1971 Photogeological interpretation of AP 2600 Victoria River Basin

Abstract

A literature search and photogeological interpretation of areas covering 6925 sq km of the Northern Territory were commissioned by North Coast Mining Limited. The literature searches were carried out over the two areas, designated Helen Springs and the Victoria River Basin, in November and December, 1970 and the results are contained in Report No's 60 and 61. This report describes the results of the photogeological studies mainly in relation to the mineral potential of both areas. Two sets of black and white aerial photographs, 24 x 24 cms at the approximate scale of 1:83330 were used in this photogeological investigation, together with geological maps of the two areas at scales of 1:250,000 and one set of old uncontrolled photomosaics of the Victoria River Basin a t 1:63360 scale. An uncontrolled photomosaic, at photo scale, covering the Victoria River Basin area was hand-mounted and subsequently cut into two sheets; the technique used in mounting the photomosaic was such that only every other photograph was laid down, the alternate photographs providing stereoscopic coverage. The photogeological interpretation was later carried out on transparent overlays to the mosaic sheets and is presented as enclosures with this report as a set of two coloured maps at approximately 1:83330 scale together with the master transparencies. In general the Victoria River Basin region is quite mountainous, with deep and wide valleys, and some difficulty was experienced in mounting the uncontrolled photomosaic; inaccuracies due to distortion were, however, minimised by using only the central part of each photograph. The photogeological interpretation of the Helen Springs area was carried out by annotating transparent overlays to alternate photographs. The annotated templates were then hand-mounted together by the radial line method and the resulting coloured map at 1:83330 scale is presented in this report together with the master transparency. Morphologically the Helen Springs area is rugged, though considerably less so than the Victoria River Basin. In general it has lower elevations. The aerial photographs were of good quality and the consistency of the tonal contrast displayed on the photographs facilitated the interpretation.

The geological maps a t 1:250,000 scale covering both areas are generally good and consequently the principal aim of the photointerpretation was to map in detail structural characteristics and features and to delimit tonal variations which may relate to structural or mineralised features. Field inspection of these anomalous areas is considered essential.