1975 Track Etch survey program in the Ngalia Basin

Abstract

Enclosed are two sets of the final tabulated data and several radon contour maps from your recent Track Etch Surveys in the Ngalia Basin. We have separated the tabulated data.according to the area mapped and for general interest we have included a complete tabulation of the data from all surveys. We are enclosing not only the Track Etch contour map of the Djuburula East-Rinkabeena area you requested but also maps of the Autobahn, Oodnappina and Ojuburula West areas since they had some interesting data that shows to best advantage when mapped. These extra maps were made at no additional cost to you. The Track Etch readings on the tabulated data sheets are reported in units of tracks per square millimeter (T/mm2) and they are normalized to equivalent 30 day exposures. These data have been tabulated in two different ways for easy use; firstly by ascending film serial numbers and secondly by ascending Track Etch readings. The readings from the complete survey ranged from a low of 0.6 T/mm2 to a high of 2002 T/mm2. There were a relatively large percentage of the readings which were quite low (below 5 T/mm2) which resulted in a mean background for the complete survey of 6.5 T/mm2. Background values for the individual areas ranged from 1 to 15.5 T/mm2. For comparison background values for the Northern Territory East Alligator River area range from 4 to 30 T/mm2. Background values generally are related to the surface or shallow trace mineralization and its distribution in the area covered. There is evidence from several of the areas that there are two or more radon background distributions. These were identified by plotting a histogram of the distribution of, the readings and they are most evident in the groups of Track Etch films which have a fairly large number of low values. We believe that this may occur because you are surveying over two or more separate geological units in these wide area surveys. If by combining the Track Etch results with other geological exploration techniques you may be able to separate these geological units then there may be some additional information to be gained concerning the various units. For example different uranium contents of each geological unit might lead to the identification of those units with greatest potential. The results presented in this report from the Track Etch surveys are of particular interest in several areas. Follow up geological analysis and further Track Etch measurements are recommended on the more anomalous areas, on single point anomalies and on areas with elevated background values.