Probing magnetic bottom and crustal temperature variations along the Red Sea margin of Egypt

D. Ravat, Ahmed Salem, A. M.S. Abdelaziz, E. Elawadi, P. Morgan

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Over 50 magnetic bottom depths derived from spectra of magnetic anomalies in Eastern Egypt along the Red Sea margin show variable magnetic bottoms ranging from 10 to 34. km. The deep magnetic bottoms correspond more closely to the Moho depth in the region, and not the depth of 580°C, which lies significantly deeper on the steady state geotherms. These results support the idea of Wasilewski and coworkers that the Moho is a magnetic boundary in continental regions. Reduced-to-pole magnetic highs correspond to areas of Younger Granites that were emplaced toward the end of the Precambrian. Other crystalline Precambrian units formed earlier during the closure of ocean basins are not strongly magnetic. In the north, magnetic bottoms are shallow (10-15. km) in regions with a high proportion of these Younger Granites. In the south, the shoaling of the magnetic bottom associated with the Younger Granites appears to be restricted to the Aswan and Ras Banas regions. Complexity in the variation of magnetic bottom depths may arise due to a combination of factors: i) regions of Younger (Precambrian) Granites with high magnetite content in the upper crust, leaving behind low Curie temperature titanomagnetite components in the middle and lower crust, ii) rise in the depth of 580°C isotherm where the crust may have been heated due to initiation of intense magmatism at the time of the Red Sea rifting (~. 20. Ma), and iii) the contrast of the above two factors with respect to the neighboring regions where the Moho and/or Curie temperature truncates lithospheric ferromagnetism. Estimates of fractal and centroid magnetic bottoms in the oceanic regions of the Red Sea are significantly below the Moho in places suggesting that oceanic uppermost mantle may be serpentinized to the depth of 15-30 km in those regions.

Original languageEnglish
Pages (from-to)337-344
Number of pages8
JournalTectonophysics
Volume510
Issue number3-4
DOIs
StatePublished - Oct 4 2011

Bibliographical note

Funding Information:
We are grateful to the U.S.–Egypt Joint Board Scientific and Technological Cooperation and the U.S. National Science Foundation for funding this research under grant no. 0752764 . We also thank Prof. Derek Fairhead and GETECH for making available some of the airborne magnetic anomaly data over Egypt used in this paper. We thank Prof. Randy Keller whose constructive review helped clarify parts of the manuscript. We also thank Prof. Mian Liu for his editorial work. Finally, D.R. thanks the Rockefeller Foundation's Bellagio Center for extending to him the spousal hospitality that made it possible to write the bulk of this paper.

Keywords

  • Curie depth
  • Eastern Egypt
  • Heat flow
  • Magmatism
  • Magnetic bottom
  • Red Sea

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes

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