Fig. 4: Coupling of mafic igneous geochemical evolution and atmospheric oxygenation.
From: Reconstructing Earth’s atmospheric oxygenation history using machine learning
a Self-organizing map (SOM) classification of mafic igneous compositional evolution through time using four clusters (red line). The blue box shows a “classical two-step” view of atmospheric oxygen evolution10. Arrows denote possible “whiffs” of O2 in the Late Archaean. b The first principal component (PCA1) of mafic igneous compositional evolution through time (red line), gradual step increases in atmospheric O2 suggested by Campbell and Allen46 (blue solid line), and numbers of continental large igneous provinces (LIPs)78. c Four stages of plate tectonics evolution43; orange curve represents variation in the thickness of new continental crust through time, and blue line is for secular cooling of mantle temperature.
