Sheet QM399 Waimate : geological resource map of New Zealand 1:250 000

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Christie, A.B.; Bishop, D.G.; Doole, M.H.; Morrison, A.D.; Field, B.D.; Brown, L.J. 1994 Sheet QM399 Waimate : geological resource map of New Zealand 1:250 000. Lower Hutt: Institute of Geological & Nuclear Sciences Institute of Geological & Nuclear Sciences science report 94/17 69 p.

Abstract: Sheet QM399 Waimate covers the greywacke terrain of the lower Waitaki Valley, the late Cretaceous and Tertiary sequence of the Oamaru district, and the northeastern part of the Haast schist. A considerable amount of gold has been obtained from the map area, both from Mesozoic quartz lode deposits in the schist and from Cenozoic quartz-pebble conglomerate placer deposits. An open pit mine at Macraes Flat is currently producing more than 3000 kg of gold annually from a quartz lode deposit. Scheelite and antimony are also present in minor amounts in the schist-hosted quartz lodes and both have been mined in small quantities in the past. Minor quantities of bismuth, iron, lead, manganese, silver, zinc, and zirconium minerals are also present in the Waimate Sheet area. The region is well endowed with non-metallic resources, particularly aggregate, limestone, dimension (building) stone, clay, diatomite, sand, and silica. Greywacke and basalt suitable for the production of good quality aggregates are available in the eastern part of the sheet area. In the western part, quartz conglomerate and schist are generally used for aggregates. Extraction is mostly from alluvial deposits: the modern river channels, Quaternary river terrace gravels, or Tertiary conglomerates. Large resources of Eocene and Oligocene limestones are present in areas near Tirnaru, Waitaiki Valley, Oamaru, and Waihao Valley, and ?Triassic crystalline limestone (marble) is present in the Blue Mountains near Dunback. Most deposits are worked as a source of limestone for use in agriculture, industry, and for aggregate. Limestone at Oamaru (Oamaru Stone) is an important source of dimension stone. Basalt, sandstone, schist, and slate have also been used for building stone in the past. Ball clay is mined at Hyde and similar deposits are known at other localities. Diatomite at Middlemarch has been mined for use as a filter material and large resources are available there and at Oamaru, for potential future development. Large deposits of silica sand are present at Hyde and Kyeburn and sand from Hyde has been used in building, for glass making, and in ceramic glazes for pottery. Several unworked silica sand deposits are present in the Waitaki Valley. Deposits of Tertiary quartz-cemented conglomerate (e.g. Mt Buster) have potential as a source of lump silica for ferrosilicon or silicon metal manufacture. Other non-metallic minerals present in the Waimate map area include fluorapatite, garnet, gemstones, glauconite, and hematite. Bituminous and sub-bituminous coal have been mined in the Shag Point and Waitaki coalfields respectively, and lignite has been extracted from numerous deposits in Central Otago. Large resources of lignite have been identified in the Hawkdun and Home Hills sectors of the Blackstone Coalfield. Oil shales are present at Carnbrians, Idabum, and Waihao Downs. Two deep onshore and two offshore petroleum exploration wells have been drilled and further work is currently being car ried out in the offshore region with a focus on the Cretaceous section. The onshore region is regarded as non-prospective. Groundwater is used locally for domestic, stock, and irrigation supplies and has potential for increased development. Thermal water is present at Timaru. (auths)