An important step in scientific petrography
Abstract
(Regarding Bowen's book "The later stages of the evolution of the igneous rocks"). The author of this note has long distinguished, among igneous rocks, between normal ones with more or less strict signs of chemical equilibrium and anomalous ones, which are not subject to any laws of equilibrium or any strict scientific classification, but bear clear signs of a sequential course of phenomena, the sequence of which, thanks to them, can be elucidated. Such rocks can only be described, and from the description, historical and geological dates can be deduced. Now, after the publication of Bowen's important work, one involuntarily inclines to the thought of the very weak representation of normal rocks, and perhaps even their absence; in nature, only approximations to them are represented, which is why they should rather be regarded not as normal, but as ideal.
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