Sykes, R. 1987 New Zealand Coal Resources Survey, Reefton and Garvey Creek coalfields : recommendations for exploration. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report M 156. 78 p.
Abstract
Six separate areas of Brunner Coal Measures (Eocene) cover approximately 4000 ha of the Victoria Range Foothills and the eastern side of the Grey-Inangahua Depression. These areas include two major coalfields, Reefton and Garvey Creek, and four minor coal-mining areas. Reefton coal is predominantly of high volatile C bituminous rank whereas that from Garvey Creek is borderline high volatile A and B bituminous. Using updated exploration and mining databases and existing geological reports, this report identifies areas within the coalfields that potentially contain more than 200 000 tonnes of coal, in seams exceeding 1.5 m in thickness and less than 400 m deep. Resources remaining in areas already mined are not considered. To explore the areas identified, specific drilling and seismic work is proposed. Past mining in the four minor areas was small-scale and generally unsuccessful because of inadequate coal reserves, unfavourable geological conditions, difficult access and small local demand. The prospects for future mining in these areas are poor. No exploration is recommended. In Reefton Coalfield, most of the more easily mined coal has been extracted but many areas worthy of future exploration remain. Twenty six areas potentially containing seams of target six are identified. The most promising areas for future mining are within No 2 Upper and No 4 seams, generally under less than 200 m of overburden, and within the Reefton to Waitahu Plateau area. The combined resources of the target areas are estimated at approximately 26.5 Mt of coal-in-ground of which most is classified as inferred to hypothetical. Thirty four drillholes and six seismic lines are proposed. The resources of Garvey Creek Coalfield are estimated at approximately 13 Mt of indicated to inferred coal-in-ground, of which nearly all are within the Basal seam. Apart from the already well-explored Island Block, two areas are likely to contain resources substantially exceeding target size within structures not too unfavourable for mining. Eleven initial drillhole sites are recommended. In both Reefton and Garvey Creek coalfields, mining to date has generally been confined to resources at shallow depths. In some areas, this practice has rendered possible resources at greater depths less accessible to future mining and if continued, could ultimately sterilise these resources. It is strongly recommended that the deeper resources of both coalfields be adequately explored and the mining options assessed before mining at shallow depths progresses much further. (auth)
