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The Oldest Rocks on Earth

The Carlsberg Foundation Distinguished Fellowships

What

The overriding objective of this project is to gain new insights into Earth's earliest crustal evolution, and the composition of the meteoritic source from which our planet accreted. This will be accomplished by studying the oldest rocks known on Earth, which happens to be found in the Nuuk-region of SW Greenland. A recent re-analysis of existing samples from a unique locality in SW Greenland indicates that these rocks may be as old as 4.1 billion years based on their Pt/Os isotopic ratios. Furthermore, they carry anomalous Ru-isotopic compositions, which has never been recorded in terrestrial rocks until now, and which is a feature, only known from certain types of meteorites.

Why

It is critical to establish the mechanism by which Earth's oldest rocks formed, because this has important implications for both geochemical and geophysical models of the tectonic regimes that operated during the earliest part of Earth's history. These particular samples from Greenland can yield entirely new constraints on the meteoritic building blocks of our planet, as well as unique insights on the formation mechanism of Earth's first primitive crust. The fundamental research questions that the present study will address, can have enormous scientific impact throughout the field of geosciences, with implications for the origin of Earth's oceans, and when our planet became habitable.

How

The research project will mainly be carried out at the Department of Geosciences and Natural Resource Management, University of Copenhagen. However, there will also be collaboration with leading researchers in Canada and Germany. We will generate a comprehensive petrological and geochemical data set for these ancient rocks. First we will focus on isotope systems relevant for age determination (Lu/Hf and Pt/Os), but we will then apply various non-traditional isotope systems like Cr, V, Ru. By this, we hope to calculate the composition of Earth's proto-crust prior to large scale crustal differentiation, which may help us identify the type of meteoritic reservoir that Earth formed from.

SSR

Greenland is unique by covering a geological history that stretches from as far back in time as the rock record goes, and all the way to the latest glaciation, and even recent anthropogenic influences. The study of Greenland's geology will lead to a better understanding of the processes that operation since the emergence of the continents, and the mechanisms by which they were subsequently reprocessed. This has important implications for modelling the type and size of metal deposits, as well as for predicting their occurrence within Greenland. Better constraints on geological commodities will provide a more nuanced and realistic perspective on the mining potential in Greenland.