An isotopic perspective on growth and differentiation of Proterozoic orogenic crust: From subduction magmatism to cratonization

• Published in: Lithos Vol. 268-271; pp. 76 - 86
• Main Authors: Johnson, Simon P., Korhonen, Fawna J., Kirkland, Christopher L., Cliff, John B., Belousova, Elena A., Sheppard, Stephen
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01.01.2017
• Subjects: Capricorn Orogen; Cratonization; Crustal differentiation; Proterozoic orogenic crust; Zircon-Hf isotopes; Zircon-O isotopes; Proterozoic orogenic crust; Capricorn Orogen; Zircon-O isotopes; Zircon-Hf isotopes; Crustal differentiation; Cratonization
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2016.11.003

The in situ chemical differentiation of continental crust ultimately leads to the long-term stability of the continents. This process, more commonly known as ‘cratonization’, is driven by deep crustal melting with the transfer of those melts to shallower regions resulting in a strongly chemically stratified crust, with a refractory, dehydrated lower portion overlain by a complementary enriched upper portion. Since the lower to mid portions of continental crust are rarely exposed, investigation of the cratonization process must be through indirect methods. In this study we use in situ Hf and O isotope compositions of both magmatic and inherited zircons from several felsic magmatic suites in the Capricorn Orogen of Western Australia to highlight the differentiation history (i.e. cratonization) of this portion of late Archean to Proterozoic orogenic crust. The Capricorn Orogen shows a distinct tectonomagmatic history that evolves from an active continental margin through to intracratonic reworking, ultimately leading to thermally stable crust that responds similarly to the bounding Archean Pilbara and Yilgarn Cratons. The majority of magmatic zircons from the main magmatic cycles have Hf isotopic compositions that are generally more evolved than CHUR, forming vertical arrays that extend to moderately radiogenic compositions. Complimentary O isotope data, also show a significant variation in composition. However, combined, these data define not only the source components from which the magmas were derived, but also a range of physio-chemical processes that operated during magma transport and emplacement. These data also identify a previously unknown crustal reservoir in the Capricorn Orogen. •Crustal growth and differentiation processes (‘cratonization’) highlighted by in situ zircon Hf and O isotopes.•Zircon Hf and O isotopes reflect multi-component sources and shallow crustal processes associated with magma emplacement.•Identified previously unknown crustal reservoir in the Capricorn Orogen.•Crustal differentiation associated with an increase in the Th/U ratio of magmatic zircon.•Cratonization process may lead to shallow parts of the crust more susceptible to reworking.