Age constraints on the tectonothermal evolution of the Selwyn Zone, Eastern Fold Belt, Mount Isa Inlier

Antipodean fugitive terranes in southern Laurentia: How Proterozoic Australia built the American West

“…Co-location of the arc and backarc assemblages of southern Laurentia inboard of the same west-dipping subduction zone that formed the backarc basins of Paleoproterozoic eastern Australia-Antarctica provides answers to two interrelated and fundamental questions: 1) the remarkably similar timing and periodicity of events in two now widely separated continents, and 2) the whereabouts of the magmatic arc that formed contemporaneously with backarc extension from 1800 to 1655 Ma along the Australian-Antarctic margin but which appears to no longer reside in either Australia or Antarctica. Similarities in timing might alternatively be explained as the result of far-field forces operating at plate scale, but this argument is increasingly difficult to sustain in light of other aspects of the shared geology, including matching early intrusive-related low pressure-high temperature metamorphism and superposed anticlockwise pressure-temperature-time paths consistent with periodic crustal thickening followed by extensional exhumation and isobaric cooling (Boger and Hansen, 2004;Grambling et al, 1989;Pourteau et al, 2018;Rubenach et al, 2008). A more likely scenario is that the Laurentian provinces represent the more outboard and distal component of the same arc-backarc system that developed along the Australian-Antarctic margin from 1800 to 1655 Ma (Fig.…”

“…These events make up part of the Riversleigh Tectonic Event (Withnall and Hutton, 2013) and were likely accompanied by crustal thickening as evidenced by the local preservation of relict higher pressure mineral assemblages yielding ca. 1650 metamorphic monazite ages (Abu Sharib, 2012;McFarlane and Frost, 2009;Rubenach et al, 2008). These ages have been reported from both the Calvert Superbasin and lower Willyama Supergroup and in the eastern Mount Isa region (Soldiers Cap Group) derive from rocks in which kyanite and garnet overprint an earlier-formed layer-parallel fabric thought to be primarily of extensional origin (Abu Sharib, 2012).…”

Hydrothermal mineral alteration patterns in the Mount Isa Inlier revealed by airborne hyperspectral data

“…Alteration and deformation took place in several stages due to the prolonged tectonothermal evolution of the Mount Isa Inlier (Rubenach et al 2008). Two major fault systems are located in the area The main lithologies in the northern Cloncurry District (Figure 2) comprise the Mount Norna (finegrained quartzite, metamorphosed greywacke, siltstone, chert, limestone) and Llewellyn Creek Formations (pelitic schist with garnet, staurolite and andalusite; phyllite, metagreywacke, quartzite and amphibolite) and interlayered amphibolites, metabasalts and metadolerites.…”

“…The peraluminous Gin Creek Granite consists of mainly non-foliated, partly porphyritic biotite granites and weakly foliated tourmaline-muscovite leucogranites (Blake 1987), which were emplaced during the Wongan event (1750-1730 Ma). The high potassic Mt Dore Granite (1516 + 10 Ma, Pollard & McNaughton 1997) is a non-foliated, partly porphyritic, biotite and hornblende-biotite granite with minor microgranites, aplites and pegmatites (Blake 1987) that is part of the Williams-Naraku Suite, which intruded after the Isan peak metamorphism (Rubenach et al 2008). The high K-content, typical for granitoids of the Williams-Naraku Suite (Mark & Foster 2000), can not only be detected with radiometric images, but also by using the white mica products derived from hyperspectral data (Figure 7, Table 2).…”

Hot lithosphere at Mount Isa: implications for Proterozoic tectonics and mineralisation

“…The Barramundi orogeny was followed by repeated crustal extension accompanied by igneous and volcanic activity and sedimentation of the Guide, Myally and Quilalar supersequences into partially superposed continental basins (Betts et al 2006;Neumann et al 2009; Figure 1). Basin formation ended with the Isan orogeny, which peaked at 1600-1580 Ma (Rubenach 1992;Rubenach et al 2008), and was accompanied in its late stages by widespread crustal melting in the eastern part of the Inlier (Page & Sun 1998;Wyborn 1998;Mark 2001). Granitic rocks in the Mount Isa Inlier, both those intruded during extension events (Kalkadoon, Big Toby, Ewen, Burstall and Wonga suites; Figure 2) and those intruded during the Isan orogeny (Williams-Naraku suite; Figure 2), are highly enriched in radioactive isotopes of K, U and Th.…”