Report on Cambrian limestones, Daly River Basin, NT.

Abstract

This report summarises the results of a helicopter survey by L G B Nixon of Adelaide Brighton Cement and Dr B Daily of Adelaide University to examine the Cambrian and Ordovician limestones of the Daly Basin. Possible Ordovician carbonates were inspected and found to be too silicious and dolomitised. All Cambrian carbonates examined were deposited under shallow water conditions. Silicification, dolomitisation and ferruginisation evident to some extent in all areas of Cambrian carbonate examined. Finding suitable grade material of sufficient lateral and vertical extent remains a challenge. Organic phosphate, present in many samples, as phosphatic shell fragments, could also prove a problem if P2O5 is deleterious to the production process. Deposits on EL 1748 warrants further work given its proximity to Darwin.