INVESTIGADORES
PETRINOVIC Ivan Alejandro
artículos
Título:
The Negra Muerta volcanic complex, southern Central Andes: geochemical characteristics and magmatic evolution of an episodic volcanic centre
Autor/es:
IVAN ALEJANDRO PETRINOVIC; RILLER, U.; BROD, A.
Revista:
Journal of Volcanology and Geothermal Research
Editorial:
Elsevier
Referencias:
Lugar: Amsterdam; Año: 2005 vol. 140 p. 295 - 320
ISSN:
0377-0273
Resumen:
This petrologic analysis of the Negra Muerta Volcanic Complex (NMVC) contributes to understanding the magmatic
evolution of eruptive centres associated with prominent NW-striking fault zones in the southern Central Andes. Specifically, the
geochemical characteristics and magmatic evolution of the two eruptive episodes of this Complex are analysed. The first one
occurred as an explosive eruption at 9 Ma and is represented by a strongly welded, fiamme-rich, andesitic to dacitic ignimbrite
deposit. The second commenced with an eruption of a rhyolitic ignimbrite at 7.6 Ma followed by effusive discharge of hybrid
lavas at 7.3 Ma and by emplacement of andesitic to rhyodacitic dykes and domes. Both explosive and effusive eruptions of the
second episode occurred within a short time span, but geochemical interpretations permit consideration of the existence of
different magmas interacting in the same magma chamber. Our model involves an andesitic recharge into a partially cooled
rhyolitic magma chamber, pressurising the magmatic system and triggering explosive eruption of rhyolitic magma. Chemical or
mechanical evidence for interaction between the rhyolitic and andesitic magma in the initial stages are not obvious because of
their difference in composition, which could have been strong enough to inhibit the interaction between the two magmas. After
the initial explosive stages of the eruption at 7.6 Ma, the magma chamber become more depressurised and the most mafic
magma settled in compositional layers by fractional crystallisation. Restricted hybridisation occurred and was effective between
adjacent and thermally equivalent layers close to the top of the magma chamber. At 7.3 Ma, increments of caldera formation
were accompanied by effusive discharge of hybrid lavas through radially disposed dykes whereby andesitic magma gained in
importance toward the end of this effusive episode in the central portion of the caldera. Assimilation during turbulent ascent
(ATA) is invoked to explain a conspicuous reversed isotopic signature (87Sr/86Sr and 143Nd/144Nd) in the entire volcanic series.
Therefore, the 7.6 to 7.3 Ma volcanic rocks of the NMVC resulted from synchronous and mutually interacting petrological
processes such as recharge, fractional crystallization, hybridisation, and Assimilation during Turbulent Ascent (ATA).
Therefore, the 7.6 to 7.3 Ma volcanic rocks of the NMVC resulted from synchronous and mutually interacting petrological
processes such as recharge, fractional crystallization, hybridisation, and Assimilation during Turbulent Ascent (ATA).
87Sr/86Sr and 143Nd/144Nd) in the entire volcanic series.
Therefore, the 7.6 to 7.3 Ma volcanic rocks of the NMVC resulted from synchronous and mutually interacting petrological
processes such as recharge, fractional crystallization, hybridisation, and Assimilation during Turbulent Ascent (ATA).