a) North China Craton within the Paleoproterozoic Columbia supercontinent (after Kusky and Santosh, 2009). (b) Tectonic framework of China illustrating the major Precambrian cratons and younger orogens (after Zhao et al., 2005).http://www.sciencedirect.com/science/article/pii/S0301926810000446

(a) P-wave tomography of the Western Pacific region showing slab graveyards (after Zhao, 2004). The vertical cross-section is shown for a profile passing through northeast China and central Japan. The velocity perturbation scale is shown at the bottom. The flat-lying stagnant slabs in the mantle transition zone extends for over 2000 km. The low velocity anomalies under the Pacific slab in the upper and topmost lower mantle, if representing a compositional anomaly, might indicate subducted felsic material. See text for discussion. (b) Sketch from P-wave tomographic image beneath Izu-Bonin arc showing the anatomy of subducted slab including the downgoing, bottoming and flattening domains (after Fukao et al., 2009). (c) Speculated slab graveyards on the coreиCmantle boundary through geological time as proposed by Maruyama et al. (2007) from P-wave whole mantle tomography by Zhao (2004). The calculated slab graveyard back to 180 Ma are also shown superposed with the present day distribution of continents. The green region represents slab graveyard during the last 180 Ma, the yellow region shows the Rodinia slab graveyard, and the dark blue region shows the Gondwana slab graveyard. The region with arrows shows the slab graveyard of Laurasia. The definitions of the slab graveyards were based on the paleopositions of the supercontinent or megacontinent. The Pacific superplume occurs at the center of the Rodinia slab graveyard. The African superplume is also shown within the Gondwana slab graveyard (after Maruyama et al., 2007)

Cartoon speculating the fluid distribution from surface to the core of the Earth (after Santosh et al., 2009b and references therein). Mid oceanic ridge basalt (MORB) subducted at the trench sinks through the mantle transition zone and finally drops down to the coreиCmantle boundary (CMB). The MORB components are then heated up by the outer core leading to partial melting. The dense iron rich melts accumulate on the bottom of the Dбх layer. The remaining restite MORB with dominant andesitic composition rises upward to form superplume. The subducted slab from the trench is hydrous, and is heated up by the surrounding mantle which releases the water in the mantle wedge and enhances the viscosity. The origin of a superplume at the coreиCmantle boundary is discussed in Maruyama et al. (2007). The vertically rising superplume enters into the upper mantle, transforms to horizontal and branches out into several hot spots. These hot spots cause the rifting of the continent, and deliver the mantle fluid (mainly C-O-H-S) to the surface. Surface CO2 has been selectively transported into the mantle in the Hadean to the Archean. After the Neoproterozoic, surface water started to be transported into the mantle transition zones (410иC660 km). For the major part of the Earth''s fluid history, the fluid transport was mostly one wayбкfrom the outer core to the surface. The return flow of water is thought to have been initiated probably after 750 Ma, and has not yet entered into the lower mantle. MORбкMid ocean ridge.

Cartoon illustrating the process of material circulation on a whole-earth scale controlled by plate, plume and anti-plate tectonics (after [51] and [88]). The subducted slab material, as inferred from seismic tomography, may be plausibly considered to reach the coreЦmantle boundary. This recycled oceanic lithosphere is viewed as a potential trigger of, and contributor to, the superplume rising from the coreЦmantle interface to the uppermost mantle, penetrating the mantle transition zone and eventually giving rise to hot spots. Radioactive heat generated in СenrichedТ basaltic slab remnants, and the heat given off by post-perovskiteЦperovskite phase transformation may contribute to generating small-scale plumes which ultimately coalesce into a superplume (see Maruyama et al., 2007 for details). The implication of horizontal movement at the base of the mantle has been referred to as Сanti-plate tectonicsТ, in many respects analogous to lithospheric plate tectonic processes operating in near-surface regions. Accordingly, through time, it is conjectured that continents gradually develop at or close to the outer earth surface while concomitant Сanti-continentsТ would be generated at the CMB (Maruyama et al., 2007). Also shown are tectosphere-bearing surface continents and water subduction into the mantle boundary layer (mantle transition zone) where rising hydrous plumes are predicted.

Cartoon illustrating tectonic erosion and sediment trapped subduction

Cartoon illustration showing a composite plate tectonic model for southern India from North (Archean Dharwar Craton) to South (Pacific-type orogen) with two major collisional orogens in between. The PCSZ represents the main suture developed through Mozambique Ocean closure. The cross section also covers ACSZ + KKB/Trivandrum Block up to the Nagercoil Block at the southern tip. The Madurai Block represents a wide magmatic arc in between.Anatomy of a Cambrian suture in Gondwana: Pacific-type orogeny in southern India? -http://www.sciencedirect.com/science/article/pii/S1342937X09000057

Cartoon speculating the dynamics and compositional layering of solid Earth through time (after Kawai et al., 2009). The anorthositic crust formed after the consolidation of magma ocean in the Hadean was ultimately subducted to the bottom of the mantle with time. Simultaneously, TTG crust began to accumulate at the mantle transition zone, as the buoyancy of the material inhibited its transport further deep into the mantle. The model predicts that through time, TTG crust has accumulated in the mantle transition zone, whereas the subducted mid oceanic ridge basalt together with slab peridotites dropped down to accumulate on the coreЦmantle boundary. Thus a three-layer structure can be speculated on a whole Earth scale with substantially larger СcontinentsТ and СsupercontinentsТ occurring on the mantle transition zone and coreЦmantle boundary as compared to those on the surface of the globe

History of major supercontinents speculated from mantle dynamics (after Senshu et al., 2009). The top panel shows supercontinents through time from the Paleoproterozoic Columbia (which is perhaps the first coherent supercontinent) at ca. 1.8Ц1.9 Ga through Rodinia at 1.0 Ga, and a combination of Gondwana (540 Ma) and Pangea (250 Ma). The bottom panel shows the timing of super-downwelling events, a process that is considered as critical for the rapid amalgamation of continents and as evaluated based on the presence of Y-shaped triple junctions from paleogeographic configurations of supercontinents (Santosh et al., 2009a). The super-downwellings would therefore roughly correspond to the timing of assembly of supercontinents. Based on the configuration, super-downwelling and mantle dynamics, the only supercontinent that was assembled within a short period of time was the hypothetical Paleoproterozoic supercontinent Columbia. The three parameters also match well for Rodinia. However, there is a wide time gap between Gondwana and Pangea, and therefore Senshu et al. (2009) clubbed these and proposed that, the timing of a true supercontinent assembly subsequent to the Neoproterozoic Rodinia in terms of mantle dynamics, is at ca. 340 Ma. According to this model, the lifespan of supercontinents becomes longer with time which has been correlated to the decrease in the rate of heat generation by subducted TTG material.

Representative field photographs illustrating evidence for subduction and ocean closure preserved in the deeply eroded collisional sutures of Precambrian supercontinents where diagnostic lithologies considered as markers for sutures are absent. (a) Field photograph showing the association of amphibolites (metavolcanics) and metachert from the Palghat-Cauvery Suture Zone, a trace of the Late Neoproterozoic Gondwana-forming suture. This association and other various evidences from this zone (discussed in Santosh et al., 2009c) provide support for ocean plate subduction during the closure of the Neoproterozoic Mozambique Ocean. (b) Field photograph showing the association of ultra-high temperature (UHT) MgЦAl granulite and metagabbro from the Inner Mongolia Suture Zone in North China Craton ( [86] and [90]), a trace of the Paleoproterozoic Columbia suture. The association of UHT granulite and metagabbro within duplexes suggest extreme metamorphism of MgЦAl sediments within the subduction channel and their extrusion and accretion together with remnants of the oceanic lithosphere and/or fragments of the mantle wedge during the final collisional stage

(a) Cartoon illustrating the concept of double-sided subduction discussed in the text (after [51] and [87]). (b) Geological and tectonic framework of the North China Craton showing the assembly of crustal blocks through opposing subduction as interpreted from a recent synthesis of S-wave receiver functions, S-wave velocities and two versions of P-wave tomographic images along various transects in this craton (after Santosh, 2010). The assembly of the major crustal blocks within the North China Craton during the Paleoproterozoic and their incorporation within the Columbia supercontinent are correlated to double-sided subduction history. (c) The Central India Tectonic Zone (CITZ) that sutures the South and North Indian blocks. The major cratons are also shown. A combined geological and geophysical synthesis suggests double-sided subduction as a trigger for the Mesoproterozoic suturing event (after Naganjaneyulu and Santosh, in press).

(AЦE) Stages of breakup and assembly of supercontinents through СintroversionТ, СextroversionТ or a combination of both introversion and extroversion as discussed in the text (after Murphy and Nance, 2005). (F) Schematic representation of the Sm/Nd isotopic evolution of oceanic lithosphere from the interior and exterior oceans (from Murphy et al., 2009). The depleted mantle ages for the interior ocean (TI) are younger than the time of supercontinent breakup (TR). Whereas in the case of exterior ocean (TE) the ages are older. Relative to the breakup of Rodinia supercontinent, the Mozambique Ocean is an exterior ocean; relative to the breakup of Pannotia, the Iapetus and Rheic Oceans are interior oceans

Cartoon sketch illustrating the anatomy of a Pacific-type orogen (modified after Maruyama and Parkinson, 2000). The inset figure shows paired Pacific-type and collision-type orogens that develop on either side of the suture during continental amalgamation as proposed in this study.

Sketch showing the travelogue of an oceanic plate from its origin at the mid oceanic ridge to its subduction at the trench to illustrate the concept ocean plate stratigraphy (OPS) (with information synthesized from [54], [63] and [53]). The top panel shows the characteristic original stratigraphic succession developed during successive stages interpreted as a function of distance from the ridge and time of travel

Cartoon illustrating the role of mantle dynamics and supercontinents in life history and surface environment. The figure shows the relationship between superplume, supercontinent breakup and mass extinction (after Isozaki, 2009) during the Late Guadalupian (Middle Permian; ca. 265 Ma) event, an episode termed the Illawarra Reversal. The model envisages two stages: (1) a strong retardation in the geomagnetic field led to a break in the geomagnetic barrier allowing galactic cosmic rays to infiltrate. This resulted in the formation of thick cloud layers which ultimately stopped the oxygen pump. The second stage is marked by the birth of a superplume and its upwelling, followed by voluminous volcanic eruption leading to plume winter

Two types of ocean closure following supercontinent breakup as proposed by Silver and Behn (2008). Orange-shaded regions Ц supercontinents; black lines with dark blue triangles Ц subduction zones; thick red lines Ц internal ocean; blue rectangles in (d) and (f) Ц oceanic crustal materials including ophiolites trapped in the suture zone. http://www.sciencedirect.com/science/article/pii/S167498711000006X

Schematic illustration of the thermal blanket hypothesis of supercontinent breakup (after Senshu et al., 2009).http://www.sciencedirect.com/science/article/pii/S167498711000006X

Phase relations for continental crust represented by anorthosite and TTG (tonalite-trondhjemite-granodiotite; after Komabayashi et al., 2009). MORBЦMid ocean ridge basalt; PvЦ perovskite; PpVЦ post-perovskite. The typical mantle geotherm is also shown. See text for discussion. The study demonstrates that all these materials can be subducted down to the core-mantle boundary, leading to the development of a compositional stratification in the DФ layer

Supercontinent breakup initiated by superplume rising from the core-mantle boundary (after [Maruyama et al., 2007] and [Senshu et al., 2009]). The phase change of subducted Mid Ocean Ridge Basalt (MORB) into post-perovskite releases latent heat generating many small scale hot plumes, which eventually gather to create a superplume

A speculative model for the evolution of modern life forms following supercontinent breakup. The breakup of the Neoproterozoic Rodinia supercontinent (a, after Rino et al., 2008) generated enlarged shallow marine environments (b, after Maruyama and Santosh, 2008), with increased oxygen level and enrichment of nutrients. This isolated environment was conducive for the extensive development of body plans and enhancement in the size and diversity life forms which finally led to the so-called Cambrian explosion. The rift-related basins thus provided the Сlife soupТ for the rapid evolution of modern life. G1 to G5 in the Rodinia reconstruction shown in (a) correspond to the classification into various groups (North American, African, Russian and Asian Grenville Groups) based on Rino et al. (2008) on the basis of zircon age data

Cumulative percentage of the occurrence of giant dyke swarms, carbonatites and kimberlites and the model periodic production of giant dyke swarms (after Yale and Carpenter, 1998). The approximate timings of assembly and disruption of the major supercontinents through Earth history are also shown.

Cartoon illustrating the role of mantle dynamics and supercontinents in life history and surface environment. The figure shows the relationship between superplume, supercontinent breakup and mass extinction (after Isozaki, 2009) during the Late Guadalupian (Middle Permian; ca. 265 Ma) event, an episode termed the Illawarra Reversal. The model envisages two stages: (1) a strong retardation in the geomagnetic field led to a break in the geomagnetic barrier allowing galactic cosmic rays to infiltrate. This resulted in the formation of thick cloud layers which ultimately stopped the Уoxygen pumpФ; the second stage is marked by the birth of a superplume and its upwelling, followed by voluminous volcanic eruption leading to plume winter.