Open AccessContribution of serpentinized ultramafics to marine magnetic anomalies at slow and intermediate spreading centres: insights from the shape of the anomalies
Author(s) -
Dyment Jérôme,
ArkaniHamed Jafar,
Ghods Abdolreza
Publication year - 1997
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1997.tb04504.x
Subject(s) - crust , geology , magnetization , magnetic anomaly , oceanic crust , mantle (geology) , geophysics , lithosphere , hydrothermal circulation , peridotite , seismology , magnetic field , tectonics , subduction , physics , quantum mechanics
SUMMARY Detailed characteristics of marine magnetic anomalies 33r and 20r suggest that the magnetization of the deeper magnetic layers, including the lower crust and possibly the uppermost mantle, is horizontally displaced with respect to that of the upper crust. We examine the possibility that serpentinization of ultramafics in the lower crust and possibly the uppermost mantle delays the acquisition of magnetization and introduces a shift between the upper‐ and lower‐crustal magnetization patterns. Thermal evolution models and the resulting magnetization patterns of the oceanic lithosphere are calculated for a wide range of physical parameters such as the Nusselt number and the depth of hydrothermal circulation in the crust, and the temperature range of serpentinization. The models with moderate hydrothermal cooling of the whole crust and serpentinization temperatures ranging between 200 and 300 d̀C successfully explain the anomalous skewness and the ‘hook shape’ of observed sea‐level magnetic anomalies created at slow and intermediate spreading rates.