northeast, or 2. The C-LIP was formed by a different plume, which – if considered fixed - would be nowadays located below the South American continent.

How to cite: Gomez Garcia, A. M., Le Breton, E., Scheck-Wenderoth, M., Monsalve, G., and Anikiev, D.: The preserved plume conduits of the Caribbean Large Igneous Plateau and their relation with the Galápagos hotspot back to 90 Ma, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10188, https://doi.org/10.5194/egusphere-egu21-10188, 2021.

09:25–09:27
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EGU21-10964
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ECS
Niklas Ahlrichs, Vera Noack, Christian Hübscher, and Elisabeth Seidel

Within the DFG project StrucFlow, we investigate the multiphase character of Late Cretaceous to Cenozoic inversion in the Baltic sector of the North German Basin based on seismic interpretation. Our analysis rests upon modern high-resolution seismic profiles in combination with data from older seismic surveys and borehole information. The resulting seismic database consists of a dense profile network with a total length of some 10.000 km. This unprecedented seismic grid allows for a detailed tectono-stratigraphic interpretation of Cretaceous and Paleogene deposits in the Baltic sector of the North German Basin. Here, basin inversion began in the Coniacian and Santonian with uplift of the Grimmen High and minor reactivation of Zechstein salt structures. Crestal faults were formed or reactivated above salt pillows in the Bays of Mecklenburg and Kiel. The onset of inversion was contemporaneous with other adjacent basins and is likewise associated with building up intraplate stress within the European foreland related to the beginning Africa-Iberia-Europe convergence. Time-isopach maps of Paleocene deposits in the study area show a slight decrease in thickness to the west. This contrasts the prevailing trend of increasing thickness towards the southwest directed basin center and indicates a changed depositional environment. In the outer eastern Glückstadt Graben, increased thicknesses and diverging strata of late Eocene and Oligocene units indicate significant remobilization of salt structures during this time. Preexisting Triassic faults above the salt pillows “Schleimünde” and “Kieler Bucht” at the eastern border of the Glückstadt Graben were reactivated and form a north-south trending crestal graben filled with Paleogene sediments. This phase of salt remobilization is contemporaneous with the reintroduction of intraplate stress triggered by the Alpine and Pyrenean orogenies in the late Eocene. In the eastern Bay of Kiel and in the Bay of Mecklenburg, Late Eocene and younger sediments are largely absent due to Neogene uplift and erosion. Deepening of rim-synclines and synchronous infill of Paleogene strata give evidence for commencing salt pillow growth. Crestal faults pierce the Paleocene and Eocene strata, indicating salt movement at least during the later Eocene. This phase of salt movement occurred contemporaneously with salt remobilization in the Glückstadt Graben, initiation of the European Cenozoic Rift System and increased activity in the Alpine realm in the Late Eocene to Oligocene. We conclude that the rise of salt pillows since the Eocene significantly exceeds the growth during late Cretaceous to Paleocene inversion phase at the northeastern North German Basin.

How to cite: Ahlrichs, N., Noack, V., Hübscher, C., and Seidel, E.: Multiphase inversion in the Baltic sector of the North German Basin: Influence of Africa-Iberia-Europe convergence during the Late Cretaceous and Cenozoic, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10964, https://doi.org/10.5194/egusphere-egu21-10964, 2021.

09:27–09:29
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EGU21-11155
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ECS
Pankaj Kumar, Pratyush Anand, Dibakar Ghosal, and Pabitra Singha

The Amsterdam-St. Paul (ASP) island complex is a manifestation of interaction between the South-East Indian Ridge (SEIR) and the ASP mantle plume, which was formed ~10 Ma. Very few geophysical studies have been conducted over the ASP island complex and therefore we have limited information about the island so far. We performed an integrated geophysical approach using gravity, magnetic study along with the joint inversion of Ps receiver function and Rayleigh wave group velocity dispersion curve to determine the crustal architecture and Moho variation in the region. The result of integrated gravity-magnetic modeling revealed that the island complex is associated with three crustal layers beneath the sedimentary strata. Inversion of Rayleigh wave group velocity dispersion curve accounts for vertical shear wave velocity average which supported the layered velocity profile. The results revealed that magnetic material (Mid oceanic ridge basalt/Flood basalt) has carpeted the entire island causing high magnetic anomaly of -1000 to 1500 nT, which is generated by gradual accumulation of a thick pile of magnetic material of normal as well as reverse polarity. The results by integrated Gravity-magnetic model suggest that crust beneath the island is suggested to be highly affected by volcanic activity (Mantle Plume/Ridge) and is underlain by high-density underplated material. The results further suggest that SEIR has less role for the outpoured magmatic activity. Integrated Gravity-magnetic model show that Moho is variable beneath the island complex and lies in the range of ~12-17 km. Further results by joint inversion of Ps receiver function and Rayleigh wave group velocity dispersion curve for the station (AIS : Nouvelle Amsterdam - TAAF, France) suggest Moho depth of ~14 km beneath the Amsterdam island and is well in agreement with the gravity-magnetic studies. The result clearly indicates that ASP island complex is highly affected by the ASP plume activity and was evolved during the ridge-plume interaction.

How to cite: Kumar, P., Anand, P., Ghosal, D., and Singha, P.: Crustal architecture of Amsterdam-St. Paul Island from an integrated geophysical approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11155, https://doi.org/10.5194/egusphere-egu21-11155, 2021.

09:29–09:31
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EGU21-12123
Eva Wegerer, Nicolai Aust, and Anton Mayer

Mineral fillers can significantly affect the application properties of plastic materials. The structural and chemical properties of phyllosilicates provide the conditions to change the properties of polymeric material, e.g. flexural and tensile strength or thermal properties, according to the required application. Mineral fillers frequently used are clay minerals with a two-layer structure (serpentine-kaolin group) or three-layer structure (talc-pyrophyllite group, mica group, smectite group). The mineral fillers can be directly used or after surface modification, depending on the polar nature of the polymer. Polymers containing polar groups (hydrophilic polymers) are water-soluble, like polyvinyl alcohols and polysaccharides or can form hydrogen bonds, like polyamides, polyesters and polyvinyl fluorides. Hydrophobic (non-polar) polymers show an absence of polar groups (e.g. polyethylene, polypropylene) or mutual cancelling electrical dipole moments (e.g. polytetrafluorethylene). Minerals with a hydrophilic surface are directly applicable with polar polymers. For the application with non-polar polymers their surface require hydrophobization, whereas non-polar two-layer silicates are directly applicable with these polymers.

Serpentinized rock material is investigated with regard to its suitability as a polymer filler and its influence on the performance characteristics of various polymers. The samples origin from the Kraubath Ultramafic Massif, which represents part of an Early Paleozoic ophiolite, at the basement of the Austro-Alpine. The Kraubath complex is dominated by metamorphosed dunites and harzburgites, which origin from fractionation processes of the primary peridotite magma. Hydrothermal alteration led to a partly or entirely serpentinization of the ultramafic rocks. The serpentinization process of dunite, ortho-pyroxenite and harzburgite transformed Mg-containing silicates, like olivine and pyroxene to serpentine group minerals. Rock material with a high grade of serpentinization offers favourable conditions for the application as mineral filler.

The qualitative and quantitative XRD-analyses reveal a predominant occurrence of the antigorite. Further serpentine group minerals, like lizardite, occur in small amounts. Talc represents the second largest mineral phase. The rock material contains a few percentage of amphibole, chlorite, olivine (forsterite) and less than two percent of chromite and bronzite. In the two-layer structure of the main component antigorite, the charge of the tetrahedral layer is compensated by the charge of the octahedral layer. The three-layer structure of talc is electrostatically neutral, with no interlayer material. Therefore, serpentine minerals and talc are suitable for the application as mineral fillers in non-polar polymers, like polypropylene. Both influence the mechanical and tribological properties of polymers. Serpentine improves elasticity, tensile strength, stress at break, elongation at break, the mass wear rate and the coefficient of friction of the polymer but reduces the impact strength. Talc positively influences rigidity, shrinkage, creep properties, heat distortion under load and the coefficient of linear thermal expansion, however reduces toughness, long thermal ageing, impact strength and tensile strength. The further mineral phases are not considered to affect the application properties negatively. Regarding tensile strength and elasticity the ratio of serpentine to talc can influence the increase and decrease of these properties in non-polar polymers. The applicability of the practical implementation is investigated with nanoparticles of the serpentinized rock material in combination with polypropylene in varying proportions.

How to cite: Wegerer, E., Aust, N., and Mayer, A.: Suitability of serpentinized rock material as mineral filler in polymer matrices, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12123, https://doi.org/10.5194/egusphere-egu21-12123, 2021.

09:31–09:33
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EGU21-12348
Frédéric Mouthereau and Paul Angrand

The heterogeneous continental lithosphere of Europe inherits billion of years of tectonic evolution, mineral transformation and magmatic addition. Though there is now an extensive body of studies on the long-term geological, geochronological and geochemical evolution of the continental crust and lithospheric mantle available in Europe, yet this knowledge has not been linked to the understanding of tectonic evolution of Cenozoic Alpine mountain building. In this aim, we review geophysical, geological, petrographical, geochemical, and thermochronological constraints to infer a kinematically coherent time-integrated tectonic model for the evolution of mountain building in Western Europe, along a 4000 km long lithospheric transect from Africa to the East European Craton. We show that the key drivers of plate-scale processes related to  Alpine orogenic and topographic evolution reflect three main ingredients : 1) a protracted magmatic and tectono-thermal transformation of Africa (Gondwana) and North Europea (Baltica) cratonic mantle lithosphere since the Neoproterozoic, 2) an overall limited Mesozoic Tethyan extension of the weak Variscan lithosphere characterized by the lack of wide, thermally relaxed, oceanic lithosphere, 3) a relatively slow Cenozoic convergence between Africa and Europe, preserving initial stages of distributed tectonic inversion of rifted continental blocks throughout Europe, and partial subduction and delamination in the Mediterranean region of the most evolved lithospheric domains. 

How to cite: Mouthereau, F. and Angrand, P.: Cenozoic mountain building of Western Europe controlled by continental lithosphere evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12348, https://doi.org/10.5194/egusphere-egu21-12348, 2021.

09:33–09:35
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EGU21-13087
Francois Guillocheau and Cécile Robin

Western Europe experienced a major rift system initiated during Bartonian times (41 Ma). This evolution is coeval with long wavelength deformations (several hundreds of kilometers) that control the topography and the sediment production beyond the rift. The climate during this time interval was first increasingly arid and then wetter.

This study is based on both landform and sediment analysis of southern England, France, Belgium and western Germany. The landforms are mainly large pediments, dated by the intersection with sediments deposited in low to high subsiding areas and volcanism. A set of paleogeographic maps with paleotopographic reconstructions, is used to constrain the uplifting and subsiding areas, their wavelength and the critical periods of intraplate deformations.

The main periods of deformations and sedimentary systems changes area as follow.

41Myrs (base Bartonian) was the beginning of a major tilting of Western Europe with subsidence of France and uplift of the Brabant/Ardennes/Rhenish Massif. Even a dense network of basement faults was reactivated, biochemical sedimentation prevailed.

35-31Myrs (Late Priabonian-Early Rupelian) initiated a period of general subsidence even along the Ardennes/Rhenish Massif and the French Massif Central. Two major marine floodings are recorded, with a differential preservation according to the balance between deformation and eustasy.

27-25Myrs (Chattian) was a period of uplift of Western Europe except the Aquitaine Basin, followed by a relaxation favoring eustatic floodings in (very) low subsiding domains. Chattian siliciclastic deposits are preserved as lowstand wedges in the surrounded basins (North Sea, Atlantic Margin).

14-11Myrs (Serravallian-Early Tortonian) initiated the overall uplift of Western Europe, still operating today. This is the beginning of a period of major denudation in southern England, Western Germany (SW Germany flat - “Stufenland”) and along the southern limb of the Franch Massif Central.

The causes and the consequences in term of sediment production are discussed.

How to cite: Guillocheau, F. and Robin, C.: Intraplate deformations, topographic evolution and sediment production of Western Europe from 40 to 5 Myrs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13087, https://doi.org/10.5194/egusphere-egu21-13087, 2021.

09:35–09:37
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EGU21-13129
Christoph Leitner

The evaporitic Haselgebirge Formation hosts in many places small occurrences of basaltic rocks. The geochemistry of these basalts can potentially provide information about the tectonic setting of the Haselgebirge Formation and the evolution of the Meliata ocean, respectively. We present here 70 new XRF analyses of these basaltic rocks from various localities (Pfennigwiese, Annaberg, Wienern, Hallstatt, Moosegg, Lammertal) and compare the results with previous data from local studies (GRUBER et al., 1991; KIRCHNER 1979; KIRCHNER 1980a; KIRCHNER 1980b; KRALIK et al, 1984; LEITNER et al., 2017; SCHORN et al., 2013; ZIEGLER, 2014; ZIRKL, 1957). Based on the concentrations of immobile trace elements (Zr, Nb, Y, Ti), a predominance of MORB-like compositions is observed for the Lower Austrian occurrences and for the locality Wienern (Grundlsee). On contrast, basalts from the localities Lammertal, Moosegg and Hallstatt have predominantly within-plate-type compositions.

We discuss this striking regional (east-west) difference of basalt types in terms of existing palinspastic models for the Haselgebirge formation (LEITNER et al., 2017; STAMPFLI & BOREL, 2002; McCANN et al., 2006).

 

GRUBER, P., FAUPL, P., KOLLER, F. (1991) Mitt. Österr. Miner. Ges., 84, 77-100.

KIRCHNER, E. (1979) Tschermaks Min. Petr. Mitt. 26, 149-162.

KIRCHNER, E. (1980a) Mitt. Österr. Miner. Ges.71/72, 385-396.

KIRCHNER, E. (1980b) Verh. Geol. Bundesanstalt 1980, 249-279.

KRALIK, M., KOLLER, F., POBER, E. (1984) Mitt. Österr. Miner. Ges., 77, 37-55.

LEITNER, C., WIESMAIER, S., KÖSTER, M.H., GILG, H.A, FINGER, F, NEUBAUER, F. (2017) GSA Bulletin 129, 1537-1553.

McCANN, T., PASCAL, C., TIMMERMAN, M.J., KRZYWIEC, P., LÓPEZ-GÓMEZ, J., WETZEL, L., KRAWCZYK, C.M., RIEKE, H., LAMARCH, J. (2006) Mem. Geol. Soc. London, 32, 355-388.

SCHORN A, NEUBAUER F, GENSER J, BERNROIDER M (2013) Tectonophysics 583, 28-48.

STAMPFLI G.M., BOREL G.D. (2002) Earth Planet. Sci. Lett. 196, 17-33.

ZIEGLER, T. (2014) Unpubl. MSc thesis University of Salzburg, p. 174.

ZIRKL, E.J. (1957) Jb. Geol. Bundesanstalt 100, 10-137-177.

How to cite: Leitner, C.: Two different basalt provinces (MORB vs. WPB) in the evaporitic Permian Haselgebirge Formation (Eastern Alps, Austria) and possible tectonic implications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13129, https://doi.org/10.5194/egusphere-egu21-13129, 2021.

09:37–09:39
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EGU21-13383
Piotr Krzywiec, Łukasz Słonka, Quang Nguyen, Michał Malinowski, Mateusz Kufrasa, Aleksandra Stachowska, Christian Huebscher, and Regina Kramarska

In 2016, approximately 850 km of high-resolution multichannel seismic reflection data of the BALTEC survey have been acquired offshore Poland within the transition zone between the East European Craton and the Paleozoic Platform. Data processing, focused on removal of multiples, strongly overprinting geological information at shallower intervals, included SRME, TAU-P domain deconvolution, high resolution parabolic Radon demultiple and SWDM (Shallow Water De-Multiple). Entire dataset was Kirchhoff pre-stack time migrated. Additionally, legacy shallow high-resolution multichannel seismic reflection data acquired in this zone in 1997 was also used. All this data provided new information on various aspects of the Phanerozoic evolution of this area, including Late Cretaceous to Cenozoic tectonics and sedimentation. This phase of geological evolution could be until now hardly resolved by analysis of industry seismic data as, due to limited shallow seismic imaging and very strong overprint of multiples, essentially no information could have been retrieved from this data for first 200-300 m. Western part of the BALTEC dataset is located above the offshore segment of the Mid-Polish Swell (MPS) – large anticlinorium formed due to inversion of the axial part of the Polish Basin. BALTEC seismic data proved that Late Cretaceous inversion of the Koszalin – Chojnice fault zone located along the NE border of the MPS was thick-skinned in nature and was associated with substantial syn-inversion sedimentation. Subtle thickness variations and progressive unconformities imaged by BALTEC seismic data within the Upper Cretaceous succession in vicinity of the Kamień-Adler and the Trzebiatów fault zones located within the MPS documented complex interplay of Late Cretaceous basin inversion, erosion and re-deposition. Precambrian basement of the Eastern, cratonic part of the study area is overlain by Cambro-Silurian sedimentary cover. It is dissected by a system of steep, mostly reverse faults rooted in most cases in the deep basement. This fault system has been regarded so far as having been formed mostly in Paleozoic times, due to the Caledonian orogeny. As a consequence, Upper Cretaceous succession, locally present in this area, has been vaguely defined as a post-tectonic cover, locally onlapping uplifted Paleozoic blocks. New seismic data, because of its reliable imaging of the shallowest substratum, confirmed that at least some of these deeply-rooted faults were active as a reverse faults in latest Cretaceous – earliest Paleogene. Consequently, it can be unequivocally proved that large offshore blocks of Silurian and older rocks presently located directly beneath the Cenozoic veneer must have been at least partly covered by the Upper Cretaceous succession; then, they were uplifted during the widespread inversion that affected most of Europe. Ensuing regional erosion might have at least partly provided sediments that formed Upper Cretaceous progradational wedges recently imaged within the onshore Baltic Basin by high-end PolandSPAN regional seismic data. New seismic data imaged also Paleogene and younger post-inversion cover. All these results prove that Late Cretaceous tectonics substantially affected large areas located much farther towards the East than previously assumed.

This study was funded by the Polish National Science Centre (NCN) grant no UMO-2017/27/B/ST10/02316.

How to cite: Krzywiec, P., Słonka, Ł., Nguyen, Q., Malinowski, M., Kufrasa, M., Stachowska, A., Huebscher, C., and Kramarska, R.: Late Cretaceous – Cenozoic history of the transition zone between the East European Craton and the Paleozoic Platform, Polish sector of the Baltic Sea, revealed by new offshore regional seismic reflection data (BALTEC project), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13383, https://doi.org/10.5194/egusphere-egu21-13383, 2021.

09:39–09:41
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EGU21-13784
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ECS
Bing Zhao, Xijun Liu, Zhenglin Li, Wenmin Huang, and Chuan Zhao

The Emeishan flood basalts are part of an important large igneous province along the western margin of the Yangtze Block, Southwest China. The western Guangxi region in southwestern China is geologically a part of the Yangtze Block. Mafic rocks, comprising mainly lavas and dykes in western Guangxi belong to the outer part of the ~260 Ma Emeishan Large Igneous Province (ELIP). Here we present a systematic study of platinum-group elements (PGEs) combined with the LA-ICP-MS zircon U–Pb age, whole-rock geochemical and isotopic data of the lavas and dykes in the Longlin area of outer zone of ELIP to constraints on their origin. On the basis of petrography and major elements characteristics, mafic lavas and dykes display an enrichment of LREE, LILE, HFSE, high (87Sr/86Sr)i ratios (0.704227~0.705754), low εNd(t) values(0.42~0.99), high εHf(t) values(5.19~6.04), they are similar to those of Permian Emeishan high-Ti basalts and Ocean island basalts (OIB) features. The Longlin mafic rocks was formed in the Late Permian with the zircon U-Pb dated age of 256.3± 1.7 Ma. The age of the Longlin mafic rocks is close to the formation age of the ELIP large-scale magmatism, suggesting that these lavas and dykes probably belongs to part of the ELIP large-scale magmatism. The Longlin mafic rocks have low total PGE contents ranging from 1.56×10-9 to 2.28×10-9, with Os, Ir, Ru, Rh, Pt and Pd contents of 0.040~0.076, 0.046~0.076, 0.027~0.079, 0.037~0.056, 0.6374~1.053 and 0.715~1.021ppb, respectively. They show left-leaning primitive mantle-normalized PGE patterns with depletion in Iridium group(IPGE) and enrichment in Palladium group, which also have lower contents than mafic rocks from the inner zone of the ELIP, suggesting that a low degree of partial melting of the mantle source plays an important role. The Longlin mafic rocks exhibit a marked increase in Cu/Pd ratios (>105,84655 to 174785) albeit with a narrow range of lower Pd/Ir ratios (<50,13.4 to 18.7), different from the PGE-enriched basalts of the Siberian Traps, Emeishan Large Igneous Province (ELIP), East Greenland CFBs and Deccan Traps, indicating that their parent magmas was significantly depleted in chalcophile elements. Calculations based on the available trace element geochemistry reveal that the basalts were originated by low degree of partial melting(<5%),with sulfides remain in the mantle during partial melting. Sulfide segregation could not happen during the evolution of the Longlin mafic rocks, due to the fact that neither significant fractional crystallization nor crustal contamination has been involved in their formation. Overall, mafic rocks from the outer zone of the ELIP show lower PGE contents than those in the inner zones, we find that the PGE contents in igneous rocks are related with the degrees of partial melting in the mantle source and the removal of sulfides before their emplacement.

This study was financially supported by the Guangxi Natural Science Foundation for Distinguished Young Scholars (2018GXNSFFA281009) and the Fifth Bagui Scholar Innovation Project of Guangxi Province (to XU Ji-feng).

How to cite: Zhao, B., Liu, X., Li, Z., Huang, W., and Zhao, C.: Geochronology, isotopic and Platinum-group elemental geochemistry of lavas and dykes from the western Guangxi in outer zone of Emeishan mantle plume, SW China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13784, https://doi.org/10.5194/egusphere-egu21-13784, 2021.

09:41–09:43
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EGU21-14385
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Highlight
Hans Thybo, Nevra Bulut, Michael Grund, Alexandra Mauerberger, Anna Makushkina, Irina Artemieva, Niels Balling, Olafur Gudmundsson, Valerie Maupin, Lars Ottemøller, Joachim Ritter, and Frederik Tilmann

The Baltic Shield is located in northern Europe. It was formed by amalgamation of a series of terranes and microcontinents during the Archean to the Paleoproterozoic, followed by significant modification in Neoproterozoic to Paleozoic time. The Baltic Shield includes a high mountain range, the Scandes, along its western North Atlantic coast, despite being a stable craton located far from any active plate boundary.

The ScanArray international collaborative program has acquired broad band seismological data at 192 locations in the Baltic Shield during the period between 2012 and 2017. The main objective of the program is to provide seismological constraints on the structure of the lithospheric crust and mantle as well as the sublithospheric upper mantle. The new information will be applied to studies of how the lithospheric and deep structure affects observed fast topographic change and geological-tectonic evolution of the region. The recordings are of very high quality and are used for analysis by suite of methods, including P- and S-wave receiver functions for the crust and upper mantle, surface wave and ambient noise inversion for seismic velocity, body wave P- and S- wave tomography for upper mantle velocity structure, and shear-wave splitting measurements for obtaining bulk anisotropy of the upper and lower mantle. Here we provide a short overview of the data acquisition and initial analysis of the new data with focus on parameters that constrain the fast topographic change in the Scandes.

 

How to cite: Thybo, H., Bulut, N., Grund, M., Mauerberger, A., Makushkina, A., Artemieva, I., Balling, N., Gudmundsson, O., Maupin, V., Ottemøller, L., Ritter, J., and Tilmann, F.: ScanArray - Seismological study of the connection between topographic change and deep structure in Fennoscandia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14385, https://doi.org/10.5194/egusphere-egu21-14385, 2021.

09:43–10:30