Geochemical Studies of Hawaiian Rocks — Naughton and Barnes 
289 
TABLE 2 
Composition of Primary Magmatic Gas 
COMPONENT 
VOLUME 
% at 1500° K 
h 2 o 
62.5 
h 2 
1.90 
co 2 
20.2 
CO 
1.66 
H 2 S 
0.38 
so 2 
13.2 
S 2 
0.42 
rium temperature of 1200°-1500°K is indi- 
cated for the actual gas. The value of the partial 
pressure of oxygen was found to be approxi- 
mately IQ" 8 atmospheres, in agreement with 
the value of 10~ 6 to 10" 8 atmospheres estimated 
independently from the study of basaltic rocks 
(Fudali et al., 1961). Measurement of the oxy- 
gen partial pressure is significant in that this 
quantity has been shown to influence crucially 
the course of magmatic differentiation (Osborn, 
1962), and may be the much-sought factor 
causing the derivation of different types of 
basalt from a tholeiitic parent magma. It will 
be noted that the magmatic environment found 
from these measurements is a reducing one. 
MEASUREMENT OF RADIOELEMENTS IN LAVA 
Hawaiian rocks have been used extensively 
in work on the very low uranium content of 
ultrabasic rocks and minerals, with the most 
recent researches on ultramafics and possible 
mantle materials being reported by Tilton and 
Reed (1963), and by Lovering and Morgan 
(1963). Also, a great deal of interest has cen- 
tered on lead isotopic anomalies observed in 
researches on Pb-Pb, U-Pb, and Th-Pb dating 
methods (Russell and Farquhar, I960). In ex- 
plaining these anomalies, discussion has in- 
volved the uncertainties regarding the cogenicity 
of lead and uranium, and the processes which 
might lead to separation of these elements dur- 
ing derivation from the mantle (Marshall, 
1958). Larson and Gottfried (I960) made 
some measurements on Hawaiian rock suites, 
and found uranium contents varying from 0.21 
to 1.8 ppm. They find an increase in uranium 
content in late basaltic differentiates (alkali 
basalts). In general, as pointed out by Heier 
and Rogers (1963), work on the uranium geo- 
chemistry of basaltic rocks has not been ex- 
tensive. 
At the Hawaii Institute of Geophysics work 
on the radioactivity of Hawaiian lavas is only 
in the preliminary stages of feasibility studies. 
Research with alpha-sensitive nuclear emulsions 
shows the uniform distribution of alpha activ- 
ity in the groundmass of tholeiites, and the 
higher concentration of activity in alkali suite 
members. A study of disequilibrium in the ura- 
nium decay chain is underway with a meas- 
urement of lead -210 through its alpha-active 
polonium -210 daughter. Easily measurable 
activities are found, and alpha spectrometry 
will be applied in the study. The radon content 
of volcanic gas is being measured also. 
Knowledge of the uranium, thorium, and 
potassium in Hawaiian lavas will enable esti- 
mates to be made of their contribution to the 
radioactive heat production, and an evaluation 
of a parent tholeiite magma as a reasonable 
direct derivative from the mantle which is in 
agreement with measurements of oceanic heat- 
flow. 
ACKNOWLEDGMENT 
Portions of this study were supported by the 
National Science Foundation under nsf Grants 
No. GP-140 and GP-2523. 
REFERENCES 
Eaton, J. P., and K. J. Murata. I960. How 
volcanoes grow. Science 132:925-938. 
Engel, A. E. J., and C. G. Engel. 1964. Igne- 
ous rocks of the East Pacific Rise. Science 
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Fudali, R. F., A. Muan, and E. F. Osborn. 
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Geol. Soc. Am. Abstracts for 1961. 
Heald, E. F., and J. J. Naughton. 1962. Cal- 
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systems by means of computers. Nature 193: 
642-644. 
and I. Lynus Barnes, Jr. 1963. 
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