Abstract
The magnetic mineralogy and Koenigsberger ratio (the ratio of the remanent to induced magnetization) of basaltic rocks from the Troodos ophiolite undergo critical transformations at the zeolite–greenschist facies boundary. At this boundary the magnetic mineralogy changes abruptly from titanomaghaemite to magnetite and the Koenigsberger ratio decreases to less than 1. If similar metamorphism is occurring near the active oceanic ridges today, then the application of the two-layer model to marine magnetic anomalies may be primarily due to the degree of metamorphism and not to the mode of emplacement, intrusive versus extrusive. We show here that apparently in the Troodos ophiolite and, therefore, probably in oceanic rocks formed at spreading centres, the presence of magnetite at depth is a function of the pressure and temperature regime seen at the spreading centre.
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Beske-Diehl, S., Banerjee, S. Metamorphism in the Troodos ophiolite: implications for marine magnetic anomalies. Nature 285, 563–564 (1980). https://doi.org/10.1038/285563a0
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DOI: https://doi.org/10.1038/285563a0
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