Evaluation of the natural lagoons of the Central Province, N.S.W. ? Are they sapphire-producing maars?

Abstract

The lagoons located on the basalts of the Central Province, N.S.W. are not interpreted as maars, but are interpreted to be formed within wind blown lunettes occupying the wide, flat floors of basalt filled valleys. The aim of the exercise was to determine the subsurface morphology and economic potential of the lagoons as they have been described as "maar-like" and possible sources of sapphire-bearing volcaniclastic rocks (Pecover, 1987). Interpretations based on the drilling, geophysical modelling and mapped geology find the lagoons to be axial to pre-basaltic drainage channels overlying at least 10 metres of valley fill flow basalts. Drilling at Kings Plains Lagoon intersected basalt flows overlying silicic volcanic basement and failed to encounter any breccia within, or feeder vent below, the structure. Bulk testing indicates that these features do not constitute economic targets.