Sulfur isotope study of Quaternary volcanic rocks from the Japanese Islands Arc

Grochimica et Cosmochimica Acta Vol. 48, pp. 1837-1848 © Pergamon Press Ltd. 1984. Printed in U.S.A.

0016-7037/84/$3.00

+ .00

Sulfur isotope study of Quaternary volcanic rocks from the Japanese Islands Arc AKIRA VEDA * and HITOSHI SAKAI** Institute for Thermal Spring Research, Okayama University, Misasa, Tottori, 682-02, Japan (Received October 13, 1983; accepted in revised/arm June 21, 1984)

Abstract-The sulfide and sulfate contents and their 034S values were determined in Quaternary volcanic rocks from the Japanese Islands Arc. The total sulfur contents are much lower (less than 40 ppm) and the 034S values are higher (+4.4 ± 2.1) than those of ocean-floor basalts (800 ± 100 ppm and +0.8 ± 0.5, respectively; MOORE and FABBI, 1971; SAKAI et al., 1982). Lateral variations of both sulfur content and 034S values were observed in the four volcanic belts in Japan. In the Northeast Japan belt, the sulfur content (30 ± 10 ppm) of the rocks in the inner zone (the Japan Sea side) is 3 to 5 times that in the outer zone (the Pacific side), although the 034S values of the two zones ar~ almost the same (+4.3 ± 1.0). The 034S values for the two belts in West Japan are on the average 2%. higher than those of East Japan. This study suggests that the primary magmas that formed the island arc volcanic rocks are initi.~~y depleted in sulfur «120 ppm) and enriched in 34S (0 34S: +5 - +7) compared to ocea~-floor tholelltlc basalts which formed at mantle under oceanic region. This indicates that the upper-mantle IS heterogeneous in sulfur content and isotope composition. INTRODUCTION THE SULFUR CONTENT of deep ocean-floor erupted basalt is 800 ± 100 ppm in average (MOORE and FABBI, 1971) and varies with chemical composition, especially the iron content (MATHEZ, 1976). A considerable fraction of sulfur in basalts exists as sulfate dissolved in glass whose relative abundance to sulfide should depend on f02 and other parameters (SAKAI et al., 1982). These field data are consistent with experiments on sulfur solubility (FINCHAM and RICHARDSON, 1954; KATSURA and NAGASHIMA, 1974). The sulfur isotope ratios of fresh ocean-floor basalts and the subaerial basalts from Hawaii and Iceland are within a narrow range (-0.5 to +I.Oroo, average +0.3%0) (KANEHIRA et al., 1973; GRINENKO et aI., 1975; PuCHELT and HUBBERTEN, 1980; SAKAI et aI., 1978, 1980, 1982). No systematic study has been carried out on the chemical and isotopic distribution of sulfur in the Quaternary volcanic rocks of Japan, which are typical of island arc volcanism. Limited studies, however, indicate that the sulfur contents are very low and variable (IWASAKI et al., 1967; OZAWA et al., 1972). The bulk sulfur isotope ratios in volcanic emanations in Japan vary widely from one volcano to another but generally are 4 to 5%0 higher than the bulk sulfur in ocean-floor basalt (e.g. SAKAI and MATSUBAYA, 1977; MATSUBAYA et al., 1975). The differences in the sulfur chemistry and isotope ratios between the ocean-floor basalts and the islands arc volcanic rocks must reflect the differences of the source material and/or the evolutionary environments

* Present address: Departments of Physics and of Geology and Geophysics, University of Calgary, Calgary, Alberta, Canada T2N IN4. ** Present address: Ocean Research Institute, Tokyo University, Minami-dai 1-15-1, Nakano-ku, Tokyo, 164, Japan. Offprint requests to H. Sakai.

for the magmas at these tectonically different sites. Thus, in the present study, a systematic investigation of the chemical and isotopic distribution of sulfur in the Quaternary volcanic rocks of Japan was carried out to gain further insight into their genesis. The Quaternary volcanoes of Japanese Islands are distributed in five volcanic belts (Fig. I). The rocks are petrographically and petrochemically divided into four rock series; tholeiitic, high-alumina, alkaline, and calc-alkaline (KUNO, 1960, 1966). The first three rock series form in order from the Pacific to the Japan Sea side and the calc-alkaline rocks occur in each zone. The tholeiitic and high-alumina basalt zones of the Northeast Japan are called the Nasu and Chokai zones, respectively. Euhedral and subhedral plagioclase phenocrysts with dark-colored glass inclusions containing lightcolored glass globules are found in these rocks. Most inclusions are nearly spherical and range in diameter from I to 50 ,.,.. They consist of two immiscible silicate liquids. Silicate liquid immiscibility in igneous rocks was first reported by ROEDDER and WEIBLEN (1970) in Apollo II lunar mare basalts. FuJII et al. (1980) also described liquid immiscibility in a number of volcanic rocks from Japan. Seventy-two rock samples collected from the four major volcanic belts of Honshu and Kyushu were analyzed for their bulk sulfur contents, sulfate/sulfide ratios and 034S values. In addition, the sulfur contents in glass inclusions in plagioclase phenocrysts of some of these rocks were also analyzed by an electron probe microanalyzer (EPMA) to estimate the sulfur contents of magma prior to extrusion. This paper summarizes the results and discusses the characteristic behaviour of sulfur and its isotopes in island arc volcanism. SAMPLES Brief descriptions of the samples with reference to the volcanoes are given below and in Tables I to 4. Whereas

1837

1838

A. Ueda and H. Sakai

Arc

r-+-=-=---

Northeast

Japan

Southwest Japan

71 72

I zu-Mariana Ryukyu

Arc

Fla. I. The Quaternary volcanoes in Japan. Each circle corresponds to a volcano. The solid circles show sample locality. Numbers in this figure correspond to those in Tables I, 3 and 4. Solid and broken lines show the volcanic fronts and Chokai zone, respectively. SI: Satsuma-Iwojima. only a few samples were taken from most volcanoes, more than 10 samples were taken from Akita-Komagatake and Hakone to study variations within one volcano. In order to investigate variations of sulfur abundance and isotope composition within a lava flow, samples were taken at different depths from a 9.3 m thick unit of Ninotaki lava flows at Chokai volcano. Three samples were also taken from a bread-crust bomb at Akita-Komagatake volcano to check for chemical and isotopic consistency (Table 2). Glass inclusions from two rock samples were analyzed for major elements and sulfur content (Table 7). Similar determinations were made on an olivine basalt sample from Kilauea Iki, Hawaii, for comparison.

seconds were repeated 5 to 7 times on each spot and averaged. The uncertainty in the measurement of sulfur content was ± 10% in most cases but it exceeded ±30% for glass with less than 200 ppm S. The details of the technique will be published elsewhere (A. UEDA and H. SAKAI, in preparation).

ANALYTICAL PROCEDURES

(I) Except for two basanites (Samples KT and MU770928, Southwest Japan), the total sulfur contents are less than 40 ppm, much lower than those of ocean-floor basalts (700 to 1500 ppm; MOORE and FABBI, 1971). (2) The average 534S value of the bulk sulfur is +4.7 ± 2.0'1'00, indicating a considerable enrichment of 34S as compared to the oceanic basalts (-0.5 to + 1.0%", SAKAI et al., 1978, 1980, 1982). (3) The sulfur content of rocks from a volcano is uniform within ±5 ppm but the average varies from 9 ppm at the Akita-Komagatake volcano to 25 ppm S at the Chokai volcanic system. The sulfur isotope ratio as well as the sulfur content were found to be uniform within a single unit of lava flow and a volcanic bomb. (4) The two basanites and three alkali olivine basalts (Samples JB-I, OKI and TK) have much higher sulfur contents but lower 534S values (+2.6 ± 1.4%,,) than the other rocks studied. (5) Sulfate commonly exists in the studied volcanic rocks and often exceeds the sulfide content. The 534S values of sulfate generally are higher than those of the coexisting sulfide. (6) Pyrrhotite and magnetite were often found in the glass inclusions in the Japanese volcanic rocks. The glass inclusions in euhedral olivine of the Kilauea Iki sample consist of skeletal plagioclase with frequent occurrences of pyrrhotite and magnetite.

Powdered rock samples were heated to 280°C under vacuum with Kiba-reagent (dehydrated phosphoric acid containing Sn 2+; KIBA et al., 1955). Sulfate and sulfide were released, respectively, as S02 and H 2S. The H 2S was oxidized to S02 by reaction with CU20 at 900°C. The quantities and 534S values were measured for both S02 samples, one from sulfate and the other from sulfide. For the details of the procedures, see UEDA and SAKAI (1983). The uncertainty in the measurement of sulfur content was ±5% of the obtained value in most cases. The sulfur isotope ratios are reported in permil deviation from Canon Diablo troilite and have a precision of±0.3%" (±II1). The sulfur content of glass inclusions in silicate phenocrysts was analyzed by a Nihon Electric Co. EPMA, model JXA5A, with an accelerating potential difference of 15 Kvand a specimen current of 0.02 IJ.A on MgO. The use of pyrite as a sulfur standard gave higher concentrations and larger uncertainties than those found by other methods. Therefore, four standard basalt glasses, with sulfur contents ranging from 100 to 1500 ppm S as determined by Kiba-reagent, were used as standards. The standards and sample glasses were alternately analyzed with an electron beam of 2 to 40 IJ. in diameter. The specimen was continuously moved with a motor (10 IJ./min) to avoid volatilization of sulfur and sodium from the glass during analyses. Counts over 40

RESULTS The data are presented in Tables I through 4 and plotted in Fig. 2. Table 5 compares the data with those from volcanic rocks in other parts of the world. The following features are noted:

Volcanic rock S isotopes

1839

Table 1 Sulfur analyses of the volcanic rocks from Akita-Komagatake and Hakone volcanoes No.

2

4

8

10 11 12 13

Sample

No. Akita-Komagatake AUX Xenolith in 1970's lava anhydri te beari ng 91904 1970's lava, Medake cone hyp aug andesite 1970's bomb (middel part) 723-2 hyp aug andesi te 91904 Medake cone, 01 hyp aug basalt 72701 Onamedake summi t, hyp aug 01 basalt 80101 Katakuradake 1ava at l300m aug 01 basalt 80102 Katakuradake 1ava at 1250m aug 01 basalt Katakuradake lava at 1200m 80104 aug 01 basalt 72901 Odake dykes, lower part hyp andes i te Odake summi t, 01 aug 91603 hyp andes ite 92203 Odake lava, caldera wall 01 aug hyp andesite 80106 Odake 1ava at 900 m, 01 aug hyp andes i te 80109 Odake 1ava, Tazawa Hill aug hyp bas alt

834S (0/ 00 )

S (ppmS)

Oescri ption S2-

SO 2-

Total

s2-

6100

470

6570

+2.8

4

14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

4

+3.1

13 +1.6

21

15

+10.7

Si0

2

Total

(wU)

+2.9

84.5

+4.4

58.4

+4.1

58.4

10

50.0 +4.8

51. 2

+4.2

-0.2 +2.5

g

4

13

12

25

4

13

+5.0 9

12

o

+4.2

13

+8.7

6

+7.7

10

+2.3

4

11

-0.5

12

12

+0.5

3 4

Average*

57.1 67.2

+0.1

57.8

+1.5

71.0

+4.5

56.7

+1.8

+1.8

+0.1

+1.2 0.0

50.1

+8.6

+8.6

52.6

8

3

+5.7 +0.5

+1.9

4

14

o

55.0

+4.5

Average* Adjacent volcano to Aki ta-Komagatake 72601 Akakurasawa lava, auto1ith rich ,01 hyp andesite #11-3 Akakurasawa lava, autolith rich, aug hyp andesite 73101 Nyutosan lava, 01 aug hyp andesite, weakly altered 92406 Sankakuyama lava, aug hyp andesite, weakly altered Hakone 53103 So-unzan cone aug hyp andesite 31203 Byobuyama, VS-5, aug hyp dacite 21306 Hiryu Fall, VS-3, aug hyp andes ite 62801 Hakone Schrine, VS-l hyp aug andes i te 53010 Hakone Pass, OS-2, aug hyp andes i te 60113 Vugawara, OS-2, aug hyp andesite 60114 Vugawara, OS-2, aug hyp andesite 60118 Vugawara, OS-2, 01 aug hyp basalt 60209 North of Mazuru, OS-2 aug hyp andesi te 53003 Nagao Pass, OS-l, hyp aug 01 basalt 53004 Otome Tunnel, OS-l, aug 01 basalt, weakly altered

SO 2-

+5.7 +2.3

63.4

+2.3

~amp1es

are listed from top to bottom in order of increasing age of eruption. The AkitaKomagatake volcano consists of a somma and central cones. The rocks are lavas and pyroclastic rocks of tholeiitic basalt to andesite compositions. However, the lava flow and bombs that erupted in 1970 from one of the central cones are gradational between tholeiitic and calc-alkaline rock series (Vagi et al., 1972). This lava contains xenoliths (Sample AUX) which are composed of tridymite, clinopyroxene, glass and anhydrite (Vagi et al., 1972). Pyrrhotite was also found in the xenolith. The Hakone volcano consists of double sommas of 12 km in diameter and central cones. The sommas are of basaltic to andesite compositions of tholeiitic rock series, whereas the central cones are calc-alkaline rocks (Kuno, 1950). Silica contents in this table are after Kawano and Aoki (1960), Vagi et a1. (1972) and Fujimaki (1975). *: Samples AUX, 72901 and 53004 excluded

DISCUSSION

Sulfur-depletion and 34S-enrichment in Japanese volcanic rocks The sulfur contents of subaerial volcanic rocks range from 55 to 3000 ppm, averaging 300 ppm, according to RICKE (1960) and SCHNEIDER (1973). Alkaline rocks usually have higher sulfur contents

(RICKE, 1960). The majority of these data are from European Tertiary volcanoes of continental eruption. The Japanese volcanic rocks contain considerably less sulfur than continental subaerial volcanic rocks. Two interpretations are possible for the low sulfur content and 34S-enrichment in Japanese volcanic rocks; these features are due to (A) sulfur loss and isotope fractionation during the evolution of magmas that originally had sulfur contents and b34S values

A. Ueda and H. Sakai

1840 Table 2

The two alternatives are now discussed.

Variation of the content and the isotope ratio of sulfur within a lava flow at Chokai Volcano and within a volcanic bomb at Akita-Komagatake Volcano. S (ppm S) Sample No.

Height from bottom(m) S2-

SO~-

6"S (0/00) Total

S2-

SO~-

+4.8 +3.6 +3.4 +3.8 +3.5

+7.0 +10.1 +9.8 +14.3 +12.4

+5.8 +4.7 +4.1 +5.2 +4.6

Lava

703-12 703-13 703-15 703-17 730-19

7.5 7.3 4.3 1.8 0.5

10 21 21 18 18

10 4 3 3

20 25 24 21 21

703-20

-

3

Total

24

2

26

+3.0

+15.2

+4.0

Volcanic bomb 723-1 rim 723-2 middl e 723-3 core

13 15 11

5 6 7

18 21 18

+0.4 +1.6 +0.7

+5.3 +10.7 +10.8

+1.9 +4.1 +4.7

919-4

-

-

13

lava

(A) The sulfur isotope ratios of a magma would be altered if sulfur was partially removed as gaseous sulfur compounds and/or metal sulfide. (A)-] Effects 01sulfur loss by degassing. The chemical composition of gaseous sulfur in equilibrium with basaltic magma is controlled by temperature, 102' water content and pressure. The temperature versus 102 relationship estimated for natural basaltic and dacitic magmas are plotted in Fig. 3, in which S03/H2S and S02/H2S equal concentration boundaries for the vapor phase associated with the magmas are also shown. The thermodynamic data for the calculation of these equal concentration boundaries were taken from BARIN and KNACKE (1973). All the gases were assumed to be ideal and the mole fractions of H 20 (XH20 ) were chosen as 1.0 for wet magma and 0.1 for dry magma. Significant sulfur degassing occurs during shallow submarine and subaerial eruptions at depths shallower than 200 m below sea level (MOORE and FABBI, 1971; MOORE and SCHILLING, 1973). Figure 3 shows that if sulfur degassing occurs at pressures near 20 atm from wet magma, H 2S and S02 occur in equal quantities in the vapor phase. However, water is deficient in basaltic rocks (DELANEY et al., 1978) and

+4.4

The 2 m thick layer at the top and the 0.3 m thick bottom layer of lava flow at Chokai are scoriaceous and reddish-brown in color due to autoxidation during cooling. The intermediate zone between these two layers is dense and gray. The rock is hornblende-bearin9 olivine augite hypersthene andesite with hypocrystall ine groundmass. No. 703-2 is a dense part from another unit underlying just below the above lava flow. The vesicularity of the volcanic bomb at Akita-Komagatake increases up to abput 50 percent from the outermost rim to the core. The groundmass is very glassy. The rock is augite hypersthene andesite. No. 919-4 is a specimen collected from a lava flow erupted during the same activity as the bomb.

similar to those of ocean-floor basalts, or (B) the source magmas for the island arcs differ from those associated with ocean-floor basalts.

Table 3 Sulfur content and isotope abundances of the volcanic rocks from Nasu and Chokai zones in the Northeast Japan belt 8345 (0/00) Si0 5 (ppm 5) Sample 2 Oescri pt ion No. No. 2 2 SO 2- Total (wU) SO 2- Total 5 5 4 4 Nasu zone 53.1 3 3 Osoreyama, Kamafuse lava 0 T-12 29 01 aug hyp andesite 65.6 3 ST-9 Osoreyama, Kitaguni lava 30 aug hyp dacite +4.4 63.5 13 Towada, welded pumice fall 10 31 9 aug hyp andesite +10.0 54.7 6 Iwate, dyke, 01 aug 02M 32 hyp andesite +5.9 3 Funagata. Kurohanayama 1ava 2 33 17 pig bronz aug 01 basalt +4.3 Funagata. Izumidake. 01 34 22 aug hyp andes i te +4.3 Bandai. summi t. aug BT 35 hyp andes i te 51.3 +3.6 4 Takahara. Hi rano-shi nden 57 36 pig aug 01 basalt

-------------------------------------------------------------------------+4.8

Average*

37 3B 39 40 41 42 43 44 45 46

Chokai zone Iwaki. cognate inc1usi on 64 01 hyp aug andes i te Iwaki. northeast valley 65 aug hyp andes i te Iwaki. volcanic block 66 hyp aug andes i te Iwaki, south of Iwaki. ho 6B aug hyp andes ite Iwaki. central dome. 01 ho 72 qtz aU9 hyp andesite Chokai. Ninotaki. Nabemori 80901 ho aug hyp andes i te 703-15 Chokai. Nakanosawa 1ava ho hyp aug andesite Chokai. Central cone lava B0703 aug hyp andes i te Chokai. Minomata lava 50107 01 aug hyp andesite Chokai. Teshirazawa lava 80719 ho 01 aug hyp andes i te

6

18

24

23

11

34

+4.7 +0.2

+7.1

9

4

+2.5

55.B

+3.6

56.1

10

33

+3.2

+9.2

+5.0

56.9

31

36

+5.1

+6.6

+6.3

62.2

14

34

+3.0

+10.4

+6.1

21

3

24

+3.4

+9.B

+4.1

22

4

26

+3.5

8

11

19

+5.0

22

+3.5

23

20

15

+3.5 +14.1

+10.4 +3.5

------------------ ---- -------------- -- ------------- -- ----- - -- -- ----------Average*

Silica content are from Kawano et al. (1961). * : Sample 02M and 50107 excluded

54.9

24

+4.4

58.6

Volcanic rock S isotopes

1841

Table 4 Sulfur analyses of the volcanic rocks from Izu-Mariana, Southwest Japan and Ryukyu Arc belts No.

47 48 49 50 51 52 53

Sample No.

Izu-Mariana SA740Fuji, 1707 erupt i on 62903 ejecta, Hoei J8-2 Oshima, Mihara, JGS standard, aug basalt Hachi jo- ji rna, post ca 1dera 6l8-Cl aug hyp andes i te 6l4-C Hachi jo- jima, Higashiyama dyke, aphyl ic andesite Hachi jo- jima, pre-caldera 6ll-Cl aphyl ic basalt 6 Nishinoshima, 1973's lava andesite KN740Chichi-jima, boninite 501

S2-

SO 24

Total

9

4

13

-0.4

9

+5.3

54 55 56 57 58 59 60 61 62 63

S2-

SO 24

65 66 67 68 69 70 71

72

Ryukyu Arc 52706 Aso, Nakadake cone. aug hyp ho andesite Aso, Kishimadake cone, hyp 52708 aug 01 andesite 52705 Aso, Sakanashi, aug rhyol ite. weakly altered 52704 Aso, Sai shi -gahara. pre-Aso lava, aug hyp andesite Aso, Iwato shri ne, pre-Aso 52715 1ava aug hyp andesi te Kr-1l7 Kuroshima. aug hyp andesite JH Kuchino-Erabujima, 01 aug hyp andes i te TK Karatsu, Takashima. 01 a1ka 1i basal t* JB-l Nagasaki, Sasebo. JGS standard, aug 01 basalt*

2

(wt%)

53.5

8

17

25

+5.8

57.3

15

33

+4.7

55.8

10

12

22

+2.7

47.2

16

3

19

+4.5

9

+5.6

19

+3.0

0

2

+8.0

+8.0

+7.7

+7.7

+5.2

+5.2

+7.4

+7.4

+6.0

+6.0

+7.0 0 0

7

0

2

0

4

2

4 9

+6.5

203

38

241

+0.6

+1.1

+0.7

24

13

37

+0.4

+4.4

+1.9

240

182

422

+2.4

+2.1

+2.3

Average** 64

Total

Si0

18

Average Southwest Japan DS-l Dai sen, Karasugasen, hyp bi ot ho andesite DS-4 Daisen, Sannosawa lava ho andesite DS-6 Daisen, Kinmon, aug hyp bi ot ho andesite A Dai sen, Ninosawa. aug hyp bi ot ho andesite C Daisen, Ninosawa lava ho aug hyp bi ot andesite S8-2 Sanbe, Shogaku lava ho bi ot andesite S8-4 Sanbe, Muronouchi lava hyp biot andesite MUnOOkayama, Tsuyama, Oyama 928 basanite* OKI Oki-Dogo. 01 alkali basalt* KT Hamada. Nagahama nepheline basalt*

34 8 S (0/00)

S (ppm S)

Descri pt ion

+6.8 g

+18.0

6

+13.1

0 0

6 3

6

20

27

+5.1

+9.5

+8.3

4

9

13

+5.1

+2.0

+3.1

59

9

68

+7.3

+7.0

3

21

+6.6

+7.3

30

+4.0

13

+4.0

52.2

----------------------------------------------------------------------Average***

29

+6.3

Silica contents are from Isshiki (1963), Ando et al. (1974) and Ando (1981). * : alkaline rocks ** : alkaline rocks excluded 34 *** : high 8 S values from Aso Volcano excluded

therefore. magma may be assumed to be dry in most natural conditions. In this case, the predominant sulfur gas should be S02 over the entire range of 102 encountered in natural basaltic magma (GERLACH and NORDlLE, 1975). The isotope fractionation between S02 and magma is then determined by the relative abundance of sulfate and sulfide which in turn is controlled by the 102, temperature and the chemical composition of the magma. According to KATSURA and NAGASHIMA

(1974), the sulfate/sulfide ratio in basaltic melt is about unity on the S03/H2S equal concentration boundary at 1250°C, I atm, but rapidly decreases with decreasing/02 (ca. 1/8 atl02 = 10- 8 .97 atm; KAT· SURA and NAGASHIMA, 1974). The experimental data of KATSURA and NAGASHIMA (1974) may not apply directly to natural basaltic magma. Further, the quantitative relationship between the sulfate/sulfide ratio and magmatic conditions requires more detailed studies. SAKAI et at. (1982) demonstrated that the

1842

A. Veda and H. Sakai

o

60

.....

50

Southwest Japan (Sw)

•

Ryukyu Arc (RY)

v

High 6 34 S rock (I'll)

+

Alkaline rock (Al)

:E

Cl. Cl.

40

III

30 20 I'll

10 0 0

50

+5

+10

EAST JAPAN

40

o

Akita-Komagatake

x

Hakone (HK)

•

Nasu zone

6

Chokai zone (CH)

a

Izu-Mariana (1M)

:E Cl. Cl.

+20

+15

(AK)

(NA)

III

-2

+15

FIG. 2. Sulfur content versus /) 34S value for Quaternary volcanic rocks of Japan. Field bounded by solid lines show two volcanoes (AK and HK), two volcanic zones (NA and CH) in Northeast Japan, three volcanic belts (1M, SW and RY), alkaline rocks (AL) and volcanic rocks of unusually high /) 34S values (HI) in Ryukyu belt. Symbols surrounded by small circles show /) 34S values of Satsuma-lwojima volcanic rocks in West Japan as determined by VEDA and SAKAI (1982).

subaerial basalts of the Kilauea east rift zone are depleted in 34S relative to the submarine equivalents owing to a preferential loss of 34S02 from magma with an average sulfate/sulfide ratio of 1/4. They suggested that the isotope effect may be reversed and the extruded, degassed magma may be enriched in the heavy sulfur, if it had a higher f02 and thus a higher sulfate/sulfide ratio. Figure 3 strongly suggests that the f02 values of the basaltic and acidic magmas are always lower than that of S03/H2S equal concentration boundary. This implies that sulfate/sulfide ratio in natural magmas is always less than unity (KATSURA and NAGASHIMA, 1974). In fact, oceanfloor basalts have sulfate/sulfide ratio of 0.02 to 0.5 (SAKAI et al.. 1978, 1982; GRINENKO et al., 1975; PuCHELT and HUBBERTEN, 1980; SAKAI et aI., in preparation). Therefore, the natural basaltic and acidic magmas would not generally have a sufficiently high f02 value for the light isotope to be enriched in escaping S02 compared to dissolved sulfur in the melt. (A)-2 Effect of sulfur loss by sulfide precipitation. Separation of sulfide minerals from magma would

also alter 034 S value of the magma. Under reducing condition of magma, sulfide separation cannot cause more than ± I %0 variation in 034S because of the small isotope fractionation between sulfide minerals separated and sulfide sulfur in the magma. In contrast, if sulfate sulfur exists in significant amounts in the magma, precipitation of metal sulfides would remove isotopically light sulfur before eruption because Osol- > OSulfide. In the Quaternary volcanic rocks from Japan, pyrrhotite has been observed in dacite rocks from Satsuma-Iwojima (UEDA and ITAYA, 1981), Sakurajima in the Ryukyu belt, and Okiura in the Northeast Japan belt (our unpublished data), implying that these magmas were saturated with respect to sulfide before eruption. The solubility of sulfur in magma has been determined to be 800 - 1500 ppm in basaltic melt under natural condition (KATSURA and NAGASHIMA, 1974; HAUGHTON et al., 1974; MOORE and FABBI, 1971; MATHEZ, 1976) and 50 - 100 ppm in dacite melt (KATSURA and NAGASHIMA, 1974; UEDA and ITAYA, 1981). The 034S values of sulfide commonly observed in differentiated mafic and granitic rocks either remain

Volcanic rock S isotopes

1843

Table 5 Summary of analytical results of sulfur in volcanic rocks from the Japanese Islands and the world.

~~~~a ~O~~ne

Total S (ppm)

S2-/S0~-

Ave. Range

Ave. Range

[~~:~. v~~~:;:es**

8 27 11 5 22 28

Japan Island Arc (average}***

14

Northeast Japan [

Izu-Mariana Southwest Japan

Ryukyu Arc

Ocean-floor basalts Hawaii [~~~~:~~~f Iceland subaerial Mariana [island arc trou9 h Greece Santor1ni andesite Germany tholeiitic basalt alkali olivine basalt alka 1; -ri ch basalt USA Triassic igneous rocks

f

870 700 93 107 60 820

-

Japan granite (~~~~~~~;es:~~:~s 270 630

* . **.

Ave. : Ref. :

h25 9~36

~33 2~9 6~58 5~68

h68 640~1570 670~840

39 35 30

~176

1 1 1 1 1 1

0023

+4.4

2.1

62

1

+0.3 +0.7 -0.7 -0.5 -

0.4 0.1 0.2 0.6

2 3 3 4 5 5 6 7 7 7 8 9 9

-

-

-

-

-

20~19DO

19 9 17 7 9 10

0.9

1.2

2~70 2~7 2~26

20~18DO

2.2 0.9 2.1 1.9

1.8

-

-

Ref.

S.D.

15.4 3.7 7.7

-

~100

Ave.

1.0 004 +4.2 2.2 0.2~7 +4.4 2.3 005 +3.0 0.4 002 +6.8 2.9 0023 +12.9 2.0 0.h7 +7.0

-

~235

580~1080

6 3.S (0/00) No.

-

-

-

+4.2 -0.3 +1.3 +3.1 +0.1

2.0 1.0 0.3 1.0 0.4

22 6 12 3 4 4 11 9 10 10 31

+4.3 -3.9

2.5 3.9

18 23

-

--

Numbers of analyses. These rocks are taken from somma and central cones from Aso and SatsumaIwojima and have high 6 34 $ values. The data from the Satsuma-Iwojima are taken from Ueda and Sakai (1982). Others volcanoes: volcanic rocks in Ryukyu Arc belt except for the high 63'S-rocks. The average value excluded those rocks that show extreme deviation. Average t S.D.: standard deViation. Reference, 1) This work, 2) Sakai et a1. (1978), Grinenko et a1. (1975), Puchelt and Hubberten (1980), Kanehira et a1. (1973), H. Sakai, D.J. Des Marais, A. Ueda and J.G. Moore (in preparation), 3) Sakai et al. (1982) 4) Sakai et a1. (1980).5) Garcia et a1. (1979).6) Hubberten et a1. (1975) 7) Schneider (1970), 8) Smitherin9ale and Jensen (1963). 9) Sasaki and Ishihara (1979).

constant or decrease with increasing fractional crystallization of magmas (I roo decrease at Skaergaard; SASAKI, 1969a; constant at Muskox; SASAKI, I969b). We measured sulfur isotope ratios of rocks from the Ibaragi granitic body, Japan, where the petrology exhibits a differentiation sequence from quartz diorite to adamellite (TAINOSHO, 1971) with corresponding changes in oxygen isotope compositions (MATSUHISA et aI., 1973). The sulfur content and 034 S values decrease from 140 to 10 ppm S and from -0.5 to -1.6%0, respectively, with increasing degree of fractional crystallization. So far, it is not observed that metal sulfide precipitation produced the large enrichment of 34S in differentiated magma during fractional crystallization. This implies that most sulfur in these mafic and granitic rocks is predominantly sulfidesulfur. In contrast, natural basaltic rocks contain a significant amount of sulfate-sulfur dissolved in glass (SAKAI et al.. 1978, 1982; GRINENKO et al.. 1975; this work). In this work, two representative volcanoes in Japan were investigated in detail for their sulfur contents and isotope ratios in relation with the chemistry and the stratigraphy of the rocks (Table 1). No satisfactory correlations among these parameters were observed in either of these volcanoes. If the sulfur content of the magma before its extrusion is similar to sulfide-saturated ocean-floor basalts (800 to 1500 ppm; MOORE and FABBI, 1971) and most sulfur in these sulfide-saturated magma is lost by sulfide precipitation, the chemical and isotope features of the volcanic rocks from Japan (less than 40 ppm and +4 - +6 roo) seem to be explained.

In summary, the low sulfur content and 34S_en_ richment in the Japanese volcanic rocks compared to ocean-floor basalts cannot be explained by simple degassing of sulfur species from magma, but can be the result of extensive sulfide precipitation prior to the degassing. (B) The second interpretation is that the source magmas for the Japanese volcanic rocks are deficient in sulfur and enriched in 34S; the upper-mantle is heterogeneous in chemistry and isotope composition of sulfur. If we take the loss of sulfur by degassing and the consequent isotopic fractionation during eruption of the Japanese volcanic rocks to be similar to those found at Kilauea volcano (ca. 75% and +0.9%0; SAKAI et al.. 1982), the sulfur content and the 034 S values of the source magma of Japanese volcanic rocks should be less than about 160 ppm and about 5 to 7%0, respectively, except for the basanites. Of the two models presented above, we consider the second one, the mantle heterogeneity, to be more likely than the first one for the following reasons. (l) GARCIA et al. (1979) reported the sulfur content of a submarine basalt glass of the Mariana back arc to average 60 ppm S, whereas the ocean-floor basalts in the Mariana Trough had 800 ppm S. In the present study, a similar pair of samples from the Yap and Mariana Trenches were also analyzed. The results are shown in Table 6. Samples DI-Ib and Dl-l were collected from a slope on the oceanic side of the Yap trench and are considered to be ocean-floor basalts. Sample DI-Ib has a sulfur content and a 034 S value similar to other ocean-floor basalts, whereas sample

A. Veda and H. Sakai

1844

Temperature 800

900

1000

1100

(Oe) 1200

1300

O.----....---...-----.--~--.....,

(at m)

MH

1000

~

- 5

/5031

H 25

1 1000

N

~502/H25

0

20

Cl

1

0

..... - 10

(20

at m)

X H20 X

H20

= 1 = 0.1

- 1 5 "'-"oL.

.....

FIG. 3. Temperature versus 102 diagram of natural basaltic and acidic rocks and equal concentration boundaries of H 2S-S02 and H 2S-S0 3 at I atm (solid line) and 1000 atm (broken line) in wet magma (XH20 = I). This figure also shows equal concentration boundaries of H 2S-S02 at 20 atm in wet (solid line) and dry conditions (XH,o = 0.1). The latter is the same as the I atm line for wet condition. Closed circles, triangles and the shaded area show the estimated T - 102 conditions in the Akita-Komagatake andesite formed during 1970 (ARAMAKI and KATSURA, 1973), Satsuma-Iwojima dacite (VEDA and ITAYA, 1981) and Hawaiian basalt (ANDERSON and WRIGHT, 1972), respectively. The open circle is an experimental point at I atm by KATSURA and NAGASHIMA (1974) in which the sulfate/sulfide ratio in basaltic melt is 1/8. Fields bounded by solid lines are T - 102 conditions of natural basaltic and acidic rocks (CARMICHAEL el al., 1974; HAGGERTY, 1976). FMQ and MH are Fayalite-Magnetite-Quartz and Magnetite-Hematite buffers, respectively (EUGSTER and WONES, 1962).

D I-I is significantly depleted in sulfur and enriched in 34S. In contrast, sample D 1-5-8, collected at a slope of the Mariana island are, has a sulfur content and isotope ratio similar to the volcanic rocks of Japan. These data partially support the conclusion by GARCIA et al. (1979), although we have no reason to reject the data on D 1- I. (2) Some glass inclusions from the Japanese volcanic rocks were analyzed for chemical compositions by EPMA to estimate the initial sulfur content in deep-seated magma. Many workers have estimated the physico-chemical conditions of host magma by chemical data on glass inclusions (ANDERSON and

WRIGHT, 1972; ANDERSON, 1976) and by heating samples under controlled conditions (ROEDDER and WEIBLEN, 1970, 1973). However, silicate melt inclusions in phenocrysts are not directly representative of trapped magmatic liquid because chemical interaction between inclusion and host crystals usually occurs after melt entrapment (ANDERSON, 1976; WATSON, 1976). The chemical compositions of glass inclusions and the whole rocks are shown in Table 7. The glass inclusions at Akita-Komagatake are depleted in CaO and Ah03 and enriched in FeO and MgO in comparison with the bulk composition of the rock. These

Table 6

Sulfur analyses of sutlTlarine

basalts from Yap and Mariana trenches. S (p,,", S)

Sample No. ST1440 DI-lb l ) ST1430 01-1 1 ) ST1404 01-5-8a 2 )

1) 2)

Local ity Yap trench, off shore slope augite basalt. glass part pillow rim, -61000-5800 m Yap trench. off shore slope

fresh basalt, crystalline -750(»'-7250 m. Mariana trench, near s~ore slope, olivine basalt, weakl y altered.

6'"S (0/00)

52 -

SD~-

Total

S75

98

673

2

6

8

21

23

44

dredged at the ocean side from Yap trench dredged at the island arc side from Mariana trench

S20.0

+1.1

SD~+7.6

+17.9

Total +1.1 +11.8 +9.8

Volcanic rock S isotopes Table 7

Chemical composition and the sulfur contents of glass inclusions and wflole rocks. Akita-Kornaga take WR

GL

An

GL**

MnO MgO CaO Na20 K2 U

55.1 0.6 4. 9 16.0 0.4 13.0 6.7 1.2 1.6

51.3 0.3 18.9 8.0 0.2 6.5 12.8 1.2 0.8

Total

99.2

99.4

100.0

FeD*

5 (ppm)

WR: FeD*: 61**: An: Fa: 1): 2) : 3) :

B1 anket:

GL

WR

51 )112±80 2 ) (86±36) 25±18 (64±19) 34±17

58.6 0.8 16.9 6.6 0.1 4.1 6.7 3.5 1.8

64.5 1.0 16.3 2.7 0.1 0.9 5.3 3.8 4.5

gg .2

99.1

25 1 ) 122±692 ) (l27±17) 49±9 (37±12 )

GL

F0 87

An49

88

51.2 0.9 19.4 9.4 0.1 4.4 11.1 2.4 0.3

5i02 Ti02 A1203

Hawaii

Chokai WR

48.7 2.8 12.7 12.1 0.1 9.5 10.1 2.4 0.6

55.0 3.0 16.9 6.2 0.1 3.2 11.8 2.4 0.8

99.0

99.4

361) 770±180 2 ) (790±70) 480±160 (420±110)

89±26 3 )

whole rock, GL: glass inclusion total iron content estimated initial composition by the assumption that 50% plagioclase was precipitated from the trapped glass. Anorthite mole percent in plagioclase forsterite mole percent in olivine determined by a Kiba-reagent method determined by EPMA with a forcused beam determined by EPMA with a deforcused beam

determined the same point by EPMA with a deforcused beam.

differences may be due to interaction of glass with host plagioclase. WATSON (1976) showed that during interaction with host minerals, the chemical composition of glass inclusion decreases in the component constituting the host mineral. He calculated an original composition by assuming that 7 to 26% of the plagioclase was precipitated from the trapped glass. We also estimated the original composition of glass at Akita-Komagatake by the actual composition of the host plagioclase which is homogeneous in its anorthite molar composition (AnsS-An90)' The result shown in Table 7 is quite similar to the bulk composition. This indicates that the plagioclase grew from the basaltic liquid. Therefore, the glass inclusion at Akita-Komagatake may be representative of the early magmatic liquid although the chemical composition of the melt was changed from the initial value. In the case of Chokai, the estimated original composition of the trapped glass did not agree so well with the bulk composition. So far, we cannot critically discuss whether the glass inclusion is co-magmatic with the rock or it formed by mixing with other magma (e.g. ANDERSON, 1976). However, the inclusions must have formed from deep-seated magma beneath the Japan Islands. As shown in Table 7, the sulfur contents of the glass inclusions are less than 120 ppm S. Pyrrhotite crystals are seen to exist in some glass inclusions. But the grain size is usually less than 1 J.l. Therefore, the pyrrhotite does not affect significantly the bulk sulfur content in the glass inclusion. In fact, the sulfur content in glass containing pyrrhotite as determined by' EPMA with a defocussed beam (approx. 30 J.l) is less than 120 ppm S (Table 7). In contrast, the Hawaiian subaerial basalts contain 36 to 200 ppm S,

1845

whereas submarine basalts from the same volcano have 700 ± 150 ppm S (MOORE and FABBI, 1971; SAKAI et aI., 1982), suggesting a significant loss of sulfur from basaltic magma during surface eruption. In order to test the validity of our EPMA technique, glass inclusions in olivine phenocrysts of the Kapoho 1960 lava, Kilauea, one of the most sulfur-deficient rocks (36 ppm S; SAKAI et al., 1982), were analyzed for sulfur by the EPMA technique. The glass inclusions contain 400 to 800 ppm S, similar to the submarine basalt glass analyzed by the Kiba reagent method (Table 7). These results strongly support the view that the sulfur content of the deep-seated magmas beneath the Japanese Islands is less than 120 ppm S; the magmas are significantly depleted in sulfur compared to those for the ocean-floor basalts. Admittedly, however, the number of analyses is limited and more data are clearly needed to confirm the present results. 034S of volcanic rocks in the world

Data from other volcanic rocks in the world are given in Table 5. In the Hellenic island arc, Greece, HUBBERTEN et al. (1975) reported 034 S values of +4.0 ± 2.9%0 for calc-alkaline andesites from the Nea Kameni volcano. In the Taupo volcanic zone, New Zealand, the 034S values for discharge from geothermal areas have been determined or estimated to be +4.8%0 for H 2S and + 15%0 for total sulfur at Wairakei (KUSAKABE, 1974) and +2 to +3 for total sulfur at Ketetahi and White Island (GIGGENBACH, 1977). We found a dredge sample from the Mariana Island Arc to have a 034 S value of +9.8%0. In contrast, continental igneous rocks generally have 034 S values of - 2 to +2%0 close to the meteoritic sulfur (SHIMA et aI., 1963; SMITHERINGALE and JENSEN, 1963; THODE et aI., 1962; SASAKI, 1969a; SCHNEIDER, 1970). Whereas, some igneous rocks in continental region have positive 034S values (Muskox mafic rocks: +3 to +70/'00; SASAKI, 1969b; Canadian granitic intrusives: +6 to +30roo; SHIMA et aI., 1963). These authors attributed the higher 034 S values to either contamination of the magma by secondary sulfur (SHIMA et al., 1963; SASAKI, 1969b) or mantle heterogeneity (SASAKI, 1969b). Although further studies should be done on continental rocks, it is likely that the 034 S values in magma beneath the island arcs are more positive than oceanic and continental magmas. Comparison with granitic rocks of Japan

Figure 2 indicates that the 034 S values of the volcanic rocks in the Ryukyu Arc and the southwest Japan (West Japan) are 2 to 3%0 greater than those of other volcanic zones (East Japan). SASAKI and ISHIHARA (1979) also noted that the Cretaceous granitic rocks of the magnetite series in San-in belt (Southwest Japan) exhibit 2 to 3%0 higher 034S values than those of the Kitakami-Abukuma belt of East Japan. The average 034 S values obtained by them for

1846

A. Ueda and H. Sakai

the two groups of granitic rocks are +2.2 for the Kitakami belt and +5.1 %0 for the San-in belt, in good agreement with the present results for the Quaternary volcanic rocks. The magnetite series granitic rocks are thought to have been derived from the upper mantle and/or the lower crust without significant contribution of sedimentary rocks to the magma (ISHIHARA, 1977). The present results together with the 034S values of the magnetite series granites strongly indicate that the sulfur isotope ratios of the deep-crust and upper-mantle beneath the west region of the Japanese Islands are 2 to 3%0 greater than the east region and the heterogeneity could have existed since Cretaceous age. On the other hand, the granitic rocks of the ilmenite series that intruded into the metamorphic terranes of the Japanese Islands invariably have significantly negative to slightly positive 034S values (-10.9 to +2.2%0; SASAKI and ISHIHARA, 1979). The negative 034S values were attributed to assimilation of 32S-rich upper-Paleozoic sedimentary rocks underlying the Japanese Islands. It should be noted that none of the Quaternary volcanic rocks studied have a negative 034S value similar to the granitic rocks of the ilmenite series; no significant contamination by sedimentary rocks occurred during and after the generation of the volcanic rocks. Volcanic rocks with high 034S values

Unusually high 034S values (+11 - +18%0) are observed in rock samples from Aso volcano (52705 and 52706, Table 4) and Satsuma-Iwojima, a volcanic island in the Ryukyu Arc belt (Fig. 2). These rocks came from the sommas and central cones of the two giant calderas (about 20 km in diameter). Volcanic rocks older than the sommas, however, have similar 034S values to the other rocks studied (Table 4 and Fig. 2). These results imply a close connection between the caldera formation and 34S-enrichment in the magmas. So far, the 034S values of basement rocks beneath the Ryukyu Arc belt have not been systematically investigated. SASAKI and ISHIHARA (1979) reported a range from -21.5 to -0.4%0 for composite samples of the Shimanto sedimentary rocks which are widely distributed in the southern part of West Japan. In addition, Miocene granitic rocks (ilmenite series) which intruded into these sedimentary rocks also have negative 034 S values (SASAKI and ISHIHARA, 1979). Therefore, these pre-Tertiary basement rocks cannot be the source materials of the heavy sulfur. On the other hand, the Quaternary volcanic rocks of Japan are mostly underlain by Tertiary submarine volcanogenetic formation. Such marine formations are often contaminated by sea water sulfate (SAKAI and MATSUBAYA, 1974) and could be the most likely candidate for the source rocks of heavy sulfur in Aso and Satsuma-Iwojima volcanoes. However, geologic evidence to support the presence of such submarine

formations underneath these volcanoes is lacking and this problem is still open for further study. Alkaline rocks

A nepheline basalt and a basanite (Table 4) sample stand out as having much higher sulfur contents and lower 034S values than the other volcanic rocks (Table 4). The alkali olivine basalts from Oki-Dogo and Takashima, which contain ultramafic xenoliths derived from mantle, also have relatively high sulfur contents and similarly low 034S values. The 034S values of five alkaline rocks studied (+2.6 ± 1.4%0) are in fair accord with those found for alkali olivine basalt in Germany (+ 1.3%0; SCHNEIDER, 1970) and are close to the ocean-floor basalt values. These facts strongly suggest that the alkaline rocks were derived from a different source than other Quaternary volcanic rocks. The depth of generation of alkaline magma is generally considered to be greater than tholeiitic and high-alumina basalt magmas (GREEN and RINGWOOD, 1967; KUSHIRO, 1973). Alternately, ANDERSON (1982a,b) proposed a model that tholeiitic and alkalic basalt magmas are derived from two different source regions of the mantle which are depleted and enriched, respectively, in incompatible elements such as large ion lithophiles and volatiles. The present results are consistent with the view that tholeiitic and alkali basalts come from two different sources, but they do not answer the question as to their formation depths. CONCLUSIONS

(I) The Quaternary tholeiitic and calc-alkaline volcanic rocks from the Japanese Islands Arc are deficient in sulfur and enriched in 34S compared to ocean-floor basalts. Several lines of evidence were presented which strongly suggest that the difference is due to heterogeneity in the chemistry and isotope composition of sulfur in the mantle beneath the island arc and ocean regions; the deep-seated magmas beneath the Japan Islands are initially depleted in sulfur (less than 120 ppm) and enriched in 34S (0 34S: +5 to +7%0) compared to those for ocean-floor tholeiitic basalts (700 - 1500 ppm, -0.5 - + 1.00/'00). So far, it is not clear why the source of the island arc volcanics is sulfur-depleted and 34S-enriched relative to oceanic basaltic magma because no data about behaviour of sulfur during partial melting of mantle are available. (2) The 034S values of the rocks from West Japan are 2 to 3%0 higher than those of East Japan. These features are similar to those observed for Cretaceous granitic rocks in Japan. (3) Alkaline rocks have relatively higher sulfur contents and lower 034S values than other rock series, supporting the view that the alkaline rocks are derived from a different source than the tholeiitic volcanic rocks. The similarity of the 034S values in the alkalic rocks to ocean-floor basalts and alkali rocks of other

Volcanic rock S isotopes

areas of the world suggest that their upper mantle source is uniformly distributed. Acknowledgements-We thank R. H. Krouse for his critical reading of this manuscript. We also thank H. Muraoka, T. Yoshida, K. Watanabe and Y. Matsuhisa for their kind advice on the field work and sample collection. Thanks are also due to K. Ono, K. Fujioka, K. Aoki, N. Isshiki, K. Shibahashi, J. Hirabayashi, K. Nakamura, K. Tazaki, Y. Nakamura, S. Togashi, K. Ishikawa, H. Fujimaki, A. Fujinawa and M. Usui for providing samples. We also thank E. Takahashi for assisting us in the use of the electron probe microanalyzer. REFERENCES ANDERSON A. T. and WRIGHT T. L. (1972) Phenocrysts and glass inclusions and their bearing on oxidation and mixing of basaltic magmas, Kilauea Volcano, Hawaii. Amer. Mineral. 37, 188-216. ANDERSON A. T. (1976) Magma mixing: Petrological process and volcanological tool. J. Volcanol. Geotherm. Res. 1, 3-33. ANDERSON D. L. (1982a) Isotopic evolution of the mantle: the role of magma mixing. Earth Planet. Sci. Lett. 57, 112. ANDERSON D. L. (1982b) Isotopic evolution of the mantle: a model. Earth Planet. Sci. Lett. 57, 13-24. ANDO A. (1981) Chemical compositions of JGS standard rocks, JG-I, JB-I, JB-2, JA-I and JR-1. Annual Meeting Geochem. Soc. Japan Abst. 3C17, pp. 357-358 (in Japanese). ANDO A., KURASAWA H., OHMORI T. and TAKEDA E. (1974) 1974 compilation of data on the GSJ geochemical reference samples JG-I granodiorite and JB-I basalt. Geochem. J.8, 175-192. ARAMAKI S. and KATSURA T. (1973) Petrology and liquidus temperature of the magma of the 1970 eruption of AkitaKomagatake Volcano, Northeast Japan. J. Japan Assoc. Mineral. Petrol. Econ. Geol. 68, 101-124. BARIN I. and KNACKEO. (1973) Thermochemical Properties of Inorganic Substances. Springer-Verlag. CARMICHAEL I. S. E., TURNER F. J. and VERHOOGEN J. (1974) Igneous Petrology. McGraw-Hill. DELANEY J. R., MUENOW D. W. and HRAHAM D. G. (1978) Abundance and distribution of water, carbon and sulfur in the glassy rims of submarine basalts. Geochim. Cosmochim. Acta 42,581-594. EUGSTER H. P. and WONES D. R. (1962) Stability relations of the ferruginous biotite, annite. J. Petrol. 3, 82-96. FINCHAM C. J. B. and RICHARDSON F. D. (1954) The behavior of sulphur in silicate and aluminosilicate melts. Proc. Roy. Soc. London Ser. A. 223, 40-62. FuJII T., KUSHIRO I., NAKAMURA Y. and KOYAGUCHI T. (1980) A note on silicate liquid immiscibility in Japanese volcanic rocks. J. Geol. Soc. Japan 86, 409-412. FuJIMAKI H. (1975) Rare earth elements in volcanic rocks from Hakone and Northern Izu Peninsula, Japan. J. Fac. Sci. Univ. Tokyo Sec. II 19, 81-93. GARCIA M. 0., LIU N. W. K. and MUENOW D. W. (1979) Volatiles in submarine volcanic rocks from the Mariana Island arc and trough. Geochim. Cosmochim. Acta 43, 305-312. GERLACH T. M. and NORDLIE B. E. (1975) The C-H-O-S gaseous system, Part I. Composition limits and trends in basaltic cases. A mer. J. Sci. 275, 353-376. GIGGENBACH W. F. (1977) The isotopic composition of sulphur in sedimentary rocks bordering the Taupo volcanic zone. New Zealand Dept. Sci. Indust. Res. Bull. No. 218. pp.57-64. GREEN D. H. and RINGWOOD A. E. (1967) The genesis of basaltic magma. Contrib. Mineral. Petrol. 15, 103-190.

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GRINENKO V. A., DMITRIEV L. V., MIGDISOV A. A. and SHARASKIN A. Y. (1975) Sulfur contents and isotope compositions for igneous and metamorphic rocks from Mid-Ocean Ridges. Geochem. Internat. pp. 132-137. HAGGERTY S. E. (1976) Opaque mineral oxides in terrestrial igneous rocks. In Oxide Minerals (ed. D. RUMBLE, III), Vol. 3, Chap. 8, pp. 101-300. Mineral. Soc. Amer. HAUGHTON D. R., ROEDER P. L. and SKINNER B. J. (1974) Solubility of sulfur in mafic magmas. Econ. Geol. 69, 451-467. HUBBERTEN H. W., NIELSEN H. and PuCHELT H. (1975) The enrichment of 34S in the solfataras of the Nea Kameni volcano, Santorini Archipelago, Greece. Chern. Geol. 16, 197-205. ISHIHARA S. (1977) The magnetite-series and ilmenite-series granitic rocks. Mining Geol. 27, 293-305. ISSHIKI N. (1963) Petrology of Hachijo-jima volcano group, seven Izu Islands, Japan. J. Fac. Sci. Univ. Tokyo. Ser. II. 15,91-134. IWASAKI I., OZAWA T. and ARIKAWA Y. (1967) Sulfur content in volcanic rocks from Japan. Annual Meeting Geochem. Soc. Japan, Abst. IB-03, pp. 30-31 (in Japanese) KANEHIRA K., YUI S., SAKAI H. and SASAKI A. (1973) Sulphide globules and sulphur isotope ratios in the abyssal tholeiite from the Mid-Atlantic Ridge near 30 0 N latitude. Geochem. J. 7, 89-96. KATSURA T. and NAGASHIMA S. (1974) Solubility of sulfur in some magmas at I atmosphere. Geochim. Cosmochim. Acta 38, 517-531. KAWANO Y. and AOKI K. (1960) Petrology of Hachimantai and surrounding volcanoes, Northeast Japan. Sci. Rept. Tohoku Univ. Ser. III 6, 409-429. KAWANO Y., YAGI K. and AOKI K. (1961) Petrography and petrochemistry of the volcanic rocks of Quaternary volcanoes of Northeastern Japan. Sci. Rept. Tohoku Univ. Ser. II. pp. 1-45. KJBA T., TAKAGI T., YOSHIMURA Y. and KJSHI I. (1955) Tin(II)-strong phosphoric acid. A new reagent for the determination of sulfate by reduction to hydrogen sulfide. Bull. Chern. Soc. Japan 28, 641-644. KUNO H. (1950) Petrology of Hakone and the adjacent areas, Japan. Bull. Geol. Soc. Amer. 61, 957-1019. KUNO H. (1960) High alumina basalt. J. Petrol. 1, 121145. KUNO H. (1966) Lateral variation of basaltic magma type across continental margins and island arcs. Bull. Volcanol. 29, 195-222. KUSAKABE M. (1974) Sulphur isotopic variation in nature; 10. Oxygen and sulphur isotope study of Wairakei geothermal well discharges. New Zealand J. Sci. 17, 183191. KUSHIRO I. (1973) Origin of some magmas in oceanic and circumoceanic regions. Tectonophys. 17,211-222. MATHEZ E. A. (1976) Sulfur solubility and magmatic sulfides in submarine basalt glass. J. Geophys. Res. 81, 42694276. MATSUBAYA 0., UEDA A., KUSAKABE M., MATSUHISA Y., SAKAI H. and SASAKI A. (1975) An isotope study of the volcanoes and the hot spring in Satsuma-Iwojima. and some areas in Kyushu. Bull. Geol. Surv. Japan 26, 375392 (in Japanese with English abstract). MATSUHISA Y., TAINOSHO Y. and MATSUBAYA O. (1973) Oxygen isotope study of the Ibaragi granitic complex, Osaka, southwest Japan. Geochem. J. 7,201-213. MOORE J. G. and FABBI B. P. (1971) An estimate of the juvenile sulfur content of basalt. Contrib. Mineral. Petrol. 33, 118-127. MOORE J. G. and SCHILLING J. G. (1973) Vesicles, water and sulfur in Reykjanes ridge basalts. Contrib. Mineral. Petrol. 41, 105-118. OZAWA T., YOSHIDA M., NAGASHIMA S., IWASAKI I. and ARIKAWA Y. (1972) The sulfur content of igneous rocks

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