Thermoremanence acquisition and demagnetization for titanomagnetite under lithospheric pressures

Launay, Nicolas; Rochette, P.; Quesnel, Yoann; Demory, François; Bezaeva, N. S.; Lattard, Dominique

doi:10.1002/2017gl073279

Cited by 4 publications

(3 citation statements)

References 40 publications

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“…Some sedimentary rocks have shown strong dependence to metamorphism (Rochette, 1987), but it is mainly magnetite breakdown and pyrrhotite creation, which at high grade conserve magnetic susceptibility. Since none of our samples show any sign of such modifications, and given that magnetic sources can subsist even at great depth (Demory et al, 2013;Ferré et al, 2013;Li et al, 2015;Launay et al, 2017), it FIGURE 11 | Model of the crustal structure along profile C beneath the WAMA considering deep BIFs with remanence and without magnetic lower crust. The parameters are identical to the ones in Figure 8.…”

Section: Discussionmentioning

confidence: 97%

Iron Formations as the Source of the West African Magnetic Crustal Anomaly

et al. 2018

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The geological sources of major magnetic field anomalies are still poorly constrained, in terms of nature, geometry, and vertical position. A common feature of several anomalies is their spatial correlation with cratonic shields and, for the largest anomalies, with Banded Iron Formations (BIF). This study first unveils the magnetic properties of some BIF samples from Mauritania, where the main part of the West African magnetic anomaly is observed. It shows how strong the magnetic susceptibility and natural remanent magnetization for such rocks are. High Koenigsberger ratios imply that the remanent magnetization should be taken into account to explain the anomaly. A numerical modeling of the crust beneath this anomaly is performed using these constraints and both gravity and magnetic field data. A forward approach is used, investigating the depth, thickness and magnetization intensity of all possible crustal lithologies. Our results show that BIF slices can be the only magnetized crustal sources needed to explain the anomaly, and that they could be buried several kilometers deep. The results of this study provide a new perspective to address the investigation of magnetic field anomaly sources in other cratonic regions with BIF outcrops.

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Section: Discussionmentioning

confidence: 97%

Iron Formations as the Source of the West African Magnetic Crustal Anomaly

et al. 2018

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“…Magnetostriction increases strongly with the Ti content of magnetite and could result in a much stronger PRM acquisition for Ti‐substituted magnetites. This can lead to significantly higher crustal magnetizations when the TRM/PRM is acquired under pressure rather than at ambient pressure (Launay et al, ). This could have implications for the interpretation of magnetic anomalies in oceanic crust, where the main magnetic carriers are Ti‐magnetite (TM60).…”

Section: Discussionmentioning

confidence: 99%

Domain State and Temperature Dependence of Pressure Remanent Magnetization in Synthetic Magnetite: Implications for Crustal Remagnetization

Volk

Feinberg

2019

Geochem Geophys Geosyst

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Pressure remanent magnetization (PRM) is acquired when a rock is compressed in the presence of a magnetic field. This process can take place in many different environments from impact and ejection processes in space, to burial and subsequent uplifting of terrestrial rocks. In this study, we systematically study the acquisition of PRM at different pressures and temperatures, using synthetic magnetite in four different grain sizes ranging from nearly single‐domain to purely multidomain. The magnitude of the PRM acquired in a 300 μT field is, within error, independent of the domain state of the sample. We propose that the acquisition of a PRM is mainly driven by the magnetostriction of the magnetic material. We further show that compared to a thermal remanent magnetization, the acquisition of PRM in large multidomain grains can be quite efficient, and may represent a significant component of magnetization in low‐temperature–high‐pressure environments.

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“…Concerning the effect of eventual remanence, in the absence of magnetization measurements on samples from cores of deep drillings, one cannot really investigate it. A recent study has however shown that it should be taken into account in the middle and lower crusts (Launay et al, 2017(Launay et al, , 2018. Fig.…”

Section: Figurementioning

confidence: 99%

Joint modeling of potential-field data and geodynamic interpretation for northeast Algeria

Benhenni

Quesnel

Berguig

et al. 2019

Journal of African Earth Sciences

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of potential-field data and geodynamic interpretation for northeast Algeria. Journal of African Earth Sciences, Elsevier, 2019, 159, pp.(M. Hamoudi). AbstractThe crustal structure beneath the northeastern continental part of Algeria is still largely unknown. Here we use potential field data processing, modeling and interpretation in order to investigate the deep sedimentary layers of this area and the transition with the basement. Indeed the gravimetric and magnetic field maps unveil the main geological domains of North Algeria: the AlCaPeKa domain, the Tellian Nappes, the Atlas and the South-Atlasic Fault (SAF). Our modeling approach combines the prediction of gravimetric and magnetic field signals along 4 N-S profiles that cross those domains and using constraints from seismic lines. The resulting cross-sections reveal the roots of the main E-W tectonic detachments of this area: the northern Suture Zone, the Tell Front, and the SAF. It seems that they are all initiated in the lower crust, nearby the continental/oceanic crustal transition for the Suture Zone, and several tenths of kilometers south from this transition for the Tell Front and the SAF detachments. Using these detachments, the lower parts of the crust are sometimes uplifted to only 5 km deep in the crust, while the upper crust is sometimes thickened to reach 15 km of thickness. Large magnetization and density contrasts are observed right beneath the Suture Zone.

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Thermoremanence acquisition and demagnetization for titanomagnetite under lithospheric pressures

Cited by 4 publications

References 40 publications

Iron Formations as the Source of the West African Magnetic Crustal Anomaly

Iron Formations as the Source of the West African Magnetic Crustal Anomaly

Domain State and Temperature Dependence of Pressure Remanent Magnetization in Synthetic Magnetite: Implications for Crustal Remagnetization

Joint modeling of potential-field data and geodynamic interpretation for northeast Algeria

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