Two distinct origins for Archean greenstone belts

Smithies, R. Hugh; Ivanic, Tim J.; Lowrey, Jack R.; Morris, Paul A.; Barnes, Stephen J.; Wyche, Stephen; Lu, Yongjun

doi:10.1016/j.epsl.2018.01.034

Cited by 139 publications

(57 citation statements)

References 47 publications

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“…Such suites are fairly uncommon worldwide, with the Whundo group in the Pilbara the only known example from the Palaeo-to Mesoarchaean. These lithologies are associated with mafic to dacitic volcanics, and are (from 2.95 Ga) associated with sanukitoids [19]. As such, these observations are most consistent with an association of these particular rocks with mature subduction that has evolved past the initiation stage.…”

Section: (D) Greenstones: a Failure To Launchsupporting

confidence: 57%

“…This contrasts with what they defined as 'variable' Th/Nb trends (steeper than the MORB array in figure 8), which indicate a mixing trend between MORB and a crustal component (here TTGs). Smithies et al [19] suggest that constant Th/Nb trends are rare in Archaean rocks of the Pilbara and Yilgarn terranes, occurring mostly in suites between 3.13 and 2.95 Ga in the Pilbara, and between 2.82 and 2.71 Ga in the Yilgarn. Such suites are fairly uncommon worldwide, with the Whundo group in the Pilbara the only known example from the Palaeo-to Mesoarchaean.…”

Section: (D) Greenstones: a Failure To Launchmentioning

confidence: 99%

“…Together, the geological record indicates periods of tectonic activity extending into the Mesoarchaean, and arguably subduction [19]. But it is not clear whether (i) subduction resembled modern (cold) subduction zones, (ii) developed into a globally connected plate boundary network, (iii) continued, once begun, unabated to the present, or sporadically ceased [20], and (iv) if indeed it regularly proceeded past the subduction initiation hurdle.…”

Section: Introductionmentioning

confidence: 99%

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The inception of plate tectonics: a record of failure

O’Neill¹,

Turner²,

Rushmer³

2018

Phil. Trans. R. Soc. A.

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The development of plate tectonics from a pre-plate tectonics regime requires both the initiation of subduction and the development of nascent subduction zones into long-lived contiguous features. Subduction itself has been shown to be sensitive to system parameters such as thermal state and the specific rheology. While generally it has been shown that cold-interior high-Rayleigh-number convection (such as on the Earth today) favours plates and subduction, due to the ability of the interior stresses to couple with the lid, a given system may or may not have plate tectonics depending on its initial conditions. This has led to the idea that there is a strong history dependence to tectonic evolution—and the details of tectonic transitions, including whether they even occur, may depend on the early history of a planet. However, intrinsic convective stresses are not the only dynamic drivers of early planetary evolution. Early planetary geological evolution is dominated by volcanic processes and impacting. These have rarely been considered in thermal evolution models. Recent models exploring the details of plate tectonic initiation have explored the effect of strong thermal plumes or large impacts on surface tectonism, and found that these ‘primary drivers’ can initiate subduction, and, in some cases, over-ride the initial state of the planet. The corollary of this, of course, is that, in the absence of such ongoing drivers, existing or incipient subduction systems under early Earth conditions might fail. The only detailed planetary record we have of this development comes from Earth, and is restricted by the limited geological record of its earliest history. Many recent estimates have suggested an origin of plate tectonics at approximately 3.0 Ga, inferring a monotonically increasing transition from pre-plates, through subduction initiation, to continuous subduction and a modern plate tectonic regime around that time. However, both numerical modelling and the geological record itself suggest a strong nonlinearity in the dynamics of the transition, and it has been noted that the early history of Archaean greenstone belts and trondhjemite–tonalite–granodiorite record many instances of failed subduction. Here, we explore the history of subduction failure on the early Earth, and couple these with insights from numerical models of the geodynamic regime at the time. This article is part of a discussion meeting issue ‘Earth dynamics and the development of plate tectonics'.

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Section: (D) Greenstones: a Failure To Launchsupporting

confidence: 57%

Section: (D) Greenstones: a Failure To Launchmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The inception of plate tectonics: a record of failure

O’Neill¹,

Turner²,

Rushmer³

2018

Phil. Trans. R. Soc. A.

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“…(a,b) Th/Yb vs. Nb/Yb plot (after Pearce, ; Smithies et al, ) showing the array for Sargur Group and Dharwar Supergroup komatiites extending from non‐arc NMORB‐EMORB‐OIB mantle array to arc regime substantiating the role of a subduction‐influenced sub‐cratonic lithospheric mantle [Colour figure can be viewed at wileyonlinelibrary.com]…”

Section: Discussionmentioning

confidence: 99%

“…(a,b) Th/Yb vs. Nb/Yb plot (afterPearce, 2008;Smithies et al, 2018) showing the array for Sargur Group and Dharwar Supergroup komatiites extending from nonarc NMORB-EMORB-OIB mantle array to arc regime substantiating the role of a subduction-influenced sub-cratonic lithospheric mantle [Colour figure can be viewed at wileyonlinelibrary.com] primordial hydrated oceanic crust forming Archean cratonic mantle roots (ACMR) beneath Dharwar Craton that was tapped by Mesoarchean and Neoarchean mantle plumes.5 | CONCLUSIONS• Komatiites from temporally distinct Sargur Group and Dharwar Supergroup greenstone belts of the Dharwar Craton are characterized by Al-depleted and Al-undepleted compositions analogous to the Barberton-and Munro-type counterparts.• The MgO, Ni, Co, and Cr concentrations reflect primitive, undifferentiated nature of precursor melts, whereas HFSE and REE chemistry corroborates high-degree (30-50%) partial melting of mantle with prominent role of majorite garnet and perovskite in the generation of komatiitic melts. Both majorite and perosvkite were stable residual phases in the mantle restite and also entered into the melt structure during partial melting.• The Al-depleted komatiites were formed at a greater depth(~13 GPa) by equilibrium melting leaving a garnet-bearing residue where the buoyant komatiitic melt segregated and accumulated in the peridotite mantle source and subsequently escaped with progressive decrease in pressure in the ascending plume.…”

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confidence: 99%

An appraisal of geochemical signatures of komatiites from the greenstone belts of Dharwar Craton, India: Implications for temporal transition and Archean upper mantle hydration

2019

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Archean ultramafic–mafic magmatism associated with dynamic mantle melting processes represents an integral part of crustal evolution and continental growth. Archean mantle plumes and their high temperature derivatives in komatiitic magmas provide a cornerstone in understanding the thermal and chemical evolution of the early Earth and its mantle. In this study, we evaluate the geochemical characteristics of the temporally distinct Sargur Group and Dharwar Supergroup greenstone belts of Dharwar Craton in southern India. The komatiites associated with these greenstone belts are characterized by Al‐depleted and Al‐undepleted compositions. Their MgO, Ni, Co, and Cr concentrations reflect primitive, undifferentiated nature of precursor melts, whereas the HFSE and REE chemistry corroborates high‐degree (30–50%) partial melting of mantle with prominent role of majorite garnet and perovskite in the generation of komatiitic melts. The Al‐depleted komatiites were formed at a greater depth (~13 GPa) by equilibrium melting leaving a garnet‐bearing residue. The resultant komatiitic melt retained buoyancy under extreme pressure and high temperature conditions, segregated and accumulated in the ambient peridotite mantle source and subsequently escaped with progressive decrease in pressure in the ascending plume. The Al‐undepleted and relatively rare Al‐enriched komatiites were derived by fractional melting at intermediate to shallow depths after the discharge of a large proportion of melt ensued by the collapse and entrance of residual garnet into the melt phase. The Mesoarchean–Neoarchean Dharwar komatiites provide evidence for heterogeneous, hydrated Archean upper mantle trapped by ascending mantle plumes. The non‐plume, arc‐related signatures invoke contributions from (a) sub‐cratonic lithospheric mantle roots influenced by ancient subduction events and (b) hydrated Archean upper mantle. The Sargur Group and Dharwar Supergroup komatiites record a distinct temporal transition and geochemical heterogeneity in the Archean mantle beneath the Dharwar Craton and can be attributed to Archean upper mantle hydration by flat slab subduction of >3.3 Ga oceanic crust at shallow level with vestiges of primordial oceanic crust forming deep cratonic mantle roots beneath the Dharwar Craton. The temporal transition towards mantle hydration beneath Dharwar Craton during the Mesoarchean can be correlated with the onset of subduction‐driven plate tectonics and ocean–crust–mantle interactions.

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Neoarchean suprasubduction zone magmatism in the Sonakhan greenstone belt, Bastar Craton, India: Implications for subduction initiation and melt extraction

et al. 2018

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The Neoarchean Sonakhan greenstone belt (SGB) in the north‐eastern Bastar Craton is mainly composed of an association of pillowed and massive tholeiitic basalts emplaced within an intraoceanic environment. Two types of ultrabasic rocks were identified and are designated as TH‐1 and TH‐2 on the basis of geochemical parameters. Both sample suites exhibit depletion of HFSE with reference to LILE and LREE, LREE/HFSE ratios, and negative Nb–Ta–Ti anomalies in the primitive mantle‐normalized multi‐element diagrams. The geochemical characters of TH‐1 and TH‐2 are consistent with Island arc tholeiites (IAT) and boninite‐like rocks of both Archean and Phanerozoic terranes. Mineral chemistry of clinopyroxenes from both volcanic suites indicate an oceanic arc affinity. The chromite chemistry indicate its derivation from a boninite‐like magma in a suprasubduction zone (SSZ) environment. Trace element modelling depicts that source depletion with significant influence of fluids derived from the subducting oceanic slab collectively controlled the trace element inventory of the mantle wedge, which result to the higher abundance of LREE and LILE compared to HREE and HFSE. The occurrence of lower basalt sequence followed by IAT and boninite‐like rocks in the SGB define a magmatic evolution which is comparable to the Phanerozoic ophiolite suites that exhibit subduction initiation prior to forearc rifting and suprasubduction zone magmatism. The subduction initiation in the intraoceanic lithosphere and the initial decompression melting followed by the upwelling of the MORB‐related magmas were attributed to the formation of the lower pillow basalts. Dehydration of the subducting plate and the melt extraction processes in the hydrous lherzolite mantle wedge account for the formation of TH‐1. Subsequent depletion and significant modification of a more refractory harzburgite source by the slab‐derived fluids generated the TH‐2 rocks. The compositionally diverse magmatic imprints with IAT and boninite affinity in the SGB indicate the significance of episodic melt extraction processes, dehydration of the subducting plate, and hydrous fluxing in SSZ tectonic setting.

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Two distinct origins for Archean greenstone belts

Cited by 139 publications

References 47 publications

The inception of plate tectonics: a record of failure

The inception of plate tectonics: a record of failure

An appraisal of geochemical signatures of komatiites from the greenstone belts of Dharwar Craton, India: Implications for temporal transition and Archean upper mantle hydration

Neoarchean suprasubduction zone magmatism in the Sonakhan greenstone belt, Bastar Craton, India: Implications for subduction initiation and melt extraction

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