Annual Report for EL 1801 and EL 1956 for 1982-1983

Abstract

An intensive programme of field mapping, structural analysis, petrology and geochemistry has been carried out for Mistral Mines NL under the supervision of Drs Jazies, PR (Structural Geology) and Oliver, ILL (Metamorphic and Chemical Petrology). Mapping has been largely carried out by postgraduate students (Lawrence R,W., Bowyer, D., Ding, P). During the 1981 field season investigation was restricted to l801A. A large proportion of the licence was mapped at 1:25000 scale by the distribution of the anorthosite, which bounds the ruby deposits, was determined. The locations of a number of ultramafics were recorded, these being potential sites for further ruby discovery. Lawrence also mapped an area of 1:3000 scale surrounding the ruby mines and including most of the mineral leases. Following the mapping of the Lease areas a theodolite survey resulted in the production of a 1:500 topographic map. Lawrence selected part of the surveyed area for mapping. The remains and bulk of this mapping was carried out by Raffran, NCG (contract geologist for Neil Cole & Associates). Detailed mapping of the subsequent earthworks was carried out by Lawrence. A few costeens were also mapped by Raffran and Warne, ICR.

(geologist for Mistral Mines No Liability). Following the 1981 Field season, Lawrence compiled a 1:125000 map presenting a proposed exploration plan for working on a number of assessable ultramafics immediately to the south of Spriggs Creek. This area was then mapped at 1:6250 scale prior to further investigation in 1982 with the aid of a back-hoe. Lawrence supervised the digging of costeens and then mapped them; however most of the ultramafics were associated with siliceous biotite gneiss. Free quartz was taken as a negative indicator for corundum. No rubies or potential ruby bearing layers were discovered. Costeens were also made in the mineral lease area revealing further large thicknesses of ultramafic which could be mined easily. Further 1:25000 scale mapping was carried out by Lawrence and Ding P (visiting research fellow from China working in association with the University of Adelaide). Lawrence completed the mapping of l8OlA, while Ding mapped l956A and the area between the two leases. The anorthosite horizon of interest became thinner and more strongly boudinaged toward the south of 1801A and was not recognised at all in 1956A. Bowyer, D.G (Honors student, University of Adelaide) mapped an area at 1:6250 scale which included part of the northern margin of EL l8OlA. No further anorthosite was located. An altramafic he located, which had been investigated using a bulldozer (presumably by Bruce, J working for Mistral Mines) contained corundum and kyanite; however, the colour of the crystals was quite pale. CONCLUSIONS - As no anorthosite has been located in EL l956A no further investigations need be carried out.