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Compositional Trends at Bezymianny Volcano (1955-2008 eruptive period). Pavel Izbekov 1 and PIRE team 2. 1 Geophysical Institute, University of Alaska Fairbanks 2 http://gps.alaska.edu/PIRE/index.html. Historical perspective: JKASP was first. - PowerPoint PPT Presentation
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Compositional Trends at Bezymianny Volcano(1955-2008 eruptive period)
1 Geophysical Institute, University of Alaska Fairbanks
2 http://gps.alaska.edu/PIRE/index.html
Pavel Izbekov1 and PIRE team2
Historical perspective: JKASP was first
Historical perspective: Int. Volc. School
Partnership in International Research and Education (PIRE project)
PIRE-Kamchatka: Scientific goal
How an edifice collapse affects magma system of an active volcano and its following eruptive activity?
What can we learn about Mount St Helens looking at its Russian analogs – Bezymianny and Shiveluch?
Mineral assemblage vs. time
Juvenile clast from the pyroclastic flow of the catastrophic eruption. Note rimm ed
hornblende and dusty-zoned plagioclase. 3/30/56
0.4 mm0.4 mm
P lagioclase > H ornblende > O rthopyroxene > C linopyroxene > M agnetite > Ilmenite z
P lagioclase > H ornblende
± Q uart
O rthopyroxene > C linopyroxene > M agnetite Ilmenite± ±
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Tim e, ca lendar years
Hornblende core in a OPx-CPx-Mt aggregate of the May 9, 2006 andesite
HbHb
0.4 mm0.4 mm
X
X
Whole rock and matrix glass compositions
54
56
58
60
62
64
66
68
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Time of eruption, calendar years
SiO
2, w
t. %
, W
hole
roc
k
60
65
70
75
80
85
SiO
2, m
atrix
gla
ss
Whole rock
Martrix glass
4
4.5
5
5.5
6
6.5
7
7.5
8
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Time of eruption, calendar years
CaO
, w
t. %
, W
hole
roc
k
0
1
2
3
4
5
6
CaO
, m
atrix
gla
ss
Whole rock
Martrix glass
Whole rock and matrix glass compositions
Whole rock and matrix glass compositions
1
1.5
2
2.5
3
3.5
4
4.5
5
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Time of eruption, calendar years
MgO
, w
t. %
, W
hole
roc
k
0
0.5
1
1.5
2
2.5
3
MgO
, m
atrix
gla
ss
Whole rock
Martrix glass
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Time of eruption, calendar years
K2O
, w
t. %
, W
hole
roc
k
0
1
2
3
4
5
6
K2O
, m
atrix
gla
ss
Whole rock
Martrix glass
Whole rock and matrix glass compositions
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Time of eruption, calendar years
K2O
WR/K
2Ogl
ass
Whole rock and matrix glass compositions
What is the meaning of the observed compositional variations at Bezymianny?
Sequential withdrawal from the top of compositionally zoned magma system / column?
54
56
58
60
62
64
66
68
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Time of eruption, calendar years
SiO
2, w
t. %
, W
hole
roc
k
60
65
70
75
80
85
SiO
2, m
atrix
gla
ss
Whole rock
Martrix glass
Magma column goes backward?
Single basaltic injection in 1955?
54
56
58
60
62
64
66
68
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Time of eruption, calendar years
SiO
2, w
t. %
, W
hole
roc
k
60
65
70
75
80
85
SiO
2, m
atrix
gla
ss
Whole rock
Martrix glass
Requires effective but gradual admixture of mafic end-member to the 1956 magma. Convection of the crystal-rich magma would be problematic.
Repetitive / continuous basaltic injections through the 1956 magma body?
54
56
58
60
62
64
66
68
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Time of eruption, calendar years
SiO
2, w
t. %
, W
hole
roc
k
60
65
70
75
80
85
SiO
2, m
atrix
gla
ss
Whole rock
Martrix glass
What is the frequency of recharges? Before each eruption? What controls the composition of magma at the exit? What is the composition of the mafic end-member and where are the xenocrysts?
