The coupled Hf-Nd isotope record of the early Earth in the Pilbara Craton

Salerno, Ross; Vervoort, Jeffrey D.; Fisher, C. M.; Kemp, Anthony I.S.; Roberts, Nicolas

doi:10.1016/j.epsl.2021.117139

Cited by 23 publications

(19 citation statements)

References 56 publications

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“…Several distinct compositional plutons have been identified in the Corunna Downs, Mount Edgar, Muccan, Warrawagine, and Yilgalong Domes, and the intrusions are only moderately to weakly foliated. The granitic rocks from this Supersuite derived from the partial melting of either a juvenile mafic source [26,27] or an older granitic crust [46,[48][49][50]. Granitic rocks from the Cleland Supersuite intruded most domes of the EPT between 3.27 and 3.22 Ga.…”

Section: Geological Settingmentioning

confidence: 99%

“…Edgar Dome Granitoids. A number of models for the Archaean evolution of the Pilbara crust have been published, yet no consensus was reached on whether the mantle source of Pilbara granitoids was chondritic [26,27,32] or more depleted [33,34]. Our zircon Hf isotope data has potential to bring new perspectives to the current debate, and a summary plot that includes literature data is given in Figure 7.…”

Section: Chondritic or Depleted Mantle Source For The Mountmentioning

confidence: 99%

“…The existence of an early evolved crust implies the presence of a complementary depleted reservoir within the mantle, and there is an ongoing debate over the size and the rate of depletion of the depleted mantle (DM). Some authors have suggested that the mantle suffered a progressive depletion in incompatible elements due to crustal extraction from the Hadean (i.e., >4 Ga) [20][21][22][23], while others have proposed that early continental crust was essentially formed from a mantle with a broadly chondritic composition, and that mantle depletion started to be significant only from the Mesoarchaean [5,14,[24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

“…The EPT contains several plutonic bodies that range in age from 3.59 to 2.8 Ga [28][29][30][31][32] and which have classically been interpreted to derive from an ancient protocrust (>3.8 Ga) that was repeatedly reworked with limited input of juvenile mantle material [31,[33][34][35]. In contrast, recent lines of evidences have suggested that progressive juvenile additions have played a key role in the formation and evolution of the EPT crust [26,27,32].…”

Section: Introductionmentioning

confidence: 99%

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Evidence for Protracted Intracrustal Reworking of Palaeoarchaean Crust in the Pilbara Craton (Mount Edgar Dome, Western Australia)

et al. 2022

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~3.5-2.8 Ga granitoids from the Pilbara Craton in Western Australia are one of the most ancient and best-preserved records of early processes of continental crust generation. A number of recent studies have focused on the nature of the mantle source from which Pilbara granitoids derived, yet no consensus has been reached on whether the mantle was chondritic or depleted in the Eo/Palaeoarchaean. Here we present integrated whole-rock (major and trace elements) and zircon (U-Pb and Lu-Hf isotopes) data for 10 granitoids sampled across the Mount Edgar Dome, which recorded four main magmatic events between 3.47 and 3.23 Ga. Whole-rock major and trace element analyses suggest that the samples belong to two distinct petrogenetic groups. The first group is akin to the tonalite-trondhjemite-granodiorite (TTG) suite, representing highly fractionated magmas initially formed by partial melting of a basaltic crust. The second group, here classified as granites, is best interpreted by the remelting of a basaltic crust and the addition of more evolved material, and it is striking that TTG-like and granitic magmas occurred coevally in time and space. Overall, both groups were formed through intense intracrustal differentiation processes that lead to the loss of significant geochemical information about their original sources. High-precision Lu-Hf analyses in zircon allow to obtain such information and to trace back the isotopic composition of the Palaeoarchaean mantle. A clear change from superchondritic to subchondritic Hf isotope compositions is observed between 3.47 and 3.23 Ga. The superchondritic Hf isotope composition of the 3.47 Ga old granitoids substantiates derivation from a depleted mantle source that separated from the chondritic mantle prior to 3.8 Ga. The presence of ca. 3.5 Ga old inherited zircons in younger magmas suggests that crustal remelting processes were involved in their generation. We propose that all granitoids investigated in this study had their crustal sources originated from a single mantle–crust differentiation event that occurred at 3.50 Ga. This event resulted in the differentiation, from the same original mantle, of two distinct crustal reservoirs, i.e., a mafic reservoir with a 176Lu/177Hf ratio of 0.023, and a reservoir of intermediate/felsic composition ( 176Lu/ 177Hf=0.013). 3.32-3.31 Ga-old granitoids were produced by remelting of the mafic reservoir, whereas 3.43 and 3.23 Ga granitoids derived from the intermediate/felsic reservoir. Overall, our data suggest that protracted intracrustal remelting processes and differentiation have played a key role in the formation, evolution, and maturation of the building blocks of continents during the Palaeoarchaean.

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Section: Geological Settingmentioning

confidence: 99%

Section: Chondritic or Depleted Mantle Source For The Mountmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evidence for Protracted Intracrustal Reworking of Palaeoarchaean Crust in the Pilbara Craton (Mount Edgar Dome, Western Australia)

et al. 2022

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“…The zircon U-Pb/Hf and REE-rich minerals U-Pb/Sm-Nd isotope results obtained from the felsic igneous rocks from the Mt. Edgar Complex (Pilbara craton, Australia) showed that these phases can be coeval [67]. In this example, zircon, monazite, titanite and apatite from a Pilbara basement rock showed Paleoarchean ages and chondritic Hf and Nd initial compositions, i.e., indicative of no significantly depleted source mantle and no Hf-Nd decoupling at that time, in this area.…”

Section: Diachronous Redistribution Of Hf and Nd Isotopes In The Saglek Blockmentioning

confidence: 99%

Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane

et al. 2022

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In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic compositions to constrain the evolution of metamorphic rocks might then inadvertently skew geological interpretations towards one aspect or one moment of a rock’s history. Here, we present in-situ U–Pb/Sm–Nd isotope analyses of the apatite crystals extracted from two meta-igneous rocks exposed in the Saglek Block (North Atlantic craton, Canada), an Archean metamorphic terrane, with the aim of examining the various signatures and events that they record. The data are combined with published U–Pb/Hf/O isotope compositions of zircon extracted from the same hand-specimens. We found an offset of nearly ca. 1.5 Gyr between U-Pb ages derived from the oldest zircon cores and apatite U–Pb/Sm–Nd isotopic ages, and an offset of ca. 200 Ma between the youngest zircon metamorphic overgrowths and apatite. These differences in metamorphic ages recorded by zircon and apatite mean that the redistribution of Hf isotopes (largely hosted in zircon) and Nd isotopes (largely hosted in apatite within these rocks), were not synchronous at the hand-specimen scale (≤~0.001 m3). We propose that the diachronous redistribution of Hf and Nd isotopes and their parent isotopes was caused by the different PT conditions of growth equilibration between zircon and apatite during metamorphism. These findings document the latest metamorphic evolution of the Saglek Block, highlighting the role played by intra-crustal reworking during the late-Archean regional metamorphic event.

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The geochemical concept of a “Primitive Mantle”

Stracke

2025

Treatise on Geochemistry

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The coupled Hf-Nd isotope record of the early Earth in the Pilbara Craton

Cited by 23 publications

References 56 publications

Evidence for Protracted Intracrustal Reworking of Palaeoarchaean Crust in the Pilbara Craton (Mount Edgar Dome, Western Australia)

Evidence for Protracted Intracrustal Reworking of Palaeoarchaean Crust in the Pilbara Craton (Mount Edgar Dome, Western Australia)

Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane

The geochemical concept of a “Primitive Mantle”

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