Multidimensional Diagrams for Tectonic Discrimination of Igneous and Sedimentary Rocks

Abstract

As Chap. 11, this chapter is also based on our recent research and, therefore, represents a novel approach. No book has been written on this aspect yet except one little known in Spanish by Verma (Analisis estadistico de datos composicionales. Universidad Nacional Autonoma de Mexico, CDMX, 2016). Our first example is on a preliminary discrimination of two tectonic settings (mid-ocean ridge MOR and oceanic plateau OP) from a multi-dimensional discriminant function based on additive log-ratio (alr) transformed major elements in basic and ultrabasic rocks. The probability concept and respective calculations are explained. Two examples on Precambrian rocks from India highlight the application, in which Chitradurga greenstone belt showed a MOR setting and Punagarh (Aravalli Craton) had affinity of an OP setting. Another example is for the multi-dimensional discrimination of active (A) and passive (P) margins from modified or hybrid log-ratio (mlr or hlr) transformation of major elements (M) as well as combined major and trace elements (MT) in siliciclastic sediments. Similarly, multi-dimensional discrimination of three tectonic settings (arc, rift, and collision) from siliciclastic sediments is described. Construction of probability-based boundaries is also presented to help readers better understand the novelty of the multi-dimensional approach. More examples of multi-dimensional discrimination are included. The chapter concludes with the indications of how more improvements in the direction of geochemometrics could be achieved.