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AGING EFFECT ON MÖSSBAUER SPECTRUM OF COPROLITE
N. Eissa, H. Sallam, B. Ashi
To cite this version:
N. Eissa, H. Sallam, B. Ashi. AGING EFFECT ON MÖSSBAUER SPECTRUM OF COPROLITE.
Journal de Physique Colloques, 1979, 40 (C2), pp.C2-449-C2-451. �10.1051/jphyscol:19792156�. �jpa-
00218530�
JOURNAL DE PHYSIQUE
Colloque C2, suppl6ment
auno 3, Tome
40,mars 1979, page C2-449
A G I N G E F F E C T ON MOSSBAUER SPECTRUM OF C O P R O L I T E
K K
N.A. E i s s a , H.A. Sallam and B.A. Ashi
Physics Department, Faculty of Science, lhziversity of Qatar, Doha, Qatar
H
MiSssbauer Laboratory, Faculty of Science, AZ-Azhar University Cairo,
E g y p tRdsum6.- La technique de l ' e f f e t ~ G s s b a u e r a 6 t 6 u t i l i s L e pour l ' d t u d e d f 6 c h a n t i l l o n s de c o p r o l i t e (bouse f o s s i l e ) , provenant d'horizons gdologiques d i f f d r e n t s du d e s e r t nord-est d e l T E g y p t e . Des ph6nomEnes de r e l a x a t i o n s o n t observds dans l e s s p e c t r e s , en r e l a t i o n systematique avec l a profondeur de l ' h o r i z o n d ' o r i g i n e , c.a.d. 1'Pge de l ' d c h a n t i l l o n . Ceci confirme l ' e x i s t e n c e de r e l a t i o n e n t r e l a t a i l l e des p a r t i c u l e s e t l ' e f f e t de v i e i l l i s s e m e n t .
Abstract.- The ~ g s s b a u e r E f f e c t (ME) technique was a p p l i e d t o s t u d y c o p r o l i t e ( f o s s i l dung) samples from d i f f e r e n t g e o l o g i c a l horizons i n t h e North-Eastern Desert o f Egypt. R e l a x a t i o n phenomena were observed i n t h e s p e c t r a which i s i n a s y s t e m a t i c r e l a t i o n w i t h t h e depth of t h e h o r i z o n , i . e . , t h e age of t h e sample. This supported t h e e x i s t e n c e of a r e l a t i o n between t h e p a r t i c l e s i z e of t h e i r o n oxide and t h e aging e f f e c t .
1 . I n t r o d u c t i o n . - I n s t u d y i n g " c o p r o l i t e " which i s f o s s i l dung, i . e . p e t r i f i e d excrements of animals l i v i n g d u r i n g t h e time a rock formation was deposi- t e d , t h e r e s u l t s showed t h e presence of t h e same i r o n forms i n a l l samples, b u t w i t h a remarkable differen- ce i n t h e i n t e n s i t y of t h e same i r o n form from type t o type of c o p r o l i t e . This l e d t o suggest t h a t t h e s e d i f f e r e n c e s may be due t o e i t h e r a r e l a t i o n between t h e o r i g i n a l n u t r i t i v e o r g a n i c m a t t e r and t h e r e p l a - c i n g m a t e r i a l i n t h e d i f f e r e n t c o p r o l i t e s , o r t h e d i f f e r e n c e i n t h e age of t h e samples which can a i d i n transforming some i r o n form t o t h e o t h e r . So i t was decided t o s t u d y c o p r o l i t e samples from d i f f e r e n t
g e o l o g i c a l h o r i z o n s t o d e t e c t t h e aging e f f e c t , i f it i s e x i s t .
2 . Experimental d e t a i l s . - Three d i f f e r e n t types of c o p r o l i t e samples were c o l l e c t e d from d i f f e r e n t l o c a - l i t i e s and from t h e f i r s t type / l / , o t h e r samples were c o l l e c t e d from t h e same l o c a l i t y b u t from d i f - f e r e n t g e o l o g i c a l horizons a t lower depths ( s e e t a b l e I ) . The samples were s t u d i e d u s i n g ME technique a t b o t h room and l i q u i d n i t r o g e n temperatures. DTA mea- surements were c a r r i e d a l s o f o r some samples. The ME a b s o r b e r s were prepared from 200 4 4 . 5 cm2 of t h e f i n e powdered m a t e r i a l u s i n g a c o n s t a n t a c c e l e r a t i o n d r i v i n g system coupled t o a 512 multichannel analy- z e r . The s o u r c e was 20 m C i 5 7 ~ o i n C r matrix.
3. R e s u l t s and discussion.- Figure 1 shows t h e room temperature ME s p e c t r a of a r e p r e s e n t a t i v e sample from each of t h e t h r e e c o p r o l i t e types. The ME re- s u l t s a r e summarized i n t a b l e I. These r e s u l t s showed t h e presence of cc-Fe2O3 i n a l l t h e samples, b u t w i t h v a r y i n g amounts. This r e s u l t i s i d e n t i c a l w i t h t h a t
o b t a i n e d f o r t h e f o s s i l s of t h e proper animal o r p l a n t from t h e same r e g i o n / l / .
F i g I : The R.T. ME s p e c t r a of a r e p r e s e n t a t i v e sam- p l e from each of t h e t h r e e c o p r o l i t e types.
The ME r e s u l t s showed a l s o t h e presence of two para- magnetic components b e s i d e a-Fep03. One component has t h e room temperature ME parameters c h a r a c t e r i s t i c
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792156
JOURNAL DE
PHYSIQUE
Table I
:The ME parameters of the different coprolite samples
Sample
'. qSS.
:H.
:% o f :
:
No. i Shape
:Locality I~em~erature I~om~onentI I"' . m / s : : mm/s
:kOe
:total
::
iron
: :Ia
:Rolled bodies
:Phosphatic
:R.T.
:A
:0.44
:0.48
:498
:25
::
region at
::
Safaga
:B i 0.32 i 0.64 i zero 68
:
(ground
:C
:0.40
:1.20
:zero
:7
::
surface)
:2 Ellipsoidal Nubban R.T.
:A
:0.44 0.40 i 5 0 0
:58
:Sand-stone
:B
:0.29
:0.49 : z e r o
:31
:at Aswan :
:
C i 0.37 i 1.14 i zero I 1 i
:
3
:Spiral
:Safaga
:R.T.
:A
:0.42
:0.40
:505
:59.5
: :(small size)
::
C i 0.33 i 1.06 zero
:29.5;
:
D
:0.56
:0.56
:393
: 1 1 :30m depth i R.T. ' A :
:0.40 500
:I Ib I
: D :
:0.36
:340
:L.N. A j 0.44 0.40 525
:25
:
B
:0.32
:0.56
:zero 68
:C : 0.36 : 1.13 : zero : I
: 1, : :
L.N.
:A
:0.50
:0.48
:492
:68
::
60m depth
:L.N.
:A
:0.44
:0.48
:480
:74
:-
:E. i 0.32 zero zero 26 i
I.S. is relative to Fe in Cr.
Errors in velocity scale
f0.08 mm/s.
Errors in magnetic fields
f5 kOe.
of either pyrite, glauconite, Fe(0~)~ or y-FeOOH where these compounds have nearly the same room temperature ME parameters, and all these compounds were identified in other fossils /1,2/. The DTA mea- surements of sample
1showed an endothermic peak at 200°C and an exothermic one at 550'~. These ther mal behaviours together with the values of the ME parameters of the main paramagnetic component in the spectra of this sample at both room and liquid ni- trogen temperatures (table I) are characteristic of lipedocrocite (y-FeOOH) /3,4/.
So this component which constitutes 68% of the total iron present in coprolite type
1may be due to the presence of y-FeOOH. The pattern due to y-FeOOH disappeared in the spectrum of the sample representing type 3 (Fig.
1)with the appearance of a magnetic pattern characteristic of a-FeOOH /5/.
The second paramagnetic component has IS
=0.40
and QS
=1.12 m / s which are characteristic of ~ e ~ + ion in octahedral site /6/.
It is seen that samples I and 3 which are from the same locality, but belong to two different types of animals showed differences in their results indi- cating that there may be a relation between the sort of the original nutritive organic matter and the re- placing material. The age of the coprolite samplecan also be a factor which aids in transforming one iron form to the other.
Figure 2 shows the room temperature ME spectra of three samples of type
1from different three depths. The results of sample
lawhich is fromground surface showed the stability of the state and percen- tage of each iron component after cooling to the li- quid nitrogen temperature (table I).
On the other hand sample
lbwhich is from a
lower horizon (30m depth), i.e. older than the first
sample showed a relaxed spectrum with broad lines
and slope in it,s baseline. This is due to superpara-
magnetic behaviour resulting from small particle
sizes /7/.
V e l o c i t y (mmls)
F i g . 2 : The ME s p e c t r a of t h r e e samples from d i f f e - r e n t d e p t h s , I from t h e ground s u r f a c e , 1 from 30m d e p t h and ;c from 60m depth. b
The a n a l y s i s of t h i s spectrum ( t a b l e I ) showed t h e p r e s e n c e of two magnetic p a t t e r n s (A and D). The v a l u e s of t h e parameters of t h e s e two p a t t e r n s a t room and l i q u i d n i t r o g e n t e m p e r a t u r e s a r e c h a r a c t e - r i s t i c of f i n a l l y d i v i d e d p a r t i c l e s of cl-Fe00H ( f o r t h e s m a l l f i e l d p a t t e r n ) and a-Fe20,. The same values
time e l a p s e d between t h e p e t r i f i c a t i o n p r o c e s s and t o d a y , confirms t h e e x i s t e n c e of t h e a g i n g e f f e c t / 9 , 1 0 / . T h i s e f f e c t h a s been proposed r e c e n t l y by Danon e t a l . / 9 / and Gangas e t a l . /10/ from t h e i r ME measurements on a n c i e n t p o t t e r y . They e x p l a i n e d t h e time dependence of t h e p a r t i c l e s i z e observed by t h e ME s p e c t r a of a n c i e n t a r t i f a c t s t o be due t o a slow d i s i n t e g r a t i o n p r o c e s s of t h e p a r t i c l e s i z e of t h e i r o n o x i d e . T h i s f a c t i n d i c a t e s t h a t t h e o r i g i n a l l y l a r g e s i z e i r o n o x i d e s p a r t i c l e s i n c o p r o l i t e s s u f f e r e d a n e r o s i o n r e d u c t i o n t o s m a l l e r p a r t i c l e s .
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(1956) 353./ 4 / Takada, T., Kiyama, M . , Bando, Y . , Nakamura, T., S h i g a , M., S h i n j o , T., Yamamoto, N . , Endoff, Y . and Takaki, M . , J . Phys. Soc. Japan
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7 (1974) 2121; Sallam, H.A., M. Sc. T h e s i s i n
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Phys., F a c u l t y o f S c i e n c e , Al-Azhar U n i v e r s i t y (1972)./ 6 / B a n c r o f t , G.M., Maddock, A.G. and Burns, R.G., Geochem. Cosmochem. Acta
2
(1967) 2219.of parameters and t h e shape of t h e spectrum W e r e ob- / 7 / Gonser, U., Topics i n Applied P h y s i c s " ~ b ' s s b ~ ~ e ~ t a i n e d p r e v i o u s l y / 5 / f o r n a t u r a l g o e t h i t e (a-FeOOH) Spec." Vol. 5 , (Springer-Verlag, B e r l i n h e i d e l -
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of p a r t i c l e d i a m e t e r -200
1.
/ 8 / Cohen, R.L.,"Applications of MGssbauer Spectros-
The spectrum of sample 1 which i s from t h e copy", Vol. 1 , (Academic P r e s s , New York) 1976.
lowest h o r i z o n (60m d e p t h ) , i s r a t h e r broad and t h e /9/ Danon, J . , E n r i q u e z , C.R., M a t t i i v i c h , E., f i e l d began t o c o l l a p s e . It h a s t h e appearance o f a Mariada, C., d e M. Coutinho B e l t r a o , J. Physique
37 (1976).
spectrum t a k e n j u s t below t h e m a g n e t i c o r d e r i n g tem-
-
1101 Gangas,N.H.J., S i g a l a s , I. and Moukarika, A . , p e r a t u r e . The spectrum of t h e same sample a t l i q u i d J. Physique
22.
(1976).n i t r o g e n t e m p e r a t u r e ( t a b l e I ) showed mainly a magne- t i c p a t t e r n t y p i c a l t o a-Fe203. So i t i s s e e n t h a t t h e o l d e r sample has t h e s m a l l e s t p a r t i c l e s i z e and t h e less number of i r o n forms, where a s time e l a p s e d one i r o n form transformed t o t h e o t h e r till a l l reach t o t h e f i n a l i r o n form a-Fe203.
The s h a p e of t h e s p e c t r a of t h e s e t h r e e samples i n d i c a t e s /8/ a l s o t h a t : f o r t h e f i r s t sample t h e s p i n r e l a x a t i o n time (of t h e i r o n o x i d e ) .rs >>
-cL,
w h i l e f o r sample 1 b , Ts J TL which e q u a l s 4xl0-'s and f o r sample l c Ts T ~ .
The observed c o r r e l a t i o n between t h e p a r t i c l e s i z e and t h e d e p t h , which i s an i n d i c a t i o n o f t h e
