Annual Report on EL 4744 Frances Creek

Abstract

CSR Limited conducted at its sole expense an exploration programme for disseminated gold mineralisation within Exploration Licence 4744 (EL 4744), known as the Frances Creek area, under a Joint Venture Agreement with Casey Consolidated Holdings. During 1985, an airborne geophysical survey was undertaken to delineate the Zamu Dolerite, and to define any alteration features. No significant structures or anomalies were defined within EL 4744. A soil sampling programme was undertaken on the Frances Creek Mine Grid. Anomalous arsenic and gold values were obtained, but these results were not confirmed by rock-chip analyses results nor by results from channel samples in a trenching programme. However, samples from an altered dolerite adjacent to a brecciated quartz vein exposed by the trenching programme did return low-order anomalous gold values, which will require follow-up work. No anomalous results were obtained from a bulk stream sediment sampling programme, nor from composite rock-chip samples collected from the altered Zamu Dolerite. An airborne geophysical survey was completed over the Frances Creek area by Geoterex Pty. Ltd. with data processing undertaken by CSR Limited. The survey comprised both total field magnetic and 4 channel radiometric surveys on east-west flight lines at 200 m spacing with a 90 m terrain clearance. North-.south lines were flown at 3 km intervals. The total magnetic field strength was measured, using a caesium vapour magnetometer at 0.2 sec sampling intervals or 13 m at the average aircraft speed of 220 km/hour. A Nuclear Data 256 channel spectrometer with a 33.1 litre crystal was used to record radiometrics (Total Count, Potassium, Uranium and Thorium). SampHng rate for radioFnetrics was one second or approximately 65 m. The survey navigation was by 1:20,000 colour airphotographs. AMG-controlled base maps were produced at a scale of 1:25,000. Engineering Computer Services Pty. Ltd. produced preliminary contour map of magnetic data while final contour plots of magnetics and image processing of magnetics and radiometrics were produced by CSR Limited. Interpretation of the airborne data (ORG No. 8586-12) was directed towards three main criteria (Anderson, 1986, unpublished data);

1. mapping lithological units, particularly in areas of poor outcrop.

2. defining major structures.

3. defining areas of possible alteration within prospective lithologies.

The magnetic relief of the Frances Creek survey is dominated by northwest-trending anomalies parallel to the Pine Creek Shear Zone which probably represent major faults. Northwest-trending highs and lows are also consistent with major parallel folds of a persistent stratagraphic unit. Minor secondary faulting is also inferred to account for terminations of some magnetic features (Anderson, 1986, unpublished data).