![]() Applying our model to a data compilation of igneous rocks from Iceland and the Cascade Mountains effectively separates these into tholeiitic and calc-alkaline trends. We use this simple natural law to define a ‘Bowen-Fenner Index’ to quantify the degree to which an igneous rock belongs to either magma series. ![]() We show that the ‘Bowen and Fenner trends’ that characterise the calc-alkaline and tholeiitic types of magmatic environments can be approximated by a simple log ratio model based on three coupled exponential decay functions, for A = Na2O + K2O, F = FeOT and M = MgO, respectively. T1 - A genetic classification of the tholeiitic and calc-alkaline magma seriesĪB - The concept of the ‘magma series’ and the distinction between alkaline, calc-alkaline and tholeiitic trends has been a cornerstone in igneous petrology since the early 20th century, and encodes fundamental information about the redox state of divergent and convergent plate tectonic settings. ![]() By admin | | mainpost, vol19 | 0 comments
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