v 7

04.C3

COMMONWEALTH OF AUSTRALIA

DEPARTMENT OF NATIONAL DEVELOPMENT

BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS

RECORD No. 1962/104

POWER LINE AREA GEOPHYSICAL SURVEY

NEAR RUM JUNGLE I NORTHERN TERRITORY 1960

50 .11 "u

by

A. Douglas

The information contained in this report has been obtained by theDepartment of National Development, as part of the policy of theCommonwealth Government, to assist in the exploration anddevelopment of mineral resources. It may not be published inany form or used in a company prospectus or statement withoutthe permission in writing of the Director, Bureau of MineralBisources, Geology and Geophysics.

501128

•••^ RECORD No. 1962/104

Al

POWER LINE AREA GEOPHYSICAL SURVEY,

NEAR RUM JUNGLE,NORTHERN TERRITORY 1960

by

A. Douglas

The information contained in this report has been obtained by theDepartment of National Development, as part of the policy of theCommonwealth Government, to assist in the exploration anddevelopment of mineral resources. It may not be published inany form or used in a company prospectus or statement withoutthe permission in writing of the Director, Bureau of MineralResources, Geology and Geophysics.

CONTENTS

Page

SUMMARY

1.^INTRODUCTION^ 1

2, OPERATIONS^ 1

3. DISCUSSION AND INTERPRETATION OF RESULTS^1

4. CONCLUSIONS AND RECOMMENDATIONS^ 2

5. REFERENCES^ 2

ILLUSTRATIONS

Plate 1. Locality map^ (Drawing No. G71-227-5)

Plate 2. Radiometric contours^ (G71-250)

Plate 3. Turam ratio and Slingram real component contours.^(G71-251)

Plate 4. Slingram imaginary component and Turam phase contours.(G71-252)

SUMMARY

Radiometric and electromagnetic surveys were carried out overthe Power Line area as part of the Bureau of Mineral Resources' 1961programme of uranium prospecting in the Rum Jungle district.

The radiometric surveys outlined several anomalies, but thesignificance of these is not clear.

The only electromagnetic anomalies of note were outlined along thesouthern portion of the eastern edge of the area. These anomaliesprobably indicate a conducting bed that constitutes part of a continuousconducting-zone extending as far as Rum Jungle Creek South. Theconductivity of this zone could be due to sulphide mineralisation. Asuranium is often associated with sulphides in the Rum Jungle district, itis recommended that the electromagnetic anomalies be tested by drilling.

1.^INTRODUCTION

The Power Line area extends northwards for 9000 ft from theBatchelor/Meneling Station road over flat ground between Batchelortownship in the east and a quartz breccia ridge in the west. Access tothe area is by the Batchelor/Rum Jungle Siding road and a rough trackthat follows the Batchelor/Rum Jungle Creek South (RJCS) power line.

The Power Line area is a section of a larger survey area whichextends from the RJCS orebody around the southern margin of a prominentquartzite breccia ridge to the Rum Jungle Laterites. Along the marginof the ridge, airborne surveys have located several radiometric anomaliesthat could indicate economic uranium deposits. Electromagnetic andradiometric surveys were carried out during June and July 1961 in anattempt to locate any such deposits.

Daly (1962) has given an adequate description of theapplicability, principles, and limitations of the geophysical methods usedand has discussed the main results for the entire survey area from RJCSto the Rum Jungle Laterites. A more detailed discussion of the Power Linearea is given below,

2, OPERATIONS

The relation of the geophysical grid for the Power Line areato the grids for adjacent areas and to the Hundred of Goyder co-ordinatesis shown by Daly (1962 0 Plate 2). A 9000-ft baseline, true bearing3360 30 1 , was surveyed across the area, and traverses ranging in lengthup to 4800 ft were pegged at right angles to this baseline. The usualspacing between traverses was 200 ft, although over parts of the area a400-ft traverse spacing was used. The traverses themselves were peggedat 50-ft intervals.

The whole of the area was investigated with the electromagneticand radiometric methods. The Turam electromagnetic method was used inthe vicinity of the power line and the Slingram method over the remainderof the area.

3, DISCUSSION AND INTERPRETATION OF RESULTS

Radiometric results

The radiometric results (Plate 2) show several anomaliessuperimposed on a general background of 0.015 mr/hr. Most of theseanomalies are of low intensity and small areal extent, and are notconsidered to be significant in the search for uranium orebodies.

There are, however, three radioactive anomalies of considerableextent which warrant further discussion. Two of these anomalies occurat the southern limit of the area; one centred on 142E/3900N 0 the otherextending south-west from 138E/3000N. The third anomaly lies between62E and 74E at about 1600N.

-2-

The anomaly that extends south-west from 138E/3000N is part ofa larger anomaly that continues into the Batchelor Laterites area. Thisanomaly appears to be associated with lateritic gravel, and has beendiscussed more fully by Rowston (1962). There is no evidence to suggestthat there is a uranium orebody associated with this anomaly.

The anomaly centred at 142E/3900N occurs over a gravelled road.This gravel was probably obtained from nearby gravel pits, which themselvesshow high radioactivity. Thus the anomaly centred on 14 2E/3900N canprobably be attributed to radioactive material within the road metal,rather than to material in situ, and can be disregarded.

The third major anomaly is unusual in that part of it extendsover quartzite breccia. Known radioactive deposits in the Rum Jungledistrict are normally restricted to rocks that underlie the quartzitebreccia. No explanation of this unusual feature can be given, and thesignificance of this anomaly as a whole is not clear.

Electromaenetic results

The only electromagnetic anomalies of any interest are those thatextend from Traverse 14 2E to Traverse 100E between 4200N and 3200N(Plates 3 and 4). These anomalies probably indicate a conducting bed thatconstitutes part of a continuous conducting-zone extending as far asRjCS. Daly (1962) has discussed the significance of this conducting-zone.

Between Traverses 100E and 78E several elongate low-intensityTuram anomalies were outlined. These could be ascribed to a series ofshear zones, but as yet there is no geological evidence to support this.

The area between 78E and 52E is devoid of anomalies.

4. . CONCLUSIONS AND RECOMMENDATIONS

Only the electromagnetic anomaly between Traverses 142E and 100Eseems to warrant further investigation. Drill holes to a vertical depthof 160 ft .are recommended at the following points:

142 E l 3825N

136 E, 3800N

120 E l 3650N

109 E, 3450N

5. REFERENCES

DALY, 3.

ROWSTON, D.L.

1962^Rum Jungle district, NorthernTerritory, introductory report ongeophysical surveys 1960-61Bur Min. Re sour. Aust. Record1962/27.

1962^Batchelor Laterites areageophysical survey, NorthernTerritory 1961.Bur. Min. Resour. Aust. Record1962/103.

PLATE I

RUM JUNGLE AREA, N.T.

LOCAL T'1 MAP

GEOPHYSICAL SURVEYS, 1961

Scale^I inch 40 rnAe

Nes/Fmniss

Do/er; &dyeEa :1- _

'41 r . Dyson.;I" It z +

MehdeS^••-#-7 1:"5

/ 4-

.... *^e■^-•

e-, ÷^<7:, /3*(2'

et/n-7

;,'e

Area £51?

-4-

4E/600N

CAST LEM AIMHI