Geology of the Henty Fault Wedge, Western Tasmania

The Henty Fault Wedge is a misfit slice of Cambrian lithologies which have been fault emplaced into the middle to late Cambrian Mt Read Volcanics. The Henty Fault Wedge has an exposed area of 30km\\(^2\\) and is located midway between Queenstown and Rosebery in western Tasmania (Fig 1). Two and possibly three fault juxtaposed structural domains occur within the wedge. The combined domains comprise six lithological associations, two tholeiitic volcanic/intrusive suites (Henty Valley and Ewart Creek Track Sequences), three calc-alkaline suites (Henty Adits, Halls Rivulet Track and Quartz phyric rhyolites) and an ophiolite complex. Igneous rocks are predominantly basaltic to andesitic in composition. Metamorphic grade within the fault wedge is predominantly prehnite pumpellyite facies, with greenschist facies rocks only recognized in gabbros in the ophiolite complex. Lithological and geochemical equivalents of the Henty Fault Wedge associations in western Tasmania are investigated. It is concluded that correlates of the Crimson Creek Formation and Mt Read Volcanics exist. The ophiolite complex is LREE and Zr enriched compared to other Tasmanian ultramafics; and andesites and tonalites within the complex have calc-alkaline affinities. The South Henty Fault is the bounding structure to the wedge in the south east, and is interpreted to be the southern continuation of the Henty Fault, a major structure in western Tasmania. The bounding structure to the west is the North Henty Fault, a Devonian structure which is interpreted to combine with the Rosebery Fault forming a north plunging thrust sole to a positive flower or pop up structure.