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Te Kopia geothermal area, Rotorua District, Bay of Plenty Region (Te Moana-a-Toi), North Island, New Zealand

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Latitude & Longitude (WGS84): 38° 23' 59'' South , 176° 13' 0'' East
Latitude & Longitude (decimal): -38.40000,176.21667
GeoHash:G#: rcjm9cmpc
Locality type:Area
Köppen climate type:Cfb : Temperate oceanic climate


A large and vigorously active geothermal area located in the Taupo Volcanic Zone.

Alkali-chloride waters discharged from hot pools and geysers recently as 3,000 years ago. Today surface thermal manifestations consist of boiling acid pools, small steam vents, mudpots and steaming ground, all typical of acid-sulfate thermal activity. The latest surface alteration event, now in progress, involves interaction of all the previously altered rocks by steam, gases and steam condensate to yield an assemblage initially dominated by kaolinite ± opal-A ± alunite ± alunogen (Martin et al., 2000)

The geothermal area is 39 kilometres south of Rotorua. Turn off State Highway 5 onto the Waikite Valley Road, then after 9 kilometres turn south onto Te Kopia Road, and travel another 8 kilometres.

The area is a conservation reserve, and collecting specimens is illegal.

The country rock is the Te Kopia Ignimbrite containing 1) lower hard dark grey rock, with much crystal fragments; 2) middle 50 foot thick member of chaotic tuff breccia, containing rhyolite and andesite blocks up to 5 feet across; 3) upper 90 foot thick member of black to brown shiny vitrophyre (volcanic rock with large crystals embedded in glassy groundmass), with a thin cover of dark grey tuff.

The geothermal area has been active for 120,000 years. Much of the literature is about how steam and acid sulphate water is altering further the ignimbrite rocks, as noted above. The site has been extensively written about with some describing alunogen, meta-alunogen, and alunite, all closely related, as well as some silica, all with similar physical location descriptions. Silica, opaline silica, quartz, opal-A, opal-C, hyalite, and chalcedony described in several references probably needs pictures for the reader to gain a clear understanding of the differences of each at the location.

(Martin, et. al., 1999) Alunogen and meta-alunogen form white fibrous tangled masses, consisting of thin micro platy crystals. Meanwhile steam condensate forms alunogen and tamarugite efflorescence. Minor constituents include potash alum, and halotrichite-pickeringite (and several other 'possible' species).

(Bignall, 1994) Surface alteration to kaolin, cristobalite, alunite, hematite, and jarosite. In the 1960's some deep drill holes were sunk at the geothermal area, and under 500 metres depth the alteration was quartz-albite-adularia, with variable amounts of chlorite, pyrite, calcite, wairakite, epidote, pyrrhotite, titanate, leucoxene, sericite, clinozoisite, illite, and rare almandine. (Noted for interest, but species not added to Mindat due to depth). Mordenite is noted in cooler areas (?).

(Cook, et. al., 2000) describes silica alteration as rinds, botryoidal loaves, and recemented crusts, caused by steam with acid sulphate fluids corroding the rocks. The silica forms opal-A and hyalite (and morganite?). The rind silica is described as a 3 mm layer of white glistening silica coating ignimbrite boulders, often discoloured from iron oxides and biological matter. Some is also viewed as water clear hyalite. Crustose silica is described unflattering as scab-like, grey to off white opaline crusts up to 5 mms thick, sometime crudely layered, and containing sometimes quartz crystals below the layers. Loaf silica is masses of dense white translucent botryoidal silica up to 20 mms thick, with a thin hyalite layer, resembling 'frog spawn', below the ground surface, and immediately above clay red hematite stained ignimbrite. Also noted is spheroid chalcedony 0.5-2 mms, and under 1 mm framboidal pockets of pyrite clusters. Leucoxene is added to the expanding list of alteration minerals in ignimbrite.

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List


13 valid minerals.

Detailed Mineral List:

Alunite
Formula: KAl3(SO4)2(OH)6
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Alunogen
Formula: Al2(SO4)3 · 17H2O
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
'Halotrichite-Pickeringite Series'
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Hematite
Formula: Fe2O3
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Kalinite
Formula: KAl(SO4)2 · 11H2O
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Kaolinite
Formula: Al2(Si2O5)(OH)4
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Melanterite
Formula: Fe2+(H2O)6SO4 · H2O
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Meta-alunogen
Formula: Al2(SO4)3 · 12H2O
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Mirabilite
Formula: Na2SO4 · 10H2O
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Opal
Formula: SiO2 · nH2O
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Opal var: Opal-C
Formula: SiO2 · nH2O
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Quartz
Formula: SiO2
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Sulphur
Formula: S8
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Tamarugite
Formula: NaAl(SO4)2 · 6H2O
Reference: Mackenzie, K.M., Rodgers, K.A., Browne, P.R.L. (1995) Tamarugite, NaAl(SO₄)₂·6H₂O, from Te Kopia, New Zealand. Mineralogical Magazine 59:4, 754-757.
Tschermigite
Formula: (NH4)Al(SO4)2 · 12H2O
Reference: Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.

List of minerals arranged by Strunz 10th Edition classification

Group 1 - Elements
Sulphur1.CC.05S8
Group 4 - Oxides and Hydroxides
'Hematite'4.CB.05Fe2O3
'Opal'4.DA.10SiO2 · nH2O
var: Opal-C4.DA.10SiO2 · nH2O
Quartz4.DA.05SiO2
Group 7 - Sulphates, Chromates, Molybdates and Tungstates
'Alunite'7.BC.10KAl3(SO4)2(OH)6
'Alunogen'7.CB.45Al2(SO4)3 · 17H2O
'Kalinite'7.CC.15KAl(SO4)2 · 11H2O
'Melanterite'7.CB.35Fe2+(H2O)6SO4 · H2O
'Meta-alunogen'7.CB.45Al2(SO4)3 · 12H2O
'Mirabilite'7.CD.10Na2SO4 · 10H2O
Tamarugite7.CC.10NaAl(SO4)2 · 6H2O
Tschermigite7.CC.20(NH4)Al(SO4)2 · 12H2O
Group 9 - Silicates
'Kaolinite'9.ED.05Al2(Si2O5)(OH)4
Unclassified Minerals, Rocks, etc.
'Halotrichite-Pickeringite Series'-

List of minerals arranged by Dana 8th Edition classification

Group 1 - NATIVE ELEMENTS AND ALLOYS
Semi-metals and non-metals
Sulphur1.3.5.1S8
Group 4 - SIMPLE OXIDES
A2X3
Hematite4.3.1.2Fe2O3
Group 29 - HYDRATED ACID AND NORMAL SULFATES
A2XO4·xH2O
Mirabilite29.2.2.1Na2SO4 · 10H2O
AB(XO4)2·xH2O
Kalinite29.5.4.2KAl(SO4)2 · 11H2O
Tamarugite29.5.3.1NaAl(SO4)2 · 6H2O
Tschermigite29.5.5.3(NH4)Al(SO4)2 · 12H2O
AXO4·xH2O
Melanterite29.6.10.1Fe2+(H2O)6SO4 · H2O
A2(XO4)3·H2O
Alunogen29.8.6.1Al2(SO4)3 · 17H2O
Meta-alunogen29.8.7.1Al2(SO4)3 · 12H2O
Group 30 - ANHYDROUS SULFATES CONTAINING HYDROXYL OR HALOGEN
(AB)2(XO4)Zq
Alunite30.2.4.1KAl3(SO4)2(OH)6
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Quartz75.1.3.1SiO2
Si Tetrahedral Frameworks - SiO2 with H2O and organics
Opal75.2.1.1SiO2 · nH2O
Unclassified Minerals, Rocks, etc.
'Halotrichite-Pickeringite Series'-
Kaolinite-Al2(Si2O5)(OH)4
Opal
var: Opal-C
-SiO2 · nH2O

List of minerals for each chemical element

HHydrogen
H AluniteKAl3(SO4)2(OH)6
H AlunogenAl2(SO4)3 · 17H2O
H KaliniteKAl(SO4)2 · 11H2O
H KaoliniteAl2(Si2O5)(OH)4
H MelanteriteFe2+(H2O)6SO4 · H2O
H Meta-alunogenAl2(SO4)3 · 12H2O
H MirabiliteNa2SO4 · 10H2O
H OpalSiO2 · nH2O
H Opal (var: Opal-C)SiO2 · nH2O
H TamarugiteNaAl(SO4)2 · 6H2O
H Tschermigite(NH4)Al(SO4)2 · 12H2O
NNitrogen
N Tschermigite(NH4)Al(SO4)2 · 12H2O
OOxygen
O AluniteKAl3(SO4)2(OH)6
O AlunogenAl2(SO4)3 · 17H2O
O HematiteFe2O3
O KaliniteKAl(SO4)2 · 11H2O
O KaoliniteAl2(Si2O5)(OH)4
O MelanteriteFe2+(H2O)6SO4 · H2O
O Meta-alunogenAl2(SO4)3 · 12H2O
O MirabiliteNa2SO4 · 10H2O
O OpalSiO2 · nH2O
O Opal (var: Opal-C)SiO2 · nH2O
O QuartzSiO2
O TamarugiteNaAl(SO4)2 · 6H2O
O Tschermigite(NH4)Al(SO4)2 · 12H2O
NaSodium
Na MirabiliteNa2SO4 · 10H2O
Na TamarugiteNaAl(SO4)2 · 6H2O
AlAluminium
Al AluniteKAl3(SO4)2(OH)6
Al AlunogenAl2(SO4)3 · 17H2O
Al KaliniteKAl(SO4)2 · 11H2O
Al KaoliniteAl2(Si2O5)(OH)4
Al Meta-alunogenAl2(SO4)3 · 12H2O
Al TamarugiteNaAl(SO4)2 · 6H2O
Al Tschermigite(NH4)Al(SO4)2 · 12H2O
SiSilicon
Si KaoliniteAl2(Si2O5)(OH)4
Si OpalSiO2 · nH2O
Si Opal (var: Opal-C)SiO2 · nH2O
Si QuartzSiO2
SSulfur
S AluniteKAl3(SO4)2(OH)6
S AlunogenAl2(SO4)3 · 17H2O
S KaliniteKAl(SO4)2 · 11H2O
S MelanteriteFe2+(H2O)6SO4 · H2O
S Meta-alunogenAl2(SO4)3 · 12H2O
S MirabiliteNa2SO4 · 10H2O
S SulphurS8
S TamarugiteNaAl(SO4)2 · 6H2O
S Tschermigite(NH4)Al(SO4)2 · 12H2O
KPotassium
K AluniteKAl3(SO4)2(OH)6
K KaliniteKAl(SO4)2 · 11H2O
FeIron
Fe HematiteFe2O3
Fe MelanteriteFe2+(H2O)6SO4 · H2O

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Bignall, G. (1994) Thermal evolution and fluid-rock interactions in the Orakeikorako-Te Kopia geothermal system, Taupo Volcanic Zone, New Zealand. (unpublished PhD thesis), University of Auckland.
Mackenzie, K.M., Rodgers, K.A., Browne, P.R.L. (1995) Tamarugite, NaAl(SO₄)₂·6H₂O, from Te Kopia, New Zealand. Mineralogical Magazine 59:4, 754-757.
Martin, R.C. (1996) Stratigraphy and structural outline of the Taupo Volcanic Zone. New Zealand Journal of Geology and Geophysics, 4:4, p462.
Martin, R., Rodgers, K.A., Browne, P.R.L. (1999) The nature and significance of sulphate-rich, aluminous efflorescences from the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical Magazine, June 1999, Vol. 63(3), 413-419.
Martin, R., Rodgers, K.A., Browne, P.R.L. (2000) Aspects of the distribution and movement of aluminium in the surface of the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand. Applied Geochemistry 15:8, 1121-1136.
Bignall, G., Sekine, K., Tsuchiya, N. (2004) Fluid rock interaction processes in the Te Kopia geothermal field (New Zealand) revealed by SEM-CL imaging. Geothermics, 33, 615-635.

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