| Autor: |
Partin, Camille A., McDonald, Brayden S., McConnell, Michael, Thrane, Kristine, Graham Pearson, D., Sarkar, Chiranjeeb, Luo, Yan, Stern, Richard A. |
| Zdroj: |
Gondwana Research; Oct2024, Vol. 134, p222-244, 23p |
| Abstrakt: |
[Display omitted] • We present new zircon U-Pb, Hf, O isotopes from the Paleoproterozoic Karrat Group. • With provenance analysis of Karrat Group and Rinkian fold belt supracrustal rocks. • Zircon Hf isotopes identify new, abundant ca. 2.15–1.9 Ga juvenile magmatism. • Karrat Group sourced dominantly from orogenies involving the Rae craton. We use zircon U-Pb, Hf and O isotopes to constrain the depositional ages and provenance of metasedimentary rocks of the Paleoproterozoic Karrat Group of West Greenland and to understand the tectonic processes leading to basin development on the eastern Rae craton. An older supracrustal assemblage (Qeqertarssuaq complex) deposited after ca. 2.6 Ga is separated by an unconformity with a younger supracrustal assemblage (the Karrat Group). The Qaarsukassak Formation at the base of the Karrat Group was deposited after ca. 2.0 Ga, with dominantly Archean age modes. The youngest siliciclastic rocks (Nûkavsak and Mârmorilik formations) in the Karrat Group have maximum depositional ages ranging from ca. 1980 to 1950 to 1900 Ma and contain dominant detrital zircon age modes between ca. 2.50 and 1.93 Ga. A ca. 1.92 Ga supracrustal assemblage referred to as the northern domain (Karrat Group, sensu lato) is geographically separated from the Karrat Group (sensu stricto) by the Prøven igneous complex. The stratigraphy and detrital zircon profiles are compared to broadly coeval sedimentary units on the Rae craton and a unifying model of their deposition is presented. The Rae craton is the dominant detritus source; initially these sources were mostly local, changing to a mix of local and distal sources including the western Rae craton. The tectonic setting of the Karrat basin transitioned from extensional to convergent to collisional during its basin evolution, reflecting Wilson cycle phases within an epeiric sea. Accordingly, zircon Hf isotopes in our dataset track the evolution of the opening and closing of the Manikewan Ocean. Detrital zircon Hf isotopes in our dataset reveal a greater proportion of juvenile detritus (especially ca. 2.15–1.95 Ga) than is known from the currently exposed crustal record, pointing to the importance of the detrital zircon record for understanding Paleoproterozoic crustal and tectonic evolution. [ABSTRACT FROM AUTHOR] |
| Databáze: |
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