1. Leg 197 Synthesis: Southward Motion and Geochemical Variability of the Hawaiian Hotspot1

Robert A. Duncan,2 John A. Tarduno,3 and David W. Scholl4


The bend in the Hawaiian-Emperor volcanic chain is an often-cited example of a change in plate motion with respect to a stationary hotspot. Growing evidence, however, suggests that the bend might instead record variable drift of the Hawaiian hotspot within a convecting mantle. Paleomagnetic and radiometric age data from samples recovered during Ocean Drilling Program (ODP) Leg 197 define an age-progressive paleolatitude history, indicating that the Emperor Seamounts volcanic trend was formed principally by rapid (4–5 cm/yr) southward motion of the Hawaiian hotspot during Late Cretaceous to early Tertiary time (81–47 Ma). Paleointensity data derived from Leg 197 suggest an inverse relationship between field strength and reversal frequency, consistent with an active lower mantle that controls the efficiency of the geodynamo. Petrochemical data and observations of volcanic products (lava flows and volcaniclastic sediments) from Detroit, Nintoku, and Koko Seamounts provide records of the evolution of these volcanic systems for comparison with recent activity in the Hawaiian Islands. We find that the Emperor Seamounts formed from similar mantle sources for melting (plume components and lithosphere) and in much the same stages of volcanic activity and time span as the Hawaiian volcanoes. Changes in major and trace element and Sr isotopic compositions of shield lavas along the lineament can be related to variations in thickness of the lithosphere overlying the hotspot that control the depth and extent of partial melting. Other geochemical tracers, such as He, Pb, and Hf isotopic compositions, indicate persistent contributions to melting from the plume throughout the volcanic chain.

1Duncan, R.A., Tarduno, J.A., and Scholl, D.W., 2006. Leg 197 synthesis: Southward motion and geochemical variability of the Hawaiian hotspot. In Duncan, R.A., Tarduno, J.A., Davies, T.A., and Scholl, D.W. (Eds.), Proc. ODP, Sci. Results, 197 (Online). Available from World Wide Web: <http://www-odp.tamu.edu/publications/197_SR/synth/synth.htm>. (Cited YYYY-MM-DD)

2College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean Administration Building, Corvallis OR 97331-5503, USA. rduncan@coas.oregonstate.edu

3Department of Earth and Environmental Sciences, University of Rochester, 227 Hutchison Hall, Rochester NY 14627-0221, USA.

4US Geological Survey, 345 Middlefield Road, Menlo Park CA 94025, USA.

Initial receipt: 30 January 2006
Acceptance: 19 May 2006
Web publication: 23 June 2006
Ms 197SR-001