Annual report EL 675 Flapper Hill

Abstract

Exploration activity on EL 675 began in late 1972. Report MG 224 (submitted in December, 1972) covers the 1972 field work. Field work resumed in April 1973 and concentrated largely on the Beta-Gap and Alligator area. After a grid had been pegged, rotary-percussion drilling began. A total of 71 holes were put down. Rich secondary mineralization was encountered in the Gap area, however, no economical deposit was found. The rotary-percussion drilling gave important geochemical results and helped to define geological boundaries under alluvial cover. A total of 15 diamond drill holes were put down on prospect Beta and Alligator. At Beta a sulphide (pyrite, galena, sphalerite) zone was discovered approx. 65 in below the alluvial plains. This mineralization which locally reaches 10% combined Pb and Zn occurs within turbiditic, carbonaceous siltstone and on fractures in a coinpentent siltstone-sandstone. The mineralization trend seems approximately parallel with the Beta sub-basin margin. It is most likely less than 100 in wide, and although sulphides occur over a thickness of 20 in and more, grades exceeding 5% combined Pb and Zn are not very common and do not exceed 5 in in thickness. This trend reflects very well in results obtained by gradient array IP work. 9 connecting gradient array rectangles show a narrow, but pronounced N-S anomalous trend, with a weaker parallel trend to the W. The trends are open to the N. Other IP anomalies were discovered E of the Camp and at Alligator. Ground magnetometry at Beta shows also anomalous N-S trends, presumably related to faults. Recommendations are made to concentrate on IP in 1974 as this seems to be working very well. The known anomalous chargeability trends should be followed up by dipole-dipole lines every 400-500 m, while the remainder of the Bonaparte Gulf Basin margin should be covered by NW-SE lines, 1000 m apart. Selected areas could, be followed up by narrowly spaced dipole-dipole lines, gradient array, and finally diamond drilling.