SHORT COMMUNICATION

MINERALOGICAL MAGAZINE, SEPTEMBER 1987, VOL. 51, PP. 463 6

An X-ray diffraction investigation of a

Marine 10 A manganate
D u R I N G recent studies on marine ferromanganese structures in transmission electron microscope
crusts from the Marius Is. region of the Western studies of marine nodules, similar to those in
Pacific Ocean one of the authors (JO) noted a terrestrial todorokite, and by the presence of
todorokite-like mineral, which, when micro- tunnel structures at higher magnification (Burns
analysed, gave unusually low totals for this mineral, and Burns, 1978).
suggesting a high degree of hydration. Micro- However, evidence that the 10 .~ phase in
analytical totals on apparently dense homogeneous nodules may be more complex than is commonly
areas of the mineral produced totals of 60-70~o, believed comes from studies such as those of Siegel
much lower than totals of 85 90~ commonly and Turner (1982) and Ostwald (1982b) that two
reported for todorokite (Burns and Burns, 1979; varieties of the mineral existed in Pacific nodules.
Ostwald, 1982a) and lower than that of vernadite At about this time the terminology 'manganite' was
70-85~ (Burns and Burns, 1979; Ostwald, 1984a). changed to 'manganate' chiefly because manganite
The microanalysis and preliminary X-ray diffrac- is a well known terrestrial mineral v-MnOOH.
tion analyses indicated that the phase was chemic- During the 1970-1980 period researchers in Bern,
ally and structurally similar to synthetic 10 A Switzerland, put forward the idea, based largely
phyllomanganate, of formula Na4Mnl~O27. on mineral synthesis, that the 10 A phase in
21H20, reported in JCPDS Card 32-1128. A nodules was essentially a naturally-occurring layer-
detailed account of the marine deposit in which the lattice structure, a phyllomanganate, with 10 A
I0 A manganate mineral occurs is in preparation. basal spacings, partially converted into the 7 A
This note concentrates on the results of some X-ray phyllomanganate birnessite and further altered
diffraction experiments, carried out because recent into the tunnel structure 7-MnOOH.
mineralogical research has suggested that the Giovanoli and Burki (1975) put forward the idea
10 A nodule phase commonly considered to be that the fibrous structures seen in nodules under the
todorokite may show considerable structural electron microscope were decomposition products
variability under heating and liquid intercala- of the 10 A manganate, and they considered that
tion (Paterson, 1981; Arrhenius and Tsai, 1981). 'todorokite' was really the alteration product of
Evidence for a 10 _~ phyllomanganate in marine the 10 A layer-lattice they termed 'buserite'. The
deposits. The mineralogy of the marine manganese 'buserite' concept aroused considerable debate and
oxides is complex and poorly understood, in part recently Giovanoli (1985) has reconsidered his
because of such features of the minerals as fine grain earlier assertions that todorokire is not a valid
size and poor crystallinity (Gtasby, 1977) but also mineral species. Todorokite is now widely accepted
because of difficulties in terminology (Ostwald, as the important Ni and Cu containing phase in
1984b). In the present context it must be recalled marine nodules and the phase producing diffrac-
that Buser and Grutter (1956) originally defined the tion peaks at about 9.8, 4.9 and 2.44 A (Burns
nodule phase 10 A manganite as the component in et al., 1983). At about the same time, however,
nodules which gave broad diffraction peaks near 10 A manganate nodule phases were reported by
10 A. Within a few years this phase was equated Arrhenius and Tsai (1981) from the East Equatorial
with todorokite by Levinson (1960), Tooms et al. Pacific, and by Chukhrov et al. (1983) from the
(1969), and Brooke and Prosser (1969), a concept Pacific. Chukhrov et al. (1983) identified three
which dominated nodule research for the last phases, buserite, asbolane (originally described by
decade (Burns and Burns, 1979). This idea was Chukhrov et al. in 1982) and mixed layer hybrid
strengthened by the observation of finely-fibrous buserite-asbolane. Further studies (Chukhrov et
464 SHORT C O M M U N I C A T I O N

al., 1984) have allowed the distinction between t w o to evaporate. The moist slide was transferred to a
types of buserite, buserite I, an unstable phyllo- diffractometer and the diffraction pattern recorded.
manganate which transforms to birnessite on X-ray diffraction was carried out on a Siemens
drying at 100 ~ and also during examination in the D500 diffractometer using Cu-K~ radiation and
vacuum of an electron microscope, and buserite II, graphite monochromator. A 0.3 ~ divergence and
which does not change its major spacing doo 1 = 0.15 ~ receiving slit were employed. Data were
9.7-9.8 on heating or dehydration. collected using 0.02 ~ two-theta step size and a
Arrhenius and Tsai (1981) distinguished between counting time of 1 sec/step over the range of 2-70 ~
todorokite, which has fixed diffraction peaks under two-theta for the intercalated manganese oxide,
heating and following intercalation with dodecyl- and 5 70~ two-theta for the original phyllo-
ammonium ions, and buserite, which contracts to manganate.
form birnessite (dool = 7 A) on heating and R e s u l t s and discussion. The X-ray experiment
expands to doo 1 = 25.6 A when intercalated with indicated:
dodecylammonium ions.
Andreev et al. (1984) in a study of Pacific Ocean 1. Heating 10 ~, phyllomanganate to 100 ~ for 4
hours results in formation of the '7 ~ ' birnessite
manganese nodules concluded that these consisted
essentially of vernadite, buserite and mixed layer structure (Fig. la, b). Collapse of the layer structure
buserite/asbolane, with the Cu and Ni being con- is irreversible. Neither dispersion in water of 0.1 M
dodecylammonium chloride for two days results in
centrated in buserite. They claimed that todorokite
did not recur in the nodules, and birnessite was very re-expansion to the '10 ~ ' structure. Dehydration
rare. via heating appears to be quite harsh and results in
These recent investigations suggest that a final permanent collapse of the layer structure.
definition of marine nodule phases has not yet been 2. Intercalation of the phyllomanganate by
achieved. dodecylammonium chloride results in a diffraction
E x p e r i m e n t a l . The phyllomanganate sample was pattern essentially identical to that obtained by
suspended on 0.1 M aqueous solution of dodecyl- Paterson, 1981 (Fig. 2a, b). The observed d-spacings
ammonium chloride for up to 65 hours. At intervals represent the 001 series consistent with the occur-
of 20, 40 and finally 65 hours aliquots of the rence of a single-layer/double-layer sequence of
suspension were removed, centrifuged and washed alkyl chains that regularly interstratify the layer
as described by Paterson (1981). The residue was in structure.
each case dispersed in water and placed on a glass 3. However, intercalation occurs more slowly than
slide from which the bulk of the liquid was allowed described by Paterson who reported complete

o
72A

m ~- ....... 3slA 24sA

I---
7
559
oo 99A

~. ~953,

~176176 2 .5o 2_9637

5~ so.5o $7.oo 63.50 70.0o
17.5s9 4.9a4 ~.6~o t..o6 t.6t4 i.464 i.343
TWO - THETA / I3 - SPACTNG
FIG. 1. (a) Powder diffraction pattern of untreated phyllomanganate. (b) Diffraction pattern of phyllomanganate
heated to 100 ~ for 4 hours.
 SHORT C O M M U N I C A T I O N 465

25aA

o
g-

o
o- 12.8A
U.-)~
)--
Z

ask
i

~ 63k 50k ~,2k

o

99~

J L Lg~k
r I ~ "1 r i i i i
~ 50
TWO - THETA / D - SPACING
FIG. 2. (a) Powder diffraction pattern of untreated phyllomanganate. (b) Diffraction pattern of phyllomanganate
intercalated with dodecylammonium chloride (after 40 hrs).

expansion after 16 hours. In our case 60 hours is The results of the heating and intercalation
not sufficient to produce complete expansion, as experiments suggest that marine 10/~ manganate is
indicated by the presence of the parent phyllo- unstable and the writers suspect that its desiccation
manganate in the XRD pattern. About 40 hours to birnessite-type minerals may account for the
appears to be the optimum time for producing the identification of such in dried ferromanganese
maximum extent of layer expansion. nodules and crusts. The numerous identifications of
4. The incomplete expansion suggests that the birnessite in marine nodules during the last two
Manus Is. 10 A phyllomanganate is generally decades (Burns and Burns, 1977) may have resulted
unstable but that it also contains domains of more from such a transformation. Terrestrial occur-
stable structure, possibly producing a hybrid- rences of the 10 /~ manganate have not been
structured mineral. Similar features were observed reported, and this is not surprising as such would
in the buserites studied by Chukhrov et al. (1984) be expected to slowly alter to birnessite during
and Andreev et aL (1984). geological time. Birnessite, like the other man-
ganese layer-lattices chalcophanite and lithio-
These results indicate that a layer-lattice man- phorite may be the end products of complex
ganese oxide occurs in ferromanganese deposits of mineral genesis mechanisms (Ostwald, 1984c).
the Pacific Ocean and confirms the earlier findings There are suggestions in the literature that
of Soviet investigators. The authors feel statements the occurrence of birnessite in marine manganese
such as those of Andreev et al. (1984) that all marine deposits may be a sign of hydrothermal activity, in
manganese oxides giving a major diffraction peak contrast to normal hydrogenous precipitations
at or near 10 A are buserite-type layer lattices is which result in nodules and crusts of layered
extreme, as manganese oxide tunnel structures with vernadite (6-MNO2) and todorokite. The deposits
major peaks in the region of 9.6-9.8 A, identified as from the Galapagos Hydrothermal Field (Corliss et
todorokite, have repeatedly been reported (Turner al., 1978) not only contain vernadite and todorokite
et al., 1982; Chukhrov et al., 1978). The writers (which may be hydrogenous components) but also
agree with Burns et al. (1985) that mineralogical a 10 A manganate very similar to the one described
identification of marine manganese oxides required in this paper, and well-crystallized birnessite.
more than just routine X-ray diffraction analysis. Lonsdale et al. (1980) also identified well-
The precise mineralogical nature of the phase crystallized birnessite (and todorokite) from the
described here requires further study, and the name region of a young submarine volcano at 8~ 48.2' N,
10 A manganate is used for convenience. No doubt 103 ~ 53.8' W, and in this case there was SEM
Soviet mineralogists would term it buserite. evidence that the birnessite was a recrystallization
466 SHORT COMMUNICATION

product of an older manganese hydroxide. Thus, (Amstutz, G. C., El Gorezy, A., Frenzel, G., Kluth, C.,
the association 10 ,~ manganate and/or birnessite Moh, G., Wauschkuhn, A., and Zimmerman, R. C., eds.)
may be a possible indication of marine hydro- 230-9. Springer-Verlag, Berlin.
thermal activity. ----Drits, L. E., Shterenberg, A. V., and Sakharov,
V. A. (1983) Izv. Akad. Nauk. SSSR Ser. Geol. 5, 91 9.
Sivtsov, A. V., Uspenskaya, T. Y., and
Acknowledgement. The authors acknowledge the technical Sakharov, V. A. (1984) Ibid. 10, 65 74.
assistance of Ms S. Bell and the support of The Broken Corliss, J. B., Lyle, M., Dymond, J., and Crane, I. T. (1978)
Hill Proprietary Company Limited. Earth Planet. Sci. Lett. 40, 12 24.
Giovanoli, R. (1985) Am. Mineral. 70, 202-4.
REFERENCES - - a n d Burki, P. (1975) Chimia, 29, 266-72.
Glasby, G. P. (ed.) (1977) Marine Manganese Deposits.
Andreev, S. I., Smetannikova, O. G., Anikeeva, L. I., Elsevier 522 pp.
Vanshtein, B. G., Frank-Kamenetskii, V. A., and Levinson, A. A. (1960) Am. Mineral, 45, 802-7.
Kaurov, V. O. (1984) Geokhim. Donnykh Obraz. Lonsdale, P., Burns, V. M., and Fisk, M. (1980) J. Geol. 88,
Mirovogo Okeana 1984, 14-29. 611-18.
Arrhenius, G. O., and Tsai, A. G. (1981) Scripps Inst. Ostwald, J. (1982a) BHP Tech. Bull. 26(1), 52-4.
Oceanography, SIO 81-28, 1-19. - - ( 1 9 8 2 b ) Mineral Mag. 46, 253-6.
Brooke, J. N., and Prosser, A. P. (1969) Trans. Inst. Mining - - (1984a) In Applied Mineralogy (Park, W. C., Hausen,
Metall. 78C, 64 73. D. M., and Hagni, R. D., eds.) Proceedings AIME,
Burns, R. G., and Burns, V. M. (1977) In Marine 1095-107.
Manganese Deposits (G. L. Glassby, ed.) 185 248. - - ( 1 9 8 4 b ) Geol. Mag. 121, 483 8.
----(1978) Scanning Electron Microscopy, SEM Inc. - - ( 1 9 8 4 c ) Neues Jahrb. Mineral. Mh. 9-16.
I, 245 51. Paterson, E. (1981) Am. Mineral. 66, 424-7.
-- (1979)Reviews in Mineralogy, 6, 1 40. Siegel, M. O., and Turner, S. (1982) Science, 219, 172-4.
----and Stockman, W. H. (1983) Am. Mineral, 68, Tooms, J. S., Summerhayes, C. P., and Cronan, D. S.
972-80. (1969) Oceanogr. Mar. Biol. Ann. Rev. 7, 49 54.
(1985) Ibid. 70, 205 8. Turner, S., Siegel, M. D., and Buseck, P. R. (1982) Nature,
Buser, W. and Grutter, A. (1956) Schweiz. Mineral. 296, 841-2.
Petrogr. Mitt. 36, 49 62.
Chukhrov, F. V., Gorshkov, A. I., Sivtsov, A. V., and
Beresovskaya, V. V. (1978) Izv. Akad. N auk SSSR Geol. [Manuscript received 2 June 1986:
12, 86 95. revised 13 October 1986]
----Vitivyshaya, I. V., Drits, V. A., and Sivtsov,
A. V. (1982) In Ore Genesis The State of the Art Copyright the Mineralogical Society

KEYWORDS: manganate, todorokite, phyllomanganate, X-ray diffraction, Pacific Ocean, manganese nodules.

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