Table 1. Major and trace element compositions of the 1991 Mount Pinatubo eruptive rocks.

[Oxide values in weight percent; elemental values in parts per million; n.a., not analyzed; LOI, loss on ignition]

Rock type
Sample
Location

Phenocryst-rich pumice

Average, Phenocryst rich

Pt6
Subic

Pt9a
Subic

Pt15 Poonbato

Pt16 Poonbato

Pt26
Clark

Pt31 Dizon

Pin1 Marella

Pin2 Marella

Pin3 Marella

Pin4 Marella

Pin5 Sacobia

Pin7 Marella

Pin8
Maraunot

Pin9 Marella

Pin10 Clark

SiO2

65.18

64.85

64.66

64.67

64.86

64.60

64.24

64.52

64.41

63.60

64.19

63.83

64.36

64.53

64.97

64.50

TiO2

.62

.54

.48

.49

.50

.49

.47

.50

.49

.47

.46

.48

.46

.47

.47

.49

Al2O3

15.35

15.54

16.94

16.89

17.01

16.66

15.75

15.40

15.63

15.92

16.10

15.64

15.83

15.71

15.58

16.00

FeO

5.00

4.63

4.21

4.19

4.44

4.16

4.15

4.18

4.26

4.07

3.87

4.07

3.80

4.13

3.97

4.21

MnO

.11

.11

.10

.10

.11

.09

.11

.11

.11

.10

.10

.10

.10

.10

.10

.10

MgO

2.55

2.43

2.16

2.23

2.36

2.15

2.60

2.37

2.52

2.54

2.52

2.81

2.44

2.60

2.53

2.45

CaO

4.92

4.83

5.29

5.32

5.54

5.22

5.30

5.16

5.18

5.38

5.24

5.46

5.08

4.68

5.12

5.18

Na2O

4.30

4.55

4.66

4.79

4.64

4.48

4.67

4.80

4.44

4.64

4.74

4.86

5.08

4.88

4.73

4.68

K2O

1.71

1.68

1.42

1.46

1.35

1.52

1.57

1.55

1.57

1.48

1.48

1.51

1.52

1.56

1.58

1.53

P2O5

.22

.20

.17

.18

.17

.15

.15

.15

.17

.14

.17

.16

.16

.15

.17

.17

LOI

n.a.

n.a.

n.a.

n.a.

n.a.

.44

.73

.57

1.02

.96

1.06

1.11

1.02

.43

.45

--

     Total

99.96

99.36

100.09

100.32

100.98

99.52

99.75

99.32

99.80

99.30

99.92

100.02

99.84

99.24

99.68

99.81

Rb

43

45

37

37

34

40

40

42

39

37

38

39

39

39

42

39

Sr

473

485

572

570

570

547

552

557

548

565

573

563

568

538

548

549

Ba

422

411

373

383

364

364

509

508

492

471

478

454

479

468

464

443

Nb

5

5

5

5

5

4

4

4

4

4

5

3

3

4

4

4

Zr

127

123

119

106

125

105

107

112

103

122

108

107

116

114

115

114

Y

14

12

11

11

12

13

12

12

13

14

12

13

12

12

11

12

Cr

21

140

129

19

22

27

40

34

26

27

27

35

24

31

27

42

Pb

10

9

10

7

8

13

11

13

7

10

11

11

8

11

10

10

Cu

4

5

0

3

0

56

37

16

17

27

29

23

29

49

27

21

Ni

15

13

11

12

13

17

15

12

12

15

16

18

15

16

16

14

Cl

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

473

476

523

438

480

420

467

525

501

--

V

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

77

78

69

81

73

79

72

86

83

--

S

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

1,615

1,474

1,911

2,161

1,628

2,211

1,637

421

353

--

Rock type
Sample
Location

Phenocryst-poor pumice

Average, phenocryst- poor

Banded pumice
Pt40
Maraunot

Mingled pumice
Pt41
Maraunot

Andesite

Basalt
Pt53

Ash

Pt9B
Subic

Pt32
Dizon

Pt48
Sacobia

Pt52
Maraunot

Pt50

Pt51

Pin 6
Marella

PIN12

PIN14

SiO2

65.39

65.19

63.88

64.65

64.78

64.67

60.15

60.36

59.76

59.73

50.60

61.13

62.82

TiO2

.50

.49

.52

.50

.50

.49

.60

.64

.62

.63

.90

.45

.41

Al2O3

17.07

16.69

16.56

16.36

16.67

16.43

16.29

15.96

15.89

15.23

13.92

16.23

16.38

FeO

4.28

4.22

4.43

4.13

4.27

4.20

5.51

6.10

5.83

5.88

9.04

3.97

3.45

MnO

.10

.10

.10

.10

.10

.10

.12

.12

.12

.15

.16

.11

.10

MgO

2.26

2.32

2.50

2.15

2.31

2.23

4.04

4.38

4.26

5.07

9.15

2.79

2.75

CaO

5.23

5.25

5.57

5.16

5.30

5.18

6.79

6.98

6.82

6.63

10.10

5.87

5.92

Na2O

5.09

4.71

4.36

4.45

4.65

4.49

4.01

3.84

3.86

3.99

2.78

5.26

5.10

K2O

1.56

1.52

1.55

1.43

1.52

1.48

1.56

1.59

1.52

1.33

1.41

1.38

1.44

P2O5

.18

.20

.17

.15

.18

.15

.21

.23

.22

.17

.30

.17

.17

LOI

n.a.

n.a.

1.15

.10

--

.59

.95

.18

.12

1.35

.23

1.22

1.10

     Total

101.66

100.69

99.64

99.08

100.27

100.01

99.28

100.20

98.94

100.17

98.59

98.58

99.64

Rb

37

39

39

40

39

40

44

47

47

34

48

43

37

Sr

542

543

544

536

541

543

568

558

566

490

531

617

605

Ba

362

381

347

357

362

362

349

360

377

418

317

429

368

Nb

5

5

3

4

4

4

3

4

3

4

3

4

3

Zr

118

111

105

109

111

112

108

109

109

87

104

111

113

Y

11

11

13

13

12

13

15

15

14

17

20

12

13

Cr

130

136

82

41

97

41

136

156

149

131

394

38

34

Pb

9

11

13

11

11

12

9

11

8

6

8

14

9

Cu

42

19

47

34

36

67

32

87

73

29

94

98

73

Ni

16

17

40

n.a.

24

40

17

47

56

56

131

20

19

Cl

n.a.

n.a

n.a.

n.a.

--

n.a.

n.a.

n.a.

n.a.

659

n.a.

1,540

1,022

V

n.a.

n.a.

n.a.

n.a.

--

n.a.

n.a.

n.a.

n.a.

126

n.a.

89

75

S

n.a.

n.a.

n.a.

n.a.

--

n.a.

n.a.

n.a.

n.a.

2,491

n.a.

2,827

2,633

This page is <https://pubs.usgs.gov/pinatubo/bernard/table1.html>
Contact: Chris Newhall
Last updated 03.29.99