Argon isotopic composition of Archaean atmosphere probes early Earth geodynamics

Pujol, Magali; Marty, Bernard; Burgess, R.; Turner, G.; Philippot, Pascal

doi:10.1038/nature12152

Cited by 109 publications

(106 citation statements)

References 37 publications

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“…6B; Cawood et al, 2013). It is equally striking that similar figures have also been estimated more recently, from the evolution of atmospheric 40 Ar/ 36 Ar through time (Pujol et al, 2013).…”

Section: Growth Of the Continental Crustsupporting

confidence: 66%

Continental growth and the crustal record

2013

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The continental crust is the archive of Earth history. The spatial and temporal distribution of the Earth's record of rock units and events is heterogeneous with distinctive peaks and troughs in the distribution of ages of igneous crystallization, metamorphism, continental margins and mineralization. This distribution reflects the different preservation potential of rocks generated in different tectonic settings, rather than fundamental pulses of activity, and the peaks of ages are linked to the timing of supercontinent assembly. In contrast there are other signals, such as the Sr isotope ratios of seawater, mantle temperatures, and redox conditions on the Earth, where the records are regarded as primary because they are not sensitive to the numbers of samples of different ages that have been analysed. New models based on the U-Pb, Hf and O isotope ratios of detrital zircons suggest that at least ~60-70% of the present volume of the continental crust had been generated by 3 Ga. The growth of continental crust was a continuous rather than an episodic process, but there was a marked decrease in the rate of crustal growth at ~3 Ga. This appears to have been linked to significant crustal recycling and the onset plate tectonics. The 60-70% of the present volume of the continental crust estimated to have been present at 3 Ga, contrasts markedly with the <10% of crust of that age apparently still preserved and it requires ongoing destruction (recycling) of early formed crust and subcontinental mantle lithosphere back into the mantle through processes such as subduction and delamination.

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Section: Growth Of the Continental Crustsupporting

confidence: 66%

Continental growth and the crustal record

2013

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“…Using compositional variations of mantle melts through time and rheological constraints of the present-day mantle, Labrosse and Jaupart (2007) postulated a temperature maximum of the Earth's mantle by about 3000 Ma, which they linked to the start of subduction-driven plate teconics involving oceanic plates similar in size to those of today's. While Pujol et al (2013) link unradiogenic 40 Ar/ 36 Ar ratios in <3500 Ma fluid inclusions from the Pilbara craton (Northwest Australia) to rapid crust extraction between 3500 and 2700 Ma, Shirey and Richardson (2011) found that the mineralogical composition of diamond inclusions changed from peridoditic to eclogitic lithologies at ca. 3000 Ma.…”

Section: The W Isotopic Evolution Of the Earth's Archean Mantlementioning

confidence: 98%

Tungsten isotope composition of the Acasta Gneiss Complex

Willbold

Mojzsis

Chen

et al. 2015

Earth and Planetary Science Letters

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Editor: B. Marty Keywords: Archean mantle crust late veneer tungsten isotopes Acasta Gneiss Complex High-precision tungsten ( 182 W/ 184 W) isotope measurements on well-characterised mafic and felsic samples of the ca. 3960 Ma Acasta Gneiss Complex (AGC; Northwest Territories, Canada) show radiogenic ε 182 W values between +0.06 to +0.15. Two ca. 3600 Ma felsic samples from this terrane have ε 182 W ∼ 0 and are the oldest samples so far documented to have a W isotopic composition indistinguishable from that of the modern mantle. The ε 182 W data are correlated with ε 142 Nd (Roth et al., 2014) and weattribute this variability to incomplete metamorphic homogenisation of the 3960 Ma protolith with more recent material in a 3370 Ma tectono-thermal event. Notably, the value of the positive ε 182 W anomalies seen in the 3960 Ma AGC samples that are least affected by metamorphic homogenisation is comparable to that observed in other early Archean rocks (Isua Supracrustal Belt, Greenland; Nuvvuagittuq Supracrustal Belt, Canada) and the late Archean Kostomuksha komatiites (Karelia). This demonstrates a globally constant signature. We infer that the presence of a pre-late veneer mantle represents the most straightforward interpretation of a uniform distribution of ε 182 W ∼ +0.15 value in Archean rocks of different ages. We show that such a notion is compatible with independent constraints from highly siderophile element abundances in mafic and ultra-mafic Archean mantle-derived rocks. The absence of anomalous ε 182 W and ε 142 Nd so far measured in samples younger than ca. 2800 Ma suggests progressive convective homogenisation of silicate reservoirs. The downward mixing of an upper mantle rich in late-delivered meteoritic material might account for these combined observations.

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“…3 correspond to the 9,366 successful combinations. The only fixed parameters were age of the Earth at 4.55 Ga (T 1 ), initial mantle μ 1 and κ 1 at 8.3 and 3.8 (26) (the μ 1 corresponds to the average of values listed by Asmerom and Jacobsen (26) after removal the two outliers), and T 2 of 3 Ga for the time at which large volumes of continental crust already existed (27,28). The unknown values are therefore μ 2 , κ 2 , μ 3 , κ 3 , and T 3 .…”

Section: Methodsmentioning

confidence: 99%

Sulfur and lead isotopic evidence of relic Archean sediments in the Pitcairn mantle plume

Delavault

Chauvel

Thomassot

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

109

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The isotopic diversity of oceanic island basalts (OIB) is usually attributed to the influence, in their sources, of ancient material recycled into the mantle, although the nature, age, and quantities of this material remain controversial. The unradiogenic Pb isotope signature of the enriched mantle I (EM I) source of basalts from, for example, Pitcairn or Walvis Ridge has been variously attributed to recycled pelagic sediments, lower continental crust, or recycled subcontinental lithosphere. Our study helps resolve this debate by showing that Pitcairn lavas contain sulfides whose sulfur isotopic compositions are affected by mass-independent fractionation (S-MIF down to Δ33S = −0.8), something which is thought to have occurred on Earth only before 2.45 Ga, constraining the youngest possible age of the EM I source component. With this independent age constraint and a Monte Carlo refinement modeling of lead isotopes, we place the likely Pitcairn source age at 2.5 Ga to 2.6 Ga. The Pb, Sr, Nd, and Hf isotopic mixing arrays show that the Archean EM I material was poor in trace elements, resembling Archean sediment. After subduction, this Archean sediment apparently remained stored in the deep Earth for billions of years before returning to the surface as Pitcairn´s characteristic EM I signature. The presence of negative S-MIF in the deep mantle may also help resolve the problem of an apparent deficit of negative Δ33S anomalies so far found in surface reservoirs.

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Argon isotopic composition of Archaean atmosphere probes early Earth geodynamics

Abstract: and crushing runs are similar is justified by the unique slope of the Fig. 1 correlation. 190Corrected step-heating data define several equations (one per temperature step) with two 191

Cited by 109 publications

References 37 publications

Continental growth and the crustal record

Continental growth and the crustal record

Tungsten isotope composition of the Acasta Gneiss Complex

Sulfur and lead isotopic evidence of relic Archean sediments in the Pitcairn mantle plume

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