Final report on exploration activities EL 1386 Tennant Creek, Northern Territory 17-12-1976 to 31-12-1981

Abstract

Exploration activity by MPAL and its Joint Venture partners has been on Licences within the Tennant Creek 1:250,000 sheet area bounded by latitudes 19 degrees south and 20 degrees south and longitudes 133 degrees 30' east and 135 degrees east. The township of Tennant Creek (population 3000) is located 500 km north of Alice Springs and 1000 km south of Darwin. Comprehensive reviews of the geology are given by many authors including Crohn (1965), Large (1975) and Black (1977). The Early Proterozoic Warramunga Group forms a large portion of the Tennant Creek Block. It has been subdivided into the Whippet Formation, a sequence of shallow water sandstones; the Bernborough Formation, a series of rhyolitic ex trusives and intrusives and the Carraman Formation, consisting of shale, sandstone and local tuff levels. The Carraman Formation hosts all the known mineralization in the area. Carpentarian shallow water sediments of the Hatches Creek Group in the south and Tomkinson Creek Beds to the north unconformably overlie the Warramunga Group. Mineralization in the Formation consists primarily of gold-copper-bismuth assemblages hosted in 'ironstones' a local term used to describe the hematite + magnetite +, quartz +, chlorite gangue mineralogy. The major orebodies mined to date are described as pipe-like or pod-like in form. Work undertaken on EL 1386 by AOM and MPAL has included an airborne magnetic and spectrometer survey, an interpretation the data, a photogeological study, open hole percussion drilling and geochemical assaying. In June 1977 a low-level airborne magnetic and spectrometer survey was flown over EL 1386 by Geometrics International Corporation on behalf of Australian Ores and Minerals Ltd. During early 1978, RK Jones of Hunting Geology and Geophysics (Australia) Pty Ltd undertook an interpretation of all available aeromagnetic and spectrometer data in order to determine the possible influences of regional structures on the local geology. The study outlined east-northeast, southeast and northwest faults and shears and also indicated the presence of distinct magnetic zones. Later in 1978 an interpretation of the low-level airborne data was undertaken using the Tennant Creek model of hydrothermal type replacement genesis. No magnetic anomalies of the 'Tennant Creek type' were located. During August to October 1978, a photogeological study of the eastern part of the Tennant Creek Mineral Field was undertaken on behalf of Marathon Petroleum Australia, Ltd by Loxton, Hunting and Associates Pty Ltd using black and white aerial photographs. The aim of the interpretation was to provide as detailed a lithostratigraphic and structural map as on which to base subsequent exploration. In September 1979 RK Jones (Consultant Geophysicist) undertook a revised interpretation using the model of strata-bound volcanogenic type using this model a magnetic anomaly was delineated within EL 1386 and has been tested by subsequent drilling. In October 1979 Rockdrill Contractors Pty Ltd of Brisbane supplied a truck mounted Foxmobile rig and support equipment necessary to carry out an open hole drilling programme. The aim of the programme was to test the magnetic anomaly and obtain fresh rock chips on which geochemical analysis could be undertaken in the hope that indicator elements could be-used as an exploration tool. A total of seven holes were drilled for an aggregate of 277 metres. All holes spudded into Carraman Formation sediments of the Warramunga Group. Subsurface geology consisted of shales, interdigitating shales and ?volcanics and quartz porphyry. Samples were submitted for assay of Cu, Mn, Co, Fe, As, Bi, Se, Ba, Sb and Mo. The drilling programme failed to locate the source of the magnetic anomaly. During November 1981, Juett Consolidated Ltd. of a truck-mounted Griffin rig to carry out a RAB drilling programme. The aim of the programme was to geochemically test a subtle magnetic anomaly in the central portion of the EL. A total of 6 holes were completed for an aggregate of 180 metres. Lithologies intersected included fine grained sandstone, siltstone and shales of the Early Proterozoic Carraman Formation. The program failed to adequately explain the magnetic anomaly. Details of all phases of the undertaken by Australian Ores and Marathon Petroleum Australia Ltd are available upon request from the company offices in Perth and Brisbane respectively or from the files of the N.T.D.M.E. in Darwin.