Data analytics for geochemical and petrogenetic study of an igneous province: A case study on Andean andesite, South America

Abstract

Genesis of Phanerozoic Andean andesite rocks is related to the subduction of the oceanic Nazca plate beneath the South American continental plate along the west coast of South America. Exploratory data analytics is done on whole-rock geochemical data of 3311 andesite rock samples collected from the Andes orogenic belt, extending from Argentina, Chile, Bolivia, Peru, and Ecuador to Colombia. Python programming has been used for the visualisation and interpretation of large volumes of geochemical data, and data-driven tectonomagmatic inferences for volcanism extending across the South American continent have been drawn with the help of data analytics. Interelemental diagrams with Zr as a fractionation index reveal relative immobility and incompatibility of several major elements, large ion lithophile elements, high field strength elements, and rare earth elements. The interelemental diagrams, correlation matrix and heat maps drawn for major elements reveal that except K₂O, TiO₂ and SiO₂, all major elements decrease with fractionation. Major element variation trends indicate that plagioclase and pyroxene were the major fractionating phases. The density plots give insight into the range of variation and data density of major and trace elements. Petrogenetic study reveals calc-alkaline, basaltic andesite to andesite, and back-arc tectonomagmatic environment for these volcanic rocks. Mantle source of Andean magma was enriched to primitive upper mantle. Around 25–30% partial melting of the upper mantle led to the genesis of the most primitive Andean magma.