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Ohio Creek prospect (Ohio Stream), Tararu, Thames-Coromandel District, Waikato Region, North Island, New Zealand

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Latitude & Longitude (WGS84): 37° 6' 4'' South , 175° 33' 20'' East
Latitude & Longitude (decimal): -37.10127,175.55574
GeoHash:G#: rckufvgv3
Locality type:Creek
Köppen climate type:Cfb : Temperate oceanic climate

Cu-Au-Mo prospect.

Centred on, and named after Ohio Stream, 3 kilometres north north-east of Thames. Geological speaking the area covered by the prospect is poorly constrained, with some of the references also describing neighbouring historic gold mines, which will be listed separately where enough information is found.

The prospect occupies a jog in the Hauraki graben fault, shared with other deposits in the Thames area. Dextral rotation with associated plate rotation, produced a series of dilational fractures hosting sulphidation alteration of the Ohio Stream porphyry, with more distal auriferous mesothermal veins.

There is progressive alteration zoning north-west to south east covering propylitic (epidote-chlorite); intermediate argillic (chlorite-sericite); phyllic (sericite-quartz); advanced argillic (pyrophyllite-diaspore-quartz); silicified ledges with progressively more abundant alunite; argillic (dickite, kaolinite, illite); and low grade propylitic (chlorite, carbonate, illite).

The porphyry deposit and intrusive breccia is altered to a core of potassic K feldspar-magnetite-biotite, with surrounding propylitic quartz-chlorite and epidote-pyrite calcite alteration, both overprinted by quartz-sericite-pyrite or chlorite-sericite alteration.

Lookout Rocks on the north-east border of the prospect contains a narrow core zone of quartz-alunite-dickite grading outwards to an extensive pyrophyllite-dickite-diaspore-kaolinite zone, that overlaps the upper part of the phyllic alteration zone of the Ohio Stream porphyry Cu-Au-Mo deposit.

The dacite porphyry and surrounding the intrusion contains thin quartz-anhydrite-carbonate stock work veins containing disseminated sulphides such as pyrite, molybdenite, galena, sphalerite, tetrahedrite, and chalcopyrite. Mineralisation is overall low grade with 0.12-0.20% Cu, and 0.23-0.4 g/t Au, with a vertical extent greater than 600 metres. Other minerals present which are noted are magnetite, rutile, hematite, bornite, covellite, enargite.

The veins trend sub-parallel north-east across 4 x 2 kilometres contain ore assemblages of (1) quartz-pyrite-electrum-pyrargyrite locally bonanza grades; (2) quartz-sulphides-tellurides (Au, Ag, Bi).

Mineral List

26 valid minerals.

Rock Types Recorded

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Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

0 - 2.588 Ma

ID: 3187411
Cenozoic volcanic rocks

Age: Pleistocene (0 - 2.588 Ma)

Lithology: Ignimbrite(s); felsic volcanic rocks; rhyolite

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

5.333 - 23.03 Ma

ID: 1308094
Coromandel Group Miocene andesite and basaltic andesite lava

Age: Miocene (5.333 - 23.03 Ma)

Stratigraphic Name: Coromandel Group

Description: Andesite and basaltic andesite lava, tuff and tuff breccia, agglomerate and pyroclastic flow deposits; andesite, diorite and dacite dikes and subvolcanic intusions.

Comments: Zealandia Megasequence Extrusive and Intrusive Rocks (Neogene)

Lithology: Andesite, tuffite, tuff-breccia, agglomerate, pyroclastic material, andesite, diorite, dacite

Reference: Edbrooke, S.W., Heron, D.W., Forsyth, P.J., Jongens, R. (compilers). Geology Map of New Zealand 1:1 000 000. GNS Science Geological Map 2. [12]

Tortonian - Burdigalian
7.246 - 20.44 Ma

ID: 1315860
Kuaotunu Subgroup andesite and dacite (Coromandel Group) of Coromandel Volcanic Zone

Age: Miocene (7.246 - 20.44 Ma)

Stratigraphic Name: Kuaotunu Subgroup

Description: Basaltic andesite, andesite and dacite intrusives, flows, volcaniclastites and volcanic epiclastites.

Comments: Neogene igneous rocks. Age based on K-Ar

Lithology: Major:: {andesite},Minor:: {dacite}

Reference: Heron, D.W. . Geology Map of New Zealand 1:250 000. GNS Science Geological Map 1. [13]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Railton, G.T., Watters, W.A. (1990) Minerals of New Zealand. New Zealand Geological Survey Bulletin 104, 89 pages.
Corbett, G.J., Leach, T.M. (1996) South-West Pacific Rim Gold-Copper Systems: structure alteration and mineralization, Workshop Manual. Manual for an exploration short course presented in Philippines, November 1996.
Christie, A.B., Simpson, M.P., Brathwaite, R.L., Simmons, S.F. (2007) Epithermal Au-Ag and related deposits of the Hauraki Goldfield Coromandel Volcanic Zone New Zealand, Economic Geology, 102:5, 785-816.
Simpson, M.P., Mauk, J.L., Merchant, R. (2011) Bonanza grade epithermal veins from the Coromandel and Thames districts Hauraki Goldfield, Proceedings 2011 AusiMM New Zealand Branch Annual Conference, 27-30 August, Queenstown, New Zealand.
Christie, T., Brathwaite, B. Mineral Commodity Report 4- Copper, Institute of Geological and Nuclear Science Limited.

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