Abstract
In this work, we study the lithospheric structure of the British Isles using a methodology that allows for forward modelling of the Curie temperature depth based on seismic, elevation and gravity observations within an integrated geophysical-petrological approach (LitMod3D). We compute 3D thermal models and self-consistently determine the density in the mantle based on temperature, pressure and bulk composition. Finally, we derive Curie temperature depth maps and forward calculate magnetic anomalies at the airborne level using a spherical magnetic modelling software (magnetic tesseroids) to estimate the geothermal magnetic signal. Our results show lateral lithospheric variations across the model domain, with Great Britain being characterized in general by thicker and colder lithosphere, especially in the south-east, and the thinnest and warmest lithosphere being located beneath west Scotland, Northern Ireland and in the north-west oceanic area. Our estimated Curie temperature depth map resembles the values obtained using other techniques (spectral method and surface heat flow inversion) in some areas, but discrepancies are notable in general. We determine that the effect of typical lateral temperature variations (i.e., Curie isotherm depth) accounts for 5-15%, on average, and up to 70% locally of the crustal magnetic signal at the airborne level (5 km altitude). Our lithospheric models are in general agreement with published tomography models as well as other geophysical studies.
Highlights
Gravity data (Bouguer, free air or geoid anomalies) have been extensively used to image the lithospheric and upper mantle density structure (e.g., Götze et al, 1994; Kaban et al, 1999; Ebbing et al, 2006; Chappell and Kusznir, 2008; Maystrenko and Scheck-Wenderoth, 2013)
Hemant (2003) and Hemant and Maus (2005) defined a global lithospheric magnetization model based on a Geographical Information System guided tectonic regionalization by assigning a Vertically Integrated Susceptibility (VIS) distribution that was subsequently refined through forward modeling and comparison with MF7 magnetic field model (Maus, 2010)
In this study we explore the perspectives for a future consistent combination of gravity and magnetic data within a lithospheric thermochemical modeling scheme
Summary
Gravity data (Bouguer, free air or geoid anomalies) have been extensively used to image the lithospheric and upper mantle density structure (e.g., Götze et al, 1994; Kaban et al, 1999; Ebbing et al, 2006; Chappell and Kusznir, 2008; Maystrenko and Scheck-Wenderoth, 2013). Gravity gradient tensor data measured at satellite height have been employed to image lithospheric and upper mantle density variations (e.g., Ebbing et al, 2013, 2014; Panet et al, 2014; Álvarez et al, 2015; Fullea et al, 2015). The two models were based on seismic crustal thickness (i.e., seismic Moho depth) and measurements of magnetic susceptibility. Hemant (2003) and Hemant and Maus (2005) defined a global lithospheric magnetization model based on a Geographical Information System guided tectonic regionalization by assigning a Vertically Integrated Susceptibility (VIS) distribution that was subsequently refined through forward modeling and comparison with MF7 magnetic field model (Maus, 2010). Magnetic data sets have been used for geological mapping, geophysical prospecting studies, and thermal modeling (e.g., Maule et al, 2005; Martos et al, 2017)
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