Mangatutu Stream prospect, Hicks Bay, Gisborne Region, North Island, New Zealand
|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.
18 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
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 Macrostrat.org
|Eocene - Cretaceous|
33.9 - 145 Ma
Age: Phanerozoic (33.9 - 145 Ma)
Stratigraphic Name: Matakoa Volcanics
Comments: Zealandia Megasequence Allochthonous Rocks
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. 
|Danian - Cenomanian|
61.6 - 100.5 Ma
|Undifferentiated Matakoa Volcanic Group basalt in East Coast Allochthon|
Age: Phanerozoic (61.6 - 100.5 Ma)
Stratigraphic Name: Matakaoa Volcanic Group
Comments: Allochthonous rocks
Reference: Heron, D.W. . Geology Map of New Zealand 1:250 000. GNS Science Geological Map 1. 
|Cretaceous - Jurassic|
66 - 201.3 Ma
|Mesozoic sedimentary and volcanic rocks|
Age: Mesozoic (66 - 201.3 Ma)
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.