Paleomagnetic testing of the Lachlan Orocline hypothesis: Overprinting of remanence in Paleozoic rocks of the Lachlan Orogen in southeast Australia

Paleomagnetic studies in the Lachlan Orogen have indicated rotation of elements within it, but evidence for is limited and has significant statistical uncertainty. This study presents a detailed paleomagnetic investigation, assisted by X-ray analysis magnetic mineralogy middle Cambrian to lower Silurian sedimentary igneous rocks Victoria New South Wales. Four demagnetisation behaviours (types A, B, C D) been recognised. Type A characterised single component, resulting an approximately linear path over magnetite unblocking temperature range. B specimens exhibit slow progressive wide range, with clustering demagnetised directions above Curie temperature, indicating hematite. Behaviour also directions, this extends wider Samples behaviour D show noisy non-informative demagnetisation, very low stability. Hysteresis data confirm that samples high coercivities remain unsaturated 300 mT. Mineral liberation selected indicates presence iron oxides, magnetite, titanomagnetite, botryoidal hematite hydroxides. Only three sites yielded type primary magnetisation, poorly defined pole from Dookie Volcanics on central limb orocline, which does match previous result same district. Two paleopoles, Tabberabbera Zone Rockley Volcanics, plot confidence limit poles defining late Early Devonian Australian apparent polar wander path. These other representing overprints around margins interpreted be alteration mineralisation produced fluids driven tectonic compression during events Bindian (420–410 Ma) or early Tabberabberan (405–380 orogenies.KEY POINTSPaleomagnetic techniques used test Orocline southeast Australia.Results suggest original remanence obscured owing post-deformation overprint.This overprint widespread associated deformation Bindian/Tabberabberan orogenic events.