Petrologic Evolution of the Louisville Seamount Chain

  1. Barbara H. Keating,
  2. Patricia Fryer,
  3. Rodey Batiza and
  4. George W. Boehlert
  1. James W. Hawkins1,
  2. Peter F. Lonsdale1 and
  3. Rodey Batiza2

Published Online: 18 MAR 2013

DOI: 10.1029/GM043p0235

Seamounts, Islands, and Atolls

Seamounts, Islands, and Atolls

How to Cite

Hawkins, J. W., Lonsdale, P. F. and Batiza, R. (1987) Petrologic Evolution of the Louisville Seamount Chain, in Seamounts, Islands, and Atolls (eds B. H. Keating, P. Fryer, R. Batiza and G. W. Boehlert), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM043p0235

Author Information

  1. 1

    Geological Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093

  2. 2

    Department of Geological Sciences, Northwestern University, Evanston, IL 60201

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1987

ISBN Information

Print ISBN: 9780875900681

Online ISBN: 9781118664209



  • Seamounts;
  • Coral reefs and islands


The Louisville Seamount Chain (LSC) extends for 4300 km from Osbourn Seamount, at the junction of the Tonga and Kermadec Trenches, southeasterly towards the Pacific Antarctic Ridge. The chain is formed of 60 or more seamounts and guyots which are aligned along a trend concentric with the Emperor-Hawaii Chain. The Louisville Chain crosses at a low angle several fracture zones which are part of the Eltanin Fracture Zone system, but there is no apparent genetic relation between the two structures. Rocks collected from the Louisville Chain comprise a spectrum of rock types including alkalic basalt, hawaiite, and basanitoid. Some samples have compositions suggesting that they are transitional to tholeiitic basalt, but no true tholeiites have been collected from the seamounts. Osbourn Seamount, at the westernmost end of the chain, is capped with basanitoid; these have been dated as ∼66 Ma. Clinopyroxene phenocrysts in basaltic composition pebbles and detrital grains of clinopyroxene have been recovered from DSDP site 204, north of Osbourn Seamount, at subbottom depths of 112 to 114 meters (Late? Cretaceous age). Some of these pyroxenes have compositions indicating a tholeiitic parental magma, some were derived from alkalic magmas. Osbourn Seamount or an older neighbor were likely sources of the clastic sediments. This is an indication that the early stages of seamount volcanism included tholeiitic magmas, magmatism subsequently evolved through alkalic and basanitic types. Samples dredged from the carapaces of seamounts east of Osbourn are mainly alkalic basalt, or hawaiite, or both. The young, eastern end of the chain near Long. 139°10′W has alkalic basalt lavas.

Modeling of trace element and REE data suggest that small amounts (e.g., 4%) melting of garnet Iherzolite could have provided the parental alkalic basalt magmas. Basanitoids represent slightly higher (∼9%) levels of melting. Element ratios of Ti/Zr, Nb/Zr, Y/Zr, Ba/La, La/Ce, La/Sm, Nb/La suggest that the mantle source for the LSC seamounts remained remarkably homogeneous through the ∼66 m.y. recorded history of the chain. This is also supported by Nd and Sr isotope data for these samples. The mantle source must have been enriched in elements such as K, Rb, Ba, Y, REE relative to the source for N-MORB or to “primitive” mantle. The LSC seamounts have evolved through a petrologic sequence like that of the Hawaiian and Samoan Chains, but the long term homogeneity of the mantle source of LSC mag mas is in marked contrast to the heterogeneous mantle implied by the petrology of Hawaiian and Samoan volcanoes. A hotspot origin for the LSC seems likely: there may be an active “Loihi counterpart” yet to be found at the southeastern end of the chain.