Reply to Comment by A.P. Nutman et al. on "Tectonics of the Isua Supracrustal Belt 1: P‐T‐X‐d Constraints of a Poly‐Metamorphic Terrane" by A. Ramírez‐Salazar et al. and "Tectonics of the Isua Supracrustal Belt 2: Microstructures Reveal Distributed Strain in the Absence of Major Fault Structures" by J. Zuo et al. Issue 5 (5th May 2022)

• Record Type: Journal Article
• Authors: Ramírez‐Salazar, Anthony; Zuo, Jiawei; Müller, Thomas; Webb, A. Alexander G.; Sorger, Dominik; Piazolo, Sandra; Haproff, Peter; Harvey, Jason; Wang, Qin; Hauzenberger, Christoph; Wong, Tsz Kin
• Is Part Of: Tectonics. Volume 41:Issue 5(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-05
• Subjects: Archean tectonics -- Isua supracrustal belt -- heat‐pipe tectonics; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2021TC007148
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: Structural and metamorphic analyses from the works under discussion (Ramírez‐Salazar et al., 2021, https://doi.org/10.1029/2020tc006516 ; Zuo et al., 2021, https://doi.org/10.1029/2020tc006514 ) show that the Isua supracrustal rocks can be interpreted to record one single deformation and metamorphic event featuring quasi‐homogeneous deformation and amphibolite facies metamorphism, followed by late static retrogression or thermal event(s). Observed deformation and metamorphic records are consistent with three hypotheses: (a) they represent Neoarchean plate tectonic overprints following Eoarchean plate tectonic evolution (e.g., Nutman et al., 2022, https://doi.org/10.1029/2021TC007036 ); (b) they represent Eoarchean heat‐pipe and/or plate tectonic deformation that survived later tectonic event(s) (e.g., Ramírez‐Salazar et al., 2021, https://doi.org/10.1029/2020tc006516 ; Zuo et al., 2021, https://doi.org/10.1029/2020tc006514 ), and; (c) they represent one major Neoarchean tectonic event, such that the Isua supracrustal belt (ISB) records Eoarchean protolith‐related processes but does not record Eoarchean metamorphism nor deformation. While a heat‐pipe model for crustal formation is central to hypothesis 2, it is also a viable crustal formation mechanism for hypothesis 3 where the ISB would still form in a heat‐pipe setting in Eoarchean time, but the major deformation of the heat‐pipe lithosphere happened during Neoarchean time, probably by (proto‐)plate tectonic processes. If the data presented in Zuo et al. (2021), https://doi.org/10.1029/2020tc006514 and Ramírez‐Salazar et al. (2021), https://doi.org/10.1029/2020tc006516 only reflect Neoarchean histories, then these cannot be used to refute or support any Eoarchean geodynamic background for the formation of the ISB. Key Points: Neoarchean tectono‐metamorphism is viable and may be the only deformation event. It would likely involve (proto‐)plate tectonics All prograde metamorphic records can be interpreted as amphibolite facies Isua Eoarchean crustal formation is feasible within a heat‐pipe tectonic context