Hotspot activity and plume pulses recorded by geometry of spreading axes

Meir Abelson*, Amotz Agnon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Anomalous plan view geometry (planform) of spreading axes is shown to be a faithful indicator of hotspot influence, possibly capable of detecting pulses of hotspot discharge. A planform anomaly (PA) occurs when the orientation of second-order ridge segments is prominently oblique to the spreading direction. PA is found in the vicinity of hotspots at shallow ridges (< 1.5 km), suggesting hotspot influence. In places the PA and shallow bathymetry are accompanied by geochemical anomalies, corroborating hotspot influence. This linkage is best expressed in the western Gulf of Aden, where the extent of the PA from the Afar hotspot coincides with the extent of La/Sm and Sr isotopic anomalies. Using fracture mechanics we predict PA to reflect overpressurized melt that dominates the stresses in the crust, consistent with hotspot regime. Accordingly, the temporal variations of the planform previously inferred from magnetic anomalies around the Kolbeinsey Ridge (KR), north of Iceland, record episodes of interaction with the hotspot and major pulses of the plume. This suggestion is corroborated by temporal correlation of episodes showing PA north of Iceland with plume pulses previously inferred by the V-shaped ridges around the Reykjanes Ridge (RR), south of Iceland. In contrast to the RR, the temporal correlation suggests simultaneous incidence of the plume pulses at Iceland and KR, hundreds of kilometers to the north. A deep northward branch of the Iceland plume active during pulse-periods may explain these observations.

Original languageAmerican English
Pages (from-to)31-47
Number of pages17
JournalEarth and Planetary Science Letters
Volume189
Issue number1-2
DOIs
StatePublished - 2001

Bibliographical note

Funding Information:
We thank Garrett Ito and Javier Escartin for profound and constructive reviews. We also benefited from discussions with Moti Stein and Oded Navon. A.A. was supported by the US-Israel Binational Science Foundation under Grant 92/345. [AC]

Keywords

  • Anomalies
  • Fracture strength
  • Hot spots
  • Mechanisms
  • Mid-ocean ridges
  • Plumes

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