Annual report for EL 4498, Ranford Hill NT.

Abstract

Ranford Hill, EL 4498, was explored by Australian Coal and Gold Holdings Ltd for tin, gold, basemetals, diamonds and uranium mineralisation in lower Proterozoic metasedimentary rocks of the Pine Creek Geosyncline. Exploration methods employed included geological mapping at a scale of 1:25,000, rock chip sampling of quartz veins and alteration zones, stream sediment sampling with geochemical analysis of the fine fraction and mineralogical examination of the coarse heavy mineral fraction, and radiometric prospecting. Expenditure in the first year of the licence amounted to $16,380. Significant hydrothermal, vein-type tin mineralisation was discovered at Mary River Camp, about 3 kilometres west of Ross Smith Battery. About 10 abandoned shafts have been sunk on easterly and northerly trending quartz-tourmaline-cassiterite veins in altered greywacke of the Burrell Creek Formation. The veins are up to several hundred metres long and two metres wide, mullock samples from the abandoned workings assay up to 2.5% Sn. Additional quartz-cassiterite veins were located in the East River Camp, Ross Smith Battery and Evelyn-Mary River areas at sample sites RHC 20, 21, 32, 37, 46, 49, 56, 57 and 59-64. Alluvial tin deposits at Mary River Camp appear to be small, of the order of 10,000-70,000 cubic metres, although fossil gravel deposits in the drainage system of the Mary River Camp tin deposits have potential to host sizeable detrital concentrations. Geochemical analysis of gossans and massive sulphides from the Coronet Hill basemetal deposits returned generally low precious metal values, e.g. Au 0.21-0.48 ppm, Ag 7.0-150.0 ppm, Pd Bld-0.003 ppm, and Sn 313-410 ppm. Silver values are erratic and are significant in massive sulphide and gossan formed from the massive sulphide. These values in conjunction with subeconomic Pb+Cu values do not support a major re-evaluation of the deposits at this stage. The rock chip sampling programme of quartz veins gave low gold values, with 16 of 138 samples assaying above 0.10 ppm, with a maximum of 0.32 ppm Au. However, four samples, RHC 04, 05, 37 and 115 are considered significant because of either associated basemetal values or favourable geological environment. Geochemical analysis of -80# fraction from the alluvial stream sediment samples produced anomalous values in samples RH 03 (Zn, U), RH 06 (Pb, Au), RH 16 (Cu, Zn, As, Sn, Pb), RH 19 (Sn), RU 24 (Au) and RH 25 (Au). Mineralogical examination of heavy mineral suites from alluvial samples identified cassiterite in samples RH 04, 07, 09, 13, 16, 17, 19, 20 and 21; copper, lead and zinc minerals in samples RU 06, 07, 08, 09, 10, 13, 16, and 21; and possible diamond indicator minerals in RH 09,- 20 and 21. Samples RH 04, 06, 09, 17 and 20 cannot be explained by known mineral occurrences and may define new provinces. The 1985/86 programme will follow-up the results outlined in this report, primarily by detailed geological mapping of prospects and additional geochemical sampling of anomalous drainages.