Arumpo bentonite/An emerging source of Australian bentonite

摘要

EXPLORATION in the early 1 990s for heavy minerals in the Murray Basin region of New South Wales provided the first indication of an extensive bentonite deposit at a location 90km north-west of the regional centre of Mildura. Arumpo Bentonite Pty Ltd has now developed a modern mining operation based on this deposit with a capacity of 30,000 tpa and opportunity for considerable expansion. The deposit lies in large lenses of kilometre dimension, apparently formed by the deposition of volcanic ash in then coastal lagoons and adjacent depressions, probably less than 3m. years ago. The exchangeable ions are sodium and magnesium with some potassium, and negligible calcium. Total bentonite in the 6 X 2km dimensions of the deposit is possibly as high as 70m. tonnes, but the economic reserves are likely to be 25-30m. tonnes. The deposits occur in continuous beds 6-10 metres thick, with 5-15 metres of a soft clay-sand overburden.