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Chemical composition of altered and unaltered rocks. Histograms of mean chemical compositions of hydrothermally altered rocks (a,b) and unaltered precursors (c–f). Mean entropy, number of samples (n) and the standard error (se = standard deviation/) are shown for each group of rocks. Error bars show the mean + standard error of the mean element concentrations. Chemical data of unaltered rocks were taken from Smithies, Champion, van Kranendonk and Hickman [16].
