%0 Journal Article
%A García Romero, Emilia
%A Vegas Salamanca, Juana
%A Baldonedo, J.L.
%A Marfil Pérez, Rafaela
%T Clay minerals as alteration products in basaltic volcaniclasticdeposits of La Palma (Canary Islands, Spain)
%D 2005
%@ 0037-0738
%U https://hdl.handle.net/20.500.14352/49738
%X Clay minerals from several volcaniclastic environments including pyroclastic (tuffs), epiclastic (lacustrine, alluvial terraces,marine fan delta) and unconformity-related paleosols in La Palma (Canary Islands) were studied by XRD, SEM, TEM, HRTEMimaging and AEM. Clay minerals and their assemblages allowed us to distinguish between primary volcaniclastic basalticmaterial produced directly by pyroclastic eruptions and epiclastic volcaniclastic material derived from erosion of pre-existingvolcanic rocks. The clay fractions consist mainly of smectite with minor chlorite, mica, chlorite-smectite mixed-layers and talc.Phyllosilicates of the epiclastic units display wider compositional variations owing to wide variations in the mineralogicaland chemical composition of the parent material. Most of the phyllosilicates (mica, corrensite, talc and chlorite) are inheritedminerals derived from the erosion of the Basement Complex Unit, which had undergone hydrothermal alteration. Smectites ofthe epiclastic units are saponite and beidellite–montmorillonite derived from the hydrothermal Basement Complex Unit andfrom volcanic materials altered in the sedimentary environment. Conversely, clay minerals of unconformity-related paleosolsare dominated by smectite composed of variable mixtures of saponite and beidellite, which were formed by pedogeneticprocesses with later hydrothermal influence. The mineralogical association in the pyroclastic unit is dominated byhydrothermally formed smectite (beidellite–montmorillonite), zeolites and calcite. This paper contributes to the differentiationbetween pyroclastic and epiclastic volcaniclastic rocks of several depositional settings in a basaltic volcanic complex by theirclay minerals characterization.
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