Carboniferous palaeomagnetism of the Werrie Block, northwestern Tamworth Belt, and the New England pole path

Palaeomagnetic, rock-magnetic and magnetic-fabric results are presented for Carboniferous and Lower Permian volcanic and volcaniclastic rocks (Merlewood Formation, Currabubula Formation, Werrie Basalt and Boggabri Volcanics), mainly from the Werrie Block of the northwestern Tamworth Belt, southern New England Orogen. Detailed thermal demagnetisation results (91 sites, 998 samples) show two groups of magnetic components with low (<400°C; LT) and high (500-700°C; HT) unblocking temperature ranges. Rock magnetic tests indicate the HT components to reside in magnetite, with single or pseudo-single domain and multidomain characteristics, and in hematite. Detailed demagnetisation up to 700°C demonstrates subtle directional differences between primary components, optimally cleaned and derived from the magnetite-hematite carrier (HT-P2), and pseudo-components, incompletely cleaned and derived from the mainly magnetite carrier (HT-P1). Directional results evidence three phases of magnetic overprinting which arose from: (i) a possible Middle-Late Cenozoic regional weathering event (LT); (ii) fluid movements associated with the Permo-Triassic Hunter-Bowen Orogeny (HT); and (iii) formation of the Bowen-Gunnedah-Sydney Basin system in the latest Carboniferous - Early Permian (HT). Magnetic fabric results show the K_max and K_min axes of the susceptibility anisotropy ellipsoids to better concentrate in stratigraphic than in geographical (in situ) coordinates, suggesting a primary depositional pattern. The prevailing north-south alignment of K_max axes changes to east-west towards the top of the Currabubula Formation. The sense of transport could not be established in absence of evidence for imbrication. Well-defined primary magnetisation components (HT-P2) have been determined for 39 of the 69 Currabubula Formation sites and for all sites of the Merlewood Formation (7), Werrie Basalt (9) and Boggabri Volcanics (6). Currabubula Formation site results have been combined into three mean-site results, all with positive fold tests at the 99% confidence level. They show good agreement with correlatable results from the northward adjacent Rocky Creek Block. Integration of the palaeomagnetic poles for the Currabubula Formation and a virtual geomagnetic pole for the Merlewood Formation with earlier determined Visean to Westphalian poles for the Rocky Creek Block outlines a Visean (Tournaisian?) to Stephanian pole path for the northwestern Tamworth Belt. Comparison with a preliminary pole path for the Rouchel and western Gresford Blocks shows no evidence for significant rotational deformation between the northwestern and southwestern Tamworth Belt. Comparison with the Northern Hastings Block indicates counterclockwise rotation of the latter relative to the northwestern Tamworth Belt over about 150°, in agreement with structural estimates.