Spreading-rate dependence of melt extraction at mid-ocean ridges from mantle seismic refraction data

Daniel Lizarralde, James B. Gaherty, John A. Collins, Greg Hirth, Sangmyung D. Kim

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


A variety of observations indicate that mid-ocean ridges produce less crust at spreading rates below 20 mm yr-1 (refs 1-3), reflecting changes in fundamental ridge processes with decreasing spreading rate. The nature of these changes, however, remains uncertain, with end-member explanations being decreasing shallow melting or incomplete melt extraction, each due to the influence of a thicker thermal lid. Here we present results of a seismic refraction experiment designed to study mid-ocean ridge processes by imaging residual mantle structure. Our results reveal an abrupt lateral change in bulk mantle seismic properties associated with a change from slow to ultraslow palaeo-spreading rate. Changes in mantle velocity gradient, basement topography and crustal thickness all correlate with this spreading-rate change. These observations can be explained by variations in melt extraction at the ridge, with a gabbroic phase preferentially retained in the mantle at slower spreading rates. The estimated volume of retained melt balances the ∼1.5-km difference in crustal thickness, suggesting that changes in spreading rate affect melt-extraction processes rather than total melting.

Original languageEnglish (US)
Pages (from-to)744-747
Number of pages4
Issue number7018
StatePublished - Dec 9 2004
Externally publishedYes

ASJC Scopus subject areas

  • General


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