Geological and physical characteristics of some magnetic sources in lower proterozoic metasediments pine creek geosyncline N.T.

Abstract

Regional aeromagnetic surveys in the Pine Creek Geosyncline, show that much of the region has a fairly flat magnetic field, and few deep seated magnetic anomalies are evident. The most prominent features are zones of narrow curvilinear anomalies which occur over Lower Proterozoic metasediments. The geological and physical characteristics of the sources of some of the magnetic anomalies over the Lower Proterozoic metasediments have been investigated by: detailed interpretation of magnetic anomalies, geological mapping, ground magnetic surveys, laboratory physical property measurements, and mineralogical studies of rock samples and drill core. In the central part of the Pine Creek Geosyncline most of the prominent curvilinear anomalies result from strongly remanently magnetised iron sulphides in the Golden Dyke Formation sediments. In the east, in the Alligator Rivers Uranium Field, the prominent anomalies result from inductively magnetised magnetite in Cahill Formation schists. In the west, in the Litchfield Block, prominent anomalies result from inductively magnetised iron oxides in unnamed schists. The regional distribution of magnetic iron facies in the Lower Proterozoic metasediments might be a useful tool to assist in formulating hypotheses regarding the geological history of the Pine Creek Geosyncline.