Mineralogical (petrographic) and Chemical (petrologic) Analyses

Mineralogical (petrographic) and Chemical (petrologic) Analyses

Generalized petrographic summary of Mt. Erebus volcanic rocks
(from Kyle et al., 1992)
Rock Type Texture Ol Cpx Kaer Op Fsp Ap Fspth Gnd Ms
Basanite fp(10-25) p, x p   p p p g p, I
Ne hawaiite fp(1-20) or p(20-50) p, po r-p, po r, po, x? p p p r-g I, p or gl-h2c, 2o
Ne mugearite cp(20-30) p, po p, po   p p p g I, p, 2o
Ne benmoreite cp(20-50) p, po, x r-p   p p p g I, p or gl
Anorthoclase phonolite cp(30-60) p p   p p p r-g I, p orgl-h, c
Benmoreite mp(10-20) p, po, x r-p r-p, po p p-x r   t or gl, c
Phonolite mp(3-10) orp(10-15) r-p, x r-g r-ppo-co r-p p-x r g t or h-I, p
Trachyte mp(<5) g-x p   p p     t
Abbreviations:
Texture: p-porphyritic; mp-microporphyritic; fp-finely porphyritic; cp-coarsely porphyritic;
percentage of phenocrysts to nearest 5% is given in parenthesis.
Mineralogy: Ol-olivine; Cpx-clinopyroxene; Kaer-kaersutite; Op-opaque oxides; Fsp-feldspar; Ap-apatite; Fspth-feldspathoids;
p-present (>1%); r-rare (<1%); x-xenocrystic; po-partially oxidized; co-completely oxidized; g-groundmass only.
Groundmass: I-intersertal; p-pilotaxitic; gl-glassy; h-hyalophitic; c-cryptocrystalline; t-trachytic;
2c-secondary carbonate; 2o-secondary oxidation.

 

Chemistry of Mt. Erebus Volcanic Bombs

Table reproduced from: Caldwell, D.A., and Kyle, P.R., 1994, Mineralogy and geochemistry of ejecta erupted from Mount Erebus, Antarctica, between 1972 and 1986, in Kyle, P.R., ed., Volcanological and Environmental Studies of Mount Erebus, Antarctica, Volume 66: Washington, D.C., American Geophysical Union, p. 147-162.

Average Electron Microprobe Analyses of Matrix Glass Separated
From Bombs Erupted Between 1972 and 1987 From Mount Erebus.
Year
1972/73
1975/76
1977/78
1978/79
1979/80
1981/82
1982/83
1983/84
1984/85
1985/86
1986/87
# of anal.
(13)
(13)
(14)
(13)
(12)
(12)
(10)
(14)
(13)
(9)
(10)
SiO2
55.38
55.54
55.60
55.65
55.60
55.45
55.29
55.96
55.88
55.74
55.60
Al2O3
19.02
19.03
19.45
19.49
19.33
19.39
19.23
19.59
19.53
19.37
19.41
TiO2
1.03
1.02
1.04
1.06
1.09
1.00
1.06
1.04
1.01
1.07
1.05
FeO
5.37
5.47
5.37
5.30
5.51
5.41
5.46
5.35
5.26
5.28
5.42
MnO
0.19
0.17
0.19
0.22
0.24
0.19
0.20
0.21
0.19
0.37
0.30
MgO
0..82
0.80
0.81
0.81
0.83
0.81
0.81
0.83
0.84
0.79
0.84
CaO
1.90
1.93
1.84
1.96
1.91
1.91
1.90
1.86
1.85
1.98
1.81
Na2O
9.67
9.46
9.31
9.44
9.41
9.38
9.36
9.56
9.47
9.40
9.41
K2O
5.20
5.32
5.35
5.10
5.22
5.27
5.19
5.34
5.39
5.42
5.31
Total
98.58
98.74
98.96
99.03
99.20
98.81
98.50
99.74
99.42
99.42
99.15

 

 

Chemistry of Lava Flows

Table reproduced from: Kyle, P.R., Moore, J.A., and Thirlwall, M.F., 1992, Petrologic evolution of anorthoclase phonolite lavas at Mount Erebus, Ross Island, Antarctica: Journal of Petrology, v. 33, p. 849-875.

Select values from Represenative analyses of volcanic rocks from Mt. Erebus.

 
1
4
9
12
16
17
19
21
SiO2
43.32
44.89
50.17
55
56.57
54.28
58.91
63.51
TiO2
3.78
3.2
2.18
1.36
0.98
1.2
0.44
0.43
Al2O3
15.38
16.96
18.64
18.29
19.31
18.01
18.47
15.33
FeO*
12.08
11.23
8.04
6.59
4.95
8.46
5.89
6.15
MnO
0.22
0.23
0.22
0.27
0.23
0.29
0.26
0.21
MgO
6.77
4.21
2.51
1.64
0.99
1.57
0.37
0.14
CaO
10.66
9.28
5.73
3.34
2.75
4.4
2.19
1.44
Na2O
4.63
5.24
6.44
7.77
8.17
6.52
7.66
6.56
K2O
1.72
2.07
3.52
4.39
4.55
3.38
4.67
5.23
P2O5
1.21
1.69
1.1
0.56
0.42
0.51
0.13
0.05
LOI
0.03
-0.13
-0.01
-0.28
-0.21
0.01
0.03
0.18
Total
99.82
98.88
98.53
98.92
98.72
98.62
99.02
99.23

Major elements are given in wt. %.
1, Basanite (83435), Cape Barne; 4, Ne hawaiite (83432), Cape Barne; 9, Ne mugearite (83417), Tent Island; 12, anorthoclase phonolite (83452), Bomb Peak; 16, anorthoclase phonolite (80020), Three Sisters Cone; 17, benmoreite (83412), Inaccessible Island; 19, phonolite (83407), Inaccessible Island; 21, trachyte (82405), Bomb Peak.

LOI, loss on ignition.

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