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M. Santosh - One of the best experts on this subject based on the ideXlab platform.
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Tracking India Within Precambrian Supercontinent Cycles
Geodynamics of the Indian Plate, 2020Co-Authors: Sarbani Patranabis-deb, Dilip Saha, M. SantoshAbstract:The term Supercontinent generally implies grouping of formerly dispersed continents and/or their fragments in a close packing accounting for about 75% of earth’s landmass in a given interval of geologic time. The assembly and disruption of Supercontinents rely on plate tectonic processes, and therefore, much speculation is involved particularly considering the debates surrounding the applicability of differential plate motion, the key to plate tectonics during the early Precambrian. The presence of Precambrian orogenic belts in all major continents is often considered as the marker of ancient collisional or accretionary sutures, which provide us clues to the history of periodic assembly of ancient Supercontinents. Testing of any model assembly/breakup depends on precise age data and paleomagnetic pole reconstruction. The record of dispersal of the continents and release of enormous stress lie in extensional geological features, such as rift valleys, regionally extensive flood basalts, granite-rhyolite terrane, anorthosite complexes, mafic dyke swarms, and remnants of ancient mid-oceanic ridges.
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High-temperature granulites and Supercontinents
Geoscience Frontiers, 2016Co-Authors: Jacques L.r. Touret, M. Santosh, Jan Marten HuizengaAbstract:The formation of continents involves a combination of magmatic and metamorphic processes. These processes become indistinguishable at the crust-mantle interface, where the pressure-temperature (P-T) conditions of (ultra) high-temperature granulites and magmatic rocks are similar. Continents grow laterally, bymagmatic activity above oceanic subduction zones (high-pressure metamorphic setting), and vertically by accumulation of mantle-derived magmas at the base of the crust (high-temperature metamorphic setting). Both events are separated from each other in time; the vertical accretion postdating lateral growth by several tens of millions of years. Fluid inclusion data indicate that during the high-temperature metamorphic episode the granulite lower crust is invaded by large amounts of low H2O-activity fluids including high-density CO2 and concentrated saline solutions (brines). These fluids are expelled from the lower crust to higher crustal levels at the end of the high-grade metamorphic event. The final amalgamation of Supercontinents corresponds to episodes of ultra-high temperature metamorphism involving large-scale accumulation of these low-water activity fluids in the lower crust. This accumulation causes tectonic instability, which together with the heat input from the subcontinental lithospheric mantle, leads to the disruption of Supercontinents. Thus, the fragmentation of a Supercontinent is already programmed at the time of its amalgamation
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1 23 ga mafic dykes in the north china craton and their implications for the reconstruction of the columbia Supercontinent
Gondwana Research, 2015Co-Authors: Wei Wang, M. Santosh, Yue Zhao, Shuwen Liu, Lifei Zhang, Xiang Bai, Shuanhong Zhang, Rongrong GuoAbstract:Abstract The Proterozoic world was shaped by the Paleo-Mesoproterozoic Columbia and Neoproterozoic Rodinia Supercontinents. The North China Craton (NCC) is an integral component of Columbia Supercontinent assembly, but the lack of rock records in the transitional period between Columbia and Rodinia in the late Mesoproterozoic (1.3–1.2 Ga) has resulted in its exclusion from models that trace the Columbia–Rodinia transition. The paleogeographic position of the NCC is also elusive, with India, Baltica, and Siberia as potential neighbors during the early evolution of Columbia. Here we report the discovery of a suite of ~ 1.23 Ga mafic dykes covering an area of ~ 0.6 × 10 6 km 2 of the NCC. These mafic rocks can be classified into both alkaline and subalkaline groups. The former group may have been derived from lower degrees of partial melting of a depleted asthenospheric mantle with limited involvement of a lithospheric mantle component, whereas the latter group can be modeled by higher degrees of partial melting of a subduction-modified enriched lithospheric mantle. Considering the large areal extent of the 1.23 Ga mafic dykes, and their dominantly OIB (Ocean Island Basalt)-like geochemical features, a Mesoproterozoic mantle plume regime is invoked for the NCC. Compiling information on global ~ 1.27–1.21 Ga mafic dykes, flood basalts and layered intrusions, we establish a Mesoproterozoic hotspot track, and consider the NCC to have been located between Laurentia and Baltica. Combined with recent paleomagnetic and geological data, we infer that the Laurentia–NCC–Baltica connection may have existed since the late Paleoproterozoic. We further propose that both plate tectonic (introversion or extroversion) and mantle plume regimes played vital roles during the Supercontinent transition.
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Mantle plumes, Supercontinents, intracontinental rifting and mineral systems
Precambrian Research, 2015Co-Authors: Franco Pirajno, M. SantoshAbstract:Abstract The formation and disruption of Supercontinents exert major influence on mantle dynamics and have important bearing on continental dynamics and mineral systems. Here we evaluate the role of mantle plumes in the rifting and breakup of Supercontinents with specific examples involving Columbia, Rodinia and Gondwana. We attempt to trace the formation of associated rift systems and the making of mineral deposits in the processes from failed rifts (aulacogens) to successful rifts. Models on the rifting and breakup of Supercontinents through mantle upwellings range from ‘thermal blanket’ effect and Supercontinent self-destruction through plumes rising from the mantle transition zone at the 410–660 km boundary layer to superplumes generated at the core–mantle boundary with subducted slabs acting as the fuel. Intracontinental rifts are potential sites of giant ore systems, such as sedimentary exhalative (SEDEX), stratiform, stratabound and Fe oxide-Cu-Au-U (IOCG) deposits. The age span of these ore systems (∼1.6–0.8 Ga) broadly corresponds with the assembly and dispersal of the Palaeoproterozoic Supercontinent Columbia, followed by the amalgamation of the Neoproterozoic Rodinia and its subsequent breakup. The Phanerozoic Pangea Supercontinent at 260 Ma had two main components, Laurasia in the north and Gondwana in the south, separated by the Palaeotethys Ocean. We focus on the rifting of Gondwana, which led to the formation of present day Atlantic and Indian oceans. Thus, rift systems effectively act as major conduits for both magmas and hydrothermal fluids. Intracontinental rifts host magmatic and hydrothermal mineral deposits including Ni-Cu and Ti-Fe±V and Cu-Ni±PGE deposits in mantle-sourced mafic–ultramafic rocks, U-REE-Nb-Cu sourced from metasomatised subcontinental lithospheric mantle, and hydrothermal Sn-W, among other types. Upwelling plumes and their migration beneath trans-crustal faults or lithospheric discontinuities drive hydrothermal factories channelling heat and fluids and generating economic ore deposits.
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Large igneous provinces linked to Supercontinent assembly
Journal of Geodynamics, 2015Co-Authors: Yu Wang, M. Santosh, Zhaohua Luo, Jinhua HaoAbstract:Abstract Models for the disruption of Supercontinents have considered mantle plumes as potential triggers for continental extension and the formation of large igneous provinces (LIPs). An alternative hypothesis of top-down tectonics links large volcanic eruptions to lithospheric delamination. Here we argue that the formation of several LIPs in Tarim, Yangtze, Lhasa and other terranes on the Eurasian continent was coeval with the assembly of the Pangean Supercontinent, in the absence of plumes rising up from the mantle transition zone or super-plumes from the core–mantle boundary. The formation of these LIPs was accompanied by subduction and convergence of continents and micro-continents, with no obvious relation to major continental rifting or mantle plume activity. Our model correlates LIPs with lithospheric extension caused by asthenospheric flow triggered by multiple convergent systems associated with Supercontinent formation.
J. Brendan Murphy - One of the best experts on this subject based on the ideXlab platform.
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The role of megacontinents in the Supercontinent cycle
Geology, 2020Co-Authors: Chong Wang, Ross N. Mitchell, J. Brendan Murphy, Peng Peng, Christopher J. SpencerAbstract:Abstract Supercontinent Pangea was preceded by the formation of Gondwana, a “megacontinent” about half the size of Pangea. There is much debate, however, over what role the assembly of the precursor megacontinent played in the Pangean Supercontinent cycle. Here we demonstrate that the past three cycles of Supercontinent amalgamation were each preceded by ∼200 m.y. by the assembly of a megacontinent akin to Gondwana, and that the building of a megacontinent is a geodynamically important precursor to Supercontinent amalgamation. The recent assembly of Eurasia is considered as a fourth megacontinent associated with future Supercontinent Amasia. We use constraints from seismology of the deep mantle for Eurasia and paleogeography for Gondwana to develop a geodynamic model for megacontinent assembly and subsequent Supercontinent amalgamation. As a Supercontinent breaks up, a megacontinent assembles along the subduction girdle that encircled it, at a specific location where the downwelling is most intense. The megacontinent then migrates along the girdle where it collides with other continents to form a Supercontinent. The geometry of this model is consistent with the kinematic transitions from Rodinia to Gondwana to Pangea.
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Supercontinents: myths, mysteries, and milestones
Geological Society London Special Publications, 2018Co-Authors: Daniel Pastor-galán, J. Brendan Murphy, R. Damian Nance, Christopher J. SpencerAbstract:AbstractThere is an emerging consensus that Earth's landmasses amalgamate quasi-periodically into Supercontinents, interpreted to be rigid super-plates essentially lacking tectonically active inner boundaries and showing little internal lithosphere–mantle interactions. The formation and disruption of Supercontinents have been linked to changes in sea-level, biogeochemical cycles, global climate change, continental margin sedimentation, large igneous provinces, deep mantle circulation, outer core dynamics and Earth's magnetic field. If these hypotheses are correct, long-term mantle dynamics and much of the geological record, including the distribution of natural resources, may be largely controlled by these cycles. Despite their potential importance, however, many of these proposed links are, to date, permissive rather than proven. Sufficient data are not yet available to verify or fully understand the implications of the Supercontinent cycle. Recent advances in many fields of geoscience provide clear directions for investigating the Supercontinent cycle hypothesis and its corollaries but they need to be vigorously pursued if these far-reaching ideas are to be substantiated.
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Supercontinents and the case for Pannotia
Geological Society London Special Publications, 2018Co-Authors: R. Damian Nance, J. Brendan MurphyAbstract:AbstractDisagreement about the existence of the late Neoproterozoic Supercontinent Pannotia highlights the limitation of defining Supercontinents simply on the basis of size, which, for pre-Pangaean Supercontinents, is difficult to determine. In the context of the Supercontinent cycle, however, Supercontinent assembly and break-up, respectively, mark the end of one cycle and the beginning of the next and can be recognized by the tectonic, climatic and biogeochemical trends that accompany them. Hence Supercontinents need only be large enough to influence mantle circulation in such a way as to enable the cycle to repeat. Their recognition need not rely solely on continental reconstructions, but can also exploit a variety of secular trends that accompany their amalgamation and break-up. Although the palaeogeographical and age constraints for the existence of Pannotia remain equivocal, the proxy signals of Supercontinent assembly and break-up in the late Neoproterozoic are unmistakable. These signals cannot be readily attributed to either the break-up of Rodinia or the assembly of Gondwana without ignoring either the assembly phase of Pan-African orogenesis and the changes in mantle circulation that accompany this phase, or the reality that Gondwana cannot be a Supercontinent in the context of the Supercontinent cycle because its break-up coincides with that of Pangaea.
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The Supercontinent cycle: A retrospective essay
Gondwana Research, 2014Co-Authors: R. Damian Nance, J. Brendan Murphy, M. SantoshAbstract:Abstract The recognition that Earth history has been punctuated by Supercontinents, the assembly and breakup of which have profoundly influenced the evolution of the geosphere, hydrosphere, atmosphere and biosphere, is arguably the most important development in Earth Science since the advent of plate tectonics. But whereas the widespread recognition of the importance of Supercontinents is quite recent, the concept of a Supercontinent cycle is not new and advocacy of episodicity in tectonic processes predates plate tectonics. In order to give current deliberations on the Supercontinent cycle some historical perspective, we trace the development of ideas concerning long-term episodicity in tectonic processes from early views on episodic orogeny and continental crust formation, such as those embodied in the chelogenic cycle, through the first realization that such episodicity was the manifestation of the cyclic assembly and breakup of Supercontinents, to the surge in interest in Supercontinent reconstructions. We then chronicle some of the key contributions that led to the cycle's widespread recognition and the rapidly expanding developments of the past ten years.
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Whither the Supercontinent cycle
Geology, 2013Co-Authors: J. Brendan MurphyAbstract:The concept of episodicity in tectonic processes pre-dates acceptance of the plate tectonic paradigm (e.g., Umbgrove, 1940; Holmes, 1951; Sutton, 1963). It was specifi cally advocated by Wilson (1966) when he made the case that ocean basins repeatedly opened and closed, a process now known as “Wilson cycles” (Dewey and Burke, 1974). The relationship between tectonic episodicity and the Supercontinent cycle was fi rst proposed by Worsley et al. (1982, 1984), who argued that episodic peaks in the number of continental collisions refl ect Supercontinent amalgamation, and that episodes of rift-related mafi c dike swarms record Supercontinent breakup. These authors identifi ed trends in tectonic activity, platform development, climate, life and stable isotopes that accompanied Supercontinent amalgamation, breakup and dispersal (Nance et al. 2013). Although not universal (e.g., Stern, 2008), a broad consensus has emerged over the past 30 years that repeated cycles of Supercontinent amalgamation and dispersal occurred since the late Archean, with profound effect on the evolution of the Earth’s geosphere, hydrosphere, atmosphere and biosphere. Statistical peaks in the age distributions of orogenic granites and detrital zircons, as well as negative e Hf excursions in zircons may match the timing of Supercontinent amalgamation. As Hf is the more incompatible element, Lu/Hf is lower in the crust and higher in the depleted mantle relative to the bulk earth, and the crust therefore evolves towards negative eHf values. Whether these eHf data imply episodicity, a preservational bias, or a combination of both phenomena is debated (e.g., Roberts, 2012; Cawood et al., 2013; Nance et al., 2013). The mechanisms potentially responsible for the Supercontinent
Joseph G. Meert - One of the best experts on this subject based on the ideXlab platform.
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Strange attractors, spiritual interlopers and lonely wanderers: The search for pre-Pangean Supercontinents
Geoscience Frontiers, 2014Co-Authors: Joseph G. MeertAbstract:Abstract The observation is made that there are very strong similarities between the Supercontinents Columbia, Rodinia and Pangea. If plate tectonics was operating over the past 2.5 billion years of Earth history, and dominated by extroversion and introversion of ocean basins, it would be unusual for three Supercontinents to resemble one another so closely. The term ‘strange attractor’ is applied to landmasses that form a coherent geometry in all three Supercontinents. Baltica, Laurentia and Siberia form a group of ‘strange attractors’ as do the elements of East Gondwana (India, Australia, Antarctica, Madagascar). The elements of “West Gondwana” are positioned as a slightly looser amalgam of cratonic blocks in all three Supercontinents and are referred to as ‘spiritual interlopers’. Relatively few landmasses (the South China, North China, Kalahari and perhaps Tarim cratons) are positioned in distinct locations within each of the three Supercontinents and these are referred to as ‘lonely wanderers’. There may be several explanations for why these Supercontinents show such remarkable similarities. One possibility is that modern-style plate tectonics did not begin until the late Neoproterozoic and horizontal motions were restricted and a vertical style of ‘lid tectonics’ dominated. If motions were limited for most of the Proterozoic, it would explain the remarkable similarities seen in the Columbia and Rodinia Supercontinents, but would still require the strange attractors to rift, drift and return to approximately the same geometry within Pangea. A second possibility is that our views of older Supercontinents are shaped by well-known connections documented for the most recent Supercontinent, Pangea. It is intriguing that three of the four ‘lonely wanderers’ (Tarim, North China, South China) did not unite until just before, or slightly after the breakup of Pangea. The fourth ‘lonely wanderer’, the Kalahari (and core Kaapvaal) craton has a somewhat unique Archean-age geology compared to its nearest neighbors in Gondwana, but very similar to that in western Australia.
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what s in a name the columbia paleopangaea nuna Supercontinent
Gondwana Research, 2012Co-Authors: Joseph G. MeertAbstract:article Supercontinents play an important role in Earth's history. The exact definition of what constitutes a super- continent is difficult to establish. Here the argument is made, using Pangaea as a model, that any superconti- nent should include ~75% of the preserved continental crust relevant to the time of maximum packing. As an example, Rodinia reached maximum packing at about 1.0 Ga and therefore should include 75% of all conti- nental crust older than 1.0 Ga. In attempting to 'name' any Supercontinent, there is a clear precedent for models that provide a name along with a testable reconstruction within a reasonable temporal framework. Both Pangaea and Rodinia are near universally accepted names for the late Paleozoic and Neoproterozoic su- percontinent respectively; however, there is a recent push to change the Paleo-Mesoproterozoic superconti- nent moniker from "Columbia" to "Nuna". A careful examination of the "Nuna" and "Columbia" proposals reveals that although the term "Nuna" was published prior to "Columbia", the "Nuna" proposal is a bit nebu- lous in terms of the constitution of the giant continent. Details of "Nuna" given in the original manuscript ap- pear to be principally based on previously published connections between Laurentia, Baltica and, to a lesser extent the Angara craton of Siberia (i.e. "the lands bordering the northern oceans"). Therefore the proposal is made that "Columbia" consists of several core elements one of which is "Nuna".
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The making and unmaking of a Supercontinent: Rodinia revisited
Tectonophysics, 2003Co-Authors: Joseph G. Meert, Trond H. TorsvikAbstract:Abstract During the Neoproterozoic, a Supercontinent commonly referred to as Rodinia, supposedly formed at ca. 1100 Ma and broke apart at around 800–700 Ma. However, continental fits (e.g., Laurentia vs. Australia–Antarctica, Greater India vs. Australia–Antarctica, Amazonian craton [AC] vs. Laurentia, etc.) and the timing of break-up as postulated in a number of influential papers in the early–mid-1990s are at odds with palaeomagnetic data. The new data necessitate an entirely different fit of East Gondwana elements and western Gondwana and call into question the validity of SWEAT, AUSWUS models and other variants. At the same time, the geologic record indicates that Neoproterozoic and early Paleozoic rift margins surrounded Laurentia, while similar-aged collisional belts dissected Gondwana. Collectively, these geologic observations indicate the breakup of one Supercontinent followed rapidly by the assembly of another smaller Supercontinent (Gondwana). At issue, and what we outline in this paper, is the difficulty in determining the exact geometry of the earlier Supercontinent. We discuss the various models that have been proposed and highlight key areas of contention. These include the relationships between the various ‘external’ Rodinian cratons to Laurentia (e.g., Baltica, Siberia and Amazonia), the notion of true polar wander (TPW), the lack of reliable paleomagnetic data and the enigmatic interpretations of the geologic data. Thus, we acknowledge the existence of a Rodinia Supercontinent, but we can place only loose constraints on its exact disposition at any point in time.
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Paleomagnetic Evidence for a Paleo-Mesoproterozoic Supercontinent Columbia
Gondwana Research, 2002Co-Authors: Joseph G. MeertAbstract:Abstract Pre-Pangea Supercontinents have been proposed for Neoproterozoic and earlier times. Most of the configurations are based on analyses of geologic and structural evidence, but the only quantitative method for testing the proposed configurations is paleomagnetism. Unfortunately, the current paleomagnetic database is of limited use in evaluating the notion of a Paleo-Mesoproterozoic Supercontinent due to a lack of well-dated sequential poles from the various cratonic nuclei. This paper examines the available data and shows that Laurentia could not have been a part of a Supercontinent at 1.77 Ga, but it may have formed the core of a pre-Rodinia continent at 1.5 Ga. The available data do not preclude the existence of a Paleo-Mesoproterozoic Supercontinent, but they do suggest that it must be younger than 1.77 Ga.
Ross N. Mitchell - One of the best experts on this subject based on the ideXlab platform.
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Archean geodynamics: Ephemeral Supercontinents or long-lived supercratons
Geology, 2021Co-Authors: Yebo Liu, Ross N. Mitchell, Uwe Kirscher, Sergei A. Pisarevsky, Chong WangAbstract:Many Archean cratons exhibit Paleoproterozoic rifted margins, implying they were pieces of some ancestral landmass(es). The idea that such an ancient continental assembly represents an Archean Supercontinent has been proposed but remains to be justified. Starkly contrasting geological records between different clans of cratons have inspired an alternative hypothesis where cratons were clustered in multiple, separate “supercratons.” A new ca. 2.62 Ga paleomagnetic pole from the Yilgarn craton of Australia is compatible with either two successive but ephemeral Supercontinents or two long-lived supercratons across the Archean-Proterozoic transition. Neither interpretation supports the existence of a single, long-lived Supercontinent, suggesting that Archean geodynamics were fundamentally different from subsequent times (Proterozoic to present), which were influenced largely by Supercontinent cycles.
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The role of megacontinents in the Supercontinent cycle
Geology, 2020Co-Authors: Chong Wang, Ross N. Mitchell, J. Brendan Murphy, Peng Peng, Christopher J. SpencerAbstract:Abstract Supercontinent Pangea was preceded by the formation of Gondwana, a “megacontinent” about half the size of Pangea. There is much debate, however, over what role the assembly of the precursor megacontinent played in the Pangean Supercontinent cycle. Here we demonstrate that the past three cycles of Supercontinent amalgamation were each preceded by ∼200 m.y. by the assembly of a megacontinent akin to Gondwana, and that the building of a megacontinent is a geodynamically important precursor to Supercontinent amalgamation. The recent assembly of Eurasia is considered as a fourth megacontinent associated with future Supercontinent Amasia. We use constraints from seismology of the deep mantle for Eurasia and paleogeography for Gondwana to develop a geodynamic model for megacontinent assembly and subsequent Supercontinent amalgamation. As a Supercontinent breaks up, a megacontinent assembles along the subduction girdle that encircled it, at a specific location where the downwelling is most intense. The megacontinent then migrates along the girdle where it collides with other continents to form a Supercontinent. The geometry of this model is consistent with the kinematic transitions from Rodinia to Gondwana to Pangea.
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Coupled Supercontinent–mantle plume events evidenced by oceanic plume record
Geology, 2019Co-Authors: Luc Serge Doucet, Richard E. Ernst, Uwe Kirscher, Hamed Gamal El Dien, Ross N. MitchellAbstract:Abstract The most dominant features in the present-day lower mantle are the two antipodal African and Pacific large low-shear-velocity provinces (LLSVPs). How and when these two structures formed, and whether they are fixed and long lived through Earth history or dynamic and linked to the Supercontinent cycles, remain first-order geodynamic questions. Hotspots and large igneous provinces (LIPs) are mostly generated above LLSVPs, and it is widely accepted that the African LLSVP existed by at least ca. 200 Ma beneath the Supercontinent Pangea. Whereas the continental LIP record has been used to decipher the spatial and temporal variations of plume activity under the continents, plume records of the oceanic realm before ca. 170 Ma are mostly missing due to oceanic subduction. Here, we present the first compilation of an Oceanic Large Igneous Provinces database (O-LIPdb), which represents the preserved oceanic LIP and oceanic island basalt occurrences preserved in ophiolites. Using this database, we are able to reconstruct and compare the record of mantle plume activity in both the continental and oceanic realms for the past 2 b.y., spanning three Supercontinent cycles. Time-series analysis reveals hints of similar cyclicity of the plume activity in the continent and oceanic realms, both exhibiting a periodicity of ∼500 m.y. that is comparable to the Supercontinent cycle, albeit with a slight phase delay. Our results argue for dynamic LLSVPs where the Supercontinent cycle and global subduction geometry control the formation and locations of the plumes.
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Decoding Earth’s rhythms: Modulation of Supercontinent cycles by longer superocean episodes
Precambrian Research, 2019Co-Authors: Ross N. Mitchell, Christopher J. Spencer, Uwe Kirscher, Richard E. Ernst, Sergei Pisarevsky, J. B. MurphyAbstract:Abstract The Supercontinent cycle of episodic assembly and breakup of almost all continents on Earth is commonly considered the longest period variation to affect mantle convection. However, global zircon Hf isotopic signatures and seawater Sr isotope ratios suggest the existence of a longer-term variation trend that is twice the duration of the Supercontinent cycle. Here we propose that since ∼2 billion years ago the superocean surrounding a Supercontinent, as well as the circum-Supercontinent subduction girdle, survive every second Supercontinent cycle. This interpretation is in agreement with global palaeogeography and is supported by variations in passive margin, orogen, and mineral deposit records that each exhibits both ∼500–700 million years periodic signal and a 1000–1500 million years variation trend. We suggest that the Supercontinent cycle is modulated by an assembly that alternates between dominantly extroversion after a more complete breakup, and dominantly introversion after an incomplete breakup of the previous Supercontinent.
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True polar wander and Supercontinent cycles: Implications for lithospheric elasticity and the triaxial earth
American Journal of Science, 2014Co-Authors: Ross N. MitchellAbstract:The amplitude of true polar wander events is shown to occur in cycles out of phase with the formation of Supercontinents over the past 3 Gyr. Associated with small-amplitude true polar wander, Supercontinents act to stabilize the spin axis. Stabilization can be explained by reduced lithospheric elasticity and/or the triaxial (oblate) figure of the Earth, both of which are legacies of the Supercontinent cycle. An excess triaxial ellipticity would only be expected to affect the first transition between Supercontinents, whereas decreased lithospheric elasticity would have also influenced formation of the first Supercontinent, if sizable enough. My analysis indicates the presence of 4 Supercontinents since 3 Ga and proposes that the triaxial Earth originates from the Supercontinent cycle.
Kent C. Condie - One of the best experts on this subject based on the ideXlab platform.
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Chapter 7 – The Supercontinent Cycle
Earth as an Evolving Planetary System, 2016Co-Authors: Kent C. CondieAbstract:This chapter reviews methods of Supercontinent reconstruction and the processes involved in Supercontinent assembly and breakup. It reviews problems associated with identifying the first Supercontinent in the late Archean, and briefly reviews the history of later Supercontinents Nuna, Rodinia, and Gondwana-Pangea. It discusses the episodicity of U/Pb zircon ages and its relationship to Supercontinent formation and breakup and to large igneous province (LIP) events. The relationships of the Supercontinent cycle to mineral deposits, Sr isotopes of seawater, sea level variations, and organic evolution are also summarized. Mantle LIP events are discussed as are possible relationships and feedbacks between various climatic regimes, the carbon cycle, and the Supercontinent cycle.
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Is the rate of Supercontinent assembly changing with time
Precambrian Research, 2015Co-Authors: Kent C. Condie, Sergei Pisarevsky, Jun Korenaga, Steve GardollAbstract:Abstract To address the question of secular changes in the speed of the Supercontinent cycle, we use two major databases for the last 2.5 Gyr: the timing and locations of collisional and accretionary orogens, and average plate velocities as deduced from paleomagnetic and paleogeographic data. Peaks in craton collision occur at 1850 and 600 Ma with smaller peaks at 1100 and 350 Ma. Distinct minima occur at 1700–1200, 900–700, and 300–200 Ma. There is no simple relationship in craton collision frequency or average plate velocity between Supercontinent assemblies and breakups. Assembly of Nuna at 1700–1500 Ma correlates with very low collision rates, whereas assemblies of Rodinia and Gondwana at 1000–850 and 650–350 Ma, respectively correspond to moderate to high rates. Very low collision rates occur at times of Supercontinent breakup at 2200–2100, 1300–1100, 800–650, and 150–0 Ma. A peak in plate velocity at 450–350 Ma correlates with early stages of growth of Pangea and another at 1100 Ma with initial stages of Rodinia assembly following breakup of Nuna. A major drop in craton numbers after 1850 Ma corresponds with the collision and suturing of numerous Archean blocks. Orogens and passive margins show the same two cycles of ocean basin closing: an early cycle from Neoarchean to 1900 Ma and a later cycle, which corresponds to the Supercontinent cycle, from 1900 Ma to the present. The cause of these cycles is not understood, but may be related to increasing plate speeds during Supercontinent assembly and whether or not long-lived accretionary orogens accompany Supercontinent assembly. LIP (large igneous province) age peaks at 2200, 2100, 1380 (and 1450?), 800, 300, 200 and 100 Ma correlate with Supercontinent breakup and minima at 2600, 1700–1500, 1100–900, and 600–400 Ma with Supercontinent assembly. Other major LIP age peaks do not correlate with the Supercontinent cycle. A thermochemical instability model for mantle plume generation can explain all major LIP events by one process and implies that LIP events that correspond to the Supercontinent cycle are independent of this cycle. The period of the Supercontinent cycle is highly variable, ranging from 500 to 1000 Myr if the late Archean supercratons are included. Nuna has a duration of about 300 Myr (1500–1200 Ma), Rodinia 100 Myr (850–750 Ma), and Gondwana–Pangea 200 Myr (350–150 Ma). Breakup durations are short, generally 100–200 Myr. The history of angular plate velocities, craton collision frequency, passive margin histories, and periodicity of the Supercontinent cycle all suggest a gradual speed up of plate tectonics with time.
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Refinement of the Supercontinent cycle with Hf, Nd and Sr isotopes
Geoscience Frontiers, 2013Co-Authors: Kent C. Condie, Richard C. AsterAbstract:Abstract 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 zircons. Sr and Nd seawater isotopes, although not as precise as ɛ Nd and ɛ Hf distributions, also record input from ocean ridge systems. Unlike 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 data. Furthermore, primary zircon sources may not reside on the same continent as derivative detrital zircons due to Supercontinent breakup and assembly. Common 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 systems. Distributions between 3.5 and 2 Ga based on ɛ Hf median values of four detrital zircon databases as well as our compiled ɛ Nd database are noisy but uniformly distributed in time, whereas data between 2 and 1 Ga data are more tightly clustered with smaller variations. Grouped age peaks suggest that both isotopic systems are sampling similar types of orogens. Only 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 location. External and internal orogens show similar patterns in ɛ Nd and ɛ Hf with age suggesting that both juvenile and reworked crustal components are produced in both types of orogens with similar proportions. However, both types of orogens clearly produce more juvenile isotopic signatures in retreating mode than in advancing mode. Many secular changes in ɛ Hf and ɛ Nd distributions correlate with the Supercontinent cycle. Although Supercontinent breakup is correlated with short-lived decreasing ɛ Hf and ɛ Nd (≤100 Myr) for most Supercontinents, there is no isotopic evidence for the breakup of the Paleoproterozoic Supercontinent Nuna. Assembly of Supercontinents by extroversion is recorded by decreasing ɛ Nd in granitoids and metasediments and decreasing ɛ Hf in zircons, attesting to the role of crustal reworking in external orogens in advancing mode. As expected, seawater Sr isotopes increase and seawater Nd isotopes decrease during Supercontinent assembly by extroversion. Pangea is the only Supercontinent that has a clear isotopic record of introversion assembly, during which median ɛ Nd and ɛ Hf rise rapidly for ≤100 Myr. Although expected to increase, radiogenic seawater Sr decreases (and seawater Nd increases) during assembly of Pangea, a feature that may be caused by juvenile input into the oceans from new ocean ridges and external orogens in retreating mode. The fact that a probable onset of plate tectonics around 3 Ga is not recorded in isotopic distributions may be due the existence of widespread felsic crust formed prior to the onset of plate tectonics in a stagnant lid tectonic regime, as supported by Nd and Hf model ages.
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The Supercontinent Cycle
Earth as an Evolving Planetary System, 2011Co-Authors: Kent C. CondieAbstract:This new chapter in the book discusses the Supercontinent cycle and its effects on Earth history. It reviews methods of Supercontinent reconstruction and the processes involved in Supercontinent assembly and breakup. It reviews problems associated with identifying the first Supercontinent in the late Archean, and briefly reviews the history of later Supercontinents Nuna, Rodinia, Gondwana and Pangea. It suggests that the episodicity of U/Pb zircon ages is related to preservation of continental crust during Supercontinent formation and not to peaks in juvenile crust production. The relationships of the Supercontinent cycle to mineral deposits, Sr isotopes of seawater, sea level variations and organic evolution are also summarized. Mantle superplume events are discussed as are possible relationships and feedbacks between various climatic regimes, the carbon cycle and the Supercontinent cycle.
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The Supercontinent Cycle and Mantle-Plume Events
Earth as an Evolving Planetary System, 2005Co-Authors: Kent C. CondieAbstract:Publisher Summary The chapter discusses the Supercontinent cycle and mantle-plume events. Supercontinents have aggregated and dispersed several times during geologic history, although geologic record of Supercontinent cycles is only well documented for the last two cycles: Gondwana–Pangea and Rodinia. It is generally agreed that the Supercontinent cycle is closely tied to mantle processes, including both convection and mantle plumes. However, the role that mantle plumes may play in fragmenting Supercontinents is still debated. Rather, the data suggests that two types of Supercontinent cycles may be operating: (1) a sequential breakup and assembly cycle and (2) a Supercontinent assembly cycle only. In the sequential cycle, a Supercontinent breaks up over a geoid high (mantle upwelling) and the pieces move to geoid lows, where they collide and form a new Supercontinent partly during but chiefly after the Supercontinent breakup.
