91 Chemical Analyses of Dacites

The Geology and Petrography of Crater Lake National Park, 1902

 PART II.

HYPERSTHENE-DACITES.

CHEMICAL ANALYSES OF DACITES.

The following analyses were made in the laboratory of the United States Geological Survey:

Analyses of Crater Lake dacites.
[Analyses by H. N. Stokes.]

—- 102. 113. 114. 130. 143. 151.
SiO 70.77 70.10 68.17 71.87 56.85 67.41
Al2O3 14.83 15.18 15.60 14.53 18.31 15.76
Fe2O3 1.35 1.78 2.31 1.28 2.88 1.88
FeO 1.25 1.09 .94 1.02 3.15 1.76
MgO .64 .74 1.02 .48 3.92 1.35
CaO 2.12 2.27 2.76 1.59 7.20 3.36
Na2O 5.07 5.15 5.15 5.08 3.89 4.54
K2O 2.68 2.58 2.46 2.84 1.23 2.36
H2O .07 .10 .09 .06 .16 .09
H2O+ .33 .19 .45 .22 .95 .54
TiO2 .38 .48 .54 .41 1.08 .56
ZrO2 .05 .04 None. .04    
CO2 None. None. None. None. None. None.
P2O5 .13 .13 .13 .10 .22 .12
SO3 None. None. None. None. None.  
Cl .11 .03 Trace. Trace.    
F Undet. Undet. Undet. Trace.    
S None. None. None. None. None. a.02
Cr2O3 None. None. None. None. None. None.
NiO None. None. None. None.    
MnO Trace. Trace. Trace. Trace. Trace. Trace.
BaO .08 .08 .06 .08 .04 .06
SrO
.02 .03 .03 .03 Trace. Trace.
Li2O Trace. Trace. Trace. Faint tr. None. Trace.
Total 99.88 99.97 99.71 99.63 99.88 99.81
aOr SO3 = .04. Whether present as S or SO3 undetermined.NOTE.—O=Cl.

No. 102. Hypersthene-dacite, vitrophyric type, south edge of Llao Rock flow. See page 106.

No. 113. Lithoidal hypersthene-dacite, water’s edge, head of Cleetwood Cove. See page 113.

No. 114. Streaked, vitrophyric hypersthene-dacite, near Wineglass, Grotto Cove, on the east side of the lake. See page 114.

No. 130. Hypersthene-dacite, lithoidal type, from a small dike that cuts the older flows immediately below Llao Rock.

No. 143. A dark-colored secretion found among the dacitic ejectamenta. See page 130.

No. 151. A light-colored secretion found among the dacitic ejectamenta. See page 139.

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