Boise State University
ScholarWorks
College of Arts and Sciences Poster Presentations
2017 Undergraduate Research and Scholarship
Conference
4-17-2017
Petrogenesis of Cinder Cones on Villarrica
Volcano, Southern Chile
Jordan Engstrom
Petrogenesis of Cinder Cones on Villarrica Volcano, Southern Chile
By Jordan
1
Engstrom
1
Wanless
and Dr. Dorsey
Boise State University Department of Geosciences, Boise, ID 83725
Introduction
Study Site
The goal of this project is to determine the compositional heterogeneity of
lavas erupted along a fissure system at Villarrica Volcano. Variations in
geochemistry (major and trace elements) are used to evaluate the role of
fractional crystallization down the fissure system.
• 12 samples were collected from Villlaririca:
• 10 samples along a NE-SW trending cinder cone fissure
system noted by
on the map
• 2 tephra from the 2015 eruption (9a and 9b)
Major Elements
Villarrica Volcano, Chile
Crystallization Trends
8.5
6
8.3
1.15
9B
2
1.10
7
9A
8
7.9
4
7.7
3.0
4
4.5
5
5.5
1
3
8
14
9A
6
2
5
1
8.6
1
14.5
9B
13.5
1
13
7
3
8
8.4
4
6
8.2
8
2
5
4
4.5
5
MgO wt %
5.5
2.8
1
3.5
4
4.5
5
5.5
6
2.75
1
2.7
4
0.6
1
5
5.5
Sample/Chondrite
30
4
8
29
3
3.5
9
3
• Sc3+ substitutes into CPX
for Fe3+
9
1
5
28
3.5
4
4.5
5
5.5
6
7
3
1.15
1
2
4.5
5
MgO wt %
5.5
6
6
9
8
1.05
4
1
0.95
5
2
0.9
Fe-oxide crystallization
9
1.1
4
7
MgO wt %
0.55
6
1
1
3
1
0.625
Clinopyroxene crystallization
1
3
• Fractionating oxides
supported by FeO* plot
7
1
0.85
3
3.5
4
4.5
5
5.5
6
MgO wt %
Conclusions
• Are lavas from a single cinder cone compositionally similar?
• In a single cone, samples are heterogeneous and show
evidence for crystallization
• Can any differences be explained by fractional crystallization?
• Geochemical evidence for crystallization of olivine,
plagioclase, clinopyroxene, and Fe-oxide
• Are lavas from the entire fissure system compositionally similar?
• Samples are compositionally heterogeneous
10
Future Research
1
La Ce Pr Nd
6
5.5
4.5
6
4
8
-71.845
-71.840
3
1
2
-71.835
Longitude
-71.830
0.88
-71.825
E
1
0.87
2
8
1
1
4
7.5
7.25
5
-71.845
-71.840
W
Eu/Eu*
6
7
7.75
7
-71.850
• Lavas have parallel REE patterns, consistent with fractional crystallization
• Europium anomaly evidence for plagioclase crystallization
5
4
1
0.86
8
FeO*
4
5
W
8.25
• Pick sample for more accurate major element contents with XRF
Yb Lu
REE
5
3.5
-71.850
Sm Eu Gd Tb Dy Ho Er
7
8.5
• Villarrica is a subduction zone
volcano in Southern Volcanic
Province of Chile
• Most active volcano in Chile
(Palma et al., 2008)
• Basaltic-basaltic andesite
stratovolcano (Leach, 2012)
• Last eruption: March 3, 2015
• 42 recorded eruptions since 1900
5
6
6
31
6
Rare Earth Element Concentration
100
Compositions vs. Longitude
Villarrica Volcano
www.PosterPresentations.com
4.5
5.5
2
0.65
0.575
4
5
27
Trace Elements
12 samples collected from Villarrica in March 2015
3 samples collected from cone 1 to evaluate heterogeneity
Processed by crushing, sieving, cleaning, and picking
Weighed and dissolved samples for analyses
Measured major and trace elements by solution ICP-MS
MgO wt %
• Example of a typical fissure system sample
• Fissure system samples are more oxidized and
weathered than the 2015 tephra
RESEARCH POSTER PRESENTATION DESIGN © 2015
7
GPS Coordinates: 39.40° S, 71.84° W
4
Proyecto De Observacion Villarrica (POVI, 2015)
1
5
3.5
8
0.675
4
2.65
9B
9A
• Lavas have a range of major element contents, indicating that they are
compositionally distinct
• Differences may be attributed to fractional crystallization
•
•
•
•
•
1 cm
3
2
0.7
9B
4.5
32
MgO wt %
9A
4
33
3
6
2
3
5 4
3.5
6
1
34
7
6
K2O wt %
Na2O wt %
8
2
1
9B
1
0.725
2.85
8
• Ni2+ substitutes for Mg2+
in olivine
MgO wt %
Sc ppm
3.5
Olivine crystallization
7.8
MgO wt %
Methods
6.0
9
30
7.4
2.9
• Samples 9A and 9B are from the 2015 eruption
• Glassier than fissure samples
40
9A
0.75
1 cm
5.5
9
3
1
Fissure System
9A
5.0
50
20
7.6
12.5
3
4.5
7
1
TiO2 wt %
Al2O3 wt %
4
8.8
CaO wt %
15.5
2.6
4.0
6
Ni ppm
3.5
MgO wt %
3
3.5
60
3
GPS Coordinates: 39.43° S, 71.94° W
3
0.85
6.9
• Are lavas from the entire fissure system compositionally similar?
• Are lavas from a single cinder cone compositionally similar?
• Can differences be explained by fractional crystallization?
0.90
1
3
5
1
7.1
15
5
1
• Eu2+ substitutes into
plagioclase for Ca2+
7
MgO wt %
7.3
Research Questions
6
1
0.95
1
Plagioclase crystallization
9
8
4
1.00
1
7.5
Examining the composition along the fissure will allow us to determine if
the fissure samples are related to each other and the 2015 tephra.
1.05
Eu wt %
FeO* wt %
8.1
9
2
3
-71.835
Longitude
0.85
3
2
1
0.84
8
-71.825
E
9
• Lava compositions are heterogeneous
• No consistent variation with longitude
• Slight variation in lavas collected from cinder cone 1,
suggesting crystallization during eruption
9
0.82
13
14
15
16
17
18
EuN
(Normalized to Sun and McDonough, 1989)
𝐸𝐸𝑢𝑢
=
∗
𝐸𝐸𝑢𝑢
𝐸𝐸𝑢𝑢𝑁𝑁
(𝑆𝑆𝑆𝑆𝑁𝑁 )(𝐺𝐺𝐺𝐺𝑁𝑁 )
Si 51%
H2O 1%
Si 52%
H2O 1%
QFM +1
QFM +2
P1
P2
P3
x
x
x
P1
P2
P3
H2O 2%
H2O 2%
Acknowledgements
0.83
1
-71.830
6
7
• Use Melts program (Ghiorso and
Sack, 1995) to model fractional
crystallization trends using a
range of parameters:
Thanks to Debbie Pierce for training on rock crushing. A sincere thanks
to Dr. Marion Lytle for all her help with ICP-MS prep, data collection,
and chemistry knowledge. Thank you Darin Schwartz and Dr. Dorsey
Wanless for collecting these samples and letting me analyze them.
Thanks to Boise State Geosciences Department for access to ICP-MS.
References
• Ghiorso M.S., Sack R.O. (1995). Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for
the interpretation and extrapolation of liquid–solid equilibria in magmatic systems at elevated temperatures and pressures. Contributions to
Mineralogy and Petrology, 119 (2/3), pp. 197–212
• Hickey-Vargas, R., Moreno-Roa, H., Lopez-Escobar, L., Frey, F.,1989. Geochemical variations in Andean basaltic and silicic lavas from the
Villarrica-Lanín volcanic chain (39.5 °S): an evaluation of source heterogeneity, fractional crystallization and crustal assimilation. Contributions to
Mineralogy and Petrology, 103, 361-386.
• Leach, R. A. (2012). A textural and chemical study of lavas from Villarrica and Llaima volcanoes, Chile: Evidence for magma recharge and
mixing (Masters thesis). Retrieved from GeoRef database.
• Palma, J. L., E. S. Calder, D. Basualto, S. Blake, and D. A. Rothery (2008), Correlations between SO2 flux, seismicity, and outgassing activity at
the open vent of Villarrica volcano, Chile, J. Geophys. Res., 113, B10201.
• Sun, S.S. McDonough, W.F., 1989, Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes, in
Sauders , A.D., and Norry, M.J., eds., Magmatism in the Ocean Basins: Geological Society of London Special Publication 42, p. 313-345.