Zircons from the Wambidgee Serpentinite Belt, southern Lachlan Orogen: evidence for oceanic crust at the Cambrian–Ordovician boundary

This is the authors' abstract. We don't add key points for this paper.

E. A. Belousovaab* , I. T. Grahamc , R. A. Glena , W. L. Griffina & L. Martind a ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC National Key Centre, Department of Earth and Environmental Sciences, Macquarie University, Sydney, Australiab Department of Resources, Geological Survey of Queensland, Brisbane, Australiac Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of NSW, Sydney, Australiad Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Crawley, AustraliaEditorial handling: Chris FergussonSupplemental data for this article are available online at https://doi.org/10.1080/08120099.2021.1981441CONTACT Elena Belousova elena.belousova@mq.edu.au ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC National Key Centre, Department of Earth and Environmental Sciences, Macquarie University, Sydney, NSW 2109, AustraliaAbstractOphiolitic rocks of the Lachlan Orogen are important because they can provide key information used to refine existing tectonic models for the orogen. This study focuses on the serpentinite belts within the greater Tumut region of the Lachlan Orogen in southeastern Australia. U–Pb, Lu–Hf, O isotopic and trace-element data collected on zircons from a plagiogranite of the Wambidgee Serpentinite Belt are consistent with their crystallisation from mantle-derived melts. Their juvenile Hf-isotope compositions, with εHf ranging from +7 to +14, and δ18O values ranging from 4.35 to 5.07‰, are close to typical mantle values and clearly within the range defined for zircons from plagiogranites of ophiolitic complexes worldwide. When combined with zircon data available for the Coolac Serpentinite and recent petrogenetic modelling for the Coolac Serpentinite Belt, a new U–Pb age of 486 ± 3 Ma of the Wambidgee zircons constrains the age of formation of oceanic lithosphere in the greater Tumut region to Cambro-Ordovician.KEY POINTSAn age of 486 ± 3 Ma is reported for zircons from plagiogranite of the Wambidgee Serpentinite Belt in the Tumut region, southern Lachlan Orogen.We tentatively conclude that all serpentinite belts of the Tumut region may be of the same age, at the Cambrian–Ordovician boundary.This Cambro-Ordovician age provides the best estimate for oceanic crust formation in the greater Tumut region.