Report on Prospecting Authority No. 1780, Montejinni District, NT

Abstract

AP 1780 was granted to Tipperary Land Corporation on 26/06/1967 for one year. The Cambrian Montejinni Limestone was explored for phosphate without success. A previously reported, 10 foot-thick cupriferous horizon was relocated near the contact of the Montejinni Limestone and the Antrim Plateau basalt. This is known as Crowson's Prospect and was located by the pastoralists of that name. It has three shallow bulldozer trenches, two deeper excavator trenches to 4 feet and 8 feet deep and a 5 feet deep shaft. The workings cover an area of 350 feet by 100 feet. The richest ore is at the greatest depth and comprises cuprite and malachite in veinlets in a vesicular basalt. The area was soil sampled and rock chipped. The occurrence averages less than 0.06% copper. Regional drainage reconnaissance samples of minus 80 mesh were assayed for copper, zinc, nickel, cobalt, silver and lead. Maximum values were 35 ppm lead, 55 ppm nickel, 45 ppm cobalt and less than 1 ppm silver. Copper greater than 45 ppm was regarded as anomalous and the highest values of 120 ppm and 95 ppm came from one mile south east of Crowson's Prospect. Visible mineralisation and geochemical anomalies were found to be confined to small areas associated with the contact. Soil sampling was conducted south east of the Top Springs Hotel. Again the highest values were downslope of the contact, possibly with some secondary concentration in chert which occasionally displays copper staining. Other isolated copper occurrences, such as 'copper balls' running to a few percent were also found. Examination of watebore cuttings and outcrop mapping indicates that these occurrences are unlikely to indicate anything economic. No further work is warranted.