The Majorqaq Belt: A record of Neoarchaean orogenesis during final assembly of the North Atlantic Craton, southern West Greenland

摘要: Abstract Over the past 4.5 billion years (Ga) Earth has undergone a secular change in tectonic regimes. Archaean tectonics was markedly different process than observed today, involving hotter planet with thinner lithosphere, thicker oceanic crust, and smaller proto-continents. The transition to more modern type of plate required initiation subduction lithosphere. onset Meso- Neoarchaean (ca. 3.2 2.5 Ga) is shown by geochemical signatures indicative crustal recycling petrologic evidence tectonically driven thickening continental crust. This recorded rock record North Atlantic Craton, which preserves history crust formation through terrane accretion collision blocks. Here we present petrologic, chronologic, chemical geophysical from Majorqaq Belt, ~ 100 km wide east–west striking zone, defined high gravity anomaly, voluminous metasedimentary units, olivine-rich ultramafic enclaves, anomalously K2O, Ni, MgO stream-sediment chemistry. We use 207Pb/206Pb zircon LA-ICP-MS age 2.557 ± 0.005 Ga (2σ) an upper-amphibolite facies metapelitic migmatite propose suturing Maniitsoq block Craton. Ti-in-zircon temperatures zircon–garnet REE distribution coefficients constrain crystallisation 815–729 °C, at, or near solidus during leucosome crystallisation. Our data reveal clockwise P–T path high-pressure assemblage garnet–kyanite–plagioclase–rutile–biotite–quartz grew at apparent thermal gradient ~ 660 °C/GPa subduction-driven compression surface-derived sediments minimum-peak-pressure ~ 1.15 GPa ~ 760 °C followed growth gedrite–cordierite–sillimanite–ilmenite minimum-peak-temperature conditions ~ 810 °C ~ 0.94 GPa. evolution belt formed proto-North Craton following closure basin south-dipping subduction, providing potential source volatiles for ca. 2.55 Ga Qorqut granite complex situated ~ 150 km further southwards. These necessitate orogenesis indicate that active 2.56 Ga final assembly