MÖSSBAUER EFFECT STUDY OF PHYSIOCHEMICAL TRANSFORMATION OCCURRING TO IRON IN FOSSILIZED BONES

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MÖSSBAUER EFFECT STUDY OF PHYSIOCHEMICAL TRANSFORMATION OCCURRING TO IRON IN FOSSILIZED BONES

H. Sallam, N. Ali, M. Hassan

To cite this version:

H. Sallam, N. Ali, M. Hassan. MÖSSBAUER EFFECT STUDY OF PHYSIOCHEMICAL TRANS-

FORMATION OCCURRING TO IRON IN FOSSILIZED BONES. Journal de Physique Colloques,

1979, 40 (C2), pp.C2-439-C2-441. �10.1051/jphyscol:19792153�. �jpa-00218527�

JOURNAL DE PHYSIQUE Colloque C2, supplhtent au n o 3, Tome 40, mars 1979, page C2-439

M~SSBAUER

EFFECT STUDY OF PHYSIOCHEMI CAL TRANSFORMATION OCCURRING TO IRON IN FOSSILIZED BONES

H.A. Sallam, N.A. Ali and M.Y.

assa an*

Mijssbauer Laboratory, Faculty of Science, AZ-Azhm Univ. Cairo, Egypt

* ~ e o Z o ~ ~ Department, Faculty o f Science, United Arab Emirates Univ. Abu Dhabi, Egypt

Rdsum6.- On a appliqud la spectromdtrie MGssbauer 1 1'6tude des formes du fer dans des os fossilis6s de la formation phosphatique de l'oasis Dakhla en Egypte; les transformations physicochimiques ont dt6 dgalement dtudides. Les rdsultats indiquent que le mCcanisme de min6ralisation et de transforma- tion est plus compliqug que ce que l'on pensait auparavant, avec en particulier l'existence de plus d'une forme du £er. Chacune de ces formes passerait par plus de deux stades de transformation avant d'atteindre l'dtat final a-Fe203, caractgtistique de tous les fossiles d'origine mGditerran6enne.

~bstract.-MEssbauer effect spectroscopy id applied to investigate the iron forms present in fossili- zed bones from the phosphatic formation at Dakhla Oasis in Egypt, and to study the physiochemical transformations occurring to these iron forms. The results showed a more complicated mechanism of mineralization and transformations than that of the previously studied plant and invertebrate fossils from the same region, where more than one iron form are identified in the spectrum of each sample.

Each of these forms had passed through more than two stages before it was transformed to the final iron form (a-Fer03) characteristic of all fossils from the Mediterranean Sea region.

l . Introduction.- Extending our previous studies /l/ ponent to another magnetic one, after heating at

on fossilized plants and animals from the Mediter- 5 0 0 ~ ~ ~ having magnetic field of 491 kOe and quadru- ranean Sea area in Egypt, we are dealing in this pole splitting of 0.49 mm/s indicate that this dou- work with the study of fossilized bones. Our aim is blet is due to y-FeOOH / 3 / which decomposes to to investigate the states and forms of iron in fos- y-Fez03 then y-Fe203 to a-Fez03 / 4 , 5 / .

as a minor quantity. The iron compounds are very

small traces that it could not be identified exactly. Fig' ^: The room temperature ME 'pectra of two samples of vertebrate from the phosphate formation silized bones, as iron could not be identified in

On the other hand two iron components could be de- in Dakhla Oasis fossilized bones from Brazil 1 2 1 , and to study the XIO 4

physiochemical transformations occurring to these ^{I D 0}

98

iron forms until1 they reach their final form. 9 6 9 4

Two fossilized bone samples are collected from

1

^{9 2}

the phosphatic formation at Dadhla Oasis in the 90

$ ^{8 8} Western Desert of Egypt and are measured using the

g

ME and X-ray techniques. Some plant and animal (in-

'

', X 1 0

vertebrate) fossils are measured also for compari-

2 99

son.

9 8

2. Results and discussion.- The X-ray diffraction 97 9 6

results of the fossilized bone samples showed that 9 5

the samples consist of dolomite (CaMg (C03)2) as a 92

tected in the ME spectrum of each bone sample

On the other hand the second component is dif- (Fig. I). The main and more incense one was the same

for the two samples (doublet C). The values of the ferent in the spectrum of each bone sample. For sam- ME parameters of this doublet (table I) and its ple 2 it is a singlet (D) having I.S. = 0.12 mm/s, transformation-after heating the sample at 300'~

-

while for sample 1 it is a doublet (F) having ME

parameters characteristic of ~ e ions. ~ + to a magnetic component (Fig. 2) having magnetic

field of 473 kOe and quadrupole splitting of 0.16 The presence of some percentage (~26%) of the

*/S, then the transformation of this magnetic corn- iron in this sample in the divalent state is in

G,C2

- _{. .} ..

> ...

-

. . 5,-,F2

.

~.

^, . . \ . .

, ... ^{, .} _{- .} ...

- - -

- -

- ,

L I I

- 6 - L -2 D 2 L 6

Cl,C2

-

^, . . .. , . 4 . .

-

^{. ..}

:

. , '... .: : ., , .

.

^{. . .}

.

^{. . . ( .}

- . ... .-:. -.

- - - -

3 3 1 1 1 1 1 t t l I

-10 - 8 - 6 - & - 2 0 2 f, 6 8 10

major quantity and hydroxyapatite (Ca10(OH)2(P0~)6) Velocity ( m m ~ s ) 4

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792153

C2-440 JOURNAL DE PHYSIQUE

contradiction with the results of all other fossils and bones measured in this work (table I) and in previous work /I/ on fossils from the same region, where all showed the presence of all iron in the

trivalent state. So the formation of this divalent iron in this sample may be due to special reducting atmosphere which was surrounding this sample in its burial site. Any how the ferrous component oxidized on heating in air to the same ferric compound which exists in the other bone sample as the minor iron- form constituent (Fig. 3). On the other hand this component (singlet D), after heating to 80O0C, transformed to a new form (doublet G) which has the same value of isomer shift like singlet D and a quadrupole splitting = 0.36 m / s . These results may be due to either the distortion of the lattice site of the iron ion in compound D from cubic symmetry, or the decomposition of this compound to another compound G in which the iron is in a distorted tetrahedral site and in a paramagnetic state also.

So singlet D, which was not observed before in the spectra of plant and (invertebrate) fossils, may be due to the presence of some form of iron phospha- te. It can be also due to any iron form connected with the mineralized bones, if Ohere is a connection

Velocity (mm/s )

between the initial building of organic matter and

Fig. 2 : The ME spectra of a fossilized bone sample the replaced or formed mineral form. at R.T. (before heating and after it was heated at

different temperatures).

Table I : The room temperature ME parameters of fossilized samples from different localities in Egypt.

I

Sample

:

^Locality

component^

^{1 - S - Q . S .}

I I m / s .

;

^{m / s . kOe H}

I

^t State of iron

I l

( 1 ) :Phosphatic horizon C

i

^0.35

I

^0.54

\

^Zero

I

Fe3+(non-mag.)

t t l .

Fossilized bone :Dakhla Oasis

:

^F

1

^1.32

i

^1.62

^:

^Zero

j

~e~+(non-mag.)

l I t 1 I

1 I I 1 t l

l l I l 1 1

t t 1 I 7 t

1 1

(2) :Phosphatic horizon C

i

^0.32

i

^{0.56 Zero}

j

Fe3+(non-mag.)

1 I I I

Fossilized bone :Dakhla Oasis

:

^D

i

^{0.12 Zero Zero}

\

Fe3+(non-mag.)

t

(3) l ^{I t} l ^t I ^t t ¹ t ^t t

Fossilized stem :Kharga Oasis _A

:

^{0.43 0.40 365}

;

Fe3+(-mag.)

of plant ₁ ^I _t ^l _l ¹ _t ¹ _{t I} ¹

l l t t t I

I l 1 t t 1

I t t l t I

1 t

(4) ¹ I A 0.40 0.48 352

i

~e~+(ma~.)

Fossilized :Kharga Oasis

cephalopods t I B t I 1 t

0.44

i

^{0.32 501} ~e~+(mag.)

1 l t t l t

t t l l t t

l I 1 1 t 1

1 1 l 1 I 1

(5) ^S :Dakhla Gasis ^{* 1}

Fossilized ^A 0.40

J

^{0.56 348}

1

~e~+(mag.)

l I l l I

pelecypods t l l 1 l 1

1 I I t t 1

1 t t I

l l t 1

I l I l l 1

(6) ^t t ^l

Fossilized nut :Aswan

c 1

^{0.37 0.59}

j

^Zero ~e~+(non-mag.)

I B

:

^{0.52 0.34 503}

:

Fe3+(mag.)

1 l 1 l I

l l 1 l l 1

1,s. is relative to Fe in Cr.

-

Error in velocity scale is 5 0.08 m / s .

-

Error in H is 2 5 kOe.

References

9 0 n Fe3+(doublet C )

0 FeZ+(doublet F )

,,,

a Fe3+rnag (smxet E) X ~ e ~ + m a g (sixet B)

7 0

'.

⁺ ~ e ~ + n o n - r n a g lstnglet D)

+

Fe3+non-mag (doublet G) 0

LZ

- ^. _'.,

i 6 0 \A- - -

-

- -

-

^x--y

4 X-X

C

I I l I l I 1 I

I

R.T. 100 2 0 0 3 0 0 L 0 0 5 0 0 6 0 0 700 B 0 0 ' TEMERATURE

,

^C'

Fig. 3 : The transformations occurring to iron forms present in a fossilized bone sample.

3. Conclusion.- From the obtained results it can be concluded that :

i. The mechanism of mineralization and the physio- chemical transformations occurring to the initial replacing minerals until1 they reach to their final form is more complicated than those in case of plant and invertebrate fossils, where the mechanism in those cases was accomplished in two stages only : the formation of (replacing with) an iron mineral connected to the immediat envi- ronment in which the fossilization process occur- red, then the decomposition of this mineral to the iron oxide a-FeeOs.

ii.Measurements and studies are needed after heating the samples at more elevated temperatures (which is not available at our Laboratory now), to see whether the last iron form obtained (doublet G) will transform to a-FezOs, and when, or not.

/ l / Eissa, N.A., Sallam, H.A., Ashi, B.A., Hassan,

M.Y. and Saleh, S.A., J.. Phys. D : Appl. Phys.9 (1976) 1391.

/ 2 / Mattivich, E. and Danon, J., Notas de Fisica

17

n05 (1971) 237.

131 Takada, T., Kiyama, M., Bando, Y., Nakamura, T., Shiga, M-, Shinjo, T., Ya Mamoto, N., Endoff, Y., and Takaki, M., J

.

^Phys

.

Soc. Japan

E

⁽¹ 964) 1744.

/4/ Gomaa, S.S., "ME Study of Hydrated Iron Oxide Group". M. Sc. Thesis, Faculty of Science, Al- Azhar University Cairo (1973).

/ 5 / Kelly, W.C. "Application of D.T.A. to identifica- tion of Natural hydrous ferric oxides" Am. Miner.

41 (1956) 353.

-

Acknowledgment.- The authors are pleased to express

.

their deep gratitude to'professor N.A. Eissa, Head of assbauer Laboratory ~ l l ~ z h a r University for helpful discussion.