Paleomagnetism and rock-magnetism by Micro-Magnetic Tomography

Project Information

MIMATOM

Grant agreement ID: 851460

DOI

10.3030/851460

Project closed

EC signature date 24 September 2019

Start date 1 February 2020

End date 31 July 2025

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 785 000,00

EU contribution

€ 1 785 000,00

Coordinated by

UNIVERSITEIT UTRECHT
Netherlands

Periodic Reporting for period 4 - MIMATOM (Paleomagnetism and rock-magnetism by Micro-Magnetic Tomography)

Reporting period: 2024-08-01 to 2025-07-31

Summary of the context and overall objectives of the project

The Earth’s magnetic field protects our planet from harmful charged particles emitted by the Sun. Without this magnetic shield, the atmosphere would gradually erode and life as we know it would not be possible. Variations in the magnetic field also affect modern technology, from satellites to telecommunications and power networks. Understanding how the field has changed in the past is therefore important both for reconstructing Earth’s history and for anticipating future changes. Volcanic rocks are valuable archives of past magnetic field behavior, as tiny magnetic minerals within them can record the field when the rock cools. However, volcanic rocks contain many different types of magnetic grains, some of which preserve the field reliably while others do not. Traditional measurements average all these signals together, and unreliable grains often dominate, making much paleomagnetic data uncertain or unusable.

The MIMATOM project addressed this problem by developing a method to read the magnetic record at the level of individual grains, rather than whole samples. By combining high-resolution magnetic imaging with 3-dimensional X-ray microscopy, we can determine the magnetic moment of each grain separately and select only those that store the field faithfully. We built a dedicated laboratory equipped with a Quantum Diamond Microscope to map extremely weak magnetic fields at micrometer resolution, and developed fast computational methods that allow the properties of thousands of grains to be determined within minutes. In the final phase, we also showed that, in some cases, the internal magnetic domain state of a grain can be inferred from its measured stray field, linking magnetic imaging directly to theoretical simulations. The method was successfully applied to volcanic rocks from several well-dated geological settings, demonstrating that reliable magnetic information can be recovered where traditional methods fail.

In conclusion, MIMATOM has introduced an entirely new approach to paleomagnetic research. By focusing on individual magnetic grains, the project improves the accuracy of reconstructions of the Earth’s past magnetic field, establishes a lasting laboratory capability, and opens new directions for studying how magnetic minerals store information over geological time.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The MIMATOM project set out to develop Micro-Magnetic Tomography (MMT), a new method for extracting reliable records of the Earth’s magnetic field from volcanic rocks. This required solving several technical challenges: building and calibrating a Quantum Diamond Microscope (QDM), obtaining high-resolution 3D reconstructions using micro-CT, linking these datasets accurately, increasing the reliability of magnetic moment determinations, and making the computations efficient enough to analyze thousands of grains. All of these goals were successfully achieved. A dedicated QDM laboratory was established at Utrecht University and is now fully operational. High-resolution micro-CT imaging was obtained through the European EXCITE network. New computational routines now allow thousands of grain moments to be reconstructed in minutes rather than days, and a statistical framework identifies which grains reliably record the magnetic field while excluding those that do not.

With the method established, MMT was applied to geological case studies where conventional paleomagnetic approaches had yielded ambiguous results. These included Devonian pillow lavas, Ediacaran volcanic dykes (in collaboration with the University of Oslo), and Archaean dykes from Greenland. These applications showed that reliable magnetic information can be recovered selectively from individual grains, producing clearer reconstructions of the past magnetic field. In the final phase of the project, we demonstrated that, under favorable conditions, the internal magnetic domain structure of single grains can be inferred from their stray magnetic fields. This was enabled through collaboration with QZabre (Zurich), and it opens new research directions and forms the conceptual basis of the PI’s subsequent research proposals. The results of MIMATOM have been disseminated through peer-reviewed publications, conference presentations, workshops, and the organization of the 18th Castle Meeting on Paleomagnetism in Utrecht. The computational tools are openly available, and the QDM laboratory will remain in operation at Utrecht University, accessible to external researchers, ensuring continued development and use of the method beyond the project timeframe.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

During MIMATOM, all major technical, computational, and scientific developments needed to establish Micro-Magnetic Tomography (MMT) as a practical research method were successfully completed. The Quantum Diamond Microscope (QDM) laboratory at Utrecht University is now fully operational, with hardware optimizations that improve magnetic sensitivity and spatial resolution. At the same time, the inversion software was redesigned to exploit modern computational hardware, allowing the magnetic moments of thousands of grains to be reconstructed within minutes rather than days. This represents a significant advance beyond previous approaches, which could only analyze small numbers of grains at much slower rates.

The project also produced a statistical framework for evaluating which grains reliably record the Earth’s magnetic field, marking a conceptual shift from bulk sample averaging to selective interpretation of reliable magnetic carriers. In the final phase, we showed that, under favorable conditions, the internal magnetic domain state of individual grains can be inferred from their stray fields when combined with micromagnetic simulations. This directly links high-resolution magnetic measurements to theoretical models and has already informed subsequent funding proposals. Looking ahead, further publications will result from the Devonian pillow-lava and Ediacaran dyke case studies, as well as from the domain-state analyses currently in preparation. The QDM facility and the computational tools developed within MIMATOM will remain in active use and accessible to external researchers, supporting continued growth and new applications in Earth and planetary sciences.

The concept of Micromagnetic Tomography