[Folda] Fwd: [Jhi] Friday seminar - today 12:30 - Maren Kahl "Accessing the dynamic evolution of magma plumbing systems by kinetic and thermodynamic modelling - a case study from Mt. Etna"

[Deirdre Clark]

Today's Friday seminar at 12:30 is by Maren Kahl on "Accessing the dynamic
evolution of magma plumbing systems by kinetic and thermodynamic modelling
- a case study from Mt. Etna"

Abstract below.

---------- Forwarded message ----------
From: Maria H. Janebo <janebo at hi.is>
Date: Fri, Feb 24, 2017 at 9:32 AM
Subject: [Jhi] Friday seminar - today 12:30 - Maren Kahl "Accessing the
dynamic evolution of magma plumbing systems by kinetic and thermodynamic
modelling - a case study from Mt. Etna"
To: jhi at hi.is


Dear all,

the Friday seminar series continues today (24 February) at 12:30 in the
seminar room on the 3rd floor with a presentation given by:

*Maren Kahl **"Accessing the dynamic evolution of magma plumbing systems by
kinetic and thermodynamic modelling - a case study from Mt. Etna"*

Deciphering the evolution of the internal dynamics of magmatic plumbing
systems and identifying the key parameters that drive the dynamics are
major goals of volcanology. A novel petrological approach that combines
kinetic modelling of the diffusive relaxation of chemical zoning patterns
in olivine crystals with thermodynamic modelling (MELTS [1, 2]) to
constrain the thermodynamic parameters (e.g. P, T, water content, oxygen
fugacity and bulk composition of melt) of magma storage beneath Mt. Etna
between 1991 and 2008, and before and during the devastating 1669 flank
eruption are presented [3-5]. The compositional and temporal record
preserved in 382 olivine crystals and the mineral chemistry of associated
clinopyroxene, plagioclase and Fe-Ti oxides was studied. The minerals span
a wide compositional range and show a large variability (e.g. a single thin
section can contain olivines showing four different compositional ranges
and zoning patterns). Detailed systemization of the information stored in
the sequential zoning record of the olivines reveal the existence of at
least 6 compositionally different magmatic environments (MEs),
characterized by different olivine core and rim plateau compositions: M0
(=Fo79-83), M1 (=Fo75-78), M2 (=Fo70-72), M3 (=Fo65-69), mm1 (=Fo73-75) and
M5(=Fo51-59). Several routes of magma transfer connecting these
environments could be derived. Modeling the diffusive relaxation of the
olivine zoning patterns reveals that the transfer of magma along such
routes can occur over fairly heterogeneous timescales ranging from days to
up to 2 years. Although some of the passageways have been sporadically
active in the months and sometimes years before an eruption, the magma
migration activity increases clearly in the weeks and days prior to an
eruptive event. A forward modeling approach was developed using
thermodynamic calculations with the MELTS software [1, 2] aiming to
identify the most plausible set of key intensive variables associated with
each of these MEs. It was found that temperature, water content, and
oxidation state, are the main distinguishing features of the different MEs [
5]. This method is applicable to recent as well as temporarily remote
eruptions and its application allows identification of different points of
residence of magma along certain pathways in a plumbing system as well as
the quantification of their environmental (e.g. water content, oxidation
state) and temporal (duration and timing of recharge of different MEs)
parameters.
[1] Ghiorso, M.S. & Sack, R.O. (1995). Contrib. Mineral. Petrol. 119,
197-212; [2] Asimow, P.D., Ghiorso, M.S. (1998). Am. Min. 83, 1127-1131;
[3] Kahl, M. et al. (2011). EPSL 308, 11-22; [4] Kahl, M. et al. (2013).
Bull. Volc. 75, 692; [5] Kahl, M. et al. (2015) Journ. Petrol. 56, 10,
2025-2068
_____________________________
Maria H. Janebo
Postdoctoral Research Fellow

Nordic Volcanological Center
Institute of Earth Sciences
University of Iceland, Askja 223
Sturlugata 7, 101 Reykjavik, Iceland


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-- 
Deirdre Clark, PhD Research Fellow
University of Iceland | Háskóli Íslands
Institute of Earth Sciences
Sturlugata 7, Askja, Room 235
101 Reykjavík, Iceland

+354 525 4275 (Office)
+354 690 5745 (Mobile)
dec2 at hi.is
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