A. H., 1967. The
;ectonic zone (C.
and the days of anganese ore in lie USSR, “Nau-
>rt of the XXIII in sulphide ores.
tic processes in Russian).
(in Russian), n. Geol. ore de-
On the Main Aspects of Formation of Ferromanganese Ores in Recent Basins
I. M . Va r e n t s o v, U .S .S .R .
ABSTRACT
The distribution of Mn and Fe in water, sediments, hydroxide nodules and crusts of Eningi-Lampi ore-bearing lake is regular, and concordant from the source to the areas of accumulation of these components. Mn-Fe hydroxide nodules and crusts oc
cur at the water-sediment interface, and more rarely in the upper (0-5 cm) film of brown watery mud. The leading role in the formation of Mn-Fe nodules and crusts is played by the chemosorption and auto-catalytic oxidation in the course of interaction of component-bearing solutions with active surfaces.
This is considered to be the basic process for the model of ferromanganese ore formation in recent basins.
Despite the differences in the physico-geographical and geochemical characteris
tics of lakes, mediterranean seas and oceans, the formation of ferromanganese hy
droxide nodules and crusts in these basins may be explained by this model.
INRODUCTION
Mn- Fe h y d r o x i d e n o d u l e s a n d c r u s t s in K arelian Lake E n in g i-L am p i occurred a t th e w ate r-se d im e n t in te rfa c e. M ore ra re ly th e y a re fo u n d in th e u p p e r (0-5 cm ) lay er of brow n w a te ry m ud. The im p o rta n t processes in th e fo rm a tio n of M n-Fe nodules and c ru s ts a re chem osorption and au to cataly tic o xidation a t th e in te rfa c e of th e com ponent-bearing solution w ith th e active su rfaces. D espite th e d ifferen ces of physico-geographical and geochem ical c h a ra c te ristic s o f lakes, m e d ite rra n ea n seas and open oceans, th e fo rm a tio n of fe rro m a n g a n ese hydroxide nodules and c ru s ts in th ese b asin s m ay be explained by using th e model discussed.
T he purpose of th e stu d y w as to c o n stru c t a p re lim in a ry model fo r th e fo rm a tio n o f m anganese and iron ores in recen t basins. The E n in g i-L am p i Lake in C en tral K arelia w as chosen as th e s ite fo r in v e stig a tio n of th e o re-fo rm in g process. The m in era l fo rm atio n in th e lake is evident, and th e re latio n sh ip s be
tw een th e source of th e m in e ra l-fo rm in g c o n stitu en ts and th e a re a s of th e ir accum ulation a re clear. I t would be a naive over-sim plification to suppose th a t th e phenom ena of m in eral fo rm a tio n observed in th is lake m ay be d irectly ex
tra p o la te d to explain th e d etails of M n-Fe m in eral fo rm a tio n in m e d ite rra n ea n seas and oceans. The p relim in a ry model is n o t intended to cover all th e p a rtic u la r fe a tu re s o f each phenom enon, b u t to be used as an in s tru m e n t in th e stu d y of th e d iffe re n t processes of M n-Fe m in eral fo rm atio n .
E n in g i-L am p i L ake is a r a th e r n a rro w (1.0-1.7 km ) elongated (7 km ) lake, up to 6 m deep. The trib u ta r ie s of th e lake d ra in a re a s of Low er P roterozoic m etavolcanic basic rocks.
Authors’ addresses are given a t the back of this book.
SECTION 4
H ydrochem ical c h a ra c te ris tic s : T he w a te r of th e lake is brow nish, re su ltin g fro m th e dissolved hum ic co n ten t and suspended o rg an ic m a te ria l. I t is of re la tively low m in e ral co n ten t (23.98-40.38 ppm ) w ith p re d o m in an t H C 0 3 ions (14.65- 29.28 m g/1) am ong th e anions, and C a++ (1.80-3.60 m g/1) and M g ++ (1.70-3.89 m g/1) am ong th e cations. The o rg an ic m a tte r co n ten t reaches up to 32.86 ppm.
M n and F e in th e lake w a te r: The d is trib u tio n of p a rtic u la te d and dissolved fo rm s of Mn and F e w ere stu d ied w here th e sam ples w ere tak en . T he analysis o f the f iltr a te (0.5;/. f ilte r ) com pared to th e re sid u e suggested th a t 72-92% of to ta l Mn, and 30-48% of to ta l F e a re dissolved r a th e r th a n suspended.
T he co n ten t o f Mn in th e w a te rs o f th e lake (F ig . 1) decreases fro m P o ru sta R iver a t th e so u th e rn end, to w ard th e n o rth end of th e lake. T he co n cen tratio n of F e also decreases fro m south to n o rth , b u t in creases slig h tly a g a in a t th e n o rth end. The pH increases to th e n o rth .
C haracteristics o f s e d im e n ts: A w ide ra n g e of clastic sedim ents fro m boulder- pebbles to silt-clay sapropel-like m uds has accum ulated in th e lake. E ach ty p e of sedim ent has a c h a ra c te ris tic location an d chem ical com position (F ig . 2 ) . In g en eral, th e sedim ents of th e lake a re th e p ro d u cts of decom position of Low er P roterozoic basic volcanic rocks.
ppt M nFe pH
n * 0l
" ° u o • z o s z o o
10 s s s o 45- 40- 35 30 25
15 10 5
I 1“
Po r u s t a Ri v e r
I fl
M o u t h E s t u a r y
o r R i v E R o r Ri v e r - S 4.IE C „
100 0 100 to o too m
I ) d . D . O . U
2} A . D . O . 0
FIGURE 1 — Distribution of Mn, Fe (ppm), Eningi-Lampi Lake, Central Karelia.
396
Mn
Fe (n. 100), pH in waters of
24th IGC, 1972— SECTION 4
•esulting of rela- i (14.65- 1.70-3.89 86 ppm.
id forms s of the otal Mn, Porusta ation of le north boulder-
type of 2). In E Lower
PLATE 1 — (Photo 1-3, common linear scale). Photo 1, Mn, Fe hydroxides grow ing over the surface o f pebbles (cherts, altered basalts), thickness of coating to 30 mm. Photo 2. Mn, Fe, hy
droxide nodules, their cores - clastic grains. Photo 3. fragm ents of wood, their upper part, rising above the water-sediment interface are coated by cap-like Mn and Fe hydroxides. Photo 4. the pebbles of igneous rocks, their surfaces rising above water-sediment in
terface, are coated by Mn-Fe hydroxides.
24th IGC, 1972 — SECTION 4 397
Fe-Mn NODULES AND CRUSTS
T he nodules and c ru s ts a re m orphologically d iffe re n t, b u t genetically very sim ila r pro d u cts. Some o f th e m orphological v a rie tie s o f nodules and crust-like co atin g s a re show n in P la te I. Especially n o tew o rth y is photo 3, show ing th a t th e u pper p a r t of wood fra g m e n ts is covered by a cap-like g ro w th of M n-Fe hy
droxides. D u rin g sam p lin g fro m u n d istu rb e d sedim ents, one can observe these cap-like Mn and F e coatin g s ris in g above th e sed im en t-w ater in terface. The p a r t of a d io rite pebble (photo 4) ris in g above th e sed im en t su rfa c e is covered by black M n-Fe hydroxide, b u t th e low er p a rt, w hich w as b u ried in sedim ent, h as a clean u n stain ed su rface. The w ater-sed im en t in te rfa c e is well shown by th e d is
tin c t b o rd er of M n-Fe hydroxides grow th.
The com position of nodules and c ru sts is as follow s:
1. M anganese n odules: p red o m in an tly M n hydroxide ( b irn e s s ite ) , M n up to 33% , F e up to 8-10% .
2. Iro n nodules: p red o m in an tly f e rr ic hydroxide (g o eth ite, hy d ro g o eth ite, am or
phous hydroxides of F e ) , F e up to 51% , Mn up to 2% .
3. N odules and c ru sts o f in te rm e d ia te com position: rep re se n te d chiefly by m ix
tu r e s o f th e above-m entioned hydroxide m in erals of Mn and F e. T h is type is p red o m in an t.
T he com positions o f in n e r and ex te rn a l p a rts of th e nodules a re of p a rtic u la r in te re st.
1. In n e r p a rts o f nodules a re m ainly composed of Mn hydroxides and to a lesser e x te n t o f F e hydroxides. The ex te rn a l c ru s t is m ainly composed of F e hydroxides w ith a d m ix tu re of Mn hydroxides.
2. T h ere is an evident association o f M n hydroxides w ith : Co (120-180). 1 0 -% , Zn (104-402). 1 0-% and BaO (1 .2 7 -2 .1 5 % ); F e hydroxides a re associated w ith : Corg (0.85-1.80% ), Co (1.44-3.46% ), N i (5-40). 1 0 -% , Cu (3-13). 1 0 -% .
3. The S i0 2 and AhCb com ponents of th e nodules a re very low; also such ele
m en ts as V and Cr, w hich occurs in am ounts of less th a n 0.0034% . N one o f th ese fo rm d istin c t associations w ith th e Mn and Fe.
Mode of occurrence: M n-Fe nodules an d c ru s ts a re found m ostly in th e zone o f deposition of sands and coarse silts (F ig . 2 ) . As a rule, th e nodules and cru sts occur on th e su rfa c e o f sedim ents. M ore ra re ly , th ey a re in th e u p p er th in lay er (5 cm ) o f brow n w a te ry m u d ; below th is m ud th e re is g re e n ish -g ra y silty mud, enriched by o rg an ic m a te ria l w ith o u t any M n-Fe hydroxide nodules. In th e zone of accum ulation of d a rk green, o ften d a rk g ray , silty, clayey, sapropel-like m uds, th e nodules a re n o t found.
A rea l d istrib u tio n of M n-Fe con cen tratio n in th e n odules: T he content of M n in th e nodules and c ru s ts decreases fro m th e P o ru s ta R iv er m outh across the so u th e rn p a r t of th e lake and re m ain s low along th e n o rth e a s te rn bank. The co n cen tratio n o f F e in th e nodules increases in th is directio n (F ig . 3 ).
Discussion
The accum ulation o f M n-Fe hydroxides is actively ta k in g place on the su rfa c e s o f coarse clastic p articles, walls of outcrops exposed a t th e edge of w a te r, an d even on fra g m e n ts of wood (P la te I, 3 ).
T he m orphological v a rie ty of nodules and c ru sts depends on th e environm ent a t th e exposed su rfa ces. In m ost cases, su rfa c e s a re in co ntact w ith bottom w a te rs ; m ore ra re ly , th ey a re in co ntact w ith in te rs titio n a l solutions o f m uds.
398 24th IGC, 1972— SECTION 4
ly very ust-like ig th at
■Fe hy- e these he part sred by has a he dis-
0 33%, amor- y mix-
;ype is ticular lesser
•oxides io-%, w ith:
:h ele- : these e zone
crusts 1 layer r mud, e zone muds, ent of iss the
;. The
n the Ige of nment wttom uds.
[ON 4
FIGURE 2 — Distribution of Mn in sediments (interval 0.0-10.0 cm ), Eningi-Lampi Lake.
1, M n /F e content (% ) in sediments. 5, 0.1 to 0.2% Mn.
2, M n /F e content (% ) in nodules. 6, Less than 0.1% Mn.
3, More than 1% Mn. 7, Boundary o f sediment type distribution.
4, 0.2 to 1.0% Mn.
P a tte rn s used in legend are as follo w s: 3, Fine-grained sands, coarse silts with admix
ture of clay and organic matter. 4, Silt-clay sapropel-like muds, dark grey to black.
5, Fluvial deposits: pebbles, boulders and coarse sands coated with Mn-Fe hydroxide crusts. 6, N ear shore sands, gravels and pebbles.
N —number o f sample Cl —clay
n — nodule of M n-Fe hydroxide S /c l ■—sandy clay
S — sand S t/c l— silty clay
St —silt
i i i i
fpfm iig
I f IV f I
Ie lETSKOe]
.akeEsissi-Lamp/'
lED %/il.HECORSK
! C.38/2 0.35
lmio(st/ch
k jm u iu n <i'i li/st]
s r e .2 0 | u-05
■ dT? o/ 4 s n
1 1
3 4
i 6 7
TT'MMn,Fe
M: plexes role. M with ir In the oxi suits o:
the lea lowed The pt react a and F<
multivi organie the fol
Me (M K t
400
1 Fr
values
^3
‘3.c
amounl creased solids - Morgar o f auto cCtJ
fa1 Th
’5b liberate
a sedimei
w supplier
to0) quantit
3 riched 1
ocs takes i
c intersti
ttS f <u tion th
2 |fa Probab
lake me
faoT
Genera
s
G Basins<4-H
O Th
.2G Recent
9 works
fa Mero, 1
■*3CO
1 Tooms,
s tion pr<
CO1 w
ized as 1. Nodi
2 seas an
o growing
Mfa nodules
1972— SECTION 4 24th IGi
Mn and F e dissolved in th e lake w a te rs a re p re se n t m ainly as org an ic com
plexes (hum ic and o th e rs) ; probably b icarb o n ate com pounds of Mn play a c e rta in role. M ost of th e m a te ria l in suspension is o rg an ic p a rticles and p la n t d e tritu s, w ith m in o r non-organic particle s.
In th e course of in te ra c tio n o f Mn and F e solutions w ith exposed su rfaces, th e oxide phases of these m etals a re form ed. O ur field observations, and th e re su lts of o u r experim ents, as well as th e w ork o f o th ers, allows us to conclude th a t th e lead in g role in th ese phenom ena is played by chem osorption in te ra ctio n s, fol
lowed by au to cataly tic oxidation (M organ an d Stum m , 1964; M ichard, 1969).
The phase of Mn and F e hydroxide fo rm in g on th e active su rfa c e can, in tu rn , re a c t as a very active sorbent, w hich prom otes new a cts of chem osorption of Mn and F e ; th ese elem ents a re fixed as th e oxide phases. The in te ra c tio n of th e m u ltiv ale n t com ponents m ay be accom panied by d e stru c tio n or oxidation o f th e ir o rg an ic complexes. F o r th e ap p ro x im ate estim atio n of k in etics of th e se processes th e follow ing sim plified equation m ay be used (M ichard, 1969) : —
d (^ e) = K (Me++)
Me — number of moles of metal, fixed by the weight unit (g) of solid;
(Me++) — concentration of metal of lower state of oxidation in solution (ppb);
K — kinetic constant, dependant on the nature of sorbent;
t — time.
F ro m th is equation one m ay m ake th e g en eral conclusion th a t, a t given values of pH and E h, w ith in c reasin g co n cen tratio n o f m etal in solution th e am o u n t of hydroxides of th is m etal fixed on th e active su rfa c e w ill also be in creased. The in te n sity of such fix a tio n depends on th e su rfa c e p ro p e rtie s o f th e solids — a ltered silicates, hydroxides o f Mn and Fe, etc. The ex p erim en ts 'o f M organ and S tum m (1964) show t h a t w ith in creasin g pH of solution, th e ra te s o f a u to c ataly tic oxidation of Mn and F e sh arp ly increase.
T he d a ta su g g e st th a t th e m a jo r p a r t o f th e Mn and some o f th e F e w as lib era ted fro m solution and accum ulated as hydroxide com pounds (nodules, cru sts, sedim ents) w ith in th e P o ru s ta R iv er e stu a ry . The n o rth e rn p a r t of th e lake is supplied w ith relativ ely sm all am ounts of Mn (F ig . 1-3). M eanw hile, th e m ain q u a n titie s of F e (in p a rtic u la te fo rm s) accum ulated in fin e-g rain ed m uds, en
riched by o rg an ic m a tte r. In th is environm ent th e decay of F e-b e a rin g com pounds ta k e s place, and F e moves into solution. T h is elem ent is able to d iffu se from in te r s titia l solutions to w ard th e bottom w aters. In a re a s of very slow sed im en ta
tio n th e a u to c ataly tic accum ulation o f F e on active su rfaces th e n ta k es place.
P robably th e relativ e e n rich m en t of w a te rs w ith F e in th e n o rth e rn p a r t of th e lake m ay be explained by th is model.
General Features of Formation of Mn and Fe Nodules and Crusts in Recent Basins
T he problem s o f fo rm atio n of M n and F e hydroxide nodules and c ru sts in R ecent b a sin s (lakes, seas, oceans) have been discussed in some com prehensive w orks (G oldberg and A rrh e n iu s, 1958; Sem enovitch, 1958; M anheim , 1965;
M ero, 1960; P rice, 1967; V inogradov, 1967; S trak h o v et al., 1968; C ronan and Tooms, 1969; Skonyakova and A ndrushenko, 1970). T he m ain fe a tu re s of fo rm a tio n processes in d iffe rin g physico-geographical en v iro n m en ts m ay be su m m ar
ized as follow s:
1. N odules and c ru sts of M n and F e hydroxides occur in lakes, m e d ite rra n ea n seas an d oceans, m ostly a t th e w a ter-sed im en t in te rfa c e, as cru st-lik e coatings gro w in g on rock, boulders and on m any kinds of su rfaces. M ore ra re ly , M n-Fe nodules a re found in th e upper p a r t of th e oxidized zone of sedim ents.
24th IGC, 1972 — SECTION 4
2. In ten siv e fo rm a tio n of M n-Fe nodules occurs w here th e ir ra te of g ro w th is considerably h ig h e r th a n th e ra te of sedim entation. F o r exam ple, in th e B altic Sea, M n-Fe nodules and c ru s ts a re m ost common on th e slopes, sum m its of sub
m arin e elevations, and a re a s of su b m arin e erosion of th e floor c o u n try rocks (V aren tso v and B lazhchishin, 1970). In oceans, th e nodules occur w idely on th e abyssal floor, w here th e ra te s o f sed im en tatio n a re relativ ely slow (0.2-3.0 X 10’3m m /y e a r) (B ezrukov an d an d R om ankevitch, 1970).
In those r a r e r cases w here M n-Fe nodules a re found in th e u pper oxidized p a r t o f sedim ents, th e ir fo rm a tio n is controlled by a complex set o f co nditions:
th e ra te s of th e ir g ro w th v ersu s th a t o f th e accum ulation of sedim ents, th e con
te n t o f o rg an ic m a tte r in th e sedim ents, and E h condition o f th e bottom w aters.
D iffe re n t values f o r th ese v ariab les lead to d if fe re n t re s u lts : b u ria l of oxide nodules, th e ir dissolution, tra n s fo rm a tio n of oxides of Mn an d F e and some o th e r tra n s itio n a l m etals in to silicate, carb o n ate, and sulphide com pounds, and th e u pw ard m ig ra tio n of th e nodule-bearing in te rv a l of m ud in accordance w ith sedi
m en tatio n . T he available in fo rm a tio n su g g ests th a t in a re a s w here sedim ents have a low co n ten t o f active o rg an ic m a tte r (fo r exam ple, th e P ac ific abyssal red cla y s), th e b u ria l of fe rro m a n g a n ese oxide nodules ta k es place. The com position o f these b u ried nodules is p ractically th e sam e as those ly in g on th e su rface of sedim ents (C ro n an and Tooms, 1969).
3. R ecent w ork (M anheim , 1965; P rice, 1967; C ronan and Tooms, 1969) has shown th a t in both th e ir m ineralogical com position an d th e association of tra c e elem ents w ith m a jo r ones, nodules d istin c tly re fle c t th e depth of th e ir fo rm atio n . The d a ta su g g e st th a t a t relativ ely shallow depths (to 3000 m ) b irn e ssite -ric h nodules associated w ith Co, Cu, P b , V an d B a pred o m in ate. In deeper w aters, to dorokite enriched by Ni and Cu predom inates. Some a u th o rs (M ero, 1965; M an
heim , 1965) sta te d th a t Fe-nodules accum ulate m ainly in shallow w a te rs and a re n o t ty p ical of abyssal environm ents.
T he physical reason fo r th e re latio n sh ip betw een d ep th and th e com position o f nodules is n o t clear. In some cases, th e problem m ay be com plicated by th e d iffic u lty in id e n tify in g th e sources of th e elem ents. F o r exam ple, in such v a st b asin s as th e P a c ific Ocean (C ronan and Tooms, 1969), th e re m ig h t be a local endogenous supply.
4. The role of c o n stitu e n t supply is an im p o rta n t fa c to r in th o se lake and sea b asin s (B altic, B lack and A rctic Seas) w here fe a tu re s o f ru n -o ff d istrib u tio n essentially control th e g en e ral p a tte r n of sedim entation. In open oceans and in some seas th e re a re com binations o f exogenous and endogenous sources o f ore- fo rm in g com ponents. T he role of endogenous an d volcanic processes is r a th e r evi
d en t in th e fo rm a tio n o f M n-Fe nodules in th e c e n tra l and so u th e rn p a rts of th e P a c ific Ocean (M ero, 1965; C ronan and Tooms, 1969; Skornyakova and A n- drushenko, 1970). The la tte r a re associated w ith volcanic m a te ria ls (b a salts and h y alo c la stite s). T he p ro m in en t p a r t in th e balance of th e se elem ents belongs, probably, to processes of su b m arin e leaching of basic volcanites (V arentsov, 1970) and biogenic tra n sfo rm a tio n s. In 1932, V ern ad sk iy (1960) pointed o u t th a t th ese elem ents w ere p re se n t in th e w a te rs o f open oceans as o rg an ic com
pounds — by-products of th e a c tiv ity of plankton. Jo h n sto n (1964) found th a t m axim um co n cen tratio n of some tra n s itio n a l elem ents occurred in th e a re a s of plankton developm ent — zones of divergence. In m any cases, th e p a r ts o f th e ocean w here th e w a te r m asses co n tain h ig h co n cen tratio n s of th ese elem ents could be c o rrela ted w ith in ten siv e developm ent of nodules on th e floor (S chutz and T u rek ian , 1965).
CON 1. T1 Lam]
sourc 2. Ml More nant Fe ai 3. In lakes, graph form?
faces REFE Bezru]
Sc
Cronai
a s
se Goldbe Ge Johnst ch Manhe me 19 Mero, . Michar Sci Morgai ica Wi Price, 1 dif Schutz, ver Gee Semeno mei US, Skornja Pac Strakho Geo Varenta tera deni Varentsi and lis, Vernads
Aca, Vinograc
402 24th IGC, 1972— SECTION 4 24th IGC
of grow th is in the Baltic im its of sub- ountry rocks ir widely on iw (0.2-3.0 X Dper oxidized f conditions:
mts, the con- ittom w aters, rial of oxide d some other ids, and th e ice with sedi- re sedim ents c abyssal red : composition the su rface
3, 1969) has tion of trace ir form ation, irnessite-rich :eper w aters, i, 1965; M an- waters and composition cated by th e in such v a st ht be a local lake and sea
distribution leans and in irces of ore- s rath er evi- parts of th e
>va and An- (basalts and mts belongs, (Varentsov, pointed out irganic com- 1 found th a t the areas of parts of th e ements could (Schutz and
SECTION 4
CONCLUSIONS
•
1. The d is trib u tio n o f Mn and F e in w ate rs, sedim ents and nodules of E n in g i- L am pi Lake, C en tral K arelia, shows re g u la r and co n sisten t p a tte rn s re lated to source and accum ulation areas.
2. M n-Fe hydroxide nodules and c ru sts occur a t th e w a ter-sed im e n t in te rfa c e..
M ore ra re ly , th e y a re found in th e u p p er oxidized p a r t o f sedim ents. The dom i
n a n t process in th e ir fo rm atio n is selective chem osorption, fix a tio n o f M n and F e and some o th e r tra n s itio n a l elem ents, followed by a u to c ataly tic oxidation.
3. In th is b rie f review o f th e m ain fe a tu re s o f M n-Fe nodule fo rm a tio n in recen t lakes, seas and oceans, i t is assum ed th a t in sp ite o f th e s u b sta n tia l physiogeo- g rap h ical and geochem ical d ifferen ces of th ese basin s, th e model of M n-Fe nodule fo rm a tio n m ay be based on chem osorption a u to cataly tic in te ra c tio n of active s u r
faces w ith com ponent-bearing solutions.
REFERENCES
Bezrukov, P. L., and Romankevitch, E. A., 1970. Sedimentation rates in the Pacific. In Sedimentation in the Pacific Ocean. Nauka, Moscow, 2, p. 228-300.
Cronan, B. C., and Tooms, J. S., 1969. The geochemistry of manganese nodules and associated pelagic deposits from the Pacific and Indian Oceans. Deep-Sea Re
search, 16, (4 ), p. 335-359.
Goldberg, E. D., and Arrhenius, G., 1958. Geochemistry of Pacific pelagic sediments.
Geochim. Cosmochim. Acta, 13, p. 128-212.
Johnston, R., 1964. Sea w ater the natural medium of phytoplankton. Trace m etals and chelation and general discussion. J. Mar. Biol. Assoc. U.K., 44, I.
Manheim, F. T., 1965. Manganese-iron accumulation in the shallow marine environ
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