Geochemical Journal, Vol. 1, pp. 157 to 168, 1967.

Pele's hair as a liquid of Hawaiian tholeiitic basalts

TAKASHI KATSURA

Department of Chemistry, Tokyo 'institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan

(Received October 19, 1966; i n revised form September 16, 1967)

Abstract-The chemical composition of Pele's hair seems to be important for illus trating the variations in chemical compositions of the Hawaiian tholeiitic basalts including the iron-rich members. The tholeiites in Hawaii are divided into two groups: One includes a series of rocks whose compositions can be explained by mixing of the magma of Pele's hair and olivine, and the other includes those whose compositions can be explained by subtracting plagioclase and clinopyroxene from the magma of Pele's hair. By using the value of the mole ratio FeO/FeOi.s in the Pele's hair, the liquidus temperature of the magma of Pele's hair is estimated to be 1,160°±10°C at an oxygen partial pressure of 10-8.2 atm.

INTRODUCTION Pele's hair is the only available material that represents supercooled liquid of a Hawaiian basalt magma. Comparing the composition of the Pele's hair with those of the solidified basaltic rocks in Hawaii, we may find that the composition of the Pele's hair is similar to that of the non-porphyritic basalt described by MACDONALD (1949), which, however, contains plagioclase, pyroxene, and iron ores as major minerals in the groundmass. The present study is intended to demonstrate the significance of the composition of the Pele's hair, and to reproduce experimentally the state of the Pele's hair in order to determine the temperature and the oxygen partial pressure of the magma of Pele's hair. The temperature and oxygen partial pressure obtained experimentally are consistent with the results obtained by field and microscopic observations.

SAMPLES COLLECTED FROM THE SUITE OF THOLEIITIC BASALTS Recent study by MACDONALDand KATSURA (1964) has made clear that the early lavas of all the Hawaiian volcanoes are indeed tholeiitic. Most abundant are tholeiites slightly supersaturated to slightly undersaturated with silica, containing small to moderate amounts of phenocrysts of olivine, which were in process of resorption when the rocks solidified. The locality and the numbers of samples of the tholeiitic basalts treated in the present study are as follows

157 158 T. KATSURA

Waianae Range 38 Lower Member West Maui 19 Wailuku volcanic series Haleakala 4 Honomanu volcanic series Kohala 14 Pololu volcanic series Mauna Kea 1 Upper Hamakua volcanic series Kauai 11 Olokele volcanic series Mauna Loa 7 Historic lavas 1 Kapoho (Puna), 1960 Kilauea 2 Puna, 1955

Chemical compositions of these rocks have been published by MACDONALD and KATSURA (1964). The tholeiitic basalts interstratified with alkalic rocks are omitted in the present study in order to avoid confusion. All the samples treated in the present study are, therefore, of the younger stage (STEARNS, 1940). Thus the "tholeiitic basalts" used herein involve basalt, olivine basalt, and picrite basalt of the oceanite type defined by MACDONALD(1949 b). Some previously published data on the chemical compositions of the lavas of Mauna Loa and Kilauea are also used in the present study. The locality and numbers of the rocks are listed below along with the references:

Mauna Loa 4 (MACDONALDand EATON, 1955) 2 (SHEPHERD, 1938) 1 (WASHINGTON, 1923 a) Kilauea (Puna) 9 (MACDONALD, 1955) (caldera) 1 (WASHINGTON, 1923 b) (caldera) 3 (MACDONALDand EATON, 1955) (Iki) 2 (TILLEY, 1960 b) (prehistoric) 1 (YODER and TILLEY, 1957) (Iki) 11 (MACDONALDand KATSURA, 1961) (prehistoric) 2 (KUNo et al., 1957) (1840 lava) 2 (MACDONALD, 1949 a) 4 (TILLEY, 1960 a)

CHEMICAL COMPOSITION OF PELE'S HAIR AND ITS RELATION TO THE HAWAIIAN THOLEIITES Three analyses have been reported so far on the Pele's hair and their com positions are listed in Table 1. The average composition of the Pele's hair is cal culated from these three (No. 4 in Table 1). The average composition of the Kilauean tholeiites including olivine tholeiites, and the average of basalts with less than 5 of olivine phenocryst are also given in Table 1 as Nos . 5 and 6, respectively. These average compositions resemble one another . It is noted that Pele's hair as a liquid of Hawaiian tholeiitic basalts 159

Table 1. Chemical compositions of Pele's hair and related tholeiites

1 2 3 4 5 6 7

Si02 48.82 50.26 50.04 49.72 49.99 50.79 50.37 Ti02 2.77 2.69 3.02 2.83 2.86 3.08 3.09 A1203 13.42 13.48 14.02 13.65 13.26 14.10 14.02 Fe203 1.70 1.55 1.72 1.66 1.88 3.17 1.88 FeO 9.90 9.57 9.45 9.64 9.76 8.33 10.07 MnO 0.18 0.17 0.17 0.17 0.16 0.12 0.17 MgO 9.00 7.04 6.93 7.66 8.39 6.78 6.75 CaO 11.32 11.45 11.54 11.44 10.61 10.26 10.39 Na20 2.25 2.22 2.42 2.30 2.26 2.60 2.35 K20 0.58 0.45 0.57 0.53 0.54 0.48 0.62 0.02 0.16 H2O 0.03 0.10 H20+ 0.02 0.27 0.15 0.32 P205 0.24 0.26 0.26 0.25 0.30 0.29 0.32 remainder 0.52

Total 100.22 99.96 100.24 100.00 100.00 100.00 100.23

1. Pele's hair, ejected during the early stages of the 1959 eruption of Kilauea Iki, collected by Dr. H. IKAWA, University of Hawaii, Nov. 22, 1959 (MACDONALD and KATSURA, 1961). 2. Pele's hair, collected in 1920, 2.5 miles southwest of Halemaumau, Kilauea crater (H. S. WASHINGTON, 1923). Reanalyzed by C. 0. INGAMELLS (TILLEY et al., 1965). 3. Pele's hair, collected in 1921, desert near the 1919 rift crater, southwest of Halemaumau, collected by T. A. JAGGAR (TILLEY, 1960). Analyst: J. H. SCOON. 4. Average of 1, 2, and 3. 5. Average of tholeiitic basalts from Kilauea (51 samples). (MACDONALD and KATSURA, 1964). 6. Average of Hawaiian basalts defined by MACDONALD (1949). 7. C-132, tholeiite, reported by MACDONALD and KATSURA (1964). This sample was used for the experiment in the present study.

No. 4 contains only 2.5% normative olivine, and Nos. 5 and 6 contain 0.5 and 4 normative quartz, respectively. For illustrating the chemical variations of all Hawiian tholeiitic basalts, Fig. 1 is constructed by the reason mentioned in a previous paper (MACDONALD and KATSURA, 1964). The ordinate means the total amount of FeO+MgO which in cludes Fe203 converted to FeO, and the abscissa, FeO/MgO is probably related closely to the temperature and the oxygen partial pressure of magmas during the fractional crystallization. The chemical compositions of the lavas extruded in Kilauea Iki in 1959 have been interpreted as a series of mixtures of olivine and Pele's hair No. 1 in Table 1 (MACDONALDand KATSURA, 1961), the latter substantially representing the liquid part (or groundmass after solidification) of the lava. A point Pa is the average composition of the Pele's hair listed in Table 1, and 01 is of the olivine in the 160 T. KATSURA

70 01 1 0 CD

Pt 0 30 l~ Py 0 Obs 20 1 PaB C4 C5 0A,x ..0 , P2 A

0.2 0.5 2 3 4 Fe0/,MgO Fig. 1. Relationship between FeO+MgO (wt°o) and FeO/MgO (wt) in rocks of Mauna Loa and Kilauea. 01: Olivine in the picrite-basalt of the 1959 Kilauea eruption (MACDONALD and KATSURA, 1961) Pi : Pele's hair of the 1959 Kilauea eruption (MACDONALD and KATSURA, 1961). P2: Pele's hair of the 1921 Kilauea eruption (TILLEY, 1960). Pa: Average of three Pele's hairs in Table 1. Py: Phenocrystic clinopyroxene (MUIR and TILLEY, 1957). A: The least magnesia-enriched lava of Puna, Kilauea (TILLEY, 1960). Pc: Average composition of the picrite basalts of oceanite type in Hawaii (MAC DONALD, 1949). Ob: Average composition of the olivine basalts in Hawaii (MACDONALD, 1949). B: Average composition of the basalts in Hawaii (MACDONALD, 1949). C4: Calculated value of No. 4 in Table 2. Cs: Calculated value of No. 5 in Table 2. Open circles: The lavas of the 1959 Kilauea Iki eruption (MACDONALD and KATSURA, 1961). Solid circles: Lavas of Kilauea and Mauna Loa.

1959 lava of Kilauea Iki (MACDONALDand KATSURA, 1961). The open circles are of the specimens from the 1959 eruption, and a curved line, 01-Pa, represents a com positional variation resulted from the arbitral mixing of olivine, 01, and the liquid, Pa (the logarithmic expression is used only for convenience, and the relationship between FeO+MgO and FeO/MgO is not linear, because the abscissa represents the ratio). As shown in Fig. 1, the actual relation found in rocks of Kilauea Iki fits the line 01-Pa, and taking account of the fact that no phenocrysts other than olivine are present in any of the samples from the Iki eruption, it may be said Pele's hair as a liquid of Hawaiian tholeiitic basalts 161

that all the specimens of that eruption belong to the tholeiitic basalt group con trolled only by olivine phenocrysts, as suggested by POWERS (1955). The contents of the other components such as Si02, A1203, CaO, Na20, K20, Ti02 and P205 in the hypothetical mixtures of Pele's hair and olivine are also similar to those of the actual specimens as shown partly in a previous paper (MACDONALDand KATSURA, 1961). The same relation is also found in the average picrite basalt, olivine basalt, and basalt described by MACDONALD(1949) (Fig. 1). The compositional line of the iron-rich members of Kilauean tholeiites ends around the point Pa to start another line, as can be seen in Fig. 1. Thus the relationship between FeO+MgO and FeO/MgO is divided into two parts, one re presented by the line 01-Pa, and the other by Pa-A, where A is a specimen of the 1955 Puna eruption, Kilauea (No. 82 in Table 4, p. 53 of the paper by TILLEY, 1960 a). This specimen A is the least magnesia-enriched lava, though there is an exceptional case found by KUNG et al. (1957), in which iron is abnormally enriched (total iron, 16.12y,, FeO+MgO, 19.06, and FeO/MgO, 5.61). The chemical properties of the Hawaiian volcanic rocks seem to change abruptly at the point A, as shown in Fig. 2. The line Pa-A in Fig. 1 strongly suggests the removal of pyroxene, because the point representing the composition of clinopyroxene in Hawaiian basalts is situated near the extension of the line Pa-A. The chemical composition of pheno cryst clinopyroxene cited in Table 2 is the average of the values obtained by MUIR and TILLEY (1957). If we subtract 10 and 20Y. of the clinopyroxene from the liquid Pa, we get the composition of Nos. 2 and 3 in Table 2, respectively. In these cases the A1203 content is significantly increased to more than 15 whereas the A1203 content of the rocks of the 1955 Puna eruption ranges from 13.5 to 14Y, . Thus, it

Table 2. Composition of materials obtained by calculation, assuming various amounts of pyroxene and plagioclase subtracted from Pele's hair, Pa

1 2 3 4 5

°o of pyx . subtracted 0 10 20 15 22 from Pele's hair of p1. subtracted 5 0 0 .5 10 from Pele's hair (Ab3o ) (Ab2o) (Ab20 ) Si02 49.7 49.6 49.2 49.5 49.4 Ti02 3.1 3.0 3.3 3.4 3.9 A120a 12.8 14.8 16.3 14.3 14.1 Fe203 1.8 1.8 1.8 1.9 2.2 FeO 10.0 10.0 10.6 10.9 12.2 MnO 0.2 0.2 0.2 0.2 0.2 MgO 8.1 6.7 5.3 6.3 5.6 CaO 11.3 10.5 9.5 9.8 8.4 Na20 2.2 2.5 2.8 2.7 2.9 K20 0.5 0.6 0.6 0.6 0.7 P205 0.3 0.3 0.4 0.4 0.4

162 T. KATSURA

0 0I 50 TI,

To .

• • .. O • LL 0* R 20 oil

x x x

-+ H 5 I0 0.3 0.5 Fe O/MgO - 2 -,W xM

A 5 A

Fig. 2. Relationship between FeO+MgO (wt%) and FeO/MgO (wt) in Hawaiian tholeiitic bassalts with additional values for hawaiite (cross), mugearite (M), and trachyte (triangle). is necessary to introduce another kind of subtraction involving both plagioclase and pyroxene. Some results of the computation are shown in Table 2. A rock specimen of the Puna lavas represented by A in Fig. 1 corresponds to the calcu lated composition No. 5 in Table 2, and a rock specimen No. 78 of the Puna lavas (TILLEY, 1960 a, Table 4, p. 53) corresponds to No. 4 in Table 2. Significant differences between the analyzed and calculated values are seen in Si02 and FeO contents in the case of Puna A. In the present method of calculation, however, the silica contents of the Pele's hair and of clinopyroxene closely resemble each other, and, therefore, the difference in absolute silica content may not be used to explain the differentiation course of a small group of basalts. The relation ship between FeO+MgO and FeO/MgO based on the calculation is also plotted in Fig. 1. These points are nicely arranged on the line Pa-A. As a matter of fact, Fig. 2 shows that almost all the Hawaiian tholeiitic basalts containing very few olivine phenocrysts are situated on or near the line Pa-A.

EXPERIMENTALSTUDY TO REPRODUCETHE STATE OF THE PELE'S HAIR For obtaining a supercooled liquid represented by the Pele's hair, it is necessary to control not only the temperature but also the oxygen partial pressure. Recently OSBORN (1959) and his colleagues have made clear the role of the oxygen partial Pele's hair as a liquid of Hawaiian tholeiitic basalts 163

pressure in the fractional crystallization of magmas, and KATSURA and SHIBATA (1967) illustrated how the liquidus temperature of the tholeiitic basalts is affected by both the oxygen partial pressure and temperature. The experimental techniques to establish the Po,-T diagram are the same as those by MUAN (1955), KATSURA and MUAN (1964), FUDALI (1965), PRESNALL (1966), and SHIBATA (1967). A 40% Rh 60% Pt container was used for minimizing the loss of iron in sample, and the change in FeO content of samples was negligible as previously shown by SHIBATA (1967) in the case of Mihara lava. Alkali contents, Na20 and K20, were not changed after 8 hr heating at 1,400°C. The precision for measurement of temperature was within ±2°C, and Po, values were calibrated with a stabilized zirconia cell as previously described by KATSURA and HASEGAWA(1967), and SHIBATA (1967). The liquidus temperatures at various oxygen partial pressures were determined from both sides of reaction involving the crystallization from liquid and the melting of the crystal. The heating time varied from 8 to 120 hr depending on the temperature. The errors of the equilibrium temperatures for the crystallization at various Po, were within ±5°C throughout the present study. The phases after the runs were identified by a petrographic microscope. As can be seen in Table 1, the FeO/Fe203 ratio in the Pele's hair is nearly constant for three samples, 5.81 on an average (log 1ONFeo/NFeol.,=0.810).Thus, if we use the Po,-T diagram for the composition of the Pele's hair, we can determine the temperature and the oxygen partial pressure at which the Pele's hair may be produced. Unfortunately, the amount of the Pele's sample availabe to the present study was too small to establish the Po,-T diagram, and in the present study, there

1100 1200 1300 ° C Fig. 3. Po,-T diagram for equilibrium crystallization of the sample C-132. G: glass SP Sp: spinel group mineral, hematite crystallizes sp + SP at high Po, instead of Sp. 2 P( G G P1: plagioclase. Py: clinopyroxene (with Ti02 ). Py Open circles: measured values of Po, at various E G temperatures on the basis of Table 3. 04 Solid circle: Liquidus temperature of the Pele's magma. v a G (The data for the diagram are as follows; rn 0 in air; SP 1,270°C '6 P1 1,200°C Py 1,175°C pt+G .0 in COz; Sp 1,205°C PI PI 1,165°C PY Py 1,155°C 8 o-'' ti~ NFeG in C02,/H2=100; Sp disappeared G \SO

+ 164 T. KATSURA fore, the result of the tholeiite, C-132 (MACDONALDand KATSURA, 1964) which is close to the Pele's hair in chemical composition is used instead of the Pele's hair. The chemical composition of C-132 is given in Table 1, and the Pot-T diagram for C-132 is given in Fig. 3. For determining the ranges of both temperature and Pot of the Pele's hair, it is only needed to obtain the relationship between the FeO/Fe203 ratio and the tem perature of the liquid of C-132 at various oxygen partical pressures. As has been found by FUDALI(1965) and SHIBATA(1967), the chemical equilibrium between ferrous and ferric oxides in molten rocks should be written as follows; FeO+ 1/4 02 =Fe01.5, where the melt has been assumed to be the ideal solution in regard to FeO and Fe203. For the present purpose, the Fe0/FeOi.5 mole ratio was determined at temperatures of 1,300, 1,200, and 1,170°C under limiting oxygen partial pressures within the liquid region of Fig. 3. The results obtained are given in Table 3, and illustrated in Fig. 4. As expected from the chemical equilibrium written above, the slope between log (NFeo/NFeo,.5)and log Pot at temperatures 1,300, 1,200, and 1,170°C is nearly 1/4, indicating the ideality of the melt, as assumed above. Thus, we may obtain the iso-ratio line of the FeO/Fe01.5 as in Fig. 3. This line seems to be straight within the experimental error, and we get the values of both temperature and oxygen partial pressure at which plagioclase begins to crystallize as a primary phase. Indeed, the CaO content of C-132 is slightly different from that of the average of the Pele's hair, and the crystallization line for plagioclase is supposed Table3. Equilibriummole-ratio of FeO/FeOi.s / at various oxygen partial pressures (The value of logio(NFeo/Nfeo,.s) in the 1 average Pele's hair is 0.810) ,0

Temperature -logioPo2 l Pete's hair oC at m og io(NFeo/NFeo,., ) 0 1,300 0.68 -0 .602 3.50 0.041 Z 0.5 5.70 0.643 0 7.50 1.061 L 1,200 3.85 -0.149 6.95 0.643 Z 0 8.00 0.919 1,170 7.40 0.663 0

Fig. 4. Relationship between logio(NFeo/ NFeo,.,) and logioPo2 in the liquid region of _j the sample C-132. -0 .5 Q -: 1,300°C 3 4 5 6 7 8 p -: 1,200°C -log Pot -A-: 1,170°C . Pele's hair as a liquid of Hawaiian tholeiitic basalts 165 to shift slightly to a higher temperature. However, as already shown by KATSURA and SHIBATA (1967), this difference for typical tholeiite composition may be small (± 10°C ). Thus, we can estimate the temperature and the Pot at which plagioclase begins to crystallize from the magma of Pele's hair to be 1,160'-+10'C and 10-8.2 atm (±0.1 in the exponent) respectively.

COMPARISONS WITH THE PREVIOUS STUDIES Based on field and microscopic observations of Hawaiian olivine basalts, MACDONALD (1949b) concluded that the earliest phenocryst to form is olivine. Plagioclase is the second to crystallize. The period of hypersthene crystallization is less definite, and as pointed out by BARTH (1931), in many olivine basalts there is no evidence for hypersthene to have formed at any stage. Powers (1955) sum marized the chemical composition of Kilauean lava flows from the relationship be tween magnesia and silica. He concluded that the historic lavas of Kilauea could all have been derived by movement of olivine phenocrysts into or out of a "single liquid magma". His conclusion has been supported by MACDONALD (1949b), MACDONALDand KATSURA (1961), and MURATA and RICHTER (1966). On the other hand, MUIR and TILLEY (1957) have studied the picrite basalts of Kilauea volcano, and concluded that it is unlikely that olivine is the only mineral that was extracted from the original liquid of the 1840 picrite basalt, since the rocks also contain phenocrysts of pyroxene and plagioclase, and they thought that the crystallization of olivine from the Kilauean basaltic liquid is followed closely in time by that of pyroxene and plagioclase. The problem is then in the definition of basaltic liquid from which three major rock-forming minerals crystallize. Since the composition of Hawaiian olivine-bearing tholeiites is reasonably inter preted as mixtures of Pele's hair, Pa, and the pure olivine, 01, as shown in Fig. 1, the "single liquid magma" proposed by POWERS(1955) may be taken as what is close in composition to the magma of Pele's hair. As may be expected from the high melting temperature of olivine, the liquidus temperature of a mixture of Pa and 01 may increase with increasing proportion of 01, and YODERand TILLEY(1957, 1962), TILLEYet al. (1963, 1964, 1965, 1967) have made clear the trend of the liquidus temperatures of various Hawaiian tholeiites under unknown Pot. Thus, if the tem perature of the magma of Pele's hair increases, the composition of resulted liquid may change to higher MgO or olivine content, because the magma of Pele's hair usually coexists with olivine crystals in a Kilauean magma chamber, and we may obtain a more basic magma from which olivine crystallizes as a primary phase, and subsequently plagioclase and pyroxene may crystallize at lower temperatures, as pointed out by MUIR and TILLEY (1967). Thus, it may be said that the temper ature of the magma of Pele's heir is critical for the crystallization course trending toward the iron-rich members of Hawaiian tholeiites. WAGER(1960, 1965) empirically pointed out a possibility that a small interval of temperature during the fractional 166 T. KATSURA

crystallization, say about 20°C, is highly significant in relation to the fractionation stage of basalt magmas. The most fundamental data on the temperature of the Kilauea Iki eruption were reported by EATON and MURATA (1960), and RICHTER and MURATA (1966). On the basis of these measurements, MURATA and RICHTER (1966) made a conclusion that the temperature of the Kilauea Iki lava generally varied with the olivine content. Though we cannot determine the composition of liquid coexisting with olivine at various temperatures, it seems highly significant to note that an average temper ature, 1,160°C, measured by them agrees well with the liquidus of the magma of Pele's hair at 10-$-2 atm of Po,. As can be seen in Fig. 3, however, the liquidus temperature of the magma of Pele's hair is affected by the change in Pot, especially in the high Po, region. HEALD et al. (1963) determined the oxygen partial pressure of the volcanic gases from a Kilauea Iki eruption to be 10-$ atm at 1,500°K and 1 atm, on the basis of the equilibrium calculations for various gas species. The temperature, 1,500°K, is a little higher than the actual temperature, but the value of 10-$ atm Pot is in good agreement with the present result obtained from the value of NFeo/NFeo1., in the Pele's hair. FUDALI (1965) and SHIBATA(1967) also focussed their attentions to the FeO/FeO,.5 ratio in molten rocks and estimated the oxygen partial pressure of typical tholeiitic magmas to be around 10-$ atm at about 1,200°C.

CONCLUSIONS From the considerations on the chemical composition of Pele's hair and, tholeiitic basalts in Hawaii and the experimental data described in this paper, it can be con cluded that, (1) the Pele's hair, Pa, represents a critical composition; olivine-bear ing tholeiites are interpreted as mixtures of olivine and a liquid represented by Pele's hair, and the iron-rich members of the Hawaiian tholeiite series may be derived from the magma of Pele's hair by removing both plagioclase and clino pyroxene while decreasing the temperature when the Pot is maintained low enough to prevent the separation of spinel group minerals, (2) the NFao/NFeo,., ratio in the Pele's hair strongly suggests that the value of Po, of the magma of Pele's hair is 10-$-2 atm at 1,160°C, and this value is in good agreement with those obtained by other investigators.

ACKNOWLEDGEMENTS A part of this work was carried out under National Science Foundation Research Grant, G-11319, to Professor G. A. MACDONALD,University of Hawaii, for geochemical investigations of Hawaiian lavas. The author wishes to express his sincere thanks to Dr. G. A. MACDONALD,.who also kindly read the manuscript, and to Mr. C. O. INGAMELLS,of the Pennsylvania State University, who kindly analyzed a rock speci men to check the results of the present chemical analyses. The author also expresses Pele's hair as a liquid of Hawaiian tholeiitic basalts 167

his thanks to Dr. KENJI SHIBATA who analyzed some of the ferrous iron content of samples, and to Dr. IKuo KusHIRO, who examined the crystallizing minerals from the melted samples by microscope.

REFERENCES

BARTH, T. F. W. (1931) Mineralogical petrography of Pacific lavas. Am. J. Si., Ser. 5, xxi, 491-530. EATON, J. P. and MURATA, K. J. (1960) How volcanoes grow. Science 132, 925-938. FUDALI, R. F. (1965) Oxygen fugacities of basaltic and andesitic magmas. Geochim. Cosmo chim. Acta 29,.1063-1075. HEALD, E. M., NAUGHTON, J. J., and BARNES, L. JR. (1963) The chemistry of volcanic gasses. 2. Use of equilibrium calculations in the interpretation of volcanic gas samples. J. Geophys. Res. 68, 545-557. KATSURA, T. and HASEGAWA, M. (1967) Equilibria in the V203-VO2 system at 1,600°K. Bull. Chem. Soc. Japan 40, 561-569. KATSURA, T. and MUAN, A. (1964) Experimental study of equilibria in the system FeO-Fe2Os Cr203 at 1,300°C. Trans. AIME 230, 77-84. KATSURA, T. and SHIBATA, K. (1967) The effect of oxygen partial pressure during the course of crystallization from basalt magmas (2). Read at the 11th Pacific Science Congress in Tokyo, August 1966. KUNO, H., YAMASAKi, K., IIDA, C., and NAGASHIMA, K. (1957) Differentiation of Hawaiian magma. J. Geol. Geogr. Japan 28, 179-218. MACDONALD, G. A. (1949a) Hawaiian petrographic province. Bull. Geol. Soc. Am. 60, 1541 1596. MACDONALD, G. A. (1949 b) Petrography of the island of Hawaii. U. S. Geol. Survey, Prof. Paper 214-D. 51-96. MACDONALD. G. A. and EATON, J. P. (1955) Hawaiian volcanoes during 1953. Geol. Survey Bull. U.S.A. 1021-D, 127-166. MACDONALD, G. A. and KATSURA, T. (1961) Variations in the lava of the 1959 eruption in Kilauea Iki. Pacific Science 15, 358-369. MACDONALD, G. A. and KATSURA, T. (1964) Chemical composition of Hawaiian lavas. J. Petrol. 5, 82-133. MUAN, A. (1955) Phase equilibria in the system FeO-Fe2Oa Si02. Trans. AIME 203, 965-976. MUIR, I. D. and TILLEY, C. E. (1957) Contributions to the petrology of Hawaiian basalts. 1. The picrite-basalts of Kilauea. Am. J. Sci. 255, 241-253. MURATA, K. J. and RICHTER, D. H. (1966) The settling of olivine in Kilauean magma as shown by lavas of the 1959 eruption. Am. J. Sci. 264, 194-203. OSBORN, E. F. (1959) Role of oxygen pressure in the crystallization and differentiation of basaltic magma. Am. J. Sci. 257, 609-647. The other references by OSBORN and his colleagues are listed in a paper by SHIBATA (1967). POWERS, H. A. (1955) Composition and origin of basaltic magma of the Hawaiian islands. Geochim. Cosmochim. Acta 5, 77-107. PRESNALL, D. C. (1966) The join forsterite-diopside-iron oxide and its bearing on the crystalli zation of basaltic and ultramafic magmas. Am. J. Sci. 264, 753-809. RICHTER, D. H. and MURATA, K. J. (1966) Petrography of the lavas in the 1959-60 eruption of Kilauea volcano, Hawaii. U. S. Geol. Survey, Prof. Paper 537-D. SHEPHERD, E. S. (1938) The gases in rocks and some related problems. Am. J. Sci. 5th Ser. 35-A, 311-351. SHIBATA, K. (1967) The oxygen partial pressure of the magma from Mihara volcano, O-sima, Japan. Bull. Chem. Soc. Japan 40, 830-834. 168 T. KATSURA

STEARNS, H. T. (1940) Four-phase volcanism in Hawaii. Geol. Soc. Am. Bull. 51, 1947-1948. TILLEY, C. E. (1960 a) Differentiation of Hawaiian basalts: Some variants in lava suites of dated Kilauean eruption. J. Petrol. 1, 47-55. TILLEY, C. E. (1960b) Kilauea magma 1959-1960. Geol. Mag. 97, 494-497. TILLEY, C. E., YODER, H. S. JR. and SCHAIRER, J. F. (1963) Melting relations of basalts. Carnegie Institution, Year Book 62, 77-84: (1964) New relations on melting of basalts. ibid. 63, 92-97: (1965) Phase-equilibrium studies of silicate and oxide systems. ibid. 64, 69 82: (1967) Melting relations of volcanic rock series. ibid. 65, 260-269. WAGER, L. R. (1960) The relationship between the fractionation stage of basalt magma and the temperature of the beginning of its crystallization. Geochim. Cosmochim. Acta 20, 158-160. WAGER, L. R. (1965) A chemical definition of fractionation stages as a basis for composition of Hawaiian, Hebridian, and other basic lavas. ibid. 9, 217-248. WASHINGTON, H. S. (1923a) Petrology of the Hawaiian Islands. II. Hualalai and Mauna Loa. Am. J. Sci. 5th Ser. 6, 100-126. WASHINGTON, H. S. (1923 b) Petrology of the Hawaiian Islands: III. Kilauea and general petrology of Hawaii. ibid. 6, 338-367. YODER, H. S. and TILLEY, C. E. (1957) Basalt magmas. Carnegie Institution, Year Book 56, 156-161. YODER, H. S. and TILLEY, C. E. (1962) Origin of basalt magmas: An experimental study of natural and synthetic rock systems. 1. Petrol. 3, 342-532.