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Updated: Nov 26, 2025

Atom Probe Tomography Analysis of Exsolved Mineral Phases
Published on: October 25, 2019
Titanium isotopes constrain a magmatic transition at the Hadean-Archean boundary in the Acasta Gneiss Complex
Sarah M Aarons1,2, Jesse R Reimink3,4, Nicolas D Greber5
1Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637, USA. smaarons@ucsd.edu.
Abstract:
Plate subduction greatly influences the physical and chemical characteristics of Earth's surface and deep interior, yet the timing of its initiation is debated because of the paucity of exposed rocks from Earth's early history. We show that the titanium isotopic composition of orthogneisses from the Acasta Gneiss Complex spanning the Hadean to Eoarchean transition falls on two distinct magmatic differentiation trends. Hadean tonalitic gneisses show titanium isotopic compositions comparable to modern evolved tholeiitic magmas, formed by differentiation of dry parental magmas in plume settings. Younger Eoarchean granitoid gneisses have titanium isotopic compositions comparable to modern calc-alkaline magmas produced in convergent arcs. Our data therefore document a shift from tholeiitic- to calc-alkaline-style magmatism between 4.02 and 3.75 billion years (Ga) in the Slave craton.
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