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Article Evaluation
[edit]The page on Alkali Basalt is currently very short. All the information seems to be relevant, as the article presents the characterization of the Alkali Basalt, chemical composition in comparison to other basalts, and notable visual aspects. The article also includes some geographic locations where the Alkali Basalt can be found. Overall, the presentation seems scientific and accurate, though the language seems to be a little too context-specific, making it difficult to read for an audience unfamiliar with geology or volcanology. The article links to many other Wikipedia articles for related topics and definitions.
The tone is descriptive and neutral, as it should be.
There is only one cited reference, which links to a page that is unavailable because of a cyber attack. Thus, in practice, the article has no references, which is an issue.
The talk page is also short. The main discussion is a claim of possible plagiarism from 2015, but the editors seem to have concluded that in fact the author of the textbook plagiarized wikipedia, and not the other way around. The article was rated a stub for quality and of mid-importance for the WikiProject it is a part of, which is WikiProject Volcanoes.
(Initial) Bibliography for Alkali Basalt article
[edit]This is a list of references I think are going to be useful in improving the Alkali Basalt article. This is not an exhaustive list, but a starting point. Along the way I might come upon others that complement or even replace these references. For instance, all of these are from peer-reviewed journals, but I think textbook sources would also be nice to have. (If you have any comments about these references, of suggestions of other references I should check out, please let me know!)
Fitton, J. G.; Dunlop, H. M. (1985). “The Cameroon line, West Africa, and its bearing on the origin of oceanic and continental alkali basalt.” Earth and Planetary Science Letters. 72(1): 23-38. https://doi.org/10.1016/0012-821X(85)90114-1
Green, D. H.; Ringwood. (1967). “The genesis of basaltic magmas.” Contributions to Mineralogy and Petrology. 15(2): 103-190. https://doi.org/10.1007/BF00372052
Le Bas, M. J.; Le Maitre, R. W.; Streckeisen, A.; Zanettin, B.; IUGS Subcommission on the Systematics of Igneous Rocks. (1986). “A chemical classification of volcanic rocks based on the total alkali-silica diagram.” Journal of Petrology. 27(3): 745-750. https://doi.org/10.1093/petrology/27.3.745
Poldervaart, A. (1964). “Chemical definition of alkali basalts and tholeiites.” GSA Bulletin. 75(3): 229-232. https://doi.org/10.1130/0016-7606(1964)75%5B229:CDOABA%5D2.0.CO;2
Winter, John DuNann (2001). An Introduction to Igneous and Metamorphic Petrology. Prentice Hall. p. 148. ISBN 0132403420.
Yoder, H. S.; Tilley, C. E. (1962). "Origin of basalt magmas: an experimental study of natural and synthetic rock systems." Journal of Petrology. 3(3): 342-532. https://doi.org/10.1093/petrology/3.3.342
Alkali basalt (Draft)
[edit]
Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock[2] usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields.[3] Alkali basalt is characterized by relatively high alkali (Na2O and K2O) content relative to other basalts and by the presence of olivine and titanium-rich augite in its groundmass and phenocrysts, and nepheline in its CIPW norm.[4][5]
Geochemical characterization
[edit]
Alkali basalt is chemically classified as a rock in region B (basalt) of the total alkali versus silica (TAS) diagram that contains nepheline in its CIPW norm. Basalts that do not contain normative nepheline are characterized as sub-alkali basalts, which include tholeiitic basalts and calc-alkaline basalts.[6]
Petrography
[edit]The groundmass of alkali basalt is mainly composed of olivine, titanium-rich augite and plagioclase feldspar and may have alkali feldspar or feldspathoid interstitially, but is poor in silica minerals, such as hypersthene and quartz.[4]
Phenocrysts are ubiquitous in alkali basalt and, similarly to the groundmass, are usually made up of olivine and titanium-rich augite but can also have plagioclase and iron oxides with lower frequency.[3][4]
Geologic context
[edit]Alkali basalt can be found in areas associated with volcanic activity, such as oceanic islands (Hawaii, Madeira[7], Saint Helena[8], Ascension, etc.), continental rifts and volcanic fields.[3] Continental alkali basalt can be found in every continent, with prominent examples being the Rio Grande Rift (USA), the East African Rift and the Pali-Aike volcanic field.[9]
The results from the gamma ray spectrometer on Venera 8 suggest it landed on Alkali basalt.[10]
References
[edit]- ^ Skewes, Milka Alexandra; Stern, Charles R. (1979). "Petrology and geochemistry of alkali basalts and ultramafic inclusions from the palei-aike volcanic field in Southern Chile and the origin of the patagonian plateau lavas". Journal of Volcanology and Geothermal Research. 6 (1–2): 3–25. doi:10.1016/0377-0273(79)90044-1.
- ^ "Basalt | Definition, Properties, & Facts". Encyclopedia Britannica.
{{cite web}}: CS1 maint: url-status (link) - ^ a b c Haldar, S. K. (2017). Platinum-Nickel-Chromium Deposits. Elsevier. p. 45. ISBN 9780128020418.
- ^ a b c Winter, John DuNann (2001). An Introduction to Igneous and Metamorphic Petrology. Upper Saddle River, New Jersey: Prentice Hall. pp. 148, 182. ISBN 0132403420.
- ^ Irvine, T. N.; Baragar, W. R. A. (1971). "A Guide to the Chemical Classification of the Common Volcanic Rocks". Canadian Journal of Earth Sciences. 8 (5): 523–548. doi:10.1139/e71-055.
- ^ a b Le Maitre, R. W.; Streckeisen, A.; Zanettin, B.; Le Bas, M. J.; Bonin, B.; Bateman, P., eds. (2002). Igneous Rocks: A Classification and Glossary of Terms. Cambridge University Press. pp. 36–37. ISBN 9780521662154.
- ^ Hughes, D. J.; Brown, G. C. (1972). "Basalts from Madeira: A petrochemical contribution to the genesis of oceanic alkali rock series". Contributions to Mineralogy and Petrology. 37 (2): 91–109. doi:10.1007/BF00371069. ISSN 1432-0967.
- ^ Baker, Ian (1969). "Petrology of the Volcanic Rocks of Saint Helena Island, South Atlantic". GSA Bulletin. 80 (7): 1283–1310. doi:10.1130/0016-7606(1969)80[1283:POTVRO]2.0.CO;2. ISSN 0016-7606.
- ^ Farmer, G.L. (2005). Rudnick, R.L. (ed.). Treatise on Geochemistry: The crust. Gulf Professional Publishing. p. 97. ISBN 9780080448473.
- ^ Ulivi, Paolo; Harland, David M (2007). Robotic Exploration of the Solar System Part I: The Golden Age 1957-1982. Springer. pp. 159–160. ISBN 9780387493268.