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Titre du document / Document title

Dynamics of the ca. 4965 yr 14C BP "Ochre Pumice" Plinian eruption of Popocatépetl volcano, Mexico

Auteur(s) / Author(s)

ARANA-SALINAS Lilia (1) ; SIEBE Claus (1) ; MACIAS José Luis (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Departamento de Vulcanologia, Instituto de Geofísica, Universidad Nacional Autónoma de México, Coyoacán, C.P. 04510, México, MEXIQUE

Résumé / Abstract

The Ochre Pumice (OP) Plinian fallout was produced by Popocatépetl volcano in central Mexico, during a major Plinian eruption that occurred 4965±65 14C yr BP (3700 BC). The OP is part of the Ochre Pumice Sequence (OPS), that consists of surge, fall, and pyroclastic flow deposits. The OP Plinian fallout shows a bimodal grain size distribution with poor to moderate sorting that improves progressively towards the upper beds. The juvenile component is mainly pumice (>83 wt.%), whereas the accidental components consist of igneous, sedimentary, and metamorphic clasts from the walls of the magma chamber and/or conduit. The vesicularity of the pumice decreases from bottom to top of the stratigraphic sequence while the crystal and glass contents increase. This suggests increasing magma degassing prior and during the eruption. The chemical composition of the pumice varies insignificantly; at the base it is less evolved (SiO2 = 61 wt.%) and it becomes slightly more silicic towards the top (SiO2 = 63 wt.%). Pumice clasts have a crystallinity index that ranges between 10 and 25 vol.% and display a seriate texture with phenocrysts of euhedral plagioclase (PI) + clinopyroxene (Cpx)+orthopyroxene (Opx) + olivine (01) ± oxide (Ox) ± apatite (Ap). The size of the maximum lithic (2.5 cm) at a horizontal distance of 19 km indicates an eruption column height of 37-41 km. The isopach map allows the recognition of a dispersal axis that points towards the NNE, where an area of ∼300 km2 was covered by >6 cm of pumice and ash. A minimum volume for the OP Plinian fallout deposit was calculated using a minimum thickness of 6 cm found at distal outcrops, and was estimated at ∼4.9 km3 which corresponds to 2 km3 of dense rock equivalent (DRE). Stratigraphic relations indicate that the entire OPS was emplaced during a short time interval of a few days to weeks and consisted of three main different phases: phreato-magmatic, Plinian, and vulcanian. It started violently with the emplacement of surges and then culminated with the eruption of the OP fallout deposit. As the eruption advanced, discharge rates became more intermittent and the height of the column fluctuated and finally collapsed, generating pumice-and-ash flows that were emplaced around the volcano. This short but intense activity was followed during subsequent years by the growth of domes in the crater and the emplacement of block-and-ash-flows generated by vulcanian explosions.

Revue / Journal Title

Journal of volcanology and geothermal research    ISSN  0377-0273   CODEN JVGRDQ 

Source / Source

2010, vol. 192, no3-4, pp. 212-231 [20 page(s) (article)] (1 p.1/2)

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Oxford, ROYAUME-UNI  (1976) (Revue)

Mots-clés anglais / English Keywords

North America

;

Mexico

;

phosphates

;

nesosilicates

;

chain silicates

;

pyroxene

;

silicates

;

framework silicates

;

feldspar

;

igneous rocks

;

volcanic rocks

;

pyroclastics

;

Popocatepetl

;

outcrops

;

thickness

;

ash

;

isopach maps

;

apatite

;

oxides

;

olivine

;

clinopyroxene

;

plagioclase

;

phenocrysts

;

crystallinity

;

chemical composition

;

degassing

;

magmas

;

crystals

;

vesicular texture

;

magma chambers

;

clasts

;

graded bedding

;

size distribution

;

grain size

;

pyroclastic flows

;

fallout

;

plinian-type eruptions

;

pumice

;

Mots-clés français / French Keywords

Amérique du Nord

;

Mexique

;

Phosphate

;

Nésosilicate

;

Inosilicate

;

Pyroxène

;

Silicate

;

Tectosilicate

;

Feldspath

;

Roche ignée

;

Roche volcanique

;

Pyroclastite

;

Volcan Popocatepetl

;

Affleurement

;

Epaisseur

;

Cendre

;

Carte isopaque

;

Apatite

;

Oxyde

;

Olivine

;

Pyroxène clino

;

Plagioclase

;

Phénocristal

;

Cristallinité

;

Composition chimique

;

Dégazage

;

Magma

;

Cristal

;

Texture vésiculaire

;

Chambre magmatique

;

Claste

;

Granoclassement

;

Distribution dimension

;

Dimension grain

;

Coulée pyroclastique

;

Retombée

;

Eruption type plinien

;

Ponce

;

Mots-clés espagnols / Spanish Keywords

America del norte

;

México

;

Fosfato

;

Piroxeno

;

Silicato

;

Feldespato

;

Roca ignea

;

Roca volcánica

;

Afloramiento

;

Espesor

;

Ceniza

;

Apatito

;

Óxido

;

Olivino

;

Piroxeno clino

;

Plagioclasa

;

Fenocristal

;

Cristalinidad

;

Magma

;

Cristal

;

Textura vesicular

;

Cámara magmática

;

Clasto

;

Granoselección

;

Dimensión grano

;

Lluvia radioactiva

;

Piedra pómez

;

Mots-clés d'auteur / Author Keywords

Popocatépetl

;

Plinian eruption

;

Ochre Pumice

;

eruptive history

;

radiocarbon dating

;

Localisation / Location

INIST-CNRS, Cote INIST : 17236, 35400018108879.0080

Nº notice refdoc (ud4) : 22758372



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