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
  • Khanneshin
• China :
  • Miaoya , Hubei
• Germany :
  • Kaiserstuhl
• Finland
  • Naantali
• 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

The Monte Vulture

• Italy :
  • Monte Vulture
  • Polino
• Cape Verde
  • Brava (Santa Bárbara)
• Kenya :
  • Mount Homa
  • Nyanza
  • Ruri
  • Tinderet
• Morocco :
  • Tamazeght near Midelt , High Atlas
• Namibia :
  • Fat Willem
• Paraguay :
  • Chiriguelo
• Zambia :
• Sweden :
  • Alnön (type locality)
• South Africa :
  • Kruidfontein
• Tanzania :
  • Panda Hill
  • Rungwa
• United States of America :
  • Arkansas :
    • Brazil Branch , Morrilton Dam , Oppelo and Perryville
    • Potash Sulfur Springs

Individual evidence

1. ^ 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 .
2. ↑ 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.
3. ^ Keller, J .: Geochemistry and Magma Development in the Kaiserstuhl . In: Advances in Mineralogy . 62 (Supplement I), 1984, p. 116-118 .
4. ↑ 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 .
5. ↑ 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 .
6. ↑ 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 .
7. ^ 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 .
8. ↑ Kresten, P .: Alnöområdet . Ed .: Lundqvist, T .: Beskrivning till berggrundskartan över västernorrlandslän. ser Ba 31. Sveriges geologiska undersökening, 1990, p. 238-278 .
9. ^ McCormick, GR and Heathcote, RC: Mineral chemistry and petrogenesis of carbonatite intrusions . In: American Mineralogist . Vol. 72, 1987, pp. 59-66 .
10. ^ 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 .