Regional zircon U-Pb geochronology for the Maniitsoq region, southwest Greenland

Abstract

Zircon U-Pb geochronology places high-temperature geological events into temporal context. Here, we present a comprehensive zircon U-Pb geochronology dataset for the Meso- to Neoarchean Maniitsoq region in southwest Greenland, which includes the Akia Terrane, Tuno Terrane, and the intervening Alanngua Complex. The magmatic and metamorphic processes recorded in these terranes straddle a key change-point in early Earth geodynamics. This dataset comprises zircon U-Pb ages for 121 samples, including 46 that are newly dated. A principal crystallization peak occurs across all three terranes at ca. 3000 Ma, with subordinate crystallization age peaks at 3200 Ma (Akia Terrane and Alanngua Complex only), 2720 Ma and 2540 Ma. Metamorphic age peaks occur at 2990 Ma, 2820–2700 Ma, 2670–2600 Ma and 2540 Ma. Except for one sample, all dated metamorphic zircon growth after the Neoarchean occurred in the Alanngua Complex or within 20 km of its boundaries. This U-Pb dataset provides an important resource for addressing Earth Science topics as diverse as crustal evolution, fluid–rock interaction and mineral deposit genesis.

Dating mylonitic overprinting of ancient rocks

“…Despite a slight skewness towards younger ages, the titanite U-Pb age distribution is broadly consistent with a single age component with only minor radiogenic-Pb loss or perhaps a slight closure temperature differential in the grain population. The dominant titanite U-Pb age of c. 2970 Ma is similar to the c. 3000 Ma zircon U-Pb magmatic crystallization age for Akia Terrane felsic gneisses 24 . Trace element patterns of this titanite are also characteristic of a magmatic genesis and the Zr concentration supports a magmatic crystallization temperature of ~770 °C.…”

“…The outcrop consists of variably sheared and intermingled tonalite, granodiorite, and diorite, with amphibolite boudins. A c. 568 Ma kimberlite dyke intrudes in close proximity to this outcrop and c. 3006 Ma dioritic gneisses have been dated 7 km west of this locality 24 . The sample comprises 43% plagioclase, 26% quartz, 18% K-feldspar, 8% biotite, 4% muscovite, and accessory minerals include apatite, augite, titanite, allanite, and calcite (Fig.…”

“…Trace element patterns of this titanite are also characteristic of a magmatic genesis and the Zr concentration supports a magmatic crystallization temperature of ~770 °C. Both the U-Pb systematics and REE compositional pattern point to magmatic titanite growth during the main regional magmatic emplacement event 24 , which dominated the isotopic memory of this mineral, with subsequent thermal conditions being unable to wholesale reset its U-Pb system.…”

Thermochronometry constraints on south West Greenland passive continental margin development

“…The latest major regional thermal and fluid event experienced by the Precambrian crystalline basement in the study area was metamorphic overprinting during the far field effects of the Nagssugtoqidian Orogeny at ca. 1.7 Ga revealed by apatite U-Pb geochronology 22 . During Phanerozoic times, the Precambrian basement in the Maniitsoq region was locally intruded by small magmatic bodies, including Proterozoic kimberlite dykes dated at 553-568 Ma 23,24 , Jurassic carbonatite complexes, monchiquite dykes (ca.…”

Supplemental Material: Did transit through the galactic spiral arms seed crust production on the early Earth?

“…table 5 and is also available through the public geoscience repository "Geoview" at http://www.dmp.wa.gov.au/geochron/ see Lu et al, (2021). Extended U-Pb data tables for all investigated NAC and Pilbara samples are available in Geological Survey of Western Australia, (2020) and Olierook et al, (2021).…”