MÖSSBAUER EFFECT STUDY OF THE RELATION BETWEEN RIVER CONCRETIONS AND MANGANEZE NODULES

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MÖSSBAUER EFFECT STUDY OF THE RELATION

BETWEEN RIVER CONCRETIONS AND

MANGANEZE NODULES

N. Eissa, H. Sallam, H. El-Kerdani, F. Taiel

To cite this version:

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JOURNAL DE PHYSIQUE Colloque C6, supplkment au no 12, Tome 37, Dkcembre 1976, page C6-857

MOSSBAUER EFFECT STUDY

OF

THE RELATION

BETWEEN RIVER CONCRETIONS AND MANGANEZE NODULES

N. A. EISSA, H. A. SALLAM, H. A. EL-KERDANI and F. M. TAIEL (*)

Mossbauer Laboratory, Faculty of Science, Al-Azhar University Cairo, Egypt.

Rksumk.

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Des Bchantillons provenant de concrktion de rivikre trks semblables a des nodules maritimes quant

B

l'apparence e t ~ 8 la couleur ont Bte Btudie par 1'Effet Mossbauer, diffraction de Rayon X- et spectroscopie IR. Les propri6tQ de leurs constituants ont et6 comparkes B celles des nodules fer-mangan6ze. Les rBsultats ont montrB que la concretion de rivikre peut-btre consider6 comme un type des nodules fer-mangankze. I1 a montre une grande quantitk d'un complexe de fer bivalent a c6t6 d'un complexe de fer trivalent-Fe(CH)s. Ce complexe ferreux est transform6 par chauffage en un ferrique paramagnetique intermkdiaire et finalement en une ferrite FeMn a 600 "C environ.

Abstract.

-

A number of river concretion samples which showed a high resemblance in appearance and in colour with those of the ocean nodules were studied using ME, X-ray diffraction and IR spectroscopy. The properties of their constituents were compared with those of the ocean iron-manganeze nodules. The results showed that river concretions may be considered as a type of iron-manganeze nodules. It showed a major amount of a divalent iron compound beside the trivalent iron compound-Fe(0H) 3. This ferrous compound is transformed by heating to an inter-

mediate paramagnetic ferric one, and finally to an Fe-Mn ferrite at about 600 "C.

1. Introduction.

-

The most interesting mineral deposits of the ocean floor are iron-manganese nodules. Structural studies of iron-manganese nodules have been started few years ago, in a trial to discover the formation mechanism of these nodules. Mineral identification by x-ray analyses was found to be difficult due to the fine-grained structure of the nodules.

The ME technique which has a great advantage in structural studies of fine-grained particles was recently applied in the study of iron-manganese nodules. The first application was carried out by Gager [l]

(1968) on three samples from the Atlantic Blake Plateau and from Pacific Ocean. The spectra of all samples showed a quadrupole splitted doublet consis- tant with the presence of lepidocrocite or goethite in a h a l y divided state. The spectrum of a sample heated to 650 0C showed a six-line pattern with a hyperfine field of 500 kOe and a superimosed doublet. Then many publications appeared on the subject containing a variety of proposals concerning the structure of these nodules. Herzenberg [2] suggested that the nodules are formed ad goethite. Sohnson and Glasby [3] indicated that iron'is present in more than one ferric hydroxide in the nodules Hrynkiewicz

et al. [4] (1970) concluded that in spite of the disorder

and impurity of the nodule material the ME spectra (*) Physics Department, Faculty of Engineering, Cairo University, Egypt.

of Pacific Ocean nodules are so simple and repro- ducible. Hrynkiewicz [5] (1972) continued his studies on Fe-Mn nodules from various Pacific Ocean locations. All his results confirmed that the iron in the nodules exists as Fe(OH), gel, and does not depend on the geographical location. Georgescu et al. [6] stated that the widths of the spectral lines obtained for the nodules samples were wide and can hide hyperfine splitting below 77 K.

In the present work the Mossbauer effect, x-ray and Infra-red measurements were applied to study iron-manganese nodules from Oceans. (Atlantic and Pacific) and from mountains (Bermuda and Hungary). River concretions (Tissa River) were also studied. The aim was to compare the state of iron in these nodules and concretions and to propose the conditions and mechanism of formation of both types.

2. Experimental procedure.

-

All samples were supplied by the Institute of Nuclear Research of the Hung. Acad. of Science, Debrecen, Hungary. Infor- mations about the nodule samples are given in table I, and chemical analysis is presented in table 11.

The ME absorbers were prepared from the nodules material after it has been crushed into a powder of size less than 0.2 mm. Then it was suspended together with 20

%

cellulose powder in a 2.5

%

warm gelatine solution and filtered by vacuum soaking onto a filter paper disk, so that the quantity of powder amounts was to 80 mg/cm2. The ME spectra were measured

54 *

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C6-858 N. A. EISSA, H. A. SALLAM, H. A. EL-KERDANI AND F. M. TAIEL

by a spectrometer of the constant acceleration type which was coupled to 512 channel analyser. The source used was 40 mC. Co5 in Cr matrix.

TABLE I

Information about iron manganese nodules

No. Coordinates Depth

-

1 Unknown Unknown

2 120 12'N North Pacific Ocean

1320.33 W 5 028 m 3 310 01.6' N Blake Plateau 78O 18.8' W 900 m 4 330 56.8' N Blake Plateau 680 47' W 4 743-4 892 m Q, -+ 5 - Atlantic Ocean m _L Bermuda Rise 6 - C Atlantic Ocean C Bermuda Rise 3 0 7 Atlantic Ocean o Bermuda Rise 8 Harskut Hungary Bakony mountain 8/C Ditch Kozoskut - 9 Csereboktny Hungary (Between szarvas and Szentes)

10 Tissea River Hungary

TABLE I1

Results of chemical analysis of manganese nodules Data in mglg

3. Results and discussion.

-

Figure 1 shows the room temperature ME spectra of all the nodule samples. The spectra indicate the presence of more than one state of iron, and that the iron ions in the nodules from different locations are bound in a similar fashion. So measurements at different temperatures were carried out on sample 8 in order to get more information about the different iron forms present in nodules. However studies with X-rays

I I I I l

-3 - 2 - 1 0 1 2

nese nodule samples.

V e l o c i t y ( r n r n l s )

No. Fe Mn CO Cu Ni

- -

-

- FIG. 1. -The R. T. ME spectra of the different iron-manga-

for this identification showed great difficulties due to the large broadening and high background. Applying Scherrer's [7] equation for particle size broadening the particle size was found to be equal 90 $. I0

A.

I. R. studies showed the existence of some com- pounds of Fe, Si and Mn in the form of oxides, hydrox- ides, or hydrated oxides.

Figure 2 shows the spectra of sample 8 at different temperatures. At liquid nitrogen temperature the spectrum indicates the preguree of two superimposed magnetic hyperfine patterns in addition to a quadrupole doublet. This reveals the existence of more than one form of iron in the nodules and which is in agreement with Johnson and Glasby [3] proposal. Moreover the magnetic transformations which hap- pened on cooling, indicate that the nodule material exists in a superparamagnetic state due to small particle size. In addition, the particle size of this sample which is from mountain is somewhat larger than that of the Ocean nodules which did not show hyperfine splitting on cooling [l, 41.

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THE RELATION BETWEEN RIVER CONCRETIONS AND MANGANEZE NODULES C6-859

-10 - 5 0 5 10

V e l o c i t y ( m m l s )

FIG. 2. -The ME spectra of sample 8 at different tem-

peratures.

doublet has ME parameters (Table 111) characteristic of Fe(OH), in accordance with the results of Hryn- kiewicz et al. [4, 51. The appearance of the magnetic pattern indicates a phase transformation or chemical decomposition of the initial magnetic component. The ME parameters of the formed magnetic phase are nearly similar to those of Fe,O, which has a spinel structure. Our results are in agreement with

ME parameters for Mountain sample and a River sample at different temperatures

I. S. Q. S. (mm1 (mm1 H Sample Temperature S) - - - - S) W e ) - Nodule sample 8 1.40 2.18 - River sample L. N. 0.44 0.72 - 0.64 0.24 478 Nodule 8 River sample Nodule 8 River sample

The parameters of the magnetic components are the average

values of the two sites of the spinel structure.

Error in velocity scale x f 0.08 mm/s.

Error in H 2 10 kOe.

I. S. relative to Fe metal.

Gager [l] results for his sample which after it was heated to 650 OC, it showed a magnetic pattern with a hyperfine field of 500 kOe and a superimposed doublet having Q. S. = 1.2 mm/s and I. S. = 0.6 mm/s. The ME measurements were carried out on three of the river samples. All~the samples showed nearly the same ME spectra, so heat treatment was carried out on one sample only. Figure 3 shows the ME

V e l o c i t y ( m m l s )

FIG. 3. - The ME spectra of the river concretion sample

different temperatures.

spectra of a representative river sample at different temperatures. It is clear from the figure that the major iron component in this sample is a ferrous compound below 5000C. The analysis (applying the peeling off method [8], of the R. T. spectra showed (Table 111) the presence of two quadrupole doublets. The first doublet has

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C6-860 N. A. EISSA, H. A. SALLAM, H. A. EL-KERDANI AND F. M. TAJEL

The different iron phases present and the transformation processes in both Ocean nodules and river concretions need more studies and discussions, but it is clear from our results that the iron phases and phase changes are nearly the same in both cases. The presence of a large, ferrous contribution in the spectra of the river samples probably indicates reducing conditions during the formation of these concretions. The X-ray diffraction pattern of the river sample showed less broadening of the lines indicating that the particle size of this sample is bigger than that in the case of ocean nodules.

4. Conclusion.

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From our results it can be deduced that all iron-manganese nodules studied contain iron in more than one chemical state. The predominant state is the iron hydroxide Fe(OH)3. River concretions can be considered as a type of iron manganese nodule containing iron in both divalent and trivalent states and showed similar characteristics as the Ocean nodules at 600 OC.

Acknowledgement. - The authors are grateful to Prof. A. Szalay for supplying the samples and helpful discussions.

References

[l] GAGER, H. M., Nature 220 (1968) 1021. [6] GORGESCU, I. I., MORARIU, M. and DIAMANOLESCU, L.,

[2] HERZENBERG, C. L., MiiSSbauer Effect Methodology, Rev. Roum. Phys. Tome 18, (1973) 401.

Vol. 5 (1. J. Gruverman, Pknum Press, New York) _[7]_BARRETT,_C._S.,Structure of Matals (Indian Press 1968).

1970, p. 202. _[8]_SIEGBAHN,_K.,_{Alpha, Beta and Gamma Spectroscopy,}

[3] JOHNSON, C. E. and GLASBY, G. P., Nature 222 (1968) 376. _{(North Holland Pub.} _{Comp.) 1965.}

[4] HRYNKIEWICZ, A. Z., SAWICKA, B. D . and SAWICKI, J. A.,

Phys. Stat. Sol. (a) 3 (1970) 1039. [g] GOLDBERG, E. D., Biol. BUN., 102 (1952) 243.

[5] HRYNKIEWICZ, A. Z., PUSTOWKA, A. J., SAWICKA, B. D. [l01 GRAHAM, J. W. and COOPER, S. C., Nature, 183 (1959)