- Mafic crustal growth
- Mantle geochemical and thermal evolution
- Temporally restricted magmatic suites, with a focus on komatiites and intracratonic norites
- Platinum group element geochemistry and Re-Pt-Os isotopes
- Geochemistry and dating of chromite and chromitites
- Formation, crystallisation and differentiation of mafic magmas
I study ancient igneous rocks and minerals derived from them to try and understand the evolution of the Earth's mantle, crust and tectonics. I am currently PI of the ChroMCrust project, funded by a €1.5 million ERC starting grant, looking to reconstruct the growth of mafic continental crust throughout Earth's history and search for traces of Earth's mafic protocrust.
Jargon-free research interests
My research interests focus on the Earth’s crust, mantle and the magmas that form when the mantle melts. The mantle is the solid rocky portion of the Earth that extends from just below the crust (from a few kilometers to 90 km deep), to the Earth’s core roughly 2900 km below the surface. Under certain conditions this mantle rock can melt to form magma. These magmas move upwards into the crust where they can either erupt as a lava, or slowly freeze in a magma chamber to form a ‘cumulate’ rock. By studying ancient lavas, cumulate rocks, and minerals derived from these, that formed at different times in Earth history, my research aims to capture ‘snapshots’ of the temperature and composition of the Earth’s mantle, understand how and when the Earth's crust formed, and study how magmatic styles have changed throughout geological time. As a geochemist, I mainly study rocks by grinding them into a powder, dissolving them, and analysing their chemical composition with mass spectrometers. I specialise in analysing precious metals related to platinum. These elements are very rare near the Earth’s surface but common in the Earth’s core and in meteorites, so they can tell us about the processes that formed the Earth’s core, or the last stages of Earth formation when the Earth and Moon were being bombarded by giant meteorites.
Current and recent research projects
ChroMCrust - The chromite record of mafic crustal growth
Funded by the EU through a €1.5 million ERC starting grant
Understanding Earth's crustal growth is crucial to understanding the evolution of its tectonics, the birth of the first continents, and the fundamental changes that transformed Earth into a habitable planet. However, much of our understanding of Earth's crustal growth is predicated on a single mineral - zircon - that is strongly biased towards detecting felsic crustal growth. This is particularly problematic for the early Earth, where average crustal compositions were far more mafic than today, and the very first protocrust may be entirely undetectable using conventional methods. This project aims to access the mafic to ultramafic crustal growth record using detrital chromite preserved in sedimentary rocks from Archaean Cratons. Like zircon, chromite chemical compositions reflect the magmas that they crystallised from, and can be used to identify the provenance of the mafic portions of a sedimentary rock. Furthermore, they can be dated using Re-Os isotopes, to identify the age of eroded mafic terranes. The project has three main objectives:
1. Develop techniques to identify the age and composition of chromite sources in ancient sedimentary rocks.
2. Use a range of detrital chromite samples from sedimentary sequences in the Superior Craton, to reconstruct a mafic-ultramafic crustal growth curve for the craton.
3. Search for evidence of Earth's mafic protocrust in some of the oldest known chromite-bearing sedimentary rocks.
Geochemistry and origin of komatiites
Komatiites are enigmatic ultra-hot, ultramafic magmas, largely restricted to the Archaean eon. Following my PhD on the pristine 1.9 Ga Winnipegosis Komatiites, a rare example of Proterozoic komatiite magmatism, I have continued research on the origins of komatiites and what they can tell us about the evolution of the Earth’s mantle. Key outstanding questions I have addressed include the temperature evolution of the Earth’s mantle (Waterton et al., 2017), the relationship between basalts and komatiites (Waterton et al., 2020), how komatiites can and can’t be used to track mantle chemistry (Waterton et al., 2021), and the apparent absence of komatiites from certain cratons (Haugaard et al., 2021). I recently submitted an invited review on the geochemistry and origins of komatiites in collaboration with Nick Arndt.
Dating chromite and chromitite
Unlike intermediate and felsic rocks, which can be readily dated with zircon U-Pb geochronology, mafic rocks and ultramafic rocks in particular lack reliable, widely available geochronometers. I have recently worked on developing the use of the Re-Os system in chromite and chromitites to provide robust model ages both for ultramafic intrusions (Santosh et al., 2020; Han et al., 2021) and for detrital chromite grains (Haugaard et al., 2021). Although these are by necessity model ages, with typical systematic uncertainties of ± 100 Myrs for Archaean rocks, I have routinely achieved analytical repeatabilities of less than ± 10 Myrs for routine analyses. For high precision unspiked analyses, this can be improved to better than 2 Myrs. In ongoing work, I have paired the use of the Pt-Os system with Re-Os to resolve the age of high metamorphosed ancient ultramafic bodies from West Greenland, finding the first ‘concordant’ Re-Pt-Os ages for samples with low Re and Pt contents.
Age and origin of Archaean ultramafic enclaves
Many Archaean cratons are host to abundant ultramafic enclaves, dispersed throughout the regional orthogneisses or included within supracrustal belts. In the North Atlantic Craton of West Greenland, there has been considerable debate as to whether these represent intrusive ultramafic cumulates or slices of tectonically emplaced mantle. This has major implications for our understanding of Archaean tectonics, as tectonic emplacement of mantle could be a sign of ophiolite obduction and potentially plate tectonics.
My work on dunite lenses of the Isua Supracrustal Belt showed that these are ultramafic cumulates, undermining a key piece of evidence that Isua is an ophiolite formed in an Eoarchaean plate tectonic regime (Waterton et al., 2022). I am also working on the Ujaragssuit layered ultramafic intrusion, a TTG-hosted ultramafic enclave that has previously been interpreted as the oldest chromitite on Earth and is a candidate for the oldest terrestrial rock. By combining detailed field mapping, U-Pb zircon and high-precision Re-Pt-Os dating, we intend to address the age of the Ujaragssuit intrusion and understand the preservation of primordial isotopic anomalies at this location.
Petrogenesis of the intracratonic norite suite
The intracratonic norite suite is a temporally restricted magmatic style, comprising large noritic intrusions and dykes with ‘boninitic’ affinities. These mainly formed between 2.7 and 2.0 Ga, coinciding with the decline of komatiite production, and include many of the world’s largest metal deposits (e.g., Bushveld, the Great Dyke). Debate is ongoing as to whether these represent boninite-like melts formed by re-melting of previously depleted mantle, melting of sub-continental lithospheric mantle, or extensive crustal contamination of an ultramafic melt such as a komatiite or picrite, with major implications for the global tectonic regime during this period.
The 3.0 Ga Maniitsoq Norite Belt of West Greenland is an early example of this style of magmatism, forming before the main intracratonic norite suite. My work on the norite belt showed that these intrusions likely formed in a very different regime to the main intracratonic norite suite, with synchronous TTG and norite magmatism immediately followed by high grade metamorphism in an ‘ultra-hot’ orogenic setting (Waterton et al., 2020). However, the ‘boninite-like’ composition of these rocks can be clearly linked to large degrees of crustal assimilation due to intrusion of ultramafic melts into hot crust. By contrast, the ‘BN dykes’ of West Greenland are a classic example of intracratonic norite magmatism, forming well after the cratonisation of the North Atlantic Craton. In ongoing work, I am seeking to address whether these could have also formed through high degree crustal assimilation, and understand the temporally-restricted nature of this magmatic suite.
Employment & education
- 2022 – present: Assistant professor, University of Copenhagen, Denmark
- 2019 – 2022: Post-doctoral researcher, University of Copenhagen, Denmark
- 2018: Post-doctoral researcher, Metal Earth, University of Alberta, Canada
- 2013 – 2018: PhD, University of Alberta, Canada (Vanier Scholar)
- 2008 – 2012: BA (1st), MSci (1st), University of Cambridge, UK
Funding & Awards
- 2023 - 2028 ERC starting grant – ChroMCrust, 1.5 million EUR
- 2014 - 2017 Vanier Canada Graduate Scholarship, 150,000 CAD
- 2014 – 2017 President’s Doctoral prize of Distinction, 21,400 CAD
- 2013 – 2016 University of Alberta Doctoral Recruitment Scholarship, 15,000 CAD
- 2021–present: Ikuya Nishio, PhD, Kanazawa University/University of Copenhagen, co-supervisor with T. Morishita, K. Szilas. Expected defence date 02/2024.
- 2020–2023: Yuesheng Han, PhD, China University of Geosciences (Beijing)/University of Copenhagen, co-supervisor with M. Santosh, K. Szilas. Defended 14/05/2023.
- 2021–2023: Marie Katrine Traun, PhD, University of Copenhagen, co-supervisor with T. Waight, N. Søager. Defended 17/04/2022.
- 2021–2022: Martin Larsen MSc, University of Copenhagen, co-supervisor with Kristoffer Szilas. Defended 15/06/2022.
- 2019–2020: William Hyde MSc, University of Copenhagen, co-supervisor with Kristoffer Szilas. Defended 28/10/2020.
- 2019: Benjamin Linnebjerg BSc, University of Copenhagen, co-supervisor with Kristoffer Szilas.
Teaching & training
- 2022–2023 Volcanoes, magmas and their geochemistry (2nd year geology, University of Copenhagen). Responsible for designing and teaching entire course, 7.5 ECTS.
- 2019–2022 Using MELTS, a brief introduction (workshop for graduate students, post-docs, staff, University of Copenhagen). Responsible for entire course, ~1 ECTS equivalent.
- 2020 Core to Crust: Earth's Evolution and Processes (MSc course, University of Copenhagen). Responsible for ~1 ECTS of 7.5 ECTS total.
- 2016–present Trained over 25 students (BSc to PhD level), post-docs, and academic staff in lab techniques including EPMA, LA-ICP-MS, micro-XRF, and isotope dilution techniques.
- 2014 Teaching assistant. EAS 320, 3rd year Geochemistry. University of Alberta.