Brathwaite, R.L.; Meshesha, M.Y.; Wyss, R.J.; Brown, L.J.; Baker, J.A.; Petty, D.R. 1991 Geological resource map of New Zealand 1:250 000 : sheet QM 261 Waitangi. Lower Hutt: DSIR Geology & Geophysics. New Zealand Geological Survey report M 181. 68 p.
Abstract
Permian-Jurassic Waipapa Group greywacke is the major source of aggregate in the sheet QM261 area, although considerable quantities of basalt from the Kerikeri Volcanic Group and the Tangihua Complex are also quarried. Large resources of limestone are present and are extracted for use in cement manufacture, agricultural top-dressing, and road aggregate. There are extensive resources of sand in onshore and offshore barrier and bar deposits along the east and west coasts of the sheet area. A large volume (65 000 cubic metres / year) of sand is dredged from a longshore bar between Mangawhai and Pakiri for use as a building material. Hydrothermally-altered Pliocene rhyolite at Matauri Bay and Mangaparerua is mined for high quality halloysite clay which is mainly exported for manufacture of fine table china. Other nonmetallic resources such as diatomite, kauri gum and serpentinite have been worked in the past. Small deposits of copper, mercury, manganese, limonite, antimony and silver have been mined in the past. Potentially economic mercury deposits at Huia and Doar have yet to be developed. Copper deposits comprise massive sulphide lenses in the Cretaceous Tangihua Complex and porphyry-style mineralisation in Miocene dioritic intrusives. Hot spring epithermal sinters, silicified zones and hydrothermal breccias host small deposits of mercury, antimony and silver, and have been prospected unsuccessfully for epithermal gold in recent years. Small stratabound manganese deposits are associated with chert, volcanic argillite and spilitic volcanics in the Waipapa Group. Zinc-lead skarn mineralisation has been found in Oligocene limestone at Motukokako (Piercy) Island. Subeconomic bauxite deposits occur in the Kerikeri area. Five coal deposits have been mined, and a number of small deposits of lignite and peat are also present. Petroleum exploration has been unsuccessful so far, and is constrained by a considerable thickness of structurally complex, allochthonous Cretaceous-lower Tertiary sediments. (auth)
