Sheet QM418 Bluff : geological resource map of New Zealand 1:250 000

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Lindqvist, J.K.; Morrison, A.D.; Doole, M.H.; Christie, A.B.; Uruski, C.I.; Brown, L.J. 1994 Sheet QM418 Bluff : geological resource map of New Zealand 1:250 000. Lower Hutt: Institute of Geological & Nuclear Sciences Institute of Geological & Nuclear Sciences science report 94/18 54 p.

Abstract: More than 5 tonnes of gold have been produced from Cenozoic alluvial gravels, and minor quantities of gold have also been obtained from beach placers and lode deposits in the Bluff map sheet area. Platinum is associated with gold in some placers and has also been detected in trace amounts in the Longwood Range basement rocks. Minor quantities of chromium, copper, manganese, nickel, zinc, silver, and lead minerals are also present in the region. Non-metallic resources are important to the economy of the region and current production is dominated by the extraction of aggregate and sand for roading, fill, and concrete. Limestone is locally produced for agriculture, and clay is mined for brick and field tile manufacture. Bluff gabbro was exploited for building facing stone. Other non-metallic minerals include asbestos, serpentine, dunite, diatomite, and zeolite. Aggregate extraction will continue to be a major industry but there is potential for development of some other commodities. For example, the considerable quartzose gravel and quartz sand resource in the area, presently used only for aggregate, could be suitable for some industrial uses. The bedded gannister and quartz conglomerate in the Landslip Hill area have been explored for potential use in the manufacture of ferrosilicon. Kaolinite-rich clays, present in coal measures, may also be suitable for further development. Lignite and sub-bituminous coal are currently mined and used for domestic and industrial heating, whereas peat is extracted for use in horticulture. Potential exists for large-scale lignite utilisation in Eastern Southland, with six large deposits of variable rank (45-60+% moisture) delineated by close-spaced drilling. Higher rank lignite mined in the Waimumu and Mataura areas, and sub-bituminous coal mined in Ohai-Nightcaps area presently enjoy an expanding market in Southland and Otago. An oil shale distillation plant was previously operated near Orepuki, but remaining oil shale resources are unknown. Surficial oil seeps have been reported and traces of hydrocarbons detected in petroleum exploration wells in the Winton area. However, the sedimentary sequence in the Winton Basin is probably too thin to have generated commercial quantities of hydrocarbons. Conversely, the Waiau Basin contains a substantial thickness of sediments and many possible trapping structures (formed from Oligocene times onwards), source rocks (Cretaceous, Eocene, and Oligocene coal measures, and Cretaceous and Eocene lacustrine shales), reservoir rocks (Cretaceous, Eocene, and Oligocene sandstones), and seals (Oligocene and Neogene mudstones). Additional drilling is required to evaluate the hydrocarbon potential of the region. (auths)