Depth to Curie temperature across the central Red Sea from magnetic data using the de-fractal method

Ahmed Salem, Chris Green, Dhananjay Ravat, Kumar Hemant Singh, Paul East, J. Derek Fairhead, Saad Mogren, Ed Biegert

Research output: Contribution to journalArticlepeer-review

91 Scopus citations

Abstract

The central Red Sea rift is considered to be an embryonic ocean. It is characterised by high heat flow, with more than 90% of the heat flow measurements exceeding the world mean and high values extending to the coasts - providing good prospects for geothermal energy resources. In this study, we aim to map the depth to the Curie isotherm (580. °C) in the central Red Sea based on magnetic data. A modified spectral analysis technique, the "de-fractal spectral depth method" is developed and used to estimate the top and bottom boundaries of the magnetised layer. We use a mathematical relationship between the observed power spectrum due to fractal magnetisation and an equivalent random magnetisation power spectrum. The de-fractal approach removes the effect of fractal magnetisation from the observed power spectrum and estimates the parameters of depth to top and depth to bottom of the magnetised layer using iterative forward modelling of the power spectrum. We applied the de-fractal approach to 12 windows of magnetic data along a profile across the central Red Sea from onshore Sudan to onshore Saudi Arabia. The results indicate variable magnetic bottom depths ranging from 8.4. km in the rift axis to about 18.9. km in the marginal areas. Comparison of these depths with published Moho depths, based on seismic refraction constrained 3D inversion of gravity data, showed that the magnetic bottom in the rift area corresponds closely to the Moho, whereas in the margins it is considerably shallower than the Moho. Forward modelling of heat flow data suggests that depth to the Curie isotherm in the centre of the rift is also close to the Moho depth. Thus Curie isotherm depths estimated from magnetic data may well be imaging the depth to the Curie temperature along the whole profile. Geotherms constrained by the interpreted Curie isotherm depths have subsequently been calculated at three points across the rift - indicating the variation in the likely temperature profile with depth.

Original languageEnglish
Pages (from-to)75-86
Number of pages12
JournalTectonophysics
Volume624-625
DOIs
StatePublished - 2014

Bibliographical note

Funding Information:
We are indebted to Dr. Richard Blakely for his discussions and comments on the idea of the paper. We also thank an anonymous reviewer and Dr. Bouligand for comments and suggestions, which helped greatly in improving the manuscript. The techniques used in this study were developed as part of a joint depth to Curie temperature study implemented primarily by Getech and funded by Shell. The method of computing geotherms using temperature-depth constraints was developed by DR with a grant from the US National Science Foundation (EAR-1246921).

Keywords

  • Curie
  • Depth
  • Heat flow
  • Magnetic
  • Red Sea

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes

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