A legacy of Hadean silicate differentiation inferred from Hf isotopes in Eoarchean rocks of the Nuvvuagittuq supracrustal belt (Québec, Canada)

Protocrustal evolution of the Nuvvuagittuq Supracrustal Belt as determined by high precision zircon Lu–Hf and U–Pb isotope data

“…As the NSB is highly deformed (as is generally the case for Eoarchean rock complexes) and has gone through several cycles of high grade metamorphism (Cates and Mojzsis, 2007;David et al, 2009), obtaining robust and unambiguous geochronological and isotopic information unravelling the different aspects of its evolution have presented a challenge. In recent years there has been a debate on whether (some of) the gneisses of the NSB were actually crystallised in and incorporated into the crust in the Early Hadean (O'Neil et al, 2008 or whether these rocks were formed in the Eoarchean (Cates and Mojzsis, 2007;Cates et al, 2013;Guitreau et al, 2013) and rather sampled an enriched mantle source that had differentiated in the early Hadean as has been suggested for example for the Isua Supracrustal Belt (e.g. Rizo et al, 2011).…”

“…3.8 Ga to 4.4 Ga (e.g. O'Neil et al, 2012;Guitreau et al, 2013). Here we report new high precision U-Pb geochronological and coupled Lu-Hf isotope data from zircons that reveal the age of the NSB and provide new constraints on the source rocks to this piece of early crust.…”

Terrestrial aftermath of the Moon-forming impact

“…Within resolution, the ratio 142 Nd/ 144 Nd is constant over modern mid-ocean ridge and oceanic island models [56] [64]. In the model of Guitreau et al [64], the Hadean domain formed at approximately 4.51 Ga. We note that the absolute time of the Moon-forming impact is not well constrained, so we cannot provide precise absolute times from 142 Nd/ 144 Nd results either.…”

“…In the model of Guitreau et al [64], the Hadean domain formed at approximately 4.51 Ga. We note that the absolute time of the Moon-forming impact is not well constrained, so we cannot provide precise absolute times from 142 Nd/ 144 Nd results either. Avice & Marty [65] proposed that the impact occurred 40-50 Myr after the start of the Solar System, or approximately 4.52 Ga, from an analysis of xenon isotopes.…”

“…Rizo et al [58] associate 142 Nd/ 144 Nd variations in Archaean lavas with this process. Guitreau et al [64] also discussed the possibility that a mantle source of this type produced 142 Nd/ 144 Nd variation within early Archaean lavas from Québec. Jackson & Carlson [56] point out that partial crystallization of the mantle in the early Hadean could have formed 'hidden' low-Sm/Nd reservoirs, leaving the rest of the mantle with Sm/Nd approximately 6% higher than the probable meteorite source of the Earth.…”