The Pleiades (volcano group)

The Pleiades are a volcanic group in northern Victoria Land of Antarctica. It consists of youthful cones and domes with Mount Atlas/Mount Pleiones, a small stratovolcano formed by three overlapping cones, being the dominant volcano and rising 500 m (1,600 ft) above the Evans Névé plateau. Two other named cones are Alcyone Cone and Taygete Cone, the latter of which has been radiometrically dated to have erupted during the Holocene. A number of tephra layers across Antarctica have been attributed to eruptions of this volcanic group, including several that may have occurred within the last few hundred years.

This article is about the volcano cones. For other uses of Pleiades, see Pleiades (disambiguation).
The Pleiades
The Pleiades
Location in Antarctica
Highest point
Elevation3,040 m (9,970 ft) [1]
Coordinates72°40′S 165°30′E [1]
Geography
LocationVictoria Land, Antarctica
Geology
Volcanic beltMcMurdo Volcanic Group
Last eruption1050 BCE ± 14,000 years[2]

Geography and geomorphology

The Pleiades are located at the crest of the Transantarctic Mountains,[3] 120 to 140 km (75 to 87 mi)[4][5] away from the coast of Lady Newnes Bay, Ross Sea.[6] The volcanoes are located between Evans Neve and the beginning of Mariner Glacier,[5] which drains Evans Neve[7] southeastwards towards the Ross Sea.[8] The volcanic group is named after the Pleiades star cluster in the constellation Taurus; the name was assigned to them by the New Zealand Geological Survey Antarctic Expedition.[9]

The volcanic group is formed by several steep,[10] small volcanic cones and lava domes that emerge from the ice of Evans Neve[11] over a 13 km (8.1 mi) long area. Most are nameless with the exception of the central Taygete Cone, Alcyone Cone just south of Taygete and the pair of c. 3,020 m (9,910 ft) high Mount Pleiones and c. 3,040 m (9,970 ft) high Mount Atlas in the southern sector.[12] Mount Atlas and Mount Pleiones form a compound stratovolcano[13] which is the principal volcano of The Pleiades.[14] Mount Atlas is formed by three separate cones that rise 0.5 km (0.31 mi) above the ice. Dykes, lava and scoria flows are found on these cones, the youngest of which has a semicircular crater.[15] and scoria cones dot its flanks.[16] At the foot of Mount Atlas are moraines with the form of ridges.[17] The cones northeast of Mount Pleiones may outline a caldera and its summit features nested craters.[18]

Alcyone Cone lies 3.5 km (2.2 mi) north of Mount Atlas.[5] It is only slightly lower than Mount Atlas but is much smaller. It has two poorly defined craters and consists of lava flows covered with scree and volcanic bombs when not buried under snow.[19] Taygete Cone 6 km (3.7 mi) north of Mount Atlas[5] appears to be a lava dome bearing traces of hydrothermal alteration and of a small crater.[19] Apart from the lava flows which make up most of Mount Atlas,[20] pyroclastic rocks have been encountered at The Pleiades.[21] The other cones are partly buried by snow and some have breached or otherwise eroded craters.[22]

The volcanoes have alternatively been described as eroded[23] or uneroded.[24] The young appearance of the edifices indicates a young age of The Pleiades volcanoes.[25] The volcanoes have been prospected for the possibility to generate geothermal energy but the presence of a good heat source is unlikely.[26] An aeromagnetic anomaly has been correlated to the volcano group.[27]

Geology

The Pleiades belong to the McMurdo Volcanic Group and more specifically to the Melbourne volcanic province, which extends from Mount Melbourne to The Pleiades and Malta Plateau.[28] These consist of the Cenozoic volcanoes of northern Victoria Land which form alignments and lineaments possibly controlled by deep fractures, and which are subdivided into a "Central Suite" consisting of large stratovolcanoes and a "Local Suite" consisting of other volcanic centres. Among the volcanoes of the McMurdo Volcanic Group are the large volcanoes Mount Overlord, Mount Melbourne[29] and in the area of The Pleiades the Malta Plateau.[30] Volcanic activity began about 10 – 7 million years ago.[31] Earlier volcanic activity began during the Cretaceous, when the West Antarctic Rift System became active.[32]

The basement underneath the volcanoes consists of Precambrian and Paleozoic sedimentary and intrusive rocks. The former are mostly represented by the Bowers Group/Bowers Supergroup and the Robertson Bay Group north of the volcanic complex and the latter by the Granite Harbour and Admiralty Intrusives mostly south of the volcanic complex. A major local fault system passes northeast of the volcanoes[33][34] and roughly follows the path of the Mariner Glacier,[35] while the Lanternman Fault passes southwest of them.[36] Some of these faults formed during the Ross Orogeny, when three terranes collided to form northern Victoria Land;[37] The Pleiades are located on the Bowers Terrane.[38] Faults may also govern the position of The Pleiades volcanoes.[39]

Composition

Basanite, basalt, benmoreite, hawaiite, phonolite, trachyandesite, trachyte and tristanite have been recovered from The Pleiades. These volcanic rocks define two separate sodium and potassium-rich magma suites and may originate from separate levels of the same magma chamber[40] or through fractional crystallization.[41] Ultimately, these magmas originate from a metasomatized mantle and were altered through assimilation of crustal material as they ascended.[42] Overall, these volcanic rocks define one of the most complete magmatic series of the McMurdo Volcanic Group.[43] It is possible that the volcanoes first erupted trachyte and later basalts,[44] but later findings indicate that the two suites were erupted simultaneously.[45] Phenocrysts include anorthoclase, apatite, augite, biotite, kaersutite, magnetite, oligoclase and olivine.[46] Essexite,[47] granodiorite,[48] granite and syenite xenoliths also occur.[49] Hydrothermal alteration at Taygete Cone has produced hematite and sulfur which coat and stain bleached trachyte.[50]

Eruption history

The oldest dated eruptions took place about 825,000 years ago and emplaced trachytes in the central part of the field; even older eruptions may have occurred but are now buried underneath of snow and ice. Three more eruptions occurred in the subsequent 700,000 years before activity began to increase after 100,000 years.[51] Potassium-argon dating has yielded imprecise ages of 40,000 ± 50,000 for Mount Atlas and 20,000 ± 40,000 and 12,000 ± 40,000 for other volcanic cones.[52] Later argon-argon dating has yielded ages of less than 100,000 years for lavas on Mount Atlas[53] and for a lava east of Taygete, and ages of about 45,000 years for Alcyone and two more lava flows on Mount Atlas.[54]

Tephra deposits have been found in Antarctica which may originate at The Pleiades. These include:

The youngest ages of 6,000 ± 6,000[67] and 3,000 ± 14,000 years ago have been obtained on Taygete,[68] which together with the youthful texture of this dome[69] indicates a young age for The Pleiades, despite the imprecise dates.[70] The presence of pumice lapilli has been taken as evidence of very recent activity in the form of a moderate pumice eruption.[71] Presently, only minor fumarolic activity has been reported.[66] Future eruptions are possible[72] and The Pleiades are not monitored, but they are also remote from any research station.[73]

See also

References
  1. "The Pleiades". Global Volcanism Program. Smithsonian Institution. Retrieved 22 March 2020.
  2. "The Pleiades". Global Volcanism Program. Smithsonian Institution. Retrieved 15 October 2020., Eruption history
  3. Stump 1986, p.305
  4. Kyle 1982, p.747
  5. Faure and Mensing 2011, p.549
  6. Kyle 1982, p.748
  7. Riddolls and Hancox, 1968 p.882
  8. Kyle 1982, p.748
  9. Alberts, Fred G. (ed.). Geographic names of the Antarctic (Report). p. 580.
  10. Riddolls and Hancox, 1968 p.897
  11. LeMasurier et al. 1990, p.60
  12. Kyle 1982, p.749
  13. Kim et al. 2019, p.120
  14. Stump 1986, p.305
  15. Kyle 1982, p.750
  16. LeMasurier et al. 1990, p.60
  17. Kyle 1982, p.750
  18. LeMasurier et al. 1990, pp.60-62
  19. Kyle 1982, p.750
  20. Esser and Kyle 2002, p.415
  21. Stump 1986, p.305
  22. Kyle 1982, p.751
  23. Esser and Kyle 2002, p.415
  24. Stump 1986, p.305
  25. Stump 1986, p.305
  26. Splettstoesser, John F.; Dreschhoff, Gisela A. M., eds. (1990). Mineral Resources Potential of Antarctica. Antarctic Research Series. 51. Washington, D. C.: American Geophysical Union. p. 119. doi:10.1029/ar051. ISBN 978-0-87590-174-9.
  27. Ferraccioli, F.; Armadillo, E.; Zunino, A.; Bozzo, E.; Rocchi, S.; Armienti, P. (2009-11-20). "Magmatic and tectonic patterns over the Northern Victoria Land sector of the Transantarctic Mountains from new aeromagnetic imaging". Tectonophysics. Magnetic Anomalies. 478 (1): 46. Bibcode:2009Tectp.478...43F. doi:10.1016/j.tecto.2008.11.028. ISSN 0040-1951.
  28. Stump 1986, p.305
  29. Kyle 1982, p.747
  30. Riddolls and Hancox, 1968 p.897
  31. Kyle 1982, p.752
  32. Kim et al. 2019, p.119
  33. Kyle 1982, p.748
  34. Riddolls and Hancox, 1968 p.884
  35. Riddolls and Hancox, 1968 p.884
  36. Kim et al. 2019, p.119
  37. Kim et al. 2019, p.118
  38. Kim et al. 2019, p.119
  39. LeMasurier et al. 1990, p.25
  40. Kyle 1982, p.749,751
  41. Stump 1986, p.305
  42. Kim et al. 2019, p.142
  43. Stump 1986, p.335
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  51. Esser and Kyle 2002, p.417
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  53. Esser and Kyle 2002, p.417
  54. Esser and Kyle 2002, p.418
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  56. Narcisi, Biancamaria; Petit, Jean Robert; Langone, Antonio; Stenni, Barbara (2016-02-01). "A new Eemian record of Antarctic tephra layers retrieved from the Talos Dome ice core (Northern Victoria Land)". Global and Planetary Change. 137: 69. Bibcode:2016GPC...137...69N. doi:10.1016/j.gloplacha.2015.12.016. hdl:2027.42/148354. ISSN 0921-8181.
  57. Curzio, Pietro; Folco, Luigi; Ada Laurenzi, Marinella; Mellini, Marcello; Zeoli, Antonio (2008-03-01). "A tephra chronostratigraphic framework for the Frontier Mountain blue-ice field (northern Victoria Land, Antarctica)". Quaternary Science Reviews. 27 (5): 616. Bibcode:2008QSRv...27..602C. doi:10.1016/j.quascirev.2007.11.017. ISSN 0277-3791.
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  66. Boutron, Claude (20 December 1980). "Respective influence of global pollution and volcanic eruptions on the past variations of the trace metals content of Antarctic snows since 1880s". Journal of Geophysical Research: Oceans. 85 (C12): 7431. Bibcode:1980JGR....85.7426B. doi:10.1029/JC085iC12p07426.
  67. Esser and Kyle 2002, p.418
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  69. Kim et al. 2019, p.120
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  72. Esser and Kyle 2002, p.418
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