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Mangatutu Stream prospect, Hicks Bay, Gisborne Region, North Island, New Zealand

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Latitude & Longitude (WGS84): 37° 37' 23'' South , 178° 14' 3'' East
Latitude & Longitude (decimal): -37.62310,178.23443
Köppen climate type:Cfb : Temperate oceanic climate

Uneconomic base metal prospect.

The New Zealand Geological Survey department discovered boulders containing sulphides in the middle reaches of Mangatutu Stream, 2 kilometres south-west of Hicks Bay. The stream is deeply incised into the ranges, and heavily forested, with no access; the nearest being State Highway 35, 1.5 kilometres away.

The main ores are marcasite, chalcopyrite and pyrite, assaying up to 8.5% Cu.
The geology of the area consists of basaltic pillow lavas, and volcanogenic breccias of the Matakoa Volcanic Group, with minor diorite and gabbro intrusive bodies.

The pillow lava, and rare massive lava is fine grained, dark grey basalts, with rare vesicles. Pyrite was found commonly coating these rocks, and infilling joints, with veins up to 10 metres long. The veins consisted of chabazite, laumonite, natrolite, quartz, and calcite. Also noted are calcite, pyrite, and a glassy material as veinlets. In thin section, phenocrysts consisted of augite, zoned labradorite, in a matrix of plagioclase laths, small augite crystals, magnetite, smectite, and chlorite.

The gabbro dykes contain plagioclase, augite edged with green-pale yellow actinolite, pseudomorphs after olivine, titanomagnetite, ilmenite, pyrite, and rare chalcopyrite.

Also found in the stream is ferruginous rounded diorite boulders 10-20 cms in diameter, light grey, with disseminated pyrite grains. Thin sections show quartz, oligoclase crystals, secondary crystalline pyrite, sericite, and alteration products nontronite, beidellite, smectite.

The breccia member is a massive 200 metre thick fine dark grey basalt, with volcanic glass and smectite.

The sulphide rich samples are up to 0.5 metre diameter boulders in the stream, of brecciated marcasite, chalcopyrite, and pyrite in a chalcedonic matrix. Some of the chalcopyrite has altered to covellite and chalcocite. There is also minor pyrrhotite, and rare sphalerite.

Mineral List

18 valid minerals.

Rock Types Recorded

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Alphabetical List Tree Diagram

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

Eocene - Cretaceous
33.9 - 145 Ma

ID: 1311086
Matakoa Volcanics

Age: Phanerozoic (33.9 - 145 Ma)

Stratigraphic Name: Matakoa Volcanics

Description: Basaltic pillow lava, igneous breccia and tuff with subvolcanic intrusive basalt, dolerite and gabbro; minor intercalated sandstone, mudstone, limestone and chert.

Comments: Zealandia Megasequence Allochthonous Rocks

Lithology: Basalt, breccia, tuffite, dolerite, gabbro, sandstone, mudstone, limestone, chert

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]

Danian - Cenomanian
61.6 - 100.5 Ma

ID: 1323503
Undifferentiated Matakoa Volcanic Group basalt in East Coast Allochthon

Age: Phanerozoic (61.6 - 100.5 Ma)

Stratigraphic Name: Matakaoa Volcanic Group

Description: Pillows and dikes of basalt, gabbro, minor sedimentary intercalations.

Comments: Allochthonous rocks

Lithology: Major:: {basalt},Minor:: {breccia, tuff}

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

Cretaceous - Jurassic
66 - 201.3 Ma

ID: 3190658
Mesozoic sedimentary and volcanic rocks

Age: Mesozoic (66 - 201.3 Ma)

Lithology: Mafic volcanic rocks; greywacke,limestone,tuffaceous sandstone,argillite,chert

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]

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.


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Cody, A.D., Grammer, T.R. (1981) Geochemical survey of stream sediments Pukeamaru Range East Cape, New Zealand Journal of Geology and Geophysics, 24:1, 21-29.

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