Surface Deformation in Iceland and Crustal Stress over a Mantle Plume

Author(s):  
Eysteinn Tryggvason
2021 ◽  
Author(s):  
Anna Gülcher ◽  
Laurent Montési ◽  
Taras Gerya ◽  
Jessica Munch

In the absence of global plate tectonics, mantle convection and plume-lithosphere interaction are the main drivers of surface deformation on Venus. Among documented tectonic structures, circular volcano-tectonic features known as coronae may be the clearest surface manifestations of mantle plumes and hold clues to the global Venusian tectonic regime. Yet, the exact processes underlying coronae formation and the reasons for their diverse morphologies remain controversial. Here, we use 3D thermomechanical numerical simulations of impingement of a thermal mantle plume upon the Venusian lithosphere to assess the origin and diversity of large Venusian coronae. The ability of the mantle plume to penetrate into the Venusian lithosphere results in four main outcomes: lithospheric dripping, short-lived subduction, embedded plume and plume underplating. During the first three scenarios, plume penetration and spreading induce crustal thickness variations that eventually lead to a final topographic isostasy-driven topographic inversion from circular trenches surrounding elevated interiors to raised rims surrounding inner depressions, as observed on many Venusian coronae. Different corona structures may represent not only different styles of plume-lithosphere interactions, but also different stages in evolution. A morphological analysis of large existing coronae leads to the conclusion that least 37 large coronae (including the largest Artemis corona) are active, providing evidence for widespread ongoing plume activity on Venus.


2020 ◽  
Author(s):  
Corné Kreemer ◽  
Geoffrey Blewitt ◽  
Paul Davis

<p> The Eifel hotspot is one of the few known active continental hotspots. The evidence is based on volcanism as recent as 11ka and a seismic velocity anomaly that shows a plume-like feature downward to at least the upper transition zone. However, the volcanism lacks a clear space-time progression of activity, and evidence for surface deformation has been ambiguous. Here, we show that the greater area above the Eifel plume shows a distinct and significant surface deformation anomaly not seen anywhere else in intraplate Europe. We use GPS data of thousands of stations in western Europe to image contemporary vertical land motion (VLM) and horizontal strain rates. We show significant surface uplift rates with a maximum of ~1.0 mm/yr (after subtracting the broader-scale VLM predicted by glacial isostatic adjustment) roughly centered on the Eifel Volcanic Field, and above the mantle plume. The same area that uplifts also undergoes significant N-S-oriented extension of ~3 nanostrain/yr, and this area is surrounded by a radial pattern of shortening. River terrace data have revealed tectonic uplift of <span>~</span>150–250 m of the Eifel since 800 ka, when recent volcanism and uplift reactivated, which would imply an average VLM of <span>0.1</span>–<span>0.3 mm/yr </span>since that time. Our VLM results suggest that the uplift may have accelerated significantly since Quaternary volcanism commenced. <span>The remarkable superimposition of significant uplift, horizontal extension, and volcanism strongly suggests a causal relationship with the underlying mantle plume. We</span><span> model the plume buoyancy as a half-space vertical force applied to a bi-modal Gaussian areal distribution exerted on a plane at 50 km depth. </span><span>Our modelling shows a good regional fit to the long-wavelength aspects of the surface deformation by applying buoyancy forces related to the plume head at the bottom of the lithosphere. From our spatially integrated force and the first-order assumption that the plume has effectively been buoyant since 250 ka (to explain Quaternary uplift) or 800 ka (at today’s rate), we estimate that a 360 km high plume requires density reduction of 57-184 kg m</span><sup><span>-3</span></sup><span> (i.e., ~0.7-5.6% of a 3300 kg m</span><sup><span>-3</span></sup><span> dense reference mantle), which is consistent with observed seismic velocity reductions. Finally, we note that the highest extension rates are centred on the Lower Rhine Embayment (LRE), where intraplate seismicity rates are high, and where paleoseismic events increased since 800 ka. We suggest that the surface uplift imposed by the Eifel plume explains the relatively high activity rate on faults along the LRE, particularly since the N-S extension would promote failure on the NW-SE trending faults in the LRE.</span></p>


2020 ◽  
Vol 222 (2) ◽  
pp. 1316-1332 ◽  
Author(s):  
Corné Kreemer ◽  
Geoffrey Blewitt ◽  
Paul M Davis

SUMMARY The volcanism of the Eifel volcanic field (EVF), in west-central Germany, is often considered an example of hotspot volcanism given its geochemical signature and the putative mantle plume imaged underneath. EVF's setting in a stable continental area provides a rare natural laboratory to image surface deformation and test the hypothesis of there being a thermally buoyant plume. Here we use Global Positioning System (GPS) data to robustly image vertical land motion (VLM) and horizontal strain rates over most of intraplate Europe. We find a spatially coherent positive VLM anomaly over an area much larger than the EVF and with a maximum uplift of ∼1 mm yr−1 at the EVF (when corrected for glacial isostatic adjustment). This rate is considerably higher than averaged over the Late-Quaternary. Over the same area that uplifts, we find significant horizontal extension surrounded by a radial pattern of shortening, a superposition that strongly suggests a common dynamic cause. Besides the Eifel, no other area in NW Europe shows significant positive VLM coupled with extensional strain rates, except for the much broader region of glacial isostatic adjustment. We refer to this 3-D deformation anomaly as the Eifel Anomaly. We also find an extensional strain rate anomaly near the Massif Central volcanic field surrounded by radial shortening, but we do not detect a significant positive VLM signal there. The fact that the Eifel Anomaly is located above the Eifel plume suggests that the plume causes the anomaly. Indeed, we show that buoyancy forces induced by the plume at the bottom of the lithosphere can explain this remarkable surface deformation. Plume-induced deformation can also explain the relatively high rate of regional seismicity, particularly along the Lower Rhine Embayment.


Vestnik MEI ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 101-108
Author(s):  
Anton Yu. Poroykov ◽  
◽  
Konstantin M. Lapitskiy ◽  

1997 ◽  
Author(s):  
H. Stahl ◽  
Kevin Stultz ◽  
H. Stahl ◽  
Kevin Stultz

2019 ◽  
Vol 486 (4) ◽  
pp. 460-465
Author(s):  
E. V. Sharkov ◽  
A. V. Chistyakov ◽  
M. M. Bogina ◽  
O. A. Bogatikov ◽  
V. V. Shchiptsov ◽  
...  

Tiksheozero ultramafic-alkaline-carbonatite intrusive complex, like numerous carbonatite-bearing complexes of similar composition, is a part of large igneous province, related to the ascent of thermochemical mantle plume. Our geochemical and isotopic data evidence that ultramafites and alkaline rocks are joined by fractional crystallization, whereas carbonatitic magmas has independent origin. We suggest that origin of parental magmas of the Tiksheozero complex, as well as other ultramafic-alkaline-carbonatite complexes, was provided by two-stage melting of the mantle-plume head: 1) adiabatic melting of its inner part, which produced moderately-alkaline picrites, which fractional crystallization led to appearance of alkaline magmas, and 2) incongruent melting of the upper cooled margin of the plume head under the influence of CO2-rich fluids  that arrived from underlying zone of adiabatic melting gave rise to carbonatite magmas.


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