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Posts by Hugh Rollinson

Book Review — Earth’s Oldest Rocks (2nd Ed)

The Earth’s oldest rocks are those which formed in the time interval 3.0–4.0 billion years ago in the mid- to early Archaean Eon. Traces of anything even earlier, which would be from the Hadean (>4.0 billion years ago), are fragmental and preserved only in detrital zircon grains and in the isotopic memory of now long-extinct isotope systems. The time interval 3.0–4.0 billion years ago is a crucial stage in Earth history, for this is when the first continents formed, when life began, and was a time during which tectonic processes were quite different from modern (Phanerozoic) plate tectonics due to the different thermal state of the young Earth.

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Geochemical Modelling of Igneous Processes – Principles and Recipes in R language*

Over the past few decades, igneous petrology has gained great power because geochemical modeling can now be used to test geological hypotheses. Technological advances have led to an exponential increase in high-quality geochemical data for igneous rocks and minerals, which is being used to decipher processes in the Earth’s crust and upper mantle. Particularly powerful have been the use of trace elements and radiogenic isotopes. The abundant geochemical data on rocks has been supported by experimental studies, particularly on the behaviour of trace elements, such that we now have a rich database of well-­determined mineral–melt partition coefficients which are used in much of the modelling. Of course, our models are just that: geochemical modelling does not always have the ability to produce a unique solution to a geological problem. Nevertheless, modelling offers a powerful way by which to place limits on a range of possible geological processes.

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