A non-zircon Hf isotope record in Archean black shales from the Pilbara craton confirms changing crustal dynamics ca. 3 Ga ago

Nebel-Jacobsen, Yona; Nebel, Oliver; Wille, Martin; Cawood, Peter A. (2018). A non-zircon Hf isotope record in Archean black shales from the Pilbara craton confirms changing crustal dynamics ca. 3 Ga ago. Scientific Reports, 8(1) Nature Publishing Group 10.1038/s41598-018-19397-9

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Plate tectonics and associated subduction are unique to the Earth. Studies of Archean rocks show significant changes in composition and structural style around 3.0 to 2.5 Ga that are related to changing tectonic regime, possibly associated with the onset of subduction. Whole rock Hf isotope systematics of black shales from the Australian Pilbara craton, selected to exclude detrital zircon components, are employed to evaluate the evolution of the Archean crust. This approach avoids limitations of Hf-in-zircon analyses, which only provide input from rocks of sufficient Zr-concentration, and therefore usually represent domains that already underwent a degree of differentiation. In this study, we demonstrate the applicability of this method through analysis of shales that range in age from 3.5 to 2.8 Ga, and serve as representatives of their crustal sources through time. Their Hf isotopic compositions show a trend from strongly positive εHfinitial values for the oldest samples, to strongly negative values for the younger samples, indicating a shift from juvenile to differentiated material. These results confirm a significant change in the character of the source region of the black shales by 3 Ga, consistent with models invoking a change in global dynamics from crustal growth towards crustal reworking around this time.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Wille, Martin

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

2045-2322

Publisher:

Nature Publishing Group

Language:

English

Submitter:

Martin Wille

Date Deposited:

16 Oct 2018 11:23

Last Modified:

10 Mar 2021 04:44

Publisher DOI:

10.1038/s41598-018-19397-9

BORIS DOI:

10.7892/boris.120487

URI:

https://boris.unibe.ch/id/eprint/120487

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