It is 50 years since the landmark paper where Black et al. (1971) presented whole-rock Pb-Pb and Rb-Sr isotopic evidence for some rocks in Greenland surviving from Earth's first billion years; the ≥ 3700 Ma Amîtsoq gneisses. This overturned ideas prevalent at that time that the young Earth was far too violent for such ancient rocks to survive. In the following few years it emerged how ‘normal’ this early Earth appeared to be, with a retained hydrosphere (oceans) by 3700 Ma and ‘continental’ crust dominated by rather normal granitic sensu lato rocks. By several decades ago this led to a vision of Eoarchean lithosphere development being controlled by a geodynamic regime with definite similarities to that in the Phanerozoic, particularly with evidence for lateral lithosphere movement (mobile lid) such as exemplified by arc-like magmatism and Barrovian metamorphism (the latter requiring tectonic crustal thickening). However, the literature in recent years is increasingly em
Ambasadorul Franţei în Statele Unite s-a întors miercuri la Washington, la două săptămâni după declanşarea unei crize fără precedent între cei doi apropiaţi aliaţi transatlantici, informează AFP