Table 8. Microprobe analytical compositions of chromite inclusions in olivine.

[Oxide values are in weight percent]

Rock type
Sample

Dacitic pumice
Pt40

Mingled pumice

 

Andesite

 

Basalt

Pt41

Pt41

Pt42

Pt42

Pt53

Pt54

SiO2

0.12

0.23

0.34

 

0.10

0.09

 

0.47

0.16

TiO2

.97

1.10

1.01

 

.80

.85

 

1.17

.57

Al2O3

16.26

17.17

14.24

 

15.37

12.09

 

20.64

17.46

Fe2O3

15.17

13.99

16.69

 

11.84

18.13

 

25.26

9.23

Cr2O3

36.05

37.61

35.60

 

41.73

37.48

 

19.96

43.34

FeO

22.94

19.77

27.73

 

19.74

23.61

 

24.03

16.09

MgO

8.09

10.62

5.20

 

10.00

7.03

 

8.16

12.49

         Total

99.60

100.49

100.81

 

99.58

99.28

 

99.69

99.34

Cations on the basis of 3 cations and 4 oxygens

Si

.004

.007

.011

 

.003

.003

 

.015

.005

Ti

.024

.026

.025

 

.020

.022

 

.028

.014

Al

.631

.646

.562

 

.590

.483

 

.787

.654

Fe3+

.376

.336

.421

 

.290

.463

 

.615

.221

Cr

.938

.950

.943

 

1.074

1.005

 

.511

1.088

Fe2+

.631

.528

.777

 

.537

.669

 

.650

.427

Mg

.397

.506

.260

 

.485

.355

 

.394

.591

This page is <https://pubs.usgs.gov/pinatubo/bernard/table8.html>
Contact: Chris Newhall
Last updated 03.29.99