Clay minerals as alteration products in basaltic volcaniclastic deposits of La Palma (Canary Islands, Spain)

Abstract

Clay minerals from several volcaniclastic environments including pyroclastic (tuffs), epiclastic (Iacustrine, alluvial terraces, marine fan delta) and unconfonnity-related paleosols in La Palma (Canary Islands) were studied by XRD, SEM, TEM, HRTEM imaging and AEM. Clay minerals and their assemblages allowed us to distinguish between primary volcaniclastic basaltic material produced directly by pyroclastic eruptions and epiclastic volcaniclastic material derived from erosion of pre-existing volcanic 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 mineralogical and chemical composition of the parent material. Most of the phyllosilicates (mica, corrensite, talc and chlorite) are inherited minerals derived from the erosion of the Basement Complex Unit, which had undergone hydrothermal alteration. Smectites of the epiclastic units are saponite and beidellite--montrnorillonite derived from the hydrothermal Basement Complex Unit and from volcanic materials altered in the sedimentary environment. Conversely, clay minerals of unconformity-related paleosols are dominated by smectite composed of variable mixtures of saponite and beidellite, which were formed by pedogenetic processes with later hydrothermal influence. The mineralogical association in the pyroclastic unit is dominated by hydrothermally formed smectite (beidellite-montmorillonite), zeolites and calcite. This paper contributes to the differentiation between pyroclastic and epiclastic volcaniclastic rocks of several depositional settings in a basaltic volcanic complex by their clay minerals characterization.

Spatial arrangement of soil mantle in Glacis de Buenavista, Mexico as a product and record of landscape evolution

“…Several earlier studies pointed to the hydrothermal alteration of volcanic rocks as the source of smectites and other 2:1 clays for pedogenesis (Mizota and Faure, 1998;García-Romero et al, 2005). Our earlier research of tephra-paleosol sequences in Nevado de Toluca (Central Mexico, some 50 km from Glacis de Buenavista) revealed the presence of smectites in minor quantities, which we attributed to inheritance from hydrothermally transformed volcanogenic minerals .…”

“…Finally, the palynological data indicate large-scale human impacts during at least last 3000 years. (Lozano- García et al, 2005), while abundant archeological materials illustrate the development of sedentary agrarian communities from the Formative period to the Classic and then Postclassic civilizations.…”

Elemental Compositions of Smectites Reveal Detailed Sediment Provenance Changes during Glacial and Interglacial Periods: The Southern Drake Passage and Bellingshausen Sea, Antarctica

“…Smectite clay minerals, a common product of chemical weathering of volcanic material or igneous rock under warm, humid conditions [1] and hydrothermal alteration of pyroclastic products [2,3], are ubiquitous in marine sediments [2]. Smectite has a range of various elemental compositions, such as nontronite (Fe-rich), saponite (Mg-rich), and montmorillonite-beidellite (Al-rich) [1,2].…”

Petrological study of the early Mesoproterozoic Glauconitic Sandstone and Olive Shale members from the Semri Group, Vindhyan Supergroup in Central India: Implications to input from intrabasinal felsic volcanic source and glauconitization

“…Thus, the rapid erosion of volcanic source rocks and the diagenetic alteration of the volcanic fragments likely produced the clay minerals. Fine‐grained volcanic ash also alters to clay minerals very rapidly (Garcı'a‐Romero, Vegas, Baldonedo, & Marfil, ). Under these favourable conditions the detrital volcanic material (glass, pumice, lithics, mica, and feldspars) transformed into clays such as illite and glauconite during the deposition of siliciclastics of Kheinjua Formation within the basin.…”