The Howards Basalt forms a minor mafic unit in the basal Lynchford Member of the Cambrian Tyndall Group. The unit is andesitic in character, and occurs most frequently as a monomictic breccia, strongly altered by chlorite, sericite and haematite. The unit was formed by the eruption of lava both explosively and effusively, in an extensional and subaqueous environment, to produce five main facies. The Howards Basalt can be geochemically correlated with the Suite ill rocks of the Mount Read Volcanics, which include the high K Que-Hellyer footwall volcanic rocks, and the shoshonitic Lynch Creek Basalt. The Howards Basalt occurs on the Comstock - Mt Lyell prospective horizon, on the same stratigraphic horizon as the Henty deposit. It is also thought to have formed in a similar fashion to the Spillway Basalt, which occupies another favourable horizon. The mode of emplacement of the Howards Basalt unit may have been conducive to mineralisation.
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