Alvikite
Alvikite is a medium to fine-grain igneous rock that is counted among the carbonatites . Together with its coarse-grained equivalent Sövit it forms the rock group of calcite carbonatites .
etymology
Alvkit was named after its type of locality , the town of Alvik on the Swedish island of Alnön ( Västernorrland ).
Initial description
Alvikite was scientifically described for the first time in 1942 by H. von Eckermann.
mineralogy
The main mineral of alvikite is by definition calcite , which is represented with more than 50 percent by volume. Secondary components are anchorite , apatite , clinopyroxene ( aegirine-augite ), magnetite and quartz , additional fluorite and sulfide minerals (such as pyrite , chalcopyrite and galena ), occasionally allanite , biotite , chlorite , garnet (titanium-rich), monazite , phlogopite , Pyrochlore , titanite and wollastonite . Post Magma table appear apatite, barite , dolomite , orthoclase , Parisit , rhodochrosite , Strontianit and Synchisit .
Varieties
The following types of gangue rock are known from alvikite :
- Barite-anchorite-alvikite
- Apatite-alvikite
- Biotite-alvikite
- Feldspar-Biotite-Alvikite
- Pyroxene-Biotite-Alvikite
- Chlorite-alvikite
- Feldspar-Alvikite
- Fluorite-alvikite
- Picrite-alvikite (with olivine pseudomorphoses)
- Strontianite-Alvikite
- Biotite-wollastonite-alvikite
Chemical composition
The following table is intended to clarify the chemical composition of alvikites:
Weight% | Average alvikite | Average Alvikite Kenya |
Alnön type locality |
Kaiserstuhl edge zone |
Kaiserstuhl central zone |
Amba Dongar I. | Amba Dongar II | Naantali |
SiO 2 | 1.50 | 0.88 | 1.01 | 2.27 | 1.09 | 3.65 | 4.11 | 8.84 |
TiO 2 | 0.07 | 0.18 | 0.06 | 0.09 | 0.00 | 0.09 | 0.17 | 0.01 |
Al 2 O 3 | 0.18 | 1.40 | 0.23 | 0.88 | 0.17 | 0.75 | 0.07 | 1.84 |
Fe 2 O 3 | 2.70 | 4.21 | 3.83 | 4.59 | 0.91 | 1.84 | 5.19 | 0.80 |
MnO | 0.57 | 0.65 | 1.12 | 0.45 | 0.46 | 0.28 | 0.84 | 0.07 |
MgO | 0.58 | 0.38 | 0.88 | 1.28 | 0.31 | 0.75 | 0.50 | 0.94 |
CaO | 49.40 | 50.83 | 49.02 | 47.50 | 52.20 | 49.42 | 45.08 | 49.10 |
Na 2 O | 0.13 | 0.48 | 0.14 | 0.03 | 0.00 | 0.16 | 0.07 | 0.08 |
K 2 O | 0.08 | 0.04 | 0.13 | 0.05 | 0.00 | 0.37 | 0.03 | 0.18 |
P 2 O 5 | 0.66 | 1.02 | 0.69 | 1.98 | 1.23 | 0.87 | 1.01 | 1.36 |
CO 2 | 39.85 | 37.57 | 41.66 | 37.30 | 41.10 | 40.48 | 38.43 | 35.94 |
BaO | 0.54 | 0.46 | 0.60 | 0.08 | 0.10 | 0.30 | 0.84 | 0.01 |
SrO | 0.26 | 0.15 | 0.01 | 0.77 | 0.80 | 0.07 | 0.61 | 0.21 |
geochemistry
Alvikites differ from Sövites not only in grain size, but also geochemically . Compared to Söviten, they generally have a higher content of rare earths , but show a depletion of strontium .
Deposits
Alvikites are associated with deposits of rare earths , but also for fluorite such as Amba Dongar in India and for phlogopite (Barra in India).
Occurrence
- Afghanistan
- China :
- Germany :
- Finland
-
India :
- Amba Dongar , Gujarat - Campanium to Selandium and Bartonium - 76 ± 2 to 61 ± 2 million years BP and 37.5 ± 2.5 million years BP
- Barra - Calymmium - 1490 million years BP
- Danta - Langera - Mahabar - Tertiary
- Kamthai
- Mahadwa - Bhagdari
- Mundwara , Rajasthan
- Munnar , Kerala
- Panwad - Kawant , Gujarat
- Samalpatti
- Sarnu - Dandali
- Sung Valley , Meghalaya - Turonian to Santonian - 90 ± 10 to 84 ± 13 million years BP
- Vinjamur
- Italy :
-
Cape Verde
- Brava (Santa Bárbara)
- Kenya :
-
Morocco :
- Tamazeght near Midelt , High Atlas
- Namibia :
- Paraguay :
- Zambia :
-
Sweden :
- Alnön (type locality)
- South Africa :
- Tanzania :
- United States of America :
Individual evidence
- ^ Von Eckermann, H .: Ett preliminär meddelande om nya forskningsrön inom Alnö alkalina omrade . In: Geologiska Föreningens i Stockholm Förhandlingar, Stockholm . Vol. 64, 1942, pp. 399-455 .
- ↑ Ayuso, R. et al .: Preliminary radiogenic isotope study on the origin of the Khanneshin carbonatite complex, Helmand Province, Afghanistan . In: Journal of Geochemical Exploration . 2013.
- ^ Keller, J .: Geochemistry and Magma Development in the Kaiserstuhl . In: Advances in Mineralogy . 62 (Supplement I), 1984, p. 116-118 .
- ↑ Woodard, J. and Hölttä, P .: The Naantali alvikite vein-dykes: a new carbonatite in southwestern Finland . In: Geological Survey of Finland Special Paper . tape 38 , 2005, p. 5-10 .
- ↑ Santosh, M. et al .: Rare Earth Element Geochemistry of the Munnar Carbonatite, Central Kerala . In: Journal Geological Society of India . Vol. 29, 1987, pp. 335-343 .
- ↑ Stoppa, F. et al .: Texture and mineralogy of tuffs and tuffisites at Ruri Volcano in western Kenya: a carbonatite, melilitite mantle-debris trio . In: Periodico di Mineralogia . tape 72 , 2003, p. 1-24 .
- ^ Cooper, AF and Reid, DL: Nepheline Sövites as Parental Magmas in Carbonatite Complexes: Evidence from Dicker Willem, Southwest Namibia . In: Journal of Petrology . Vol. 39, 1998, pp. 2123-2136 .
- ↑ Kresten, P .: Alnöområdet . Ed .: Lundqvist, T .: Beskrivning till berggrundskartan över västernorrlandslän. ser Ba 31. Sveriges geologiska undersökening, 1990, p. 238-278 .
- ^ McCormick, GR and Heathcote, RC: Mineral chemistry and petrogenesis of carbonatite intrusions . In: American Mineralogist . Vol. 72, 1987, pp. 59-66 .
- ^ Heathcote, RC and McCormick, GR: Major-cation substitution in phlogopite and evolution of carbonatites in the Potash Sulfur Springs complex, Garland County, Arkansas . In: American Mineralogist . Vol. 74, 1989, pp. 132-140 .