Curie depth estimation from magnetic anomaly data: a re-assessment using multitaper spectral analysis and Bayesian inference

Summary Curie point depth can be used as a proxy for plate temperatures. Data from the North Atlantic (10○ - 50○N) is used here to determine if the observed oscillations and patterns in Curie depths could be a sub product of small-scale thermal instabilities arising at the bottom of the lithospheric plates. Our numerical models suggest that small-scale convection (SSC) cells could produce thermal perturbations at isotherms as low as the Curie point. These results are compatible with North Atlantic observations in terms of wavelengths (150 to 300 km), amplitudes (∼4 km) and orientations of the instabilities. Observed Curie-point depth oscillations before the onset (70 to 90 Myr) of SSC could also be linked to other different processes. We suggest that, in the case of the North Atlantic lithosphere, the spreading rate variation and the melt and upwelling could be intricately linked and cause a different pattern of SSC.

Section: Model Setupmentioning

confidence: 99%

The effects of small-scale convection in the shallow lithosphere of the North Atlantic

Likerman

Zlotnik

2021

“…Moreover, the usual procedure implies to divide the studied area into numerous windows that overlap between them (e.g. : Okubo et al, 1985;Blakely, 1988;Lesane et al, 2015;Bouligand et al, 2009;Idarraga-García & Vargaz, 2018;Audet & Gosselin, 2019). This overlapping allows to increase the data coverage (resolution) and to avoid data loss (of anomalies or frequencies contained in image borders).…”

Section: Windows: Geometry Sizes and Overlappingmentioning

confidence: 99%

“…If there is a large difference between the opposite edges of an image, it will generate an abrupt discontinuity in the signal. These discontinuities are of large bandwidth and can mask other relevant components in the spectrum (Brigham, 1988;Moisan, 2011;Mahmood et al, 2015;Burger & Burge, 2016;Audet & Gosselin, 2019).…”

Section: Windowing Filters and Reduction To The Polementioning

confidence: 99%

Review of Curie point depth determination through different spectral methods applied to magnetic data

Demarco

Prezzi

Bettucci

2020

Summary Spectral methods have been applied for more than 40 years to calculate the depth to magnetic sources and the Curie point depth or Moho depth. Unfortunately, conceptual, theoretical and methodological errors, as well as, subjective approaches and lack of rigor in the application of the method are common. This has affected reproducibility, credibility and confidence in this method. We carried out a detailed mathematical and methodological revision of the spectral methods (centroid, spectral peak, forward and fractal methods) applied to magnetic data for the determination of the depth to magnetic sources. Moreover, a systematic analysis of more than 110 articles was done in order to compile and compare the different approaches and values of key parameters used by different authors in their calculations. We discuss difficulties, conditions and methodological procedures, as well as several misapplications and misinterpretation of the different methods.

“…For a prescribed geological model, populated with correlated and uncorrelated prior information on rates of heat production and thermal conductivity, we found the MAP estimate of temperature subject to the data we assimilated (Figs 5 and 13). However, Curie depth has high intrinsic uncertainty related to the choice of fractal parameter and size of the window used to discretize maps of the magnetic anomaly (Audet & Gosselin 2019;Mather & Fullea 2019), and heat flow data are occasionally perturbed by hydrothermal circulation and suffer from low spatial coverage (Mather et al 2017). These data loosely constrain the 580 • C isotherm and the integrated heat production in sparsely distributed localities for Curie depth and heat flow data, respectively.…”

Section: I M I Tat I O N S a N D F U T U R E D I R E C T I O N Smentioning

confidence: 99%

Adjoint inversion of the thermal structure of Southeastern Australia

Mather

Moresi

2019

SUMMARY The variation of temperature in the crust is difficult to quantify due to the sparsity of surface heat flow observations and lack of measurements on the thermal properties of rocks at depth. We examine the degree to which the thermal structure of the crust can be constrained from the Curie depth and surface heat flow data in Southeastern Australia. We cast the inverse problem of heat conduction within a Bayesian framework and derive its adjoint so that we can efficiently find the optimal model that best reproduces the data and prior information on the thermal properties of the crust. Efficiency gains obtained from the adjoint method facilitate a detailed exploration of thermal structure in SE Australia, where we predict high temperatures within Precambrian rocks of 650 °C due to relatively high rates of heat production (0.9–1.4 μW m−3). In contrast, temperatures within dominantly Phanerozoic crust reach only 520 °C at the Moho due to the low rates of heat production in Cambrian mafic volcanics. A combination of the Curie depth and heat flow data is required to constrain the uncertainty of lower crustal temperatures to ±73 °C. We also show that parts of the crust are unconstrained if either data set is omitted from the inversion.