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Evolution of stress fields during the supercontinent cycle

Geodesy and Geodynamics 2022年第4期13卷 363-375页

作者： Alexander Bobrov Alexey Baranov Robert Tenzer Schmidt Institute of Physics of the Earth Russian Academy of SciencesMoscowRussia Institute of Earthquake Prediction Theory and Mathematical Geophysics Russian Academy of SciencesMoscowRussia Department of Land Surveying and Geo-Informatics Hong Kong Polytechnic UniversityHong KongChina

We investigate the evolution of stress fields during the supercontinent cycle using the 2D Cartesian geometry model of thermochemical convection with the non-Newtonian rheology in the presence of floating deformable *** the course of the simulation,the supercontinent cycle is implemented several *** number of continents considered in our model as a function of time oscillates around *** lifetime of a supercontinent depends on its *** results suggest that immediately before a supercontinent breakup,the over-lithostatic horizontal stresses in it(referring to the mean value by the computational area)are tensile and can reach-250 *** the same time,a vast area beneath a supercontinent with an upward flow exhibits clearly the over-lithostatic compressive horizontal stresses of 50-100 МРа.The reason for the difference in stresses in the supercontinent and the underlying mantle is a sharp difference in their *** large parts of the mantle,the over-lithostatic horizontal stresses are in the range of±25 MPa,while the horizontal stresses along subduction zones and continental margins are significantly *** the process of continent-to-continent collisions,the compressive stresses can approximately reach 130 MPa,while within the subcontinental mantle,the tensile over-lithostatic stresses are about-50 *** dynamic topography reflects the main features of the su-percontinent cycle and correlates with real *** the breakup and immediately after the disin-tegration of the supercontinent,continents experience maximum *** the supercontinent cycle,topographic heights of continents typically vary within the interval of about±1.5 km,relatively to a mean *** maxima of orogenic formations to about 2-4 km are detected along continent-to-continent collisions as well as when adjacent subduction zones interact with continental margins.

关键词： supercontinent cycle Floating deformable continents Thermochemical convection Horizontal stresses Dynamic topography

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Refnement of the supercontinent cycle with Hf, Nd and Sr isotopes

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Geoscience Frontiers 2013年第6期4卷 667-680页

作者： Kent C.Condie Richard C.Aster Department of Earth and Environmental Science New Mexico Institute of Mining and Technology Geosciences Department Colorado State University

The combined use of Hf,Nd and Sr isotopes is more useful in understanding the supercontinent cycle than the use of only Hf isotopic data from detrital *** and Nd seawater isotopes,although not as precise as εNd and εHf distributions,also record input from ocean ridge *** detrital zircons where sources cannot be precisely located because of crustal recycling,both the location and tectonic setting often can be constrained for whole-rock Nd isotopic ***,primary zircon sources may not reside on the same continent as derivative detrital zircons due to supercontinent breakup and *** to all of the isotopic studies are geographic sampling biases reflecting outcrop distributions,river system sampling,or geologists,and these may be responsible for most of the decorrelation observed between isotopic *** between 3.5 and 2 Ga based on εHf median values of four detrital zircon databases as well as our compiled εNd database are noisy but uniformly distributed in time,whereas data between 2 and 1 Ga data are more tightly clustered with smaller *** age peaks suggest that both isotopic systems are sampling similar types of *** after 1 Ga and before 3.5 Ga do we see wide variations and significant disagreement between databases,which may partially reflect variations in both the number of sample locations and the number of samples per *** and internal orogens show similar patterns in εNd and εHfwith age suggesting that both juvenile and reworked crustal components are produced in both types of orogens with similar ***,both types of orogens clearly produce more juvenile isotopic signatures in retreating mode than in advancing *** secular changes in εHf and εNd distributions correlate with the supercontinent *** supercontinent breakup is correlated with short-lived decreasing εHf and εNd （≤ 100 Myr） for most supercontinents,there is no isotopic evidence for

关键词： supercontinent cycle Hf isotopes Nd isotopes Collisional orogens Accretionary orogens

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True polar wander in the Earth system

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Science China Earth Sciences 2023年第6期66卷 1165-1184页

作者： Chong WANG Ross N.MITCHELL State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

True polar wander(TPW),or planetary reorientation,is the rotation of solid Earth(crust and mantle)about the liquid outer core in order to stabilize Earth’s rotation due to mass *** TPW is well-documented on Earth presently with satellites and for multiple planets and moons in the Solar System,the prevalence of TPW in Earth history remains *** a history of controversy,both the physical plausibility of TPW on Earth and an empirical basis for it are now *** resistance to the old idea likely stems from the fact that,like plate tectonics,TPW may influence much of the Earth system,thus acknowledging its existence requires rethinking how many different datasets are *** review summarizes the development of TPW as a concept and provides a framework for future research that no longer regards TPW like a ghost process that may or may not exist,but as an integral part of the Earth system that can relate shallow and deep processes that are otherwise only mysteriously ***,we focus on the temporal regularity of large TPW,and discuss its relationship with the supercontinent-megacontinent cycle based on previous *** suggest the assembly of megacontinents has a close linkage to large ***,supercontinent tenure and breakup have a close linkage to fast *** effects of TPW on sea level changes,paleoclimate,biological diversity,and other facets of the Earth system are presented and require interdisciplinary tests in the future.

关键词： True polar wander(TPW) Planetary reorientation Apparent polar wander(APW) Mantle convection supercontinent cycle Megacontinent

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Will Earth's next supercontinent assemble through the closure of the Pacific Ocean?

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National Science Review 2022年第12期9卷 73-81页

作者： Chuan Huang Zheng-Xiang Li Nan Zhang Earth Dynamics Research Group The Institute for Geoscience Research(TIGeR) School of Earth and Planetary Sciences Curtin University Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking University

Earth’s known super continents are believed to have formed in vastly different ways,with two endmembers being introversion and *** former involves the closure of the internal oceans formed during the break-up of the previous supercontinent,whereas the latter involves the closure of the previous external super ***,it is unclear what caused such diverging behavior of supercontinent cycles that involved first-order interaction between subducting tectonic plates and the *** we address this question through 4D geo dynamic modeling using realistic tectonic *** results show that the strength of the oceanic lithosphere plays a critical role in determining the assembly path of a *** found that high oceanic lithospheric strength leads to introversion assembly,whereas lower strength leads to extroversion assembly.A theoretically estimated reduction in oceanic crustal thickness,and thus its strength,during Earth’s secular cooling indicates that introversion was only possible for the Precambrian time when the oceanic lithosphere was stronger,thus predicting the assembling of the next supercontinent Amasia through the closure of the Pacific Ocean instead of the Indian-Atlantic *** work provides a new understanding of the secular evolution of plate tectonics and geodynamics as the Earth cooled.

关键词： yield stress oceanic lithosphere introversion extroversion supercontinent cycle

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