Dickite and kaolinite in the Pb-Zn-Agsulphide deposits of northern Kosovo

(Trepca and Crnac)

S. S . PALINKAS 1 , * , S . B . SO ST AR IC 1 , V . BE RMANE C 1 , L . PAL INKAS 1 ,

W. PROCHASKA 2 , K . FURIC 3AND J . SMAJLOVIC 4

1 Faculty of Science, Horvatovac bb, HR-10000 Zagreb, Croatia, 2 Montanuniversitat Leoben, Peter-Tunner-Straße 5,

8700 Leoben, Austria, 3 Ruder Boskovic Institute, Bijenicka 54, P.O.B. 180, HR-10000 Zagreb, Croatia, and 4

Geotechnical Faculty Varazdin, Hallerova aleja 7, HR-42000 Varazdin, Croatia

(Received 25 March 2008; revised 2 July 2008; Editor: John Adams)

ABSTRACT: Alteration minerals dickite and kaolinite were detected in two hydrothermal Pb-Zn-

Ag sulphide deposits in the northern Kosovo region. Dickite is associated with skarn mineralization

in the Trepca (Stari Trg) deposit and kaolinite occurs in vein sulphide parageneses in the Crnac

deposit. The mineralogical characteristics of dickite and kaolinite were determined by X-ray powder

diffraction, Raman spectroscopy and scanning electron microscopy with EDS detector. Fluid-

inclusion microthermometry and ion chromatography of leachates provided information on the P-T-X

conditions of the genesis of dickite at Trepca. It was formed at temperatures between 290 and 330ºC

and pressures between 12 and 60 MPa from a fluid with salinity in the range 6�8.5 wt.% NaCl eq.

and pH <5.5. Kaolinite was deposited from a fluid with minimum temperatures between 210 and

250ºC, minimum pressure of 1.7 to 3.7 MPa, and salinity between 4.6 and 5.1 wt.% NaCl eq. Both

dickite and kaolinite are related to the acidic pre-mineralization phase in the deposits.

KEYWORDS: alteration, dickite, kaolinite, hydrothermal, Pb-Zn-Ag deposits, Trepca, Crnac, Kosovo, Dinarides.

The kaolin group is represented by the minerals

kaolinite, dickite and nacrite. Identification of the

three polytypes with the chemical formula

Al4Si4O10(OH)8 can be achieved by combination

of X-ray diffraction (XRD), Raman spectroscopy

and scanning electron microscopy (SEM). Kaolinite

occurs in hydrothermal ore veins, in hot spring

deposits and as authigenic vermicular crystals in

sediments. It is a common weathering product and

is a major component of soils, residual clays,

bauxites and certain sedimentary deposits (Bailey &

Tyler, 1960; Murray, 1988). Dickite is generally

related to conditions of higher temperature and

pressure, mainly occurring in hydrothermal envir-

onments (e.g. Balan et al., 2005). Nacrite is the

rarest polytype of the kaolin minerals and is mostly

related to hydrothermal systems (e.g. Buatier et al.,

1996).

Kaolin minerals are recorded within two hydro-

thermal Pb-Zn-Ag sulphide deposits in northern

Kosovo, both of which are related to Late

Palaeogene, post-collisional volcanism (Cvetkovic

et al., 2004). Dickite occurs in the Trepca (Stari

Trg) deposit and kaolinite is found in the Crnac

deposit (Fig. 1).

This paper deals with the genesis of dickite and

kaolinite and presents their mineralogical character-

istics. The geochemical conditions for the formation

of dickite and kaolinite in Pb-Zn-Ag sulphide

deposits in Kosovo are estimated on the basis of

fluid-inclusion data obtained from cogenetic quartz

spatially associated with the kaolin minerals.* E-mail: sabina.strmic@inet.hrDOI: 10.1180/claymin.2009.044.1.67

ClayMinerals, (2009) 44, 67–79

# 2009 The Mineralogical Society

G E O L O G I C A L S E T T I N G

Trepca hydrothermal-replacement ore deposit

The Trepca hydrothermal-replacement ore

deposit is situated 40 km NW of Pristina, Kosovo

(Fig. 1) and the mine is located within the

Kopaonik block of the Western Vardar zone in

the eastern part of the Dinarides (Dimitrijevic,

1997).

The mineralization is represented by galena,

sphalerite, pyrite, arsenopyrite and pyrrhotite, and is

hosted by recrystallized limestones with inherited

palaeokarst features under a screen of Triassic schists.

The palaeokarst phenomenon played an important

role in the ore-deposit genesis, as conduits for ore-

forming fluids during loading of the ore. The

mineralization is structurally controlled. The steeply

dipping pipe-shaped structure, with a volcanic semi-

circular sanidine-latite plug of Oligocene age

surrounded by volcanic breccia at the contact

between schists and carbonates, controls the geometry

of the ore body (Fig. 2a). The major gangue minerals

are carbonates and quartz. The formation of skarn

minerals (ilvaite, hedenbergite and garnet) preceded

sulphide mineralization (Schumacher, 1954).

The breccia is composed of subangular fragments

of the country rocks, rounded clasts of sanidine-

latites and blocks composed of pyrrhotite, magnetite

Stari Trg(Trepča) deposit

Crnac deposit

Quaternary

Cretaceous

Jurassic ophiolite and ophiolite mélange

Triassic metamorphic complex

Pal eozoica

Tertiary volcanics

Priština

Stari Trg

K O S O V O

SERBIA

AL

BA

NIA

FYROMACEDONIA

Crnac

5 km

FIG. 1. Simplified geological map of the Kosovo area with locations of investigated dickite and kaolinite

occurrences.

68 S. S. Palinkas et al.

and pyrite. The usual size of the clasts ranges from

tens of centimetres to several metres. In the deeper

levels, the breccia cuts limestones and occasionally

assumes the characteristics of a fluidized breccia

with milled matrix (Forgan, 1950; Schumacher,

1954; Bogdanovic et al., 1978). This type of breccia

consists mainly of ‘rock flour’. The dominant

minerals are carbonates, various silicates (mostly

sericitic feldspar and feldspar) and quartz.

Carbonates are occasionally replaced by pyrite.

There are two modes of dickite occurrence within

the Trepca deposit, both of which are associated

with the breccia. (1) Dickite in the form of

monomineral aggregates is a vug-filling cluster

within Fe-carbonate fragments of breccia (Fig. 3a).

Carbonate is represented by siderite enriched in Ca

and Mn. It is occasionally impregnated by pyrite

and replaced by microcrystalline quartz. Quartz also

occupies cavities in the form of euhedral crystals.

(2) Dickite also occurs as an alteration product of

silicate minerals, mostly sericitic feldspar and

K-feldspar in a milled matrix of fluidized breccia.

Crnac Pb-Zn-Ag hydrothermal-replacement

deposit

The Crnac vein-type hydrothermal deposit is

situated in the Western Vardar zone, at the

FIG. 2. Cross-section though: (a) the Trepca (Stari Trg) deposit (after Forgan, 1950); and (b) the Crnac deposit

(after Miletic, 1995).

Dickite and kaolinite from northern Kosovo 69

northernmost border of the Kosovo region (Fig. 1).

It consists of two types of mineralization � a vein

type in Jurassic amphibolite and gabbro and a

disseminated type in metasomatic listwaenites

(Fig. 2b). The Jurassic amphibolite hosts are over-

lain by serpentinite and serpentinized peridotites

and therefore the structure resembles an amphibo-

lite within an obducted ophiolitic block. The entire

geological section is cross-cut and was intruded by

sanidine-latite dykes in the Oligocene. The sani-

dine-latite dykes are accompanied or enveloped by

vein-type mineralization which consists of a series

of steeply dipping massive ore veins, 1�5 m thick.

Ore petrography suggests three vein-formation

stages: (1) a pre-mineralization stage, with pyrite-

quartz-kaolinite; (2) the major mineralization stage

with galena-sphalerite-chalcopyrite; and (3) a post-

mineralization stage, with prevailing carbonates

sideri te-ankeri te-calci te-dolomite-cerussi te

(Pavlovic and Todorovic, 1961; Urosevic et al.,

1966).

Listwaenite is a silica-carbonate rock produced

by the hydrothermal alteration of serpentinite. The

listwaenite type of mineralization occurs in the

uppermost level of the deposit, at the contact

between amphibolites and overlying serpentinite.

Silicification followed by lesser pyritization is a

pre-mineralization stage, the next stage being base-

metal formation terminating with carbonatization,

sericitization and illitization. Some of the listwae-

nite samples grade into hydrothermal breccias, with

an increased fraction of rounded particles from the

pre-mineralization phase, cemented later during the

major mineralization phase.

Kaolinite occurs in the three different para-

geneses within the Crnac Pb-Zn-Ag deposit:

(1) kaolinite associated within vein-type mineraliza-

tion, following a pre-mineralization stage with large

masses of euhedral quartz and pyrite grown in open

space (Fig. 3b); (2) kaolinite associated with a

listwaenite type of mineralization occurs as rounded

clasts up to 3 cm in size; and (3) kaolinite

associated with the sanidine-latite dykes as an

alteration product of feldspars.

Kaolinite type 1 occurs as milky-white irregular

masses, a few mm to cm in size. It is more

abundant at the lowermost level of the deposit,

decreasing upwards in quantity. In some places

kaolinite is associated with carbonates, assumed to

be introduced during the post-mineralization phase.

The purity of kaolinite also decreases upwards,

where it is often found as a mixture of kaolinite-

ankerite-illite-chlorite-montmorillonite phases.

S A M P L E S A N D M E T H O D S

Dickite in the form of monomineral aggregates was

hand-picked from vug-fillings in the fragments of

Fe-carbonates within the breccia (Fig. 3a). The size

of the aggregates, up to 5 mm, allows separation of

dickite without contamination by the host rock.

Milky-white kaolinite type 1 from vein-type

mineralization was hand-picked from level VI in

the Crnac deposit (Fig. 3b). It appears as irregular

masses of vug-fillings, up to 1 cm in size in the

quartz-pyrite pre-mineralization assemblage.

X-ray powder diffraction (XRD) analyses were

carried out on oriented samples using a Philips

FIG. 3. Macroscopic view of: (a) dickite clusters within breccia fragments from the Trepca deposit; (b) vein-type

mineralization from the Crnac deposit with milky white irregular masses of kaolinite. Kaolinite is associated with

the quartz-pyrite-arsenopyrite pre-mineralization assemblage.

70 S. S. Palinkas et al.

diffractometer PW 3040/60 X’Pert PRO (45 kV,

40 mA) with Cu-Ka1 monochromatized radiation

(l = 1.54056 A) and y�y geometry. The samples

were scanned between 4 and 63º2y with 0.02º steps

per 0.5 min and between 48 and 78º2y with 0.02º

steps per min. The goniometer was calibrated

against a quartz standard.

The textural features of the sample were

examined using a Tescan scanning electron micro-

scope (SEM) equipped with an INCA 250 analysing

system. The analyses were carried out using the

following operating conditions: 3�40 mm beam,

accelerating voltage 20 kV, probe current 10 nA,

and counting time 200 s.

Raman spectroscopy was carried out using a Jobin

Yvon T64000 system working in micro-Raman,

triple-monochromatic mode. An argon ion laser

(Coherent, Innova 400, Santa Clara, California,

USA) operating at 514.5 nm with a laser power of

20 mW excitation on the samples was used.

Fluid-inclusion studies were carried out within

doubly-polished ~0.5 mm thick wafers of quartz

associated with dickite and kaolinite. Measurements

were carried out using a Linkam THMS 600 stage

mounted on an Olympus BX 51 microscope with

106 and 506 Olympus long-working distance

objective lenses in visible light. Two synthetic

fluid-inclusion standards (SYN FLINC; pure H2O,

10 20 30 40 50 60 70 80

(131)

(131)

Inte

nsity

-

(001)

(020)

(060)(135)

-(154)

-

10 20 30 40 50 60 70

Inte

nsity

a

b

(02

2)

(11

2)

(02

1)

(11

0)

(13

0)(1

31

)(1

32

) (13

2)

(13

10

)

°2θ

°2θFIG. 4. XRD patterns of: (a) dickite from the Trepca deposit; (b) kaolinite from the Crnac deposit.

Dickite and kaolinite from northern Kosovo 71

mixed H2O-CO2) were used to calibrate the

equipment. The precision of the system was U2.0ºC

for the homogenization temperature, and U0.2ºC in

the temperature range between �60 and +10ºC.

Solute chemistry analyses were conducted using

a crush-leach procedure (Nesbitt & Prochaska,

1998). For the determination of solute chemistry,

quartz and pyrite with grain sizes of 0.5�1 mm

were separated. Surface impurities were removed

by treatment with dilute HNO3. The samples were

rewashed in double-distilled water twice per day for

5 days. 1 g of cleaned crystals was ground in 5 ml

of double-distilled water using an agate mortar and

pestle. The resulting slurry was filtered to separate

the leachate from the sample residue. Anions (Cl�,

SO42� and F�) and cations (Li+, Na+, K+, Ca2+,

Mg2+) of the leachates were analysed by ion

chromatography using a Dionex DX�500 system

with a micromembrane suppressor.

R E S U L T S

Dickite

The XRD patterns are shown in Fig. 4a and

diffraction lines with their relative intensities are

listed in Table 1. All diagnostic diffraction lines for

dickite are present (Brindley & Brown, 1980).

Special attention was given to patterns with

reflections between 20�24, 34�40 and 70�74º2y.

Dickite differs from the other kaolin minerals in

terms of the presence of a triplet in the 20�24º2yrange and an distinct peak at 3.79 A (Chen et al.,

2001). A triplet in the range 35�36º2y and a single

peak at 38.8º2y also suggest dickite (Chen et al.,

2001). A prominent peak at 71.5º2y distinguishes

dickite from kaolinite (Zotov et al., 1998). No

crystalline impurity was observed. The results of

least-squares refinement of the dickite structure using

the present XRD data are a = 5.147(1), b = 8.932(1),

c = 14.421(3) A, b = 96.86(2)º and V = 658.2(1) A3.

Scanning electron microscopy showed that the

dickite aggregates consist of 1�2 mm thick

pseudohexagonal crystals ranging from 5 to 20 mm

in diameter (Fig. 5a). The major chemical elements

determined by EDX detector are Al, Si, and O.

The Raman spectra of dickite are characterized by

six bands in the n(OH) stretching region listed in

Table 2 and shown in Fig. 6a. The relative intensities

of the n(OH) bands depend strongly on the

orientation of the crystals and scattering geometry

(Johnson et al., 1998). Bands at 3623, 3686 and 3697

TABLE 1. d spacing and relative intensity of diagnostic XRD peaks for dickite from the Trepca deposit and

kaolinite from the Crnac deposit.

——————— Dickite ——————— —————— Kaolinite ——————d spacing

(A)Relative intensity

(%)hkl d spacing

(A)Relative intensity

(%)hkl

7.21 69 002 7.13 100 0014.47 20 020 4.35 6 1104.37 22 110 4.17 5 1114.29 18 021 3.84 2 0214.14 38 112 3.57 68 0023.97 9 111 3.15 0.3 1123.79 28 022 2.75 0.5 0223.58 100 004 2.38 6 0032.56 21 130 2.33 7 1132.51 31 131 2.29 5 1312.46 3 132 2.19 0.6 2012.39 15 006 2.00 1 2032.34 71 132 1.98 2 1322.20 7 134 1.84 0.6 2021.98 26 206 1.62 2 1511.86 7 136 1.54 0.8 3131.46 8 330 1.34 1 1351.39 3 336 1.31 1 1351.32 17 1310 1.30 1 154

72 S. S. Palinkas et al.

cm�1 are indicative of dickite polycrystals (Wiewiora

et al., 1979). A sharp band at 3623 cm�1 is

indicative of dickite single crystals (Johnson et al.,

1998). The shoulder at 3686 cm�1 points to the

presence of diffusely adsorbed water. The bands

within the 50�1800 cm�1 region (Table 2, Fig. 6a)

are in agreement with published data for dickite

(Wiewora et al., 1979; Johnson et al., 1998).

Primary fluid inclusions from quartz (Fig. 7a)

associated with dickite are two-phase (L+V) at

room temperature and homogenize to a liquid phase

between 285 and 320ºC. Their salinities range

between 6.0 and 8.5 wt.% NaCl eq. Secondary fluid

inclusions were not observed.

The bulk leachate data (Table 3) of fluid

inclusions in quartz associated with dickite

suggest Cl� as major anion and Ca2+ and Na+ as

dominant cations. The total cation molar concentra-

tion is significantly less than the concentration of

Cl�. Such phenomena can be expected due to the

inability of the method to analyse all dissolved

species, notably Fe2+, Zn2+ and Pb2+. Fluid-

inclusion studies have shown that the mineralizing

fluid had a mean salinity of ~7.3 wt.% NaCl eq.

Assuming that chloride is the only anion present,

recalculated leachate data reveal an Na:Ca molar

ratio of 0.4�2.3, an Na:Mg ratio of 2.0�4.7 and a

uniform Na:K ratio of 3.3.

The fluid-inclusion density, in the range

0.7595�0.8482 g/cm3, was determined by a

combination of the microthermometric and bulk-

leachate data.

Isochores were calculated using the computer

program ISOC (Fig. 8; Bakker, 2003) from the

equation of state by Zhang & Frantz (1987) and a

correction for the volumetric properties of quartz.

Homogenization pressure (PH) was estimated to be

in the range 6.5�10.8 MPa.

Alkali geothermometers applied to the bulk

leachate data reveal a formation temperature in

the range from 290 (K-Na-Ca; Fournier &

Truesdell, 1973) to 330ºC (Na-K; Can, 2002). A

formation pressure between 12 and 60 MPa was

estimated by a combination of fluid-inclusion and

geothermometric data (Fig. 8).

FIG. 5. SEM images of: (a) classic book-like dickite aggregates composed of 5�15 mm-wide crystals;

(b) pseudohexagonal kaolinite plates, 3�5 mm wide, slightly elongated in shape and associated with 5�15 mm-

thick aggregates.

TABLE 2. List of Raman spectra band positions for

dickite from the Stari Trg deposit and kaolinite from

the Crnac deposit.

— Wavenumber (cm�1) —Dickite Kaolinite

131 130245 244270 273336 338420 433433 463462 752748 791791 916916 36223623 36553655 36693685 3692

Dickite and kaolinite from northern Kosovo 73

b20000

15000

10000

5000

00 500 1000 1500 2000

Wavenumber (cm )-1

Ra

ma

nin

tesity

20000

15000

10000

5000

00 500 1000 1500 2000

Wavenumber (cm )-1

Ra

ma

nin

tesity

a

4000

4000

3500

3500

FIG. 6. Raman spectra for low-frequency and the expanded hydroxyl-stretching region of (a) dickite from the

Trepca deposit; (b) kaolinite from the Crnac deposit.

FIG. 7. Photomicrographs of a representative primary, two-phase, fluid inclusion within quartz related to:

(a) dickite from the Trepca deposit; (b) kaolinite from the Crnac deposit.

74 S. S. Palinkas et al.

Kaolinite

The XRD pattern of kaolinite is plotted in

Fig. 4b. Sharp peaks indicate a well crystallized

sample. The XRD pattern displays two evident

groups of triplets: the first in the range

34.8�36.0º2y (2.58�2.50 A) and the second at

37.8�39.4º2y (2.38�2.29 A) (Chen et al., 2001).

According to Zotov et al. (1998), two additional

diagnostic peaks are to be found at 70.3º2y and

72.4º2y. Furthermore, reflections from (131) and

(131) indicate the triclinic symmetry of kaolinite

(Brindley & Porter, 1978). The cell parameters

determined for kaolinite are a = 5.13(3), b =

8.94(6), c = 7.52(5) A, and V = 335(3) A3, while a= 93.2(7)º, b = 103.5(7)º and g = 90.1(7)º.

The SEM images of kaolinite samples show a

number of large pseudohexagonal plates, slightly

elongated in shape (Fig. 5b). They frequently

appear as 5�15 mm thick clusters, with plate

diameters varying from 3 to 5 mm and occasionally

forming rose-shaped aggregates. Chemical analyses

do not show any impurities, while the Al peak is

almost equal in height to the Si peak.

The unit cell of kaolinite is C-centred and,

according to Bish (1993), corresponds to the C1

space group. It contains four OH groups and

consequently the Raman spectra of well crystallized

samples display four low-frequency bands. The

Raman spectra of kaolinite presented in Fig. 6b and

listed in Table 2 show a distinct low-frequency

TABLE 3. Bulk-leachate analyses (in ppb) of quartz from the Stari Trg, and pyrite from the Crnac deposits.

Sample Mineralogy Locality Li Na K Mg Ca Cl

T1 Quartz Stari Trg 6.4 660 342 353 2907 1390T1-qtz2 Quartz Stari Trg 21.5 4055 2097 914 3073 17078C 17/1/VI Pyrite Crnac 7.5 1052 743 299 688 2662

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400

�=

0.9

070

gcm

-3

�=

0.8

800

gcm

-3

5wt.%

NaCl equ

.iv

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400

Temperature °C( )

Pre

ss

ure

Ma

(P

)

�=

0.8

482

gcm

-3

�=

0.7

595

gcm

-3

L+V 7.5wt.%

NaCl equ

.iv

290

330°C

12 MPa

60 MPa

35 MPa

310

FIG. 8. P�T diagram showing isochores constructed on the basis of microthermometric data for fluid inclusions

within quartz associated with dickite from the Trepca deposit (solid lines) and with kaolinite from the Crnac

deposit (dashed line). The trapping temperatures are calculated from Na/K, and K/Mg/Ca geothermometric

equations applied to bulk-leachate data obtained on quartz associated with dickite from the Trepca deposit.

Dickite and kaolinite from northern Kosovo 75

band at 3622 cm�1 related to the stretching of the

inner OH group. The broad band observed at

3692 cm�1 is related to the in-phase stretching

mode of inner-surface OH groups. According to the

experimental studies of Balan et al. (2001, 2005),

within well ordered kaolinite samples this band is

shifted to a slightly lower frequency. Two weaker

bands at 3655 and 3669 cm�1 are attributed to the

two out-of-phase stretching modes of the inner-

surface OH groups. The bands within the low-

frequency region (Table 2, Fig. 6b) are in agree-

ment with published data for kaolinite (Wiewiora et

al., 1979; Johnson et al., 1998).

Fluid-inclusion microthermometry was carried

out on quartz wafers from the quartz-kaolinite-

pyrite assemblage at level VI. Several generations

of inclusions were identified. Primary two-phase

inclusions are situated within quartz growth zones.

They are rounded or spherical in shape, varying in

size from 8 to 10 mm (Fig. 7b). The degree of

filling is uniform (F = 0.95). Salinities vary

between 4.6 and 5.1 wt.% NaCl eq., and they all

homogenized to the liquid state at temperatures

ranging from 210 to 250ºC. The primary fluid-

inclusion assemblage is overprinted by pseudose-

condary inclusions, forming clusters that nearly

reach the grain boundaries. These fluids contain

bivalent cations. The formation of clathrates

indicates that, beside H2O, the inclusions contain

CO2. They are interpreted as the remains of late-

stage fluids evolved via water-rock reactions

(homogenization temperatures vary from 130 to

180ºC, and salinities from 0.6 to 6.9 wt.% NaCl

equiv.).

Due to a deficiency of quartz, bulk-leachate data

were obtained on pyrite associated with kaolinite

(Table 3). The alkali geothermometers applied

suggest an unreliable high temperature in the

range from 360ºC (K-Na-Ca; Fournier and

Truesdell, 1973) to 380ºC (Na-K; Can, 2002). The

possible source of errors lies in fact that bulk-

leachate data represent mixtures of fluid inclusions

of several generations, and some of them could

have large K contents due to water-rock

interactions.

The isochores were calculated using the computer

program ISOC (Fig. 8; Bakker, 2003) from the

equation of state by Zhang & Frantz (1987) and a

correction applied for the volumetric properties of

quartz.

The homogenization pressure was estimated to be

in the range 1.7�3.7 MPa.

D I S C U S S I O N

The most common parent minerals from which

kaolin minerals develop are feldspars and musco-

vite. The alteration of K-feldspar into kaolin

minerals occurs according to the equation

2 KAlSi3O8 + 2 H+>

Al2Si2O5(OH)4 + 4 SiO2 + 2 K+ (1)

To form kaolin minerals from muscovite, it is

necessary to remove K and to add protons which

are transformed into OH groups, coordinating Al in

accordance with the equation:

2 KAl2[Si3AlO10](OH)2 +

H+ + 3 H2O > 3 Al2Si2O5(OH)4 + 2 K+ (2)

The formation temperature and pressure esti-

mated from fluid-inclusion and ion-chromatography

data are incorporated into the thermodynamics of

formation reactions for dickite from K-feldspar and

muscovite.

The activity diagrams and reactions mentioned

above emphasize the strong influence of fluid

composition on the alteration mineralogy, whilst

temperature has a marked influence on the actual

position of the phase boundaries. The ratios of

constituents (aK+/aH+) are more important than

absolute concentrations (e.g. Corbett & Leach,

1998).

The K activity was determined using the

computer program BULK (Bakker, 2003) in

combination with the final ice-melting temperature

and the bulk-leachate data. Activity coefficients of

H2O and dissolved salts in fluid inclusions are

calculated according to the thermodynamic model

of Pitzer (1991).

The occurrence of dickite without K-feldspar

and/or muscovite at a temperature of 310ºC,

pressure of 35 MPa and K activi ty of

0.127 mol/dm3, requires a pH of <5.5 (Fig. 9).

Phase boundaries are constructed from equations 1

and 2 on the basis of thermodynamic data for

dickite (Fialips et al., 2003), K-feldspar, muscovite,

quartz, water, K+ and H+ (Helgeson et al., 1978,

1981; Helgeson & Kirkham, 1974). The dielectric

constant of water is taken from Helgeson &

Kirkham (1974).

Dickite occurs at a high-temperature, moderate-

pressure and low-pH environment. In the Trepca

deposit, dickite is intimately related to the early

stage of mineralization and is an indicator of an acid

environment and a high temperature of formation.

76 S. S. Palinkas et al.

Fluid-inclusion data obtained on quartz asso-

ciated with kaolinite are used for estimation of the

kaolinite formation temperature and pressure.

Homogenization temperatures (TH) and pressures

(PH) are recorded in the range 210�250ºC and

1.7�3.7 MPa, respectively. Due to the lack of an

adequate amount of quartz associated with the

kaolinite, the alkali geothermometer cannot be

applied. Comparison of fluid-inclusion data

obtained from dickite-quartz and kaolinite-quartz

assemblages suggests a lower homogenization

temperature and pressure for kaolinite than for

dickite. Also, kaolinite is precipitated from less

saline fluids. Calculation of pH values for the

formation of kaolinite failed due to the absence of

reliable bulk-leachate data.

C O N C L U S I O N S

A combination of methods enabled positive

identification and distinction between dickite and

kaolinite. The temperature, pressure and fluid pH

are the most important of many factors which

influence the clay mineralogy of hydrothermal

systems (e.g. Browne, 1978; Henly et al., 1984).

In the Trepca deposit, Kosovo, dickite has been

described for the first time. It consists of

micrometre-sized crystals as vug-filling clusters

within Fe-carbonate fragments of breccia and is

the only kaolin phase present. The formation of

dickite is related to the pre-ore phases in the deposit

and is precipitated from high-temperature

(290�330ºC), moderately saline (6.0 and 8.5 wt.%

NaCl equiv.), acid (pH <5.5) fluids under pressures

of 12�60 MPa.

The kaolinite investigated occurs in vein-type

mineralization of the Crnac deposit. It forms milky-

white irregular masses of vug-fillings and belongs

to the quartz-pyrite-kaolinite paragenesis.

According to fluid-inclusion data, kaolinite is

precipitated at moderate temperature (TH =

210�250ºC) and low pressure (PH = 1.7�3.7

MPa) from low-salinity fluid (4.6� 5.1 wt.%

NaCl eq.).

ACKNOWLEDGMENTS

This study was supported by the by the Croatian

Ministry of Sciences, Technology and Sports (Projects

No. 119-0982709-1175 and 119-0000000-1158). The

authors are grateful to the geological teams at the

Trepca and Crnac mines, in particular to Drs M. Diehl

and G. Maliqi for help and constructive discussions

during fieldwork. They are also grateful to Goran Durn

and an anonymous referee for critical reviews and

helpful suggestions which improved the content and

presentation of the manuscript.

REFERENCES

Bailey S.W. & Tyler S.A. (1960) Clay minerals

associated with the Lake Superior iron ores.

Economic Geology, 55, 150�175.

Bakker R.J. (2003) Package FLUIDS 1. Computer

programs for analysis of fluid inclusion data and

for modelling bulk fluid properties. Chemical

Geology, 194, 3�23.

-8

-6

-4

-2

0

2

4

0 2 4 6 8 10 12

pH

log

Ka

+Dickite

K-feldspar

Dickite

Muscovite

FIG. 9. Stability diagram of dickite�K-feldspar and dickite�muscovite at 310ºC and 35 MPa. The activity of K is

calculated from a combination of fluid-inclusion and bulk-leachate data.

Dickite and kaolinite from northern Kosovo 77

Balan E., Saitta A.M., Mauri F. & Calas G. (2001) First-

principles modeling of the infra-red spectrum of

kaolinite. American Mineralogist, 86, 1321�1330.

Balan E., Lazzeri M., Saitta A.M., Allard T., Fuchs Y. &

Mauri F. (2005) First-principles study of OH-

stretching modes in kaolinite, dickite, and nacrite.

American Mineralogist, 90, 50�60.

Bish D.L. (1993) Rietveld refinement of the kaolinite

structure at 1.5 K. Clays and Clay Minerals, 41,

738�744.

Bogdanovic P., Urosevic M., Urosevic D., Dimitrijevic

M., Markovic B., Pavic A., Menkovic L. & Folgic K.

(1978) General geological map of SFRJ 1:100 000,

schist Titova Mitrovica. Federal Geological Survey,

Belgrade.

Brindley G.W. & Brown G. (1980) Crystal Structures of

Clay Minerals and their X-ray Identification.

Monograph 5, Mineralogical Society, London.

Brindley G.W. & Porter A.R.D. (1978) Occurrence of

dickite in Jamaica. Ordered and disordered varieties.

American Mineralogist, 63, 554�562.

Browne P.R.L. (1978) Hydrothermal alteration in active

geothermal fields. Annual Review of Earth and

Planetary Sciences, 6, 229�250.

Buatier M.D., Potdevin J.-L., Lopez M. & Petit S.

(1996) Occurrence of nacrite in the Lodeve Permian

basin (France). European Journal of Mineralogy, 8,

847�852.

Can I. (2002) A new improved Na/K geothermometer by

artificial neural networks. Geothermics, 31,

751�760.

Chen P.Y., Wang M.K. & Yang D.S. (2001) Mineralogy

of dickite and nacrite from northern Taiwan. Clays

and Clay Minerals, 49, 586�595.

Corbett G.J. & Leach T.M. (1998) Controls on

hydrothermal alteration and mineralization. Pp.

69�82 in: Southwest Pacific Rim Gold-Copper

Systems: Structure, Alteration, and Mineralization

(G.J. Corbett and T.M. Leach, editors). Special

Publication, 6, Society of Economic Geologists,

Tulsa, Oklahoma, USA.

Cvetkovic V., Prelevic D., Downes H., Jovanovic M.,

Vaselli O. & Pecskay, Z. (2004) Origin and

geodynamic significance of Tertiary postcollisional

basaltic magmatism in Serbia (central Balkan

Peninsula). Lithos, 73, 161�186.

Dimitrijevic M.D. (1997) Geology of Yugoslavia.

Geological Institute GEMINI Special Publication,

Belgrade.

Fialips C.-I., Majzlan J., Beaufort D. & Navrotsky A.

(2003) New thermochemical evidence on the stabi-

lity of dickite vs. kaolinite. American Mineralogist,

88, 837�845.

Forgan C.B. (1950) Ore deposits at the Stari Trg lead-

zinc mine. Pp. 290�307 in: 18th International

Geological Congress, London, Part VII, Symposium

of Section F (K.C. Dunham, editor).

Fournier R.O. & Truesdell A.H. (1973) An empirical

Na�K�Ca geothermometer for natural waters.

Geochimica et Cosmochimica Acta, 37, 1255�1273.

Helgeson H.C. & Kirkham D.H. (1974) Theoretical

prediction of the thermodynamic behavior of aqu-

eous electrolytes at high pressures and temperatures;

I. Summary of the thermodynamic/electrostatic

properties of the solvent. American Journal of

Science, 274, 1089�1198.

Helgeson H.C., Delany J.M., Nesbitt H.W. & Bird D.K.

(1978) Summary and critique of the thermodynamic

properties of rock-forming minerals. American

Journal of Science, 278-A, 1�229.

Helgeson H.C., Kirkham D.H. & Flowers G.C. (1981)

Theoretical prediction of the thermodynamic beha-

vior of aqueous electrolytes at high pressures and

temperatures. IV. Calculation of activity coefficients,

osmotic coefficients and apparent molal and standard

and relative partial molal properties to 600ºC and

5 kbar. American Journal of Science, 281,

1249�1516.

Henley R.W., Truesdell A.H. & Barton P.B. (1984)

Fluid-mineral equilibria in hydrothermal systems.

Reviews in Economic Geology, 1, 1�267.

Johnson C.T., Helsen J., Schoonheydt R.A., Bish D.L. &

Agnew S.F. (1998) Single-crystal Raman spectro-

scopic study of dickite. American Mineralogist, 83,

75�84.

Miletic G. (1995) The structure of the lead and zinc

deposit at Crnac (in Serbian with English summary).

Pp. 299�304 in: Geology and Metallogeny of the

Kopaonik Mt. Symposium, Kopaonik, Belgrade.

Murray H.H. (1988) Kaolin minerals: their genesis and

occurrences. Pp. 67�89 in: Hydrous Pyllosilicates

(exclusive of micas) (S.W. Bailey, editor). Reviews

in Mineralogy, 19, Mineralogical Society of

America, Washington, D.C.

Nesbitt B.E. & Prochaska W. (1998) Solute chemistry of

inclusion fluids from sparry dolomites and magne-

sites in Middle Cambrian carbonate rocks of the

southern Canadian Rocky Mountains. Canadian

Journal of Earth Sciences, 35, 546�555.

Pavlovic S. & Todorovic Z. (1961) Sulphide miner-

alisation and Pb-Zn ore types at Rogozna Mt. (in

Serbian). Glas CCXLV, 21, 104�105, Belgrade.

Pitzer K.S. (1991) Ion interaction approach: theory and

data correlation. Pp. 76�153 in: Activity Coefficient

in Electrolyte Solutions (K.S. Pitzer, editor). CRC

Press, Boca Raton, Florida, USA.

Schumacher F. (1954) The ore deposits of Yugoslavia

and the development of its mining industry.

Economic Geology, 49, 451�492.

Urosevic M., Pavlovic Z., Klisic M., Brkulovic T.,

Malesevic M. & Trifunovic S. (1966) General

geological map of SFRJ 1:100 000, sheet Novi

Pazar. Federal Geological Survey, Belgrade.

Wiewiora A., Wieckowski T. & Sokolowska A. (1979)

78 S. S. Palinkas et al.

The Raman spectra of kaolinite sub-group minerals

and of pyrophyllite. American Mineralogist, 35,

5�14.

Zhang Y.G. & Frantz J.D. (1987) Determination of the

homogenization temperatures and densities of super-

critical fluids in the system NaCl-KCl-CaCl2-H2O

using synthetic fluid inclusions. Chemical Geology,

64, 335�350.

Zotov A., Mukhamet-Galeev A. & Schott J. (1998) An

experimental study of kaolinite and dickite relative

stability at 150�300ºC and the thermodynamic

properties of dickite. American Mineralogist, 83,

516�524.

Dickite and kaolinite from northern Kosovo 79