Sheet QM360 Hanmer : Geological resources map of New Zealand 1:250 000

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Eggers, M.J.; Sewell, R.J. 1990 Sheet QM360 Hanmer : Geological resources map of New Zealand 1:250 000. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report M 173. 41 p.

Abstract: Sheet QM 360 has yielded some of the richest metallic and non-metallic geological resources in the South Island which have been exploited more or less continuously over the past century. Mining is now restricted largely to non-metallic commodities such as coal, aggregate and limestone although several mining licenses have recently been granted for alluvial gold mining. Almost all of the mineralised and economic coal-bearing areas lie west of the Alpine Fault whereas to the east, the resources are chiefly aggregate and limestone. Gold occurs in quartz veins within Greenland Group and as detrital particles in alluvium. Lode gold mineralisation is usually accompanied by trace metals such as antimony and arsenic. Rarely, tungsten and molybdenum are concentrated in quartz vein stockworks within or adjacent to granitoid rocks but no economic deposits have been found. Chromite occurs in low concentrations within dunite and harzburgite of the Dun Mountain Ultramafics whereas copper (chalcopyrite) is present in quartz veins within Greenland Group greywacke, Permian sediments, and Devonian-Carboniferous granitoid.High-volatile bituminous coal is mined in the Buller and Reefton areas mainly from Eocene Brunner coal measures. Estimates of recoverable reserves indicate that these areas are likely to produce coal well into the next century. In the Murchison district, sub-bituminous coal from the Longford Formation has also been mined but most of the economic reserves are now exhausted. Traces of hydrocarbons are known from several areas within Sheet QM360, the most significant shows being in the Murchison area. Although the coal measures nearby provide potential source rocks, it is unlikely that significant economic reserves of oil and gas will be found as the structure of the area in general does not favour the retention of hydrocarbons. Resources of aggregate and limestone are abundant within Sheet QM 360 particularly east of the Alpine Fault. The limestone is quarried mostly from the Tertiary sequence whereas aggregate is derived chiefly from Torlesse Supergroup. At present rates of extraction, reserves of these commodities are virtually inexhaustable.