Port Chalmers, Dunedin City, Otago Region, New Zealandi
| Regional Level Types | |
|---|---|
| Port Chalmers | - not defined - |
| Dunedin City | City |
| Otago Region | Region |
| New Zealand | Country |
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Latitude & Longitude (WGS84):
45° 49' 8'' South , 170° 37' 23'' East
Latitude & Longitude (decimal):
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Portobello | 1,200 (2012) | 4.0km |
| Waitati | 534 (2011) | 8.8km |
| Dunedin | 114,347 (2017) | 11.1km |
| Warrington | 427 (2011) | 11.8km |
| Karitane | 427 (2015) | 20.1km |
Port Chalmers is the container port for Dunedin, on Otago harbour.
The very detailed geology source for the Port Chalmers area, indicates bohmite listed on Mindat, is minor compared to the overall geology. It is not a noted specimen location, although interesting rocks occur. Space allows only species to be listed.
Port Chalmers is near the centre of a Miocene aged complex shield volcano. The area surrounding Port Chalmers shows the earliest rocks from the initial eruption being 230 metre thick basalt flows, overlain by trachyte and trachyte agglomerate 100-250 metres thick, overlain by further basalt flows 190-290 metre thick, and finally phonolitic trachyte. These abut the Port Chalmers Breccia which fills the eruptive vent.
The basal basalt flow shows as weathered red and purple basalt, with fresh basalt containing plagioclase, olivine, brown amphibole, and titanaugite, as well as phenocrysts of labradorite, titanaugite, and minor olivine.
Above this is interlayered flows and agglomerates, most a white trachy anorthoclase phenocrysts in a ground mass of partially exsolved alkali feldspar laths, with minor hornblende, quartz, and pale pinkish-brown opal.
Overlying this is alkali basalt, or alkali olivine basalt flows, containing olivine, labradorite, titanaugite, and titanomagnetite. To the west of Careys Bay this section contains sparse phenocrysts of very pale lilac titanaugite, and olivine is a ground mass of andesine, faint green clinopyroxene, some hydro altered to a soft white mix of quartz, feldspar and kaolinite. Sepiolite as an intermediate alteration stage is found just north of Leans Rock.
The highest in the sequence is phonolitic trachyte, showing as sparse phenocrysts of clinopyroxene in a ground mass of sanidine microlites, and sodic clinopyroxene, with interstitial aenigmatite.
The vent shows calcite and kaolinite cemented breccia, with dark green dominant phonolite, as well as basalt, basanite, trachyandesite, phonolitic trachyte, and minor basement schist fragments intermixed. The vent covers an area 1.3 by 2.5 kilometres, elongated north-east to south-west. The breccia is underlain by phonolite, dolerite, and a trachyandesite dyke. The phonolite is pale green, with mafic minerals, and nepheline replaced by green montmorillonite, carbonate and mica, streaked with analcime, and minor water clear albite. The dyke contains kaersutite crystals, plus titanaugite both partly replaced by pale green clinopyroxene, stumpy very pale pink apatite crystals, with abundant inclusions, and second generation much smaller acicular apatite crystals. The schist contains a variety of species including quartz, muscovite, chlorite, calcite, biotite, garnet, epidote, and albite. The upper levels of the vent is dominated by plagioclases, brown amphibole, nepheline, alkali feldspar, clinopyroxene, kersantite, and camptonite.
The author notes five blocks of peralkaline nepheline sodalite syenites, one containing the rare zirconian silicate eucolite, being the first record of the species in New Zealand. The syenite blocks contain sodic orthoclase, nepheline, sodalite, aergirine-augite, katophorite, pyrite, pyrrhotite, biotite, sphene, and apatite. Secondary alteration shows as patches of analcime, dolomite, bohmite, and fibrous gibbsite. The eucolite occurs as erratic disseminated stumpy crystals, less than 2 mms long, with much inclusions of the groundmass.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsDetailed Mineral List:
| ⓘ Böhmite Formula: AlO(OH) |
| ⓘ 'Eudialyte Group' Formula: [N(1)N(2)N(3)N(4)N(5)]3[M(1.1)M(1.2)]3[M(2.1)M(2.2)M(2.3)]3-6[M(3)M(4)]Z3[Si24O72]Θ4X(1)X(2) |
| ⓘ 'Eudialyte Group var. Eucolite' Formula: [N(1)N(2)N(3)N(4)N(5)]3[M(1.1)M(1.2)]3[M(2.1)M(2.2)M(2.3)]3-6[M(3)M(4)]Z3[Si24O72]Θ4X(1)X(2) |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 4 - Oxides and Hydroxides | |||
|---|---|---|---|
| ⓘ | Böhmite | 4.FE.15 | AlO(OH) |
| Unclassified | |||
| ⓘ | 'Eudialyte Group var. Eucolite' | - | [N(1)N(2)N(3)N(4)N(5)]3[M(1.1)M(1.2)]3[M(2.1)M(2.2)M(2.3)]3-6[M(3)M(4)]Z3[Si24O72]Θ4X(1)X(2) |
| ⓘ | '' | - | [N(1)N(2)N(3)N(4)N(5)]3[M(1.1)M(1.2)]3[M(2.1)M(2.2)M(2.3)]3-6[M(3)M(4)]Z3[Si24O72]Θ4X(1)X(2) |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Böhmite | AlO(OH) |
| O | Oxygen | |
| O | ⓘ Böhmite | AlO(OH) |
| O | ⓘ Eudialyte Group var. Eucolite | [N(1)N(2)N(3)N(4)N(5)]3[M(1.1)M(1.2)]3[M(2.1)M(2.2)M(2.3)]3-6[M(3)M(4)]Z3[Si24O72]Θ4X(1)X(2) |
| O | ⓘ Eudialyte Group | [N(1)N(2)N(3)N(4)N(5)]3[M(1.1)M(1.2)]3[M(2.1)M(2.2)M(2.3)]3-6[M(3)M(4)]Z3[Si24O72]Θ4X(1)X(2) |
| Al | Aluminium | |
| Al | ⓘ Böhmite | AlO(OH) |
| Si | Silicon | |
| Si | ⓘ Eudialyte Group var. Eucolite | [N(1)N(2)N(3)N(4)N(5)]3[M(1.1)M(1.2)]3[M(2.1)M(2.2)M(2.3)]3-6[M(3)M(4)]Z3[Si24O72]Θ4X(1)X(2) |
| Si | ⓘ Eudialyte Group | [N(1)N(2)N(3)N(4)N(5)]3[M(1.1)M(1.2)]3[M(2.1)M(2.2)M(2.3)]3-6[M(3)M(4)]Z3[Si24O72]Θ4X(1)X(2) |
Other Regions, Features and Areas containing this locality
Australian Plate
- Haast SchistAccretionary Complex
New Zealand
- South IslandIsland
- Southern AlpsMountain Range
Pacific PlateTectonic Plate
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