Kirwan's Hill Tungsten Prospect, Reefton, Buller District, West Coast Region, South Island, New Zealand
| Latitude & Longitude (WGS84): | 42° 1' 33'' South , 172° 0' 9'' East |
|---|---|
| Latitude & Longitude (decimal): | -42.02609,172.00264 |
| KΓΆppen climate type: | Cfb : Temperate oceanic climate |
Scheelite mineralisation on the upper flanks of Kirwan's Hill.
Explored by Western Australian junior exploration company Siburan, from 2013 to 2017. Drilling was conducted and three old adits re-discovered, cleaned out and sampled. Eternally optimistic, the company (Siburan 2013) stated 'We see this phase as a turning point in our company's future'. Siburan abandoned the leases early 2017, with no clear picture of the extent of the mineralisation, blaming low world tungsten prices.
Scheelite is found in two sheeted quartz vein systems, and to a lesser extent disseminated in surrounding coarse sandstone units, as part of the Shaw-Drysdale Fracture Zone, hosted by the Greenland Group metasedimentary rocks. There is an absence of wolframite. The two fissure quartz vein systems, are several hundred metres wide, 600 to 1000 metres in strike. Individual quartz veins are 0.01 to 0.2 metres thick.
The mineralisation is thought to have formed from a hydrothermal heat source, with thermal metamorphism, emplacing a quartz fissure system, with associated mineralisation.
The quartz veins contain scheelite, and minor tourmaline, fluorite, apatite, orthoclase, late stage pyrite, cross cut by carbonate veinlets, and hematite. Ore mineralisation in the veins consist of scheelite, pyrrhotite, chalcopyrite, pyrite, arsenopyrite, loellingite, with minor sphalerite, molybdenite, cassiterite, Ag-Pb-Bi sulphosalts, supergene covellite, bornite and tungstite.
Scheelite forms anhedral grains up to 30 mms in length, with an erratic distribution, but confined to vein margins with muscovite. Pyrrhotite is intergrown with chalcopyrite, while pyrite is associated with pyrrhotite, and in places rims scheelite grains. A second phase of pyrite is replaced by loellingite, which may also replace pyrrhotite and chalcopyrite. Uncommon sphalerite is found as inclusions in chalcopyrite, or infilling of microfractures with other sulphides. Local cassiterite grains are associated with scheelite.
Low level anomalous copper and gold was found. The historic Kirwan's Reward gold mine, where high grade gold was recovered from loose boulders is several hundred meters to the south.
Mineralisation in the envelope surrounding the quartz veins is biotite, tourmaline, muscovite, phlogopite, clinozoisite, pyrrhotite, and scheelite. The tourmaline is mid-way between schorl and dravite. Pyrrhotite with chalcopyrite is pervasive within 30 cms of the quartz vein margins.
Mineral List
21 valid minerals.
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 Macrostrat.org
| Mississippian - Devonian 323.2 - 419.2 Ma ID: 1308019 | Karamea Suite Devonian-Carboniferous felsic intrusive rocks Age: Paleozoic (323.2 - 419.2 Ma) Stratigraphic Name: Tuhua Intrusives; Karamea Suite; Karamea Suite Devonian-Carboniferous felsic intrusive rocks Description: Granite, granodiorite, tonalite and diorite; locally foliated to gneissic. Comments: Western Province (Tuhua Intrusives) Rocks Lithology: Granite, granodiorite, tonalite, diorite, orthogneiss 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] |
| Famennian - Frasnian 358.9 - 382.7 Ma ID: 1362276 | Dunphy Granite (Karamea Suite) Age: Late Devonian (358.9 - 382.7 Ma) Stratigraphic Name: Karamea Batholith; Karamea Suite; Dunphy Granite Description: Leucocratic muscovite-biotite granite with K-feldspar megacrysts. Comments: Basement (Karamea Batholith) igneous rocks. Age based on U-Pb zircon Muir et al, Tulloch unpublished Lithology: Major:: {granite} Reference: Heron, D.W. . Geology Map of New Zealand 1:250 000. GNS Science Geological Map 1. [13] |
Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License
References
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