Applicability of large-ion lithophile and high field strength element basalt discrimination diagrams

Abstract

ABSTRACTBasalt discriminant diagrams have been used to identify the tectonic setting of basaltic magmatism since the 1970s and have played an important role in reconstructing paleotectonic environments. However, the significant increase in the availability of geochemical data has led to a reassessment of these diagrams, suggesting that some of the tectonic settings indicated by these diagrams are not accurate. Here, we use a database of global ocean island basalt (OIB), mid-ocean ridge basalt (MORB), and island arc basalt (IAB) geochemistry to propose a series of new tectonic discriminant diagrams based on the ratios of large-ion lithophile elements (LILEs) to high field strength elements (HFSEs). These new diagrams indicate that the LILE can be used to differentiate OIB, MORB, and IAB samples, meaning that LILE/HFSE ratios can discriminate between these basalts that form in different tectonic settings. Our new diagrams can correctly assign samples to OIB, MORB, and IAB categories more than 85% of the time, with the discrimination between OIB and MORB having an accuracy of slightly less than 85%.