Bulletin of Volcanology

, Volume 59, Issue 8, pp 577–592

Petrology and geochronology of basalt breccia from the 1996 earthquake swarm of Loihi seamount, Hawaii: magmatic history of its 1996 eruption

  • Michael O. Garcia
  • Ken H. Rubin
  • Marc D. Norman
  • J. Michael Rhodes
  • David W. Graham
  • David W. Muenow
  • Khalil Spencer
ORIGINAL PAPER

DOI: 10.1007/s004450050211

Cite this article as:
Garcia, M., Rubin, K., Norman, M. et al. Bull Volcanol (1998) 59: 577. doi:10.1007/s004450050211

Abstract

 Samples of basalt were collected during the Rapid Response cruise to Loihi seamount from a breccia that was probably created by the July to August 1996 Loihi earthquake swarm, the largest swarm ever recorded from a Hawaiian volcano. 210Po–210Pb dating of two fresh lava blocks from this breccia indicates that they were erupted during the first half of 1996, making this the first documented historical eruption of Loihi. Sonobuoys deployed during the August 1996 cruise recorded popping noises north of the breccia site, indicating that the eruption may have been continuing during the swarm. All of the breccia lava fragments are tholeiitic, like the vast majority of Loihi's most recent lavas. Reverse zoning at the rim of clinopyroxene phenocrysts, and the presence of two chemically distinct olivine phenocryst populations, indicate that the magma for the lavas was mixed just prior to eruption. The trace element geochemistry of these lavas indicates there has been a reversal in Loihi's temporal geochemical trend. Although the new Loihi lavas are similar isotopically and geochemically to recent Kilauea lavas and the mantle conduits for these two volcanoes appear to converge at depth, distinct trace element ratios for their recent lavas preclude common parental magmas for these two active volcanoes. The mineralogy of Loihi's recent tholeiitic lavas signify that they crystallized at moderate depths (∼8–9 km) within the volcano, which is approximately 1 km below the hypocenters for earthquakes from the 1996 swarm. Taken together, the petrological and seismic evidence indicates that Loihi's current magma chamber is considerably deeper than the shallow magma chamber (∼3–4 km) in the adjoining active shield volcanoes.

Key words Hawaii Loihi Magmatic processes Submarine volcanism Petrology Geochronology Lava geochemistry 

Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • Michael O. Garcia
    • 1
  • Ken H. Rubin
    • 1
  • Marc D. Norman
    • 2
  • J. Michael Rhodes
    • 3
  • David W. Graham
    • 4
  • David W. Muenow
    • 5
  • Khalil Spencer
    • 1
  1. 1.Department of Geology and Geophysics, Hawaii Center for Volcanology, University of Hawaii, Honolulu, Hawaii 96822, USAUS
  2. 2.Key Centre for the Geochemical Evolution and Metallogeny of the Continents (GEMOC), School of Earth Sciences, Macquarie University, North Ryde, NSW 2109 AustraliaAU
  3. 3.Department of Geosciences, University of Massachusetts, Amherst, MA 01003, USAUS
  4. 4.College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331–5503, USAUS
  5. 5.Department of Chemistry, University of Hawaii, Honolulu, Hawaii 96822, USAUS

Personalised recommendations