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Solubility of sulfur in some magmas at 1 atmosphere
aeochhnfoa etComochfmica Acta, 1974, VOI. 38.pp.617to631.Pmamon Press. WntedinNorthern IrAnd
Solubility of sulfur in some magmas at 1 atmosphere Tmsnr
KATSURA
and Srrmxnu HAGASHIMA
Department of Chemistry, Faculty of Science, Tokyo Institute of Technology, Ookayama, Yeguro-ku, Tokyo (Received24 May 1973; accepted in revised form 27 September 1973)
Abstract-h
order to understand the distribution of sulfur in igneous rooks, we determinedthe solub~ity of sulfur in volcanic rock melts (tholeiitebasalt, hawaiite and rhyoda&te from Hawaii) at vmriousgas compositions and at 1250° and 1300% and 1 atm total pressure. The solubility of sulfur in the melt passes through a minhmnn with change in oxygen partial pressure,if other factors are held constant. For the basaltic liquid at 1200°C, most sulfurin the melt is as dissolved suhlde (S-e) at oxygen partial pressures below 10--8 atm and as dissolved sulfate at oxygen partial pressuresabove 10-e atm. Based on the present solubility data, 6 per cent is inferredfor voiaanie gas at 1 atm total pressurein equilibriumwith subaeriallyextruded Hawaiian tholeiite basalt (Pele’s hair with 180 ppm S) at 1200% and lOa atm Po,.
THE smm content in igneous rocks has been studied by several investigators to obtain the average amount of sulfur in the crust. These are painstaking studies, but are insufficient to clarify the general rules covering the global ~t~bntion~f sulfur in igneous rocks. Because sulfur is one of the volatile constituent in a magma, we cannot apply the distribution law based on the crystallo-chemical properties recognized in metallic minor elements to the distribution of sulfur. Recently, several investigators focused their attentions on the solubility of gaseous species in magmas in order to clarify original contents of some volatile constituents in magmas at high tem~rat~s and pressures. The solubility of sulfnr in rather simple silicate melts was studied experimentally by FINcw and RICHARDSON(X954), ST. PIERRE and CHIPMAN (1956), ~OQAK and DARKEN (1961), MACLEAN (1969), Su and CLARK (1973), and NAGAsm and KATSURA (1973). Pmcm and RICHARDSON (1954) studied the solubility of sulfur in the CaO-A&O,-SiO, system at high temperatures. They obtained a ~mum value in the solub~ty of sulfur as a function of the oxygen partial pressure at a constant amount of total sulfur in the gas phase. NAGASHIMAand KATSURA (1973) also recognized the same phenomenon in the Na,O-SiO, system and clarified that the solubility of sulfur increases greatly with increasing the Na,O content. ~WACLEAN(1969) determined liquidus phase relations in the FeS-FeO-Fe,O,-SiO, system, and deduced that the amount of sulfur dissolved in basic magma appears to be in the order of 0.1 wt % or less. Sm and CUE (1973) studied ~q~dus relations in the FeS-FeO-SiOz-Na,O system, and compared their results with those of MacLean. SKINNER and PECE (1966, 1969), and DESBOROUGHet a,?.(1968) found immiscible sulfide melts from the Hawaiian basaltic lavas. SKINNER and PECK (1969) determined a sulfur content of a differentiated silioeous liquid confined within interstices of the upper crust of the lava lake to be 0.038 per cent S by weight at 106.!Y’C.MOORE and FABBI (1971) have estimated the amount of the juveniie sulfur content of the basalt melt from the mantle to be 800 -& 150 ppm on the basis of 3
617
518
TAKASHI KATSKJXA
and Srrmwu
NAQASHIMA
outer glassy parts of submarine erupted basalt. Recently, AWDERSON (1972, 1973) focused attention on tiny inclusions of glass trapped within crystals prior to eruption. He concluded that most magmas are sulfur-saturated prior to eruption, and sulfur contents in glass inclusion are approximately constant at 800-1600 ppm. HAUGHTON and SKINNER (1972), and ~UGHTON and ROEDER (1972) studied the solubility of sulfur in a melt of basaltic composition coexisting with an immiscible sulfide melt. They pointed out that sulfur in saturated silicate melts shows strong positive correlation with Fe0 and TiO, in melts. The present objectives are not only to clarify the solubility of sulfur in some rock melts at 1 atm total pressure, but also to estimate the amount of sulfur compounds in volcanic gases derived from the melts. The present explanation will be limited to the case of basaltic liquid immediately after extrusion at 1 atm total pressure, because both temperature a,nd the oxygen partial pressure of the typical basaltic magma have been successfully measured and have also been estimated on the basis of experiments. EXPERIMENTAL Three volcanic rocks with the different chemical composition were chosen. They were investigated petrographically and chemically by MACDONALD and KATSURA (1964). KATSUEA (1967) has determined the liquidus temperature of tholeiite basalt C-132 used in the present study under consideration of the effect of oxygen partial pressures. In the present study, liquidus temperatures of both hawaiite C-45 and rhyodacite were determined as a function of I’,, under a petrographic microscope using thin sections. Results showed that these three rocks were completely in the liquid state over the present range of PO at 125O’C and at 1300%. YODER and TIDY (1962) have determined liquidus temperaturesoftholeiite (No. 7a in Table 14) and of oxidized hawaiite (No. 23 in Table 14). Samples No. 78 and No. 23 are similar in composition with tholeiite basalt C-132 and hawaiite C-45 in the present specimens, respectively. According to their results, No. 7a and No. 23 were in liquid state at 1250% though they did not control the oxygen partial pressure. In our present study of hawaiite C-45, magnetite appeared at 1220% as a primary phase at 1O-3’* atm PO,, followed by peeudobrookite (1 lSO%), plagioclaso (1165”C), and clinopyroxene (114O’C) at the same PO, condition. However, at lOa atm Po2, plagioclase appeared at 1160°C as a primary phase, followed by clinopyroxene (1140%). Magnetite and pseudobrookite did not crystallize at such a low oxygen partial pressure. In the case of rhyodacite, plagioclase appeared at 113O’C aa a primary phase, followed by orthopyroxene at 1126% at an oxygen partial pressure of 10-s.* atm. Detailed results will be published in the near future. The chemical composition of the present rocks is given in Table 1. The sulfur contents determined by the method of NAGA~HIMA et al. (1972) are listed in Table 3 which will be seen later together with those in several Hawaiian basaltic rocks. The quenching method was adopted, and the procedures are the same as those described in previous papers by KATSURA and MUAN (1964) and by IWASAJLIand KATSURA (1967). Atmospheres of desired oxygen partial pressures and of various sulfur compounds were obtained by using CO,-Hz-SO, mixtures. The proportioning of three gases was made by a compoeite gas mixer, then equilibrated partial pressures of 0,, SO,, HsS, SO,, SO, COS, S,, HS, CS,, CS, CO,, CO, H, and H,O at 1loo’, 1250” and 1300°C were calculated with computer by the method of WHIR efal. (1968). In the present paper, we will distinguish the amount of the initial input SO, by using the term (SO& from the equilibrated amount of SO,. The thermodynamic data were taken from the JANAF Thermo&micd Tables (1966). Furnace and temperature control are the same as those described by IWASAKI and KAT~URA (1967), and furnace temperatures were kept constant to approximately f2’C. Actual temperatures within the f umace were measured with a Pt-87 per cent Pt13 per oent Rh thermocouple whioh was calibrated against the melting point of gold.
Solubility
of sulfur in some magmas
at 1 atmosphere
519
Table 1. Chemical composition of volcanic rocks used in the present study (wt %) 1 SiO, TiO, AWs Fe& Fe0 MnO MgC cao Na,O K‘AC H,O( -) H,C(+) P,Cs Total
50.37 3.09 14.02 1.88 10.07 0.17 6.75 10.39 2.35 0.62 0.04 0.16 0.32 100.23
2
3
45-84 3.59 16.90 3.48 9.93 0.22 4.95 7.92 4.03 1.16 0.32 0.34 0.78 99.82
66.78 0.59 15.69 1.45 1.40 0.05 1.28 2.61 4.49 3.60 0.66 0.59 0.58 99.77
1. Tholeiite basalt, (C-132). 2. Hawaiite (C-45) 3. Rhyodacite (TK 1501). (See paper MACDONALD snd KATSU-RA, 1964.)
by
NAOASHIMAand KATSURA(1973) measured the oxygen partial pressures of the gas phase by means of a solid electrolyte cell (KATSURAand HIASEGAWA, 1967). They concluded that the gaseous species involving sulfur compounds may be in equilibrium at 1250’ and 1300%. In the present study, we measured oxygen partial pressures in mixed gases with various COZ/Ha The relationship between measured and ratios containing a fixed initial concentration of (SO,),. calculated oxygen partial pressures was almost identical with that obtained previously. It is demonstrctted that at llOO°C, the equilibrium state within the gas phase is not established over the range from lO+ to 10-14 atm PO, at, the flow rate of 0.6 cm/set in the vertical quenchfurnace wound with 60 per cent Pt 40 per cent Rh wire. However, at 1250’ and 1300’%, measured oxygen partial pressures agreed well with calculated ones ranging from lo4 to lo-8 atm Pot, and deviated only slightly from calculated ones with decreasing oxygen partial increased with increasing concentration of (SO,)i. On the basis of the pressures. This deviation present measurements, it is presumed that the gas phase is approximately in equilibrium at temperatures above 1250% and at oxygen partial pressures above lo-l2 atm when the amount of (SO,), is below 2 per cent. Some relationships between our measured and calculated oxygen partial pressures are illustrated in Fig. 1. The check of equilibrium between melts and the gas phase was performed by varying the reaction time. Examples of these results are given in Fig. 2. In every sample, the reaction time from 3 to 6 hr was enough to approach the equilibrium state at 1250° and 1300°C when we used about 60-100 mg of a f?nely powdered sample. The 60 per cent Pt 40 per cent Rh alloy was used aa containers for heating rock samples in order to minimize the alloy formation between Pt and Fe in rock samples. As ascertained by SHIBATA(1967) and by NAGASHIECA and KATSURA( 1973). contents of iron and sodium in quenched glasses did not change seriouslyeven at lo-12 atm PO, and at 1300% when reaction times are shorter than 6 hr. Since the present apparatus and techniques are just the same as those of previous may not change signilicantJy after runs.
works, initial compositions
of the present samples
RESULTS ABNDDI~CTJ~~I~N Figure 3 shows the relationship
between the solubility
of sulfur in rock melts
and the oxygen partial pressure at a 2-l per cent (SOJi and at 125O’C.
As clearly
TAKASHIKATSURA
520
and SHIGERUNAGASHIMA
._.
..~_,_~_~__“~~~~~~ ., _.q
-T----T------
I6
I /
:
I
14.
1
12
7
IC
i
1
s2
/ “.‘ at-
a?
1
o”6 T
, /
;
!
41.
_’
Fig. 1. Relationshipbetween calculatedand observed oxygen partial pressuresat 1100’ and 1250%. A 2.1 per cent SO llooOcI~ 2.1 per cent SO,“.
12500C 0 0 per cent SO, 0 2.1 per cent SO,
-
0
/
I
2
3 Time,
4
5
IO
hr
Fig. 2. Cunreeshowing changes of sulfur content in rock melts vs heating time at 1250% and at 2.1 per cent (SO,),. A Hawaiite at 10-xa.w,atm PO,; A hawaiite at 10-3.66 atm P o,; 0 tholeiite basalt at 10-12.20atm PO,; l tholeiite basalt at 10-3.66atm P OS’
Solubility of sulfur in some magmsa at 1 atmosphere
1 0
1
2
521
I 4
6
6
IO
12
-log PO2
Fig. 3. Relationship between the solubility of sulfur in rock melts and PO, at 1250% and at 2-l per cent (SO,),. 0 Tholeiite basalt (C-132); @ hawaiite (C-15); l rhyodacite (TK 1501).
seen in Fig. 3, each representative rock melt shows a minimum solubility of total sulfur at an oxygen partial pressure around lo-’ atm which seems to be independent of rock composition, though the amount of total sulfur in melts varies with the rock composition. The solubility of total sulfur in tholeiite basalt melt increases with increasing the (SO,), in the gas phase, as shown in Fig. 4. The relationship between the concentration of (SO,)* in the gas phase and the solubility of sulfur in the tholeiite basalt melt in term of -log (per cent S) at 125O’C and at isobaric oxygen partial pressures is also derived from Fig. 4. The results are illustrated in Fig. 5 at oxygen partial pressures of lo- 6, lo-* and lo-lo atm. As seen in Fig. 5, each isobaric line seems to be straight and has an identical slope within experimental
Fig. 4. Relationship between the solubility of sulfur in tholeiite basalt (C-132) melt and PO, at 1250% under various concentrations of (SO,),. 0 2.1 per cent (SO&; A 1.3 per cent (SO,),; 0 0.6 per cent (SO,)+
522
TAKASEI
KATSKRA
and SEIOERUNAQASHIMA
Fig. 5. Relationship bet\veonthe concentration of (SO,), and the solubility of sulfur in tholeiite baa& (C-132) melt at 1250% under various isobaric conditions of P,*.
errors. However, the present relation in Fig. 5 has no theoretical justification. As pointed out in a previous paper by IWASAKI and KATSURA (1967), the solubility of hydrogen chloride in a basalt melt obey neither Henry’s nor Sievert’s laws when the solubility is above 0.03 mole HCl per 1 kg of the melt,. This may also be true for a region of some high solubility of sulfur. In addition, the term (SOJi does not mean the equilibrated partial pressure of a single molecule but means the equilibrated partial pressure of a single molecule but means the sum of partial pressures of molecules containing sulfur. Therefore, we cannot extrapolate the present limiting and empirical relation to very high values of (SO.Jj. FINCEIARIand RICIIARDSON (1954) assumed that sulfur dissolves in melts as sulfate at relatively high oxygen partial pressures, and as sulfide at relatively low oxygen partial pressures on the thermodynamic calculation. In a previous paper, NAQASHIMA and KATSURA (1073) proved this thermodynamic prediction by means of chemical analysis. In the present experiment, the sulfide- and sulfate-sulfur in melts were determined by the same method developed by XAGASRWA et al. (1972). Results of the tholeiite basalt arc given in Table 2, together with the value of -log PO,. As seen in Table 3, af oxygen partial pressures above 10-6.8 atm, sulfur in the melts is in the form of sulfate, and at oxygen partial pressures below lo-* atm , it is in the sulfide form. The minimum amount of dissolved sulfur is below 0401 per cent S, and the corresponding oxygen partial pressure to this minimum point is around lO-‘.O atm at 125O’C. It should be noticed that the equilibrium amount of sulfur in melta increases remarkably at, oxygen partial pressures below IO-lo atm at 1250°C when the rock melts are rich in iron. Thoiite basalt and hawaiite are case in point-these two have a mafic composition and amounts of total iron are in the range from 13 to 14-5 per cenf as l?e,O,. Rhyodacite, on the contrary, has a salic composition having
Solubility of rmlfuriu some megnag at 1 atmosphere
623
Table 2. Sulfide- and &f&e-sulfur oontents iu tholeiite baalt (C-132) melts & 1260°C and at 2.1 per cent (SO,)t sulfur
-1% PO, 3.65 5-38 6.79 8.97 IO.66 12.20
Total S O-006 o-003 o-001 0.009 0.022 0.11
content (wt %) Sulfide to*001 <0~001
sulfate 0.006 o-003 O*OOl 0.001
a low amount of iron but with a high amount of alkalies. If we use the results illustrated in Fig. 3, and plot the total amount of dissolved sulfur against the iron content in the three melts at lo-lo atm PO, and at f250cC, we observe that the total amount of dissolved sulfur which is in the form of sulfide increases with increasing total iron. On the contrary, it was impossible to observe a significant relationship between dissolved sulfur and other components in the melts. FINCHAM and RICHARDSOET(1954) and OLSHBNSEII (1951) observed the same relation as mentioned above in the FeO-SiO, fused system at relatively low oxygen partial pressures. They explained that the anomalous enrichment of sulfur is due to the formation of troilite (FeS) in both liquid metallic and liquid oxide phases. Recent studies by B.&GLEAN (1969), and S~UMAZAEI and CLARK (1973), and by HAUCWTON and SEIINNER (1972), HAUGIHTON and ROEDER(1972) on a basaltic melt also confirmed the positive relation of the solubility of sulfur to the amount of ferrous oxide present in melts. At an oxygen partial pressure of lo- la.20atm, the solubility of sulfur in tholeiite basalt melt reached 0.1 I per cent as given in Table 2. As described by SKINNERand PEUK(1969), the solubility of sulfur in a silicate melt saturated with sulfide may be controlled by many variables. In the present study, however, we cannot discuss anything about the ~t~ation of sulfur, because we failed to observe the existence of separate iron sulfide phases in this quenched sample. We will use the solubility data obtained only above 10-l* atm PO*in later discussions. Figure 6 shows the relationship between the amount of dissolved sulfur in melts and the oxygen partial pressure at 2-l per cent (SO& in the gas phase at 1300°C. In the cases of tholeiite basalt and hawaiite, the minimum solubility is below O-001 per cent S at which the oxygen partial pressure is around lOA atm. Thus, the value of oxygen partial pressure at which the minimum solubility was observed increases with increasing ~rn~rat~e at a constant (SO& though the amount of dissolved sulfur at this minimum point is nearly the same at each temperature. It may be experimentally reasonable that at lZOO”C, the minimum point may be expected to be around 10” atm. This shift of the minimum point corresponds to the change of partial pressures of sulfur ~ompo~ds in the gas phase. Figure 7 shows the simplified relationship between partial pressures of sulfur compounds (SO,, H,S and SO,) and the oxygen partial pressure at llOO”, 1250’ and 13OO’C. As seen in Fig. 7, the partial pressure of SO, is equal to that of H,S at the oxygen
524
TA&AS~
KATSURA
and
Smamu
NAGASHIMA
Fig. 6. Relationship between the solubility of sulfur in rook melts and .Por at 1300% and at 2.1 per cent (SO,),. Symbols are the asme as those in Fig. 3.
4
6
12
8
14
-log Pa2
Fig. 7. Relationship between caloulated partial pressures of SO,, SO, and H# twdcalculated.Po, at2.1 per cent (SO,), and at 1100’ 1260’ and 1300%. Calculated pa&a3 pressuresof E&O, CO,, CO, H,, SO, S, HS, COS, CS and CS, are omitted. C&x&&d partial pressures of O,, SO, and H&3 at points Px, Pz and Pa are as follows: 1260°
1300°
PI
P,
P,
8.323
6.955
6.666
f6.987
6.634
6-644
lloo” --log PO, --log P’s& ( = --log P&S) The Psor at each P,,
is the same, and the value of -log
PO, is 1.678.
Solubility of sulfur in some magmaa at 1 atmosphere Table 3. Sulfur content
in some Hawaiian
rocks
(wt %) Total S Pole’s hair Pele’s tear TK 2101 IkiNo.2 TK 1805 TK 00018 TK 2205 TK 2201 TK 1501 C-132 C-6 C-42 c-45 C-56 C-62-1 c-72 c-91 C-92 c-97 c-100 c-105 c-111 c-112 c-117 C-118 c-120 C-128
0.018 0.016 0.002 0.003 0.010 0.003 0.003 0.002 0*006 0.006 0*002
Sulfide
Sulfate
0.018 0.016
0.010
0.006
0.003
0.036
Pele’s hair and Pele’s tear; ejected during the early stages of the 1959 eruption of Kilauea Iki, collected by Dr. H. Ikowa, University of Hawaii, Nov. 22, 1969. TK 2101; the 1960 eruption of Kilauea Iki, inside of the lava lake. Collected by T. Kataura. Iki No. 2; Core from drill hole at depth of 4 ft from the surface of the lava lake, Kilauea Iki. See a paper by MACDONALD and KATSURA (1961). TK 1806; the 1960 spatter cone of Kilauea. first few hours of the eruption, northwest of Kapoho Village. Collected by T. Katsure. TK 60018; the 1955 lava flow of Kilauea, May 26, 1965. Collected by T. Katsura near Ilewa Crater. TK 2205; the 1935 lava of the Mauna Loa, Pahoehoe lava, 2 miles easat of Puu-Huluhulu. Collected by T. Katsura. Remarks for other samples are seen in a paper by MACDONALD and KATSURA (1964)
626
526
TAKASHI
and SIIIQERIJ NAGASHIMA
KATSURA
Fig. 8. Relationship between PO, and the solubility of sulfur in tholeiite baa& (C-132) melt at 2.1 per cent (SO,), under various isothermal conditions.
partial pressure of lo- 13.~55 atm (Pz in Fig. 7) at 1250°C. This point P, moves to the point P, where the oxygen partial pressure is 10-s~sssatm when the temperature is raised to 1300°C. These oxygen partial pressures coincide with those indicating minimum solubilities with equal amounts of sulfide- and sulfate-sulfur in melts, and these facts are necessary to estimate the solubility relation at 1200°C or at 1150°C which is illustrated in Fig. 8. Figure 9 shows the relationship between -log (per cent S)meltand the concentration of (SO,)i in the gas phase at 1200°C under various oxygen partial pressures. In drawing Fig. 9, we assume the same slope of -log (per cent S),,,,/(p er cent SO,), for each isobaric line as that obtained at
I -T---1 1
I~_
r
I
/
,
QOL,,’
,,a0
$ m
.
,
/’
/‘,
’
\o
' @%,R' /'ye,,' ,60 , ,o ' I' ,"Qor
2
P --/ B
'KC ,e0 \o 3
'-4
I_
0
1_..--~-
/
2 %
3
-_J
5
( SO,);
Fig. 9. Relationship between concentration of (SO& and the solubility of sulfur in tholeiite basalt (C-132) melt at 1200% under various isobario conditions of PO . *
Solubilityof sulfurin some msgmaeat 1 atmosphere
529
126OY!, on which each amount of dissolved sulfur is plotted by using Fig. 8. Figure 9 will be used later to estimate the concentration of (SO,), in volcanic gases. The. e&nuth
of th concentration of (SO,), in volcanic gaees
The concentration of sulfur compounds in basaltic volcanic gases is now estimated in terms of (SO,), on the basis of the solubility of sulfur in basaltic rock melts. In the present discussion, we assume that a subaerially extruded basaltic magma is in equilibrium with volcanic gases at 1 atm total pressure. Many efforts have been defrayed by many investigators to estimate the extruded basaltic magmas (MINAKAMIet al., 1951; EATONand MURATA,1960; RICHTERand MURATA,1966; MURATAand RICHTER, 1966; KATSURA, 1967; SIQURGEIRSSON, 1966; SKIXNERand PECK, 1969). According to these measurements, it seems to be reliable that the temperature of the typical basaltic magma is around 1200°C at the highest. FUDALI (1965) and SHIBATA(1967) reported independently that the oxygen partial pressures of basaltic volcanic gases are around 1O-8atm at about 1200°C. KATSURA(1967) also estimated the oxygen partial pressure of Hawaiian basaltic volcanic gases being 1O-8.2atm at 1160°C. SATO and WRIGHT(1966) also estimated the oxygen fugacity of Makaopuhi lava, Kilauea, Hawaii, to be 1O-8.43atm at 12OO”C,based on the direct measurement of oxygen fugacity in holes drilled through the crust of Makaopuhi lava lake. Under these considerations, it is reasonable to conclude that the oxygen partial pressures of basaltic volcanic gases, coexisting with basaltic magmas, are of the order of IO-* atm at about 1200°C and at 1 atm total pressure. Several analytical data on the volcanic gases have been published, but the reported amounts of H,S and SO, vary widely. For example, SHEPHERD’Sdata (1938) of volcanic gases from Kilauea eruptions showed that the amount of SO, fluctuates from 8 to 30 per cent. In addition, the collected gases are considered to be frequently contaminated by air. On the basis of the thermochemical calculation, MATSUO(1960) estimated that the partial pressure of SO, in volcanic gases equilibrated with basaltic magma is 5.37 x 10e2 atm at 1100°K and at one atmosphere total pressure (the concentration of H,S is very small). MATSUO(1962) also proposed reliable values of concentrations of SO, in volcanic gases from Kilauea eruptions on the basis of the Shepherd’s analysis. According to Matsuo, corrected values of SO, are in the range from 3.7 to 13.6 per cent. SKINNERand PECK(1966) estimated the sulfur fugacity in drill-holes at Makaopuhi lava lake, Kilauea, and presented the value 10-1.5*5.0atm Ps at 1066°C based on the sulfide mineral assemblages. and ELIL-BON This corresponds to 2-20 per! cent SO, in volcanic gases. SI~VALDASON (1968) reported that the SO2 concentration in volcanic gases directly collected from the Surtsey lava lake is in the range from 164 to 6.40 per cent at 1400°K. They emphasized that the collected gas samples are hardly contaminated by impurities. FINLAYSONet aZ. (1968) summarized the volcanic research in Hawaii, and estimated the concentration of SO, in oceanic volcanic gases on the basis of their study and of early studies by HEALDet al. (1963), JAGY~ER (1940), MATSUO(1962), EATONand MURATA(1960), and SIQVALDASON and ELI~SON(1968). According to the estimation by FINLAYSONet al., the SO, concentration in Hawaiian ‘magmatic’ gases scatters
628
TAKA~HIKATSURAand SHIOERUNACASHIMA
from O-017 to 24.3 per cent. ‘Magmatic’ gases from Hawaii include gases collected from holes drilled through the solid crust, and these drill-hole gases seem to be concentrated by SO,. Recently, NORDLIE (1971) estimated the composition of the magmatic gas of Kilauea after removal of atmospheric contamination including 0,, N,, and removal of water based on the smallest amount of water found in a sample J-S. Then, he assumed that carbon has been neither added nor lost from the magmatic gas. He postulated the C/S ratio in magmatic gases, and calculated the partial pressure of equilibrated SO, in Kilauean volcanic gases at I atm total pressure and at 1100°C to be 053 atm or 0*27 atm when C/S is 05 or 15, respectively (the concentration of H,S is very small). In order to estimate the concentration of total sulfur compounds in volcanic gases expressed as (SO,)i on the basis of solubility data, the most important thing is to obtain a glass sample representing a magma equilibrated with a volcanic gas at 1 atm total pressure. MACDONALD and KATSURA (1961) focused attention on the Pele’s hair wafted from the crater of Kilauea Iki, Hawaii, erupted in November, 1959. They considered that the Pele’s hair was possibly quenched from high temperature as a glass. KATSURA (1967) also determined the liquidus temperature of the Pele’s hair under various oxygen partial pressures, and he concluded that the chemical composition of the Pele’s hair may present the liquid part of the magma extruded from the Kilauea Iki crater. As listed in Table 3, the sulfur content of the Pele’s hair is 0.018 per cent, and that of the Pele’s tear collected at the same time is 0.016 per cent S. The former consists wholly of a quenched glass, but the latter contains olivine phenocrysts which may be nuclei to form a spherical tear. The amount of olivine in the Pele’s tear was variable, but was estimated roughly to be lo-20 per cent. Thus, the content of sulfur in the glass part of the Pele’s tear is almost the same as that in the Pele’s hair. We assume with a considerable degree of certainty that the value 0.018 per cent S in Pele’s hair may represent the solubility of sulfur in the magma subaerially extruded in the 1959 eruption of Kilauea Iki. If so, the concentration of (SO,), in volcanic gases may be calculated to be 5-l per cent at 1200°C and at lo--* atm PO, with an aid of Fig. 9. This value is consistent with those directly measured by SI~VALDASON and ELISSON (1968) in Surtsey volcano. The present value agrees also with estimated average concentrations by MATSUO (1962) (6.7 per cent SO, as an average of J.16, J.13, and 5.2) and by SKINNER and PECK (1966) (6.7 per cent SO,), though there is a difference between the Kilauea Iki eruption of 1959 and other activities of summit lava lakes in extensive outgassing. The sulficr content of Hawaiian rocks According to CLARKE and WASHINGTON (1924), the average content of sulfur in igneous rocks is estimated to be O-052 per cent S, and RICKE (1960) presented the value 0.03 per cent S as the average. TAYLOR (1964) preferred the value 0.025 per cent S as the average of basaltic rocks. Recently, MOORE and FABBI (1971) determined the sulfur content of subaerially erupted oceanic basalt and of submarine erupted basalt by means of X-ray fluorescence. They give an average content of X-ray fluorescence. They give an average content of 107 ppm S, and 680 ppm S for subaerial and submarine basalts, respectively. Their analytical results show that
Solubility of sulfur in some magma
at 1 atmosphere
529
a spatter erupted August, 1969, from Mauna Ulu, Kilauea, contains O-017 per cent S, and a pumice erupted July 11, 1961, from Halemaumau, Kilauea, contains O-018 per cent S. These values are identical with that of the Pele’s hair. After careful studies, they concluded that this difference is the results of retention of sulfur in basalt quenched on the sea floor at pretty high pressures and loss of sulfur in basalt by degassing at the surface. ANDERSON(1973) also studied the sulfur content of glass inclusions in crystals from basic rocks, and found high contents of sulfur up to 0.26 per cent by weight. In contrast to these high concentrations, OZAWA et al. (1972) reported that the sulfur content in Japanese volcanic rocks is significantly low, and they obtained app~~rna~ly 0*005 per cent S as an average value for Japanese basaltic rocks. In order to check this tendency, we analyzed a large number of subaerially erupted Hawaiian volcanic rocks, and found that the sulfur content in Hawaiian basaltic rocks is almost the same as those in Japanese basaltic rocks. The detailed results will be published in the near future, but some results are given in Table 3 for the convenience of the present discussion. Samples of TK-series were collected by one of the present authors under supervision of G. A. Macdonald, University of Hawaii. Samples of C-series were collected by G. A. Maedonald, and their petro~ap~c and chemical properties have been pub~shed (IMACDONALD and KATSURA, 1964). In the usual sense, these samples are fresh except for C-45 under microscope. As listed in Table 3, typical Hawaiian tholeiite basalts contain less than 0.005 per cent S. In contrast to the sulfur content in the Pele’s hair, samples TK 2101 and Iki No. 2 contain very small amount of sulfur, as seen in Table 3. These two samples also represent the solidified magma of the Kilauea Iki eruption in 1959. Thus, it may be true as pointed out by MOOREand FABBI (1971) that almost all sulfur dissolved in a subaerially extruded magma at 1 atm total pressure in equ~b~um with coexisting volcanic gases may be degassed during the slow cooling after extrusion. Acknowledgements---Thepresent authors deeply thank Dr. BRIAE J. SKINNER,Yale University, and Dr. ALFEEDT. ANDERSON,JR., University of Chicago, for their thorough criticisms to the present study. We also thank deeply Professor GORDONA. MACDONALD, University of Hawaii, who kindly permitted the use of Hawaiian volcanic rocks, and thank Dr. H. OSAKA, Tokyo Institute of Technology, who helped us to program the digital aomputation for obtaining partial pressuresof chemical species in the gas phase. Dr. &nAO &fATSUO, Tokyo Institute of Technology, read the present manuscript and encouraged us t~oughout the study. REFERENCES ANDERSONA. T. (1972) Sulfur and chlorine contents of glass inclusions in phenocrysts and basaltic host glasses. Fluid Inclusions Res. Proc. COFFI, Vol. 3. ANnERsONA. T. (1973) Chlorine and sulfur in and out of some basaltic magmas. Submitted to Geol. Sot. Amer., May 1973 (personal communication). CLAEEEF. W. and WASHINGTON H. S. (1924) The composition of the earth’s crust. U.S. c3’eoZ. Sure. Prof. Paper 127, p. 16. DESBOROU~H G. A., AE~EESONA. T. and WEXOHTT. L. (1968) Mineralogy of sulfides from certain Hawaiian basalts, &on. i&o& 68, 636-644. EATONJ. P. and MURATAK. T. (1960) How volcctnoesgrow. Science132, 925-938. FINCHAMC. J. B. and RICHARDSON F. D. (1964) The behaviour of sulfur in silioateand &miuate melts. Pmt. Roy. Sot. London A%& 49-62. FINLAYSONJ. B., BAEEES I. L. and NAUUHTONJ. J. (1968) Developments in volcfmic gas research in Hawaii. &ophya. Monogr. l.2, 426-438.
530
T~SHI
KATSURA
and SEIGERU NA~AYHIMA
Fu~plcr R. F. (1965) Oxygen fugacities of basaltic snd sndesitic magmss. C;reochim,Cosmochi~n. Acta 22, 1063-1075. HAUGHTON D. R. and SKINXER B. J. (1972) Chemistry of sulfur in melts. Abstr. 24th International Geological Congress, p. 420. HAUUECTON D. R. and ROEDER P. L. (1972) Iron and sulfur in basaltic liquids. Abstr. Can. Mineral. 11,574. BALD E. F., NAUUHTONJ. J. snd BARNES I. 1;. (1963) The chemistry of volcanic gases. 2. Use of eq~ibrium oalibrations in the interpretation of volcanic gas samples. J. ~&o~~~~. Res. 68, 545577. IWASAKI B. and KATSURA T. (1967) The solubility of hydrogen chloride in volcanic rock melts. Bull. Chem. Sot. Japan 40, 554-561. JAoamz T. A, (1940) Magmatic gases. Amer. J. Sci. 88, (8) 313-353. JANAP Xhewnoclaemical Tables (1965) U.S. Depsrtment of Commerce/National Bureau of Standards. KATSURA T. and MUAN A. (1964) Experimental study of equilibria in the system FeO-Fe,O,Cr,O, at 1300°G. Tram. AIXX 220, 77-84. KATS~~A T. (1967) Pele’s hair as s liquid of Hawaiian tholeiitic bass&s. Get&em. J. 1, 157-168. KATSURA ‘I’. snd HASEGAWAM. (1967) Equilibria in the V,O,-VO, system at 1600°K. BUZZ. Chem. Sot. Japa7a 40,561~569. MACDONALDG. A. and KATST~A T. (1961) Variation in the lava of the 1959 eruption in Kilauea Iki. Pac. Sci. 15,358-369. MACDONALDG. A. and KATS~XA T. (1964) Chemical composition of Hswaiisn lavas. J. Petrol. 5, 82-133. MACLEAN W. H. (1969) Liquidus phsse relations in the FeS-FeO-Fe,O,-SiGs system end their application in geology. Icon. Geol. 64, 865-884. MATS~O S. (1960) On the origin of volcanic gases. J. _&z&h. Sci. ~‘ug~ga L&iv. 8, 222-245. *daTsvo S. (1962) Es~blishme~t of chemical equilibrium in the volcsnic gas obtained from the lava lake of Kilauea, Hawaii. Bull. Volcanol. 24, 59-71. MINAKAMIT., MIYA~AEI T. and TAI(AHASKIT. (1951) The 1950-1951 eruptiou of Oo-sima and its seismetrical investigations. (1) Bull. Earthqualce Res. In.&. Tokyo Univ. 29, 359-381. MOOREJ. G. and FABBI B. P. (1971) An estimate of the juvenile sulfur content of basalt. Contrib. illinerctl. Petrol. 33, 118-127. MURA~AK. J. and RICHTERD. II. (1966) The settling of ohvine in Kilsueitn magma as shown by lavas of the 1959 eruption. Amer. J. SC& 284, 194-203. NAC;ASHIXAS., YOSHIDA M. and OZAWA T. (1972) The deter~nation of sulfide- and sulfstosulfur in igneous rocks with tin (H-strong phosphoric acid snd strong phosphoric acid. Bull. Chem. Sot. Japan 45, 3446-3451. NAUAS~IMA S. and KATSURA T. (1973) The solubility of sulfur in Na,O-SiO, melts under various oxygen partial pressures. Bull. Chem. Sot. Japan 46, 3099-3103. NORDLIE B. E. (1971) The composition of the magmatic gas of Kilauea and its behavior in the near surface environment. Amer. J. Sci. 271, 417-463. OLSHANSKIX YA. I (1951) quoted from the paper by FXNCBMANand RICHARDSON(1954). OZAFVAT., NAGA~HIMAS., YOSMDA M., ARIKAWA Y. and IWASAKI I. (1972) Sulfur content of igneous rocks. Personal co~unication. ST. PIERRE D. H. and CRX~MANJ. ~1956} Sulfur equilibria between gases and slags containing FeO. Trune. AI&U% 206, 1474-1483. RICHZER D. H. and MURATAK. H. (1966) Petrography of the lavas in the 1959-60 eruption of of Kilauea volcano, Hawaii. U.S. Beol. Sure. Prof. Paper, 537-D. RIC~E W. (1960) Ein Beitrag zur Geoahemie des Schwefels. Geochim. Cosmoch/im. Acta 21,35-80. SATO M. and WRI~RT T. L. (1966) Oxygen fug&ties directly measured in magmatic gases. Science lfi3, 1103-1105. SHICP~ E. S. (1938) The gsses in rocks and some mIsted problems. Amer. J. SC& 35A, 31 l-351. SHIBATA K. (1967) The oxygen psrtisl pressures of the magma from Mihara voloano, O-aims, Japan. B&. C76em.Sot. Japan 40,836-834. SHI~~I H. and CLA~E L. A. (1973) Liquidus relations in the FeS-FeO-SiO-Na,O system and geological implications. Econ. Beol. 68, 79-96.
Solubility of sulfur in some magma8 at 1 atmosphere
631
SIQDBQEIILSSON TH. (1900) Geophysical meaaurementain Surtsey carried out during the year
of 1965. Surt~y Rec. Prog. Report II. The Surtsey Res. Sot., Reykjavik, Iceland. G. E. and ELISIONG. (1968) Collection and analysis of volcanic gases at Surtsey Iceland. &o&m. Coemochim. Acta 82, 797-805. SKIN-NER B. J. and PECK D. L. (1960) The solubility of sulfur in basic magmaa. Ewn. &XL 61, 802. SKINNER B. J. and PECK D. L. (1909) An immiscible sulfide melt from Hawaii. Econ. i3eoZ. Monoqr. 4, 310-322. TAYLORS. R. (1964) Abundance of chemical elements in the continental crust. A new table. Geochim. Coemochim. Acta 28, 1273-1285. !RIILKDOOAN E. T. and DARKENL. 5. (1961) Sulfur equilibrium between gases and calcium ferrite. Trans. AIME W1,464-474. WHITE W. B., JOHNSONS. M. and DANTZIOG. B. (1958) Chemical equilibrium in complex mixture& J. Chem. Phya. 28, 761-756. YODER H. S., JR. and TILLEYC. E. (1962) Origin of basalt magma: an experimental study of natural and synthetic systems. J. Petrol. 3, 342-632. SIGVALDASON
Solubility of sulfur in some magmas at 1 atmosphere Tmsnr
KATSURA
and Srrmxnu HAGASHIMA
Department of Chemistry, Faculty of Science, Tokyo Institute of Technology, Ookayama, Yeguro-ku, Tokyo (Received24 May 1973; accepted in revised form 27 September 1973)
Abstract-h
order to understand the distribution of sulfur in igneous rooks, we determinedthe solub~ity of sulfur in volcanic rock melts (tholeiitebasalt, hawaiite and rhyoda&te from Hawaii) at vmriousgas compositions and at 1250° and 1300% and 1 atm total pressure. The solubility of sulfur in the melt passes through a minhmnn with change in oxygen partial pressure,if other factors are held constant. For the basaltic liquid at 1200°C, most sulfurin the melt is as dissolved suhlde (S-e) at oxygen partial pressures below 10--8 atm and as dissolved sulfate at oxygen partial pressuresabove 10-e atm. Based on the present solubility data, 6 per cent is inferredfor voiaanie gas at 1 atm total pressurein equilibriumwith subaeriallyextruded Hawaiian tholeiite basalt (Pele’s hair with 180 ppm S) at 1200% and lOa atm Po,.
THE smm content in igneous rocks has been studied by several investigators to obtain the average amount of sulfur in the crust. These are painstaking studies, but are insufficient to clarify the general rules covering the global ~t~bntion~f sulfur in igneous rocks. Because sulfur is one of the volatile constituent in a magma, we cannot apply the distribution law based on the crystallo-chemical properties recognized in metallic minor elements to the distribution of sulfur. Recently, several investigators focused their attentions on the solubility of gaseous species in magmas in order to clarify original contents of some volatile constituents in magmas at high tem~rat~s and pressures. The solubility of sulfnr in rather simple silicate melts was studied experimentally by FINcw and RICHARDSON(X954), ST. PIERRE and CHIPMAN (1956), ~OQAK and DARKEN (1961), MACLEAN (1969), Su and CLARK (1973), and NAGAsm and KATSURA (1973). Pmcm and RICHARDSON (1954) studied the solubility of sulfur in the CaO-A&O,-SiO, system at high temperatures. They obtained a ~mum value in the solub~ty of sulfur as a function of the oxygen partial pressure at a constant amount of total sulfur in the gas phase. NAGASHIMAand KATSURA (1973) also recognized the same phenomenon in the Na,O-SiO, system and clarified that the solubility of sulfur increases greatly with increasing the Na,O content. ~WACLEAN(1969) determined liquidus phase relations in the FeS-FeO-Fe,O,-SiO, system, and deduced that the amount of sulfur dissolved in basic magma appears to be in the order of 0.1 wt % or less. Sm and CUE (1973) studied ~q~dus relations in the FeS-FeO-SiOz-Na,O system, and compared their results with those of MacLean. SKINNER and PECE (1966, 1969), and DESBOROUGHet a,?.(1968) found immiscible sulfide melts from the Hawaiian basaltic lavas. SKINNER and PECK (1969) determined a sulfur content of a differentiated silioeous liquid confined within interstices of the upper crust of the lava lake to be 0.038 per cent S by weight at 106.!Y’C.MOORE and FABBI (1971) have estimated the amount of the juveniie sulfur content of the basalt melt from the mantle to be 800 -& 150 ppm on the basis of 3
617
518
TAKASHI KATSKJXA
and Srrmwu
NAQASHIMA
outer glassy parts of submarine erupted basalt. Recently, AWDERSON (1972, 1973) focused attention on tiny inclusions of glass trapped within crystals prior to eruption. He concluded that most magmas are sulfur-saturated prior to eruption, and sulfur contents in glass inclusion are approximately constant at 800-1600 ppm. HAUGHTON and SKINNER (1972), and ~UGHTON and ROEDER (1972) studied the solubility of sulfur in a melt of basaltic composition coexisting with an immiscible sulfide melt. They pointed out that sulfur in saturated silicate melts shows strong positive correlation with Fe0 and TiO, in melts. The present objectives are not only to clarify the solubility of sulfur in some rock melts at 1 atm total pressure, but also to estimate the amount of sulfur compounds in volcanic gases derived from the melts. The present explanation will be limited to the case of basaltic liquid immediately after extrusion at 1 atm total pressure, because both temperature a,nd the oxygen partial pressure of the typical basaltic magma have been successfully measured and have also been estimated on the basis of experiments. EXPERIMENTAL Three volcanic rocks with the different chemical composition were chosen. They were investigated petrographically and chemically by MACDONALD and KATSURA (1964). KATSUEA (1967) has determined the liquidus temperature of tholeiite basalt C-132 used in the present study under consideration of the effect of oxygen partial pressures. In the present study, liquidus temperatures of both hawaiite C-45 and rhyodacite were determined as a function of I’,, under a petrographic microscope using thin sections. Results showed that these three rocks were completely in the liquid state over the present range of PO at 125O’C and at 1300%. YODER and TIDY (1962) have determined liquidus temperaturesoftholeiite (No. 7a in Table 14) and of oxidized hawaiite (No. 23 in Table 14). Samples No. 78 and No. 23 are similar in composition with tholeiite basalt C-132 and hawaiite C-45 in the present specimens, respectively. According to their results, No. 7a and No. 23 were in liquid state at 1250% though they did not control the oxygen partial pressure. In our present study of hawaiite C-45, magnetite appeared at 1220% as a primary phase at 1O-3’* atm PO,, followed by peeudobrookite (1 lSO%), plagioclaso (1165”C), and clinopyroxene (114O’C) at the same PO, condition. However, at lOa atm Po2, plagioclase appeared at 1160°C as a primary phase, followed by clinopyroxene (1140%). Magnetite and pseudobrookite did not crystallize at such a low oxygen partial pressure. In the case of rhyodacite, plagioclase appeared at 113O’C aa a primary phase, followed by orthopyroxene at 1126% at an oxygen partial pressure of 10-s.* atm. Detailed results will be published in the near future. The chemical composition of the present rocks is given in Table 1. The sulfur contents determined by the method of NAGA~HIMA et al. (1972) are listed in Table 3 which will be seen later together with those in several Hawaiian basaltic rocks. The quenching method was adopted, and the procedures are the same as those described in previous papers by KATSURA and MUAN (1964) and by IWASAJLIand KATSURA (1967). Atmospheres of desired oxygen partial pressures and of various sulfur compounds were obtained by using CO,-Hz-SO, mixtures. The proportioning of three gases was made by a compoeite gas mixer, then equilibrated partial pressures of 0,, SO,, HsS, SO,, SO, COS, S,, HS, CS,, CS, CO,, CO, H, and H,O at 1loo’, 1250” and 1300°C were calculated with computer by the method of WHIR efal. (1968). In the present paper, we will distinguish the amount of the initial input SO, by using the term (SO& from the equilibrated amount of SO,. The thermodynamic data were taken from the JANAF Thermo&micd Tables (1966). Furnace and temperature control are the same as those described by IWASAKI and KAT~URA (1967), and furnace temperatures were kept constant to approximately f2’C. Actual temperatures within the f umace were measured with a Pt-87 per cent Pt13 per oent Rh thermocouple whioh was calibrated against the melting point of gold.
Solubility
of sulfur in some magmas
at 1 atmosphere
519
Table 1. Chemical composition of volcanic rocks used in the present study (wt %) 1 SiO, TiO, AWs Fe& Fe0 MnO MgC cao Na,O K‘AC H,O( -) H,C(+) P,Cs Total
50.37 3.09 14.02 1.88 10.07 0.17 6.75 10.39 2.35 0.62 0.04 0.16 0.32 100.23
2
3
45-84 3.59 16.90 3.48 9.93 0.22 4.95 7.92 4.03 1.16 0.32 0.34 0.78 99.82
66.78 0.59 15.69 1.45 1.40 0.05 1.28 2.61 4.49 3.60 0.66 0.59 0.58 99.77
1. Tholeiite basalt, (C-132). 2. Hawaiite (C-45) 3. Rhyodacite (TK 1501). (See paper MACDONALD snd KATSU-RA, 1964.)
by
NAOASHIMAand KATSURA(1973) measured the oxygen partial pressures of the gas phase by means of a solid electrolyte cell (KATSURAand HIASEGAWA, 1967). They concluded that the gaseous species involving sulfur compounds may be in equilibrium at 1250’ and 1300%. In the present study, we measured oxygen partial pressures in mixed gases with various COZ/Ha The relationship between measured and ratios containing a fixed initial concentration of (SO,),. calculated oxygen partial pressures was almost identical with that obtained previously. It is demonstrctted that at llOO°C, the equilibrium state within the gas phase is not established over the range from lO+ to 10-14 atm PO, at, the flow rate of 0.6 cm/set in the vertical quenchfurnace wound with 60 per cent Pt 40 per cent Rh wire. However, at 1250’ and 1300’%, measured oxygen partial pressures agreed well with calculated ones ranging from lo4 to lo-8 atm Pot, and deviated only slightly from calculated ones with decreasing oxygen partial increased with increasing concentration of (SO,)i. On the basis of the pressures. This deviation present measurements, it is presumed that the gas phase is approximately in equilibrium at temperatures above 1250% and at oxygen partial pressures above lo-l2 atm when the amount of (SO,), is below 2 per cent. Some relationships between our measured and calculated oxygen partial pressures are illustrated in Fig. 1. The check of equilibrium between melts and the gas phase was performed by varying the reaction time. Examples of these results are given in Fig. 2. In every sample, the reaction time from 3 to 6 hr was enough to approach the equilibrium state at 1250° and 1300°C when we used about 60-100 mg of a f?nely powdered sample. The 60 per cent Pt 40 per cent Rh alloy was used aa containers for heating rock samples in order to minimize the alloy formation between Pt and Fe in rock samples. As ascertained by SHIBATA(1967) and by NAGASHIECA and KATSURA( 1973). contents of iron and sodium in quenched glasses did not change seriouslyeven at lo-12 atm PO, and at 1300% when reaction times are shorter than 6 hr. Since the present apparatus and techniques are just the same as those of previous may not change signilicantJy after runs.
works, initial compositions
of the present samples
RESULTS ABNDDI~CTJ~~I~N Figure 3 shows the relationship
between the solubility
of sulfur in rock melts
and the oxygen partial pressure at a 2-l per cent (SOJi and at 125O’C.
As clearly
TAKASHIKATSURA
520
and SHIGERUNAGASHIMA
._.
..~_,_~_~__“~~~~~~ ., _.q
-T----T------
I6
I /
:
I
14.
1
12
7
IC
i
1
s2
/ “.‘ at-
a?
1
o”6 T
, /
;
!
41.
_’
Fig. 1. Relationshipbetween calculatedand observed oxygen partial pressuresat 1100’ and 1250%. A 2.1 per cent SO llooOcI~ 2.1 per cent SO,“.
12500C 0 0 per cent SO, 0 2.1 per cent SO,
-
0
/
I
2
3 Time,
4
5
IO
hr
Fig. 2. Cunreeshowing changes of sulfur content in rock melts vs heating time at 1250% and at 2.1 per cent (SO,),. A Hawaiite at 10-xa.w,atm PO,; A hawaiite at 10-3.66 atm P o,; 0 tholeiite basalt at 10-12.20atm PO,; l tholeiite basalt at 10-3.66atm P OS’
Solubility of sulfur in some magmsa at 1 atmosphere
1 0
1
2
521
I 4
6
6
IO
12
-log PO2
Fig. 3. Relationship between the solubility of sulfur in rock melts and PO, at 1250% and at 2-l per cent (SO,),. 0 Tholeiite basalt (C-132); @ hawaiite (C-15); l rhyodacite (TK 1501).
seen in Fig. 3, each representative rock melt shows a minimum solubility of total sulfur at an oxygen partial pressure around lo-’ atm which seems to be independent of rock composition, though the amount of total sulfur in melts varies with the rock composition. The solubility of total sulfur in tholeiite basalt melt increases with increasing the (SO,), in the gas phase, as shown in Fig. 4. The relationship between the concentration of (SO,)* in the gas phase and the solubility of sulfur in the tholeiite basalt melt in term of -log (per cent S) at 125O’C and at isobaric oxygen partial pressures is also derived from Fig. 4. The results are illustrated in Fig. 5 at oxygen partial pressures of lo- 6, lo-* and lo-lo atm. As seen in Fig. 5, each isobaric line seems to be straight and has an identical slope within experimental
Fig. 4. Relationship between the solubility of sulfur in tholeiite basalt (C-132) melt and PO, at 1250% under various concentrations of (SO,),. 0 2.1 per cent (SO&; A 1.3 per cent (SO,),; 0 0.6 per cent (SO,)+
522
TAKASEI
KATSKRA
and SEIOERUNAQASHIMA
Fig. 5. Relationship bet\veonthe concentration of (SO,), and the solubility of sulfur in tholeiite baa& (C-132) melt at 1250% under various isobaric conditions of P,*.
errors. However, the present relation in Fig. 5 has no theoretical justification. As pointed out in a previous paper by IWASAKI and KATSURA (1967), the solubility of hydrogen chloride in a basalt melt obey neither Henry’s nor Sievert’s laws when the solubility is above 0.03 mole HCl per 1 kg of the melt,. This may also be true for a region of some high solubility of sulfur. In addition, the term (SOJi does not mean the equilibrated partial pressure of a single molecule but means the equilibrated partial pressure of a single molecule but means the sum of partial pressures of molecules containing sulfur. Therefore, we cannot extrapolate the present limiting and empirical relation to very high values of (SO.Jj. FINCEIARIand RICIIARDSON (1954) assumed that sulfur dissolves in melts as sulfate at relatively high oxygen partial pressures, and as sulfide at relatively low oxygen partial pressures on the thermodynamic calculation. In a previous paper, NAQASHIMA and KATSURA (1073) proved this thermodynamic prediction by means of chemical analysis. In the present experiment, the sulfide- and sulfate-sulfur in melts were determined by the same method developed by XAGASRWA et al. (1972). Results of the tholeiite basalt arc given in Table 2, together with the value of -log PO,. As seen in Table 3, af oxygen partial pressures above 10-6.8 atm, sulfur in the melts is in the form of sulfate, and at oxygen partial pressures below lo-* atm , it is in the sulfide form. The minimum amount of dissolved sulfur is below 0401 per cent S, and the corresponding oxygen partial pressure to this minimum point is around lO-‘.O atm at 125O’C. It should be noticed that the equilibrium amount of sulfur in melta increases remarkably at, oxygen partial pressures below IO-lo atm at 1250°C when the rock melts are rich in iron. Thoiite basalt and hawaiite are case in point-these two have a mafic composition and amounts of total iron are in the range from 13 to 14-5 per cenf as l?e,O,. Rhyodacite, on the contrary, has a salic composition having
Solubility of rmlfuriu some megnag at 1 atmosphere
623
Table 2. Sulfide- and &f&e-sulfur oontents iu tholeiite baalt (C-132) melts & 1260°C and at 2.1 per cent (SO,)t sulfur
-1% PO, 3.65 5-38 6.79 8.97 IO.66 12.20
Total S O-006 o-003 o-001 0.009 0.022 0.11
content (wt %) Sulfide to*001 <0~001
sulfate 0.006 o-003 O*OOl 0.001
a low amount of iron but with a high amount of alkalies. If we use the results illustrated in Fig. 3, and plot the total amount of dissolved sulfur against the iron content in the three melts at lo-lo atm PO, and at f250cC, we observe that the total amount of dissolved sulfur which is in the form of sulfide increases with increasing total iron. On the contrary, it was impossible to observe a significant relationship between dissolved sulfur and other components in the melts. FINCHAM and RICHARDSOET(1954) and OLSHBNSEII (1951) observed the same relation as mentioned above in the FeO-SiO, fused system at relatively low oxygen partial pressures. They explained that the anomalous enrichment of sulfur is due to the formation of troilite (FeS) in both liquid metallic and liquid oxide phases. Recent studies by B.&GLEAN (1969), and S~UMAZAEI and CLARK (1973), and by HAUCWTON and SEIINNER (1972), HAUGIHTON and ROEDER(1972) on a basaltic melt also confirmed the positive relation of the solubility of sulfur to the amount of ferrous oxide present in melts. At an oxygen partial pressure of lo- la.20atm, the solubility of sulfur in tholeiite basalt melt reached 0.1 I per cent as given in Table 2. As described by SKINNERand PEUK(1969), the solubility of sulfur in a silicate melt saturated with sulfide may be controlled by many variables. In the present study, however, we cannot discuss anything about the ~t~ation of sulfur, because we failed to observe the existence of separate iron sulfide phases in this quenched sample. We will use the solubility data obtained only above 10-l* atm PO*in later discussions. Figure 6 shows the relationship between the amount of dissolved sulfur in melts and the oxygen partial pressure at 2-l per cent (SO& in the gas phase at 1300°C. In the cases of tholeiite basalt and hawaiite, the minimum solubility is below O-001 per cent S at which the oxygen partial pressure is around lOA atm. Thus, the value of oxygen partial pressure at which the minimum solubility was observed increases with increasing ~rn~rat~e at a constant (SO& though the amount of dissolved sulfur at this minimum point is nearly the same at each temperature. It may be experimentally reasonable that at lZOO”C, the minimum point may be expected to be around 10” atm. This shift of the minimum point corresponds to the change of partial pressures of sulfur ~ompo~ds in the gas phase. Figure 7 shows the simplified relationship between partial pressures of sulfur compounds (SO,, H,S and SO,) and the oxygen partial pressure at llOO”, 1250’ and 13OO’C. As seen in Fig. 7, the partial pressure of SO, is equal to that of H,S at the oxygen
524
TA&AS~
KATSURA
and
Smamu
NAGASHIMA
Fig. 6. Relationship between the solubility of sulfur in rook melts and .Por at 1300% and at 2.1 per cent (SO,),. Symbols are the asme as those in Fig. 3.
4
6
12
8
14
-log Pa2
Fig. 7. Relationship between caloulated partial pressures of SO,, SO, and H# twdcalculated.Po, at2.1 per cent (SO,), and at 1100’ 1260’ and 1300%. Calculated pa&a3 pressuresof E&O, CO,, CO, H,, SO, S, HS, COS, CS and CS, are omitted. C&x&&d partial pressures of O,, SO, and H&3 at points Px, Pz and Pa are as follows: 1260°
1300°
PI
P,
P,
8.323
6.955
6.666
f6.987
6.634
6-644
lloo” --log PO, --log P’s& ( = --log P&S) The Psor at each P,,
is the same, and the value of -log
PO, is 1.678.
Solubility of sulfur in some magmaa at 1 atmosphere Table 3. Sulfur content
in some Hawaiian
rocks
(wt %) Total S Pole’s hair Pele’s tear TK 2101 IkiNo.2 TK 1805 TK 00018 TK 2205 TK 2201 TK 1501 C-132 C-6 C-42 c-45 C-56 C-62-1 c-72 c-91 C-92 c-97 c-100 c-105 c-111 c-112 c-117 C-118 c-120 C-128
0.018 0.016 0.002 0.003 0.010 0.003 0.003 0.002 0*006 0.006 0*002
Sulfide
Sulfate
0.018 0.016
0.010
0.006
0.003
0.036
Pele’s hair and Pele’s tear; ejected during the early stages of the 1959 eruption of Kilauea Iki, collected by Dr. H. Ikowa, University of Hawaii, Nov. 22, 1969. TK 2101; the 1960 eruption of Kilauea Iki, inside of the lava lake. Collected by T. Kataura. Iki No. 2; Core from drill hole at depth of 4 ft from the surface of the lava lake, Kilauea Iki. See a paper by MACDONALD and KATSURA (1961). TK 1806; the 1960 spatter cone of Kilauea. first few hours of the eruption, northwest of Kapoho Village. Collected by T. Katsure. TK 60018; the 1955 lava flow of Kilauea, May 26, 1965. Collected by T. Katsura near Ilewa Crater. TK 2205; the 1935 lava of the Mauna Loa, Pahoehoe lava, 2 miles easat of Puu-Huluhulu. Collected by T. Katsura. Remarks for other samples are seen in a paper by MACDONALD and KATSURA (1964)
626
526
TAKASHI
and SIIIQERIJ NAGASHIMA
KATSURA
Fig. 8. Relationship between PO, and the solubility of sulfur in tholeiite baa& (C-132) melt at 2.1 per cent (SO,), under various isothermal conditions.
partial pressure of lo- 13.~55 atm (Pz in Fig. 7) at 1250°C. This point P, moves to the point P, where the oxygen partial pressure is 10-s~sssatm when the temperature is raised to 1300°C. These oxygen partial pressures coincide with those indicating minimum solubilities with equal amounts of sulfide- and sulfate-sulfur in melts, and these facts are necessary to estimate the solubility relation at 1200°C or at 1150°C which is illustrated in Fig. 8. Figure 9 shows the relationship between -log (per cent S)meltand the concentration of (SO,)i in the gas phase at 1200°C under various oxygen partial pressures. In drawing Fig. 9, we assume the same slope of -log (per cent S),,,,/(p er cent SO,), for each isobaric line as that obtained at
I -T---1 1
I~_
r
I
/
,
QOL,,’
,,a0
$ m
.
,
/’
/‘,
’
\o
' @%,R' /'ye,,' ,60 , ,o ' I' ,"Qor
2
P --/ B
'KC ,e0 \o 3
'-4
I_
0
1_..--~-
/
2 %
3
-_J
5
( SO,);
Fig. 9. Relationship between concentration of (SO& and the solubility of sulfur in tholeiite basalt (C-132) melt at 1200% under various isobario conditions of PO . *
Solubilityof sulfurin some msgmaeat 1 atmosphere
529
126OY!, on which each amount of dissolved sulfur is plotted by using Fig. 8. Figure 9 will be used later to estimate the concentration of (SO,), in volcanic gases. The. e&nuth
of th concentration of (SO,), in volcanic gaees
The concentration of sulfur compounds in basaltic volcanic gases is now estimated in terms of (SO,), on the basis of the solubility of sulfur in basaltic rock melts. In the present discussion, we assume that a subaerially extruded basaltic magma is in equilibrium with volcanic gases at 1 atm total pressure. Many efforts have been defrayed by many investigators to estimate the extruded basaltic magmas (MINAKAMIet al., 1951; EATONand MURATA,1960; RICHTERand MURATA,1966; MURATAand RICHTER, 1966; KATSURA, 1967; SIQURGEIRSSON, 1966; SKIXNERand PECK, 1969). According to these measurements, it seems to be reliable that the temperature of the typical basaltic magma is around 1200°C at the highest. FUDALI (1965) and SHIBATA(1967) reported independently that the oxygen partial pressures of basaltic volcanic gases are around 1O-8atm at about 1200°C. KATSURA(1967) also estimated the oxygen partial pressure of Hawaiian basaltic volcanic gases being 1O-8.2atm at 1160°C. SATO and WRIGHT(1966) also estimated the oxygen fugacity of Makaopuhi lava, Kilauea, Hawaii, to be 1O-8.43atm at 12OO”C,based on the direct measurement of oxygen fugacity in holes drilled through the crust of Makaopuhi lava lake. Under these considerations, it is reasonable to conclude that the oxygen partial pressures of basaltic volcanic gases, coexisting with basaltic magmas, are of the order of IO-* atm at about 1200°C and at 1 atm total pressure. Several analytical data on the volcanic gases have been published, but the reported amounts of H,S and SO, vary widely. For example, SHEPHERD’Sdata (1938) of volcanic gases from Kilauea eruptions showed that the amount of SO, fluctuates from 8 to 30 per cent. In addition, the collected gases are considered to be frequently contaminated by air. On the basis of the thermochemical calculation, MATSUO(1960) estimated that the partial pressure of SO, in volcanic gases equilibrated with basaltic magma is 5.37 x 10e2 atm at 1100°K and at one atmosphere total pressure (the concentration of H,S is very small). MATSUO(1962) also proposed reliable values of concentrations of SO, in volcanic gases from Kilauea eruptions on the basis of the Shepherd’s analysis. According to Matsuo, corrected values of SO, are in the range from 3.7 to 13.6 per cent. SKINNERand PECK(1966) estimated the sulfur fugacity in drill-holes at Makaopuhi lava lake, Kilauea, and presented the value 10-1.5*5.0atm Ps at 1066°C based on the sulfide mineral assemblages. and ELIL-BON This corresponds to 2-20 per! cent SO, in volcanic gases. SI~VALDASON (1968) reported that the SO2 concentration in volcanic gases directly collected from the Surtsey lava lake is in the range from 164 to 6.40 per cent at 1400°K. They emphasized that the collected gas samples are hardly contaminated by impurities. FINLAYSONet aZ. (1968) summarized the volcanic research in Hawaii, and estimated the concentration of SO, in oceanic volcanic gases on the basis of their study and of early studies by HEALDet al. (1963), JAGY~ER (1940), MATSUO(1962), EATONand MURATA(1960), and SIQVALDASON and ELI~SON(1968). According to the estimation by FINLAYSONet al., the SO, concentration in Hawaiian ‘magmatic’ gases scatters
628
TAKA~HIKATSURAand SHIOERUNACASHIMA
from O-017 to 24.3 per cent. ‘Magmatic’ gases from Hawaii include gases collected from holes drilled through the solid crust, and these drill-hole gases seem to be concentrated by SO,. Recently, NORDLIE (1971) estimated the composition of the magmatic gas of Kilauea after removal of atmospheric contamination including 0,, N,, and removal of water based on the smallest amount of water found in a sample J-S. Then, he assumed that carbon has been neither added nor lost from the magmatic gas. He postulated the C/S ratio in magmatic gases, and calculated the partial pressure of equilibrated SO, in Kilauean volcanic gases at I atm total pressure and at 1100°C to be 053 atm or 0*27 atm when C/S is 05 or 15, respectively (the concentration of H,S is very small). In order to estimate the concentration of total sulfur compounds in volcanic gases expressed as (SO,)i on the basis of solubility data, the most important thing is to obtain a glass sample representing a magma equilibrated with a volcanic gas at 1 atm total pressure. MACDONALD and KATSURA (1961) focused attention on the Pele’s hair wafted from the crater of Kilauea Iki, Hawaii, erupted in November, 1959. They considered that the Pele’s hair was possibly quenched from high temperature as a glass. KATSURA (1967) also determined the liquidus temperature of the Pele’s hair under various oxygen partial pressures, and he concluded that the chemical composition of the Pele’s hair may present the liquid part of the magma extruded from the Kilauea Iki crater. As listed in Table 3, the sulfur content of the Pele’s hair is 0.018 per cent, and that of the Pele’s tear collected at the same time is 0.016 per cent S. The former consists wholly of a quenched glass, but the latter contains olivine phenocrysts which may be nuclei to form a spherical tear. The amount of olivine in the Pele’s tear was variable, but was estimated roughly to be lo-20 per cent. Thus, the content of sulfur in the glass part of the Pele’s tear is almost the same as that in the Pele’s hair. We assume with a considerable degree of certainty that the value 0.018 per cent S in Pele’s hair may represent the solubility of sulfur in the magma subaerially extruded in the 1959 eruption of Kilauea Iki. If so, the concentration of (SO,), in volcanic gases may be calculated to be 5-l per cent at 1200°C and at lo--* atm PO, with an aid of Fig. 9. This value is consistent with those directly measured by SI~VALDASON and ELISSON (1968) in Surtsey volcano. The present value agrees also with estimated average concentrations by MATSUO (1962) (6.7 per cent SO, as an average of J.16, J.13, and 5.2) and by SKINNER and PECK (1966) (6.7 per cent SO,), though there is a difference between the Kilauea Iki eruption of 1959 and other activities of summit lava lakes in extensive outgassing. The sulficr content of Hawaiian rocks According to CLARKE and WASHINGTON (1924), the average content of sulfur in igneous rocks is estimated to be O-052 per cent S, and RICKE (1960) presented the value 0.03 per cent S as the average. TAYLOR (1964) preferred the value 0.025 per cent S as the average of basaltic rocks. Recently, MOORE and FABBI (1971) determined the sulfur content of subaerially erupted oceanic basalt and of submarine erupted basalt by means of X-ray fluorescence. They give an average content of X-ray fluorescence. They give an average content of 107 ppm S, and 680 ppm S for subaerial and submarine basalts, respectively. Their analytical results show that
Solubility of sulfur in some magma
at 1 atmosphere
529
a spatter erupted August, 1969, from Mauna Ulu, Kilauea, contains O-017 per cent S, and a pumice erupted July 11, 1961, from Halemaumau, Kilauea, contains O-018 per cent S. These values are identical with that of the Pele’s hair. After careful studies, they concluded that this difference is the results of retention of sulfur in basalt quenched on the sea floor at pretty high pressures and loss of sulfur in basalt by degassing at the surface. ANDERSON(1973) also studied the sulfur content of glass inclusions in crystals from basic rocks, and found high contents of sulfur up to 0.26 per cent by weight. In contrast to these high concentrations, OZAWA et al. (1972) reported that the sulfur content in Japanese volcanic rocks is significantly low, and they obtained app~~rna~ly 0*005 per cent S as an average value for Japanese basaltic rocks. In order to check this tendency, we analyzed a large number of subaerially erupted Hawaiian volcanic rocks, and found that the sulfur content in Hawaiian basaltic rocks is almost the same as those in Japanese basaltic rocks. The detailed results will be published in the near future, but some results are given in Table 3 for the convenience of the present discussion. Samples of TK-series were collected by one of the present authors under supervision of G. A. Macdonald, University of Hawaii. Samples of C-series were collected by G. A. Maedonald, and their petro~ap~c and chemical properties have been pub~shed (IMACDONALD and KATSURA, 1964). In the usual sense, these samples are fresh except for C-45 under microscope. As listed in Table 3, typical Hawaiian tholeiite basalts contain less than 0.005 per cent S. In contrast to the sulfur content in the Pele’s hair, samples TK 2101 and Iki No. 2 contain very small amount of sulfur, as seen in Table 3. These two samples also represent the solidified magma of the Kilauea Iki eruption in 1959. Thus, it may be true as pointed out by MOOREand FABBI (1971) that almost all sulfur dissolved in a subaerially extruded magma at 1 atm total pressure in equ~b~um with coexisting volcanic gases may be degassed during the slow cooling after extrusion. Acknowledgements---Thepresent authors deeply thank Dr. BRIAE J. SKINNER,Yale University, and Dr. ALFEEDT. ANDERSON,JR., University of Chicago, for their thorough criticisms to the present study. We also thank deeply Professor GORDONA. MACDONALD, University of Hawaii, who kindly permitted the use of Hawaiian volcanic rocks, and thank Dr. H. OSAKA, Tokyo Institute of Technology, who helped us to program the digital aomputation for obtaining partial pressuresof chemical species in the gas phase. Dr. &nAO &fATSUO, Tokyo Institute of Technology, read the present manuscript and encouraged us t~oughout the study. REFERENCES ANDERSONA. T. (1972) Sulfur and chlorine contents of glass inclusions in phenocrysts and basaltic host glasses. Fluid Inclusions Res. Proc. COFFI, Vol. 3. ANnERsONA. T. (1973) Chlorine and sulfur in and out of some basaltic magmas. Submitted to Geol. Sot. Amer., May 1973 (personal communication). CLAEEEF. W. and WASHINGTON H. S. (1924) The composition of the earth’s crust. U.S. c3’eoZ. Sure. Prof. Paper 127, p. 16. DESBOROU~H G. A., AE~EESONA. T. and WEXOHTT. L. (1968) Mineralogy of sulfides from certain Hawaiian basalts, &on. i&o& 68, 636-644. EATONJ. P. and MURATAK. T. (1960) How volcctnoesgrow. Science132, 925-938. FINCHAMC. J. B. and RICHARDSON F. D. (1964) The behaviour of sulfur in silioateand &miuate melts. Pmt. Roy. Sot. London A%& 49-62. FINLAYSONJ. B., BAEEES I. L. and NAUUHTONJ. J. (1968) Developments in volcfmic gas research in Hawaii. &ophya. Monogr. l.2, 426-438.
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T~SHI
KATSURA
and SEIGERU NA~AYHIMA
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Solubility of sulfur in some magma8 at 1 atmosphere
631
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