Mineralogical Magazine, October 2005, Vol. 69(5), pp. 695±706
Mineralogical controls on storage of As, Cu, Pb and Zn
at the abandoned Mathiatis massive sulphide mine, Cyprus
K. A. HUDSON-EDWARDS1,* AND S. J. EDWARDS2
1 Research School of Earth Sciences at UCl-Birkbeck, Birkbeck, University of London, London WC1E 7HX, UK
2 Department of Earth and Environmental Sciences, University of Greenwich at Medway, Chatham Maritime, Kent
ME4 4TB, UK
ABS TR AC T
The Mathiatis massive sulphide deposit in Cyprus was a low-grade (0.3% Cu), three million ton ore
body of pyrite and minor chalcopyrite occurring within basaltic lavas of the Troodos ophiolite.
Cessation of mining in 1987 left a deep open pit surrounded by large heaps of spoil, which are
undergoing oxidation and leaching. The aim of this study was to determine the mineralogical controls
on the storage and potential remobilization of As, Cu, Pb and Zn within, and from, mine spoil heaps.
Most of the spoil samples collected, and related materials (stream sediment, reaction zone between a
boulder of massive pyrite and calcareous chert, salt crusts on stream beds), are enriched in As
(27ÿ220 ppm), Cu (110ÿ400 ppm), Pb (10ÿ140 ppm) and Zn (290ÿ12,000 ppm) relative to both the
basalt and calcareous chert (As 4ÿ10 ppm, Cu 20ÿ76 ppm, Pb 3ÿ6 ppm, Zn 39ÿ200 ppm).
Arsenic, Cu, Pb and Zn in the spoil and related materials are associated with Fe(-Al-S)-O, Fe(-AlMg)-S-O, Al(-Mg-Fe)-S-O and Mg(-Al-Fe)-S-O phases (the brackets represent minor components of
less than 20 wt.% within the phases). Chemical extraction work using CaCl2 suggests that Cu, Zn and
to some extent, As, are potentially more soluble than Pb. This is corroborated by the very high total
concentrations of Cu and Zn in both the secondary salt crusts and the reaction zone material, high
CaCl2-extractable As, Cu and Zn in the salt crusts, and aqueous data for the Mathiatis mine area
collected for a European Union LIFE report. This may have implications for ecosystem health and
water quality in the Mathiatis area and areas of similar mineralogy and climate world wide.
K EY WORDS :
mine spoil, arsenic, copper, lead, zinc, Mathiatis, Cyprus, sulphate.
Introduction
MINE spoil is a rich source of potentially toxic
metallic and metalloid elements to the Earth's
surface environment. In the EU alone there are
400 million tonnes from extractive industries, a
large proportion of which is mine waste
(including quarrying) (http://www.minesandcommunities.org/Action/press456.htm; accessed 1
January 2005). In many areas, the spoil is
uncontrolled and left to weather, causing a
potential threat to water and soil systems, and to
their indigenous organisms. It is important to
* E-mail: k.hudson-edwards@geology.bbk.ac.uk
DOI: 10.1180/0026461056950281
#
2005 The Mineralogical Society
understand the mineralogical controls on metallic
and metalloid elements in these systems, since
they will determine the degree to which these
elements will be redistributed should environmental conditions change.
Cyprus, in the eastern Mediterranean, hosted
numerous, relatively small, massive sulphide
mines that were exploited in historical times,
and that are now characterized by large piles of
mine spoil, acidic pit waters and metal-rich
sediments (Edwards ., 1996). Of these, the
Mathiatis mine provides a good case study area to
examine the mineralogical controls on metallic
and metalloid element mobility, since it hosts
large mine spoil piles and carbonate-bearing
rocks, which may promote acid-neutralizing
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K. A. HUDSON-EDWARDS AND S. J. EDWARDS
reactions. This paper, therefore, aims to characterize the mineralogical hosts of As, Cu, Pb and
Zn at the Mathiatis mine in Cyprus, and their
processes of formation and long-term stability.
Methods and materials
Geology and mining history of the Mathiatis
massive sulphide deposit, Cyprus
Mathiatis mine (33ë21 E, 34ë58 30 N) lies in the
eastern part of the Troodos ophiolite, in the
volcanic sequence, between the villages of Agia
Varvara and Mathiatis. The Mathiatis deposit was
a typical example of a Cyprus-type Cu-bearing
massive sulphide ore body (Constantinou, 1980).
It consisted of a lower mineralized stockwork
zone and an overlying lens of massive sulphide
capped by ochre. This mineralized sequence
consisted of mainly pyrite and marcasite with
minor chalcopyrite and was overlain, in turn, by
unmineralized lavas, umbers, calcareous cherts
and chalks.
The Mathiatis deposit is one of the 30 or so
sulphide deposits in the Troodos ophiolite that
have been mined over the past 5000 years.
Ancient slags occurring in the area surrounding
Mathiatis attest to small-scale mining and
smelting operations that date back to at least
Roman times. Although the modern mine at
Mathiatis opened during the 1930s, large scale
extraction did not commence until 1965, and this
was completed in the mid-1980s. Over this
period, approximately three million tonnes of
low grade (averaging 0.3 per cent Cu) copper ore
were removed. The abandonment of Mathiatis
mine in the mid-1980s left a deep pit, now hosting
a lake fed by surface runoff, surrounded by piles
of mineralized and unmineralized spoil. The spoil
is estimated to be of the order of 10.5 million
tonnes (Charalambides
., 1998) and
comprises sediment ranging in size from ®ne
clay- and silt-sized particles to boulders
exceeding 1 m in diameter. The waste was
dumped to form ¯at-topped piles with steepsided slopes, some of which have failed.
Precipitation ponds on the ¯at surfaces and
drains through the piles or washes down the
slopes, causing gullying and transporting mainly
clay-, silt- and sand-sized particles onto adjacent
farmland and into stream beds. Sulphidic waste,
particularly that containing pyrite, is quite
obviously oxidizing and giving rise to sulphurous
gases and a plethora of colourful secondary
minerals, which appear to be responsible for
cementing the waste sediment in the spoil piles.
'
'
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696
Sampling took place in September 1999.
Sampling efforts were concentrated on the SE
side of the Mathiatis area because all of the mine
spoil tips and rock types were present and
exposed there (Fig. 1). Solid materials collected
included mine-spoil tip material, sediment from
dry stream beds, salt crusts on the surfaces of
stream beds and a reaction zone between massive
pyritic ore and calcareous chert. To establish
background values of As, Cu, Pb and Zn in the
area, samples of weathered calcareous chert and
basalt bedrock were also taken. All samples were
collected using a stainless steel trowel.
In the laboratory, the samples were homogenized, and a portion was air-dried, disaggregated and sieved to pass through a 2 mm aperture.
A sub-sample of the air-dried material was then
ground in an agate tema for 4 min. The samples
were digested in an HF-HClO4-HNO3 mixture
and analysed by ICP-MS (VG Elemental Plasma
Quad II+) for As, Cu, Pb and Zn. Analytical
precision was determined by inserting blind
duplicates to ~10% of the total number of
samples analysed. Precisions (2 ) were within
5% for Zn, and 12% for As, Cu and Pb. Analytical
trueness was determined using the reference
sediment standard GBW07311 (Of®ce of
Reference Materials, Laboratory of the
Government Chemist, UK). Estimates of trueness,
based on four replicates of this standard material,
were within 3% for Zn, 14% for Cu and As and
12% for Pb, and are regarded as acceptable for the
purposes of the study. Total sulphur was
determined by dry combustion using a LECO
instrument. Precision and trueness were within
10%.
Single batch chemical extractions have been
employed successfully to estimate the solubility
and potential environmental impacts of metallic
and metalloid elements in soils and sediments
(Vidal
., 1999). For this study, a single
chemical extraction using 0.01 M CaCl2, to
represent the fraction that is easily remobilized
after rainfall (cf. Pickering, 1986), was applied to
the samples. 1 g of sample was shaken at 20 rev/
min in 10 ml of 0.01 M CaCl 2 for 2 h
(Novozamsky ., 1993). The extractions were
performed in acid-washed, 25 ml erlenmeyer
¯asks. After shaking, the solutions were ®ltered
using Whatman no. 42 ®lter papers, made up to
50 ml volume and stored in polypropylene bottles
until analysis. For every eight samples, a
s
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MINERALOGICAL CONTROLS ON METAL STORAGE, CYPRUS
FIG. 1. Location of the abandoned Mathiatis mine, Cyprus, and of samples taken for this study.
duplicate sample and a blank were also extracted.
Two drops of 50% HNO3 (Aristar) were added to
prevent ¯occulation and sorption of metals onto
the bottle walls. Analyses for Cu, Pb and Zn were
carried out by inductively coupled plasma-atomic
emission spectroscopy (ICP-AES, Phillips instrument) and for As using atomic absorption
spectrophotometry (Unicam Soker system).
Precisions were better than 10%, except for
samples exhibiting very low concentrations
(<0.1 ppm).
Polished thin sections were made of all
samples, examined using a petrological microscope, and relative proportions of major minerals
697
estimated. All samples were analysed by X-ray
diffraction (Philips PW1710 instrument ®tted with
a graphite monochromator, with Cu-K radiation
at 40 kV/30 Ma operating conditions) for their
mineralogical compositions. The 2 range was
2ÿ60ë, step size 0.020ë and step time 1.25 s. The
relative proportions of the minerals identi®ed
were estimated using peak height, after calibrating to an aluminium standard. Elemental
analysis and X-ray element mapping for Fe, S,
O, As, Al, Zn, Cu and Mg were performed on a
CAMECA SC100 electron microprobe, with
operating conditions of 20 kV accelerating
voltage and 10 nA incident specimen current.
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K. A. HUDSON-EDWARDS AND S. J. EDWARDS
Results
Mineralogy of mine spoil and related products
X-ray diffraction (XRD) and petrological microscope analysis reveals that the basalt samples
consist of albite, anorthite, augite, chlorite,
diopside, kaolinite and quartz, with minor
calcite occurring mainly in amygdales, and the
calcareous chert samples comprise calcite, kaolinite, muscovite and quartz. The same analytical
techniques show that the mine spoil and stream
sediment samples contain the minerals found in
the basalt and calcareous chert, re¯ecting the fact
that they contain fragments of these two rock
types. In addition, they contain up to 25 vol.%
each of goethite, gypsum, hematite, jarosite,
kierserite, melanterite, illite, natrojarosite, pyrite,
quartz and vermiculite and in one stream sediment
sample, minor (<5 vol.%) ferrohexahydrite
(detected only by XRD). Electron microprobe
analysis (EMPA) and X-ray mapping suggest that
the mine spoil and stream sediments also contain
Al(-Mg-Fe)-S-O and Mg(-Al-Fe)-S-O phases
(that are probably X-ray amorphous), and
petrographic analysis of the areas analysed
suggests that these are relatively rare
TABLE 1. Total As, Cu, Pb, Zn and S concentrations of mine spoil, stream sediment, salt crusts, reaction zone,
basalt and calcareous chert.
Sample
Description
(ppm)
As
(ppm)
Mine spoil
MAT8
Basaltic spoil
10
MAT9
Basaltic spoil
27
MAT10
Basaltic spoil
63
MAT15
Basaltic spoil
76
MAT22
Massive pyrite
220
Stream sediment
MAT17
30
MAT19
53
MAT20
49
MAT14
64
MAT13
50
MAT12
71
MAT11
120
MAT6
110
MAT5
130
MAT4
27
MAT3
43
MAT2
41
MAT1
45
Salt crusts on stream bed
MAT24
38
MAT25
41
Contact zone between MAT22 and MAT23
MAT21
46
Basalt
MAT7
9
MAT26
4
MAT27
5
Calcareous chert
MAT16
8
MAT18
10
MAT23
10
698
Cu
(ppm)
Pb
(ppm)
Zn
(%)
S
(%)
75
190
160
240
110
3
19
50
41
150
220
440
410
290
500
0.41
0.03
5.19
7.57
17.8
180
170
320
280
300
250
310
200
210
150
190
170
170
21
13
22
32
21
59
68
78
140
27
100
58
85
350
800
340
570
840
630
660
440
670
570
590
480
530
1.12
3.78
6.46
5.37
6.24
7.30
4.90
5.70
5.66
2.54
3.03
4.18
4.46
280
350
20
10
1300
1300
8.21
9.13
400
4
12000
9.37
76
56
63
6
5
6
200
160
180
0.01
0.02
0.04
22
20
48
3
5
5
51
39
81
0.01
0.01
0.09
MINERALOGICAL CONTROLS ON METAL STORAGE, CYPRUS
(<5 vol.%). On the mine spoil tips, swallow-tail
crystals of secondary selenite line many of the
deep gully cracks.
The reaction zone (sample MAT 21) consists of
gypsum, quartz and hydronium jarosite (detected
by XRD), as well as an amorphous Fe(-Al-S)-O
oxide phase (suggested by EMPA and X-ray
mapping; the brackets around the elements here
and below represent minor components of
<20 wt.% within the phases). The XRD and
petrographic microscope analysis suggest that
the calcareous chert comprises calcite, kaolinite
and quartz, and the pyrite boulder, abundant
pyrite and quartz, and minor (<5 vol.%) hydronium jarosite, gypsum and sphalerite.
The XRD analysis of the secondary salt crusts
show that they contain hematite and a wide range
of hydrous Fe sulphates including copiapite,
melanterite, natrojarosite and rozenite, as well as
other minerals including gypsum, paragonite and
minor (<5 vol.%) quartz. Petrographic, EMPA
and X-ray mapping suggest that X-ray amorphous
Al(-Mg-Fe)-S-O and Mg(-Al-Fe)-S-O phases are
also present in abundances of <25 vol.%.
Total and CaCl2-extractable concentrations of As, Cu, Pb,
Zn and S
All but one of the mine spoil samples (MAT8),
stream sediments, salt crusts and reaction zone
materials are enriched in As, Cu, Pb and Zn by
two to 200 times relative to both the basalt and
calcareous chert (Table 1). The mine-spoil and
mine-spoil reaction products also contain some S
(Table 1). The reaction zone sample (MAT21)
exhibits the highest concentrations of Cu and Zn
of all the samples, intermediate concentrations of
As and low concentrations of Pb, whereas the
secondary salt crusts exhibit the second-highest
concentrations of Zn of all the sample media,
intermediate concentrations of As and Cu, and
low concentrations of Pb. Copper and Zn are the
most easily extracted using CaCl2, followed by As
and Pb (Fig. 2). The salt crusts exhibit the highest
concentrations of CaCl2-extractable As, Cu and
Zn of all of the sample types (both in terms of
absolute concentrations and percentages of total
concentrations), and the basalt and chert, the
lowest. Between 60 and 83% of the total Zn, As
FIG. 2. Absolute concentrations (in ppm) and percentages of total concentrations for 0.01 M CaCl2 extractions of
mine spoil, reaction zone, salt crust, stream sediment, basalt and chert samples at Mathiatis.
699
K. A. HUDSON-EDWARDS AND S. J. EDWARDS
and Cu in the two Mathiatis salt crust samples are
CaCl2-soluble, suggesting that these elements will
be easily mobilized after rainfall. This is likely to
occur frequently: secondary salts at the nearby Sia
Mine in Cyprus have been observed by Wong and
Malpas (2000) to readily dissolve in the run-off
resulting from the ®rst precipitation following a
dry period, especially during the winter months
from November to February.
Between 10 and 100 ppm Cu and Zn will be
mobilized from mine spoil and stream sediment
materials, and <1 ppm Zn from the basalt and
chert, following rainfall (Fig. 2). These values
represent <10% of the total amount of Cu and Zn
present in these materials. Stream sediment
samples MAT12 and MAT14 exhibit the highest
concentrations of CaCl2-soluble As, Cu and Zn of
all the stream sediments. MAT14 was sampled
downstream of the spoil heap represented by
sample MAT15, which also has elevated CaCl2soluble As (1.2 ppm), Cu (20 ppm) and Zn
(46 ppm): it is therefore possible that the
dissolution of soluble As, Cu and Zn from the
MAT 15 spoil heap may have contributed to the
total As, Cu and Zn in MAT14. MAT12 was
sampled downstream of the contact between the
mine spoil and calcareous chert; its elevated
CaCl2-soluble As (2.4 ppm), Cu (70 ppm) and Zn
(260 ppm) may be a product of reactions between
these two materials.
Mg(-Al-Fe)-S-O phases (Fig. 3). The Fe(-Al-S)-O,
Al(-Mg-Fe)-S-O and Mg(-Al-Fe)-S-O phases
have been reported in the section on the
`mineralogy of mine spoil and related products'
above, and it is likely that the Fe(-Al-Mg)-S-O
phases represent the jarosite, natrojarosite, hydronium jarosite, ferrohexahydrite, copiapite, melanterite and rozenite also reported in that section
and detected by XRD. Similarly, the Fe(-Al-S)-O
phases probably include the XRD-detected
goethite and hematite, and the X-ray amorphous
phase in MAT 21 described in the section on the
`mineralogy of mine spoil and related products'
above. These associations suggest that there may
be a large degree of substitution or sorption of Fe,
Al and Mg on the oxide and sulphate phases, or
sulphate mineral solid solution series involving
these three elements. This has been discussed in
the literature: melanterite, for example, has been
shown to contain up to 2 mol.% Mg (Alpers .,
1994), melanterite, rozenite and copiapite, several
mol.% of Mg (Jerz and Rimstidt, 2003) and Mg
sulphate salts such as epsomite, some Fe (Palache
., 1951).
Arsenic is mainly associated with Fe(-Al-Mg)S-O phases, and particularly, with Fe(-Al-S)-O
phases (Fig. 3). The association of As with Fe
oxyhydroxides and oxyhydroxysulphates is welldocumented in mining areas affected by sulphide
oxidation (e.g. Foster
., 1998; HudsonEdwards
., 1999; Savage
., 2000;
Courtin-Nomade ., 2003). In the salt crusts
and to a lesser extent, the mine spoil and stream
sediments, Mg(-Al-Fe)-S-O phases also contain
As (Fig. 4 ); this association, by contrast, has
been poorly documented. The Al(-Mg-Fe)-S-O
phases contain little As.
Copper and Zn show similar associations in
both the X-ray maps and the microprobe analysis
(Figs 3, 4 ). These elements are mainly associated
with Fe(-Al-S)-O and Fe(-Al-Mg)-S-O phases
(Fig. 4 ), and occur to a lesser extent in the
Mg(-Al-Fe)-S-O and Al(-Mg-Fe)-S-O phases. All
of these Cu- and Zn-bearing phases are intimately
intergrown and interbanded with gypsum.
Substitution of Cu and Zn in Fe and Mg sulphate
minerals has been clearly demonstrated by
Jambor . (2000).
Where Pb was detected, it was associated with
Fe(-Al-Mg)-S-O and Fe(-Al-S)-O phases (Fig. 3).
The association of Pb with Fe oxyhydroxysulphate minerals such as jarosite, plumbojarosite or
beudantite is well known (Hudson-Edwards .,
1999; Dutrizac and Jambor, 2000).
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Discussion
Mineralogical controls on storage of As-, Cu-, Pb- and Znbearing mine spoil and reaction products
T-tests reveal that there are no signi®cant
differences between total As, Cu, Pb and Zn
concentrations for the mine spoil and stream
sediment samples (Table 1). This may re¯ect the
fact that the streams are directly supplied by
runoff from the mine spoil tips, and that the As,
Cu, Pb and Zn could, therefore, be related to
detrital phases that are eroded from the mine spoil
tips. In the reaction zone, however, Cu and Zn
concentrations exceed those of its parent materials
MAT22 and MAT23, and the chemical reactions
that produced it may result in a net accumulation
of these elements in the zone, and a net depletion
from the pyrite and the chert, as well as additions
from rain and groundwater.
Electron microprobe analysis shows that As, Cu,
Pb and Zn in the mine spoil and reaction products
are associated with pyrite and with Fe(-Al-S)-O,
Fe(-Al-Mg)-S-O, Al(-Mg-Fe)-S-O and
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MINERALOGICAL CONTROLS ON METAL STORAGE, CYPRUS
FIG. 3. EMPA data plots for As, Cu, Pb and Zn. The Fe-S-O phases include the Fe(-Al-S)-O and the Fe(-Al-Mg)-S-O
phases. Samples that plot near zero have below-detection limit concentrations of As, Cu, Pb and Zn.
Formation of As, Cu, Pb and Zn-bearing secondary phases
at Mathiatis
The oxidation of pyrite and other sulphide
minerals in abandoned massive sulphide mines
results in the formation of acid waters that carry
considerable quantities of metallic and metalloid
ions (Nordstrom, 1982; FoÈrstner and Wittman,
1981; Boult ., 1994; Hudson-Edwards .,
1999). These acid waters are often attenuated
naturally either by chemical reactions with host
rocks offering a high degree of buffering capacity
(such as limestones), or where the drainage mixes
with surrounding waters (Chapman ., 1983).
These processes result in increases in aqueous pH,
effectively neutralizing the acidity, which in turn
cause precipitation of secondary phases such as
Fe oxides, hydroxides, oxyhydroxides and/or
hydroxysulphates that co-precipitate or sorb
metallic and metalloid elements (Langmuir and
Whittemore, 1971; Nordstrom, 1982; Chapman
., 1983; Johnson, 1986; Hochella ., 1999).
At Mathiatis, these phases, and remobilized mine
spoil, form a considerable proportion of the
sediment found in streams draining the mine.
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701
In the Mathiatis area, reactions between the
pyritic (and other sulphide mineral) mine spoil,
surrounding calcareous chert and basalt have
resulted in the formation of metallic and metalloid
element-bearing, secondary Fe oxides and
oxyhydroxides (hematite, goethite, amorphous
Fe oxyhydroxide; the Fe(-Al-S)-O phases) and
oxyhydroxysulphates (jarosite, natrojarosite,
soluble sulphates such as copiapite; the Fe(-AlMg)-S-O phases), as seen in other mining areas,
as well as Mg(-Al-Fe)-S-O and Al(-Mg-Fe)-S-O
phases. The Mg sulphate phase may be kieserite
(detected by XRD), and the Al sulphate,
basaluminite, a phase common in acid-mine
drainage areas, forming at pH values of 5 or
above (Nordstrom
., 1984; Nordstrom and
Alpers, 1999), or a soluble Al sulphate salt such
as alunogen or meta-alunogen (Jambor
.,
2000). The Mg and Al could come from the
weathering of the silicate minerals found in the
abundant basalt in the area (cf. Jambor, 2000).
Secondary salt crusts such as those at Mathiatis
have been observed in many other mine drainage
systems (e.g. Nordstrom, 1982; Alpers
.,
1994; Bayless and Olyphant, 1993; Hudsonet al
et al
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K. A. HUDSON-EDWARDS AND S. J. EDWARDS
FIG. 4. X-ray colour maps: (
) MAT 25 showing association of As with an Mg-Al-S-O-bearing phase;
(
) MAT14 showing an association of Cu and Zn with Fe-Al-Mg-O-bearing phases.
a above
b facing page
Edwards ., 1999; Buckby ., 2003). They
are thought to form by the evaporation of acidic
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702
drainage waters, precipitation of upward-moving
pore water by capillary action (i.e. ef¯orescent
MINERALOGICAL CONTROLS ON METAL STORAGE, CYPRUS
salts) or through the oxidation of pyrite under
humid conditions (Alpers ., 1994; Wong and
Malpas, 2000). The ®rst two processes appear to
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703
be occurring at Mathiatis, as no pyrite was found
in the stream bed. Pyrite does, however, occur in
the abandoned Mathiatis pit and in other pyritic
K. A. HUDSON-EDWARDS AND S. J. EDWARDS
At Mathiatis, the high concentrations of CaCl2soluble As, Cu and Zn in the salt crusts suggest
that, after dissolution of these phases, these
elements will be released to local waters. The
greater solubility of Cu and Zn relative to Pb and,
in some cases, As, in these crusts and some of the
stream sediment and mine waste samples, has
been demonstrated for other areas affected by acid
mine drainage (e.g. tailings leachates, Sweden,
Lin, 1997; alluvium, RõÂo Tinto, Spain, HudsonEdwards ., 1999). The different af®nities that
secondary phases have for Cu and Zn relative to
As and Pb may play a large role in this greater
solubility. The sorption of As and Pb onto Febearing precipitates in acid mine drainage areas,
for example, is thought to occur at pH 4.5ÿ5,
whereas sorption of Cu and Zn occurs at more
neutral pH (Smith, 1999). Thus, as long as the pH
remains below 4.5ÿ5, Cu and Zn are likely to be
more soluble. The solubility of the sorbing
minerals also plays a large role: Lin (1997)
suggested that the relative immobility of As and
Pb were due to sorption on insoluble Fe
oxyhydroxides (such as goethite) and hydrocerussite, respectively, whereas the mobility of Cu
and Zn were due to their incorporation in soluble
Fe sulphate salts. Some or all of these factors may
be responsible for the differing solubilities seen at
Mathiatis.
waste on the northern side of the area, and salt
crusts can be frequently observed coating these
sulphides. The salt crusts pose a potential threat to
mining ecosystems because their stored acidity
and metallic and metalloid elements (see below)
can be released to mining ecosystems when the
minerals are dissolved by recharge or runoff, and
when the Fe or Al undergoes hydrolysis (Alpers
., 1994; Jerz and Rimstidt, 2003), and because
their released ferric ion can oxidize pyrite and
result in further acid discharge (Cravotta, 1994).
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Long-term storage of As, Cu, Pb and Zn at Mathiatis and
other similar mining areas
The small amounts of soluble As, Cu, Pb and Zn
in all of the sample media except the salt crusts at
Mathiatis suggest that these elements are not
likely to be dissolved during rainfall at neutral
pH. The Mathiatis Fe(-Al-S)-O and Fe(-Al-Mg)S-O phases, which host considerable amounts of
As, Cu, Zn and, to a lesser extent, Pb, are likely to
be relatively insoluble under near-surface
oxidizing conditions, but may dissolve in the
longer-term due to reduction after burial and early
diagenesis. Many Al sulphates that form in acid
mine drainage environments (and are inferred to
form at Mathiatis) also have low solubility
(Bigham and Nordstrom, 2000). The incorporation of Cu and Zn in products such as the reaction
zone sample (MAT21, Table 1), and, in turn, their
relatively small amounts of CaCl2-soluble Cu and
Zn (Fig. 2), suggests that much of the Cu and Zn
will be stored for a potentially long period.
Relatively small amounts of CaCl2-soluble As
and Pb in all materials except the salt crusts also
implies that these elements may also undergo
long-term storage in the solid media.
These assertions are supported by data from a
recent European Union LIFE report (Charalambides
., 1998), in which most of the water samples
taken from open wells, boreholes, springs and
streams in the Mathiatis area exhibit relatively
small dissolved concentrations of As and Cu
(generally <10 ppb), Pb (<0.5 ppb) and Zn
(<100 ppb). By contrast, water samples from the
mine pit show elevated concentrations of Cu
(3260ÿ5360 ppb), Pb (3.05ÿ58.4 ppb) and Zn
(19600ÿ23000 ppb), particularly at the end of the
wet season. These correlate with high aqueous Fe
and SO4 concentrations, suggesting that they might
be the result of pyrite oxidation, or of the dissolution
of large amounts of soluble sulphate salt crusts that
line the pit walls and cement the spoil sediment.
Conclusions
Arsenic, Cu, Pb and Zn in mine spoil, stream
sediments, a reaction zone between pyrite and
calcareous chert, and stream bed salt crusts are
associated mainly with Fe(-Al-Mg-)-S-O and
Fe(-Al-S)-O phases, and to a lesser extent, Al(Mg-Fe)-S-O and Mg(-Al-Fe)-S-O phases. As in
other mining-affected areas, soluble Fe sulphate
minerals that form salt crusts control the potential
mobility of As, Cu and Zn, but there is evidence at
Mathiatis that the Al and Mg sulphates may also
be important. Overall, As and Pb appear to be less
soluble than Cu and Zn, which is probably due to
mineralogical factors and, possibly, the relative
sorption of these elements on the Fe, Al and Mg
oxide and sulphate phases.
et al
Acknowledgements
704
The authors would like to thank the Geological
Survey Department, Nicosia, Cyprus, for their
support for the project and for making available
the European Union LIFE data. We also thank
MINERALOGICAL CONTROLS ON METAL STORAGE, CYPRUS
S. Hirons for XRD analysis and S.L. Houghton for
carrying out the CaCl2 extractions. A portion of
the laboratory work was carried out using Wolfson
Laboratory for Environmental Geochemistry facilities (Research School of Earth Sciences at UCLBirkbeck, University of London), and additional
analysis was done using the NERC ICP-AES
Facility at RHUL, with the permission of its
Director, Dr J.N. Walsh. We also acknowledge the
assistance of D.A. Plant and the facilities of the
NERC Electron Microprobe Facility at the
University of Manchester. This work was funded
by the University of London Central Research
Fund, the Birkbeck Faculty of Science and the
Department of Earth and Environmental Sciences,
University of Greenwich. We appreciate the
comments of two anonymous reviewers and
guest editor Eva Valsami-Jones that greatly
improved the manuscript.
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[
]
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International Journal of Environmental Analytical
Chemistry 51
The
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Applied Geochemistry 15
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Manuscript received 24 January 2005:
revised 11 July 2005
706
the
Eastern