test_true_extraction.txt

'\nStarting now, you need to answer user questions based on the factual information provided to you. You are prohibited from fabricating any information that does not exist beyond the factual information given to you. The factual information will be provided to you in JSON format, containing details at the reference-level, location-level, and site-level. The reference-level information corresponds to literature-related information, the location-level corresponds to the location-related information within the literature, and the site-level corresponds to site-related information within the literature.\nIf the user\'s query involves information contained within the factual information provided to you, you must return the relevant information. If not, you should not fabricate any information and tell the user that the information is not included in the given fact, THEN answer the question without using the given fact.\nBelow is the factual information and user question:\n<Fact Information>:\nThe theory of plate tectonics is widely accente. by scientists and provides a robust framework with which to describe and pred ^t the behavior of Earth\'s rigid outer shell the lithosphere - in space and time. Exp  sio.is of plate tectonic interactions at the Earth\'s surface also provide critical insig t in.to the machinations of our planet\'s inaccessible interior, and allow postulation about th.- g.ological characteristics of other rocky bodies in our solar system and beyond. Forr iah. ation of this paradigm occurred at a landmark Penrose conference in 1969, repre enting the culmination of centuries of study, and our understanding of the“what”,“where”,“why”, and “when” of plate tectonics on Earth has continued to improve since. In this Centennial review, we summarize the major discoveries that have been made in these fields and present a modern-day holistic model for the geodynamic evolution of the Earth that best accommodates key lines of evidence for its changes over time. Plate tectonics probably began at a global scale during the Mesoarchean (c. 2.9-3.0 Ga), with firm evidence for subduction in older geological terranes accounted for by isolated plate tectonic ‘microcells\' that initiated at the heads of mantle plumes. Such early subduction likely \nhotter oceanic lithosphere. A transitional period during the Neoarchean and Paleoproterozoic/Mesoproterozoic was characterized by continued secular cooling of the Earth\'s mantle, which reduced the buoyancy of oceanic lithosphere and increased its strength. allowing the angle of subduction at convergent plate margins to gradually steepen. The appearance of rocks during the Neoproterozoic (c. 0.8-0.9 Ga) diagnostic of subduction do not mark the onset of plate tectonics, but simply record the beginning of modern-style cold, deep, and steep subduction that is an end-member state of an e^-lie. hotter, mobile lid regime. \nKeywords: Plate tectonics, secular change, geodyna nic. petrology, planetary science Plate tectonics has been ccepted by most scientists since the late 1960s as a reliable description of how the Earth\'s lithosphere “behaves\'; however, the inception of this paradigm began many years earlier (Romm, 1994). First-order observations of similar shapes of coastlines either side of the Atlantic Ocean have been noted and theorized upon since the late 16" century by explorers such as Sir Francis Bacon. In his 1620 work Novum Orgaum, he noted “both the New World [South America] and the Old World [Africa] are broad and extended towards the north, narrow and pointed towards the south”, though Bacon made no inference of both having been joined together in the past. Later papers published in the 18" \nand 19" century by various philosophers and naturalists, including Theodor Christoph Lilienthal and Alexander von Humboldt, continued to document geometric and geologic similarities along each coastline, but attributed their current separation to a Biblical catastrophe (cf. Kearey et al., 2009). \nand 19" centuries marked a transition in scientific thought from “catastrophism””, where geological change occurs due to highly energetic events happeing uddenly and unpredictably, to “uniformitarianism\', where change takes plae by lower-energy events occurring gradually over time (Gould, 1965). The con^en of uniformitarianism, often encapsulated by the maxim “the present is the key to the past", forced the subsidiary implication that the Earth was extremely old, con lic ing with estimates of ~20-200 Myr made at the time by Lord Kelvin (cf. Bur hf.eld, 1990). Uniformitarianistic principles were first applied to the idea of “drifting” lan \'masses by Frank Taylor, an American physicist, in 1910. who presented a hypothesis “s woling what is now referred to as continental drift (cf Le Grand, 1988). In Taylor\'s in. del, formerly polar continents were driven laterally towards the equator, creating an ecuarial bulge around the Earth and colliding to form approximately east-wes. trending mountain ranges (e.g. the Alpine-Himalayan orogenic belt). A continent was also suggested to have broken apart to form the Atlantic Ocean. While conceptually close to the truth, Taylor incorrectly suggested that the gravitational pull of the \nIn 1912. Alfred Wegener - a German meteorologist - proposed a similar model of horizontal continental motion and expanded on Taylor\'s ideas by documenting several independent sets \nassembly Pangaea - literally meaning “all the Earth”- wh cn s now understood to have later broken apart into two supercontinents: Laurasia in the nou.h (North America, Greenland, Europe, and Asia) and Gondwana in the south (South An erica, Antarctica, Africa, Madagascar, India, and Australasia) (e.g. Olse , ). These continental masses were separated by the Tethys Ocean - the pro - editerranean Sea - and surrounded by Panthalassa - the proto-Pacific Ocean (. rias, 2008). Unfortunately, Wegener\'s ideas were initially rejected by many Europe a d North American geologists, as they required discarding the existing scientif.  ortnodoxy of a static Earth, and due to his theory being based on multidisciplinary da.o .n fields of study that he was not an expert. Small faults were used by prominent scier. isus at the time to reject the broader-scale hypothesis outright, and a critical limitation was Wegener\'s inability to provide a plausible mechanism for continental motion (cf. Kearey et al., 2009). Soon afterwards, Holmes (1928) proposed that convection currents in the mantle powered by the heat of radioactive decay may have dragged continents across the Earth\'s surface, though it is known today that this force has minimal influence on lithospheric plate motion (see section 5). Nonetheless, this idea, which emerged nearly 40 years before formalization of the theory of plate tectonics, planted the seed for deciphering \nmechanisms that could explain the wealth of observational data supporting a mobile Earth \nsurface \n1950s revealed that many continental igneous rocks preserve magnetic pole positions and orientations that differ from the present day (Keevil, 1941; Holmes and Smales, 1948; Collinson and Runcorn, 1960). Two competing interpretations can be drawn from these data: (1) the Earth\'s magnetic poles remained static over time, but th^ co. tinents wandered; or (2) the continents remained fixed as magnetic poles migrated crc ss the Earth\'s surface. The latter interpretation would be acceptable for data obtaineo from a single supercontinent, such as Pangea, but cannot account for several discrete lar dn. sses identifying multiple poles in different places at the same time in Earth histcry, un.ess the ancient magnetic field was not bipolar. These data thus provided further u port for the notion that landmasses may have moved great distances across the Earth . surface over time (Cox and Doell, 1960). na \nMapping of the ocean floor du ng and after World War II revealed a semi-continuous “mid ocean ridge”(MOR) system re than 65,000 km long that stood tall above the adjacent abyssal plains (e.g. Ew. and Heezen, 1956). In 1962, marine geophysicist Harry Hess studied these maps and developed his seminal theory of sea floor spreading, suggesting that new ocean crust was created at MOR systems and spread out laterally, pushing the continents apart (Hess, 1962). In this model, new oceanic crust formed from upwelling and cooling of magma at ridges, divided in two, and each half moved laterally away from the ridge. Hess hypothesized that sea floor spreading would thus be driven by thermal convection cells in the mantle, and old, cold crust must be destroyed elsewhere on the Earth so that the planet\'s surface area remained constant. Continued mapping of the oceans ultimately revealed vast \nbathymetric depressions situated at some ocean margins that were associated with intense volcanic and seismic activity (e.g. Jongsma, 1977). These phenomena were concluded to be consistent with features expected from subduction of oceanic lithosphere at convergent plate boundaries. Further and final support for the sea floor spreading hypothesis came from the discovery of “magnetic anomalies” retained within seafloor basalt, which formed roughly parallel to a central MOR and were symmetrical on either side (Vine and Matthews, 1963) The recognition of transform faults that connect linear belts of tectonic activity (Wilson, 1965) allowed the Earth\'s surface to be divided into a compley mos tic of seven major and several smaller plates that rearrange continuously like a jis saw puzzle. Geometrical relationships defined between plates moving across a sphe ical planetary surface (e.g. McKenzie and Parker. 1967) and more information deri、ed from seismic observations about their behavior following subduction into the r an.\'Coney and Reynolds, 1977) refined these geophysical models of oceanic lith、 sr iere formation, evolution, and destruction. \nFormalization and widespread acc^nt.e of the plate tectonic paradigm is often agreed to have occurred in 1969 at the G. ological Society of America Penrose Conference, Pacific Grove, California, entitled “1 Meaning of the New Global Tectonics for Magmatism Sedimentation, and Mewmorphism in Orogenic Belts”. Many prominent geoscientists outlined observations and interpretations at the meeting and published seminal papers soon afterwards that supported plate tectonics having operated on Earth for many millions of years (Dewey and Bird, 1970; Kay et al., 1970; Minear and Toksoz, 1970; Oxburgh and Turcotte, 1970). Notably, the broad-scale synthesis presented at that meeting has changed surprisingly little since (Le Pichon, 2019); but what was the geological orthodoxy beforehand and how did interpretations of Earth evolution differ? The pre-plate tectonics “static’ model of the Earth interpreted all tectonic features as having formed essentially by vertical movements at \nwere first outlined by geologist James Hall at his Presidential address made to the Geological Society of America in 1857 (cf. Knopf, 1960). In this model, geosynclines were geographically fixed domains of deep subsidence where sediments accumulated and were eventually buried deeply enough for metamorphism and partial melting to occur at their bases. The morphology of a mountain belt thus corresponded to the original location of greatest sediment accumulation in the geosyncline (i.e. the deepest part of the trough). Subtypes of these geosynclines were classified based on whether ylca. ic rocks were present in the succession: if so, these were called eugeosynclines, an. not, they were called miogeosynclines (Bond and Kominz, 1988). As such, in tt.? context of the plate tectonic paradigm, miogeosynclines would represent basins forn. ng along the passive margin of a continent, which typically contain clastic and l io _er.ic sedimentary rocks (sandstone, limestone, and shale), and eugeosynclinev ould represent accretionary or collisional orogens containing deformed and metamorphosc1 sedimentary and volcanic sequences (Shimron 1980; Palin et al., 2013; Sepidbar ^t ar 2019). \nMany mechanisms were sugg .ed to drive the formation and evolution of geosynclines. but Y most prominent was ‘gr. vnational sliding\', which invoked isostatic warping of sedimentary piles and minor thrusting of different strata along low-angle fault systems (Krebs and Wachendorf, 1973). Alternatively, some scientists supported the idea of a contracting Earth (cf. Dott, 1997), which assumed that our planet formed in a fully molten state and has since been cooling and contracting. Shrinkage of the Earth\'s outer shell would have caused lateral C compressional forces that folded (or crinkled) geosynclinal sedimentary sequences upwards to produce orogenic belts. While both hypotheses involve minor components of local horizontal motion. it is important to note that geosynclinal theory personified the idea of a \nstatic (immobile) Earth surface and so struggled to explain many common geological structures and phenomena that are prevalent on Earth today. By contrast, the theory of plate tectonics provides a unified explanation of all the Earth\'s major surface features and has revealed unprecedented linkages between many fields of study (Condie, 2015; Palin et al., 2020). We explore some of these phenomena in the sections below. \ngeodynamic scenarios? Multidisciplinary study of rocky b odie s in our solar system including planets, moons, and asteroids of various sizes -. hows that a wide range of tectonic regimes may occur at their surfaces (Watters, 2010), anu these may transition between states with time as the body cools (Fig. 1). Followin, e atlished conventions, we emphasize that  ‘plate’ is the colloquial term for a discre.r.ass of lithosphere (Barrell, 1914), which may be entirely oceanic, entirely continental, or have components of both. The lithosphere - or lid on a rocky body may be distinguished f*om its underlying asthenosphere in several ways. For example, a thermal definition c. n be used based on whether the dominant mode of heat flow is by conduction (lithosphere,^ convection (asthenosphere) (Chapman and Pollock, 1977). Alternatively, from a rh logical perspective, the lithosphere acts in a rigid manner, whereas the underlying asthenosphere is weaker and able to flow over geological timescales (Walcott, 1970; Doglioni et al.. 2011). The behavior of the lithosphere divides geodynamic scenarios into two end members: stagnant and mobile. \nStagnant lid regimes are characterized by significantly lower horizontal surface (lid) velocities compared to internal (asthenospheric mantle) velocities, which differ by around two to three orders of magnitude (Weller and Lenardic, 2018). Many forms of stagnant lid \nand energy exchange between the surface and interior, but with limited (if any) horizontal displacement (Solomatov and Moresi, 1997; Piccolo et al., 2019, 2020). Recent conceptual models consider that the early Earth was an unstable stagnant lid planet with unsubductable lithosphere, and that mantle overturns were triggered by inefficient coiling of the stagnant lid (Bedard, 2018). As such, stagnant lid regimes may be considered analogous in many respects with the pre-plate tectonic orthodoxy of geosynclinal theory, where almost all tectonic activity occurs due to vertical motion. By contrast, mobile lid rogin.es are characterized by substantial horizontal motion of lithospheric plates with re ,pe、t to the underlying asthenosphere (Cawood et al., 2006), which typically hove relative velocity ratios of 0.8-1.8 (Weller and Lenardic, 2018). Plate tectonics, as it oc urs on Earth today, is the only known form of a mobile lid tectonics in the rocky bodies in our solar system (Poirier, 1982; Head et al., 2002; Wade et al., 2017; Stern et al., 0\'8), although others can be speculated upon. Mass and energy exchange between a planet . surface and interior is relatively easy in a mobile lid geodynamic regime, with subductin f oceanic and/or continental lithosphere at convergent plate margins continuously tra. poruing volatiles and solid rock into the Earth\'s interior (Poli and Schmidt, 2002; Riipke et .l, 2004; Weller et al., 2016; Cao et al., 2019; Lamont et al., 2020), and return proce. es generating new crust at arcs (Hawkesworth et al., 1997; Collins et al., 2016: Li et al., 2020) and divergent spreading centers (Spiegelman and McKenzie, 1987; Sinton and Detrick, 1992; Morgan et al., 1994). \nGiven the vast amount of observational data that now exist for planets, satellites, and smaller bodies (e.g. Ceres) in our solar system, we are learning more and more about the rich variety of geological features that may form on the surfaces of rocky or icy bodies (e.g. Stern et al., 2015). A conceptual tectono-magmatic evolution of a rocky planet over time is shown in Fig. \nnot feature in this generic evolution, as it is an “unexpected” geodynamic state that is thought to require many independent factors to be favorable, such as the presence of surface water (Korenaga, 2020). The initial condition for all rocky planets and satellites that can internally differentiate is that of a magma ocean near to the body\'s surface above a solid lower mantle and metallic core (Weyer et al., 2005; Elkins-Tanton, 2012). The thickness of this magma ocean depends on body radius; for instance, small bodies with low gravity, such as the Moon, will experience a smaller increase in pressure with depth (dPld-) an d so the peridotite solidus is reached at much greater depth than larger bodies with higne dPldz, such as Mars (ElkinsTanton, 2008). Integrated petrological and thermal models of the very early Earth suggest a fully molten magma ocean to shallow depths (~20-30 k.) situated above a partially molten crystal-rich mush that extended to a depth of -3U .n (Abe, 1997; Elkins-Tanton, 2012). Complete solidification of this terrestriar m gma ocean/mush likely occurred within 1-10 Myr (e.g. Monteux et al., 2016), although this timescale on other planets depends strongly on body size, which controls the surf e . . a to volume ratio (SA/V). For example, Earth has SA/V ~ 4.6 x 10“, although th、 hypothesized magma ocean on 4 Vesta - the second largest body in the asteroid belt, but vh a radius just ~9% of Earth\'s and SA/V ~ 1.1× 10²- is thought to have solidifi + completely in just hundreds of thousands of years (Neumann et al., 2014). Thus, larger rocky bodies are expected to remain geologically active over significantly longer timescales than smaller rocky bodies. \nCrystallization of a primitive terrestrial magma ocean would have proceeded by expulsion of melts towards the Earth\'s surface, where they may either extrude as volcanic lava flows or solidify during ascent, forming plutons (Mole et al., 2014; Rozel et al., 2017; Piccolo et al., 2020). The earliest stage of the evolution of a stagnant lid geodynamic regime is expected to \ntime. This scenario, with volcanism dominating over plutonism, has been suggested for the Hadean Earth and has been dubbed heat-pipe tectonics (Fig. 1: Moore and Webb, 2013). Continuous eruption of lava and thus repeated burial of older flows causes this primitive crust to thicken, which makes it increasingly more difficult for ascending melts to reach the surface (Malviya et al., 2006; O\'Neil and Carlson, 2017). Thus, over time, volcanism becomes subsidiary to intrusive magmatism. Old mafic lavas that are buried during continued igneous activity and crustal thickening will undergo metamorphic tran forn. .tion to amphibolite and granulite at pressures exceeding ~6 kbar, with garnet stabi\'izn g at lower crustal conditions (>12 kbar; Raase et al., 1986; Palin et al., 2016a). If suffic_ently hydrated, these metabasalts will partially melt, and experimental and petrologica\' me deling has shown that they should produce magmas of tonalite-trondhjemite-gra io. o ite (TTG) composition (Moyen and Stevens, 2006; Martin et al., 2014; Palin t ., 2016b). These felsic melts rise towards the surface of the Earth and may either stan and form plutons in the lower, middle, or upper crust, or erupt onto the surface as lvand pyroclastic materials. All Archean terranes contain abundant TTG plutons or metamorphosed versions thereof - gray gneisses), which are thought to represent Earti.\'s first stable continental crust (Martin, 1993; Moyen and Martin, 2012; White et .\' , 2017), and importantly, as discussed in section 6, likely did not form via subduction (e.g. Martin et al., 2014; Palin et al., 2016b) \nContinued thickening of a mafic crust produces high-density eclogite at >20 kbar (>60 km), which is gravitationally unstable compared to underlying peridotite (Ito and Kennedy, 1971; Aoki and Takahashi, 2004). On the hotter Archean Earth, these lower crustal portions are predicted to ductilely deform and “drip” into the underlying mantle via short-wavelength, density-driven downwellings (van Thienen et al., 2004; Fischer and Gerya, 2016). Mantle \nmagmatic activity over regions of upwelling (e.g. Piccolo et al., 2019). This stagnant lid environment dominated by intrusive magmatism into a thick crust instead of the repeated extrusion of lavas is often referred to as a drip-and-plume geodynamic regime, or colloquially “plutonic squishy lid” (e.g. Lourenco et al., 2020). Cooling of the mantle and thickening of newly formed lithosphere is shown via two- and three-dimensional thermo-mechanical models of the Archean Earth to increase the spacing between mantle plumes and to inhibit localized drip-like density inversions (Fischer and Gerya, 2016: Pi olo et al., 2020). Then, high-density eclogite and underlying depleted mantle term na\'y sink into the asthenosphere via broad-wavelength and large-volume delaminations (e. Kay and Kay, 1993; Zegers and van Keken, 2001; Foley et al., 2003; Piccolo et al., 201s; Convective upwellings in the asthenospheric mantle drive decompression m l. o and continued formation of new mafic crust, which may be buried and melted tu fc.m new felsic TTGs in a cyclical process that continually builds new continents (Kan. er et al., 2002; Moyen and Martin, 2012: Palin et al. 2016b; Wiemer et al., 2019). \nAll differentiated planetary b des - whether they exhibit a stagnant or mobile lid regime while geologically activ.. will ultimately evolve towards having a global, thick crust and whole-mantle lithosphere as their terminal state (Fig. 1). This is an inevitable result of secular cooling of a planet\'s interior causing the Rayleigh number to fall below the threshold at which convection is effective, such that any remaining internal heat can only be lost via geologically ‘dies\' and is expected to exhibit minimal if any tectonic activity at is surface, although continued cooling and planetary contraction may induce localized deformation or cause reactivation of pre-existing lines of weakness (e.g. Watters et al., 2012; Watters et al. \n2016; Valantinas and Schultz, 2020). This tectonic mode is expressed today in the solar system by Mercury and the Earth\'s Moon (Hauck et al., 2004) \nThe question of where plate tectonics operates is not straightforward to answer, despite earlier statements that Earth is the only known planet to exhibit this style of mobile lid regime. If plate tectonics is one of many intermediate steps in the ever-changing lifecycle of a silicate body (Fig. 3), there is every possibility that another plant - in our solar system or beyond - may have transitioned into this regime at some point in time and has since transitioned out. Such an argument could theoretically he  ade for Venus, which experienced a global resurfacing event at c. 300 Ma (Strom et al.. 194); the cause of which remains unknown. Can we confidently ascertain the ge  nnic regime(s) that came before if all surface evidence has been erased? Even .fr ics of Venus\' ancient past remain, we will likely not discover them for centuries. Focuse\' mapping and detailed laboratory investigation of rocks on the Earth\'s surface have heei onducted for decades, although many points of debate about relatively simple . uestions remain concerning the evolution of tectonics on oun planet. How long, then, mion. it take to map out, sample, analyze, and interpret the vast geological richness of u.^ venusian surface in order to come to a somewhat complete understanding of its geological past? While we present this as simply a rhetorical question, it raises the key philosophical issue that ‘where’ may be just as readily phrased as \'when\' if we are not discussing the Earth. \nMany forms of tectonic activity have been documented elsewhere in our solar system, of which two unique cases occur on the Galilean satellites - the four largest moons of Jupiter. The innermost satellite, Io, is thought to currently exhibit heat-pipe tectonics (Turcotte, 1989; \nits surface (Spencer et al., 2007). Remote sensing suggests that Io is internally differentiated and its bulk density indicates the presence of a metallic core, thick silicate mantle, and relatively thin crust (Anderson et al., 1996, 2001). Extensive volcanism requires the existence of a global source of magma at depth below its surface, which is thought by many to be sustained by tidal heating of its solid interior (Hamilton et al., 2015), although some workers suggest that it has a global magma ocean (Khurana et al., 2011). Spectral analyses of eruptions imply very MgO-rich lavas of picritic or komatiitic mpsition, equivalent to those predicted to form during decompression melting of t no.ter Archean terrestrial mantle (Williams et al., 2000) or at the head of a mantle plume ( _-ndt et al., 1997). As such, Io may represent an analogue for the very early Earth, albeit at a much smaller scale. A e \na form of mobile-lid behavior that close!y resembles plate tectonics on Earth (Kattenhorn and Prokter, 2014), though with some b.\' diferences. Europa contains a small metallic core, a thick rocky mantle, and a subs. -face liquid-water ocean (~80-100 km) immediately beneath a solid HzO-ice crust (~10-30 kn) (Anderson et al., 1998; Kuskov and Kronrod, 2005). Evidence for active crye tectonics is provided by the extremely low crater densities across Europa\'s surface, which implies a very young mean age and so a mechanism for continuous recycling (Bierhaus et al., 2005). Dilational bands with surface features offset symmetrically on either side thus resemble terrestrial MOR spreading zones and provide evidence of new ice generation. Conservation of surface area and “tectonic\' reconstructions of ice-crust plates were interpreted by Kattenhorn and Prokter (2014) to support transport of surface material into the interior of Europa\'s ice shell along a linear domain, taken to be an analogue of a convergent plate boundary on Earth. Interestingly, active cryo-volcanism has been inferrec \non the ‘overriding\' ice crust, thus providing further support for a brittle, mobile, plate-like shell of H O-ice situated above a warmer, convecting layer (Sparks et al.. 2017). Thus. despite most studies focusing on our neighbor rocky planets that have similar physical and chemical properties to Earth, Europa may instead be the first extraterrestrial solar system discovered to exhibit features closely resembling mobile lid tectonics. \nOur neighboring rocky planets Venus and Mars both show a wide variety of geological features on their surfaces, most of which are expressions of vari ous forms of stagnant lid tectonics (Fig. 1: Solomatov and Moresi, 1996; Reese et a\'., I 98), although others have been debated to represent evidence for plate tectonic-like behay_or. Abundant>1000-km-diameter shield volcanoes on Venus (Ernst and Desnoyers, 2004) nd lava flows spatially resembling terrestrial flood basalts (Lancaster et al., 1995) b th ndicate extensive subsurface mantle plume activity, which is common in a “u in and-plume”geodynamic regime. However, transform faults (Ford and Pettengill, 12; Koenig and Aydin, 1998), linear MOR-like features (Head and Crumpler, 1987).  asymmetric and curved trench-like depressions (Sandwell and Schubert, 1992) bserved in radar maps morphologically resemble surface structures associated with the th.ee types of terrestrial plate margin. Transient spikes in sulfun dioxide contents in the enusian atmosphere (Esposito, 1984; Marcq et al., 2013) suggest  that several regions of the surface are currently volcanically active, indicating that the interior is hot enough to maintain planetary-scale geological activity. Even more importantly, crater counting suggests that the entire Venusian surface is younger than c. 300 Ma (Strom et al., 1994), indicating that all such features formed in the same geodynamic environment, lending support to hypotheses for the early Earth that plate tectonic-like features make form locally within a larger-scale stagnant lid regime (Nimmo and McKenzie, 1998). \nBreuer, 2007) and sporadic seismic activity (Anderson et al., 1977; Banerdt et al., 2020), although most planet-wide geological activity is thought to have ceased at c. 3 Ga (Carr and Head, 2010). Older terranes show clear evidence for active tectonics, metamorphism, and magmatism, with one of the most curious features of the planet being its pronounced hemispheric dichotomy (Andrews-Hanna et al., 2008): here, the northern hemisphere is comprised of low-elevation plains and thin (~32 km) mafic crust, whereas the southern highlands are high-elevation and the crust is much thicker (~58 Im) (Wieczorek and Zuber, 2004). The hemispheric boundary has been studied in deta I ar d has revealed much geomorphological evidence for the flow of liquid water which has led many researchers to suggest that the northern lowlands may once have ben  vered by a vast ocean (Baker, 1979; DiAchille and Hynek, 2010; Oehler and Al r, 2012; Wade et al., 2017). Given the importance of surface water for stabilizi. s.bduction of oceanic lithosphere, this observation has spurned many investigations into wl ether Mars has ever exhibited a mobile lid tectonic \nTwo major geological featuren Mars lend support to this hypothesis. First, mafic rocks of the southern highlands eserve elongate linear remnant magnetic anomalies that have alternating polarities (Connerney et al., 2005) and so superficially resemble the magnetic stripes that form on the ocean floor via sea floor spreading on Earth (Vine and Matthews, 1963). This hypothesis is weakened somewhat by the lack of a geometrical ‘spreading center and that their widths are an order of magnitude greater than the stripes observed on Earth (Connerney et al., 1999); however, in rebuttal, it can be argued that these may record similar plate tectonic-like behavior at a much faster rate than on Earth - thus producing thick stripes instead of thin stripes - or that magnetic-field reversal rates occurred over a much longer \ntimescale on Mars. Nonetheless, these features may also be accounted for by non-plate tectonic processes, such as the episodic intrusion of dikes (Nimmo, 2000). The other major geological feature on Mars that shows cursory resemblance to plate tectonic features on Earth is the Valles Marineris trough system, which Yin (2012) suggested is a >2000-km-long and 50-km-wide strike-slip fault zone. Purported evidence for offset comes from displaced impact craters on either flank of the valley, although the trough system has been alternatively argued to have formed due to catastrophic flooding or graben-like crustal collapse due to movement of subsurface magma (Schultz, 1998; Andrews-Hanna, 2012a 20125, 2012c). As such, current opinion within the geological and planetary scienc. co nmunities is that Mars did not ever exhibit subduction. Nonetheless, both Mars and Ven. hold much promise for understanding the geological processes that operate i i sw onant lid tectonic regimes and continued exploration of both planets in the fu n、will return a wealth of new data that may also shed light on the evolution of the ea. lv arth. \nA final note to be made concerning ‘whre\' plate tectonics may operate must mention planets that lie outside of our own sola. system - exoplanets. There have been many technological advances in the past 50 years th t have substantially improved our ability to locate and quantify physical (e.g. . ass and radius), orbital (e.g. period, semi-major axis), and/or geochemical (e.g. atmospheric composition) properties of exoplanets (Seager and Deming, 2010: Marcy et al., 2005). Some such criteria may be used to argue for the operation of plate tectonics; for example, monitoring of an exoplanet\'s atmosphere may allow detection of sudden spikes of sulphate aerosols injected into it by large explosive volcanic eruptions (Misra et al., 2015). While not diagnostic of plate tectonics, observations on Earth show that explosive volcanism is most commonly related with silica- and gas-rich magmas that form above subduction zones (Eichelberger et al., 1986), as opposed to more silica-poor and \neffusive volcanism that occurs in large igneous provinces caused by mantle plume activity (White and McKenzie, 1986). As a consequence, both 2D and 3D thermo-mechanical modeling has been applied to rocky exoplanets of various mass-radius relationships to determine the likelihood of convection and/or surface plate motion (O\'Neill and Lenardic, 2007: Noack and Breuer, 2014), and thermodynamic modelling of exoplanet compositions has been used to predict their interior mineralogy (Wagner et al., 2011; Dorn et al., 2015; Unterborn et al., 2017; Foley and Smye, 2018; Putirka and Rarick, 2019). Such studies predict that plate tectonics may be inevitable on super-Earths (ale.cia et al., 2007), which are defined by having a mass ~2-10 times that of Earth. O ner exogenic factors that likely control whether an exoplanet develops mobile lid behavio. include its initial internal temperature (Noack and Bruer, 2014), the degree of ola. insolation (Van Summeran et al., 2011), and the presence of surface water (Kor( na a 2011). \nThe question of why Earth exhibit nl.t tectonics is surprisingly well understood in terms of broad-scale geodynamics, alth ugh there is still much fine detail to resolve. Indeed, soon after formulation of the plate . tonic paradigm, several studies were dedicated to understanding what driys plate motion, approaching the issue from both observational and theoretical/modeling perspectives. In a landmark study, Forsyth and Uyeda (1975) compared key physical properties of Earth\'s major tectonic plates and identified certain variables that showed strong positive and negative relationships, while others showed no correlation. The main conclusion to emerge from that study was that the forces acting on the downgoing slab control the velocity of oceanic plates and are an order of magnitude stronger than any other “edge\'or “body’force. Thus, the sinking of dense oceanic lithosphere into the underlying mantle at convergent plate boundaries appears to be the main driving force for horizontal \nsurface motion (e.g. Carlson et al., 1983; Conrad and Lithgow-Bertelloni, 2004; Coltice et al. 2019). This gravitational edge force - slab pull (Fsp) - dominates, although pushing apart newly formed oceanic lithosphere at mid-ocean ridges (ridge push: FRp) also contributes. In addition, convection in the asthenospheric mantle makes a small contribution to driving plate motion by frictionally dragging the underside of the lithospheric mantle (basal drag: FBp) and iceberg-like lithospheric roots that hang down into the asthenosphere may be pushed along by this ‘mantle wind\'(Kaban et al., 2015). The absolute magnitudes of these competing forces and their relative importance through time ho ben further refined and quantified by geodynamic modeling; for example, young a d . ot oceanic lithosphere is more buoyant than old and cold oceanic lithosphere (Alfonsel., 2007; Weller et al., 2019), such that the magnitude of Fsp may evolve as a subductior. zo.re matures (Conrad and LithgowBertelloni, 2002), and higher temperatures wit ii. th. Archean mantle (below) would have reduced mantle viscosity and thus absolu^  alues of Fgp (Artemieva and Mooney, 2002) \nConvection is a fundamental char^^ter i.ic of the mantle and facilitates cooling of the Earth over time (e.g. Hanks and And. "son, 1969; Davies, 1993; DeLandro-Clarke and Jarvis, 1997; Korenaga, 2003; Labrosse and \'aupart, 2007). As temperature changes both horizontally and vertically through the E. "tn s mantle, and the absolute depths of the Moho and lithosphere asthenosphere boundary vary according to tectonic setting (Karato and Karki, 2001; Anderson, 2000; Profeta et al., 2015), discussion of secular cooling of the Earth and other rocky bodies in our solar system requires use of a common reference frame. As defined by McKenzie and Bickle (1988), the mantle potential temperature (Tp) is the adiabatic extrapolation of a mantle geotherm to a planet\'s surface in any given geological environment; for example, the mantle Tp above a mantle plume would be higher than the mantle Tp for a divergent plate margin (mid-ocean spreading ridge). The Tp for ambient mantle reflects \ninterplay between heat lost due to convection in the asthenosphere and/or conduction through the lithosphere, and heat gained due to radioactive decay of heat-producing elements in the mantle and conductive heating from the core (e.g. Korenaga, 2011). Importantly, because the efficiency of each of these parameters varies with time, ambient mantle Tp must also have changed simultaneously since formation of the Earth (Fig. 2), alongside the ratio of internal heat generation in the mantle compared to mantle heat flux, called the convective Urey ratio (Ur) (Korenaga, 2008). \nvalue of Ur is estimated to be 0.23±0.15, and therm .l n.odels that extrapolate it backwards through the Proterozoic, Archean, and Hadean eo s,Korenaga, 2008a, b) produce a concaveupwards mantle Tp curve that has a max. w .n value at c. 2.8-3.2 Ga between ~1675 ℃ (Ur = 0.23) and~1575℃(Ur=0.38) (Fig. 2). As today\'s ambient mantle Tp is ~1350 °℃ (Herzberg et al., 2010), these thermal nodels predict cooling of ~75-100 °C/Gyr, although this intrinsically relies on geoc -mieal assumptions of the Earth, such as it having chondritic concentrations of radiogenic _ .t-producing elements (Leitch and Yuen, 1989). This thermal modeling exercise has u. en supported in recent years by analytical petrology. For example, the chemistry of unaltered mantle-derived magmas is an excellent recorder of the physical conditions present in their source region at the time of extraction from their residue (e.g. Cone et al., 2020), including temperature and pressure. This was exploited by Herzberg et al. (2010), who calculated the liquidus temperatures for a small dataset of non-arc basalts of various ages, which fall roughly between curves for Ur of 0.23 and 0.38, implying Archean \nlavas form due to mantle plume activity (Campbell et al., 1989). It should be noted that other studies have applied similar petrological analysis to larger datasets (e.g. Condie et al., 2016; Ganne and Feng, 2017) and concluded that ambient Archean mantle Tp outside periods of supercontinent formation was colder than estimates provided by Herzberg et al. (2010); potentially as low as ~1350-1500 °℃ (Fig. 2). This would define a less pronounced secular cooling rate of ~30-50 °C/Gyr. While an absolute difference of ~150-200 °℃ in predicted mantle Tp seems small, it has profound implications for the viability of subduction during the Archean, and so the operation or not of global plate tectonics ( o. Cerya, 2014; Piccolo et al., 2019) \nThe structure and composition of oceanic lithosphere cr ted at divergent spreading centers is controlled by mantle Tp (McKenzie and Bickl,  8) and so the viability of subduction initiation and the transition from any fon. c. stagnant lid tectonics to a stable, global form of mobile lid tectonics is fundamentally ln. ed to the thermal history of the Earth. Petrological modeling of melting in the mantle nd. ^nstruction of new oceanic lithosphere at divergent plate margins has been perforn. \'d by many workers. For detailed reviews of these processes, the reader is referred to Lang. wir et al. (1992), Kinzler (1997), and Asimow et al. (2004); however, in relation to s cuar change and the initiation of plate tectonics on Earth, it is sufficient to note that a cold present-day mantle Tp produces a thin and low-MgO oceanic crust, whereas a hotter Archean mantle Tp produces a thicker and high-MgO oceanic crust (Ziaja et al., 2014). The petrophysical and geodynamical implications of such a secular change in oceanic crust composition are profound, impacting the lithologies that form in descending slabs (Palin and White, 2016; Palin and Dyck, 2018), and so their density and material strength (McNutt and Menard, 1982; Weller et al., 2019). Comparative thermomechanical modeling of Phanerozoic and Archean oceanic lithosphere has suggested that a \nhotter Archean mantle reduced the buoyancy contrast between oceanic lithosphere and underlying asthenosphere (e.g. Van Hunen and Moyen, 2012). Generation of a relatively thick and strong (more depleted) mantle lithosphere and relatively thick and weak (hotter) oceanic crust in the Archean would have produced mechanically weak subducting slabs that experienced frequent losses of coherency (Van Hunen and van den Burg, 2008), thus breaking apart at shallow depths and developing an episodic style of Archean subduction, with a typical duration of a few Myr (Moyen and Van Hunen, 2012). Similar petrological calculations of density variation according to metamorphic ph ti. nsformations also predict that the thicker Archean oceanic lithosphere was primed tc su. duct (e.g. Weller et al., 2019), although likely not at steep angles (>10°) that characteric most Phanerozoic convergent S margins (Syracuse et al., 2010). \nO The issue of identifying how and why su.d ction could initiate on the early Earth is separate from constraining the petrological and geodynamic conditions that are needed for it to become self-sustainable. Numeric^l m. eling shows that one-sided subduction consisting of a downgoing slab and an overl, ing arc requires a low-strength zone to form at the plate interface (Hassani et al., 109,.7 agawa et al., 2007) with an effective coefficient of friction <0.1. Dry rocks are una \'e to achieve this condition, indicating that aqueous fluids must be present at convergent plate margins to ‘lubricate\' plate motion (Gerya et al., 2008). This is readily achieved on Earth where liquid water has been present on the planet\'s surface since c. 4.4. Ga (Wilde et al., 2001; Maruyama et al., 2013) and may be transported to various depths within subduction zones as pore fluids in sediments and sedimentary rocks (e.g. mudstone; You et al., 1996), structurally bound water in hydrous minerals, such as chlorite and amphibole, in hydrothermally altered and metamorphosed oceanic crust (Katayama et al., 2006: Palin et al.. 2014: Hernandez-Uribe and Palin, 2019a), and serpentine in metasomatized \nmantle lithosphere (Hyndman and Peacock, 2003; Ranero et al., 2003; Coltorti and Gregoire, 2008). Metamorphism during burial of these lithologies causes dehydration and pulse-like release of H O, COz, and other volatile species (e.g. halogens) at fore-arc and sub-arc depths (Poli and Schmidt, 1995; van Keken et al., 2011; Hernández-Uribe and Palin, 2019b) Transport of water into the deep mantle may be achieved by its incorporation into nominally anhydrous minerals, such as olivine and clinopyroxene (Karato, 2003). The ability for a planet to acquire and retain surface water over geological timescales thus appears to be a critical factor for determining the viability of plate tectonics (P^ge auer-Lieb et al., 2001; Lecuyer, 2013; Wade et al., 2017) and should be considerr d al ongside other important astronomical factors when predicting the habitability of ni. nets outside of our solar system. \nWhen did plate tectonics initiate on Eart.? Given that independent plate motion must be facilitated by a global network of plate Loundaries, evidence for isolated occurrences of subduction at any point in time is ot  ough to justify the operation of this planet-wide geodynamic regime. This sobe. ing fact is undoubtedly the reason for such contention in the literature, where the wide ran.  of interpretations of the timing of onset of plate tectonics presented in Fig. 3 sten. trom the reliability of different lines of evidence for satisfying this “global’criterion. Additional opaqueness comes from the likely interpretation that the initiation of subduction occurred over an extended period, and so it is unreasonable to assign a well-defined age to this onset, as is often the case in the literature. In a recent review of secular change, Palin et al. (2020) divided indicators of subduction preserved in the geological record into three groups - petrological, tectonic, and geochemical/isotopic. Although not data in the purest sense of the word, the results of thermo-mechanical (geodynamic) and/or petrological modeling can also be used to interpret the timing of \nsubduction initiation by comparing simulation output to real-world observations. We follow this scheme again here by briefly outlining evidence for plate tectonic processes for each category, and the strengths and weaknesses of each. \nmargin settings, including those belonging to the downgoing slab and the overlying arc. If these lithologies are discovered in the rock record and can be r liat!y dated using geochronology, they would represent firm evidence of sub uc ion having operated at that point in Earth history, although this need not have been au  global scale. Associated evidence of horizontal plate motion may be inferred from rock, thet are diagnostic of oceanic spreading ridges - for example, mid-ocean rid e a alt (MORB) and associated sheeted dike complexes s although these features alon. not require subduction to be operating elsewhere on a planet, as lithosphere m.y be readily destroyed in non-plate boundary settings \nA key group of petrological . d cators used to identify subduction is high-pressure/lowtemperature (HP/LT) m、tamorphic rocks, such as blueschist and jadeitite (e.g. Stern, 2005; Stern et al., 2013). These lithologies form exclusively in subduction zones along geothermal gradients of ~150-440 °C/GPa (Fig. 4; Ernst, 1988; Sorensen et al., 2006; Palin and White, 2016) due to metamorphism of hydrated basalt and metasomatism of the mantle wedge just above the slab interface, respectively. Blueschists and jadeitite also often occur as exotic blocks in serpentinite-bearing melanges, confirming a subduction zone environment of formation (Tsujimori and Harlow, 2012). Eclogite is often considered within this HP/LT category of rocks that are diagnostic of subduction zone metamorphism, although deeply \nburied mafic roots of overthickened continental crust - such as in the Pamir region of the Himalayan orogen (Hacker et al., 2005) - show that some eclogite can form by extreme crustal deformation and thickening (Austrheim, 1991). Nonetheless, eclogite with either MORB geochemistry or containing the minerals lawsonite and/or glaucophane is diagnostic of metamorphism in subduction zones (Becker et al., 2000; Palin and Dyck, 2018). The polymorphic transition of quartz to coesite defines the boundary between HP and UHP metamorphism, which occurs at ~ 26 kbar at 500 °℃ and ~28 kbar at 900 °C kbar (Chopin, 1984; Liou et al., 2004). As such, coesite-bearing eclogite repren exceptionally deep burial and exhumation of crustal materials from a depth of at I ast 100 km in the mantle, which is difficult to explain without invoking steep subdu. tion of oceanic lithosphere (e.g. CO Jahn et al., 2001). \nIndia, and western China: Maruyama et l., 1996), c. 0.63 Ga (Pan African orogenic belt, Southwestern Brazil; Liou et al., 2009)and c. 0.47 Ga (Oya-Wakasa, Japan; Nishimura and Shibata, 1989), respectively, air. hough HP eclogite, with or without MORB geochemical signatures, occurs in several a eoproterozoic terranes worldwide (see below: Fig. 4). The marked increase in abun. ance of these HP/LT rock types during the Neoproterozoic has been attributed to many factors, including a late onset of global subduction at that time (e.g. Stern, 2005). However, in light of other lines of evidence suggesting plate tectonics having begun prior to c. 0.9 Ga (Fig. 3), preservation bias likely also plays a key role in overprinting older occurrences (Whitney and Davis, 2006), a change in exhumation mechanism may have taken place during the Neoproterozoic (Agard et al., 2009; Palin et al., 2020) such that older examples were unable to return to the Earth\'s surface, or else the hotter Archean mantle (Fig. 2) may have increased subducted slab-top geotherms so that diagnostic low-temperature \nminerals, such as glaucophane and lawsonite, could not stabilize (cf. Early and Late Archean subduction zone geotherms in Martin and Moyen, 2002). A recent model, supported by observed secular changes in basalt compositions through time (Keller and Schoene, 2012 Furnes et al., 2014), is that a cooling of the mantle and an associated decrease in the maficity of oceanic crust through time gradually allowed sodic amphibole (glaucophane) and lawsonite to stabilize in Neoproterozoic (and younger) low-MgO hydrated basalt (Palin and White, 2016). In this scenario, older Paleoproterozoic and Archean high-MgO hydrated basalt would have formed actinolite and chlorite-rich assemblages at ualent HP/LT subduction zone conditions (Palin and Dyck, 2018), which resemble g.ee. schist-facies assemblages that occur throughout Archean greenstone belts. Thus, detailed geochemical investigation and thermobarometry are required to assess whether inceisp.^uous greenstone-like units in ancient terranes record hidden evidence of sub lu、 ticn-related HP metamorphism (e.g. Francois et al., 2018). \nA final note on this topic must be mac.^ oncerning the relevance of HP vs. UHP eclogite as an indicator for the operation o. olate tectonics. Geodynamic arguments (see section 6.4) suggest that subduction on a^er early Earth would have occurred at shallow (<10°) angles if it did at all such t t it may have been impossible for subducted crust to reach UHP conditions. Even if subduction operated at high angles, it is also notable that hotter Archean slabs are predicted to have been mechanically weaker than colder Phanerozoic counterparts, meaning that they would lose coherency during subduction and break apart at shallow depths before reaching the HP-UHP transition (Van Hunen and Moyen, 2012). Detached and eclogitized slab fragments that had transformed to become denser than the surrounding mantle and would terminally sink into the deep Earth (Aoki and Takahashi, 2004), achieving UHP metamorphic conditions, but never able to return to the surface for study. By contrast, \nrecording HP peak metamorphic conditions. Thus, the presence of coesite should therefore be viewed as sufficient, but not necessary, for identifying steep subduction during the Archean. With this in mind, it is notable that several HP eclogites occur in Paleoproterozoic terranes (Fig. 4) with ages c. 1.8 Ga to c. 2.1 Ga, including the Congo Craton, Democratic Republic of the Congo (Francois et al., 2018), the Nagssugtoqidian Orogen, south-east Greenland (Miller et al., 2018a, b), and the Trans-Hudson Orogen, Canada (Weller and St-Onge, 2017). Although individual occurrences of HP eclogite may be viewed as otential evidence for localized subduction systems, similar lithologies forming ia n. ultiple terranes in the same ~300 Myr period is notably more likely to support a gloha. network of plate boundaries having been established at that time (cf. Wan et al., 202) The curious paucity of HP eclogite in the rock record between 1.8 and 0.8 Ga (Fig. 4 i yet to be satisfactorily explained, although coincides with a global period ft ctonic quiescence ethe Boring Billion (Roberts, 2013). Finally, brief discussion must be made on mafic eclogite from the Kola Peninsula, Russia (Mints et al., 2010), and Fenc  andian Shield (Dokukina et al., 2014), which are reported to have equilibrated a. P-1 conditions of ~16 kbar and ~750 ℃ at c. 2.87 Ga, and ~24 kbar and ~700 ℃ at c 2.32 -2.72 Ga, respectively. While these examples may be considered by some to u 丶 tue oldest known HP examples, there is much debate about the age of metamorphism for these localities (Mints and Dokukina, 2020), with other researchers arguing that they formed during later regional tectonic overprinting during the Svecofennian \nOphiolite complexes represent alternative petrological evidence for subduction, as they represent fragments of oceanic lithosphere that have been tectonically emplaced (obducted) \nrepresent fragments of oceanic lithosphere that have been tectonically emplaced (obducted) \n(c. 2.0 Ga; Scott et al., 1991, 1992), which lies within the Trans-Hudson orogen, Canada; a Proterozoic collisional orogen with many temporal and spatial similarities to the Cenozoic Himalayan orogen (St-Onge et al., 2006). However, Santosh et al. (2016) documented a Late Neoarchean ophiolite from the c. 2.5 Ga Yishui complex, North China Craton, with its lithology, petrology, and geochemistry confirming a suprasubduction zone genesis. Although Kusky et al. (2001) proposed that the Dongwanzi greenstone h^lt ( 2.51 Ga), North China Craton, contains dismembered fragments of an Archean or nic\'ite sequence, this interpretation has been disputed by many other research g. ups (Zhai et al., 2002), as have sheeted dikes and associated pillow basalts in the Isu. s..racrustal sequence (c. 3.8 Ga). Greenland, reported by Furnes et al. (2007) an 1. n.er et al. (2009). Recent studies have also reported well-preserved ophiolite-like su.e.sions of Neoarchean age such as those from the Miyun Complex in the North China Craton (e.g., Santosh et al., 2020). These ancient examples are less readily accepted s ducted Archean oceanic lithosphere by the broader geoscience community due to .. eir incompleteness, as individual components of ophiolites such as sheeted dikes and nin" basalts - may form individually in non-subduction zone tectonic settings (Moon et al., 1982; Vanko and Laverne, 1988). However, additional petrological evidence in some localities supports the interpretation that these greenstone belts do represent metamorphosed oceanic crust (cf. Tang and Santosh, 2018). Arc-type andesitebearing greenstone belt volcano-sedimentary successions occur in the Superior, Slave, and Yilgarn Archean cratons, among others (cf. Boily and Dion, 2002). These andesitic members are intercalated with graywacke and other volcaniclastic strata that commonly occur along modern-day continental and island arcs, such as boninite, shoshonite, and high-Mg andesite \nsedimentary stratigraphic package, subduction-zone processes represent the most likely explanation for their genesis. \ndescribes large-scale geological features that were created by dominantly horizontal tectonic forces. Evidence for the former is readily provided by paleomagnetism, although this technique can be challenging to apply to rocks formed on the erly Earth (Van der Voo and Channell, 1980). Typically, paleomagnetic studies and the ide. tification of apparent polar wander in Archean terranes is complicated by the lack t _ itable stratigraphic sections that are horizontal, have remained undeformed, and have not been remagnetized since acquisition of their primary magnetism. Further issues aric e , it\' providing geological constraints for different sedimentary or volcanic formau. n , due to uncertainties associated with many isotopic dating techniques increasing with absolute age (Schoene et al., 2013). Nonetheless, several studies have managed to ciu. ent these issues. In particular, a recent study by Brenner et al. (2020) presented new paleomagnetic data from tholeiitic metabasalts in the East Pilbara Craton, western . vstralia, and demonstrated that the different paleolatitudes of the terrane documenteq \'v sequential phases of volcanic activity required plate motion of at least 2.5 cm/yr between c. 3.35 and c. 3.18 Ga. This is comparable to documented rates of continental drift on the Phanerozoic Earth (~2-10 cm/yr) and exceeds those predicted for stagnant- and sluggish-lid models (up to 2 cm/yr; Fuentes et al., 2019), suggesting the \nIn parallel with paleomagnetism providing evidence of motion of individual continental blocks. larger-scale tectonic evidence of drift of multiple blocks is readily provided by the \nsupercontinent cycle. A supercontinent is a vast landmass formed by accretion of most (or all) continental fragments that exist on Earth at any point in time (Rogers and Santosh, 2004) Due to the limited degree of horizontal motion associated with various forms of stagnant lid regime, evidence of supercontinent formation provides strong support for mobile lid tectonics. The first undisputed supercontinent that formed on Earth assembled at c. 2.0-1.8 Ga, termed Columbia/Nuna (Rogers and Santosh, 2002; Meert and Santosh, 2017), and was followed by Rodinia (1.2-1.1 Ga), Gondwana (0.54 Ga), and Pangea (0.30-0.25 Ga) (Rogers and Santosh, 2004). Two supercontinents are also suggested by son.e researchers to have formed on the Archean Earth - Ur (3.0 Ga; Mahapatro et a r., 2012) and Kenorland (2.7-2.5 Ga: Aspler and Chiarenzelli, 1998) - and if true would pr vide strong support for a globally established network of subduction zones and operatin of the Wilson Cycle at that point in time. A diverse range of geodynamic models F as ^n proposed to account for this billionyear cyclical pattern of assembly and brek p of supercontinents (cf. Nance et al., 2014). Double-sided subduction (Maruyama e. l., 2007) and/or multiple sets of subduction zones within a single oceanic basin (Santsh . al., 2009) have been proposed to promote the rapid assembly of continental fragme ts into supercontinents. Supercontinent dispersal is thought to be driven by mantle plume^ ssociated with large igneous provinces and giant dike swarms, which have be temporally linked to the demise of Columbia/Nuna and Rodinia \nParallel and pseudo-linear belts that preserve low-temperature/high-pressure (LT/HP) mineral assemblages in one terrane and high-temperature/low-pressure (HT/LP) mineral assemblages in an adjacent terrane are called paired metamorphic belts (Miyashiro, 1961, 1973). These belts record convergent margin activity, where LT/HP metamorphism occurs in the subducted slab. forming blueschist- and eclogite-facies metamorphic rocks, and HT/LP metamorphism \nor ultrahigh temperature (UHT) rocks (Iwamori, 2000). Such belts record the penecontemporaneous metamorphism along contrasting apparent thermal gradients - one cold and one hot - in discrete terranes that are later tectonically juxtaposed (Oxburgh and Turcotte, 1971). The classical locality for paired metamorphism is the Sanbagawa Belt, Japan (Banno and Nakajima, 1992), although similar belts have been documented in Precambrian terranes (e.g. Katz, 1974). Paired metamorphic belts therefore record many forms of arcrelated activity, such as subduction and crustal shortening and thick ning. o0 \ncharacterize ongoing subduction, the closing phase of th、 Wilson Cycle is documented by terminal destruction of an ocean basin leading to \' ision and amalgamation of multiple continental blocks and/or intervening aru sv tems (Wilson et al., 2019). Accretionary orogenesis typically occurs during ongoing subduction and evolves to collisional orogenesis during continental accretion (Caw^od * al., 2009; Santosh et al., 2009). Accretionary orogens exhibit accretionary c nplexes containing MORB and deep-sea sediments belonging to the subducting oceanic nla.^ and medium- to high-grade metamorphic rocks and calcalkaline/I-type batholith. belonging to the overlying continental plate (Bahlburg et al., 2009 Sepidbar et al., 2019), which are separated by a forearc basin (Hall, 2009). By contrast, collisional orogens are characterized by passive continental margin sequences (Gaetani and Garzanti, 1991), with an orogenic core of medium- to high-grade regional metamorphic rocks (Etheridge et al., 1983; Weller et al., 2013; Palin et al., 2018; Treloar et al., 2019; Kang et al., 2020). A collisional suture with remnants of oceanic components marks the zone of ocean closure (Thakur and Misra, 1984; Robertson, 2000; Palin et al., 2015; Parsons et al., 2020). Accretionary orogens often contain accretionary prisms - accumulations of material scraped \noff subducting oceanic lithosphere that show a downward younging of successive strata (Huang et al., 1997). The relative volume of individual units in accretionary prisms also typically decreases with age, that some portion of the accreted material is tectonically eroded and carried into the mantle via subduction erosion (Isozaki et al., 2010). This process can lead to underplating of overlying arc crust with felsic sedimentary material and allows hydration of the mantle wedge (Platt et al., 1985; Hacker et al., 2011). Accretionary prisms are sparse the geological record before c. 0.9 Ga (Hamilton, 1998), although several melanges in Archean terranes have been interpreted as accretionary prisms inci ding the SchreiberHemlo greenstone belt (c. 2.75-2.70 Ga), Superior Provin e, anada (Polat and Kerrich, 1999) and the Abitibi greenstone belt (c. 2.70 Ga), Quehe (Mueller et al., 1996). 5 \nMany forms of geochemical and isotopic le.a can be used to infer the operation of plate tectonics through geological time. The tonic environments in which igneous rocks formed are commonly constrained using trce olement ratios, particularly for mafic rocks, which can be used to identify depleted ma tle (DM), enriched mantle (EM), and hydrated mantle (HM) source regions (e.g. Workma. .id Hart, 2005; Pearce and Stern, 2006). Basalts with these geochemical signatures . re often interpreted to have formed at mid-ocean ridges, on oceanic plateaux above mantle plumes, and in arc/back-arc settings where partial melting takes place within a hydrated mantle wedge, respectively (Condie, 1985). Many researchers have applied these trace element discrimination diagrams to Archean and Proterozoic basalts in greenstone belts to determine whether these mantle reservoirs existed at various points in time (e.g. Furnes et al. 2014); however, caution is advised, as some studies have shown that these techniques are not always reliable at identifying tectonic settings on the young Earth where \nthe mode of basalt formation can be independently verified by other geological criteria (Snow, 2006; Vermeesch, 2006; Li et al., 2015). \nrepresent obducted and metamorphosed components of Precambrian oceanic crust, as such. application of trace element discrimination techniques to their mafic components should be able to verify the geodynamic setting of protolith (basalt) formation, assuming that no significant modification of the elemental ratios involved has taln !!ace during subsequent heating and burial. Furnes et al. (2014) used multiple inco upa ible element ratios (Th/Yb Nb/Yb. V/Ti) to interpret that most basalts from Archeon g reenstone belts formed in convergent margin tectonic settings due to the preser vau n of geochemical signatures similar to Phanerozoic MORB, boninite, and island arite. By contrast, Condie et al. (2016) suggested that modern-day tectonic setti s cannot be confidently identified in rocks older than c. 2.5 Ga, as distinct EM and DM signatures only become resolvable after that time. A critical limitation to applying thes^ ge  nemical techniques to define when plate tectonics began on Earth is the issue of d fining what major-, minor-, and trace-element signatures basalts generated in various t..s of stagnant lid regime should exhibit (e.g. HernándezMontenegro et al., 201s, Aithough mantle plume-related magmatism occurs on Earth today, complicating factors such as progressive depletion of the upper mantle through time and the uncertainty concerning the rate and degree of secular cooling (e.g. Ganne and Feng, 2017) introduce uncertainty into forward models of partial melt composition that depend on factors such as protolith composition, pressure and temperature conditions of melting (Weller et al., 2019; Hernandez-Uribe et al., 2020a), and degree of fractional crystallization, mixing, and assimilation during magma ascent through the crust (Hastie et al., 2015). In particular, HM trace element ratios in basalt are viewed as diagnostic signatures of magma genesis at oceanic \nor continental arcs during the Phanerozoic, but have recently been suggested to alternatively represent intraplate mantle that has been metasomatized by assimilation of dripped or delaminated hydrous lower crust (e.g. Bedard, 2006; Fischer and Gerya, 2016; Piccolo et al., 2019). \ngeodynamics through time can be obtained from the geochemistry and isotopic signatures of individual crystals within metamorphic and igneous rocks. Diamon. is of critical use for studying secular change in global geodynamics, as it is ph sic lly and chemically resistant to tectonothermal overprinting and stabilizes at pressures eq.ivalent to ~150-180 km depth below the Earth\'s surface (Sung, 2000). Natural diaron\'s crystallize from carbon-rich solutions in the mantle and can trap minerals, lu. +s or melts that occur at equivalent depths within the Earth\'s interior (Harte, 2010). As such, they have been used in many studies to examine how mantle “contaminants\' ha.  evolved through time through studies of their inclusion suites and their isotopic n.sitions. For example, mineralogical evidence of the transition between stagnant lid nd inobile lid geodynamic regimes during the Mesoarchean was provided by Shirey and ichardson (2011), who studied silicate and sulfide inclusions in diamonds from five ma r Archean terranes. While peridotite-like inclusion suites (harzburgite and lherzolite) occur in diamonds of all ages, eclogite-like inclusion suites (garnet plus omphacitic clinopyroxene) became dominant after c. 3 Ga. These data were interpreted to record the onset of global subduction on Earth that allowed eclogite metamorphosed oceanic crust - and carbon-bearing fluids to be transported to subcontinental mantle depths, with the diamonds subsequently exhumed via volcanism. In an analogous fashion, stable isotope ratios in cratonic diamonds may constrain the onset and degree of \nJagersfontein kimberlite, South Africa (Tappert et al., 2005), and carbon and nitrogen isotopes in diamond from the c. 3.5-3.1 Ga Kaapvaal craton, South Africa, (Smart et al., 2016) were reported to record evidence for the transport of oceanic crust and oxidized carbon-rich sediments into the mantle, presumably facilitated by subduction of oceanic lithosphere at a convergent plate margin. Oxygen and strontium isotope signatures in Archean diamonds from eclogite xenoliths exhumed from cratonic mantle in South Africa (MacGregor and Manton, 1986) are similarly thought to document subduction of hydrothermally altered oceanic crust into the mantle at c. 2.5 C. \nBoth thermo-mechanical (numerical) and petrologic?l (u.ermodynamic) modeling can be used independently or in combination to infer he lil.elihood of subduction at different times through Earth history (e.g. Palin et al., 2c16; Ge et al., 2018; Wiemer et al., 2018). This is best achieved by correlating the surficia! imprints of key tectonic processes and/or the geochemistry and metamorphic/m ^on.^*c P-T evolution of rock types that are predicted to form in both stagnant lid and n. bile lid environments with those documented in the \nThermo-mechanical modeling can be used to test how different physical variables affect evolution of the crust and mantle, and remains a highly effective method to examine the geodynamic effects of secular cooling of the Earth\'s mantle through time (cf. Gerya, 2014). Examination of the thermal stability of thick, mafic Archean crust has shown that eclogitization and melt-loss from its roots would have caused dripping and/or delamination of this high-density material into the underlying mantle (Fischer and Gerya, 2016; Piccolo et al., 2017: Nebel et al.. 2018). It is primarily the results of such simulations that have allowed \n1. Such geodynamic simulations also demonstrate which petrophysical factors are necessary to initiate and sustain plate tectonics on Earth. Parameterizations have been employed that consider variations in oceanic lithospheric thickness, composition, and hydration state, and mantle Tp values for Archean, Proterozoic, and modern-day convergent margins (e.g. Gerya et al. 2008). In general, hot, thick, and highly mafic Archean oceanic slabs are not strong or dense enough to undergo steep subduction (van Hunen and Moyen, 2012), and commonly break apart when the leading-edge transforms to high-density log te. The well-documented importance of slab-pull forces for driving plate motion at t\'ie  urface of the Earth (Conrad and Lithgow-Bertelloni, 2002) indicates that subduction inr ely only became self-sustainable at a point in geological time when descending slabs vven. strong (and cold) enough to maintain down-dip coherency, arguing against m d n-day like subduction having operated on the much hotter early Earth (Foley et .l. 2003; Palin et al., 2020). \nBy contrast with thermo-mechanil deling, petrological modeling may be used to independently assess whether 1. cks exposed at the Earth\'s surface in Archean, Proterozoic and modern-day terranes fon.  via subduction (e.g. Ge et al., 2018). This form of modeling uses equilibrium thermu +vnamics to predict which minerals, melts, and aqueous fluids would stabilize at various depths and temperatures within the Earth (Powell et al., 1998; White et al., 2000, 2007; Green et al., 2016; Holland et al., 2018). If geochemical mass-balance constraints can be applied, in-depth analysis of the major, minor, and trace element contents of metamorphic rocks and anatectic melts can be obtained (Spear, 1988), which can then be C compared to natural lithologies preserved in different terranes worldwide (Palin et al., 2016c). Focused petrological study of Archean geodynamics has recently been facilitated by new thermodynamic descriptions of minerals and melts that may form in metabasalts (e.g. \nMORB, calc-alkaline basalt, ocean-island basalt), which are thought to have been precursor lithologies for generation of TTG magmas. Natural Archean TTGs and equivalent gray gneisses have historically been divided into low-pressure, medium-pressure, and highpressure variants based on geochemical signatures that imply magma genesis in the presence or absence of plagioclase, amphibole, garnet, and/or rutile (see Moyen and Martin, 2012 for a comprehensive review). Low-pressure TTGs are thus expected to have formed from partial melting of amphibolite, medium-pressure TTGs from garnet granulite, and high-pressure TTGs from eclogite (e.g. Foley et al., 2003). Such application f oetrological modeling has almost universally demonstrated that Earth\'s first continer .s u d not form via subduction, as all forms of TTG melts matching natural examples may b generated in normal crustal environments (Nagel et al., 2012; Palin et al., 2016b. Wr ite et al., 2017; Ge et al., 2018; Wiemer et al., 2018; Kendrick and Yakmychu, ^0; Laurent et al., 2020; Liu and Wei, 2020; Yakmychuk et al., 2020 and othernd calculations performed at mantle P-T conditions representative of subduction . one metamorphism shows that eclogite is highly infertile (Hernandez-Uribe et al., 2(h). Whilst TTGs with appropriate major-element  compositions and trace-elemen. signatures may be generated at these high-pressure conditions (e.g. Rapp et al120), the volumes produced cannot account for the proportions observed in Archean cr. ons. For more information about application of this petrological modeling to Archean metamorphism and TTG genesis, the reader is referred to Palin et al. (2016b) and Kendrick and Yakymchuk (2020). \nThe geological record becomes increasingly incomplete further back in time, which is expected due to older terranes having had more opportunity to be reworked via later episodes of tectonic deformation, overprinted by thermal or regional metamorphism, or eroded away \ninto their constituent grains. This presents many problems for geologists using the distribution of rock types through time as a tool to interpret secular changes in geodynamic processes; for example, arguments can be made about the absence of key petrological indicators of subduction, such as blueschist, prior to c. 0.8 Ga being due to lack of preservation rather than lack of formation, as they are easily retrogressed. Analogous problems arise when making interpretations from data obtained from individual outerops of Archean age, which may not be representative of global conditions at the time of their formation. Unfortunately, this is a limitation that will likely neuer L  circumvented unless there is an important discovery of new Archean crust in re :1ors of the world that are currently not fully explored. \nThe search for Earth\'s oldest rocks is of criticah. nortance for answering a wide range of questions related to our planet\'s evolutio. cluding the nature and style of its initial tectonic regime. However, as with many aspects of such studies, fervent dispute exists with respect interpretation of data reported from di f rent localities. Today, the oldest-known rocks on Earth are commonly accepted  occur within the Acasta Gneiss Complex, the westernmost exposure of the basement ot  Slave Craton, northwest Canada (Bowring et al., 1989). This Complex contains a peu logically diverse suite of rocks ranging from metagabbro to granitic orthogneiss that mostly have metamorphic ages of c. 4.02-3.6 Ga (e.g. Stern and Bleeker, 1998: Bowring and Williams, 1999). The timing of metamorphism and melting in these rocks has been tightly constrained by U-Pb zircon geochronology (e.g. Reimink et al., 2014, 2016), which is generally considered a reliable petrochronological technique for producing highprecision ages in ancient rocks (e.g. Montgomery, 1979; Kohn et al., 2015). Further, the changing chemical systematics of zircon during metamorphism and partial melting are well studied and well understood (Lee et al., 1997; Rubatto and Hermann, 2007), such that it is \nratios of trace elements and/or REEs in different microstructural domains, such as extraction of a primitive melt from the mantle and subsequent metamorphism in an orogenic environment. However, zircon is rare in mafic and ultramafic rocks, meaning that other minerals and isotope systems are often required to date them. In a landmark study, O\'Neil et al. (2008) reported a 146Sm-142Nd isochron age of c. 4.28 Ga from amphibolite-like mafic schist from the Nuvvuagittuq greenstone belt, Quebec, Canada, making them contenders for being named as Earth\'s oldest crust; however, these data have rown contentious (Andreasen and Sharma, 2009), given assumptions of the initial conce .tra. on of the “Sm parent isotope on the early Earth, which is now extinct. Key aspects of th geology and tectonic interpretations for both localities are briefly summari zeu helow, although for a more comprehensive review of the nature of Earth\'s fn. t rust that encompasses many recent discoveries and tectonic models, the read. r ’s referred to Carlson et al. (2019). \n(2016) divided into four main t pes oased on age, structure, and petrology: a layered gneiss unit composed of meter-scale tohalitic and granodioritic members; foliated, garnet-bearing amphibolite; weakly de. rmed metagabbro that preserves some relic igneous textures; and a dominant, massive orthogneiss with granodioritic to granitic compositions. The oldest lithological components of this suite are low-strain, mafic tonalitic gneisses of the Idiwhaa unit, which contain igneous zircons with U-Pb crystallization ages of c. 4.02 Ga (Reimink et al., 2014). These felsic gneisses were reported by Reimink et al. (2014) to be unusually Ferich (~9-15 wt. % FeO) and so have lower Mg-numbers (~13-18) than typical Archean gray gneisses (~25-60, with a median of ~43; Moyen, 2011), which in turn was interpreted to record shallow-level fractional crystallization of a low-H O basaltic parent magma. Oxygen \nmost likely tectonic scenario for generating such melts is an Iceland-like environment where mantle upwelling generated a thick oceanic plateau that experienced intracrustal melting, differentiation, and magma hybridization (Kroner, 1985; Reimink et al., 2014), which aligns with suggestions that the very early Earth experienced more intense plume-related magmatism than during the Proterozoic and Phanerozoic (Bedard, 2018) and that a wide variety of magmas may be produced in such intraplate environments (e.g. Hastie et al., 2010. 2016). \nThe Nuvvuagittuq greenstone belt, Superior Craton, is a tc\'atively small (6 km‘) terrane, but exposes a wide variety of rock types, including felsic to . termediate orthogneiss, ultramafic and mafic sills, and metasediments (e.g.O\'Ne\'le a\'., 2007). Much focus has been given in recent years to the petrology of mafic sup ra rustals s amphibolite-like rocks, termed the Ujaraaluk unit - that were reported by \'Neil et al. (2008) to have a *\'Sm-142 " whole-rock isochron Hadean age of c. 4.28 G Fi3). Many of these mafic units show major minor, and trace element compositional si. ilanty to metabasalt from several Early Archean terranes worldwide (Carlson et al. 2610), although those in the Ujaraaluk unit typically contain cummingtonite instead f nornblende (O\'Neil et al., 2008). Based on compatible and incompatible trace element ratios, these faux-amphibolites have been interpreted to have formed from basalt derived directly from a peridotite mantle (O\'Neil and Carlson, 2017) and thus may represent subsequently deformed and metamorphosed relics of Earth\'s oldest secondary crust. \nDespite the ancient heritage of these rocks from the Nuvvuagittuq greenstone belt and Acasta Gneiss Complex. even older terrestrial materials occur in the form of detrital zircon grains \nwithin clastic metasediments in the Jack Hills area of the Archean Narryer Terrane, Western Australia (e.g. Hoskin, 2005). Early investigation of a greenschist-facies meta-conglomerate from this region by Compston and Pidgeon (1986) revealed two zircon grains with ages of 4276±12 Ma, and further investigation of grains from the same locality by Wilde et al. (2001) revealed a single grain with a ""Pb/Pb age of 4404 ±8 Ma, the oldest ever obtained from a mineral formed on Earth. Subsequent analyses have shown that Jack Hills detrital zircons show a characteristic bimodal distribution with peaks at c. 3.3 and c. 4.1 Ga (cf. Harrison, 2009).Textural characteristics of the Jack Hills zircons s.ch as morphology and internal growth zoning, indicate that virtually all are deriv d r.om igneous sources (e.g. Cavosie et al., 2004); thus, the older (Hadean) age peak m.y be considered as a magmatio crystallization age, and the younger (Archean) age p akkely records metamorphic recrystallization and/or isotopic resetting. Alth ou h other suites of Hadean zircons exist elsewhere on Earth, including Greenland Mojzsis and Harrison, 2002), China (Cui et al., 2013), and South America (Paquette et .!, 2015), most study has concentrated on the Jack Hills materials and discussion of the i. formation gleaned about the Hadean Earth, below, focuses on studies of this set. \nHadean zircons provide riucal information about the geochemical conditions and petrology of the rocks in which they formed, and so the geodynamics of the Earth at that time. This information primarily comes in two forms: chemical and isotopic properties of the zircons themselves, and the mineralogy of inclusions within them. Several independent studies of Jack Hills zircon have reported a heavy oxygen isotope signature (Mojzsis et al. 2001; Wilde et al., 2001) that may be explained by the melt from which these grains crystallized having formed from "O-rich clay minerals. In turn, this implies that liquid water was present at the Earth\'s surface at c. 4.4-4.3 Ga. This conclusion is further supported by highly negative \nvalues of o\'Li from Jack Hills zircons that reflect crystallization from a source rock that was strongly weathered (Ushikubo et al., 2008; Tang et al., 2017). Both sets of isotope data may be satisfactorily explained by weathering of pre-existing crust and formation of a clay-rich sediment at the Earth\'s surface, which was buried perhaps via subduction heated, melted, and crystallized zircon. \nbeen inferred from initial "“Hf/\'"Hf ratios in Jack Hills zirco.o, wi.ich exhibit large deviations in eHf(T) from the bulk silicate Earth (Kinny et al., 1991; Harrison et al., 2005) ranging mostly between -10 and +4 (Harrison, 2009) Tis has been interpreted to reflect early major differentiation of the silicate Earth (Blic\'ert- Toft and Albarede, 2008) and primary crust formation since c. 4.5 Ga. Critic lly, mlany of these analyzed ratios cluster along a trend corresponding to a Lu-Hf v.  e of ~0.1, which is characteristic of continental crust, and has led to many models of con. inental crust formation through time incorporating substantial growth immediately afue" the Earth\'s formation. The absence of this crust from the geological record is commonly . tributed to destruction and re-working due to a purported intense bolide impact flu.* c. 5.9 Ga, often termed the late heavy bombardment (c. 3.9 Ga; Wetherill, 1975; Gomes、+ al., 2005; Chapman et al., 2007). The effects of high-velocity meteorite impacts on the Earth\'s primitive crust have been speculated upon by many researchers, with some suggesting that impacts may have triggered subduction initiation (O\'Neill et al., 2017, 2020) and induced significant fracturing, weakening, and hightemperature/short-duration metamorphism at impact sites (Byerly and Lowe, 1994; Gibson, 2002; French, 2004; Sleep and Lowe, 2014). As with many other aspects of Earth\'s early history, study of similar processes on our neighboring rocky planets Mars and Venus - and the Moon - may shed new light on the evolution of the Hadean Earth. \nMany workers have reported the mineralogy and crystal-chemistry of inclusion suites within Jack Hills zircons (e.g., Bell et al., 2015, 2017; Cavosie et al., 2004; Caro et al., 2008; Menneken et al., 2007; Nemchin et al., 2008; Rasmussen et al., 2011), which have provided profound insight into the tectonic processes that operated at this point in Earth history. These observations have been used to support and complement suppositions made by some workers from isotope analysis that surficial crustal material was transported to pressure and temperature conditions within the Earth that allowed anatexis t taxe place, specifically in a subduction zone environment due to the cold P/T gradient in olved (see below). Primary inclusions documented within Hadean zircons worldwide I clude (but are not limited to) quartz, muscovite and biotite mica, chlorite, K-feldsr ar and albitic plagioclase, rutile, monazite, xenotime, and even diamond (Maas et 1 1992; Trail et al., 2007; Menneken et al. 2007). A campaign-style analysis of zirc ns rrom Jack Hills by Hopkins et al. (2008) showed that quartz and muscovite comprise nea.\'v two-thirds of all inclusions, and that these minerals often occur in close spati^l a  ciation with mutual grain boundaries, implying chemical and textural equilibrit m. \nThe common occurrenc. or nydrated mineral inclusions (muscovite, biotite, chlorite, and apatite) that are characteristic of peraluminous igneous rocks can be attributed on the modern-day Earth to either melting of clay-rich metasediments during regional metamorphism - as shown by syn- and post-orogenic Himalayan-type leucogranites that form in the cores of collisional mountain belts - or by production of andesite-like magmas in an island or continental arc setting (Chappell, 1999; Collins and Richards, 2008). Felsic melts may alternatively be produced as highly fractionated differentiates of originally mafic magmas, such as occur in trondhjemitic dikes that formed by hydrous partial melting of \ngabbro in the roof-zone of an axial magma chamber in the Semail ophiolite, Oman (e.g. Rollinson, 2008), although these occurrences are much less common than orogenic S-type magmas. Nonetheless, all these scenarios are characteristic of mobile lid geodynamic regimes with magma genesis at sites of plate convergence. \nenvironment has been put forward due to the results of thermobarometry performed on each. The Ti-in-zircon thermometer (Watson and Harrison, 2005) arplied to zircon grains with ages c. 4.4-3.9 Ga produced a mean crystallization temper atu e of ~680-690 ℃, which lies close to the wet melting curve for pelite and granite at D>4 kbar. In addition, the Si contents of muscovite inclusions were used in combination with hase diagram-based modeling of granitic magma genesis by Hopkins et al. (2003) ^onstrain a mean crystallization pressure of ~6.9 kbar (at ~680-690 ℃), and thus . st.itic and linearized geothermal gradient of ~980 C/GPa. Interpretation of what these P-T conditions mean for the geodynamics of the Hadean Earth is complex. As noted in sction 6.1, most rocks diagnostic of subduction on the Phanerozoic Earth, such as blut schist and lawsonite-bearing eclogite, form at P/T gradients <440 °C/GPa (Penniston-Dolar.d et al., 2015; Palin et al., 2020). Thus, while Hopkins et al. (2008) and others have I terpreted that these zircons formed from melts generated in an underthrust environment - perhaps similar to a modern-day subduction zone - the P/T gradient calculated from these inclusion suites is over twice as hot as this ‘upper\' limit for warm subduction, at least on the Phanerozoic Earth. These data therefore may provide primary constraints on the thermal structure of Archean subduction, which is otherwise \nand carbon isotopic signature of graphite and diamond inclusions. Ion microprobe analyses of individual and composite inclusions in zircon grains as old as c. 4.2 Ga by Nemchin et al. (2008) revealed strongly negative o C isotope values between -5‰ and -58‰, with a median value of -31o. These data were supported by similar analyses of graphite flakes included in c. 4.1-Ga zircon from the region by Bell et al. (2015), who produced o-C isotope values of -24±5o. The interpretation of these strongly negative values is contentious, as they are consistent with a biogenic origin, although not diagnc ouof it. Abiotic processes that may account for light o-C signatures, such as incorporati( n on meteoritic materials (oC values from +68‰ to -60%‰) or carbon isotopic fract on. tion by diffusion are considered unlikely to produce consistently low o\'C values over the range of ages of host grains analyzed in these studies (cf. Clayton, 1963: F bert and Epstein, 1982; Engel et al., 1990), giving weight to the hypothesis that primit. e biological activity was taking place at the Earth\'s surface at this time. Nonethe _^s, .n abiotic origin for graphite formation has recently been favored by Menneken et al. (2o\'7), who documented COz inclusions in Jack Hills zircons that also exhibited thi c. bon films on the inside of inclusion walls. This close spatial relationship betw en graphite and COz was suggested by to indicate precipitation of carbon during thermal me amorphism, and not as evidence for a terrestrial biosphere at c. 4 Ga. Regardless of the origin of the isotopically light carbon, undersaturation of carbon in the Earth\'s mantle requires that surficial sediments or crustal materials were transported into the interior at this time (Dasgupta and Walker, 2008). Unfortunately, these isotope data cannot directly determine whether subduction or other tectonic processes were responsible, such as dripping or delamination (Fig. 1), and thus other lines of evidence are needed to identify whether plate tectonics had begun to operate during the Hadean. \nStudy of the Archean Earth has become a major sub-category of geoscience, as demonstrated by the vast number of research articles that are published on the topic each year and the frequency with which review papers are required to keep up with new developments. In many cases, the major aim of these studies is to constrain the timing of onset of plate tectonics on Earth, and historical estimates in the literature span billions of years (Fig. 3). Some workers have used mineral inclusions in Jack Hills zircon and isotopic data for felsic crust present at the Earth\'s surface soon after planetary formation to propose suhdu. tion having begun during the Hadean (c. 4.2-4.0 Ga: Hopkins et al., 2008), whereas .no.t interpretations cluster around the Mesoarchean (c. 3.2-2.8 Ga: Cawood et al., 2006: van Kranendonk et al., 2007; Condie and Kroner, 2008; Tang et al., 2016; Palin et al., 2020) u. sed on the appearance of tectonic features resembling those that characterize Ph n oic collisional orogens, geochemical evidence for a rapid increase in primary 、or .inental crust thickness (Dhuime et al., 2017) paleomagnetic evidence for continentar vift (Brenner et al., 2020), and evidence for operation of the Wilson Cycle (Shirey nd Richardson, 2011). A striking gap exists between c. 2.9 Ga and c. 1 Ga, overlapp.ng with the Boring Billion (c. 1.8-0.8 Ga), and is terminated by a separate cluster of rearhers who argue for a Neoproterozoic onset (c. 1.0-0.8 Ga; Stern, 2005; Hamilton, 2011; Stern et al., 2016). \nA holistic model of changing geodynamics through time should take into account many of the strong arguments for subduction having begun to operate in the deep geological past - very likely in isolated micro-cells that were located at the head of mantle plumes (Fig. 5a-b). The occurrence of multiple mantle plumes on the early Earth infers the existence of multiple microcells, and it is conceivable that interactions between these cells could produce plate margin-like features, such as collisional orogenesis (Fig. 5c-d), although in the absence of a \ndirected to Palin et al. (2020). This regime of isolated microcells with localized subduction zones eventually transitioned into a global-scale phenomenon as secular cooling of Earth\'s mantle allowed oceanic lithosphere to become stronger and less buoyant. The character of subduction has undoubtedly changed through time in many other ways and has impacted the diversity of its tectonic, petrological, and geochemical products preserved in the geological record. Several lines of evidence support the hypothesis that cold, deep, and steep slab subduction is a recent (<0.9 Ga) phenomenon, which is exemplifiec by the abrupt emergence of key rock types, such as blueschist and UHP eclogite, of ula. age (e.g. Fig. 4). Evidence for plate motion and continental and island arc-related activit, before this point in time, such as the supercontinent cycle, can be readily accounted fo. by shallow subduction/underthrusting that is also documented on Earth today. A red ct. n in the average temperature of such shallow subduction zones accounts for s ^u\'ar changes in TTG composition (Martin and Moyen, 2002) - of which many require formation at pressures only achievable via subduction and the increasing number of no-U eclogite with MORB-like affinity in the \nAs the geological recor. becomes more fragmented with age, various forms of modeling begin to provide more in-depth insight into the likely geodynamics of the Archean (and Hadean?) Earth. Thermo-mechanical modeling argues strongly for one of many forms of stagnant lid tectonics before c. 3 Ga (Fig. 6) where the Earth was dominated by vertical plate motion and intracrustal differentiation, producing the bimodal TTG and greenstone lithological associations that are typical of Archean cratons (e.g. Piccolo et al., 2020). Poor constraints on key petrophysical properties, such as mantle Tp, obviate definitive statements concerning the style of stagnant lid regime that occurred at any point in time, although \nused to supplement the results of numerical simulations. These suggest that the Archean Earth transitioned from an environment characterized by extensive volcanism (heat-pipe world) to one characterized by intrusive magmatic activity (plutonic squishy lid), thus thickening the crust with time. Little is known about the Hadean environment, as samples are restricted to mafic supracrustal rocks in the Nuvvuagittuq greenstone belt (c. 4.28 Ga) and xenocrystic zircons within younger (Archean) metasedimentary rocks, such as quartzite from the Jack Hills region of western Australia (see section 7). Nonther ss, this small suite of zircon grains has provided a wealth of information about t\'e ikely geochemical, mineralogical, and isotopic character of the crust and man.\'e at this enigmatic time in Earth history, as well as potentially providing evidence for an 、merging biosphere less than 300 Myr after planetary accretion. \nWhile most of the geoscience community is arriving at a consensus about these secular changes, there are several key are^^ or rsearch that may yet make substantive impact on our current understanding. Firstly, ontimued debate concerning the magnitude of secular cooling and absolute temperatures oi th Archean mantle has stymied advances in petrological and geodynamical interpreta ons of early Earth terranes. Many models are predicated on the supposition of a “hot\'Archean mantle, as indicated by primary magma solutions determined from non-arc basalts by Herzberg et al. (2010). However, subsequent studies have argued for a cooler mantle Tp, albeit still hotter than the present day (Fig. 4). While these differences in magnitude are somewhat small (AT~100-300℃), thermo-mechanical simulations suggest that they are significant enough to have dramatic consequences for the predicted forms of geodynamics and timing of onset of subduction (e.g. Piccolo et al., 2019). Developing new techniques to constrain mantle Tp and/or extracting higher-precision information from current \n<User Question>:\nHelp me extract the sampling locations in the text\n<Return Result>:\n'