Caledonia aims to strike lightning

Australian-based Caledonian Pacific Minerals (CDM-V) has applied for an exploration licence covering a diamondiferous diatreme in the Lightning Ridge area of northern New South Wales, Australia.

The diatreme was discovered by a division of Rio Tinto (RTP-N) in 1997. The licence area covers a cluster of bull’s-eye magnetic anomalies, which are typical of diatreme fields.

Only one 0.15-sq.-km anomaly has been partially drill-tested. Other anomalies covered by the licence range in size from 0.01 to 0.25 sq. km, none of which has been drill-tested. By comparison, pipes greater than 0.15 sq. km are considered large.

One of two reverse-circulation holes drilled by Rio Tinto returned three microdiamonds and a suite of kimberlitic indicator minerals from a 86.2-kg sample of basalt breccia believed to be a diatreme.

The lack of kimberlite source rocks and the widespread occurrence of diamonds in eastern Australia have led the Geological Survey of New South Wales to develop a new model for diamond formation and emplacement, known as the subduction or s-diamond model.

In this model, diamonds form during subduction and are brought to the surface by alkali basalt volcanism as diatremes and dykes. Diatremes are breccia-filled volcanic pipes formed by gaseous explosion.

Drilling to define the size and grade of the diatreme and to test other anomalies will begin as soon as the licence is granted.

Meanwhile, West African Coronation International Mining recently proposed a $5-million proportional takeover of 60% of the issued shares of Caledonian Pacific Minerals. The offer price is 18 per share.