A N N A L E S S O C I E T A T I S G E O L O G O R U M P O L O N I A E R O C Z N I K P O L S K I E G O T O W A R Z Y S T W A G E O L O G I C Z N E G O
v. 51—1/2: 133—151 K ra k ó w 1981
Ksenia M o c h n a c k a , M aria S a s s - G u s t k i e w i c z
THE METASOMATIC ZINC DEPOSITS OF THE POMORZANY MINE
(CRACOW— SILESIAN ORE DISTRICT, POLAND)
(5 Figs and PI. I—IV)
Metasomatyczne złoże rud cynku z kopalni Pomorzany (rejon śląsko-krakowski)
(PL I— IV i 5 fig.)
Ksenia M o c h n a c k a , Maria S a s s - G u s t k i e w i c z : T he m etasom atic zinc deposits of the Pom orzany Mine (C racow -Silesian ore district, Poland). Ann. Soc.
Geol. Poloniae, 51— 1/2: 133— 151. 1981 Krakow.
A b s t r a c t : Based on the observations in the m ine w orkings the zinc portion of the Pom orzany m ine is described. The m etasom atic origin o f the deposit is dem onstrated by geological structures, by m acrostructures inherited from paleo- some, and by m icroscopic iexaminations. The ore body reveals several processes:
dolom itization, ore replacem ent, and karstification. It appears that the karst lead and zinc part of the deposit w a s form ed after that of the m etasom atic ore body.
K e y w o r d s : m etasom atic Zn—Pb ores, Cracow—S ilesian region, Poland.
K senia Mochnacka, Maria Sass-G ustkiew icz: In stytut G eologii i Surow ców M ine
ralnych, A kadem ia G órniczo-H utnicza im. St. Staszica, Al. M ickiew icza 30, 30-059 Kraków
M anuscript received: April, 1980 accepted: May, 1980
T r e ś ć : Przedstaw iono opis złoża cynku kopalni Pom orzany. Jego budowa geologiczna, m akrostruktury rud oraz ich m ikroskopowe cechy świadczą o m eta- som atycznym pochodzeniu om aw ianego złoża. Złoże ujaw nia w p ły w dolom ityzacji, m etasom atycznego zastępow ania oraz procesów krasow ych. Stw ierdzono również, że brekcjow e złoże cyn k ow o-ołow iow e utworzyło się w w ynik u procesów kraso
wych; po pow staniu m etasom atycznego złoża cynku.
INTRODUCTION
In the Pom orzany Mine, tw o types of deposits are observed: 1 — the banded and spotted zinc ores sim ilar to those described by Bogacz et al.
(1973), Sm olarska (1968), and Sobczynski, Szuw arzynski (1974) from the Chorzow area, and 2 — the lead — zinc ores in solution collapse brec
cias. This p a p e r deals only w ith the first type, i.e., the m etasom atic ore body and its relation to the breccia type. The problem concerning the k a rst ores w ill be a subject of the forthcom ing paper.
GEOLOGICAL SETTING
The Pom orzany ore deposit is located in the carbonate rocks of Low er M uschelkalk (Anisian). The Triassic and P erm ian sediments over
lap transgressively the folded and eroded Paleozoic basem ent. The host rock is an ore-bearing dolomite — a neosome produced by dolomiti- zation of lim estone and recrystallization of the early diagenetic dolo- stone (for references see Bogacz et al. 1975). The m ain volume of the ores coinicides w ith low erm ost p a rt of th e dolomite bodies. The bottom p a rt of the deposit described here is found in the ore-bearing dolomite which corresponds to so-called interform ational conglomerate of th e Gogolin Beds (Table 1).
T a b l e — T a b e l a 1 Stratigraphic position of the exam in ed fragm ents of ore bodies
Pozycja stratygraficzna badanych fragm entów złoża na tle schem atycznego profilu dolnego w apien ia m uszlow ego
K archow ice Beds T erebratula Beds G órażdże Beds
Mla W ellenkalk III
QJ
7 j Inter-W ellenkalk Beds
OC/1 W ellenkalk II
2 Conglom erate horizon
0)> Gogolin Beds Porous L im estone
>o
, 1 Lim estone w ith Pecten and D adocrinus (higher
part)
W ellenkalk I
Lim estone w ith P ecten and D adocrinus (lower part)
stratigraphic-position of the ore bodies
— 135 —
The carbonate host rocks are essentially horizontal and are cut by num erous faults am ong w hich the latitu d in al ones are th e m ost im portant. They produced the m ain horsts and grabens. The Pom orzany ore body occurs generally in a large graben and is separated from the Olkusz deposit by a horst stru ctu re. In the tectonic zones, the deposit is cut and displaced together w ith rigid blocks of surrounding rocks.
The ores are scattered in form of a nest-like bodies throughout the mass of the ore-bearing dolomite. The horizontal ex ten t of most nests is m uch greater th a n the vertical one. Some of them take a regular, iso
m etric shape; others form ta b u lar lenses. The la tte r ones usually consist of banded and spotted ores, w hereas the nestlike ore bodies comprise m ineralised breccia. These breccias represent the solution-collapse type analogous to those observed in the neighbouring Olkusz deposit (Sass- -Gustkiewicz, 1974, 1975). The banded and spotted ores resulted from the replacem ent of carbonate rocks by ore m inerals. These m etasom atic ores constitute a m inor p a rt of the Pom orzany deposit.
SURROUNDING ROCKS
The sourrounding carbonate rocks differ in th e ir stru ctu re s and te x tures. Several types of dolomites, limestones, and dolomitic limestones have been distinguished. In the vertical profile, we can observe a tra n sit
ion from one to the other stru c tu ra l type of limestones affected by the variation of depositional environm ent. The ch aracter of the rock stru c tu res and their variability points to th e ir form ation in a shallow sedi
m e n tary basin.
A considerable variability of stru ctu res can be also observed in the ore-bearing dolomite. This is caused by the fact th a t some of the stru c
tu res w ere inherited from paleosome. Figs. 1 and 2 are good examples of such inheritance. The same rock stru ctu re s can be seen on both sides of the metasom atic contact of limestone and ore-bearing dolomite. How
ever, the continuation of structures from one to the other rocks is not always precise. F o r examples 1 — coarse crystalline, organogenic lim e
stones and some of the spotted ones w ere altered to spotted dolomite, and 2 — grey, sm ooth limestones to coarse crystalline, p a rtly lam inated dolomite.
The stru ctu res of the ore-bearing dolom ite are m ore varied th a n those of th e limestones. This is probably resulted from several processes involued in the m etasom atosis such as: dolomitization, recrystallization, and dissolution. However, most of the well-developed structures of p a
leosome are reflected in the ore-bearing dolomite neosome (Table 2).
T a b l e — T a b e l a 2 Petrographic description of surrounding rocks
Petrograficzna charakterystyka skał otaczających Structure/texture
of rocks L im estones D olom ites
1 2 3
Homogenous, fine-grained
Grey, smooth, m icrosparitic lim estone, partly clotted, re
crystallized m icrofossills are visib le
Hom ogenous grey dolom ite.
M icroscopically: equicrystal- line, idiotopic, (or xenotopic), locally porous. Ore m inerals fill th e in tercrystalline sp a
ces. R ecrystallization of dolo
m ite is partly observed.
C oarse-crystalline organogenic
Grey, corse-crystalline, partly spotted lim estone. Carbonate fossils (m ainly Crynoides) are observed in fin e-cry sta llin e m atrix. Features of recrystal
lization and dolom itization.
Grey, coarse, crystallin e dolo
mite, w ith stylolites. M icro
scopically: composed of h y - pidiom orphic crystals of dolo
m ite (0,05—0,16 mm). O ften the dolom ite grains m im ic the shapes of Crynoides, featu res of recrystallization. S ty lo lites common.
Lam inated and/or banded
Light grey lim estone w ith dark lam inae. Composed of m icritic or m icrosparitic car
bonate m aterials, lam ination is accentuated by the presence of m icritic lam inae separated one from another by m icro
sparitic one and clay m in e
rals. Scattered dolorhombs point to initial stages of dolo
mitization.
Light grey w ith dark la m i
nae. M icroscopically: coarse crystalline, idiotopic dolom ite.
The iron hydroxides under
line the outline of dolom ite rhombohedra. N on-transm it- ted m inerals are also accu m ulated in the outher zones of dolom ite grains.
Recurring, 1
spongy-like
Grey, coarse-crystalline, rhyt- m ically-porous dolom ite.
Spongy-lik e structure appears as porous, alongated zones, parallel to each other.
Spotted Spotted lim estone is light grey w ith darker lam inae and irregular spots. U su ally in the inner part of spots coarse crystalline calcite is visible. M icroscopically: m i
crosparitic, non equigranular lim estone, in som e places clotted. Irregular m icritic clots, or m icritic lam inae and
Spotted dolom ite is grey w ith lighter irregular spots, w h ich som etim es show porous inner parts. M icroscopically: coarse- -crystallin e rock, hipidiotopic w ith fin er-crystallin e areas.
The porous zones are m id d le- crystalline xenotopic, affected by recrystallization. N um erous cavities are partly filled w ith
— 137 —
1 2 3 I
num erous recrystallized m i
crofossils are present. Dolo- m itic rhombohedra are accu
m ulated near clay intercala
tions and stylolites. This type of lim estone w as found in the v icin ity of lim estone/dolom ite contact, or in boundary zone betw een organogenic and lig h t gray, smooth lim estone.
idiom orphic crystals of dolo
m ite, showing typical zone structure. Som etim es the po
res are filled w ith sphalerite.
Spotted-lum p S potted-lum p lim estone is ligh t-grey w ith darker spots and is characterized by irre
gular interfaces. M icroscopic
ally: m icritic, partly m icro- sparitic rock contain disse
m inated crystals of dolomite.
Lum py structure appear as irregular, rounded spots, f il
led w ith coarse crystalline calcite. C alcite partly rep lac
ed by dolomite.
S p otted-lum py dolom ite is grey w ith irregular lighter spots. M icroscopically it is m id d le-crystallin e dolom ite w ith coarse crystalline spots.
Features of recrystallization are common. S tylolites filled w ith iron-hydroxides sepa
rate coarse and m iddle-cry
stalline parts of rock.
Intraform ational conglom erate
The conglom erate is com pos
ed of grey, m icritic lim estone pabbles cem ented by lighter, coarse-crystallin e organodet- ritic (m ainly Crynoides) lim e
stone. M atrix contains a few clastic grains of quartz and rounded barite concentrations.
C onglom erate composed of grey, coarse-crystalline, non equigranular dolom ite which form s pabbles cem ented by fin ecrystallin e lim estone. Both rocks are in som e places a f
fected by recrystallization.
THE CONTACT RELATION OF THE ORE-BEARING DOLOMITE A ND LIMESTONE
The contacts betw een the ore-bearing dolomite and limestone appear to be sim ilar to th a t described by Bogacz et al. (1972) in Trzebionka Mine and by Mochnacka, Sass-Gustkiewicz (1978) from the Olkusz de
posit. These are irre g u lar and cross-cut the bedding planes. The contact is w ell-m arked and accentuated by differences in colour and te x tu re of rocks. Often it is additionally accentuated by some am ounts of clay m inerals. In some cases, however, there occurs a gradual transition from the ore-bearing dolomite to limestone. B ut th e boundaries betw een the two rocks are always of cross-cutting character.
' A ^ - ~ /
0 1.0 m si'-" \
tf:-.
&7T&2 » » * 4 8 ^"^-5 « ^ 6 r i 7
Fig. 2. Cross section of a portion of ore body near the m etasom atic contact of ore-bearing dolom ite w ith lim estone. 1 — ore-bearing dolom ite, 2 — lim estone, 3 — clays, 4 — banded and spotted ores, 5 — lam inated rocks, 6 — conglom eratic
rocks, 7 — exam p les show on photographs
Fig. 2. Przykład w yk ształcen ia złoża w pobliżu m etasom atycznego kontaktu dolo
m itów kruszconośnych z w apieniam i. 1 — dolom it kruszconośny, 2 — w apień, 3 — iły, 4 — ruda o strukturze w arstw ow an ej i plam istej, 5 — skały o strukturze lam inow anej, 6 — sk ały o strukturze zlepieńcow ej, 7 — przykłady struktur rudnych
przedstaw ione na fotografiach
The geom etrical configurations of the contacts over short distances are very irregular, even w hen the contact is n early horizontally. In some cases th e lim estone-dolom ite boundary is w avy (Figs. 1 and 2), in others it is thooth-like (middle p a rt of Fig. 1). In the low er p a r t of the m ain dolomite body, there is an interm ediate zone of incomplete dolomitization. In this zone are some alongated relics of limestones, p arallel to the bedding planes.
One can see th a t this zone (Fig. 1, left side) is transform ed into a ta b u la r dolomitic body developed on both sides of th e bedding surfaces of the paleosome. The dolomite body is isolated from the u nder- and over-lying lim estones by th in black layers of clay m inerals. The presence of these two clay screens has brought about a forced horizontal flow of dolomitizing solutions w hich resulted in the form ation of a ta b u lar body.
Both these facts: 1 — the cross-cutting contact of the sedim entary interfaces, and 2 — the presence of unaltered relics of limestones point to the m etasom atic origin of the ore-bearing dolomite (compare Bogacz et al. 1972 and 1975).
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THE METASOMATIC ORE BODIES
As it has been said before the m etasom atic ore-bodies assume mostly a ta b u la r shape. T heir horizontal extention is several tens of m eters, . up to hundreds of m eters, while th e ir vertical ex ten t ranges from 0.5 to 3 m eters. This quite reg u lar shape is disrupted in a few places by a rapid increase of thickness which has form ed local nests of banded and spotted ores. The height of these nests exeeds m any tim es the average thickness of th e ta b u lar body and m ay even reach 30 m eters.
The tabular, horizontally disposed ore bodies if observed from nearb y are irregular. Their boundaries cross the sedim entary bedding planes of surrounding rocks. This is the re su lt of the selective replace
m ent of the ore-bearing dolomite. Consequently, the bottom of the m etasom atic ore bodies coincides w ith the bottom of the ore-bearing dolomite.
The m etasom atic ore bodies are not uniform in th e ir inner com
position. They contain irreg u lar accum ulations of massive sphalerite ores surrounded by w eak im pregnetions of sphalerite w ith preserved fragm ents of b a rre n dolomite. Usually, th e re are some differences be
tw een the character of the bottom and the roof of the ore body. In the roof zone, the concentrations of ore m inerals decrease step-like w ith distance from the ore body, while the bottom is sh arp ly defined and accentuated by the presence of clays. F igures 1, 2 and 3 illustrate some selected fragm ents of a m etasom atic ore body.
Fig. 2 represents a section through the m arginal p a rt of the ore body.
The following rock stru ctu re s can be distinquished in the limestone and in the ore-bearing dolomite: lam inated, spotted, and recurring spongy. The contact betw een th e lim estone and th e ore-bearing dolomite is of a m etasom atic type. All th e sedim entary stru ctu re s continue from lim estone to dolomite w ithout any changes at the cross-cutting boundary betw een them . Along this contact, some am ounts of clay m inerals were accum ulated. Small, irregular, sphalerite and m arcasite nest-like bodies are developed exclusively in the ore-bearing dolomite and term inate a the contact w ith th e limestones.
In the lam inated layer of the ore-bearing dolomite, there banded ores have been form ed (PI. I, Fig. 1). Above them , in the layers of spotted dolomite, th e re are concentrations of spotted ores (PI. Ill, Fig. 3). In both cases, the ores reflect the p ettern s of the host rocks.
The concentrations of massive ores are surrounded w ith im pregnation haloes. Of these tw o ore m inerals, the sphalerite is older th a n the m arcasite. The la tte r fills the open spaces resulting from the m eta- somatosis and also replaces the sphalerite.
L et us re tu rn to Fig. 1. Above the zone of incomplete dolomitization, described earlier in this section, in the complex of ore-bearing dolomites,
there is the m arginal p a r t of a typical ta b u la r ore body. Its thickness ranges w idely b u t decreases tow ards th e distal end (on the right of the picture). In spite of its ta b u la r shape, th e ore body is not bedding controlled.
The ore body consist of two different, overlapping, horizontally disposed elem ents. The u p p er one is composed of m etasom atic ores and the low er one is made up of the internal sediments. As usual, the roof of the m etasom atic ore body has an irre g u lar shape th a t cross-cuts the bedding, b u t the sm all sedim entary stru ctu res are repeated, re su lt
ing in banded and spotted ores. Their distribution is visible in Fig. 1.
The upperm ost p a rt of the m etasom atic ore body is a zone of irregularly disposed im pregnations.
Between the rich, massive ores and the im pregnation zones, there is a gradual transition. The sample show n on PI. I, Fig. 2, shows the transition zone in w hich the banded ores are of low concentration.
The lam inated dolomite is im pregnated by sphalerite grains. The bedd
ing planes are solutionally widened, producing narrow , sheet-like open spaces. These voids are incrusted by light brow n and d ark brow n sphalerite. The distribution of ore m inerals suggests th a t the solution
ally enlarged voids w ere the places from which the replacing solutions have spread outw ards into the host rock (compare also Bogacz et al.
1973 and Dzulynski, Sass-Gustkiewicz 1977).
The bottom of the m etasom atic ore body rests on the intern al sediments. T heir thickness differs according to the irregularities of the irreg u lar bottom surface. This surface shows a typical karstic morphology w ith solutionally rounded forms covered by black residual clays. The internal sediments consist of d e trita l grains of the s u r
rounding carbonates, clastic and euhedral sulfide grains and residual clays. The sedim ents also contain fragm ents of dolomite and m e ta
somatic ores. The in ternal sedim ents show a lam ination th a t often reveals soft-rock-deform ations. The am ount of ore m inerals is great enough to call them stratified sedim entary ores.
The above presented twofold ore body has been affected by two different ore form ing processes, i.e. m etasom atosis and dissolution joined w ith in te rn a l karstic accumulation. The nearly horizontal bottom of the m etasom atic ore body suggests th a t the dissolution of underlying rocks preceeded very slowly and to g eth er w ith the deposition of in
tern al sediments, w hich protected th e m etasom atic ore body from collapse. However, th e presence of m etasom atic ore fragm ents in the internal sedim ents indicates th a t the karstic processes developed a fte r the em placem ent of m etasom atic ores. This relationship is evidenced more obviously in the following p ictures (Fig. 3) th a t show a section through th e central p a rt of the ore body. The complex of the Gogolin limestones (lower part) and the ore-bearing dolomites (upper part) lies
— 141 —
horizontally. As usual, the contact betw een the two types of rocks cuts across the bedding planes, which are more clearly m arked in limestones th an in dolomites. In the ore-bearing dolomites, the irregular concen
trations of m etasom atic ores can be observed. They represent the same type of banded ores described above, composed m ainly of sphalerite followed by m arcasite.
B eneath the ore body, th e re are two elongated in the vertical direction breccia zones. The sm aller one (on th e right in Fig. 3) is' developed in lim estone beds only and the overlying dolomite strata are not disturbed nor even fractured. The bigger one (on the left of the picture) involves also the ore-bearing dolomites, thus in the breccia, we can find clastic fragm ents of the overlying m etasom atic ore body.
The spaces between th e large breccia fragm ents are filled w ith small clastic particles of the surrounding rocks and the internal sediments.
Both breccia zones are a type of solution-collapse breccias w ith an uncollapsed roof. T here is a la teral transition from the proper breccia to the unbrecciated dolomite layers through breccia w ith little displace
m ent and rotation of blocks which is typical of collapse stru ctu res (compare Sass-Gustkiewicz 1974). Moreover, the surface of the lim es
tones shows signs of dissolution.
The above-m entioned breccia zone shows a certain assym etry in the distribution of lim estone and ore-bearing dolomite beds on both sides of the breccia zone. Because of the lack of disturbance in the overlying dolomite and because the same layers of limestones are traceable on the sam e level on both sides of breccia, th e assym etry cannot have been affected by any vertical displacem ent. This relation
ship m u st have been caused by a prior assym etric configuration of the m etasom atic contact betw een th e lim estones and the dolomites th a t prom oted the dissolution processes. Thus, the presence of ore fragm ents in the solution collapse breccia indicates th a t the karstic processes developed afte r the em placem ent of sphalerite and m arcasite in the banded ores.
INHERITED AND/OR DIFFU SIO N ORE STRUCTURES
Betw een the ore structures, there is a group of large-scale stru ctu res th a t show a striking sim ilarity to the m acrostructures of the host rocks.
To explain this sim ilarity, a specific la y er w as selected in which a transition from lim estone through ore-bearing dolomite to th e ore is visible over a sh ort distance. F our m ain types of stru ctu res w ere differentiated, th a t is: banded, repeated spongy-like, spotted, and organo
genic occuring as w ell in limestones, in ore-bearing dolomite as in ores
(compare Table 2). The pictures in P lates II and III show two m acro
structures: repeated spongy-like and spotted w hich were observed in all these rocks.
Microscopic exam inations have led to the conclusion th a t the m ain reason for th e recurrence of these stru ctu re s during all th e steps of m etasom atism was the differences in solubility. Hence, we m ay conclude th a t some of the m acrostructures w ere inherited from the paleosome (see also Bogacz et al. 1973).
A part from the doubtlessly inherited ore stru ctu res th e re are the banded and spotted stru ctu re s w hich do not reflect the p rim ary stru c tures. They developed probably independently of the structures of the host rocks. It m ay be added, a t this point, th a t Bogacz e t al. (1973) describing sphalerite m etasom atic banded ores in Trzebionka Mine has pointed to th e “irregularities and deviations from p rim ary p a tte rn s ” among th e inherited structures.
Comparison of these irregularly banded ores w ith the rhy th m ic ore structures obtained by Pospelov (1973) from experim ents on the form a
tion of the so called “fissureless veins” reveals a close sim ilarity. These experim ental rhythm ic ore stru ctu res w ere affected by a reverse dif
fusion of components, w hich sim ilarly to the wave phenom ena are subjected to diffraction, interference, and wave deflection in the stream of diffusion. Because diffusion is an im portant factor in the spreading of m ineralizing solutions, it seems reasonable to assume th a t the stru ctu res obtained from experim ents are com parable w ith these observed in a real ore body and th a t the irregularities and deviations from the p rim ary structures m ight be explained as a resu lt of dif
fraction, interference, and deflection of waves during the reverse diffusion of the m ineralizing solutions.
The coexistance of inherited and non-inherited stru ctu res in one simple ore-body is in agreem ent w ith the observations made in m any other typical m etasom atic ore deposits and can be explained in term s of th e paradoxes of metasomatosis.
MICROSCOPIC EXAM INATION OF THE METASOMATIC ORES
The sphalerite 1 ore replaces a m etasom atically altered, coarse cry stalline dolomite. The ore consists of idio- or hipidiom orphic grains of dolomite (0.05—0.3 mm) and sphalerite. The sphalerite occurs in form
1 For sim p licity ’s sake, ZnS occuring in all types of accum ulations has been nam ed sphalerite. It is know n how ever (Chu-Tuan-Nha, Kubisz 1973) that ZnS from P olish Zn—Pb deposits contains som etim es up to 10% of hexagonal w urtzite.
D etailed m ineralogical exam inations are not the aim of this paper.
— 143 —
of dispersed grains or irre g u lar aggregates. Usually, the size of spha
lerite and dolomite crystals is sim ilar or the fo rm e r is som ew hat smaller.
(Fig. 4— 1).
According to microscopic observations of th in sections, a few steps of successive replacem ent of dolomite b y sphalerite can be distinquished.
In th e first step, th e sphalerite grains are d istributed around the larger grains of dolomite or form rings around th e dolomitic aggregates. The next stage was th e form ation of sphalerite nests containing dolomite crystals w ithin th e ir meshes. The last stage appears to be the massive sphalerite aggregates containing single, well-developed centrally located dolorhombs (Fig. 4— 2, 3 and PI. IV, Fig. 4). Sim ilar m icrostructures of sphalerite are observed in the vicinity of vugs incrusted by sphalerite (PI. I, Fig. 2).
The sphalerite occuring as dispersed grains belongs to the oldest generation — I. It originated concurrently w ith the recrystallization of dolomite or a little later; this is suggested by th e coarse crystalline idio- topic stru c tu re of dolom ite containing sphalerite I. The massive aggre
gates of sphalerite are composed of sphalerite II. Both, I and II gene
rations of sphalerite exam ined in transm ited light are gray, light brow n w ith high refractive index, isotropic or p a rtly anisotropic. Sphalerite II occurs in com pletely recrystallized ore-bearing dolomite. It consists of well developed dolorhombs. Staining m ethods using alizarin red S and potassium ferricyanide reveal irre g u lar ankeritic zones of dolomite cry
stals. The dolorhombs show replacem ent by sphalerite II.
In the porous p a rts of th e rock (e. g. in spotted and spongy dolo
mite), the sphalerite occurs as a filling of pores. The dolomite crystals growing in the open spaces have a typical concentric zonation. The outer zones are ankeritic (unlike th e dolorhombs form ing the ore-bearing dolo
m ite in w hich th e ankeritic zones are the ones before th e last). The different forms of dolom ite crystals seem to correspond to the different stages of dolomitization. The crystals of dolomite I are low-iron w hereas the dolomite II crystals filling open spaces contain the outer ankeritic zones.
Well-developed dolorhombs show the evidences of dissolution which starts from the inner p a rt of crystals. These voids w ere filled w ith fine crystals of dolomite or sometimes of sphalerite (see Fig. 4— 5 and PL IV, Fig. 3). More intensive dissolution and tran sfer of liquids prom oted the enlargem ent of voids, which were succesively filled w ith colloform sphalerite of the I lia generation (Fig. 4— 4). As is shown in Fig. 4—4, the aggregates of sphalerite II are covered w ith th in layers of sphalerite of indistinct structure. The colloform sphalerite III forms the next zone and is b u ilt up of altern ate ly repeated bands of light-honey and dark - -brow n bands of sphalerite. Longitudinal crystals growing perpendi
cularly to the nucleation surface cut across several bands. The next
Fig. 4. Form y w ystępow an ia sfalerytu w sJaaii miikxoskioipoiwej: a — dolomit, b — kalcyt, c — sfaleryt, d — siarczek żelaza
— 145 —
v ariety is white, crystalline sphalerite Illb (Fig. 4— 4 and 5, 6). All stru c tu ra l varieties of sphalerite discussed above originated as th e filling of open spaces (Fig. 4— 4, 5, 6, 7, 8). However, it should be noticed th a t the aggregates of sphalerite II indicate the traces of recrystallization, and th e y mimic collomorphic stru ctu re s (Fig. 4— 3).
The F eS 2 exists as: a) cem ent of sphalerite grains (Fig. 4—9, 10), b) irre g u la r pore filling, c) in form of aggregates w hich cover the collo
form sphalerite and p a rtly replace it (Fig. 4— 11).
A SCHEME OF METASOMATIC PROCESSES
The scheme presented in Fig. 5 shows the developm ent of m eta
somatic processes in the Pom orzany deposit. Its construction has been based on microscopic exam inations of rocks and ores. However, the tim e relationship of these processes is based on the observation on the m acro- and mesoscale.
The m etasom atic processes altered the limestone only, because in opposition to other deposits of this region, no early diagenetic dolomite occured here.
The dolomitization of limestones was the first geological process (cal
cite I — area 1) which affected the origin of dolomitic limestone (dolo
m ite I — area 2). Locally, in the same th in sections, evidences of recry
stallization or calcitization of single dolorhombs (calcite II — area 3) w ere observed. The dolomitization of lim estone caused the form ation of dolostone, which consists of dolomitic grains only (dolomite I — area 4). The la tte r stage of the metasom atic processes is the recrystalli
zation of dolomite (dolomite II — area 5). The coarse-grained, idiotopic, p a rtly hipidiotopic dolostone is the resu lt of the above described p ro cesses.
Dolomitization is associated w ith the dissolution of rocks and con
sequently w ith th e developm ent of caverns. These caverns are then p a rtly filled w ith th e idiotopic dolorhombs, showing concentric stru ctu re (dolomite Ila — area 6).
The form ation of dolomite I was accompanied by the deposition of th e first generation of sphalerite (sphalerite I — area 7). The dissemi
nated iron sulfides (pyrite I) probably were produced at the same time.
The successive enrichm ent in ZnS resulted in the form ation of sphalerite aggregates (area 8) located in th e idiotopic coarse-graine dolomite. The dolomite rhom boedra occuring in these aggregates seem to be the relics of dolomite, which were not replaced by sphalerite. This is evidenced by th e transition zones, showing succesively g reater density of the sphale
rite aggregates. The well-developed dolorhombs are characterized by
10 — R o c z n i k P T G 51/1—2
s 5 > G E 9 C S 10
Fig. 5. Schem e of m etasom atic processes: 1 — calcite, 2 — dolom ite, 3 — ankeritic zones, 4 — dissem inated grains and aggregates of sphalerite, 5 — colloform spha
lerite, 6 — w h ite crystallin e sphalerite, 7 — iron sulfides, 8 — galena, 9 — supplied elem ents, 10 —rem oved elem en ts
Fig. 5. Schem at procesów m etasom atycznych w złożu. 1 — kalcyt, 2 — dolomit, 3 — strefy żelaziste, 4 — sfaleryt rozproszony oraz w form ie im pregnacji, 5 — sfaleryt kolom orficzny, 6 — sfaleryt krystaliczny biały, 7 — siarczki żelaza,
8 — galena, 9 — pierw iastki doprowadzone, 10 — p ierw iastk i odprowadzone.
special resistance to replacem ent. The dolomite II was form ed at the same time. U sually it contains the ankeritic areas in the inner p arts of rhom boedra (area 9).
The dissolution was the n ex t im portant process associated w ith th e m etasom atism . It is the dissolution of dolomite rhom bohedra th a t show concentrically banded stru c tu re (dolomite lib) w hich was p a rtly replaced
— 147 —
by sphalerite (area 9). The m arcasite III infilling the pores was formed in th e same time.
The form ation of colloform accum ulation of sphalerite (Ilia) followed the recrystallization of sphalerite II. The differences in th e stru ctu re and colour of the colloform sphalerite and crystalline I and II suggest changes in chemical composition of oreform ing solutions (area 10). W ith
in th e colloform sphalerite idiomorphic crystals of galena often are visible (area 11), this galena replaces the sphalerite. However, galena occurs in small am ounts and does not seem to be typical com ponent of m etasom atic ores. In the same picture (area 11), w hite grains of spha
lerite I llb are shown. They cover the colloform sphalerite I lia or occur in calcitic veinlets cutting them.
Among the discussed ore m inerals, m arcasite IV and V are the youngest one (area 12). The m arcasite is characterized by radial struc
tures of crystals and strong anisotropy. It also shows th e features of replacem ent.
We m ention a t this place, th a t Przeniosło (1974) also suggested the existence of successive gradual transform ations of the dolomite which
led to the appearance of m etasom atic ores.
FIN AL REMARKS
As a result of above-described investigations a n um ber of conclusions concerning the composition, development, and the origin of the Pomo
rzany deposit h as been reached. The conclusions are as follows:
1 — two genetic types of deposits can be disitmiguished:
— m etasom atic ores composed of sphalerite, and
— filling of em pty voids in collapse breccias by lead and zinc minerals.
2 — th e host rock is the ore-bearing dolomite. Its epigenetic character has been concluded from contacts w ith limestones and from micro
scopic exam inations of rocks
3 — the m etasom atic ore bodies are m ostly stratiform . In some cases, th e ir thickness rapidly increases in m an y places and at m any tim es 4 — despite the layered form of the m etasom atic ore bodies, detailed exam ination reveals th a t th e ir irre g u la r shapes crosscut the sedi
m entary structures
5 — the m etasom atic deposits resulted from the following processes succeeding one afte r th e other:
— dolomitization of limestones,
— recrystallization of dolomites,
— replacem ent of dolomites by ZnS,
— infilling by ZnS of the open spaces formed during the ore m eta
somatism 10*
— replacem ent of dolomites and sphalerite by FeS2
6 — the m etasom atic processes are show n by the inherited stru ctu res observed in limestones and ore-bearing dolomite, and in the spha
lerite ores
7 — the rhy tm ic ore structures m ight have been caused by the diffu- sional ch aracter of flow of the m ineralizing solutions
8 — the deposits located in collapse breccias were form ed a fte r the em placem ent of the m etasom atic ores.
translated by H. Czubakowska
REFERENCES — W YKAZ LITERATURY
B o g a c z K., D ż u ł y ń s k i S., H a r a ń c z y k C . , S o b c z y ń s k i P. (1972). Contact relationship o f the ore-bearing dolom ite in the Triassic of the Cracow—S ilesian region. Rocz. Pol. Tow. Geol. (Ann. Soc. Geol. Pol.), 42, 4: 347— 372, Kraków.
B o g a c z K., D ż u ł y ń s k i S., H a r a ń c z y k C., S o b c z y ń s k i P. (1973), Spha
lerite ores reflectin g the pattern of prim ary stratification in the Triassic of the Cracow— S ilesian region. Rocz. Pol. Tow. Geol. (Ann. Soc. Geol. Pol.), 43, 3: 286—300, W arszawa—Kraków.
B o g a c z K., D ż u ł y ń s k i S., H a r a ń c z y k C., S o b c z y ń s k i P. (1975), Origin of the ore-bearing dolom ite in the T riassic of the Cracow—S ilesian Pb— Zn ore district. Rocz. Pol. Tow. Geol. (Ann. Soc. Geol. Pol.), 45, 2: 139—155, Kraków.
C h u - T u a n - N h a , K u b i s z J. (1973), C echy typom orficzne siarczków Zn, Pb i Fe ze złóż śląsko-krakow skich (Typomorphic features of Zn, Pb and Fe sulfides from th e C racow—Silesian ore district). Prace Mineralog. (Mineral.
Transaction), 32: 1—57, W arszawa.
D ż u ł y ń s k i S., S a s s - G u s t k i e w i c z M. (1977), C om m ents on the genesis of th e E astern-A lpine Zn—Pb deposits. Mineralium Deposita, 12: 219—233, Berlin.
M o c h n a c k a K., S a s s - G u s t k i e w i c z M. (1978), M etasom atic processes along the contact of th e ore-bearing dolom ite w ith lim estones (Olkusz Mine,, Cracow—S ilesia n Zn—Pb ore district). Rocz. Pol. Tow. Geol. (Ann. Soc. Geol.
Pol.),48, 2: 183— 191, Kraków.
P o s p e l o v G. L. (1973), Paradoxes, geologo-physical nature and m echanism of m etasom atosis, 353 pp., Novosibirsk.
P r z e n i o s ł o S. (1974), Cynk i ołów w utw orach w ęglan ow ych triasu rejonu za
w ierciańskiego (Zinc and lead in the Triassic carbonate rocks in the vicin ity of Zawiercie). Biul. I.G. 278: 115—200, W arszawa.
S a s s - G u s t k i e w i c z M. (1974), Callapse breccias in the ore-bearing dolom ite of the Olkusz Mine (Cracow—S ilesian ore district). Rocz. Pol. Tow. Geol.
(Ann. Soc. Geol. Pol.),44, 2— 3: 217—226, Kraków.
S a s s - G u s t k i e w i c z M. (1975), Zinc and lead m ineralization in collapse brec
cias of the Olkusz Mine (Cracow—S ilesia n region, Poland). Rocz. Pol. Tow.
Geol. (Ann. Soc. Geol. Pol.),45, 3—^4: 303—326, Kraków.
S m o l a r s k a I. (1968), C harakterystyka złoża rud cynku i ołow iu kopalni Trze
bionka (Characteristic of the zinc and lead deposit of the Trzebionka Mine).
Prace Geolog. (Geological Transact.),47: 1—47, W arszawa.
S o b c z y ń s k i P., S z u w a r z y ń s k i M. (1974), W ykształcenie dolom itów i hory
zonty rudne w dolnym w apieniu m uszlow ym w kopalni Trzebionka (Dolomites and ore horizons in the Lower M uschelkalk of the Trzebionka Mine). Rocz.
Pol. Tow. Geol. (Ann. Soc. Geol. Pol.), 44, 4: 546— 556, W arszawa—Kraków.
— 149 —
STRESZCZENIE
Złoże kopalni Pom orzany znajduje się w. północnej części obszaru olkuskiego. Je st ono jedynym w rejonie śląsko-krakowskim miejscem w ystępowania na większą skalę ru d m etasom atycznych obok ru d brek - cjowych.
Podobnie jak pozostałe złoża tego rejonu, złoże Pom orzany jest u sy
tuow ane w utw orach w apienia muszlowego, a spągowe części badanych ciał rudnych znajd u ją się w obrębie serii zlepieńcowej w arstw gogoliń- skich. Ciała rudne wykształcone są w postaci gniazd oraz w form ach zbliżonych do pokładów. Skałam i otaczającym i złoże są w apienie i dolo
m ity kruszconośne w ykazujące duże zróżnicowanie petrograficzne. W y
różniono sześć odm ian w apieni oraz siedem odmian dolomitów (tabela 2).
Dolomity kruszconośne jako utw ory epigenetyczne pow stałe z prze
kształcenia wapieni w ykazują w wielu przypadkach s tru k tu ry odziedzi
czone po nich. N iekiedy są one zatarte w skutek działania procesów re
krystalizacji i rozpuszczania towarzyszących metasomatozie.
W złożu m etasom atycznym jedynym m inerałem użytecznym jest sfa- leryt, rzadko w ystępuje galena, niekiedy spotyka się duże nagrom adze
nia m arkasytu. Ciała rudne m ają zwykle form ę płaską zbliżoną do po
kładu, o miąższości 0.5—2.5 m. Czasami jednakże dochodzi do gw ałtow
nego w zrostu miąższości przekraczającej wielokrotnie przeciętną. W skali ociosu pokłady m ają kształt nieregularny, a ich spąg pokryw a się ze spągiem ciał dolomitowych dziedzicząc po nim nieregularny m etasom a- tyczny kontakt (fig. 1, 2, 3). Podobnie jak dolomit dziedziczył stru k tu ry po wapieniu, ta k i ru d y m etasom atyczne dziedziczą stru k tu ry po dolo
m itach. P rzykładem są s tru k tu ry w arstw ow ane i plam iste przedstaw ione na planszach II i III.
Przeprowadzone badania m akro- i mikroskopowe ru d m etasom atycz
nych i skał otaczających pozwoliły na wydzielenie kilku form w ystępo
w ania sfalerytu, odpowiadających kilku generacjom (fig. 4). Je st to sfa- le ry t rozproszony I, im pregnacyjny II, kolomorficzny Ilia i krystalicz
ny Illb . Tworzenie się tych odmian związane jest z kolejnym i m etaso- m atycznym i przekształceniam i skał otaczających. Rozwój procesów m e
tasom atycznych przedstaw iono na fig. 5. Uogólniając, w rozwoju złoża metasom atycznego można stwierdzić działalność następujących proce
sów: 1 — dolomityzacji wapieni, 2 — rekrystalizacji dolomitu, 3 — za
stępow ania metasom atycznego siarczkami cynku, 4 — w ypełniania wol
nych przestrzeni pow stałych p rzy m etasom atozie siarczkami cynku i że
laza oraz 5 — zastępowania metasom atycznego dolomitów i m inerałów kruszcowych przez siarczek żelaza.
Obserwowane frag m en ty ru d m etasom atycznych w zm ineralizow a- nych brekcjach zawałowych świadczą, że procesy krasowe w złożu roz
w ijały się po utw orzeniu się złoża rud metasomatycznych.
Praca n in iejsza została w ykonana w ram ach realizacji problem u resortow ego
„Rozpoznanie w aru nk ów geologiczno-złożow ych dla potrzeb eksploatacji i racjo
nalnej gospodarki złożam i Zn—P b” koordynow anego przez ZBIP „Cuprum”.
EX PLA NA TIO N OF PLATES — OBJAŚNIENIA PLA N SZ
P late — Plansza I
Fig. 1. Banded ores: s — colloform sphalerite (light grey and black); tn — m arca
site (dark grey); k — calcite (white). In the low er part of the sam ple, spha
lerite bands contain relics of dolom ite (d). M arcasite replaced colloform sphalerite or filled the em pty voids form ed during the m etasom atism . The youngest calcite and galena (g) filled up all open spaces.
Fig. 1. Ruda o strukturze w arstw ow anej złożona z pasm kolom orficznego sfalerytu (s — jasnoszare i czarne pasma), m arkasytu (m — ciem noszary) oraz k a l- cytu (k — biały). W dolnej części okazu pasm a sfalerytu zaw ierają relik ty dolom itu (d). M arkasyt zastępuje sfaleryt kolom orficzny oraz w yp ełn ia w o l
ne przestrzenie pow stałe w sk u tek m etasom atozy sfalerytow ej. N ajm łodszy kalcyt i galena (g) w ypełn iają praw ie całkow icie pozostałe pustki.
Fig. 2. Ore fragm en t from the top of a m etasom atic body: ds — sphalerite im pre
gnations in dolom ite. The sphalerite grains follow the lam ination of dolo
mite. T he am ount of sphalerite grains increases tow ards the sh eet-lik e vu gs (ev) passing into the lig h t- and dark-brow n incrustations of sphalerite (s).
g — galena, m — irregular m etasom atic concentrations o f m arcasite.
Fig. 2. Fragm ent rudy ze stropu pokładu rud w arstw ow an ych . Znaczną część oka
zu (szare części — ds) stanow i dolom it im pregnow any sfalerytem . Im pre
gnacje sfalerytow e układają się w pasm a rów noległe do Iaminacji. Ilość sfalerytu w zrasta stopniowo w kierunku podłużnych p ustek (ev) przecho
dząc w inkrustacje jasnego i ciem nobrązowego sfalerytu (s). g — galena, m — nieregularne m etasom atyczne skupienia markasytu.
Plate — Plansza II
E xam ples of inherited structures. S p ongy-lik e ore-bearing dolom ite w ith rhythm i
cally repeated layers of clay m inerals — dark lam inae (Fig. I). In Fig. 2 — sam ple of spongy-like sphalerite ore. The vugs incrusted by colloform sphalerite (s) cor
respond ex a ctly to lam inae of clay m inerals observed in Fig. 1.
Przykład dziedziczenia struktur w procesie m etasom atozy. Figura 1 przedstaw ia gąbczasty dolom it, w którym powtarzają się rytm icznie lam iny substancji ilastej (ciem ne smugi). Na Figurze 2 przedstaw iony jest okaz rudy sfalerytow ej. Jej struktura jest rów nież gąbczasta. R ytm pustek inkrustow anych sfalerytem (s) od
powiada ściśle rytm ow i lam in substancji ilastej na Figurze 1.
P late — Plansza III
S e t of spotted structures observed in lim eston e (Fig. 1), ore-bearing dolom ite (Fig. 2), sphalerite ore (Fig. 3), and m arcasite ore (Fig. 4). T hey illustrate the in heritance of structures during the dolom ization and ore m etasom atism .
— 151 —
Z estaw struktur plam istych obserw ow anych w w ap ien iu (Fig. 1), w dolom icie kruszconośnym (Fig. 2), w rudzie sfalerytow ej (Fig. 3) oraz w rudzie m arkasytow ej (Fig. 4), Stanow ią one ilustrację dziedziczenia struktur w procesie dolom ityzacji oraz m etasom atozy kruszcow ej.
P late — Plansza IV
Fig. 1. M etasom atic sphalerite ore. T he sphalerite (s) form s im pregnations in ore- -b earing dolom ite. Transm itted light, one nicol.
Fig. 1. Ruda m etasom atyczna. S faleryt (s) tw orzy im pregnacje w dolom icie. Bez analizatora, św iatło przechodzące.
Fig. 2. Ore-bearing dolom ite. Coarse crystalline, idiotopic dolomite. Iron hydroxides (black) aceentuate outlines of dolom ite rhombohedra. Transm itted light, one nicol.
Fig. 2. D olom it kruszconośny. D olom it grubokrystaliczny, idiotopiczny. Skupienia w odorotlenków żelaza (czarne) podkreślają zarysy rom bów dolom itu. Bez analizatora, św iatło przechodzące.
Fig. 3. Ore-bearing dolom ite. Coarse crystalline idiotopic dolomite. Iron hydroxides accentuate outlines of dolom ite rhomboedra. Moreover, the pseudom orphosis of sphalerite (s) after dolorhombs are visible. Transm itted light, one nicol.
Fig. 3. D olom it kruszconośny. D olom it grubokrystaliczny, idiotopiczny. Z arysy rom bów podkreślone są skupieniam i w odorotlenków żelaza (czarne). W idoczne są ponadto pseudom orfozy sfalerytu (s) po rom bach dolom itu. Bez analiza
tora, św iatło przechodzące.
Fig. 14. M etasom atic sphalerite ore: s — sphalerite, d — dolom ite rhomboedra Transm itted light, one nicol.
Fig. 4. Ruda m etasom atyczna: s — sfaleryt im pregnacyjny, d — rom by dolom itu B ez analizatora, św ia tło przechodzące.
Ann. Soc. Geof. Poloniae v. 5 1 / 1 - 2
К . M ochnacka, М . Sass -Gustkie wic z Pi //
Ann. Soc. Geo/. Poloniae v. 5 1 1 1 -2
Ann. Soc. Geoi. Poloniae v, 51
/
1-2CM
К . M ochnacka, М . Sass -G ustkiew icz PI. IV
o«1 m m
Ann. Soc. G eoi Poloniae v. 51 j 1-2
