Evidence for Hadean mafic intrusions in the Nuvvuagittuq Greenstone Belt, Canada.

Many questions remain regarding Earth's earliest crust owing to the rarity of Hadean (>4.03 billion-year-old) rocks and minerals. The Nuvvuagittuq Greenstone Belt (NGB) in Canada may be the only known remnant of Hadean crust, although its age is debated, ranging from ≥3.75 to 4.3 billion years old. Mafic intrusions within this belt were specifically sampled and analyzed to investigate the timing of their magmatic differentiation. Correlations between samarium/neodymium (Sm/Nd) and 143Nd/144Nd and 142Nd/144Nd ratios correspond to ages of 4157 ± 174 and 4196 − 81 + 53 million years for the long-lived 147Sm-143Nd and the short-lived 146Sm-142Nd systems, respectively. The age agreement between both extant and extinct radiogenic systems, in rocks related through igneous fractionation, is compelling evidence for preservation of Hadean rocks in the NGB, opening a rare window into Earth's earliest times. Editor's summary: Earth has a habit of renewing its crust through melting and recrystallization, thus erasing much of its early history. There are mineral fragments from the oldest eon, the Hadean, but there is little consensus on whether any intact, primordial crust still exists. Sole et al. revisited oceanic rocks from the Nuvvuagittuq Greenstone Belt in northeast Canada, comparing long- and short-lived samarium-neodymium isotope systems to determine when the rocks first crystallized. Their new tests point to an age of about 4.2 billion years, further evidence that a slice of Hadean crust may remain. —Angela Hessler [ABSTRACT FROM AUTHOR]