H.—34.

Economic Geology. Gold. —The gold-bearing gravels and silts of the Orepuki Series have been worked extensively during the past sixty years over an area extending from Waimeamea River to Ourawera Stream at Round Hill. In past decades a considerable amount of work was done on the black sands on the beach of Te Wae Wae, but to-day these activities are.confined to two or three parties. At Orepuki there are at present four parties carrying out sluicing operations, while at Round Hill extensive work is being carried out by the Round Hill Gold Mining Co. with considerable success. The gold is fairly evenly distributed through the entire Orepuki Series, there being no particular auriferous formation. In the Orepuki district the bottom is generally the Waimeamea or Taunoa Series, locally known as the " papa " bottom, and in the Pahia - Round Hill area the weathered igneous complex forms the bottom, termed the " diorite " bottom by the local miners. All parties working in the area are receiving a good return for their labour, and there is no reason why there should not be more activity than there is at present. Coal —At the base of the Waimeamea Series, immediately below the oil shale, is 10 ft. to 20 ft. of hard brown coal. This coal has been worked in the past at several places in the district, just east of the Waimeamea River, near Taunoa Creek, and at the shale-works where coal was obtained during the shale-mining operations. A small open-cast mine is at present working on the banks of the Waimeamea River, producing enough to supply a part of the local market. In the Orepuki area there is an extensive coalfield, that should be of considerable importance in the future. This field is bounded by the Waimeamea River in the north and by Falls Creek in the south. Oil Shale. —A fuller report on the work carried out on the Orepuki Shale deposits will appear in the New Zealand Journal of Science and Technology. In 1899 the New Zealand Coal and Oil Co. erected works and began mining the shale on the eastern bank of the Taunoa Creek, about two and a half miles from Orepuki. A drive was put in for a distance of 900 ft. down the dip of the shale, which is here 25° south-south-east. Some 14,000 tons of shale was obtained during the period the works were in operation. Shale was also mined on a small scale at the Waimeamea River, where the outcrop is only 8 in. thick, and near the shale-works it was obtained by sluicing. In the main mine the shale was 41- ft. thick, which is the average thickness in the area adjacent to the works. In the year 1908 the New Zealand Coal and Oil Co. had four bores put down on their property, along a line running north-north-west from the shale works and on the southern bank of the Taunoa Creek. The depths obtained from these bores agree with both the geological and geophysical evidence. Samples from boreholes were treated, and the following table gives the borehole information and the treatment results :

These tests were carried out by Ronald Johnstone and Son, of Glasgow. An estimation of the amount of shale available is given in the more comprehensive report referred to above. Other Economic Deposits— There is no limestone of any value in the area discussed in this report. The fine-grained, marly mudstones that occur at Waihoka may be of value to the cement-making industry. Road-metal can be obtained in unlimited quantities from the gravel terraces and flats of the Waiau Valley, but there are no exposures of the igneous complex suitable for quarrying. COAL RESOURCES SURVEY. By H. E. Fyfe, M. Gage, and W. E. Hall. Field-wokk. In the later part of the 1938-39 season, field-work continued in the same areas as were described in last year's annual report. Preliminary traverses were run along the ridge between Brunner and Mount Davy mainly for the purpose of tying in the earlier detailed work of H. A. Mis m the Goal Creek basin This enabled his survey, with additions by the present survey, to be incorporated m the new plans Traverses were run in the headwaters of branches of Coal Creek rising on the Mount Davy ridge and on the spurs between them. In Seven-mile Stream geological observations were made in and around Moody Creek, and Baddeley and party leases in connection with mining problems. During the winter months the Coal Creek basin was triangulated and many points were fixed along the Brunner-Blackball side of the coalfield in preparation for geological work. Weather conditions did not permit completion of the observations until well into the present season. Also during the winter some geological prospecting was done in the Williams- and party, Hunter and party, and Moore and party areas. At the commencement of this season survey lines were cut along streams and ridges at Roa, and surface prospecting was done in anticipation of geological work. The field-work is not yet sufficiently advanced to permit definite correlation between two areas, for each of which the stratigraphic sequence is satisfactorily established. In the following account, therefore, these areas, which are separated by a line running roughly from Blackball Beak to the outfall of Cavern Creek, will be referred to as the north-western and south-eastern areas respectively.

83

""ST* »— c 35:'| Am pr= m ,.?'trFt. in. Ft. in. 1 .. 180 6 4 6 45 21-9 2 287 0 4 9 36 25-55 3 i' 375 6 4 8 45 31-0 4 .. 479 3 4 3 45 28-30