TecMagDiSys: A New Computer Program for Multidimensional Tectonomagmatic Discrimination

Abstract

AbstractThe tectonomagmatic classification began with the idea that magmas from different tectonic settings could be distinguishable in their chemistry. The previous models so far have been limited to the discrimination of a few tectonic settings at a time, usually two or four of the following: island and continental arcs, continental rift, ocean island, mid-ocean ridge, collision, and oceanic plateau. TecMagDiSys (Tectonomagmatic Discrimination System) is a new online software meant for deciphering a total of 29 igneous rock tectonic settings through two new comprehensive multidimensional discrimination models based on major elements (SiO2 to P2O5), and major and trace elements (SiO2 to P2O5, Cr, Nb, Ni, V, Y, and Zr). These models consist of a total of 56 discriminant function equations, 154 centroids, and 154 probability calculations. This lengthy and complex procedure indicates that the application of these models without a suitable computer program is impracticable. For this reason, it was considered necessary to develop a computer program for an efficient, accurate, and routine application of these diagrams. As far as is known, there is no other program to classify so many tectonic settings at the same time. TecMagDiSys is structured in three modules: (i) tectonomagmatic discrimination applies the discriminant functions and centroids and estimates the probabilities; (ii) uncertainty propagation simulates independent analyses from the Monte Carlo procedure in terms of the mean composition and analytical errors of any given individual analysis; (iii) the module on the post-emplacement changes simulates new compositions from post-emplacement alteration-related changes (gain or loss of single or multiple elements) of any given sample. TecMagDiSys was developed in Java and ZK Framework, which is available for direct use at the web portal http://tlaloc.ier.unam.mx/tecmagdisys. This program can run on any conventional computer regardless of its platform or operating system. This program requires an input Excel® file, for it, the user must prepare an input file containing chemical concentration for major (SiO2 to P2O5 for M model) or combined major and trace (Cr, Nb, Ni, V, Y, and Zr for MT model) elements. It is recommended to download the appropriate template from this portal. TecMagDiSys provides an extended report for individual samples and a summary report for a given dataset. The usefulness of this comprehensive multidimensional scheme was validated from eight application cases. (i) Miocene rock samples from Nosy Be archipelago of northern Madagascar and Afyon volcanic province of Turkey; (ii) Cretaceous basement rock samples from Deep Sea Drilling Project Sites 417 and 418 of the western Atlantic Ocean; (iii) Late Triassic to Late Cretaceous basaltic lavas from the Neotethyan suture zone ophiolites in western Turkey; (iv) Neoarchean to Paleo-Archean rock samples from the Isua greenstone belt (West Greenland), Melville Peninsula (Nunavut, Canada), Bastar mafic dike of central Indian craton, and Serra do Rabo granite stocks in Carajás Metallogenic Province (Brazil). Hence, the use of TecMagDiSys software is recommended in any future applications for probability-based inferences on tectonic settings.KeywordsIgneous rocksLinear discriminant and canonical analysisLog-ratio transformationMultidimensional classificationTectonomagmatic discrimination