Geochemical Studies of Hawaiian Rocks 
Related to the Study of the Upper Mantle 1 
John J. Naughton and L Lymus Barnes 
Certain 1 rocks, notably ultramafics (perido- 
tites) and eclogite, have properties which ful- 
fill a good many of the criteria for the material 
of the upper mantle. Hawaiian lavas have served 
as model substances in these categories (spe- 
cifically nodules from Hualalai, Hawaii, and 
eclogite from Salt Lake Crater, Oahu). In fact, 
Tilton and Reed (1963), on the basis of the 
factors contributing to radioactive heating, be- 
lieve that Hawaiian eclogites are the best guides 
to the composition of the upper mantle. Other 
investigators (Engel and Engel, 1964) are of 
the opinion that tholeiitic basalt, which is the 
predominant lava type of the Hawaiian Island 
chain and is unique in Its abundance at this 
site, is the chief or only magma generated in 
the earth’s mantle under oceanic ridges and 
rises. 
Geochemical investigations at the Hawaii 
Institute of Geophysics have contributed in 
several ways to the understanding of Hawaiian 
lavas as materials recently derived from the 
earth’s mantle. 
AGE-DATING 
Dating work has been directed mainly to in- 
vestigations of the suitability of whole rocks 
for age-dating using the Waianae volcanics of 
Oahu, and to solving the problems of dating 
relatively young rock. Some preliminary results 
are listed in Table 1, giving an idea of the age 
range expected in Hawaiian lavas and the capa- 
bilities of the potassium-argon method for dat- 
ing young rocks. 
The results are in good agreement with the 
whole rock determinations of McDougall (1964). 
The discrepancy between whole rock and in- 
cluded mineral ages is under investigation and 
must be resolved before proceeding with fur- 
ther studies. 
1 Hawaii Institute of Geophysics Contribution No. 
87 . 
Using the convective cell theory (Wilson, 
1963) and the distance from the present active 
source on Hawaii to the Waianae volcano, a 
crustal movement of about 10 cm/year has. 
been calculated by McDougall (1964). If the 
age of included mica from the Waianae lower 
member is used (8 million years), a rate of 
4 cm/year is found, which is in better agree- 
ment with the 3 cm/year calculated as the 
upper limit for convective currents in the 
upper mantle (McDougall, 1964). The alter- 
nate interpretation of these data of course is 
that the age relations reflect progressive devel- 
opment of volcanism along gradually develop- 
ing fractures in the crustal mantle, rather than 
crustal migration from a single primary source 
of volcanism. 
ANALYSES FOR MAJOR AND MINOR ELEMENTS 
A controversy has been under way for many 
years as to the possible source within the upper 
mantle of the two main types of oceanic lavas 
(tholeiitic and alkalic). One school maintains 
that they have two completely separate magma 
sources (Kuno, 1959), the other that both 
have been derived from a single parent magma 
by gravitational differentiation or by separa- 
tion at a different stage of lava ascent (Engel 
and Engel, 1964). Seismic evidence in Hawaii 
indicates that the primary events which culmi- 
nate in eruption at active volcanoes take place 
within the upper mantle at a depth of about 60 
km, and that build-up and storage of lava occur 
in a magma chamber about 3 km immediately 
beneath the volcano (Eaton and Murata, I960).. 
Thus, the active sequences in Hawaii are rela- 
tively clear, and chemical and petrological stud- 
ies on Hawaiian lavas have figured most prom- 
inently in the discussions of the theories of 
basalt derivation. 
Chemical analyses of some hundreds of sam- 
ples are available for Hawaiian lavas, with many 
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