DISTRIBUTION OF ANTIMONY IN GROUNDWATER

N. M. Shvartseva

(Presented by Prof. P. A. Udodov)

The geochemistry of antimony has been poorly studied. Its average content in the Earth’s crust is \(4 \cdot 10^{-5}\) percent by weight. It is concentrated in sulfide ores. In nature, antimony is only rarely found in native form. In its chemical compounds it is trivalent and pentavalent. The principal minerals of antimony are: valentinite, senarmontite, cervantite, stibiconite, and antimonite. Compounds of antimony with sulfur (antimonite) are the most common in nature. In its compounds it often plays the role of a metal rather than a metalloid. Antimony forms the sulfate, \(\mathrm{Sb(SO_4)_3}\), which is unstable in water and rapidly hydrolyzes. Antimony chloride also hydrolyzes rapidly (Emmons, 1935). Among the chemical properties of antimony, an important one is the ability of its sulfide to dissolve readily in aqueous solutions of alkali sulfides, with the formation of the readily soluble complex ion \(2(\mathrm{SbS_3})'''\) (Poyarkov, 1955).

The chemical properties of antimony and its compounds indicate the possibility of their presence in the waters of sulfide deposits, which was first confirmed by the studies of V. Emmons (1935) and S. S. Smirnov (1955). Thus, in the waters of mines whose ores contain much antimony in the form of sulfide, very little antimony was encountered, usually only as traces. However, antimony was found in acid waters at Philipsburg in Butte, Montana, and in several other places. According to O. Weigel (Emmons, 1935), the solubility of antimony sulfide \((\mathrm{Sb_2S_3})\) in pure water at \(t = 18^\circ\) is \(5.2 \cdot 10^6\) moles per 1 liter. Cook’s experimental data on the dissolution of antimonite under conditions close to those of the oxidation zone showed that from 1 g of antimonite, after 84 days, up to 0.0175 g of \(\mathrm{SbO_4}\) passes into the water. The rate of oxidation under water–air conditions proved to be comparatively high (Emmons, 1935).

Field observations by S. S. Smirnov (1955) indicate that oxidation of antimonite in the ordinary type of its ores (quartz–antimonite) proceeds much more slowly than in the case of oxidation of antimonite enclosed in complex ores. Therefore antimonite in the zone

of oxidation may be moderately stable and weakly stable. The principal products obtained in the oxidation of antimonite and other antimony minerals have considerable solubility (up to thousandths of a gram per 1 l of water), which indicates a noticeable migratory capacity of antimony under the conditions of the oxidation zone.

Of all the most important antimony compounds that can arise in the oxidation zone, the alkaline salts of antimonic acid possess significant solubility in comparison with antimony oxides. Thus, S. S. Smirnov (1955) showed that the solubility of potassium antimonite \((\mathrm{K}_2\mathrm{H}_2\mathrm{Sb}_2\mathrm{O}_7)\) is determined as 27.4 g/l at \(20^\circ\mathrm{C}\), and that of sodium pyroantimonite as 0.3 g/l at \(12.3^\circ\mathrm{C}\). In addition to the transport of antimony in the form of alkaline antimonites, migration in strongly acidic solutions in the form of polysulfides may also be of importance.

In the same work it is stated that, in individual cases, undoubted redeposition of antimony in oxidized ores was observed, and it was found in single analyses of mine waters.

In the very near-surface parts of the oxidation zone of quartz-antimonite deposits, S. S. Smirnov (1955) often observed an almost complete removal of antimony from the ore mass. In his opinion, under such conditions one may expect widespread formation of fine suspensions and, possibly, even colloidal solutions. He also suggests that sometimes analogous phenomena may occur in deeper parts of the oxidation zone.

On the basis of the foregoing, it may be assumed that antimony is capable of migrating in the form of suspensions, fine suspensions, and colloids in the waters of the oxidation zone of sulfide deposits.

And the fact that antimony has been found in groundwaters at up to 3100 and 3900 μg/l (Udodov et al., 1965; Mukimova, 1962), confirms its good migratory capacity.

The migration coefficient for antimony was first calculated by P. A. Udodov (Udodov et al., 1962), who, using the example of groundwaters of Siberia, assigned it to the 2nd group in terms of distribution, with a coefficient of aqueous migration \(A = 0.9 \cdot 10^{-4}\). This value indicates a good migratory capacity of antimony, which makes it possible to assign it to the first group—the migrating elements. D. S. Mukimova (1969) gives the coefficient of aqueous migration for the river waters of Central Asia as \(A = 0.4 \cdot 10^{-3}\), which proved to be higher than “\(A\)” for groundwaters.

In recent years many investigators have established the presence of antimony in surface and groundwaters, in waters of zones of tectonic disturbances, in thermal springs, in waters of permafrost regions, in saline groundwaters, and also in seawater.

For a general idea of the distribution of antimony in groundwaters, a graph is presented (Fig. 1), from which it is evident that there is no clearly expressed dependence between mineralization and the antimony content. However, it may be said that in saline waters, apparently, a considerable concentration of antimony is possible. From this figure one may tentatively judge the background content of antimony in groundwaters, which here is taken as 5 μg/l (the upper limit of the background).

It is not yet possible to speak of the background content of antimony in groundwaters because of the lack of data. However, we have the results of studies by D. S. Mukimova (1969), who, for the river waters of Central Asia, gives antimony contents from 30 to 200 μg/l with an aqueous-migration coefficient \(A = 0.4 \cdot 10^{-3}\). These quantitative characteristics indicate that antimony may occur in river waters in significant concentrations and migrate well. In groundwaters, antimony occurs rather often, especially in regions of mineralization zones or deposits known to us.

Fig. 1. Distribution of antimony in natural waters.
1—surface waters, 2—groundwaters, 3—mine waters, 4—waters of hydrothermal systems, 5—saline waters, 6—upper background limit (UBL)

For a number of years, hydrogeochemical investigations were carried out by us in the area of the village of Semiluzhki (Tomsk Oblast), which confirmed the presence of an antimony mineralization zone. In the groundwaters of this area, which have a mineralization of 0.1–0.5 g/l and are characterized by a hydrocarbonate–magnesium composition with pH 6.5–7.6, up to 30 μg/l (occasionally 50 μg/l) of antimony was recorded. At the same time, in the waters of tectonic-dislocation zones in this area of work, antimony was found in amounts from 6 to 30 μg/l (Table 1). Antimony has also been found in the waters of a tungsten-mineralization zone (Transbaikalia), with contents of 0.5–8.0 μg/l, and in waters of antimony mineralization in an amount of 2.7 μg/l at pH 6.9 (Udodov et al., 1962). From these data it follows that in the waters of zones of antimony and tungsten mineralization, with water pH from 6.6 to 6.9, antimony is present in insignificant concentrations (from 0.5 to 2.7, occasionally up to 30 and 50 μg/l).

As a rule, in the waters of various deposits (copper–cobalt, antimony, and gold-ore), antimony is present in amounts greater than 5.0 μg/l. Thus, at the antimony (Razdolnoye) deposit, according to A. A. Lukin, antimony was found in the waters almost everywhere, with contents from 40 to 90 μg/l, and at a number of points increases in content up to 126–127 μg/l, occasionally up to 1030 μg/l, were observed (Table 1). At the same time, in the Saralinsk gold-ore field (Kuznetsk Alatau; V. I. Ivanov), the occurrence of antimony reaches 55%, the maximum content is 500 μg/l, and the average content is 23 μg/l. The magnitude of dispersion halos for antimony here is fairly considerable and reaches 1.5 km.

In recent years, a number of researchers (White, 1965; Smirnov, 1967; Ozerova, 1968; Mukimova, 1969, and others) have discovered the presence of antimony in thermal springs. Thus, in the Wyoming spring (USA, Yellowstone Park), antimony was found in an amount of 100 μg/l, and in the Steamboat spring (USA, Nevada), 400 μg/l (White, 1965). In the waters of thermal springs of Kamchatka and the Kuril Islands, antimony has been found at 150 to 400 μg/l (Ozerova, 1968, and others).

Of considerable importance is also the fact that antimony is found in the waters of regions of perennially frozen rocks. Its contents are small. Thus, in the northwestern part of the Siberian Platform, S. L. Shvar-

Table 1

Antimony content in groundwaters

Tseblym (1963, 1965) discovered antimony in bog waters with an average content of 1.7 µg/l, in waters of loose formations—2.8 µg/l, and in waters of bedrock—3.6 µg/l. In Transbaikalia, in the area of talik permafrost, antimony was found in all from 0.3 to 0.6 µg/l (Udodov et al., 1962). The literature sources contain isolated information on the presence of antimony in saline groundwaters. In this respect, the data of S. I. Smirnov (1967) are of interest—in the groundwaters of Searles Lake (California), antimony was found in an amount of 5000 µg/l. The waters of this lake have pH 9.7 and mineralization of 340—360 g/l. In this case, antimony in saline waters probably with

with an alkaline reaction, is capable of forming stable, readily soluble complex compounds.

Although antimony in waters is still poorly studied, on the basis of the data presented it is possible to draw the following preliminary conclusions:

1. Antimony is widely distributed in groundwater.
2. The presumed upper background limit for fresh groundwater is 5.0 μg/l.
3. Antimony can migrate in river waters in considerable quantities.
4. Maximum concentrations of antimony are observed not only in mine waters, but also in saline groundwater and in thermal springs.
5. Antimony is capable of forming aqueous dispersion flows around antimony and gold-ore deposits (possibly other deposits as well), which should be used in hydrogeochemical prospecting.

REFERENCES

1. Mukimova D. S. Mercury content in some rivers of Central Asia. VINITI, series Geology, Methods of Prospecting, No. 1, 1969.

2. Mukimova D. S. Hydrogeochemical dispersion halos of antimony-mercury deposits of Central Asia and their prospecting significance. Abstract. Tashkent, 1969.

3. Poyarkov V. E. Mercury and antimony. Issue 15, Moscow, 1955.

4. Smirnov S. I. Was ore-bearing fluoride discovered by a deep borehole in Southern California? Bull. MOIP, Geological Section, No. 3, 1967.

5. Smirnov S. S. Oxidation zones of sulfide deposits. Publishing House of the Academy of Sciences of the USSR, 1955.

6. White D. E. Thermal waters of volcanic origin. In: Geochemistry of Post-Magmatic Processes, Mir Publishing House, 1965.

7. Udodov P. A., Onufrienok I. P., Parilov Yu. P. Experience in hydrogeochemical investigations in Siberia. Vysshaya Shkola Publishing House, Moscow, 1962.

8. Udodov P. A., Matusevich V. M., Grigor’ev N. V. Hydrogeochemical prospecting under conditions of the semi-closed geological structures of the Tom–Yaya interfluve. TSU Publishing House, Tomsk, 1965.

9. Shvartsev S. L. Some results of investigations under permafrost conditions. Journal Geology of Ore Deposits, 1963, No. 2.

10. Shvartsev S. L. On the hydrogeochemical method of prospecting in northern swampy regions. Journal Geology and Geophysics, 1965, No. 7. Publishing House of the Siberian Branch of the Academy of Sciences of the USSR, Novosibirsk.

11. Emmons V. H. Secondary enrichment of ore deposits. Moscow—Leningrad, ONTI, 1935.