Cored bombs, a kind of pyroclast consisting of a lithic core surrounded by a chilled shell of juvenile material, record the thermal interaction of magma with wall rocks. We performed textural analysis of cored bombs, solid-melt heat-transfer theoretical modelling, and high-temperature coating experiments to put temporal and intensity constraints on the thermal interaction of potassic magma feeder systems with carbonate wall rocks during explosive eruptions in the Quaternary, Colli Albani Volcanic District (Roman Province). It appears that the degree of thermal alteration of lithic cores records the duration of magma-core heat transfer, whereas the core/shell size ratio records the initial entrainment temperature of the lithic fragment. Both parameters appear to vary significantly with the eruptive style, magnitude and vent location. Specifically, small-scale (similar to 0.1-1 km(3) DRE) hydromagmatic eruptions show magma-core heat-transfer durations of 0.1-10 s and entrainment temperatures in the range of 100-300 degrees C in the case of a monogenetic maar located in the Colli Albani peripheral area, while entrainment temperature is as high as to 800 degrees C for a polygenetic maar in a high-enthalpy geothermal system at the margins of the main Colli Albani magma chamber. A large-scale (similar to 30 km(3) DRE) caldera-forming explosive event shows magma-core heat-transfer duration in the order of 10(2)-10(3)s and temperature of 100-500 degrees C at the initial magma-wall rock contact. On these grounds, we derived the cooling rate of magmas as a function of the initial temperature, mass and size distribution of lithic clasts entrained. Magma cooling by lithic entrainment may have occurred on the same time-scale as that of eruptive pulses (seconds to hours), implying that lithic entrainment may effect changes in magma physico-chemical properties on a short time-scale and, consequently, affect eruptive conduit dynamics. (C) 2010 Elsevier B.V. All rights reserved.
Constraints on magma-wall rock thermal interaction during explosive eruptions from textural analysis of cored bombs / Sottili, Gianluca; J., Taddeucci; Palladino, Danilo Mauro. - In: JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH. - ISSN 0377-0273. - STAMPA. - 192:1-2(2010), pp. 27-34. [10.1016/j.jvolgeores.2010.02.003]
Constraints on magma-wall rock thermal interaction during explosive eruptions from textural analysis of cored bombs
SOTTILI, Gianluca;PALLADINO, Danilo Mauro
2010
Abstract
Cored bombs, a kind of pyroclast consisting of a lithic core surrounded by a chilled shell of juvenile material, record the thermal interaction of magma with wall rocks. We performed textural analysis of cored bombs, solid-melt heat-transfer theoretical modelling, and high-temperature coating experiments to put temporal and intensity constraints on the thermal interaction of potassic magma feeder systems with carbonate wall rocks during explosive eruptions in the Quaternary, Colli Albani Volcanic District (Roman Province). It appears that the degree of thermal alteration of lithic cores records the duration of magma-core heat transfer, whereas the core/shell size ratio records the initial entrainment temperature of the lithic fragment. Both parameters appear to vary significantly with the eruptive style, magnitude and vent location. Specifically, small-scale (similar to 0.1-1 km(3) DRE) hydromagmatic eruptions show magma-core heat-transfer durations of 0.1-10 s and entrainment temperatures in the range of 100-300 degrees C in the case of a monogenetic maar located in the Colli Albani peripheral area, while entrainment temperature is as high as to 800 degrees C for a polygenetic maar in a high-enthalpy geothermal system at the margins of the main Colli Albani magma chamber. A large-scale (similar to 30 km(3) DRE) caldera-forming explosive event shows magma-core heat-transfer duration in the order of 10(2)-10(3)s and temperature of 100-500 degrees C at the initial magma-wall rock contact. On these grounds, we derived the cooling rate of magmas as a function of the initial temperature, mass and size distribution of lithic clasts entrained. Magma cooling by lithic entrainment may have occurred on the same time-scale as that of eruptive pulses (seconds to hours), implying that lithic entrainment may effect changes in magma physico-chemical properties on a short time-scale and, consequently, affect eruptive conduit dynamics. (C) 2010 Elsevier B.V. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
