Analyse de variations minéralogiques par surfaces de tendance dans les tephra du volcan El Chichón (Chiapas, Mexique)

Jean-Paul Donnay & Etienne Juvigné
Quantitative analysis of minerals from 74 tephra samples of the March-April 1982 eruption of El Chichón have been submitted to multivariate statistical techniques. Variations in mineralogical content have been mapped by trend surfaces and maps of residual values have been drawn. A progressive sorting of the minerals during transport in the atmosphere has been firmly demonstrated; this sorting depends on both specific gravity and shape of the grains. Exceptionally high turbulence in the vicinity of...