Accepted Manuscript

Initiation of plate tectonics in the Hadean: Eclogitization triggered by the ABEL Bombardment

S. Maruyama, M. Santosh, S. Azuma

PII: S1674-9871(16)30207-9 DOI: 10.1016/j.gsf.2016.11.009 Reference: GSF 514

To appear in: Geoscience Frontiers

Received Date: 9 May 2016 Revised Date: 13 November 2016 Accepted Date: 25 November 2016

Please cite this article as: Maruyama, S., Santosh, M., Azuma, S., Initiation of plate tectonics in the Hadean: Eclogitization triggered by the ABEL Bombardment, Geoscience Frontiers (2017), doi: 10.1016/ j.gsf.2016.11.009.

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MANUSCRIPT

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1‐ Initiation of plate tectonics in the Hadean:

2‐ Eclogitization triggered by the ABEL

3‐ Bombardment

4‐

5‐ S. Maruyama a,b,*, M. Santosh c,d,e , S. Azuma a

6‐ a Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1, 7‐ Ookayama-Meguro-ku, Tokyo 152-8550, Japan 8‐ b Institute for Study of the Earth’s Interior, Okayama University, 827 Yamada, 9‐ Misasa, Tottori 682-0193, Japan 10‐ c Centre for Tectonics, Resources and Exploration, Department of Earth 11‐ Sciences, University of Adelaide, SA 5005, Australia 12‐ d School of Earth Sciences and Resources, China University of Geosciences 13‐ Beijing, 29 Xueyuan Road, Beijing 100083, China 14‐ e Faculty of Science, Kochi University, Kochi MANUSCRIPT 780-8520, Japan 15‐ *Corresponding author. E-mail address: [email protected]

16‐

17‐ Abstract

18‐ When plate tectonics began on the Earth has been long debated and

19‐ here we argue this topic based on the records of Earth-Moon geology and

20‐ asteroid beltACCEPTED to conclude that the onset of plate tectonics was during the middle

21‐ Hadean (between 4.37–4.20 Ga). The trigger of the initiation of plate tectonics is

22‐ the ABEL Bombardment, which delivered oceanic and atmospheric components

23‐ on a completely dry reductive Earth, originally comprised of enstatite 1‐ ‐ P a g e ‐|‐2222‐‐‐‐ ACCEPTED MANUSCRIPT ‐

24‐ chondrite-like materials. Through the accretion of volatiles, shock metamorphism

25‐ processed with vaporization of both CI chondrite and supracrustal rocks at the

26‐ bombarded location, and significant recrystallization went through under wet

27‐ conditions, caused considerable eclogitization in the primordial continents

28‐ composed of felsic upper crust of 21 km thick anorthosite, and 50 km or even

29‐ thicker KREEP lower crust. Eclogitization must have yielded a powerful slab-pull

30‐ force to initiate plate tectonics in the middle Hadean. Another important factor is

31‐ the size of the bombardment. By creating Pacific Ocean class crater by 1000 km

32‐ across impactor, rigid plate operating stagnant lid tectonics since the early

33‐ Hadean was severely destroyed, and oceanic MANUSCRIPT lithosphere was generated to

34‐ have bi-modal lithosphere on the Earth to enable the operation of plate tectonics.

35‐ Considering the importance of the ABEL Bombardment event which initiated

36‐ plate tectonics including the appearance of ocean and atmosphere, we propose

37‐ that the Hadean Eon can be subdivided into three periods: (1) early Hadean

38‐ (4.57–4.37 Ga), (2) middle Hadean (4.37–4.20 Ga), and (3) late Hadean ACCEPTED 39‐ (4.20–4.00 Ga).

40‐

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41‐ Keywords: Initiation of plate tectonics; ABEL Bombardment; Eclogitization;

42‐ Stagnant lid tectonics; Primordial continents

43‐

44‐ 1. Introduction

45‐ The Earth is the only example among all planets in our solar system with

46‐ active plate tectonics (Fig. 1), and also life-bearing since Hadean (e.g. Turner et

47‐ al., 2014; Ebisuzaki and Maruyama, 2016). This rocky planet is characterized by

48‐ both H 2O ocean and wide-spread granitic continents covering its surface. The

49‐ appearance of ocean triggered the operation of plate tectonics, which promoted

50‐ subduction of oceanic plate at the MANUSCRIPT trench and generation of TTG

51‐ (tonalite-trondhjemite-granodiorite) magmas at the continental region. As a

52‐ result, important nutrients are being continuously supplied for the survival for life,

53‐ together with CO 2, N 2, and H 2O as components of the building blocks of life.

54‐ Thus, the Habitable Trinity environment is sustained which is one of the basic

55‐ conditions for life. Plate tectonics, life, H 2O ocean, and granitic continents must ACCEPTED 56‐ genetically relate with each other (e.g. Dohm and Maruyama, 2015).

57‐ “When plate tectonics began on this planet” is one of the most heated

58‐ debates in Earth Sciences ever since the new paradigm of plate tectonics was

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59‐ established in 1968 (e.g., Le Pichon, 1968; Morgan, 1968; McKenzie, 1969).

60‐ The major argument to demonstrate the operation of plate tectonics was based

61‐ on the presence or absence of ophiolites remaining as a thin and narrow belt

62‐ within orogenic belts as an index of the tectonic movement of the oceanic plates

63‐ which have already disappeared by collision of continents (e.g. Komiya et al.,

64‐ 1999). However, definition of ophiolite depends on the rock assemblages

65‐ (Maruyama et al., 1989), and therefore when, where, and how plate tectonics

66‐ began to operate remains unsolved. To tackle these questions, we start from

67‐ clarifying what plate tectonics is from its most essential characters such as

68‐ rigidity, plate boundary processes, role ofMANUSCRIPT water as a driving force, mantle

69‐ potential temperature, and evaluate the multi-disciplinary aspects of the theory.

70‐ Finally, we propose a trigger to initiate plate tectonics on Hadean Earth.

71‐

72‐ 2. What is plate tectonics?

73‐ ACCEPTED 74‐ 2.1. Definition of plate tectonics and three-dimensional structure of

75‐ lithosphere

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76‐ Plate tectonics is basically defined as follows; The Earth’s surface is

77‐ covered by more than a dozen rigid lithospheres called plate. The movement of

78‐ these plates is rotational motion on the spherical body of the Earth. Hence both

79‐ the rotational pole and angular velocity of the rotation are given to all plates on

80‐ the globe. Thus, the motion at any point on the globe is determined, if both

81‐ direction of plate motion and speed are given on the globe. This is the core of the

82‐ theory of plate tectonics.

83‐ Another important factor of plate tectonics is the rigidity of the plate. The

84‐ Earth is characterized by rigid lithospheric plates, and the rigidity accompanies

85‐ brittle deformation. However, the deformation MANUSCRIPT mechanism of rocks changes with

86‐ increase in temperature from brittle to ductile, as seen in rock types from basalts,

87‐ gabbros and mantle peridotites which can be highly ductile above 800 °C (Arzi,

88‐ 1978; Kohlstedt et al.,1995). If volatiles such as H 2O and CO 2 are present, rocks

89‐ start melting at around this temperature. The presence of volatiles and melts are

90‐ imaged through velocity drop in geophysical studies (e.g. Nehlig, 1993). ACCEPTED 91‐ Furthermore, the ductility acts as a catalyzer to promote slippage at the bottom

92‐ of the lithosphere.

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93‐ One of the major features of plate tectonics is the three-dimensional

94‐ subduction of lithosphere in the shape of plate. In the upper mantle, the platy

95‐ structure of lithosphere is preserved during the subduction process. However,

96‐ the lithosphere cannot keep the platy form in the lower mantle. Platy or

97‐ curtain-like structure of lithosphere seen above 410 km changes to blob-shaped

98‐ structure in the lower mantle through the mantle transition zone at 410–660 km

99‐ depth with the phase changes from olivine to wadsleyite at 410 km, wadsleyite to

100‐ ringwoodite at 520 km, and finally into perovskite and wüstite at 660 km depth.

101‐ The recent observations, particularly derived from seismic tomographic data,

102‐ have revealed the architecture of subducting MANUSCRIPT plates at depth (Fukao, 1992;

103‐ Maruyama, 1994; Maruyama et al., 2007) including the total amount of

104‐ accumulated slabs.

105‐ Recent multidisciplinary research of the deep Earth including deep

106‐ mantle and even core have brought new insights into the dynamics of the Earth

107‐ combined with geologic history of the Earth, particularly back to 200 Ma, with ACCEPTED 108‐ information on the location of slab graveyards that have been well documented

109‐ in seismic tomographic images. A ca. 300 m topographic bulge over 3000 km

110‐ above the Pacific superplume has been identified where 5 independent hot

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111‐ spots are concentrated beneath the southern Pacific region (e.g. Zhao, 2007).

112‐ These observations have led to the concept of a coupled tectonic system where

113‐ upper mantle is dominated by horizontal plate movement with curtain-like

114‐ upwelling beneath the mid-oceanic ridge down to the 400 km depth (Zhao, 2004,

115‐ 2009; Zhao et al., 2007). Curtain-like upwelling makes the platy lithosphere at

116‐ mid-oceanic ridge which then moves to the trench and subducts to a depth of

117‐ 660 km. At the mantle transition zone from 410 to 660 km, the platy structure

118‐ becomes unclear with stagnation. From this depth to the bottom of the

119‐ core-mantle boundary (CMB), the plates do not show a simple curtain-like

120‐ structure. Instead, blob shaped structure MANUSCRIPT can be seen presumably in the

121‐ transition zone where olivine recrystallizes to wadsleyite (beta phase),

122‐ ringwoodite (gamma phase) and finally to perovskite plus wüstite. In the

123‐ presence of water, such recrystallization results in fine-grained crystal

124‐ aggregates and reduction in viscosity by 2 to 3 order of magnitude, causing the

125‐ shape change of lithosphere (Fig. 2). Tomographic images clearly indicate blob ACCEPTED 126‐ shaped independent down-going slabs that finally accumulate in the D” layer at

127‐ the bottom of the mantle. This is what we define as vertical tectonics, or drip

128‐ tectonics. On the other hand, rising mega-plume such as those documented

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129‐ underneath Africa and southern Pacific originated from older slab graveyards

130‐ formed during the amalgamation of Gondwana and Rodinia supercontinents,

131‐ respectively. Thus, the Permian superplume of Africa originated from the slab

132‐ graveyard of Gondwana, and the Pacific superplume from that of Neoproterozoic

133‐ Rodinia (Maruyama et al., 2007). Mantle upwelling is the characteristic feature in

134‐ the lower mantle, and therefore, the lower mantle is controlled by vertical

135‐ tectonics, mainly superplume and plume which is different from the horizontal

136‐ tectonics of the upper mantle. In general, the behavior of the upper mantle is

137‐ independent from the lower mantle. But over the long geological duration, the

138‐ scenario turns to be different, like the case MANUSCRIPT of the Cretaceous pulse (Larson,

139‐ 1991). Large volume of stagnant slabs at 660 km must have collapsed to make

140‐ slab avalanche to the bottom of CMB, and generated extensive magmatism only

141‐ in the Pacific domain. It did not affect the Indian and Atlantic domains, as have

142‐ been well documented from the width of magnetic stripe. About double to four

143‐ times more production of MORB in the Pacific domain as well as OIB volcanism ACCEPTED 144‐ was caused by faster subduction along the Pacific subduction zones to create

145‐ voluminous TTG, basalt and felsic volcanics (Maruyama, 1994). Episodic

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146‐ collapse of cold slabs onto the top of the CMB may drive more extensive

147‐ geomagnetism through more activated convection in the liquid outer core.

148‐

149‐ 2.2. Plate boundary process

150‐ There are three types of plate boundary process: (1) divergent (Fig. 3A,B),

151‐ (2) convergent (Fig. 3C,D), and (3) transform (Fig. 3 map view). The divergent

152‐ plate boundary is represented by mid-oceanic ridge where oceanic plates are

153‐ formed as schematically shown in Fig. 3A. Another type of divergent boundary is

154‐ the continental rift where initial doming of continents occurs by mantle upwelling

155‐ located beneath the continent, followed byMANUSCRIPT subsidence to form continental rift

156‐ valley (Fig. 3B). In this process, low pressure UHT and HT metamorphism could

157‐ be expected. The convergent plate boundaries are of two types: the first one is

158‐ subduction zone where descending slab is dehydrated to generate calc-alkaline

159‐ magma that increase the volume of continental crust (Fig. 3C), accompanied by

160‐ the formation of accretionary complex and subduction zone regional ACCEPTED 161‐ metamorphism to form blueschist and eclogite along Benioff thrust. The second

162‐ one is the collisional plate boundary where mountain building occurs such as the

163‐ Himalaya and Alps to exhume HP-UHP metamorphic belts and associated

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164‐ sedimentation to form huge deltaic sediments on the neighboring ocean floor

165‐ (Fig. 3D).

166‐ Plate tectonics has significant effects in not only planetary interior but also

167‐ the surface and atmosphere. A key role of plate tectonics is to stabilize the

168‐ surface environment of the Earth through the steady-state lithospheric

169‐ circulation between the surface of the Earth and deep Earth from mantle

170‐ transition zone (410–660 km) down to the CMB (2900 km depth). At the same

171‐ time, mantle upwellings transport volatiles from mantle to atmosphere and ocean

172‐ to balance the material circulation between the surface and deep mantle.

173‐ Assuming the on-going production rate of MORBMANUSCRIPT crust as 25 km 3/yr since 2.0 Ga,

174‐ the production rate might have been double prior to 2.0 Ga, suggesting that the

175‐ whole mantle must have melted at least once. This contributes to the long-term

176‐ stability of surface environment of the Earth through the steady-state energy

177‐ circulation and avoid stocking all slabs in particular domains in the solid Earth

178‐ (e.g., Maruyama et al., 2007). ACCEPTED 179‐

180‐ 3. What are the requirements for plate tectonics?

181‐ 3.1. The importance of water on plate tectonics

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182‐ Plate tectonics is fundamentally controlled by fluids acting as lubricant,

183‐ particularly H 2O (see details in Section 3.2). If CO 2 is present as the dominant

184‐ constituent, it would impart a negative effect like the case of Venus (McGovern

185‐ and Schubert, 1989; Korenaga, 2010). Whereas the convergent plate margins

186‐ on the Earth are characterized by production of voluminous subduction zone

187‐ magmas, there is no equivalent calc-alkaline (CA) magmatism on Venus,

188‐ although Venus is said to be similar to the Earth in terms of trench-like

189‐ topographic features and the large scale of landscapes caused by rising and

190‐ downwelling plumes. This distinction between Venus and Earth might be related

191‐ MANUSCRIPT to the dominance of CO 2 in Venus against H 2O on Earth. This example

192‐ underpins the important role played by liquid water in plate tectonics. In other

193‐ words, plate tectonics is not operated on a planet if liquid water does not cover at

194‐ least the surface of the planet. We further evaluate the role of liquid water and

195‐ mechanism to operate plate tectonics in the next section.

196‐ ACCEPTED 197‐ 3.2. Mechanism of plate tectonics and water circulation

198‐ The top of lithosphere is hydrated at the mid-oceanic ridge through

199‐ water-rock interaction by circulating water. As a result, a number of hydrous

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200‐ silicates are formed on the upper layer of oceanic basalts usually on the surface,

201‐ and sometimes reaching to 1.5–2 km depth (Alt et al., 1986). This is the most

202‐ critical process to operate plate tectonics.

203‐ Subsequently, the separation of saline water at mid-oceanic ridge produce

204‐ two phases, one is nearly fresh water and the other is dense saline brine, which

205‐ penetrate into the gabbroic layers of the oceanic crust, where brown hornblende

206‐ is stable as demonstrated by dredge samples from the Indian ocean (Maruyama

207‐ et al., 1989). The hydrated topmost part of lithosphere moves horizontally to

208‐ subduction zones where it descents into the deep mantle accompanied by

209‐ progressive dehydration along the subduction MANUSCRIPT zone geotherm (Fig. 4). Most of

210‐ the hydrous minerals break down into anhydrous phases above 50 km depth,

211‐ below which dry eclogitic assemblages are stabilized (Maruyama et al., 1996).

212‐ The change in water contents from blueschist to eclogite transition ranges from 2

213‐ wt.% to less than 0.5 wt.% (Okamoto and Maruyama, 2004). From the stability

214‐ field of amphibole lawsonite, the rocks move down to epidote, zoisite, and ACCEPTED 215‐ eclogite with minor amphibole and finally to dry eclogite with garnet, omphacite,

216‐ and quartz (Okamoto and Maruyama, 1999, 2004). At further depth, coesite

217‐ appears and is finally replaced by stishovite at 230 km depth (Komabayashi et

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218‐ al., 2007). Omphacite gradually starts to break down to garnetite and other minor

219‐ accessory ultrahigh-pressure mineral phases at the depth above ca. 70 km. The

220‐ trench turbidite and underlying deep sea sediments become dried out between

221‐ 50 to 100 km depth in the subduction channel, with the surviving K feldspar

222‐ turning to hollandite at 200 km deep (Irifune et al., 1994).

223‐ Dehydrated fluid is removed to the upper seismic zones. Fluids released

224‐ during progressive dehydration plays a critical role as lubricant and imparts a

225‐ slippery top surface of the down-going plate. Thus, both top and bottom

226‐ boundaries of the plate act as slippage planes in subduction zones (Fig. 4).

227‐ The lower zone of the double seismic MANUSCRIPT plane starts from right inside the

228‐ trench axis and both the lower and upper zones are located not within the

229‐ oceanic crust, but in the peridotite slab (Hasegawa et al., 2005, 2009, 2013).

230‐ The double seismic zone converges at around 200 km depth, and finally

231‐ disappears (Fig. 4).

232‐ From approximately 200 to 660 km depth, the occurrence of minor ACCEPTED 233‐ earthquakes suggests continuous dehydration to transport fluids into the mantle

234‐ transition zone (410–660 km depth) as a huge water tank as large as 5 times

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235‐ that of the of ocean water in volume (Murakami et al., 2002; Maruyama and Liou,

236‐ 2005).

237‐ The largest and richest hydrated mantle transition zone occurs in the

238‐ Western Pacific and East Asia, and hydrous mantle plumes generated at 410 km

239‐ depth cause active surface dynamics in this region (Komiya and Maruyama,

240‐ 2007).

241‐

242‐ 3.3. Conditions to operate plate tectonics

243‐ What is the requirement to initiate plate tectonics with subduction of plate?

244‐ Although this question is still controversial, MANUSCRIPT this can be evaluated in conjunction

245‐ with the history of evolution of the Earth.

246‐ The mechanism of plate tectonics is dominant in the upper mantle of

247‐ present day Earth. In contrast, Mars and Venus are dominated by the

248‐ stagnant-lid convection at present where the mantle convection is caused by

249‐ upwelling and downwelling plumes beneath a rigid and immobile lid or plate (Fig. ACCEPTED 250‐ 1) (Moresi and Solomatov, 1998; Reese et al., 1998). The difference in the

251‐ dominant style of tectonics significantly influences the evolution of terrestrial

252‐ planets. Plate tectonics can efficiently cool the planetary interior and carry

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253‐ crustal materials containing water and heat-producing elements, such as

254‐ uranium (U), thorium (Th), and potassium (K), into deep mantle. Subducted

255‐ crustal materials may become the heat source of the plume in planetary interior.

256‐ The numerical calculations in previous studies have identified the necessary

257‐ conditions for initiation of plate tectonics which include the following: (i)

258‐ moderate strength of plate to enable the plate to keep its form without hindrance

259‐ to the development of plate boundaries; (ii) the low frictional coefficient between

260‐ plate boundaries to allow the independent movement of each plate including

261‐ plate subduction; and (iii) the driving forces, i.e. slab pull, ridge push, and mantle

262‐ convection, that keep the constant movement MANUSCRIPT and subduction of plate.

263‐

264‐ 3.3.1 ... Plate strength as a function of water

265‐ In this section, we focus on the plate strength of the Earth in the past and

266‐ discuss the reasons why plate tectonics was initiated on Earth.

267‐ Laboratory studies have indicated that the rock strength (or plate strength) ACCEPTED 268‐ depends on the temperature and water content (e.g., Karato and Wu, 1993). The

269‐ existence of water may be a key to allow the operation of plate tectonics on the

270‐ terrestrial planets as is evident when compared to the case of Mars and Venus

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271‐ that have no ocean. Therefore, the formation of the ocean must have been an

272‐ important factor for the initiation and operation of plate tectonics. In brittle

273‐ deformation regions, water plays a role as pore pressure, which has physical

274‐ and chemical effects on the rock strength. As a physical effect, the pore

275‐ pressure Pp reduces the effective pressure Pe. As a result, the reduction of

276‐ frictional strength occurs (Eq. 1).

277‐ τ = τ + f P = τ + f (P −αP ) 0 c e 0 c c p

278‐ (1)

279‐ where fc is frictional coefficient, τ and α are the constant. The frictional

280‐ τ MANUSCRIPT strength decreases with increasing pore pressure Pp (Fig. 5). On the other

281‐ hand, it has been reported for sheet-structure minerals such as clay minerals

282‐ that the frictional coefficient itself decreases under water-saturated conditions

283‐ without pore pressure (e.g., Morrow et al., 2000). For instance, the frictional

284‐ coefficient of smectite is mostly no different from that of Byerlee’s law (0.6–0.85)

285‐ under dry conditions, whereas the frictional coefficient is significantly low ACCEPTED 286‐ (0.2–0.3) under water-saturated conditions (e.g., Kubo and Katayama, 2015).

287‐ Therefore, water reduces the plate strength and the frictional strength of plate

288‐ boundaries, and helps the movement of plate to develop plate boundaries.

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289‐ Water has significant effect on rock strength even in ductile deformation

290‐ region. Water (hydrogen) increases the concentration of intracrystalline point

291‐ defects and the rock strength (viscosity) decreases (e.g., Karato and Wu, 1993;

292‐ Hirth and Kohlstedt, 2003). In fact, viscosity difference between mantle

293‐ lithosphere (dry) and asthenosphere (wet) is large, which is a key to make thin

294‐ plates, and the low viscosity of the asthenosphere can play a role as lubricant to

295‐ plate motion. From the above results, it is clear that the initiation of plate

296‐ tectonics requires water (fluid), which would suggest the presence of ocean on

297‐ Hadean Earth. Below we evaluate the rheological structure of Hadean Earth and

298‐ discuss the possibility of initiation of plate MANUSCRIPT tectonics in Hadean due to the

299‐ formation of ocean.

300‐ To determine the rheological structure of Hadean Earth, the thermal

301‐ structure of Earth’s interior is the key. Potential temperature in Hadean Earth is

302‐ not well known, but Archean potential temperature was at least 150–200 °C

303‐ higher (i.e.1500–1550 °C) than that in current Eart h (1350 °C) (e.g., Komiya, ACCEPTED 304‐ 2004). We calculated the thermal structure of Hadean Earth based on a model of

305‐ transient half-space cooling (Turcotte and Schubert, 2002) at given mantle and

306‐ surface temperature parameters at 1600 °C as the li quidus temperature of

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307‐ mantle peridotite and 100 °C, respectively (Fig. 6A ), and the crustal thickness is

308‐ assumed to be 30 km for early Hadean Earth. In the calculation of the

309‐ rheological structures, the rock strength in brittle regions was computed not only

310‐ from Byerlee’s law (Byerlee, 1978), but also frictional coefficient of sheet silicate

311‐ minerals under saturated conditions. It is inferred that the plate strength notably

312‐ depends on whether the water covers the plate boundaries (ridges, subduction

313‐ zones, and transform faults) because the frictional strength itself of sheet silicate

314‐ minerals decreases under water-saturated conditions (Fig. 5). In ductile

315‐ deformation region, the strength of oceanic crust is calculated from flow laws of

316‐ plagioclase (Rybacki and Dreasen, 2000; MANUSCRIPTAzuma et al., 2014). Mantle rheology

317‐ is determined by flow laws of olivine (Karato and Jung, 2003; Katayama and

318‐ Karato, 2008). In both brittle region and ductile region, the effect of water is

319‐ taken into account. Fig. 6B–D shows the calculated rheological structures at

320‐ plate age of 10–40 Myr in Hadean Earth. Plate strength is different between wet

321‐ and dry conditions because of the effect of water to friction coefficient of sheet ACCEPTED 322‐ silicate mineral. We infer the change of plate strength in Hadean based on the

323‐ Fig. 6. If the early Earth was a naked planet without ocean (Maruyama et al.,

324‐ 2013), the plate strength of the Earth was quite high to operate the stagnant lid

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325‐ tectonics (Fig. 7). However, the formation of ocean made the strength of plate

326‐ (<200–300 MPa) and plate boundaries (frictional coefficient < 0.1–0.2) weak (Fig.

327‐ 7). The decrease of plate strength promoted the development of plate

328‐ boundaries and the independent motion of plate, indicating that the Earth would

329‐ have potential for the initiation of plate tectonics in the Hadean. This also means

330‐ that water is necessary for the initiation of plate tectonics, and the formation age

331‐ of ocean is a key to discuss when plate tectonics began on the Earth.

332‐

333‐ 3.3.2. Driving force of plate tectonics: Generation of slab-pull force MANUSCRIPT 334‐ The dominance of free fluids immediately above the down-going slabs in

335‐ subduction zones becomes the major driving force for the slab pull of plates. On

336‐ the other hand, ridge push serves to push up the spreading axis by about 2.5 km

337‐ from the base of surrounding ocean floor, where the curtain-like steady state

338‐ mantle upwelling is seen in modern mid-Atlantic ridge (Zhao, 2004). This 339‐ generates aACCEPTED sliding slope extending for about 15,000 km in the Atlantic Ocean 340‐ from spreading axis to the 200 Ma ocean-floor at continental margin. Along the

341‐ slope, oceanic lithosphere together with continents slides at the rate of 1–2

342‐ cm/yr. Compared to the Atlantic Ocean, the Pacific Ocean is marked by active 19‐ ‐ P a g e ‐|‐20202020‐‐‐‐ ACCEPTED MANUSCRIPT ‐

343‐ subduction zones at continental margin, without continents in the oceanic

344‐ domain, and sliding rate is 5 times faster than that of Atlantic region. A

345‐ combination of effective ridge push and slab pull forces associated with

346‐ subduction in convergent margins creates five times faster spreading rate

347‐ (Forsyth and Uyeda, 1975).

348‐ 4. When plate tectonics began on Earth?

349‐

350‐ 4.1. Previous studies based on geological evidence

351‐ When did plate tectonics begin on the Earth? Although extensively MANUSCRIPT 352‐ discussed based on various geological evidence, the timing of onset of plate

353‐ tectonics remains controversial. The geological evidence commonly used as

354‐ an indicator of plate tectonics is the presence of ophiolite (Dewey and Bird,

355‐ 1971), blueschists, characteristics of accretionary complex, duplex structure

356‐ (Komiya et al., 1999), ultra-high pressure (UHP) metamorphism including the 357‐ occurrence ACCEPTED of coesite and diamond, geochemical data from zircons, among 358‐ other features (e.g., Wilde et al., 2001; Harrison et al., 2005; Stern, 2005; Furnes

359‐ et al., 2007; Hopkins et al., 2008; Hamilton, 2011; Komiya et al., 2015). These

360‐ lines of evidence were derived mainly from the Precambrian Earth. However, it 20‐ ‐ P a g e ‐|‐21212121‐‐‐‐ ACCEPTED MANUSCRIPT ‐

361‐ can be said that UHP metamorphism may not be strong evidence for plate

362‐ tectonics because UHP metamorphism is typical feature seen after 600 Ma

363‐ through the Earth’s history as well as blueschist since ca. 800 Ma. The style of

364‐ plate tectonics has been changing through time and its feature was possibly

365‐ different between the early and present day Earth (Komiya et al., 1999;

366‐ Maruyama et al., 2007). These features also suggest that slab melting must

367‐ have occurred when the potential temperature of early Earth was higher than

368‐ that of current Earth. Therefore, most of evidence focusing on the timing of

369‐ initiation of plate tectonics is derived from Hadean zircons. Mineral inclusions

370‐ and oxygen isotopes in these Hadean zircons MANUSCRIPT suggest the derivation from TTG

371‐ magma, indicating that plate tectonics began at 4.4 Ga (e.g., Wilde et al., 2001).

372‐

373‐ 4.2. The trigger of plate tectonics: ABEL Bombardment

374‐ The initiation of plate tectonics requires the presence of ocean (see

375‐ Section 3). However, the Earth must have been formed as a dry planet through ACCEPTED 376‐ the extensive accretion of planetesimals within a few millions of years after CAI

377‐ formation at 4.567 Ga (Amelin et al., 2002, 2010). At the end of this period, the

378‐ Earth must have witnessed extensive melting termed the magma ocean under

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379‐ the dry condition, because the source meteorites were dry enstatite

380‐ chondrite-like materials (Maruyama et al., 2013; Maruyama and Ebisuzaki,

381‐ 2016). If so, how did the Earth obtain the volatiles after magma ocean and its

382‐ solidification to bear ocean? The most possible scenario is the delivery of

383‐ volatiles to Earth to generate ocean through bombardment as proposed by

384‐ Maruyama and Ebisuzaki (2016) who coined the term “ABEL” (advent of

385‐ bio-elements) model. According to this proposal, the completely dry Earth was

386‐ formed at 4.56 Ga and volatiles and highly siderophile elements were delivered

387‐ by carbonaceous chondrites dominantly during 4.37–4.20 Ga from outer

388‐ asteroid belts due to gravitational scattering MANUSCRIPT by gas giants such as Jupiter,

389‐ Saturn, and the missing “Black Sheep”. This delivery event is termed ABEL

390‐ Bombardment which enabled the initially reductive Earth to have ocean and

391‐ atmosphere. Through this bombardment, the Earth’s crust is estimated to have

392‐ accreted by ca. 3 km (Morgan et al, 2001; Becker et al., 2006), or 17 km (Walker,

393‐ 2009) as originally derived from the abundance of PGEs in the mantle ACCEPTED 394‐ (Maruyama and Ebisuzaki, 2016).

395‐ Bombardment induced instantaneous shock metamorphism, melting,

396‐ and gas explosion. The crashed material was deposited as dust and glass on

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397‐ the surface, whereas the volatiles generated the atmosphere and ocean. The

398‐ basement rocks were fragmented, brecciated to soil or partly related to be glassy

399‐ tektite and micro-tektite, together with falling nano-sized particles of glassy CI

400‐ chondrites. After adequate volume of oceanic and atmospheric components

401‐ were delivered, ca. 4 km thick ocean and atmosphere of over 10 bars were

402‐ generated, and hydrological material circulation began through weathering,

403‐ erosion and transportation to transport onland-materials into lakes or oceans. By

404‐ analogy with the thick regolith layers on the Moon reaching up to 10 km

405‐ thickness depending on the localities, composed of a mixture of basement rocks

406‐ and powders of CI chondrites, the early Earth MANUSCRIPT might have also been presumably

407‐ covered by a few km thick regolith layers.

408‐

409‐ 4.3. Mechanism to initiate the plate tectonics on the Hadean Earth

410‐ Due to repeated bombardment by carbonaceous chondrites from outer

411‐ asteroid belts, the primordial continents were destroyed and brecciated to mix ACCEPTED 412‐ with sub-micron sized dust originated from asteroids and primordial continents,

413‐ such as glassy tektites, orange or green soils, and breccias. Total thickness of

414‐ sediment generated by crashed materials may have accumulated over a few km

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415‐ to cover the primordial continents (Maruyama and Ebisuzaki, 2016). At the same

416‐ time, the formation of atmosphere and hydrosphere gradually progressed due to

417‐ the accumulation of water components, CO 2, and N 2 through ABEL

418‐ Bombardments (Fig. 8).

419‐ Primordial continents together with sediment cover and dikes-sills of

420‐ mafic-ultramafic rocks in the upper continental crust of anorthosite with

421‐ schreibersite (Fe 3P), uranites, and other metallic elements, such as Mo, Zn, Mn,

422‐ Mg, Fe 2+ , Cr 3+ , were all concentrated in the final residues of magma ocean. Thus,

423‐ KREEP gabbros were largely settled in the lower crust but locally intruded into

424‐ the upper crust or erupted on the surface MANUSCRIPTof the primordial continents together

425‐ with komatiitic lava-flows at earlier stages. The nutrients supplied by these might

426‐ have played significant role to cause enzyme-forming pre-biotic reactions for the

427‐ emergence of life. Fluids, as the most important catalytic agent to promote

428‐ recrystallization reaction, infiltrated from entire basement crust (primordial crust)

429‐ into mantle depths by the large asteroid bombardments. Through the formation ACCEPTED 430‐ of thickened crust (ca. 10–40 km in maximum) by addition of CI chondrite falls

431‐ enriched in volatiles, along the weakened lineaments (connected through

432‐ accidental arrangement of bombarded craters), led to the development of the

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433‐ first subsidence of linear depression and to evolve the first trench line. This

434‐ marked the formation of the first consuming plate boundary (Fig. 9).

435‐ Associated with development of trench line along the continental margin,

436‐ mantle upwelling by plumes made topographic highs to push up primordial

437‐ continents. If several (at least three) plumes are connected, a linear fracture can

438‐ be formed due to the development of the linear mantle upwelling combining two

439‐ hotspots, which is analogous to spreading axis like Mid-Atlantic Ridge (Fig. 9).

440‐ Continuous spreading and accompanying horizontal compression leads to

441‐ further subduction analogous to the modern-style plate tectonics, although under

442‐ the double-layered mantle convection regime, MANUSCRIPT because of high-T mantle ca.

443‐ 1500 °C (Fig. 9).

444‐ In contrast to the Moon, the Earth has kept primordial atmosphere and

445‐ ocean. These volatiles could have contributed to recrystallization, which was the

446‐ key to initiate plate tectonics. Recrystallization of anorthosite, iron rich basalt and

447‐ mantle peridotite were garnet-bearing phases in spite of high geothermal ACCEPTED 448‐ gradient, since garnet is highly dense, and thus the lower half would turn to

449‐ eclogite due to high-pressure (Fig. 10). Along the heterogeneous plate boundary

450‐ on the Hadean Earth, a number of nearly vertical faults transformed to oblique

25‐ ‐ P a g e ‐|‐26262626‐‐‐‐ ACCEPTED MANUSCRIPT ‐

451‐ because of mantle upwelling which pushed up from below. If recrystallization is

452‐ rapid enough to promote phase transformation into high density crust under the

453‐ presence of H 2O fluid, subduction starts along the now reclined faults, combined

454‐ with plume-related mantle upwelling. The analogy of such features is modern

455‐ Africa, where the plume heads are connected (Burke, 1988), followed by the

456‐ initiation of vertical mantle upwelling corresponding to the process at the

457‐ divergent plate boundary. The surface portion of the rigid plate starts to subduct

458‐ along linear boundary on the faults within primordial continents, including the

459‐ newly grown portions. At the divergent plate boundary, new oceanic crust could

460‐ be formed without any primordial continents, MANUSCRIPT marking the appearance of oceanic

461‐ lithosphere. In the case of Hadean Earth, double thick lithosphere (Fig. 9) having

462‐ high content of garnet may have promoted the subduction of heavy primordial

463‐ continental crust into deep mantle, which is the cause of slab pull force. Once it

464‐ reached to 300 km depth, the SiO 2 component in eclogitized KREEP rocks

465‐ would enhance the slab pull force because of phase transformation from coesite ACCEPTED 466‐ (density 2.6 g/cm 3) to stishovite (density 4.4 g/cm 3) with respect to mantle

467‐ peridotite (density 3.5 g/cm 3). We consider this as the scenario for initiation of

468‐ plate tectonics.

26‐ ‐ P a g e ‐|‐27272727‐‐‐‐ ACCEPTED MANUSCRIPT ‐

469‐

470‐ 4.4. Eclogitization triggered by ABEL Bombardment

471‐ Fig. 10 shows the phase diagram of MORB + H 2O system (after

472‐ Maruyama et al., 1996; Okamoto and Maruyama, 2004). The figure shows the

473‐ Hadean and Phanerozoic subduction zone geotherms along the Benioff plane

474‐ from 0 to 50 kbar pressure and temperature up to 1500 °C. Along the

475‐ Phanerozoic geotherm, blueschist and low-temperature eclogite appear which is

476‐ consistent with the geological observation. In contrast, blueschist does not

477‐ appear during Precambrian including Hadean, whereas eclogite facies is stable

478‐ in a wide range from low-temperature to overMANUSCRIPT 1500 °C under high-temperature

479‐ and high-pressure conditions. Eclogite contains lawsonite at low-temperature,

480‐ but amphibole and zoisite is stable between low-temperature and

481‐ high-temperature, and dry eclogite is stable over ca. 1050 °C. Dry eclogite can

482‐ be observed in kimberlite from Cretaceous continental rift in Africa or in the

483‐ Pacific domain such as Malaita Island in Solomon Islands (Ishikawa et al., 2007). ACCEPTED 484‐ Mantle xenoliths carried to the surface by alnöitic magma commonly contain dry

485‐ eclogite originated from basalt. These basalts were originally ocean island basalt

486‐ (OIB) or MORB of 600 Ma, and even dates back 3.0 Ga. Such ancient history

27‐ ‐ P a g e ‐|‐28282828‐‐‐‐ ACCEPTED MANUSCRIPT ‐

487‐ indicates that dry eclogite was stable in the deep parts of subduction zone in

488‐ Archean, which is consistent with the phase diagram shown in Fig. 10.

489‐ Hadean geotherm immediately after the solidification of magma ocean

490‐ must be lower than dry solidus of MORB. In the domain between dry solidus and

491‐ wet solidus, which is solid-melt region in Fig. 10, both magma and crystalized

492‐ minerals are present. In Hadean, the temperature of mantle was high enough,

493‐ therefore solid-melt region should have been smaller, and wet solidus was

494‐ closer to the dry solidus.

495‐ The most important factor to be mentioned here is the density of eclogite

496‐ as ca. 3.5–4.0 g/cm 3 depending on pressure MANUSCRIPT and Fe/Mg ratio, which is markedly

497‐ denser than that of surrounding mantle peridotite with a density of ca. 3.5 g/cm 3

498‐ up to 50 kbar. The difference in the density produces strong slab pull force. In

499‐ the case of modern subduction zone, oceanic plate aging less than 200 Ma

500‐ comprises only 6 km MORB crust within the 60 km thick lithosphere.

501‐ Eclogitization of MORB crust is considered to account for 80% of driving force of ACCEPTED 502‐ plate tectonics. Given the rock assemblage consisting of lithosphere at the

503‐ initiation of plate tectonics, KREEP lower crust is thought to be extremely thick

504‐ (over 100 km), compared with the 6 km thickness in modern Earth or 20 km in

28‐ ‐ P a g e ‐|‐29292929‐‐‐‐ ACCEPTED MANUSCRIPT ‐

505‐ early Archean. Moreover, KREEP basalt is enriched in iron, therefore chemical

506‐ composition is expected to contribute to the higher density. The combinations of

507‐ bigger sized crustal body and high density in Hadean are the critical factors to

508‐ initiate the operation of plate tectonics.

509‐ However, eclogite is ultrahigh pressure metamorphic rock. Thus,

510‐ eclogitization needs ultrahigh pressure. The initiation of eclogitization was

511‐ achieved through ABEL Bombardment, which delivered volatiles onto dry Earth

512‐ for the first time. As explained in earlier section, the formation of ocean is one of

513‐ the most important conditions to initiate plate tectonics. Specifically, the

514‐ presence of volatiles enabled ultrahigh pressureMANUSCRIPT (UHP) metamorphism (e.g.

515‐ eclogitization) by the accretion of water component in KREEP crust or part of

516‐ mantle. As a result of ABEL Bombardment, accreted volatiles could dramatically

517‐ accelerate recrystallization in KREEP crust to generate equilibrated eclogite. If

518‐ volatiles were absent, recrystallization could not proceed even if KREEP crust is

519‐ carried into deep mantle by convection. Such examples are well observed in ACCEPTED 520‐ UHP metamorphic rocks in Kokchetav, Kazakhstan. Internal structure of a few

521‐ mm sized zircon from Kokchetav Massif shows a distinct zonation texture such

522‐ as the core, mantle, and outer rim. The core part and outer rim of zircon contains

29‐ ‐ P a g e ‐|‐30303030‐‐‐‐ ACCEPTED MANUSCRIPT ‐

523‐ low-pressure and high temperature mineral inclusions, such as albite, quartz,

524‐ and graphite, whereas the mantle domain contains jadeite, coesite, and diamond

525‐ which is characteristic of UHP and high temperature metamorphism (Katayama

526‐ and Maruyama, 2009). This zoning structure indicates that inclusions contained

527‐ in each domain grew under specific P-T conditions; core and outer rim

528‐ experienced low-pressure metamorphism, and mantle part was under ultrahigh

529‐ pressure and temperature metamorphism. After the core part was grown under

530‐ low-pressure metamorphism, this part should have experienced UHP

531‐ metamorphism when the mantle part was growing. However, inclusions in the

532‐ core did not change, remaining low-pressure MANUSCRIPT phases. Likewise, UHP minerals in

533‐ mantle part was not relocated to lower P-T conditions such as 5–6 kbar and

534‐ 600 °C when outer rim was growing, and inclusions w ere remained without

535‐ phase change. This means that hydration with lowering of temperature and

536‐ pressure was not in progress but inclusions trapped in zircon did not experience

537‐ phase transition, which was due to absence of fluid within zircon crystal. Thus, ACCEPTED 538‐ phase transition does not occur if fluid is absent, even if crystals were put under

539‐ ultrahigh P-T conditions during 30 Myr (Komiya and Maruyama, 2007).

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540‐ Therefore, it is evident that eclogitization could not have occurred prior to ABEL

541‐ Bombardment, as the Earth did not have water component.

542‐ As described above, strong slab pull force was generated by phase

543‐ transition, e.g. eclogitization. No eclogitization would prevent subduction due to

544‐ buoyancy. Therefore, the presence of volatile is the most critical factor for the

545‐ phase transition as eclogitization, and the trigger of plate tectonics. Volatiles

546‐ were delivered to the Earth by ABEL Bombardment, and we therefore consider

547‐ this as an exceedingly important event in the Earth history to evolve into

548‐ habitable planet.

549‐ MANUSCRIPT

550‐ 4.5. The size of impactors to initiate plate tectonics

551‐ Through the ABEL Bombardment, volatiles were circulated within the

552‐ interior of the Earth down to mantle depth, facilitating continuous eclogitization. It

553‐ is clear that this process initiated the operation of plate tectonics following to the

554‐ appearance of ocean on Earth’s surface. However, there is another important ACCEPTED 555‐ factor to initiate plate tectonics. It is the size of a crater formed by the

556‐ bombardment.

31‐ ‐ P a g e ‐|‐32323232‐‐‐‐ ACCEPTED MANUSCRIPT ‐

557‐ After the Earth’s layered structure was made through the consolidation of

558‐ the magma ocean since 4.53 Ga, the early Hadean Earth formed a global rigid

559‐ continental lithosphere as thick as 100–150 km. It means there was no

560‐ horizontal/vertical movement like modern plate tectonics, which should have had

561‐ stagnant lid tectonics (Solomatov and Zharkov, 1990; Moresi and Solomatov,

562‐ 1995; Solomatov, 1995; Solomatov and Moresi, 1996). Therefore, it is necessary

563‐ to switch from stagnant lid tectonics to plate tectonics, and such process should

564‐ have followed by the breakup of rigid plate. The ABEL Bombardment was a

565‐ critical event to destroy rigid plate formed on the Earth. Moreover, such

566‐ destruction by impactors must have been MANUSCRIPTextreme, which is not like 500 km or

567‐ 1000 km wide, rather Pacific Ocean sized huge crater must have formed by

568‐ single bombardment or intensive bombardments within short period. If 1000 km

569‐ across impactor bombarded the Earth, impactor itself and the surface of the

570‐ Earth, or up to a certain depth of lithosphere, instantaneously have vaporized.

571‐ As a result, 10,000 km across crater formed where mantle rebound occurred to ACCEPTED 572‐ balance the deficit caused by the bombardment, which resulted in the formation

573‐ of first bi-modal lithosphere on the Earth. Consequently, slab pull force, as the

574‐ major and powerful driving force of plate tectonics, was generated at the

32‐ ‐ P a g e ‐|‐33333333‐‐‐‐ ACCEPTED MANUSCRIPT ‐

575‐ subduction zone due to eclogitization. Also following to mantle rebound after the

576‐ bombardment, if some plume heads appeared, curtain-like upwelling was

577‐ generated by the connection of two plumes to create mid-oceanic ridge, where

578‐ decompression melting through mantle upwelling provided basalt in divergent

579‐ region to cause the ridge push force. This is the process to initiate modern plate

580‐ tectonics after stagnant lid tectonics.

581‐ Regarding Hadean surface state after bombardments, Marchi et al. (2014)

582‐ suggested how the surface was disrupted during the first 100 Myr after the

583‐ formation of the Earth, assuming several conditions such as early Earth’s

584‐ impactor size-frequency (Fig. 11A), lunar impactMANUSCRIPT flux, and impact-generated melt

585‐ volume. Fig. 11B shows that the spatial distribution and sizes of craters formed

586‐ on the early Earth at four different times given from their model, indicating that

587‐ the first 25 Myr after the formation of the Earth, almost all Earth’s surface is

588‐ affected by bombardments and reworked by impact-generated melt, while there

589‐ are areas that were not influenced by impact-generated melt at each time steps ACCEPTED 590‐ since 4.450 Ga. However, it can be interpreted that almost all Earth’s surface

591‐ was reproduced between 4.4500 Ga and 4.400 Ga. They estimated that up to

592‐ 60–70% of the Earth’s surface was reproduced to 20 km depth approximately

33‐ ‐ P a g e ‐|‐34343434‐‐‐‐ ACCEPTED MANUSCRIPT ‐

593‐ before 4.4 Ga. As seen in a series of map in Fig 11B, vast area is reproduced

594‐ after bombardments, suggesting Hadean rigid continental lithosphere must have

595‐ severely broken in early stage, and Pacific Ocean sized proto-primordial

596‐ continental lithosphere as thick as over 100 km was replaced by oceanic

597‐ lithosphere and mafic peridotite less than 50 km (Maruyama and Ebisuzaki,

598‐ 2016).

599‐ Marchi et al. (2014) also suggested that the Hadean was presumably

600‐ characterized by one to four impactors larger than 1000 km, and by three to

601‐ seven impactors larger than 500 km. Considering the size of impactors, it is

602‐ natural to allow that the larger impactors toMANUSCRIPT hit the Earth than the Moon as the

603‐ Earth’s mass is 50 times larger than the Moon. Such a specific bombardment

604‐ image delivered by their scenario is well fit to the ABEL model (Maruyama and

605‐ Ebisuzaki, 2016), and the suggested process to initiate the plate tectonics

606‐ following to the generation of Pacific Ocean class crater.

607‐ On the other hand, some assumptions in Marchi et al. (2014) can be ACCEPTED 608‐ modified based on recent detailed studies for lunar samples (e.g. Borg et al.,

609‐ 2015; Hopkins and Mojzsis, 2015). First, concerning the terrestrial impact rate,

610‐ they basically assumed the so-called lunar sawtooth model to extrapolate to the

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611‐ Earth. However, the peak age of the bombardment has been reviewed through

612‐ the recent research for lunar zircon to back to 4.37–4.20 Ga (Maruyama and

613‐ Ebisuzaki, 2016), which can be taking into consideration for the method of

614‐ further simulation. Second, the scenario of terrestrial bombardment including

615‐ planetary formation should be enhanced to distinct the nature of the

616‐ bombardment. For example, sawtooth model provides two peaks of the

617‐ bombardment; e.g., 4.56 Ga and 3.9 Ga. In view of planetary formation theory,

618‐ the bombardment around 4.56 Ga means the formation of each planet such as

619‐ primitive Earth or Mars. This is totally different event from the bombardment

620‐ which occurred as so-called late heavy MANUSCRIPT bombardment or the ABEL

621‐ Bombardment. “The bombardment” to form a planet and the bombardment

622‐ occurred on formed planet must be distinguished.

623‐

624‐ 4.6 ... An implication to the Hadean plate tectonic history

625‐ Figure 12 is schematic figure to show the history of Hadean plate ACCEPTED 626‐ tectonics from 4.55 to 4.0 Ga. At 4.55 Ga, magma ocean entirely covered the

627‐ Earth, and solid iron core was present. By 4.53 Ga, mantle was solidified to form

628‐ layered structure remaining residual magma (lherzolite) on the top and bottom of

35‐ ‐ P a g e ‐|‐36363636‐‐‐‐ ACCEPTED MANUSCRIPT ‐

629‐ the lower mantle. A few hundred km thick topmost upper part is composed of

630‐ anorthositic upper crust underplated by primarily generated KREEP basaltic

631‐ lower crust (hereafter, KREEP I). The surface of the continental lithosphere must

632‐ be covered by komatiitic lava flow together with KREEP I flow. At that time, the

633‐ rigid and thick continental lithosphere covered the surface of the Earth to enable

634‐ stagnant lid tectonics and there was no oceanic lithosphere. Underneath the

635‐ continental lithosphere, there remained high temperature uppermost magma

636‐ ocean which was fertile and enriched in Fe. Through time, it was solidified but

637‐ those liquid may have episodically penetrated the stagnant lid to flood the

638‐ KREEP I. The bottom of the KREEP I as the MANUSCRIPT lower crust may have been dripping

639‐ down by the phase transformation, while numbers of rising mantle plume

640‐ underplated below the stagnant lid. Thus, the stagnant lid tectonics must have

641‐ prevailed since 4.53 Ga until 4.37 Ga when the ABEL Bombardment started.

642‐ Between 4.37 to 4.20 Ga, the ABEL Bombardment progressed.

643‐ Icy asteroids, derived from the outer margin of the asteroid belt at 4–5 AU, have ACCEPTED 644‐ been delivered to inner rocky planets. Owing to 50 times larger Earth’s mass

645‐ than the Moon, the Earth experienced heavier bombardment than the Moon.

646‐ Through this bombardment, the Earth was delivered oceanic and atmospheric

36‐ ‐ P a g e ‐|‐37373737‐‐‐‐ ACCEPTED MANUSCRIPT ‐

647‐ component including 10 km thick solid component (Maruyama and Ebisuzaki,

648‐ 2016). Estimated total mass of icy asteroid was in the order of 10 22 kg (Morgan,

649‐ 2001; Becker et al., 2006; Walker, 2009). The expected size of the largest

650‐ asteroid was 1000 km class in diameter, or larger than it. Those huge sized

651‐ asteroids reproduced nearly 70% of continental lithosphere (Marchi et al., 2014).

652‐ Due to the massive destruction of rigid continental lithosphere accompanying the

653‐ delivery of water component, oceanic lithosphere was generated to balance the

654‐ lost continental lithosphere. At the same time, water component, delivered by

655‐ bombardments, facilitated the eclogitization to initiate the operation of plate

656‐ tectonics. MANUSCRIPT

657‐ After 4.30 Ga, due to the operation of plate tectonics, primordial

658‐ continent composed of anorthosite, komatiite, and KREEP I started to be

659‐ removed into deep mantle by tectonic erosion. Anorthosite is being accumulated

660‐ at the top of the lower mantle due to density contrast. On the other hand, the

661‐ densest KREEP I among whole mantle dripped down to the bottom of the mantle ACCEPTED 662‐ to accumulate (almost all KREEP I should have accumulated at CMB by 4.0 Ga).

663‐ They contained 400 times more radioactive elements such as uranium,

664‐ potassium, and thorium than surrounding mantle, which heated up the bottom of

37‐ ‐ P a g e ‐|‐38383838‐‐‐‐ ACCEPTED MANUSCRIPT ‐

665‐ the lower mantle to generate plumes at CMB. Accumulated KREEP I at CMB

666‐ was once melting by radioactive decay heat, and then solidified to form anti-crust

667‐ composed of Fe-rich silicate, producing a stable rock unit called anti-crust, which

668‐ is density stratification contrasting to the crustal density stratification formed at

669‐ the surface (Maruyama et al., 2007). After the formation of anti-crust, residual

670‐ KREEP I is restite enriched in Ca-perovskite which split off from KREEP I to be

671‐ high temperature solid plume to travel upward through the lower mantle. They

672‐ finally accumulated at the top of the lower mantle as stable Ca rich layer. This

673‐ layer will grow until 2.6 Ga to be delivered to the surface of the Earth as flood

674‐ basalt by mantle overturn. On the other hand, MANUSCRIPT solid core also melts down due to

675‐ radioactive decay heat to result in the appearance of liquid core to generate the

676‐ strong geomagnetic field by 4.2 Ga (Tarduno et al., 2015).

677‐ By 4.20 Ga, TTG magma was generated to increase granitic

678‐ continental crust at the consuming plate boundary due to the operation of plate

679‐ tectonics. Removed anorthositic crust by tectonic erosion moved down to ACCEPTED 680‐ 660–1000 km depth to accumulate. Within the lower mantle, coming up plumes

681‐ from CMB travel to 660 km depth to accumulate there.

38‐ ‐ P a g e ‐|‐39393939‐‐‐‐ ACCEPTED MANUSCRIPT ‐

682‐ At 4.0 Ga, subducting oceanic lithosphere has accumulated at

683‐ 660 km depth as stagnant slab. TTG crust also removed from the surface

684‐ through tectonic erosion to accumulate at the mantle transition zone (410–660

685‐ km), forming second continent. At the bottom of the lower mantle, D” layer

686‐ mostly formed to be third continent (Kawai et al., 2009). Gradually, the upper

687‐ mantle depleted basaltic component by plate tectonic operation or arc

688‐ subduction to cool down and weaken the mantle convection. Through the time,

689‐ upper mantle cooled down against warming lower mantle by radiogenic heating

690‐ from the D” layer. Finally, mantle overturn occurred at 2.6 Ga due to local

691‐ inversion of density between upper and lower MANUSCRIPT mantle.

692‐ 5. Discussion

693‐ The formation of the Earth has long been discussed in many studies,

694‐ and majority of researchers considered that the Earth was covered by ocean and

695‐ atmosphere since the birth of the planet at ca. 4.567 Ga. In the newly proposed

696‐ ABEL (advent of bio-elements) model, specific aspects associated with the ACCEPTED 697‐ formation of Earth were reconsidered based on material science derived from

698‐ chronology of meteorites and the Moon, and analyses of isotopic ratios.

699‐ According to the ABEL model, the Earth was born as a completely dry planet

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700‐ from enstatite chondrite-like materials, and oceanic and atmospheric

701‐ components (which are bio-elements such as carbon (C), hydrogen (H), oxygen

702‐ (O), and nitrogen (N)) were delivered as secondary components together with

703‐ other volatiles and siderophile elements from outer asteroid belt due to

704‐ gravitational disturbance by three gas giants of Jupiter, Saturn, and currently

705‐ missing “Black Sheep” during 4.37–4.20 Ga (Maruyama and Ebisuzaki, 2016).

706‐ The recent investigations suggest that the LHB occurred in the middle of

707‐ Hadean (Hopkins and Mojzsis, 2015). Maruyama and Ebisuzaki (2016)

708‐ redefined the event as ABEL Bombardment and proposed this to be the most

709‐ important event to evolve Earth into life sustaininMANUSCRIPTg planet. During the 170 Myr

710‐ long bombardments, global hydrological material circulation began to change

711‐ chemical composition and volume of ocean and atmosphere. Moreover, the

712‐ ABEL Bombardment could be the trigger of operation of plate tectonics as well

713‐ as the initiation of metabolism for the emergence of life. Based on this redefined

714‐ significant event, we propose the subdivisions of Hadean Eon into 3 periods; i.e. ACCEPTED 715‐ the early Hadean (4.567–4.37 Ga; from the formation age of dry Earth until the

716‐ beginning of ABEL Bombardment), the middle Hadean (4.37–4.20 Ga; period of

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717‐ ABEL Bombardment), and the late Hadean (4.20–4.0 Ga; after ABEL

718‐ Bombardment and the period to bear life).

719‐ The early Hadean is characterized by dry rocky planet without ocean

720‐ and atmosphere. It is important to have this period as the reductive planet. The

721‐ mixing of reductive material and oxidized material is the trigger of the

722‐ metabolism to lead to the emergence of life. The middle Hadean started with the

723‐ most important event on the whole Earth history which is the advent of

724‐ bio-elements (ABEL Bombardment) occurred by bombardment of carbonaceous

725‐ chondrites caused by the gravitational disturbance of asteroid belt by three gas

726‐ giants; i.e. Jupitar, Saturn, and the missing MANUSCRIPT third big giant “Black Sheep”.

727‐ Through the accumulation of water components on the Earth, primordial ocean

728‐ appeared for the first time to initiate the plate tectonics on this planet. After this

729‐ significant event, the Earth witnessed the late Hadean which must have the

730‐ emergence of life with the global material circulation driven by plate tectonics.

731‐ One more point to be emphasized here is the terrific destruction of the ACCEPTED 732‐ surface of the Earth was caused through the ABEL Bombardment. The size of

733‐ impactors of bombardments were expected to be huge, and larger in earlier

734‐ stage of the ABEL Bombardment to cause Pacific Ocean sized crater on the

41‐ ‐ P a g e ‐|‐42424242‐‐‐‐ ACCEPTED MANUSCRIPT ‐

735‐ Earth to destroy rigid continental lithosphere and newly formed oceanic

736‐ lithosphere. As a result, bi-modal lithosphere appeared to initiate the operation

737‐ of plate tectonics. However, current majority of researchers have totally different

738‐ image for such a bombardment event, for example, LHB is regarded to be minor

739‐ event and it did not play important role through the Earth’s history. On the

740‐ contrary, the ABEL model suggested completely dissimilar scenario. Further

741‐ researches should demonstrate or validate previously proposed models based

742‐ on detailed analyses using specific material such as meteorites, and returned

743‐ samples including lunar rocks.

744‐ MANUSCRIPT

745‐ 6. Conclusion

746‐ Plate tectonics is a unique feature restricted to the modern Earth among

747‐ other planets in our solar system. Among the various factors that initiated and

748‐ operated plate tectonics, the most critical is the presence of water.

749‐ The Earth was formed as a dry reductive planet at 4.567 Ga, after which ACCEPTED 750‐ volatiles were delivered from outer asteroid belts by carbonaceous chondrites at

751‐ 4.37–4.20 Ga due to gravitational disturbance of asteroid belt by three gas

752‐ giants of Jupiter, Saturn, and missing “Black Sheep”. This event is called ABEL

42‐ ‐ P a g e ‐|‐43434343‐‐‐‐ ACCEPTED MANUSCRIPT ‐

753‐ Bombardment which is the trigger of the operation of plate tectonics on Hadean

754‐ Earth with the formation of ocean and atmosphere.

755‐ In earlier stage of the ABEL Bombardment, 1000 km across impactors

756‐ bombarded the Earth to destroy rigid continental lithosphere operating stagnant

757‐ lid tectonics since the formation of the Earth. Due to terrific destruction by

758‐ gigantic impactor to create Pacific Ocean class crater, oceanic lithosphere was

759‐ generated on the surface of the Earth for the first time through the history.

760‐ Through the ABEL Bombardment, water component accumulated as ocean

761‐ gradually, and mixed into the interior of the Earth through bombardments.

762‐ Through this process, eclogitization facilitated MANUSCRIPT to initiate the operation of plate

763‐ tectonics at bi-modal lithosphere. Eclogitization of primordial continental crust at

764‐ both upper and lower, caused by the ABEL Bombardment, gave the strong

765‐ slab-pull force to initiate the process of subduction. This is the scenario to shift

766‐ from stagnant lid tectonics to modern plate tectonics.

767‐ Because of the significance of the events of initiation of plate tectonics ACCEPTED 768‐ on the Earth which lead to the emergence of life, a subdivision of Hadean Eon is

769‐ proposed as follows: (1) the early Hadean (4.57–4.37 Ga), the middle Hadean

770‐ (4.37–4.20 Ga), and the late Hadean (4.20–4.00 Ga).

43‐ ‐ P a g e ‐|‐44444444‐‐‐‐ ACCEPTED MANUSCRIPT ‐

771‐ Acknowledgement

772‐ This research was supported by Grant-in-Aid for Scientific Research on

773‐ Innovative Areas Grant Number 26106002. Authors thank Ms. Reiko Hattori for

774‐ technical assistance to complete this paper.

775‐ References

776‐ Alt, J.C., Honnorez, J., Laverne, C., Emmermann, R., 1986. Hydrothermal

777‐ alteration of a 1-km section through the upper oceanic-rust, deep-sea

778‐ drilling project hole 504B: Mineralogy, chemistry, and evolution of

779‐ seawater-basalt interactions. Journal of Geophysical Research-Solid Earth

780‐ and Planets 91, 309-335. MANUSCRIPT

781‐ Arzi, A.A., 1978. Critical phenomena in the rheology of partially melted rocks.

782‐ Tectonophysics 44, 173-184.

783‐ Amelin, Y., Kaltenbach, A., Iizuka, T., Stirling, C.H., Ireland, T.R., Petaev, M.,

784‐ Jacobsen, S.B., 2010. U–Pb chronology of the Solar System's oldest solids

785‐ with variable 238U/235U. Earth and Planetary Science Letters 300, ACCEPTED 786‐ 343-350.

44‐ ‐ P a g e ‐|‐45454545‐‐‐‐ ACCEPTED MANUSCRIPT ‐

787‐ Amelin, Y., Krot, A.N., Hutcheon, I.D., Ulyanov, A.A., 2002. Lead isotopic ages

788‐ of chondrules and calcium-aluminum-rich inclusions. Science 297,

789‐ 1678-1683.

790‐ Azuma, S., Katayama, I., Nakakuki, T., 2014. Rheological decoupling at the

791‐ Moho and implication to Venusian tectonics. Scientific Reports 4, 4403,

792‐ doi:10.1038/srep04403.

793‐ Becker, H., Horan, M.F., Walker, R.J., Gao, S., Lorand, J.P., Rudnick, R.L., 2006.

794‐ Highly siderophile element composition of the Earth’s primitive upper mantle:

795‐ Constraints from new data on peridotite massifs and xenoliths. Geochimica

796‐ et Cosmochimica Acta 70, 4528-4550. MANUSCRIPT

797‐ Borg, L.E., Gaffney, A.M., Shearer, C.K., 2015. A review of lunar chronology

798‐ revealing a preponderance of 4.34–4.37 Ga ages. Meteoritics & Planetary

799‐ Science 50, 715-732.

800‐ Byerlee, J. D., 1978. Friction of rocks.‐Pure and Applied Geophysics 116,

801‐ 615–626. ACCEPTED 802‐ Burke, K., 1988. Tectonic evolution of the Caribbean. Annual Review of Earth

803‐ and Planetary Sciences 16, 201-230.

45‐ ‐ P a g e ‐|‐46464646‐‐‐‐ ACCEPTED MANUSCRIPT ‐

804‐ Dewey, J.F., Bird, J.M., 1971. Origin and emplacement of ophiolite suite:

805‐ Appalachian ophiolites in Newfoundland. Journal of Geophysical Research

806‐ 76, 3179-3206.

807‐ Dohm, J.M., Maruyama, S., 2015. Habitable trinity. Geoscience Frontiers 6,

808‐ 95-101.

809‐ Ebisuzaki, T., Maruyama, S., 2016. Nuclear geyser model of the origin of life: 810‐ driving force to promote the synthesis of building blocks of life. Geoscience 811‐ Frontiers. http://dx.doi.org/10.1016/j.gsf.2016.09.005

812‐ Forsyth, D., Uyeda, S., 1975. Relative importance of driving forces of plate

813‐ motion. Geophysical Journal of the Royal Astronomical Society 43,

814‐ 163-200. MANUSCRIPT 815‐ Fukao, Y., 1992. Seismic tomogram of the Earths mantle: geodynamic

816‐ implications. Science 258, 625-630.

817‐ Furnes, H., de Wit, M., Staudigel, H., Rosing, M., Muehlenbachs, K., 2007. A

818‐ vestige of Earth's oldest ophiolite. Science 315, 1704-1707.

819‐ Hamilton, W.B., 2011. Plate tectonics began in Neoproterozoic time, and plumes

820‐ from deepACCEPTED mantle have never operated. Lithos 123, 1-20.

821‐ Harrison, T.M., Blichert-Toft, J., Muller, W., Albarede, F., Holden, P., Mojzsis,

822‐ S.J., 2005. Heterogeneous Hadean hafnium: Evidence of continental crust

823‐ at 4.4 to 4.5 Ga. Science 310, 1947-1950. 46‐ ‐ P a g e ‐|‐47474747‐‐‐‐ ACCEPTED MANUSCRIPT ‐

824‐ Hasegawa, A., Nakajima, J., Uchida, N., Okada, T., Zhao, D., Matsuzawa, T.,

825‐ Umino, N., 2009. Plate subduction, and generation of earthquakes and

826‐ magmas in Japan as inferred from seismic observations: An overview.

827‐ Gondwana Research 16, 370-400.

828‐ Hasegawa, A., Nakajima, J., Umino, N., Miura, S., 2005. Deep structure of the

829‐ northeastern Japan arc and its implications for crustal deformation and

830‐ shallow seismic activity. Tectonophysics 403, 59-75.

831‐ Hasegawa, A., Nakajima, J., Yanada, T., Uchida, N., Okada, T., Zhao, D.,

832‐ Matsuzawa, T., Umino, N., 2013. Complex slab structure and arc

833‐ magmatism beneath the Japanese Islands. MANUSCRIPT Journal of Asian Earth Sciences

834‐ 78, 277-290.

835‐ Hirth, G., Kohlstedt, D. L., 2003. Rheology of the upper mantle and the mantle

836‐ wedge: A view from the experimentalists. Inside the Subduction Factory,

837‐ Geophysical Monograph 138, pp. 83–105.

838‐ Hopkins, M., Harrison, T.M., Manning, C.E., 2008. Low heat flow inferred from > ACCEPTED 839‐ 4 Gyr zircons suggests Hadean plate boundary interactions. Nature 456,

840‐ 493-496.

47‐ ‐ P a g e ‐|‐48484848‐‐‐‐ ACCEPTED MANUSCRIPT ‐

841‐ Hopkins, M.D., Mojzsis, S.J., 2015. A protracted timeline for lunar bombardment

842‐ from mineral chemistry, Ti thermometry and U–Pb geochronology of Apollo

843‐ 14 melt breccia zircons. Contributions to Mineralogy and Petrology 169,

844‐ 1-18.

845‐ Irifune, T., Ringwood, A.E., Hibberson, W.O., 1994. Subduction of

846‐ continental-crust and terrigenous and pelagic sediments: An

847‐ experimental-study. Earth and Planetary Science Letters 126, 351-368.

848‐ Ishikawa, A., Kuritani, T., Makishima, A., Nakamura, E., 2007. Ancient recycled

849‐ crust beneath the ontong Java plateau: Isotopic evidence from the garnet

850‐ clinopyroxenite xenoliths, Malaita, Solomon MANUSCRIPT Islands. Earth and Planetary

851‐ Science Letters 259, 134-148.

852‐ Karato, S., Jung, H., 2003. Effects of pressure on high-temperature dislocation

853‐ creep in olivine. Philosophical Magazine A83, 401–414.

854‐ Karato, S., Wu, P., 1993. Rheology of the upper mantle: A synthesis. Science

855‐ 260, 771–778, doi: 10.1126/science.260.5109.771. ACCEPTED 856‐ Katayama, I., Karato, S. 2008. Low-temperature, high-stress deformation of

857‐ olivine under water-saturated conditions.‐Physics of the Earth and Planetary

858‐ Interiors 168, 125–133.

48‐ ‐ P a g e ‐|‐49494949‐‐‐‐ ACCEPTED MANUSCRIPT ‐

859‐ Katayama, I., Maruyama, S., 2009. Inclusion study in zircon from

860‐ ultrahigh-pressure metamorphic rocks in the Kokchetav massif: an excellent

861‐ tracer of metamorphic history. Journal of the Geological Society 166,

862‐ 783-796.

863‐ Kawai, K., Tsuchiya, T., Tsuchiya, J., Maruyama, S., 2009. Lost primordial

864‐ continents. Gondwana Research 16, 581-586.

865‐ Kohlstedt, D.L., Evans, B., Mackwell, S.J., 1995. Strength of the lithosphere:

866‐ Constraints imposed by laboratory experiments. Journal of Geophysical

867‐ Research: Solid Earth 100, 17587-17602.

868‐ Komabayashi, T., Hirose, K., Sata, N., Ohishi,MANUSCRIPT Y., Dubrovinsky, L.S., 2007.

869‐ Phase transition in CaSiO3 perovskite. Earth and Planetary Science Letters

870‐ 260, 564-569.

871‐ Komiya, T., 2004. Material circulation model including chemical differentiation

872‐ within the mantle and secular variation of temperature and composition of

873‐ the mantle. Physics of the Earth and Planetary Interiors 146, 333–367. ACCEPTED 874‐ Komiya, T., Maruyama, S., 2007. A very hydrous mantle under the western

875‐ Pacific region: Implications for formation of marginal basins and style of

876‐ Archean plate tectonics. Gondwana Research 11, 132-147.

49‐ ‐ P a g e ‐|‐50505050‐‐‐‐ ACCEPTED MANUSCRIPT ‐

877‐ Komiya, T., Maruyama, S., Masuda, T., Nohda, S., Hayashi, M., Okamoto, K.,

878‐ 1999. Plate tectonics at 3.8-3.7 Ga: Field evidence from the Isua

879‐ Accretionary Complex, southern West Greenland. Journal of Geology 107,

880‐ 515-554.

881‐ Komiya, T., Yamamoto, S., Aoki, S., Sawaki, Y., Ishikawa, A., Tashiro, T.,

882‐ Koshida, K., Shimojo, M., Aoki, K., Collerson, K.D., 2015. Geology of the

883‐ Eoarchean, > 3.95 Ga, Nulliak supracrustal rocks in the Saglek Block,

884‐ northern Labrador, Canada: The oldest geological evidence for plate

885‐ tectonics. Tectonophysics 662, 40-66.

886‐ Korenaga, J., 2010. On the likelihood of plateMANUSCRIPT tectonics on super-Earths: Does

887‐ size matter? The Astrophysical Journal Letters 725, L43.

888‐ Kubo, T., and Katayama, I., 2015, Effect of temperature on the frictional behavior

889‐ of smectite and illite. Journal of Mineralogical and Petrological Sciences 110,

890‐ 239¬–299.

891‐ Kumazawa, M., Maruyama, S., 1994. Whole earth tectonics. Journal of ACCEPTED 892‐ Geological Society of Japan 100, 81-102.

893‐ Larson, R.L., 1991. Geological consequences of Superplumes. Geology 19,

894‐ 963-966.

50‐ ‐ P a g e ‐|‐51515151‐‐‐‐ ACCEPTED MANUSCRIPT ‐

895‐ Le Pichon, X., 1968. Sea-floor spreading and continental drift. Journal of

896‐ Geophysical Research 73, 3661-3697.

897‐ Marchi, S., Bottke, W.F., Elkins-Tanton, L.T., Bierhaus, M., Wuennemann, K.,

898‐ Morbidelli, A., Kring, D.A., 2014. Widespread mixing and burial of Earth's

899‐ Hadean crust by asteroid impacts. Nature 511, 578-582.

900‐ Maruyama, S., 1994. Plume tectonics. Journal of Geological Society of Japan

901‐ 100, 24-49.

902‐ Maruyama, S., Ebisuzaki, T., 2016. Origin of the Earth: a proposal of new model 903‐ called ABEL. Geoscience Frontiers. 904‐ http://dx.doi.org/10.1016/j.gsf.2016.10.005.‐

905‐ Maruyama, S., Ikoma, M., Genda, H., Hirose, K., Yokoyama, T., Santosh, M., MANUSCRIPT 906‐ 2013. The naked planet Earth: Most essential pre-requisite for the origin

907‐ and evolution of life. Geoscience Frontiers 4, 141-165.

908‐ Maruyama, S., Liou, J.G., 2005. From snowball to Phanerozoic Earth.

909‐ International Geology Review 47, 775-791.

910‐ Maruyama, S., Liou, J.G., Terabayashi, M., 1996. Blueschists and eclogites of

911‐ the worldACCEPTED and their exhumation. International Geology Review 38, 485-594.

912‐ Maruyama, S., Santosh, M., Zhao, D., 2007. Superplume, supercontinent, and

913‐ post-perovskite: Mantle dynamics and anti-plate tectonics on the

914‐ Core-Mantle Boundary. Gondwana Research 11, 7-37. 51‐ ‐ P a g e ‐|‐52525252‐‐‐‐ ACCEPTED MANUSCRIPT ‐

915‐ Maruyama, S., Terabayashi, M., Fujioka, K., 1989. Origin and Emplacement of

916‐ Ophiolite: A Review. Journal of Geography (Chigaku Zasshi) 98, 319-349.

917‐ McGovern, P.J., Schubert, G., 1989. Thermal evolution of the Earth: effects of

918‐ volatile exchange between atmosphere and interior. Earth and Planetary

919‐ Science Letters 96, 27-37.

920‐ McKenzie, D.P., 1969. Speculations on the consequences and causes of plate

921‐ motions. Geophysical Journal International 18, 1-32.

922‐ Moresi, L.N., Solomatov, V.S., 1995. Numerical investigation of 2D convection

923‐ with extremely large viscosity variations. Physics of Fluids 7, 2154-2162.

924‐ Moresi, L., Solomatov, V., 1998. Mantle MANUSCRIPT convection with a brittle lithosphere:

925‐ thoughts on the global tectonic styles of the Earth and Venus. Geophysical

926‐ Journal International 133, 669-682.

927‐ Morgan, W.J., 1968. Rises, trenches, great faults, and crustal blocks. Journal of

928‐ Geophysical Research 73, 1959-1982.

929‐ Morgan, J.W., Walker, R.J., Brandon, A.D., Horan, M.F., 2001. Siderophile ACCEPTED 930‐ elements in Earth's upper mantle and lunar breccias: Data synthesis

931‐ suggests manifestations of the same late influx. Meteoritics & Planetary

932‐ Science 36, 1257-1275.

52‐ ‐ P a g e ‐|‐53535353‐‐‐‐ ACCEPTED MANUSCRIPT ‐

933‐ Morrow, C. A., Moore, D.E., Lockner, D.A., 2000. The effect of mineral bond

934‐ strength and absorbed water on fault gouge frictional strength. Geophysical

935‐ Research Letters 27, 815-818.

936‐ Murakami, M., Hirose, K., Yurimoto, H., Nakashima, S., Takafuji, N., 2002.

937‐ Water in Earth's lower mantle. Science 295, 1885-1887.

938‐ Nehlig, P., 1993. Interactions between magma chambers and hydrothermal

939‐ systems: Oceanic and ophiolitic constraints. Journal of Geophysical

940‐ Research: Solid Earth 98, 19621-19633.

941‐ Okamoto, K., Maruyama, S., 1999. The high-pressure synthesis of lawsonite in

942‐ MANUSCRIPT the MORB+H 2O system. American Mineralogist 84, 362-373.

943‐ Okamoto, K., Maruyama, S., 2004. The eclogite-gametite transformation in the

944‐ MORB+H 2O system. Physics of the Earth and Planetary Interiors 146,

945‐ 283-296.

946‐ Reese, C.C., Solomatov, V.S., Moresi, L.N., 1998. Heat transport efficiency for

947‐ stagnant lid convection with dislocation viscosity: Application to Mars and ACCEPTED 948‐ Venus. Journal of Geophysical Research: Planets 103, 13643-13657.

53‐ ‐ P a g e ‐|‐54545454‐‐‐‐ ACCEPTED MANUSCRIPT ‐

949‐ Rybacki, E., Dresen, G., 2000. Dislocation and diffusion creep of synthetic

950‐ anorthite aggregates. Journal of Geophysical Research, 105,

951‐ 26017–26036.

952‐ Solomatov, V.S., 1995. Scaling of temperature and stress dependent

953‐ viscosity convection. Physics of Fluids 7, 266-274.

954‐ Solomatov, V.S., Moresi, L.N., 1996. Stagnant lid convection on Venus. Journal

955‐ of Geophysical Research: Planets 101, 4737-4753.

956‐ Solomatov, V.S., Zharkov, V.N., 1990. The thermal regime of Venus. Icarus 84,

957‐ 280-295.

958‐ Stern, R.J., 2005. Evidence from ophiolites, MANUSCRIPT blueschists, and ultrahigh-pressure

959‐ metamorphic terranes that the modern episode of subduction tectonics

960‐ began in Neoproterozoic time. Geology 33, 557-560.

961‐ Tarduno, J.A., Cottrell, R.D., Davis, W.J., Nimmo, F., Bono, R.K., 2015. A

962‐ Hadean to Paleoarchean geodynamo recorded by single zircon crystals.

963‐ Science 349, 521-524. ACCEPTED 964‐ Turcotte, D. L., Schubert, G., 2002. Geodynamics, 2nd Edition. Cambridge

965‐ University Press, New York, pp. 132–144,

54‐ ‐ P a g e ‐|‐55555555‐‐‐‐ ACCEPTED MANUSCRIPT ‐

966‐ Turner, S., Rushmer, T., Reagan, M., Moyen, J.-F., 2014. Heading down early

967‐ on? Start of subduction on Earth. Geology 42, 139-142.

968‐ Walker, R.J., 2009. Highly siderophile elements in the Earth, Moon and Mars:

969‐ Update and implications for planetary accretion and differentiation. Chemie

970‐ der Erde - Geochemistry 69, 101-125.

971‐ Wilde, S.A., Valley, J.W., Peck, W.H., Graham, C.M., 2001. Evidence from

972‐ detrital zircons for the existence of continental crust and oceans on the

973‐ Earth 4.4 Gyr ago. Nature 409, 175-178.

974‐ Zhao, D.P., 2004. Global tomographic images of mantle plumes and subducting

975‐ slabs: insight into deep Earth dynamics. MANUSCRIPT Physics of the Earth and Planetary

976‐ Interiors 146, 3-34.

977‐ Zhao, D., 2007. Seismic images under 60 hotspots: Search for mantle plumes.

978‐ Gondwana Research 12, 335-355.

979‐ Zhao, D., 2009. Multiscale seismic tomography and mantle dynamics.

980‐ Gondwana Research 15, 297-323. ACCEPTED 981‐ Zhao, D., Maruyama, S., Omori, S., 2007. Mantle dynamics of Western Pacific

982‐ and East Asia: Insight from seismic tomography and mineral physics.

983‐ Gondwana Research 11, 120-131.

55‐ ‐ P a g e ‐|‐56565656‐‐‐‐ ACCEPTED MANUSCRIPT ‐

984‐

985‐ Figure captions

986‐ 987‐

988‐ Figure 1. A summary of planetary tectonics (modified after Kumazawa and

989‐ Maruyama, 1994). The mechanism of plate tectonics is dominant in upper

990‐ mantle of present day Earth. In contrast, Mars and Venus are dominated by

991‐ stagnant-lid convection at present in which the mantle convection is caused by

992‐ upwelling and downwelling of plumes only beneath a rigid and immobile lid or

993‐ plate.

994‐ MANUSCRIPT

995‐ Figure 2. Shape change of lithosphere from the surface through mantle

996‐ transition zone and in the lower mantle. Platy lithosphere is created at

997‐ mid-oceanic ridge which moves to the trench and subducts down to 660 km

998‐ depth. At the mantle transition zone from 410 to 660 km, the platy structure

999‐ becomes unclear and also stagnation has been identified. From this depth to ACCEPTED 1000‐ bottom of the core-mantle boundary (CMB), the plates do not show the simple

1001‐ curtain like structure. Instead, blob shaped structure can be seen presumably in

1002‐ the transition zone.

56‐ ‐ P a g e ‐|‐57575757‐‐‐‐ ACCEPTED MANUSCRIPT ‐

1003‐

1004‐ Figure 3. Plate boundary processes: Plate boundary processes of divergent (A,

1005‐ B), convergent (C, D) and transform fault boundaries. Formation of new plate

1006‐ proceeds at divergent plate boundary at mid-oceanic ridge (A) and also in

1007‐ continental rift (B). Pacific-type (C) and collision-type orogenies (D) occur at

1008‐ consuming plate boundary.

1009‐

1010‐ Figure 4. Global water circulation in association of birth of plate and consumption

1011‐ of plate at 660 km depth (modified after Maruyama and Liou, 2005). The

1012‐ hydrated topmost part of lithosphere moves MANUSCRIPT horizontally to subduction zones

1013‐ where it descents into the deep mantle accompanied by progressive dehydration

1014‐ along the subduction zone geotherm. Dehydrated fluid is removed to the upper

1015‐ seismic zones. Fluids released during progressive dehydration play a critical role

1016‐ as lubricant and imparts a slippery top surface of the down-going plate. Thus,

1017‐ both top and bottom boundaries of the plate act as slippage planes in subduction ACCEPTED 1018‐ zones. The lower zone of the double seismic plane starts from right inside the

1019‐ trench axis and both the lower and upper zones are located not within the

57‐ ‐ P a g e ‐|‐58585858‐‐‐‐ ACCEPTED MANUSCRIPT ‐

1020‐ oceanic crust, but in the peridotite slab. The double seismic zone converges at

1021‐ around 200 km depth, and finally disappears.

1022‐

1023‐ Figure 5. Frictional intensity as a function of water. In the calculation of the

1024‐ rheological structures, the rock strength in brittle regions is calculated not only

1025‐ from Byerlee’s law (Byerlee, 1978), but also frictional coefficient of sheet silicate

1026‐ minerals under saturated conditions. It is inferred that the plate strength notably

1027‐ depends on whether the water covers the plate boundaries because the

1028‐ frictional strength itself of sheet silicate mineral decreases under water-saturated MANUSCRIPT 1029‐ conditions.

1030‐ Figure 6. Differential stress (MPa) vs. depth at given temperature to define the

1031‐ strength of lithospheric plate. (A) Thermal structures of oceanic plate at plate

1032‐ age of 10–40 Myr in Hadean Earth. The thermal structures are calculated from a

1033‐ model of transient half-space cooling at given mantle and surface temperature

1034‐ parameters at 1600 ºC as the liquids temperature of mantle peridotite and 100 ACCEPTED 1035‐ ºC, respectively, (B), (C), and (D) shows the calculated rheological structures at

1036‐ plate age of 10–40 Myr in Hadean Earth. Plate strength is different between wet

58‐ ‐ P a g e ‐|‐59595959‐‐‐‐ ACCEPTED MANUSCRIPT ‐

1037‐ and dry conditions because of the effect of water to friction coefficient of sheet

1038‐ silicate mineral.

1039‐

1040‐ Figure 7. Change of plate strength in Hadean Earth. If the early Earth was a

1041‐ naked planet without ocean, the plate strength of the Earth was quite high to

1042‐ operate the stagnant lid tectonics. However, the formation of ocean made the

1043‐ strength of plate (<200–300 MPa) and plate boundaries (frictional coefficient <

1044‐ 0.1–0.2) weak (Fig. 7), and facilitated the eclogitization. The decrease of plate

1045‐ strength promoted the development of plate boundaries and the independent

1046‐ motion of plate, indicating that the Earth would MANUSCRIPT have potential for the initiation of

1047‐ plate tectonics in the Hadean.

1048‐

1049‐ Figure 8. Schematic model for ABEL Bombardment. Due to repeated

1050‐ bombardment by carbonaceous chondrites from outer asteroid belts, the

1051‐ primordial continents were destroyed and brecciated to mix with sub-micron ACCEPTED 1052‐ sized dust originated from asteroids and primordial continents, such as glassy

1053‐ tektites, orange or green soils, and breccias. The sediment generated by

1054‐ crashed materials may have accumulated over a few km to cover the primordial

59‐ ‐ P a g e ‐|‐60606060‐‐‐‐ ACCEPTED MANUSCRIPT ‐

1055‐ continents. At the same time, the formation of atmosphere and hydrosphere

1056‐ gradually progressed due to the accumulation of water components, CO 2, and

1057‐ N2 through ABEL Bombardments.

1058‐

1059‐ Figure 9. Initiation of plate tectonics. (A) Plate tectonics was initiated by

1060‐ generation of slab-pull force through eclogitization of thick KREEP lower crust

1061‐ (ca. 100 km) together with anorthositic upper crust (21 km thick) under the ABEL

1062‐ Bombardment which delivered volatiles onto dry Earth for the first time. It may

1063‐ have continued a few to several hundred millions years during 4.37–4.20 Ga.

1064‐ Associated with the development of trench MANUSCRIPT line along the continental margin,

1065‐ mantle upwelling by plumes made topographic highs to push up primordial

1066‐ continents, which generated ridge pull force. (B) Eclogitization started after

1067‐ volatiles were delivered by ABEL Bombardment. Denser eclogite generated slab

1068‐ pull force to initiate plate tectonics.

1069‐ ACCEPTED 1070‐ Figure 10. Phase diagram of MORB + H 2O system to explain eclogitization

1071‐ (modified after Maruyama et al., 1996; Okamoto and Maruyama, 2004). The

1072‐ green arrowed lines are the Hadean and Phanerozoic subduction zone

60‐ ‐ P a g e ‐|‐61616161‐‐‐‐ ACCEPTED MANUSCRIPT ‐

1073‐ geotherms along the Benioff plane. In Hadean, the temperature of mantle was

1074‐ high enough, therefore solid-melt region should have been smaller, and wet

1075‐ solidus was closer to the dry solidus. The density of eclogite (ca. 3.5–4.0 g/cm 3)

1076‐ is markedly higher than that of the surrounding mantle peridotite (ca. 3.5 g/cm 3),

1077‐ which produces strong slab pull force. In the rock assemblage consisting of

1078‐ lithosphere at the initiation of plate tectonics, KREEP lower crust is thought to be

1079‐ extremely thick over 100 km, compared to 6 km of modern Earth or 20 km in

1080‐ early Archean. The combination of bigger sized crustal body and high density in

1081‐ Hadean becomes the most important factor to initiate the operation of plate

1082‐ tectonics. MANUSCRIPT

1083‐

1084‐ Figure 11. (A) Early Earth’s impactor size-frequency: The red curve corresponds

1085‐ to current main-belt asteroids larger than 10 km across where Ceres is the

1086‐ largest object (~913 km in diameter). Black curve is extrapolated to 4000 km

1087‐ across object by using the slop in the size range 500–913 km in diameter. Note ACCEPTED 1088‐ that larger impactor than Ceres could make more than the Pacific Ocean size

1089‐ crater by single bombardment (modified after Marchi et al., 2014). (B) Melt

1090‐ spreading over the first 100 Myr of the Earth history: Cumulative record of

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1091‐ craters at four different times (Marchi et al., 2014). At each time step, Earth’s

1092‐ surface has the region that are not influenced by impact-induced melt, excepting

1093‐ for >4.475 Gyr. However, almost all Earth’s surface is affected by impactors by

1094‐ 4.4 Gyr.

1095‐

1096‐ Figure 12. Hadean history of the Earth. At 4.55 Ga, dry Earth was formed. By

1097‐ 4.53 Ga, mantle was solidified to form layered structure and stagnant lid

1098‐ tectonics operated. Between 4.37 and 4.20 Ga, ABEL Bombardment progressed

1099‐ deliver atmospheric and oceanic components on dry Earth. Due to great

1100‐ destruction of stagnant lid by huge impactors, MANUSCRIPT stagnant lid tectonics shifted to

1101‐ plate tectonics. By 4.30 Ga, bi-modal lithosphere (continental curst and oceanic

1102‐ crust) appeared following to bombardment to operate plate tectonics. Due to

1103‐ tectonic erosion, primordial continent (anorthosite, komatiite, and KREEP I) was

1104‐ removed into deep mantle. The densest KREEP I dripped down to the bottom of

1105‐ the mantle to accumulate (almost all KREEP I should have accumulated at CMB ACCEPTED 1106‐ by 4.0 Ga). KREEP I heated up the bottom of the lower mantle to generate

1107‐ plumes at CMB due to radioactive decay heat, where anti-crust formed at the

1108‐ same time. Restite enriched in Ca-perovskite split off from KREEP I as high

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1109‐ temperature solid plume to accumulate at the top of the lower mantle. On the

1110‐ other hand, solid core also melts down due to radioactive decay heat. By 4.20

1111‐ Ga, TTG magma was generated to increase granitic continental crust at the

1112‐ consuming plate boundary. Removed anorthositic crust moved down to

1113‐ 660–1000 km depth to accumulate. Within the lower mantle, coming up plumes

1114‐ from CMB accumulated at 660 km depth. At 4.0 Ga, subducting oceanic

1115‐ lithosphere has accumulated at 660 km depth as stagnant slab. TTG crust also

1116‐ removed from the surface to accumulate at the mantle transition zone (410–660

1117‐ km), forming second continent. At the bottom of the lower mantle, D” layer

1118‐ mostly formed to be third continent. MANUSCRIPT

1119‐

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Initiation of plate tectonics in the Hadean:

Eclogitization triggered by the ABEL Bombardment

S. Maruyama a,b,*, M. Santosh c,d,e , S. Azuma a a Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1, Ookayama-Meguro-ku, Tokyo 152-8550, Japan b Institute for Study of the Earth’s Interior, Okayama University, 827 Yamada, Misasa, Tottori 682-0193, Japan c Centre for Tectonics, Resources and Exploration, Department of Earth Sciences, University of Adelaide, SA 5005, Australia d School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China e Faculty of Science, Kochi University, Kochi 780-8520, Japan *Corresponding author. E-mail address: smaruyam@geo MANUSCRIPT.titech.ac.jp

Research Highlights

Presence of water is the most critical factor for plate tectonics

Bombardment of carbonaceous chondrites delivered water on completely dry

Earth
EclogitizationACCEPTED provided slab-pull force to initiate plate tectonics
Stagnant lid tectonics shifted to plate tectonics by the ABEL Bombardment