Terrestrial Ferro-Manganese Nodules Formed in Limestone Areas of The

Geochemical Journal, Vol. 17, pp. 41 to 49, 1983

Terrestrial ferro-manganese nodules formed in limestone areas of the Ryukyu Islands Differential thermal analysis, infrared absorption and thermal transformation of mineral phases

KIY0sHI KANESHIMA and HATSUO TAIRA

Department of Chemistry, College of Sciences, University of the Ryukyus, Nishihara-cho Okinawa 903-01, Japan

(Received January 16, 1982: Accepted October 8, 1982)

Physical studies such as differential thermal analysis, thermal gravity analysis, infrared absorption and thermal transformation of mineral phase have been carried out for terrestrial ferromanganese nodules formed in limestone areas of the Ryukyu Islands. The differential thermal analysis data indicate that they are grouped into four different types regardless of indistinct patterns of X-ray diffractometry. The first group shows endothermic peaks at near 120, 320 and 560°C. The second goup is close to the first group except showing a quite enhanced endothermic peak at 320°C. The third type of nodules shows one more additional endothermic peak at near 800°C. The final fourth group shows only two endothermic peaks at near 120 and 560°C. The X-ray diffraction patterns for heated samples at various temperatures indicate that magnetite is formed at temperatures over 700°C. Braunite also seems to be formed at the same tem perature range but it disappears at 1,000°C. The mineral composition of the manganese nodules has been also discussed by the study of infrared absorption patterns with particular reference to quartz, goethite, amorphous state of ferrihydrite and artifitially formed silica gel.

INTRODUCTION (16± 2) X 104 y for a nodule to attain a maximum size of 2cm in diamter (TAIRA et al., 1979). The occurrence and the distribution of ter There are quite a few reports on differential restrial ferro-manganese nodules which are thermal analysis (DTA) and infrared (IR) ab formed in reddish soils on the Ryukyu Islands sorption studies for oceanic manganese nodules, are largely concerned with Riukiu Limestone and which show either a discrete endothermic peak its weathering processes. The nodules well con in the 120-240° C temperature range or some centrate minor elements such as Ni, Cu, Pb and weak endothermic peaks at temperatures higher Co as oceanic nodules, but Pb and Cd are more than 3000C (SHIMA and OKADA, 1968; OKADA concentrated in terrestrial ferro-manganese nod and SHIMA, 1969; OKADA et al., 1972). There ules than in oceanic nodules (KANESHIMAand are, however, few studies on terrestrial ferro IREI, 1968; OOSHIROand NOHARA 1976; NOHA manganese nodules. RA and OOSHIRO,1978; TAIRA et al., 1981). This paper deals with differential thermal The study on the mineral composition of the analysis and infrared absorption for terrestrial nodules shows only a peak for quartz and the ferro-manganese nodules together with thermal most part of the nodules remains as amorphous transformation of the mineral phase. state for manganese and iron minerals (KANE

SHIMAand IREI, 1968). Recent detailed study EXPERIMENTAL clarifies the existence of very weak signals from todorokite and birnessit (NOHARAand OosHIRO, Samples 1978). The growth rate of the nodules is found Fifteen samples were collected from Okina to be about 61±9mm/106y and it takes about wa, Kume, Ie and Miyako Islands. The samples

41 42 K. KANESHIMA and H. TAIRA

and locations are: Oyakebaru Sashiki-son (S-1), average physical states of nodules, ten to fifteen Sobe Yomitan-son (Y-1,3), Ganeko Ginowan individual nodules collected from the same area shi (Gi-4), Sakiyama Nakijin-son (N-6B) and were compositely ground rather than taking a Bise Motobu-cho (BI-1) on Okinawa Island. The single nodule. The DTA measurements were others were collected from Ie Island (1-1,4), carried out by the use of a Rigaku Denki Ther Kume Island (K-1) and Miyako Island (M-3,5, moflex TG-DSC. The sample of 0.25-0.35g 8,9). The sampling locations are shown in Fig. was taken for the analysis with the use of stan 1. dard aluminum oxide. The DTA data were The maximum size of the nodules used was obtained with 500µV, 10°C/min in air free 1.5 cm in diameter and most of the others varied circumstance. The results are shown in Fig. 2. from 0.5 to 1.0 cm in diameter. Color is dark For some limited samples, thermal gravity brown. The major and minor chemical com changes were measured and the results are ponents of the samples used in this work have shown in Fig. 3. The DTA data on goethite already been reported in the previous paper and quartz samples from North Korea are shown (TAIRA et al., 1981). in Fig. 4 for reference.

Measurements Thermal transformation of mineral phases DTA measurement For the study of the Thermal transformation of mineral phase

125°20' E

24°50' 128°00'E I P, N-6B M-8~~ rl--n29PT M-9 i e I-1, M-3,5 BI-1-' v Miyako Is.

126°50'E K-1 Okinawa Is. ® :Riukiu Limestone

26°20 N 25030'N

Kyushu Kume is. °o S 0°O0'N

Y-1

GI-4 P Ryukyu Is, 6 S-1 Kume I s 4 0 '. 6PO Tai wan Okinawa Is.

0 10 20km Miyako is. --f 25°30'N 0 5km 125000'E 130°00'E

Fig. 1. Sampling locations for terrestrial ferro-manganese nodules.

0 Terrestrial ferro-manganese nodules 43

of the nodules at various temperatures was also measured by the use of X-ray powder method. The air dried powder samples were heated at 0 110, 600, 700, 800, 900 and 1,000'C for 6 hours. The X-ray diffraction patterns were 5 taken for the above samples by a Rigaku Denki a Geigerflex 2011 B with Ni filter, Cu Ka-ray, X10 30KV, l0mA, 2°/min scan speed and 20mm/ 15 o

min chart speed. The results are shown in 20 S-1 Fig. 5. 100 300 500 700 900 Temp (°C) Infrared absorption For the study of identification of the existence of hydroxides of Fig. 3. Thermogravimetry patterns for some terrestrial manganese and iron in the nodules, the infrared ferro-manganese nodules. absorption spectra with KBr crystal were ob tained on a Hitachi EP1-52 type spectrometer. are four types of endothermic peak patterns in The results are shown in Fig. 6. DTA curves for terrestrial manganese nodules, depending upon the sampling locations. Endo thermic peaks at 123-135°C and at 552-573°C RESULTS AND DISCUSSION temperature ranges are common thoughout all DTA patterns As seen from Fig. 2, there samples, whereas the modes and appearances of the endothermic peaks at 270-325°C and 765 815°C temperature ranges are characteristic for each sample. This introduces a method to S-1 classify nodules into 4 types. 130 317 558 Y-1 The first group in Fig. 2 (Type I) includes 125 320 555 K-1 Type I 315 the nodules collected from both Okinawa Island 123 558 Gi-4 (S-l, Y-1, Gi-4 and N-6B) and Kume Island (K 315 555 x.125 N-6B 1). The DTA pattern of this type shows 3 130 325 565 endothermic peaks at temperatures 123-130,

Y 565 M-3 315-325 and 555-565°C. The second type 13 ~ 0 ,3 M-5 (Type II), which is found in Miyako Island, Type II C. 560 _125 M-8 ~3 323 560 M-9 130 560

325

I-1C Goethite

123 315 552 765 BI-1A

Type III 125 270 573 815 BI-1E 808 1 5 329 570 BI-1B 808 Quartz 1"25 ' 325, 570

--f- I-4

Type IV 558

550 100 200 300 400 500 600 700 800 ~ 5 15 0C 100 200 300 400 500 600 700 800 900 Temperature C)

Fig. 2. Differential thermal analysis patterns for ter Fig. 4. Differential thermal analysis patterns for goe restrial ferro-manganese nodules. thite and quartz.

0 44 K. KANESHIMA and H. TAIRA

also has 3 endothermic peaks as in Type I but show an endothermic peak near 360°C as seen gives endothermic peaks at 323-325°C tem in Fig. 4. d) OKADA(1959) reported the occur perature range stronger than that in Type I. The rence of an endothermic peak at 350°C in a third type which was collected from Bise, Moto goethite which was collected from Hayaseno bu Peninsula, Okinawa Island, exhibits one more mineral deposits. The occurrence of the peak extra peak at 765-815°C temperature range may most probably be due to hydrous iron besides the 3 peaks in Types I and II. This type oxides in reddish soils which have been in of nodule has CaCO3 content higher than any corporated in manganese nodules in accretion other types of nodules (TAIRA et al., 1981). processes. The final fourth type nodule exhibits only two The third endothermic peak at the 552 endothermic peaks at 123-135°C and 550 573°C temperature range may be originated 558°C temperature ranges. This type of nodules from the phase transition from a-quartz to are formed only in le Island. a-quartz, since quartz transition takes place at Besides the DTA study, thermal gravity about 570°C as seen in Fig. 4. The other types changes (TG) were also measured for some of transitions from Mn02 to Mn2O3 or from limited samples. The results are shown in Fig. 3. Figure 3 indicates that the rate of weight loss M M between room temperature and 120'C is fairly Q M M M B M rapid and it becomes slow and monotonic up 1000°C BH HQ B MB to 1,000°C. The rate of TG changes seems to 900°C

correspond to the individual endothermic peak 800°C S-1 I. patterns. 700°C On the basis of these results on DTA and TG measurements, the sharp endothermic peak at 600°C the 123-135°C temperature range is considered 110°C Q M M M to be due to the existence of H2O(-) and H20 I B M M M A 1000°C (+) which are originated from adsorbed and/or Q Q adheared water not only on manganese minerals 900°C

but also on the others such as iron and clay 800°C minerals. This may be corroborated by the Y-3 700°C results obtained from DTA study on oceanic I manganese nodules (OKADA and SHIMA,1969; 600°C

OKADAet al., 1972) and on the other terrestrial 110°C manganese ores (ITo, 1963; HARIYA and TERA Q M B M Q M M DA, 1965). 1000°C

The endothermic peak near 325°C, which is i Q w.n 900°C very weak or even does not appear from oceanic manganese nodules, can be observed in all ter +w+SwM+.~ 800°C I-4 ,N+hwF.J restrial manganese nodules except for one from 700°C le Island. Irrespective of the existence of 600°C goethite, the peak near 325°C may probably be due to the existence of hydrous iron oxides in wn.~w..~4 110°C 20 30 40 terrestrial manganese nodules. This is supposed 50 60 (°) from the following experimental observations: Diffraction angle(26) a) Iron content is high (17.6% as Fe203). b) Fig. 5. X-ray diffraction patterns for some selected TG curve gives a considerable change in mass samples with heat treatment (Q; Quartz, M; Magnetite, reduction. c) DTA data of a goethite sample B; Braunite, H; Hematite). Terrestrial ferro-manganese nodules 45

Fe203 to Fe304 may also be complexed with Thermal phase transformation For the above quartz transition, because TG decreases study on the thermal phase transformation of at about 570'C and the rate of the mass reduc terrestrial ferro-manganese nodules, the samples tion can almost be neglected at temperatures were heated for 6 hours at 110, 600, 700, 800, higher than 5 70° C. 900 and 1,000'C. Then X-ray diffraction pat The endothermic peak at the 765-815°C terns were taken for the above samples. The range, which can be observed in samples col results are shown in Fig. 5. It is clear from Fig, lected from Bise Motobu-cho, implies the 5 that the samples seem to be steady for heating existence of CaCO3, CaO content being as high up to 600'C. At 700"C, however, a peak for as 1.71-1.92% compared with the other samples magnetite with d value (distance of the crystal of 0.5517o CaO content on the average (TAIRA lattice) of 2.53A (20 = 35.5°) seems to appear. et al., 1981). In order to assertain this, gases Secondary peaks at d values of 2.97A (20 = given off from manganese nodules at 710-770°C 30.1 °) become enhanced at temperatures higher were analyzed by gaschromatography, as shown than 800'C. The peaks corresponding to d values in Fig. 7. Figure 7 clearly indicates the ex of 1.71A (20 = 53.3°) and 1.62A (20 = 56.8') istence of CO2 gas which was released by the for magnetite appear at 900'C for all samples. A decomposition of CaCO3 in manganese nodules. peak for d value of 2.72A (20 = 32.9°) which may show the formation of braunite at 7000C and the peak height becomes maximum at 900° C. The peak, however, disappears at 1,000°C. 2 3 5 7 10 20 Fm OKADAet al. (1972) reported the same type of studies on oceanic manganese nodules, which

Goethit showed the formation of bixbyite, hematite, cubic and tetragonal (Fe, Mn)203, respectively.

/ M-9 , There are also many other studies on phase ~A transformations resulted from heat treatment BI-1Cr. 0 (HARIYA and TERADA, 1965; ITO, 1961 a, b, 1963; OKADA,1959; OKADAet al., 1972; SHIMA et al., 1975). Even though there are many similarities between oceanic and terrestrial Silica Gel manganese nodules, there are some differences 0 in the phase transformation pattern. For ex N N ample, X-ray powder patterns in Fig. 5 show Ferrihydrite a0 -~(G -2A) that magnetite is formed in most samples at mH E .

710`C 7251C 7401C 7701C 790 N1 K A N1 N1 N1

ho lip Y-3C

COt C% COt COi

l i

3600 2000 1600 1200 800 400 Retention Time(Arbitrary) Wave Number (cm-1) Fig. 7. Gaschromatogramsfor CO2 gasfraction released Fig. 6. Infrared absorption spectra for terrestrial man from heated manganesenodule of BI-ICsample (column; ganese nodules, silica gel, goethite and ferrihydrite. Porapak T, Tem.;50°C, N2 gasflow; 25 m1/min.). 46 K. KANESHIMA and H. TAIRA

In O O N N '0 O\ tO N to H M .-K r-t -4 .--I r1 N

M 00 N t 00 O 00 N N v) en 00 r a~ N en It NN.-q Oh 00 to M M .d O d' M N N cV fV w

00 O 0 O 0 O r-t h M O 00 N ri M It r1 a w M M 00 In N N r N O, ~} to d' t N to 110 M O, O r-1 r-1 00 00 01 N t0 d; M b N N N N N r-f A w N 0 O O O ~0 to to O N 0 ton M M M N

cd ~ 00 110 mr C,4 O 0 ON ri O N M ON ON 00 tn %0 v) 00 %0 to d' It M h M fV fV N .-i ri .-i .--i .--4 cn H N

r-. M N d' d OM N %0 -4 O It H O d' .--I ri M V') O n"1 O O N N -4 tn 00 -4 oo-4 N tn°q r to M 1-4 O 00 r %0 %D V) Ict It ^r w ab d N N fV d .--i

O O O 0 v) 0000000 NO a . -4 O It N N 0) ~ ,NNcnNtn00 t+) N 0, N N t~ O M d •-t .a 00 to N rti to r~ 0O M 00 to N M t to M N 1-4 .--i-4 0 N 00 00 I It) . . . M N C4 N N N N 1-4 -4 1-4 r-i .--4 -4 -4 -4 q O O

to O 0 O 0 0 O M to 0 v) 0 0 0 0 0 0 14 1-4 ri N 0 [. to N N N N N M 0) h ts CL a en C4 %0 M O\ 00 O N M 01Mt N O --4 v) t M O M MO'.'.ON0 .. O N M O,N tnerm e4-4 00 00 00 r W) 1 M tI) . d M en N cV N N N N CV ~4 14 N 0 01 N 00 O 00 to 00 '%0 O 00 0 .-4 O N N .-a O ti r-t Op 0) O ~ N rV O N O 00 N 00 0, d• M to to 00 rti . N to r-1 e . N r ..r Oi N try M 01 t to M 00 00 /0 %0 tn I* M t~ b ~. d M m N (V CV N cV 14 -4 14 -4 O N C N

t` 00 O O, M O O N N O, N N NW N000M r4 rti M t -4 rti r-1 .--~ .--~ N .-1 . o m 0 O ~ O 01 r-. v -to to .-a t O t~ ~O M 0, 00 N .--i O M v to r .--t M C14 a .-1 00 .--4 qt 00 to N 00 N M O N to N .--t 00 t %OW to eF le, 't M >+ b d. m N C N N N N -4 -4 0

t N O, 0, 0 t--~ N N N N .M-i O0%tn %0 000ti)O N N N M e . -4 0p 0 ra

00 N %0 tn %0 tn N to t 00 to 00 -4 01 M O~ 00 00 -4 00 tn 01 N t0 M 0, t~ 00 to .-4-4 00 00 V] b d' d M et . M c+1N N N N N tV r -4 r~ r; .~i

Ayh Terrestrial ferro-manganese nodules 47 temperatures higher than 700°C except for some sorption bands at 1,600, 1000 and 400-600cm-' samples which may form hematite. The hema are common throughout all samples. The absorp tite peak can be seen in samples with low Mn/ tion band at 900cm ' which appears like a Fe values whereas it is not clear in samples with shoulder rinked with a large absorption band Mn/Fe values of 1.1-1.3. around 1,000cm-' , is clearer than that in oceanic As seen from Fig. 5 and Table 1, a peak with manganese nodules (SHIMA et al., 1975). d value of 2.72A which seems to be revealed by For reference studies, a silica gel, a fer braunite also appears at 700° C. This peak posi rihydrite which was collected from northern tion is very close to the mean peak position of part of Okinawa Island and a goethite obtained bixbyite, partridgite and hematite. Morevoer, from North Korea were selected, and their IR the characteristic peaks with d values of 3.49A absorption spectra were taken as seen in Fig. 6. (20 = 25.5°) and 2.14A (20 = 42.2°) for braun It is not clear from the figure that the iron forms ite, however, are not observed either in Fig. 5 or goethite in terrestrial manganese nodules, in Table 1. It is, therefore, difficult to conclude because absorption band patterns are quite that the peak with d value of 2.72A is due to the different from those of manganese nodules. The formation of braunite alone. It is, however, weak absorption bands at 900 cm-', however, estimated with the following experimental may imply the existence of some amounts of observations that at least some of braunite must goethite. be formed at 700'C: a) Terrestrial manganese The absorption bands for ferrihydrite and nodules give Mn/Fe values lower than oceanic silica gel show a close resemblance to those of manganese nodules. b) Silica content is abnor manganese nodules giving almost all coincident mally high, 33.2%, compared with that in oceanic main absorption bands such as at 3,200, 1,600, nodules. c) Silicate minerals with high Mn 1,000 and 500 cm-'. The spectrum analogy content such as hematite, manganophyllite and between manganese nodules and ferrihydrite, penwithite are transformed from braunite at however, is greater than that between manganese 600°C. and become extinct at 1,000°C (ITO, nodules and silica gel or goethite. This indicates 1961a, b, 1963). d) Si02 becomes a solid solu that some amorphous type of ferrihydrite is tion with Mn203 of 0-40% in weight (MUAN, certainly contained in terrestrial ferroman 1959). e) Characteristic peaks for braunite with ganese nodules. d values of 1.65A (20 = 55.7°) and 1.42A (20 = Comparing the IR absorption spectra for 65.8°) are found as indicated in Table 1. terrestrial manganese nodules and oceanic ones (SHIMA and OKADA, 1968; OKADAand SHIMA, Infrared absorption Infrared absorption 1969), the absorption band patterns are very spectra were taken for terrestrial manganese much similar to each other. The absorption nodules to clarify the existence of hydrous bands at corresponding wave numbers may be oxides of manganese and iron and also to clas explained as follows: POTTER and RossMAN sify the types of nodules which could hardly (1979a, b) reported that the absorption bands be characterized by X-ray powder patterns. The at 3,500 and 1,600 cm-' found in some man IR absorption spectra are shown in Fig. 6. ganese minerals are brought from bending Figure 6 shows that IR absorption spectra vibration of H2O which is cohered and/or exhibits some differences between samples, adhered onto manganese minerals. This may although they are not so clear as in DTA mea suggest that the absorption bands near the same surements. The manganese nodules from Miya wave number as for terrestrial ferro-manganese ko Island (M-8, 9), for example, exhibit three nodules are also due to bending vibration of small absorption bands like shoulders super H20, which is analogous to that in manganese imposing on a large absorption band at 3,600 minerals. cm-' due to OH streching vibration. The ab In the study of ferrihydrite collected from 48 K. KANESHIMA and H. TAIRA

Finland, CARLSON and SCHWERTMANN(1981) chim. Acta 45,421-429. concluded that the band at 1,000cm-' is given HARIYA, Y. and TERADA, S. (1965) Abnormaly by streching vibration of Si-O bonding. They phase change by thermal on some pyrolusites. J. Jap. Assoc. Mineral. Petrol. Econ. Geol. 53, 19-25 (in found, in the study of IR absorption for Si-O-Fe Japanese). bonding, that ferrihydrite which does not con ITO, K. (1961a) Thermal transformation of Pen tain Si02 gives none of absorption around withite. J. Jap. Assoc. Mineral.Petrol. Econ. Geol. 1,000 cm -', whereas the sample which contain 46,17-25 (in Japanese) Si02 shows an apparent absorption band in the ITO,K. (1961b) Thermal transformation of Bemen 900-1,000 cm-' region. The absorption strength tite. J. Jap. Assoc. Mineral.Petrol. Econ. Geol. 46, 209-218 (in Japanese). in this region increases and the wave numbers ITO,K. (1963) Thermal transformation of Mangano shift , from 900 cm -' to 1,000 cm-' side along phyllite. J. Jap. Assoc. Mineral.Petrol Econ. Geol. with the increase in the Si02 content of fer 49, 182-188 (in Japanese). rihydrite. The results were also ascertained by KANESHIMA,K. and IREI, S. (1968) Geochemical comparing the IR absorption spectra of the study on the manganesenodules in the latteritic soil ferrihydrite sample treated with both HCl and of the Ryukyu Islands.Bull. Sci. & Eng. Div. Univ.of the Ryukyus 11, 28-44 (in Japanese). NaOH solutions. With respect to the above MUAN,A. (1959) Phaseequilibria in the systemman results, OKADA et al. (1972) reported that ganeseoxide-Si02 in air. Am. J. Sci. 257,297-315. absorption band around 500-600 cm-' in NOHARA,M. and OOSHIRO,I. (1978) Terrigenous oceanic manganese nodules, result mainly from manganese nodules, its shapes, mineralogical and silicates and MnO2 minerals. It is, therefore, geochemical characteristics. Bull. of Museum of said that absorption band near 1,000cm 1 is un OkinawaPref. No. 4, 17-30 (in Japanese). OKADA,K. (1959) Thermal study on some y-type doubtedly due to quartz taken into manganese ramsdellites. J. Jap. Assoc. Mineral. Petrol. Econ. nodules together with Mn02 . Geol. 43, 229-238 (in Japanese). Even though there are many analogies be OKADA,K. and SHIMA,M. (1969) Study on the man tween terrestrial and oceanic manganese nodules ganese nodule (II). Comparison of a manganese in the spectrum pattern of IR absorption, X nodules collected from the surface of the sea-floor ray powder diffraction and DTA curves, many with that collected from a 3 meter deep core. J. Jap. Assoc. Mineral. Petrol. Econ. Geol. 61, 41-49 (in differences are also seen from the above studies. Japanese). Terrestrial ferro-manganese nodules might have OKADA,A., MINAKUCHI,T. and SHIMA,M. (1972) been formed in an unsteady environment of the Study on the manganesenodule V. Thermal studies weathering of Riukiu Limestone, while man of the Iron-manganesephase. J. Oceanog. Soc. ganese nodules are formed on the deep sea floor Japan. 28, 39-47 (in Japanese). which is considered to be an almost steady en OOSHIRO,I. and NOHARA,M. (1976) Manganese nodules in surface reddish soil on Ryukyu Islands. vironment. This difference should be reflected Geol.News 260,16-23 (n Japanese). in the characteristics of the terrestrial manganese POTTER, R. and ROSSMAN, G. R. (1979a) The nodules. tetravalent manganese oxide: identification, hydra tion, and structural relationships by infrared spectro Acknowledgements-Weare indepted to Professor Y. scopy. Am. Miner. 64,1199-1218. KITANOfor his helpful suggestionsand critical reading POTTER, R. and ROSSMAN,G. R. (1979b) Mineral the manuscript. Wealso thank Mr. M. HIGAfor his help ogy of manganese dendrite and coatings. Am. Miner. in measuringIR absorption, and Mr. T. OOMORIfor aid 64,1219-1226. in gaschromatographicanalyses. SHIMA,M. and OKADA,A. (1968) Study on the manganese nodule(I) Manganese nodules collected from a long deep-sea core on the mid-Pacificocean REFERENCES floor. J. Jap. Assoc. Mineral. Petrol Econ Geol. 60, 47-56 (in Japanese). CARLSON,L. and SCHWERTMANN,U. (1981) Natural SHIMA,M., OKADA,A. and YABUKI,S. (1975) Study ferrihydrites in surface deposits from Finland and on Manganese nodule (IX). Infrared Absorption their association with silica. Geochem. et Cosmo Spectra of ManganeseNodules. Instit. Phys. Chem. Terrestrial ferromanganese nodules 49

Res. (Rikagaku Kenkyusho) Sci. Paper LP.C.R. 51, TAIRA,H., KITANO,Y. and KANESHIMA,K. (1981) 74-81 (in Japanese). Terrestrial ferro-manganese nodules formed in lime TAIRA,H., KITANO,Y. and KANESHIMA,K. (1979) stone areas of the Ryukyu Islands. Part I Major and Growth rate of terrestrial ferro-manganesenodules in minor constituents of terrestrial ferro-manganese the limestone area of the Ryukyu Islands. Geochem. nodules. Geochem. J. 15, 69-80. J. 13,301-305.