Annual report Newcastle Range, Delamere

Abstract

EL 5441 is central to the Newcastle Ranges and drainage is well developed in this area, The sampling method thus consisted of stream sampling combined with barrage sampling, the former being the main reconnaissance exploration tool used in the VRB. Stream samples in general averaged 50 litres of -2mm sieved material. The lower cut-off varied at times, but if the excavated material was dry a lower cut-off at 0.4mm was employed. With wet/damp samples no undersize was taken off. Barrage samples were employed as a back-up to stream sampling. Barrages typically ranged upwards from a minimum of 200 ltr of excavated material, all manually collected. With 82 samples collected in EL 5441 an average sample density of one sample per 13 sq kms was achieved. Geologically the NRP can be divided into two domains: the massive quartz sandstones, siltstones and shales of the Newcastle Range and the predominantly dolomitic rocks to the south of the Newcastle Range. As can be seen in Table 4 a high percentage of sample sites fell into the average to poor range. These sites could be directly related to the dolomitic rocks. Typical sites would contain white carbonate clasts, a black clay/soil component and relatively little material in the -2mm + 0.4mm size fraction. Digging was always very hard at these sites, and sieving would produce little material in relation to the amount removed. As such, a higher sampling density was used in this area. In direct contrast, sampling in the Newcastle Range itself was of higher quality. The greatest percentage of sites were rock bars of good to very good quality. Iron pisolites were common in trapsitcs. Due to the quality of trapsites and good drainage a lower sampling density was used. A subdomain of the Newcastle Range could be defined. This region comprised sand choked streams where the slope of the range decreased. Sampling in this area was typically difficult due to the lack of trapsites.