Geology of the Yudnamutana area, northern Flinders Ranges, with special reference to the geochemistry of the mineralization and the Wooltana Volcanics

Abstract

The Wooltana Volcanics is a sequence of lavas having undergone intensive low grade alteration. The majority of lavas are now scapolitized biotite rich purple rocks in which the original igneous textures have been obliterated. Minor amygdaloidal lavas and rhyolites showing igneous textures remain. Geochemical and petrological evidence suggests that the majority of these lavas were originally basic lavas having undergone subsequent K and Fe metasomatism. The origin of the metasomatic solutions is considered to be the members of the "Younger Granite Suite" intruding the basement. Mineralization within the area is largely found in the Wywyana Formation and is associated with metasomatic solutions. Structures caused by the Delamerian Orogeny have localized the mineralization. Statistical evidence suggests that some of the mineralization may be due to subsequent enrichment of disseminated metasomatic copper, possibly augmented by disseminated copper from the Wooltana Volcanics.