Publication Date:
2017-04-04
Description:
Generally, the intensity and magnitude of explosive
volcanic activity increase in parallel with SiO2 content.
Pyroclastic-flow-forming eruptions in the Colli Albani
ultrapotassic volcanic district (Italy) represent the most
striking exception on a global scale, with volumes on the
order of tens of cubic kilometres and K-foiditic compositions
(SiO2 even 〈42 wt.%). Here, we reconstruct the preeruptive
scenario and event dynamics of the ~456 ka
Pozzolane Rosse (PR) eruption, the largest mafic explosive
event of the Colli Albani district. In particular, we focus on
the driving mechanisms for the unusually explosive
eruption of a low-viscosity, mafic magma. Geologic,
petrographic and geochemical data with mass balance
calculations, supported by experimental data for Colli
Albani magma compositions, provide evidence for significant
ingestion of carbonate wall rocks by the Pozzolane
Rosse K-foiditic magma. Moreover, the scattered occurrence
of cored bombs in Pozzolane Rosse pyroclastic-flow
deposits records carbonate entrainment even at the eruptive
time scale, as also tested quantitatively by thermal modelling
of magma–carbonate interaction and carbonate assimilation
experiments. We suggest that the addition of free CO2 from
decarbonation of country rocks was the major factor
controlling magma explosivity. High CO2 activity in the
volatile component, coupled with magma depressurisation,
produced extensive leucite crystallisation at short time
scales, resulting in a dramatic increase in magma viscosity
and volatile pressurisation, which was manifested a change
of eruptive dynamics from early effusion to the Pozzolane
Rosse's highly explosive eruption climax.
Description:
INGV
Description:
In press
Description:
2.3. TTC - Laboratori di chimica e fisica delle rocce
Description:
JCR Journal
Description:
restricted
Keywords:
Mafic explosive eruptions
;
Eruption magnitude
;
Pyroclastic flow
;
Colli Albani
;
Potassic volcanism
;
Carbonate assimilation
;
05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Permalink
