Resumo

DIAZ-GONZALEZ, Lorena  e  CRUZ-HUICOCHEA, René. Application of discordancy and significance statistical tests for the comparison of dacitic volcanism from the central part of the Mexican Volcanic Belt. Nova scientia [online]. 2014, vol.6, n.11, pp.158-178. ISSN 2007-0705.

Our aim is to show a statistical procedure along with two new computer programs (DODESSYS and UDASYS). For this task we compiled a database of 249 samples of dacite coming from four closely located Mexican Volcanic Belt (MVB) areas: monogenetic volcanoes from the Sierra de Chichinautzin and Valle de México, the Nevado de Toluca stratovolcano, the Iztaccíhuatl stratovolcano and the Popocatépetl stratovolcano. The discordancy and significance (ANOVA -ANalysis Of Variance-, Fishers' F and Student's t) statistical tests were applied at 99% confidence level. The final statistical was calculated for 98 geochemical parameters, these include major oxides, rare earth elements, trace elements and additional parameters, as well as log-ratio parameters used in new tectonic discrimination diagrams. These geochemical parameters were treated as univariate statistical samples and were classified according with the four MVB regions. Discordancy statistical tests detected discordant outliers in 124 (amount to about 35%) statistical samples. ANOVA tests showed significant differences among all groups in 32 parameters. The similarities and differences between the log-ratios parameters elements may eventually be useful in future to propose tectonic discrimination diagrams from a representative database.

Palavras-chave : ANOVA; Fisher's F; Student's t; discordant outliers; geochemical data; statistical handling of compositional data.

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