Other Scholarly Content

 

Insights into mantle composition and mantle melting beneath mid‐ocean ridges from postspreading volcanism on the fossil Galapagos Rise Public Deposited

Downloadable Content

Download PDF
https://ir.library.oregonstate.edu/concern/defaults/4q77fw457

This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by American Geophysical Union and can be found at:  http://www.agu.org/journals/gc/.

Descriptions

Attribute NameValues
Creator
Abstract
  • New major and trace element and Sr, Nd, and Pb isotope data, together with ³⁹ Ar-⁴⁰Ar ages for lavas from the extinct Galapagos Rise spreading center in the eastern Pacific reveal the evolution in magma compositions erupted during slowdown and after the end of active spreading at a mid-ocean ridge. Lavas erupted at 9.2 Ma, immediately prior to the end of spreading are incompatible element depleted mid-ocean ridge tholeiitic basalts, whereas progressively younger (7.5 to 5.7 Ma) postspreading lavas are increasingly alkalic, have higher concentrations of incompatible elements, higher La/Yb, K/Ti, ⁸⁷Sr/⁸⁶Sr, and lower ¹⁴³Nd/¹⁴⁴Nd ratios and were produced by smaller degrees of mantle melting. The large, correlated variations in trace element and isotope compositions can only be explained by melting of heterogenous mantle, in which incompatible trace element enriched lithologies preferentially contribute to smaller degree mantle melts. The effects of variable degrees of melting of heterogeneous mantle on lava compositions must be taken into account when using mid-ocean ridge basalt (MORB) to infer the conditions of melting beneath active spreading ridges. For example, the stronger “garnet signature” inferred from Sm/Nd and ¹⁴³Nd/¹⁴⁴Nd ratios for postspreading lavas from the Galapagos Rise results from a larger contribution from enriched lithologies with high La/Yb and Sm/Yb, rather than from a greater proportion of melting in the stability field of garnet peridotite. Correlations between ridge depth and Sm/Yb and fractionation-corrected Na concentrations in MORB worldwide could result from variations in mantle fertility and/or variations in the average degree of melting, rather than from large variations in mantle temperature. If more fertile mantle lithologies are preferentially melted beneath active spreading ridges, then the upper mantle may be significantly more “depleted” than is generally inferred from the compositions of MORB.
Resource Type
DOI
Date Available
Date Issued
Citation
  • Haase, K. M., M. Regelous, R. A. Duncan, P. A. Brandl, N. Stroncik, and I. Grevemeyer (2011), Insights into mantle composition and mantle melting beneath mid‐ocean ridges from postspreading volcanism on the fossil Galapagos Rise, Geochemistry Geophysics Geosystems, 12(5), Q0AC11, doi:10.1029/2010GC003482.
Series
Keyword
Rights Statement
Funding Statement (additional comments about funding)
  • This study was funded by the Bundesministerium für Bildung und Forschung through grant 03G0160A.
Publisher
Peer Reviewed
Language
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Sue Kunda(sue.kunda@oregonstate.edu) on 2011-12-19T18:39:09Z (GMT) No. of bitstreams: 1 DuncanRobert.COAS.InsightsMantleComposition.pdf: 1812539 bytes, checksum: b5b088c8e951539c79261495ec8e8fd5 (MD5)
  • description.provenance : Made available in DSpace on 2011-12-19T18:39:09Z (GMT). No. of bitstreams: 1 DuncanRobert.COAS.InsightsMantleComposition.pdf: 1812539 bytes, checksum: b5b088c8e951539c79261495ec8e8fd5 (MD5) Previous issue date: 2011-05
  • description.provenance : Submitted by Deanne Bruner (deanne.bruner@oregonstate.edu) on 2011-12-08T22:51:21Z No. of bitstreams: 1 DuncanRobert.COAS.InsightsMantleComposition.pdf: 1812539 bytes, checksum: b5b088c8e951539c79261495ec8e8fd5 (MD5)

Relationships

Parents:

This work has no parents.

Items