Early differentiation of silicate soil recorded in Archean rocks of Isua (Greenland) : implications on mantle dynamics over time
type: Distribution
access URL: https://theses.hal.science/tel-00861891
format: HTML
issued: 2026-05-09T18:07:31.803717
modified: 2026-05-09T18:07:31.783506

test_moissonnage_selune
type: Agent

Early differentiation of silicate soil recorded in Archean rocks of Isua (Greenland) : implications on mantle dynamics over time
type: Dataset
contact point: Organization
  fn: CCSD
keyword: differenciation-precoce
keyword: theses
keyword: early-differentiation
keyword: silicate-earth
keyword: infoeu-reposemanticsdoctoralthesis
keyword: archean
keyword: archeen
keyword: 142nd
keyword: sdustusciences-of-the-universe-physicsearth-sciences
keyword: hadean
keyword: terre-silicatee
keyword: hadeen
keyword: isua
landing page: https://theses.hal.science/tel-00861891
description: The composition and the evolution of the silicate Earth during the Hadean-Eoarchean is widely debated and largely unknown due to the limited geological record. The first undisputable evidence for a very early differentiation of the mantle came from the extinct 146Sm-142Nd chronometer. The 142Nd excesses measured in 3.7 billion year (Ga) old rocks from Isua (Southwest Greenland) relative to modern terrestrial samples imply their derivation from a depleted mantle formed in the Hadean. We have studied 146,147Sm–142,143Nd and 176Lu–176Hf isotope systematics in 3.8 Ga, 3.7 Ga, 3.4 Ga and 3.3 Ga mantle-derived samples from different tectonic domains of the Isua region. This dataset covers ~ 500 million years of the early history of the Earth and revealed precious information about the compositional evolution and dynamics of the early Earth mantle. Combined Lu-Hf and Sm-Nd of the 3.7 Ga Isua samples revealed that these isotopic systematics were decoupled, suggesting a deep-seated source for the Isua lavas. We have further expanded the dataset and confirmed the 142Nd excesses in these rocks, implying that their source was depleted and differentiated during the first 100 Ma of Earth’s history. The differentiation event that created this early-depleted reservoir had to also form a complementary enriched component. We have found the first evidence for this reservoir recorded in the 3.4 Ga samples that yielded negative 142Nd anomalies. However, the 3.3 Ga analyzed samples showed no resolvable 142Nd anomalies compared to terrestrial Nd standards. This suggests that the Hadean heterogeneities were likely isolated for more than 1 Ga before being completely rehomogeneized by 3.3 Ga. The remixing by 3.3 Ga could have been achieved by subduction processes due to the onset of modern plate tectonics at ~3.2 Ga, as proposed by other recent studies.
identifier: NNT: 2012CLF22270
issued: 2026-05-09T18:07:31.795581
language: fr
modified: 2026-05-09T18:07:31.795585