Provenance and tectonic development of the late Archaean Gawler Craton, Australia; U-Pb zircon, geochemical and Sm-Nd isotopic implications

Integrated Sensitive High Mass Resolution Ion Microprobe (SHRIMP) U-Pb zircon, geochemical and Sm-Nd isotopic data from the late Archaean Gawler Craton, southern Australia, constrain major basin-forming and magmatic processes to the interval 2560-2500 Ma. This terrane represents a convergent margin associated with the second half of a full global Wilson cycle, during which continental fragments formed between 2780 and 2590 Ma amalgamated with younger cratons, perhaps forming the Earth's first supercontinent. Metasedimentary rocks in the central and southern Gawler Craton deposited between 2535 and 2500 Ma, have dominant detrital SHRIMP U-Pb zircon ages, geochemical and ε<inf>Nd</inf> signatures which reflect input from predominantly felsic, juvenile to moderately evolved late Archaean crust. Geochemical patterns in ca. 2560-2500 Ma felsic to intermediate igneous lithologies that in part were produced during on-going basin development, suggest affinities with an arc-like environment, and have a range of ε<inf>Nd</inf> values that indicate variable crustal contamination of primitive arc components. However, approximately coeval komatiites have geochemical and ε<inf>Nd</inf> signatures consistent with a mantle-plume origin. We envisage a tectonothermal regime for development of the late Archaean Gawler Craton that reflects interaction between a convergent margin and mantle-plume, in which sedimentary deposition occurred during active basin development in a back-arc or arc-rift setting. Basin formation and associated magmatism was terminated by regional granulite grade metamorphism and crustal thickening during the ca. 2500-2400 Ma Sleafordian Orogeny, which was proceed by ∼400 Ma of tectonic quiescence. This suggests that the Sleafordian Orogeny was driven by collision between continental components, leading to the formation of a continental interior. While the late Archaean Gawler Craton is younger than prodigious late Archaean metallogenic provinces associated with the first half of a full global Wilson cycle (ca. 2780-2590 Ma), there are important lithological and tectonic similarities to those mineralized systems. © 2005 Elsevier B.V. All rights reserved.

Greg Swain, A. Woodhouse, M. Hand, K. Barovich, M. Schwarz and C.M. Fanning