Annual report ELs 5689 and 5801, Kulgera for the period 1988 to 1989.

Abstract

NT evaporites are investigating the possibilities of harvesting evaporite minerals and other useful products from playa salt lake sediments or from the evaporation of the brines. In the first year of exploration on ELs 5689 and 5801, emphasis was placed on assessment of sediments and highly concentrated brines in the playa chains. The lakes are part of both a modern drainage system and a much larger palaeo-drainage system, which during the Tertiary discharged to Lake Eyre via the ancestral Finke River. Cainozoic sediments in the study area are tens of metres thick and comprise alluvial-aeolian clay and sand interbedded with lacustrine deposits. Bedded dolomite, limestone, siltstone and evaporites (mainly gypsum and anhydrite) of Proterozoic age underlie the Cainozoic sediments at Lake Amadeus. Both Cainozoic and fractured bed-rock aquifers appear to be present. The playa lakes are essentially discharging/recharging outcrops of shallow groundwater aquifers with brines derived from both modern and Proterozoic sources. Work involved literature review, field mapping, sediment coring, water sampling and laboratory analysis of the samples collected. Coring along transects was conducted by tapping PVC tubes into the the playa beds. Grab samples were collected form pits and bedrock. Brines were collected. In addition, 47 bulk surface and pit samples were also collected. Cores were split and analysed by XRD and microscopy. Further work will focus on magnesite and dolomite, zeolites and clays, and evaporites (sulphates, chlorides, and mixed sodium, calcium, magnesium and potassium).