Abstract
Magmatic processes have usually been identified and evaluated using qualitative or semiquantitative geochemical or isotopic tools based on a restricted number of variables. However, a more complete and quantitative view could be reached applying multivariate analysis, mass balance techniques, and statistical tests. As an example, in this work a statistical and quantitative scheme is applied to analyze the geochemical features for the Sierra de las Cruces (SC) volcanic range (Mexican Volcanic Belt). In this locality, the volcanic activity (3.7 to 0.5 Ma) was dominantly dacitic, but the presence of spheroidal andesitic enclaves and/or diverse disequilibrium features in majority of lavas confirms the operation of magma mixing/mingling. New discriminant-function-based multidimensional diagrams were used to discriminate tectonic setting. Statistical tests of discordancy and significance were applied to evaluate the influence of the subducting Cocos plate, which seems to be rather negligible for the SC magmas in relation to several major and trace elements. A cluster analysis following Ward's linkage rule was carried out to classify the SC volcanic rocks geochemical groups. Finally, two mass-balance schemes were applied for the quantitative evaluation of the proportion of the end-member components (dacitic and andesitic magmas) in the comingled lavas (binary mixtures).
Highlights
IntroductionGeochemical, and isotopic tools, using a limited number of variables (e.g., bivariate, trilinear, multielement, and semilogarithmic diagrams), have usually been applied to establish a qualitative or semiquantitative view of igneous petrological mechanisms [1, 2]
Several conventional mineralogical, geochemical, and isotopic tools, using a limited number of variables, have usually been applied to establish a qualitative or semiquantitative view of igneous petrological mechanisms [1, 2]
Unlike other sets of diagrams, a continental arc setting can be inferred from those based on immobile trace elements (n = 10; % prob = 39.7; Table 4 and Figure 5)
Summary
Geochemical, and isotopic tools, using a limited number of variables (e.g., bivariate, trilinear, multielement, and semilogarithmic diagrams), have usually been applied to establish a qualitative or semiquantitative view of igneous petrological mechanisms [1, 2]. Verma [21] and Verma et al [22], to solve the limitations of the tectonic discrimination conventional schemes, have proposed a set of new discriminant-function-based multidimensional diagrams for intermediate and acid magmas from four tectonic settings (island arc, continental arc, continental rift + ocean island, and collision) In this context, Velasco-Tapia et al [23] recently reported, based on mineralogical, geochemical, and Sr-Nd isotopic conventional tools, that the formation of the Sierra de las Cruces (SC) volcanic range (3.7 to 0.5 Ma; central part of the Mexican Volcanic Belt (MVB); Figure 1) was mainly controlled by a magma mixing/mingling process. As an example, multivariate techniques (linear discriminant, cluster, and principal component analysis), discordancy and significance statistical tests, and mass-balance approaches were applied to establish the tectonic setting and to obtain a quantitative picture of the magmatic evolution of this volcanic range
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