ALLOPHANE AND OPAL SPELEOTHEMS FROM GRANITE CAVES IN SOUTHEAST QUEENSLAND

Abstract

Coralloidal and flowstone speleothems occur in two caves in the Stanthorpe Granite at Girraween National Park, south-east Queensland. The cave coral is found on the cave roofs and consists of banded opal-A with small mineral inclusions derived from the overlying granite. Coral from one cave conlains a small component of allophane. The flowstone occurs on the floor of one cave, and is composed of thinly banded allophane, which has an unusual composition characterisedby high levels of aluminium, phosphate and organic carbon. The allophane is precipitating only from water that has seeped through humus and soil. This is the first positive identification of allophane in speleothems, and also prov..