M INERALO GIA POLON ICA Vol. 32, N o 1, 2001 PL ISSSN 0032-6267
Ewa KOSZOW SKA1, Dorota SAŁATA1
M IN ERALS OF THE HYDROTALCITE GROUP IN METASOMATICALLY ALTERED CARBONATE ROCKS FROM ZAWIERCIE, S POLAND
A b s t a c t . M inerals of the hydrotalcite-manasseite group were identified in sam ples from two borehols in Zawiercie (ZMZ-9, RK-1). The minerals were found in calciphire bodies (RK-1) and in one small, m etasom atic veinlet (ZMZ-9) formed in M iddle Devonian dolom ites. Alteration of dolomitic sedim ents w as genetically connected with infiltration fluids that caused formation of a gam et-pyroxene skam . Inves
tigations have revealed the presence of both hydrotalcite and m anasseite. Besides, in few places of the veinlet there occurs a mineral, which has been recognized as iowaite.
Key-words: hydrotalcite-m anasseite group, calciphires, ska m s, metasomatic veins, Zawiercie, S Poland
IN T R O D U C T IO N
T h e h y d ro talcite g ro u p m in erals b elon g to a larg e g ro u p o f n atu ral an d syn thetic d ih y d ro x id e s n am e d a lso a s "la y e re d d o u b le h y d ro x id e s" or "an io n ic c la y s". Their g e n e ral fo rm u la can be w ritten as: M | 2XM (0 H )2(A m“)x/ mn H2 0 (w here M +2, M+ 3 are catio n s in the h y d ro x id e lay ers an d A m_ is the in terlayer anion ) an d is b a se d on p o sitiv e ly c h a rg e d brucite-like lay ers w ith C 0 3-like an io n s an d w ater m o le cu le s in in terlay er p o sitio n s (D rits et al. 1987) (Fig. la ). W ithin the g ro u p , d e p e n d in g on the c o m p o sitio n o f the o ctah ed ral bru cite-type cationic lay ers, three su b g ro u p s can be d istin g u ish e d in w hich the cation s are:
a) M g+ 2 + A l+3, b) M g+ 2 + Fe+ 3 , c) M g+ 2 + C r+3.
In the su b g ro u p o f the (M g,A l) h y d ro x id e s the 2H (h exagon al) p o ly ty p e is m a n asse ite an d the 3R (rh om bo h edral) is h yd rotalcite. In the su b g ro u p o f the (M g,Fe) h y d ro x id e s the 2H p o ly ty p e is sjogren ite and the 3R p o lyty p e is p yroau rite. The
1 Ja giello n ia n U n iversity, Institute o f G eological Scien ces, D epartm en t o f M in eralogy and P etrograph y , O le a n d ry 2a, 30-063 K rak ow , P olan d ; e m ail: e w a@ in g.u j.ed u .pl; agat@ in g.uj.edu .pl
69
Fig. 1. General structure of minerals of the hydrotalcite group
(A) — the scheme of ordered arrangement of atom s in the layer structural elements (Drits et al. 1987) (B) — the structure of a mineral of the hydrotalcite group with the M g /A l ratio 2:1 proposed by
Arakcheeva et al. (1996)
co rre sp o n d in g m in erals in the su b g ro u p of the (M g,C r) h y d ro x id e s are stich tite an d b arb e rto n ite (A rak ch eev a et al. 1996).
Both hyd rotalcite an d m an asse ite are relatively rare in n atu re. T h e m ajo rity o f oc
cu rren ces o f the m in erals o f the hyd rotalcite g ro u p are asso ciated w ith se rp en tinites, h o w ev er they w ere a lso describ ed from contact rocks (sk am s) an d salin e d e p o sits (Ć em y 1963; Scain i et al. 1967). In P o lan d they h ave been identified in K ło d a w a salt d e p o sit (W ach ow iak 1999), in the contact altered carbon ate rocks in the D ubie area an d in the D ębn ik area (M u szy ń sk i, W yszom irski 1998). M in erals of the h y d rotalcite-m an asseite g ro u p w ere a lso identified in altered carbon ate rocks in Z aw iercie (K o sz o w sk a, S alata 1997a, b). A lth o u g h it is a lm o st a ru le that hyd rotalcite a n d m an asse ite form su b- m icro sc o p ic in tergrow th s, their se p a ra te occurrence is a lso k now n (D rits et al. 1987).
H y d ro talc ite is a scarce ly stu d ie d m in eral, th ou gh it p la y s a sig n ific a n t ro le in cem en t p ro d u c tio n , m etal tech n o lo gy, M g an d A l co rro sio n stu d ie s, an d is an im p o rtan t acid so rb en t an d c a ta ly st (M o ro z, A rk h ip e n k o 1991; C av an i et al. 1991).
S T R U C T U R E O F M IN E R A L S O F T H E H Y D R O T A L C IT E -M A N A S S E IT E G R O U P
B o th 3R a n d 2 H p o ly ty p e s o f m in e ra ls of the h y d ro talcite g ro u p can h a v e a d ifferen t M g / A l ratio. T h e cry stal stru ctu re o f m in erals o f the h y d ro talcite g ro u p w ith the M g / A l
ratio = 2:1, p r o p o se d b y A rak ch e ev a et al. (1996), co n sists o f octah ed ral b ru cite-typ e catio n ic la y e rs in w h ich catio n s (M g,A l) are p resen t. L ay er 1 is of the bru cite type an d h a s the c o m p o sitio n [A lM g2(O H )6], L ay e r 2 is a carb o n ate net of the [ C 0 3] co m p o sitio n , w h e re a s lay er 3 is a n etw ork o f H 20 m o lecu les. The lay er stru ctu ral elem en ts a lo n g the h e x a g o n a l ax is fo rm the se q u en ce - 2 - 1 - 3 - 1 - 2 - (Fig. lb ).
A ll the m in e ra ls g e n e rally con tain only ( C 0 3)2- in their in terlay ers, h o w ev er v a rie tie s co n tain in g ( S 0 4)2-, C L , (O H )’ , ( N 0 3)" an d ( C r 0 4)2- an io n s w ere a lso d e sc rib ed (D rits et al. 1987). E .g. K o ritn in g an d S iisse (1975) d e sc rib ed a h y d rotalcite co n tain in g (O H )- in ste ad o f ( C 0 3)2- an io n s in in terlayers h av in g the co m p o sitio n : [M g6A l2 (O H) 1 6 ] + 2 [ ( 0 H )2-4H20 ] -2. Io w aite, a m agn esiu m -ferric iron o xy ch lo rid e h a v in g the co m p o sitio n M g4( 0 H )8F e 0 C L H20 , w a s d escrib ed b y K o h ls an d R o d d a (1967) (fide D rits et al. 1987).
S A M P L IN G A N D M E T H O D S O F IN V E ST IG A T IO N S
S a m p le s o f v e in lets an d calcip h ires h av e been collected from tw o b o re h o le s ZM Z-9 a n d RK -1, in Z aw iercie (n orth w est of K rak ó w , Fig. 2). M in erals from v e in lets and calcip h ires w e re se p a ra te d b y h an d p ic k in g u n d er a binocular.
M icro sc o p ic o b se rv atio n s o f thin sectio n s w ere p erfo rm ed w ith an A M P L IV A L p e tro g ra p h ic a l m icro sc o p e .
X -ray d iffractio n p o w d e r p attern s w ere o btain ed w ith a P h ilip s diffracto m eter u sin g N i-filtere d C u K a rad iatio n .
T h e m o rp h o lo g y o f m in erals an d their ch em ical co m p o sitio n w ere stu d ie d by m ean s o f a sc a n n in g electron m icro sc o p e (SE M ) JE O L 5410 e q u ip p e d w ith an en ergy d is
p e rsiv e sp e c tro m e te r (E D S) V o y ag e r 3100 (N O R A N ). Fresh su rfa c e s o f rock p ieces as w ell a s p o lish e d thin sectio n s co ated w ith the carbon film w ere exam in ed an d the co n ten ts o f catio n s w ere e v alu ate d acco rd in g to the " s ta n d a r d le ss" p ro ce d u re o f calcu latio n in V o y a g e r so ftw are (i.e. u sin g sta n d a rd s from the so ftw are library su p p lie d by the m an u factu rer).
C h em ical co m p o sitio n o f selected sa m p le s of h yd ro talcites w a s d eterm in ed by m e a n s o f an E D S m icrop rob e ISIS sy stem connected w ith a JE O L JSM 35 scan n in g
Fig. 2. Location of the area investigated
71
m icro sc o p e o p e ra tin g at acceleratin g v o lta g e o f 20 kV an d sa m p le cu rren t o f 30 n A w ith Z A F / F L S co rrectio n s. Biotite (for M g , Si a n d Fe), ch lorite (for A l), a lm a n d in e (fo r C a), rh o d o n ite (for M n an d Z n) w ere u se d a s calib ratio n sta n d a rd s. T h e re su lts a re g iv e n in T ab le 2 w ith all the iron re calcu lated a s FeO .
R E S U L T S
M in erals o f the h y d ro talcite -m an asseite g ro u p w ere fo u n d in calcip h ire b o d ie s, d rille d in the b o re h o le RK-1 in Z aw iercie an d in on e sm all, m e taso m a tic v e in let fo rm ed in M id d le D ev o n ian d o lo m ite s (ZM Z-9, Z aw iercie). B oth o c cu rren ces are g e n e tically co n n ected w ith m e taso m atic g a m e t-p y ro x e n e sk arn a sso c ia te d w ith C u m in eralizatio n .
The m ain c o m p o u n d s of the c a lc ip h ir e s are: n eo m o rp h ic sp aritic calcite, e u h e d ra l p in k or gre en ish sp in e l sensu stricto (as d isse m in a te d cry stals in sp a ritic calcite), m ag - n esio ferrite an d o v al a g g r e g a te s b u ilt m ain ly of fin e-flaky se rp e n tin e s a n d sm a ll a m o u n ts o f ch lo rites, w ith in w h ich o ccu r w ell-p reserv ed sm a ll fra g m e n ts o f forsterite a n d m in erals of the h u m ite g ro u p (K o sz o w sk a 2001).
R e d d ish -b ro w n v e in lets cu ttin g calcip h ires co n sist m ain ly o f forsterite a n d m in e ra ls o f the h u m ite g ro u p . The latter sh o w p le o ch ro ism w ith an ab so rp tio n sch em e: from c o lo u rle ss to yellow a n d from y ellow to o ran ge-y ellow an d re p e ate d tw in n in g. T h ese m in e ra ls in co m p ariso n to fo rsterite are ch aracterized b y an ad m ix tu re o f 5.5 w t.% TiC ^.
F orsterite an d m in erals o f the h u m ite g ro u p are p re se rv e d in v a rio u s d e g re e s. T h ey are often altered into serp en tin e.
M in erals o f the h y d ro talcite g ro u p in the calcip h ires occur in e n v e lo p e s o f sp in e l c ry sta ls (Phot. 1 ,2 ,4 ; F ig. 3) or in sp a c e s a m o n g fractu res o f sp in e ls in a sso c ia tio n w ith ch lorite, serp en tin e, an d so m etim e s bru cite. M icro sco p ical (o p tical a n d electron ) in v e stig atio n s allo w ed to o b serv e the fo llo w in g regu larity: m in erals o f the h y d ro talcite g ro u p form rim s directly aro u n d sp in e l crystals, w h ile o u tsid e o f the h y d ro talcite rim s, ch lorite an d occasio n ally bru cite occur. H ydrotalcite-like m in erals w e re a lso fo u n d a s in clu sio n s in m agn esio ferrite.
T h e m e taso m a tic v e in le t cu ttin g d o lo m ite s is filled w ith ch lorite, fo rsterite, m i
n e rals of the h u m ite g ro u p , serp en tin e, d o lo m ite an d o p a q u e m in erals re p re se n te d by m ag - netite, p yrite an d sm all a m o u n ts o f ch alcopyrite. C h lorite (pen n in ite) o c cu rs in tw o v arieties: a fin e-flaky one, ab o u t 0 . 0 1 m m in size, fo rm s n ests betw een la rg e r flaky cry stals u p to 0.2 m m in size. F orsterite an d m in erals o f the h u m ite g r o u p u n d e rg o alteratio n into serp en tin es.
M in erals o f the h y d ro talcite g ro u p in the vein let o c cu r m o stly in a sso c ia tio n w ith the fin e-flaky ch lo rite. T h ey form " n e s t " a g g r e g a te s su r r o u n d e d b y the co arse -fla k y ch lo rite (P hot. 3, 5) a n d can b e p re se n t in the " n e s t s " alo n e , or in a ss o c ia tio n w ith the fin e-flak y ch lo rite. In b o th o c cu rren ce s they fo rm p la te s u p to 20 p m in siz e , rare ly sh o w in g w e a k ly v isib le h e x a g o n a l h ab it (P hot. 6). A m in e ra l re c o g n iz e d a s io w aite, w h ich a p p e a r s on ly in the v e in let, re v e a ls co m b in atio n o f sh o rt, h e x a g o n a l p rism a n d p in a c o id a b o u t 10 pm lo n g (P hot. 7; F ig . 4), an d is o ften in te rg ro w n w ith se rp e n tin e .
4 5 0 0- 4 0 0 0-
o M9
3500
M C: 0
o
Energy (keV)
F ig. 4. Io w aite c ry stals sh o w in g com bin ation o f short h exagon al p rism s an d p in acoid . SEM im age.
E D S sp ectru m o f iow aite
73
B e cau se it w a s im p o ssib le to se p a ra te the m o n o m in eral h y d ro talcite fraction , fu rth er in v e stig a tio n s w ere carrie d ou t on p o ly m in e ral sa m p le s.
X -ray d iffractio n p atte rn s from o rien ted p re p a ra tio n s o f the in v e stig a te d v e in let (Z M Z-9 125.7a, b) sh o w tw o d ifferen t ty p e s o f b a sa l reflectio n s (7.84, 3.91-3.87, an d 7 .6 6 -7 .6 4 ,3 .8 2 -3 .8 1
A,
etc.) w h at in d icates the p resen ce o f b o th 3R (h y d ro talcite) a n d 2H (m an asse ite ) p o ly ty p e s o f the h y d ro talcite g ro u p (Fig. 5). In the p atte r n s o f c a lcip h ire s, m ain ly reflectio n s o f h y d ro talcite (7 .8 4 -7 .7 6 ,3 .9 1 -3 .8 7A)
w e re id e n tified .M o reo v er, an (M g,F e)-m in eral, w h o se co m p o sitio n is sim ila r to io w aite, h a s b ee n id e n tified in the vein let on ly on the b a s is o f E D S in v e stig atio n s. T h is " io w a it e " a p p e a r s there sp o ra d ic a lly on ly in few p lace s. Its reflection s in the X R D p attern are d iffic u lt to be d isc rim in a te d b e c a u se o f their co in ciden ce w ith reflection s o f oth er m in eral p h a se s, so the p re se n ce o f th is m in eral is tentative.
S m a ll reflectio n s (10.78 an d 11.42
A)
w h ich occur in the X R D p atte rn s o f the v ein let (F ig. 5) can p o in t to the p resen ce o f w o o d w a rd ite (10.90A),
m o u n tkeith ite (11.30A)
orm o tu k o re a ite (11.26
A).
The latter, d e sc rib ed by R o d g e rs et al. (1977), h a s m ain ly an (M g,A l) h y d ro x id e lay er stru ctu re w ith in terlayer su lp h ate an d carb o n ate an io n s a n d w a te r m o le cu le s. B rin d ley an d K ik k aw a (1980) ob tain e d a sim ila r sy n th etic h y d ra te d su lp h ate -h y d ro talcite p h a se w ith a d -sp a c in g o f 11.15A,
w h ile S erw ick a et al. (1996) sy n th e tise d a p h a se in w hich a d -sp a c in g o f ab o u t 1 1 - 1 2A
is co n n ected eith er w ith the o ccu rren ce o f d efect la y e rs re su ltin g from p artia l lo cal d isso lu tio n o f b ru cite sh e e ts (d u e to the in tercalation w ith acid ic h e tero p o ly an io n s), or to the p resen ce o f la c u n a ry K e g g in sp e c ie s o f sm a lle r d im e n sio n s. T h ese m in erals are stru ctu rally re le v an t to m in e ra ls of the h y d ro talcite g ro u p .°2 © C u K a reflection o f hydrotalcite (Hansen, Taylor 1991)
reflection o f m anasseite (PD F 14-0525)
Fig. 5. Fragments of XRD patterns show ing difference in the position of hydrotalcite and m anasseite, in the veinlet (ZMZ-9) and calciphires (RK-1)
Ch — chlorite, S — serpentine
TABLE 1 C ations contents of the hydrotalcite-manasseite group minerals from Zawiercie
(standardless EDS procedure)
Cations per formula unit calculated on the basis of 4 Mg atoms, bold type — averaged amount of Mg, A1 and Fe.
I* — cation composition of iowaite.
7 5
E n e rg y -d isp e rsiv e sp ec tro m e ter a n a ly se s (E D S) h av e re v e a le d th at the m in e ra ls o f the h y d ro talcite g ro u p stu d ie d , excep t M g a n d A l, co n tain Fe a n d sm a ll a m o u n ts o f Ti, Z n a n d sp o ra d ic a lly C a. In their stru ctu re sm a ll q u a n titie s o f a n io n s su c h a s C l"
(0 .0 3 -0 .2 4 /4 M g a to m s ), ( S 0 4)2- (0 .0 1 - 0 .1 5 /4 M g a to m s), (PO4)3- (0.01 / 4 M g a to m s) are a lso p resen t. T h e M g / A l ratio o scillates ab o u t 2:1 (T able 1). T h e h y d ro ta lc ite s stu d ie d d is p la y the A 1/(A 1 + M g + Fe) ratio fro m 0.26 to 0.38 w ith the a v e ra g e v a lu e a b o u t 0.33.
In c o m p a riso n the n atu ral h y d ro talcite from K o z a n i h a s a n A l/ ( A l + M g + Fe) ratio of 0.37 (H all, S ta m a ta k is 2000). B rin d ley a n d K ik k aw a (1979) a n d M iy ata (1980) o b tain e d h y d ro talcite w ith A 1/(A 1 + M g ) from 0.20 to 0.33, w h e re as M isra a n d P erotta (1992) sy n th e sise d sligh tly m o re A l-rich h y d ro talcite s w ith A1/(A 1 + M g ) u p to 0.38. T h e p h a se re c o g n ize d a s io w aite co n tain s in its stru ctu re C l" an d ( S 0 4)2- (F ig. 4).
D IS C U S S IO N A N D C O N C L U S IO N S
A c c o rd in g to the P D F a n d D rits's (1987) d a ta , m a n a sse ite h a s d -v a lu e s o f b a sa l reflectio n s g e n e rally lo w e r than h y d ro talcite b u t th ese v a lu e s can b e in flu e n c ed b y v a rio u s facto rs. O ne o f them co u ld be a p resen ce o f larg e an io n s su c h a s C l", B r_, ( S 0 4)2- in in terlay e r p o sitio n s (M iyata 1983). T h e m in erals in v e stig ate d co n tain a d m ix tu re s of
TABLE 2.
Com parison of the calculated and determined microprobe chemical com positions (wt.%) of the hydrotalcite group minerals
1 — chemical composition of hydrotalcite calculated for ideal form ula of 4M gO • A120 3 • C 0 2 • 9H20 ; 2 — composition o f natural hydrotalcites investigateded by Gastuche et al. (1967);
3-7 — hydrotalcite m inerals from Zawiercie (RK-1 2023).
* Total am ount of C 0 2 + H20 calculated as a difference between the ideal form ula (100%) and the total am ount of oxides.
su c h a n io n s b u t on ly in su b o rd in ate am o u n ts. A d d itio n ally , p ro p o rtio n s o f an io n s flu c tu ate in v a r io u s p la c e s o f a sa m p le an d there is no co rrelation betw een the v a lu e o f b a sa l reflectio n s a n d the a m o u n t o f the an ion s. B e cau se o f that, the p resen ce o f these a n io n s se e m s to h av e n o im p ac t on the v a lu e o f b a sa l reflection s o f the m in erals e x am in e d .
T h e se co n d factor th at co u ld in fluen ce the d -v alu e o f reflection s is the M g / M g + A1 ratio. In v e stig a tio n s o f syn th etic h y d ro c arb o x id e s (G astu ch e et al. 1967) sh o w that a la rg e v a lu e o f the ratio sh ifts m ain reflection s to w a rd s h igh er v a lu e s. In the sa m p le s co n sid e re d , the M g / M g + A l ratio, b ec au se o f its variab ility , se e m s n ot to h a v e a sig n i
fican t in flu en ce on the v a lu e o f reflections.
In X -ray p atte rn s of the sa m p le s from the vein let ex am in ed there a p p e a r tw o in d e p e n d e n t g r o u p s o f reflections, w h ich are ch aracteristic o f b oth h y d ro talcite an d m a n a sse ite (T able 2). T h is co u ld su g g e st that there occu rs a m ixtu re o f m in erals o f the h y d ro talcite g ro u p . In other sa m p le s on ly h y d ro talcite is p resen t.
Fig. 6 . Fragments of XRD patterns of the investigated sam ples
M — mountkeithite, Mt — motukoreaite, W — woodwardite, Ch — chlorite, C calcite, S serpentine 77
C ry stalliz atio n of m in e ra ls o f the h y d ro talcite g ro u p is m o stly co n n ected w ith se c o n d a ry p ro c e ss of serp en tin ite alteratio n (D rits et al. 1987; R am d o h r, S tru n z 1978).
In the calcip h ires in v e stig a te d , the m in erals o f h y d ro talcite g ro u p se e m to b e the p ro d u c ts o f alte ratio n o f sp in e ls [sim ilar p ro c e ss w a s d e sc rib ed b y S tru w e (1958)]. In the v e in let they m ig h t form a s p ro d u c ts o f se rp en tin izatio n o f forsterite in ste a d o f bru cite w h en A l an d Fe io n s are p resen t. The p ro c e ss c o u ld b e e x p la in e d on the b a se o f the fo llo w in g re actio n (D eer et al. 1963):
2 forsterite + 3 H zO = se rp en tin e + b ru cite (h ydro talcite)
Acknowledgement. Sincere thanks are due to Dr. K. Bahranowski (Faculty of Geology, G eophysics and Environmental Protections, University of M ining and Metallurgy) for critical reading and Dr. A. Skow roński (University of M ining and M etallurgy) for corrections of the m anuscript. Special thanks are directed to MSc. A. Latkiewicz (Institute of Geological Sciences, Jagiellonian University), MSc. J. Faber (Laboratory of Electron M icroscopy, Institute of Zoology, Jagiellonian University) and MSc. E. Starnaw ska (Polish G eological Institute, W arszawa) for help in analyses.
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Ewa KOSZOWSKA, Dorota SAŁATA
MINERAŁY GRUPY HYDROTALKITU Z METASOMATYCZNIE ZMIENIONYCH SKAŁ WĘGLANOWYCH Z ZAWIERCIA
S t r e s z c z e n i e
M in erały z g ru p y h y d ro talk itu -m an asse itu zid en ty fik ow an e zo stały w próbk ach p o ch o d z ący ch z d w u otw o ró w w iertn iczych z Z aw iercia (ZM Z-9, RK-1). W ystępują on e w kalcyfirach (RK-1) g d z ie p o w stały w w yn iku p rzeo b raże n ia sp in eli i w m eta- so m aty czn e j ży łce (ZM Z-9), w której ich obecn ość w iąże się z p rocesem serp en tyn izacji fo rstery tu . Stw ierd zo n o , że w k alcyfirach d o m in u jącą fazę stan o w i hyd rotalkit, p o d cz a s g d y w ży łce w y stę p u je m ieszn in a h yd rotalkitu i m an asse itu . S to su n ek M g:A l w b a d a n y c h m in erałach je st zm ien n y i w ah a się od 1,4:1 d o 2,4:1. P oza glinem i m a g n e z e m w m in erałach tych w y stę p u ją niew ielkie do m ieszk i Fe, Zn, C a, Ti, C l', ( S 0 4)2-, (PO4)3". W m etasom aty czn ej żyłce stw ie rd zo n o obecn ość m in erału m agn e- z o w o -ż e la z o w e g o o sk ła d z ie o d p o w iad ający m iow aitow i.
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Phot. 1. M in e rals o f the h y drotalcite g ro u p an d chlorites rep lacin g sp in e l cry stal (calcip h ire s, RK -1).
Plane p o larise d light
Phot. 2. M in erals o f the h y d rotalcite g ro u p a n d chlorites rep lacin g sp in el cry stal (calcip h ires, RK -1).
C ro sse d p o la rs
E. K O SZ O W SK A , D . S A L A T A — M in erals o f the h y d rotalcite g ro u p in m eta so m a tically altere d carb on ate rocks from Z aw iercie, S P olan d
M IN E R . P O L O N . V ol. 32, N o . 1, 2001
Phot. 3. A m ixtu re o f a fin e-flaky chlorite an d m in erals o f the h ydrotalcite g ro u p w ithin a coarse-flaky chlorite (the veinlet, ZM Z-9). C ro sse d p o lars
Phot. 4. A lteration o f sp in e l into chlorite and h ydrotalcite from m argin s o f cry stals (calciph ires, RK-1).
SEM im age
E. K O SZ O W SK A , D. S A L A T A — M in erals o f the hydrotalcite g ro u p in m etasom atically altered carbonate rocks from Z aw iercie, S Poland
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P hot. 5. H yd rotalcite-ch lorite a g g re g a te s w ithin a coarse-flak y ch lorite (the v ein let, Z M Z -9). SEM im ag e
Phot. 6. Fine flak es o f h y drotalcite (the veinlet, ZM Z -9). S E M im age
E. K O SZ O W SK A , D. S A L A T A — M in erals o f the h y d rotalcite g ro u p in m eta so m a tically altered carb on ate rocks from Z aw iercie, S P olan d
M IN E R . P O L O N . V ol. 32, N o . 1, 2001
Phot. 7. P en etration twin o f iow aite (the veinlet, ZM Z-9), SEM im age
E. K O SZ O W SK A , D. S A L A T A — M in erals o f the hydrotalcite g ro u p in m etasom atically altered carbonate rocks from Z aw iercie, S Poland
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