Ujlān_volcanic_complex

Ujlān volcanic complex

Ujlān volcanic complex

Seamount in the Pacific Ocean

Ujlān volcanic complex is a group of seamounts in the Marshall Islands. The complex consists of the seamounts Ļajutōkwa, Ļalibjet, Likelep, Ļotāb and Ujlān[1] which with a minimum depth of 1,250 metres (4,100 ft) is the shallowest part of the complex;[2] sometimes Ujelang Atoll is also considered to be a part of the complex;[1][3] Eniwetok atoll and Lo-En seamount form a cluster together with this volcanic complex.[4]

Quick Facts Location, Geology ...
Seamounts and an atoll in the volcanic complex
Ujelan atoll

These are simple single-peaked seamounts with the exception of the three-peaked Ujlān and there appear to be two rift zones associated with the complex.[5] Between the seamounts the seafloor is covered with debris while the seamounts themselves are covered with varying thicknesses of pelagic sediments;[2] however in general volcanic rocks and mostly breccia are the dominant components.[6] Minerals found in samples from the volcanic complex include biotite, hornblende and plagioclase.[7] Video observation has noted sediment deposits with ferromanganese knolls on some of the seamounts.[8] There is little evidence of reefs but most seamounts were affected by slumps; in addition there are frequently terraces and volcanic cones on the seamounts.[9]

The volcanic complex and neighbouring structures may be of Cretaceous age but with some scatter.[10] Likelep features probably Campanian-age rocks[6] and radiometric dating has yielded an age of 81.4–82.8 million years ago for Ļalibjet,[11] 81.2 ± 0.5 for Ļajutōkwa, 82.5 ± 0.2 for Likelep, 79.7 ± 0.4 for Ļotāb and 80.1 ± 0.5 for Ujlān.[12] The complex is also known as the Ujlān seamount trail[7] and its formation of this complex may be related to the Rarotonga hotspot[13] while the geochemistry shows affinities to the Samoa hotspot.[14]

The seamount complex is located within the exclusive economic zone of the Marshall Islands,[1] and Ļalibjet has been considered a site for cobalt mining.[15] The names of the seamounts come from Marshallese; Ļajutōkwa was the first navigator chief in the northern Marshall Islands, Ļalibjet is a sea god, Likelep is a place on Ujlān and Ļotāb like his ancestor Litōrmalū is a legendary navigator.[16] One source has given Ļalibjet as the old name for Likelep.[17]

References

  1. [1]
    Hein et al. 1990, p. 1.
  2. [2]
    Hein et al. 1990, pp. 5–6.
  3. [3]
    Hein, James R.; Wong, Florence L.; Mosier, Dan L. (1999). "Bathymetry of the Republic of the Marshall Islands and vicinity". Miscellaneous Field Studies Map.
  4. [4]
    Bergersen 1995, p. 605.
  5. [5]
    Hein et al. 1990, p. 3.
  6. [6]
    Hein et al. 1990, p. 12.
  7. [7]
    Koppers et al. 2003, p. 20.
  8. [8]
    Hein et al. 1990, p. 11.
  9. [9]
    Hein et al. 1990, p. 6.
  10. [10]
    Bergersen 1995, p. 610.
  11. [11]
    Bergersen 1995, p. 606.
  12. [12]
    Koppers et al. 2003, p. 7.
  13. [13]
    Bergersen 1995, p. 609.
  14. [14]
    Koppers et al. 2003, p. 25.
  15. [15]
    Masuda, Y.; Cruickshank, M.J.; Abernathy, J.A.; Winston, R. (1991). "Feasibility Study Of Crust Mining In The Republic Of The Marshall Islands". OCEANS 91 Proceedings. pp. 1475–1478. doi:10.1109/OCEANS.1991.606510. ISBN 978-0-7803-0202-0. S2CID 106667117.
  16. [16]
    Hein et al. 1990, p. 245.
  17. [17]
    Foulger, Gillian R. (2005). Plates, Plumes, and Paradigms. Geological Society of America. p. 81. ISBN 9780813723884.

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