Fiji — Colonial Geological Surveys 1947–1956
|From Dixey, F. 1957. Colonial Geological Surveys 1947–1956: a review of progress during the past ten years. Colonial geology and mineral resources. Bulletin supplement No. 2. London: HMSO.|
Prior to 1951, when systematic geological survey work was first put in hand by the Government, some geological work had been carried out in Fiji by private mining organisations, by research workers from overseas institutions, and by Inspectors of Mines employed by the Department of Lands. In addition, the geology of two areas embracing possible dam sites had been examined for the Government of Fiji by a consultant from Great Britain. The decision to establish a Geological Survey was, however, made after a reconnaissance of the Fijian scene by the Director of Colonial Geological Surveys. Headquarters were therefore established in Suva, where the Survey is attached to the Department of Lands, Mines and Surveys and financed by funds provided under Colonial Development and Welfare Acts.
Dr. W. J. Skiba took up the appointment of senior geologist in 1952, following the appointment of a geologist in 1951. For about two years, until he was unfortunately invalided from the Colony, he did much valuable work on geological mapping, mineral investigation and engineering geology, and, during the absence from the Colony of an Inspector of Mines, he also advised the Mining Board and prepared its Annual Reports for the years 1952 and 1953. Late in 1956 Dr. N. J. Guest, from the Geological Survey of Tanganyika, assumed control of the Department; one geologist was in post, and a second was due to arrive early in 1957. It has not yet been possible to fill a post of draughtsman which was created in 1952.
Since 1952 the geology of approximately 660 sq. miles of Viti Levu—the principal island of the Colony—has been mapped on scales varying from one-quarter of a mile to the inch to ten miles to the inch. The total area mapped has not been continuous, because it has been necessary to give priority in mapping to areas of potential economic importance.
A survey of the copper-silver-gold occurrences in the upper Sabeto Valley has shown that the mineralisation is associated with a body of quartz-monzonite that is intrusive into a series of volcanic rocks, and exploratory drilling was consequently recommended. At Wainivesi, on the eastern side of Viti Levu, mapping showed copper-zinc mineralisation to be associated with diorites and tonalites intruding andesites and Wainimala tuffs. The locality is not under development. In the same area, magnetite occurs and is considered to be a result of the intrusion of limestone by plutonic rocks. Similar occurrences were examined in western Viti Levu. Some 310 sq. miles were mapped in south-western Viti Levu because of the occurrence in this region of iron ores and gold-and manganese-bearing rocks. Manganese mineralisation appears to be associated in the majority of cases with tuffs and limestones of the Ndakandaka Succession. After mapping the extent of the Ndakandaka Succession, it became possible to delineate those areas most suitable for prospecting. Mapping of the Nasauthoko area, in west central Viti Levu, has shown further development of the tuffs and bedded limestones, and approximately 10,000 tons of manganese ore have been removed from two mines in this region. Both mines have come into production within the past three years.
A tour was made of Vanua Levu, the second largest island in the Colony, in order to see whether a similar association could be recognised there, but a rapid reconnaissance of the principal rock types suggested significant differences in its geology from that of Viti Levu, and the critical Ndakandaka Succession appeared to be absent.
Following reports of occurrences of ores of copper and manganese and of phosphate, brief surveys were made in certain islands of the Lau and Yasawa Groups, but the alleged deposits were found to be small or non-existent.
Geological mapping on a regional basis became necessary on the Nadrau Plateau and in the Sovi Gorge area as a basis for reporting on dam sites for hydro-electric schemes. Proposed dam sites were also examined at Savura Creek and elsewhere, and reports were submitted on various building and quarry sites. Advice has been given to Government departments and to mining companies.
Visits were made, in company with two officers of the New Zealand Department of Scientific and Industrial Research, to the majority of hot springs known in Fiji, and some 20 areas were studied, two of which were previously unrecorded. Heat-flows were determined and water samples taken for analysis. Two areas, those of Nakama and Wailevu, both in Vanua Levu, warrant further investigation.
In September, 1953, an earthquake of 30 seconds duration occurred, causing damage and loss of life. The maximum intensity of shock experienced, strength 6–7 Mercalli's scale, extended over an area of approximately 17 to 23 sq. miles, and the epicentre lay 10 miles west of the city of Suva. The earthquake was followed by a tidal wave, and by aftershocks which continued for some months. An officer of the New Zealand Geological Survey assisted the senior geologist in a study of the earthquake, and results will be incorporated in a report.
Annual Reports of the Mining Board for 1952 and 1953, and Annual Reports of the Geological Survey for 1952 to 1955, have been published. Numerous typescript reports on the geology and mineral resources of Fiji have been prepared, but remain unpublished.
Copper and copper ores
Iron and iron ores
Fiji — Staff list
Geological Survey, Department of Lands, Mines and Survey, Suva
N. J. Guest, B.Sc., Ph.D., F.G.S., A.M.I.M.M.
S. R. M. Harvey, B.Sc.
R. W. Bartholomew, B.Sc., F.G.S.