Nature of Oxidation of Gold-Sulfide Deposits and Methods for Processing Oxidized Ores
Abstract Generated abstract
This paper examines how hypergene oxidation changes the mineral composition and processing behavior of gold-sulfide ores, using the Kokpatas deposit as a representative case. The authors calculate element stability coefficients relative to primary ores, relate oxidation stages to mineral assemblages and gold occurrence, and compare cyanidation and flotation results across ores with different degrees of sulfide oxidation. They propose an iron-based formula for estimating oxidation degree and show that cyanidation recovery increases as sulfides oxidize, while flotation becomes more effective in less oxidized ores. On this basis, the study recommends separating reserves and processing routes for oxidized, mixed, and sulfide ores, with approximate oxidation boundaries of 85 to 90 percent and 30 percent.
Full Text
Oxidation Characteristics of Gold-Sulfide Deposits and Methods for Processing Oxidized Ores
I. M. Korobushkin, A. M. Glotov, N. A. Vasilkova (IRGIREDMET)
In recent years the gold-mining industry has begun to develop gold-ore deposits represented by zones of hydrothermally altered rocks with disseminated gold-bearing sulfides. Their characteristic feature is the finely dispersed nature of gold inclusions in pyrite, arsenopyrite, and chalcopyrite. Such gold is difficult to extract and requires the introduction of preliminary roasting into the technological cycle. Under surface conditions these ores acquire different technological properties.
The development of hypergene processes at such deposits leads to the oxidation of sulfides with the formation of limonites, jarosites, scorodites, and others. In the process of oxidation, gold is liberated from the sulfides and occurs in a free state or in the products of sulfide oxidation. The processing of such ores can be carried out according to a simpler and more economical flowsheet (direct cyanidation) with high extraction indices.
The transition zone from oxidized ores to primary ores has a complex mineral composition and is characterized by the presence of both sulfides and products of various stages of their oxidation, which makes it necessary to distinguish such ores as an independent type of mixed ores. The gold in them occurs in a finely dispersed state in sulfides and is also found in free form. Processing of mixed ores requires the use of combined flowsheets (flotation of gold-bearing sulfides and cyanidation of flotation tailings). Various technologies are used to extract gold from the sulfide concentrate: roasting followed by cyanidation, chloridizing volatilization, and autoclave leaching. Thus, three types of ores are identified, processed according to different technological flowsheets, as a result of which it is necessary to carry out separate reserve estimation for them and separate processing. The boundaries of the indicated types have gradual transitions, and their delineation at deposits by visual methods is impossible. The latter necessitates the development of criteria for their delineation using—
...use of analytical methods. The importance of this problem is obvious, and the present work is an attempt to solve it.
The Kokpatas deposit is a typical representative of gold-sulfide deposits, consisting of hydrothermally altered rocks in zones of crumpling and crushing with superimposed sulfide mineralization. The ore bodies have a complex lens-like form with swellings and pinches. They are composed mainly of quartz-chlorite schists, with subordinate amounts of aleurolites and sandstones. A veinlet-disseminated type of mineralization is characteristic of them. Early and late sulfides are distinguished in the composition of the ore mineralization. The early sulfides include pyrite and arsenopyrite. Their content in the ores ranges from 3 to 20%. The late sulfides include chalcopyrite, sphalerite, bournonite, tetrahedrite, bravoite, and other sulfides and sulfosalts of lead. Quantitatively, they are sharply subordinate and are of only mineralogical interest. The only valuable component in the ores is gold, the predominant part of which is bound as fine-dispersed dissemination in pyrite and arsenopyrite.
Under surface conditions, the ores are subjected to the action of hypergene processes, as a result of which the textural-structural features and the primary mineral composition of the ores change. As a result of their chemical transformation in the oxidation zone, there is extensive development of secondary minerals—limonites, jarosites, scorodite, gypsum, alunite, kaolin, and others.
In studying the behavior of the principal ore-forming elements in the oxidation zone, as a characteristic reflecting the degree of mobility of elements in the oxidation zone, we calculated their stability coefficients. The calculation of stability coefficients was carried out relative to the primary ores by the method of Smith–Polynov [1]. Silicon was taken as the witness element. Changes were introduced into the calculation procedure, consisting of the following. The method described is used to determine the migration coefficient. We are interested in the stability of elements in the products of oxidation. Therefore we introduced the concept of the stability coefficient, the value of which is determined by the ratio of the contents of elements in the oxidation products to their contents in the unaltered rocks. The results of the calculation are summarized in Tables 1 and 2. The relative stability of elements in the oxidation zone was established from the logarithms of the stability coefficients of the elements being compared. The value of the stability coefficients made it possible to compile stability series of the elements and to identify stages in the development of the oxidation zone.
According to the nature of stability, the elements are subdivided into: 1) practically immobile; 2) inert; 3) mobile and readily mobile (Tables 1, 2).
The first group includes elements with the greatest stability. Their accumulation takes place in the oxidation zone. Such elements are aluminum and silicon. The value of the stability coefficient is equal to 1 or more. The second group of elements is relatively inert to oxidation processes. It includes iron, whose stability coefficient is 0.8. Arsenic, sulfur, silver, calcium, and magnesium are assigned to the third and fourth groups. Their stability is variable. The value of the stability coefficient for the group of elements under consideration ranges from 0.1 to 0.8 (Table 1). The stability series of elements, compiled relative to ores with different degrees of oxidation, and their material composition make it possible to distinguish three stages in the development of oxidative processes.
Calculation of coefficients characterizing the stability of elements in the oxidation zone of the Konzhakovskoe deposit
Table 1
| Elements | Content in 100 g of ore with degree of oxidation, %, 0–30 | 30–50 | 50–80 | 80–100 | From 100 g of ore remained in ores with degree of oxidation, 30–50 | 50–80 | 80–100 | Coefficient of stability with respect to content in acidic waters, 30–50 | 50–80 | 80–100 | Coefficient of stability by stages, 30–50 | 50–80 | 80–100 | Logarithms of stability coefficients, 30–50 | 50–80 | 80–100 | Logarithms of stability coefficients by stages, 30–50 | 50–80 | 80–100 | Mobility degree of elements in relation to iron and second stage—serebrom, for ores with degree of oxidation 30–50 | 50–80 | 80–100 | Mobility degree of elements in relation to iron and second stage—serebrom, by stages 30–50 | 50–80 | 80–100 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Gold | \(7.9 \cdot 10^{-6}\) | \(6.45 \cdot 10^{-6}\) | \(3.3 \cdot 10^{-6}\) | \(4.15 \cdot 10^{-6}\) | \(5.6 \cdot 10^{-6}\) | \(2.9 \cdot 10^{-6}\) | \(3.3 \cdot 10^{-6}\) | 0.70 | 0.40 | 0.40 | 0.70 | 0.52 | 1.14 | −0.15 | −0.4 | −0.4 | −0.15 | −0.28 | 1.06 | 1.5 | 4.0 | 4.0 | 1.5 | 2.8 | stable |
| Silver | \(2.2 \cdot 10^{-6}\) | \(2.0 \cdot 10^{-6}\) | \(1.5 \cdot 10^{-6}\) | \(1.6 \cdot 10^{-6}\) | \(1.74 \cdot 10^{-6}\) | \(1.3 \cdot 10^{-6}\) | \(1.596 \cdot 10^{-6}\) | 0.80 | 0.60 | 0.80 | 0.80 | 0.80 | 0.97 | −0.1 | −0.23 | −0.23 | −0.1 | −0.2 | −0.06 | 1.0 | 2.3 | 2.3 | 1.0 | 1.0 | 1.0 |
| Iron | 7.2 | 6.7 | 6.7 | 7.0 | 5.8 | 5.8 | 5.5 | 0.8 | 0.8 | 1.0 | 0.8 | 1.0 | 1.0 | −0.1 | −0.1 | −0.1 | −0.1 | 0.00 | 0.00 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | stable |
| Sulfur | 4.9 | 4.45 | 2.6 | 0.55 | 3.9 | 2.3 | 0.44 | 0.80 | 0.5 | 0.1 | 0.80 | 0.6 | 0.2 | −0.1 | −0.3 | −1.0 | −0.1 | −0.22 | −0.7 | 1.0 | 3.0 | 10.0 | 1.0 | 2.2 | 12 |
| Arsenic | 1.86 | 1.6 | 1.10 | 1.0 | 1.40 | 0.96 | 0.80 | 0.8 | 0.5 | 0.40 | 0.8 | 0.7 | 0.8 | −0.1 | −0.3 | −0.4 | −0.1 | −0.15 | −0.1 | 1.0 | 3.0 | 4.0 | 1.0 | 1.5 | 2 |
| Silicon | 40.0 | 46.0 | 46.0 | 51.0 | 40.0 | 40.0 | 40.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | more stable | more stable | more stable | more stable | stable | stable |
| Calcium | 7.5 | 4.9 | 3.7 | 3.46 | 3.2 | 2.7 | 3.25 | 0.6 | 0.40 | 0.30 | 0.6 | 0.8 | 0.8 | −0.23 | −0.4 | −0.52 | −0.23 | −0.1 | −0.1 | 2.3 | 4.0 | 5.2 | 2.3 | 1.0 | 2 |
| Magnesium | 2.5 | 1.61 | 1.57 | 1.35 | 1.40 | 1.37 | 1.06 | 0.6 | 0.60 | 0.40 | 0.6 | 1.0 | 0.8 | −0.23 | −0.22 | −0.4 | −0.23 | 0.00 | −0.1 | 2.3 | 2.2 | 4.0 | 2.3 | stable | 2 |
| Aluminum | 12.0 | 14.2 | 17.1 | 16.6 | 12.3 | 14.9 | 13.0 | 1.0 | 1.20 | 1.1 | 1.0 | 1.2 | 0.9 | 0.00 | 1.08 | 1.04 | 0.00 | 1.08 | −0.05 | more stable | more stable | more stable | more stable | stable | 1.0 |
Rows of stability of elements:
I — for ores with degree of oxidation
II — for stages of oxidation, determined by the ratios:
a) \(30—50\%\)
\[ \mathrm{Al,\,Si>Fe,\,Ag,\,S,\,As,\,Au>Ca,\,Mg} \]
b) \(50—80\%\)
\[ \mathrm{Al,\,Si>Mg>Fe,\,Ag>As>Au>Ca>S} \]
c) \(80—100\%\)
\[ \mathrm{Al,\,Si>Fe>Au,\,As,\,Mg>Ca>S} \]
I stage
\(0—30\)
II stage
\(50—80\)
III stage
\(30—50\)
\(80—100\)
\(50—80\)
\[ \mathrm{Al,\,Si>Fe,\,Ag,\,S,\,As,\,Au>Ca,\,Mg} \]
\[ \mathrm{Al,\,Si,\,Fe,\,Mg>Ag,\,Ca>As,\,S>Au} \]
\[ \mathrm{Au,\,Si,\,Fe>Al,\,Ag>As,\,Mg,\,Ca>S} \]
a. Sulfate–arsenate stage. In this stage, aluminum and silicon are practically immobile elements. Their stability coefficient is equal to 1 (Tables 1, 2). A slight accumulation of aluminum relative to quartz is observed, as well as removal of iron, whose stability coefficient is 0.8. Sulfur, arsenic, and silver have mobility analogous to that of iron. In the material composition of the ores characterizing this stage, the formation of
Table 2
Stability series
| Stability series of elements | I stage, sulfate–arsenate | II stage, hydrogoethite–goethite | III stage, formation of anhydrous iron hydroxides | Value of the stability coefficient |
|---|---|---|---|---|
| Practically immobile | Al, Si | Al, Si | Si, Au | 1.0—1.2 |
| Inert (weakly mobile) | Fe, Ag, S, As | Fe, Mg | Ag, Fe, As, Ca, Al | 0.8—1.0 |
| Mobile | Mg, Ca, Au | Ag, Ca, As | Mg | 0.5—0.8 |
| Readily mobile | — | S, Au | S | 0.5 |
scorodite and jarosite is noted. As a result, it has been termed sulfate–arsenate. The more mobile elements are magnesium, calcium, and gold. In the material composition this circumstance is reflected in a decrease in the amount of carbonates. During the decomposition of sulfides, gold is, in all probability, removed with iron hydroxides.
b. Hydrogoethite–goethite stage is characterized, in comparison with the preceding one, by inert behavior of magnesium and iron. Aluminum continues to accumulate. Silicon remains immobile. Silver, calcium, and arsenic are mobile. Sulfur and gold migrate especially intensively (Table 2). In mineralogical terms, iron hydroxides represented by goethite and hydrogoethite predominate. Arsenates and sulfates are of subordinate importance. A sharp depletion of the ores in gold is observed.
c. Stage of formation of iron hydroxides. Sulfur has the greatest mobility; its stability coefficient is 0.2 (Table 2). Silicon remains immobile. A slight removal of iron is observed, although by the stability coefficient it belongs to the group of inert elements. A relative accumulation of gold, silver, and arsenic is established. Aluminum and magnesium possess slight mobility. In the material composition, a broad development of the process of dehydration of goethite and hydrogoethite is observed, as a result of which they pass into goethite and hematite. The formation of redeposited iron hydroxides with characteristic colloform structures is noted. Relatively coarse gold, up to 2.0 mm in size, occurs.
The most stable products of sulfide oxidation are limonites. With the development of oxidative processes, iron passes from the divalent form in sulfides into the trivalent form in the products of their oxidation. The relatively inert behavior of iron in the oxidation zone and the presence of two forms of its manifestation make it possible to recommend it
for determining the degree of oxidation of ores, which is calculated by the formula: $K = \dfrac{P}{1.43Q + P}$, where $K$ is the degree of oxidation of sulfides, %; $P$ is the amount of $\mathrm{Fe_2O_3}$, %; $Q$ is the amount of Fe bound with sulfides, %; 1.43 is the coefficient for converting iron bound with sulfides into oxidized iron.
Depending on the degree of oxidation, all ores may be subdivided into 3 groups: 1) ores with an oxidation degree of 80% and higher; 2) ores with an oxidation degree of 30–80%; 3) ores with an oxidation degree below 30%. Under near-surface conditions, to a depth of 20–30 m, and in individual cases to 50 m, ores with an oxidation degree of 80–100% are clearly distinguished. With increasing depth of occurrence to 150–200 m vertically, their degree of oxidation decreases to 80–50% and lower. However, in such ores, in zones of increased fracturing, areas with an elevated degree of oxidation are established (above 80%). As a result of uneven oxidation (where ore bodies are of considerable thickness), weakly oxidized ores (oxidation degree 30–50%) are interbedded with more highly oxidized ores (oxidation degree 50–80% and higher) (Fig. 1).
Ores with an oxidation degree of less than 30%, at the present level of exploration of the deposit, are observed as separate lenses and blocks within ores having an oxidation degree of 30–80%. In all probability, they occur at deeper horizons and have not yet been exposed by exploration workings (Fig. 1).
Study of the material composition of ores according to degree of oxidation revealed features of their mineral composition (Table 3). The amount of carbo-
Table 3
Mineral Composition of Ores
| Degree of oxidation, %, total | Degree of oxidation, %, average | Content, %, carbonates | Content, %, quartz | Content, %, clayey-micaceous minerals | Content, %, dark-colored and accessory minerals | Content, %, sulfides | Content, %, limonite, jarosite, scorodite | Content, %, gold liberated by oxidation of sulfides |
|---|---|---|---|---|---|---|---|---|
| 0–30 | 25 | 16,0 | 19,0 | 42,0 | 0,4 | 10,0 | 0,9 | 2 |
| 30–50 | 34 | 15,0 | 22,0 | 44,0 | 0,6 | 10,0 | 2,6 | 33 |
| 50–80 | 64 | 6,0 | 18,0 | 57,0 | 0,6 | 7,0 | 4,4 | 75 |
| 80–100 | 93 | 4,5 | 19,5 | 60,0 | 0,6 | 0,3 | 14,0 | 96 |
nates decreases with increasing degree of ore oxidation. The content of quartz and dark-colored minerals remains relatively constant. An accumulation of clayey-micaceous minerals is observed. The sharpest difference in the mineral composition of ores according to degree of oxidation is noted in the content of sulfides and the products of their oxidation. Thus, with an increase in the degree of oxidation of ores, the amount of sulfides changes from 10% in ores with an oxidation degree of 80–100%. At the same time, the amount of iron hydroxides, jarosites, and scorodites increases correspondingly from 0.9 to 14.0%.
As for the gold liberated during oxidation of sulfides, its contents in the ores are directly dependent on the degree of their oxidation, and the relative amount of liberated gold corresponds to the degree of oxidation of the sulfides (Table 3). This circumstance practically determines the technological properties of the ores. According to rational analysis data for ore samples with different degrees of oxidation, the con-
Fig. 1. Schematic cross-section of the deposit along profile No. XXXVI.
1, 2, 3, 4 — ores with degrees of oxidation, respectively, of 80–100%, 50–80%, 30–50%, and 0–30%; 5 — dikes of lamprophyres, kersantites, porphyrites, etc.; 6 — zones of fracturing and rock crushing; 7 — sandstones of the Upper Arkhar subformation; 8 — shales of the Lower Arkhar subformation; 9 — Cretaceous deposits; 10 — modern sediments.
Table 4
Technological indicators of ore processing as a function of oxidation degree
| Indicator / Sample no. | 2 technological | 4 | 5 | 14 | 17 | 6 | 10 | 15 | 1 | 16 | 11 | 8 | 2 | 7 | 12 | 13 | 3 | 9 | 4 technological | technological | 18 | 19 | 20 | 21 | 22 | 23 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Degree of oxidation, % | 98.5 | 98.5 | 98.5 | 98.2 | 98.0 | 97.5 | 97.0 | 97.0 | 97.0 | 95.0 | 92.5 | 91.7 | 91.0 | 81.0 | 64.5 | 63.5 | 53.0 | 32.2 | 20.0 | 30.0 | 60.0 | 29.0 | 43.0 | 27.0 | 30.0 | 20.0 |
| Percentage of unoxidized sulfides | 1.5 | 1.5 | 1.5 | 1.8 | 2.0 | 2.5 | 3.0 | 3.0 | 3.0 | 5.0 | 7.5 | 8.3 | 9.0 | 19.0 | 35.5 | 36.5 | 47.0 | 67.8 | 80.0 | 70.0 | 40.0 | 71.0 | 67.0 | 73.0 | 70.0 | 80.0 |
| Extraction of gold by cyanidation, % | 92.0 | 92.3 | 84.2 | 89.7 | 97.3 | 87.9 | 85.6 | 85.3 | 93.7 | 85.3 | 77.3 | 78.7 | 75.0 | 72.6 | 64.4 | 65.8 | 52.5 | 42.4 | 10.0 | 20.0 | 64.3 | 9.7 | 26.3 | 16.5 | 15.2 | 10.4 |
| Losses of gold in cake, % | 8.0 | 7.7 | 15.8 | 10.3 | 2.7 | 12.1 | 15.4 | 14.7 | 6.3 | 14.7 | 22.7 | 21.3 | 25.0 | 27.4 | 35.6 | 34.2 | 47.5 | 57.6 | 90.0 | 80.0 | 35.7 | 90.3 | 73.7 | 83.5 | 84.8 | 89.6 |
| Including: gold associated with sulfides and clay minerals, % | 2.0 | 3.8 | — | — | 0.5 | — | — | 5.9 | 0.3 | — | 13.6 | — | 3.6 | — | 6.9 | — | 2.0 | 4.6 | 9.1 | 6.7 | 0.7 | 2.1 | 1.1 | 1.5 | 2.3 | 5.7 |
| Gold associated with iron oxides, % | 0 | 0.6 | 8.0 | 2.6 | 1.1 | 3.0 | 6.7 | 2.9 | 1.0 | 5.9 | 1.1 | 1.4 | 10.8 | 13.0 | 4.0 | 16.0 | 5.7 | 6.4 | 3.4 | 2.0 | 6.4 | 12.8 | 18.9 | 10.9 | 3.4 | 2.9 |
| Gold associated with sulfides, % | 2.0 | 0 | 1.1 | 1.0 | 0 | 1.5 | 6.7 | 0 | 0 | 2.9 | 2.3 | 2.1 | 3.5 | 8.7 | 10.8 | 5.0 | 34.5 | 37.1 | 68.4 | 67.3 | 13.8 | 64.5 | 50.2 | 63.0 | 62.0 | 68.5 |
| Gold associated with quartz, % | 4.0 | 3.3 | 6.7 | 6.7 | 1.1 | 7.6 | 2.0 | 5.9 | 5.0 | 5.9 | 5.7 | 17.8 | 7.1 | 5.7 | 3.9 | 9.2 | 5.1 | 9.5 | 9.1 | 4.0 | 14.8 | 10.9 | 3.7 | 3.1 | 17.1 | 12.5 |
| Extraction of gold into flotation concentrate | — | 18.2 | — | — | — | — | — | — | — | — | — | 56.0 | — | 32.2 | 55.7 | 56.2 | — | 41.8 | 89.0 | 87.0 | 81.0 | 93.0 | 93.9 | 91.4 | 93.1 | 90.0 |
| Losses of gold in flotation tailings | — | 81.8 | — | — | — | — | — | — | — | — | — | 44.0 | — | 67.8 | 44.3 | 43.8 | — | 18.2 | 11.0 | 13.0 | 19.0 | 7.0 | 6.1 | 8.6 | 6.9 | 10.0 |
Note: gold extraction during cyanidation at an NaCN concentration of 0.1%.
Table 4 was compiled, from which the dependence of the technological properties of the ore on the degree of sulfide oxidation is evident.
On the basis of the results of rational analysis, the nature of gold losses with cyanidation tailings was revealed. Depending on the degree of oxidation of sulfides in the ore, different amounts of gold are lost with the cyanidation tailings. These losses are associated with a number of minerals and are divided into four groups (Table 5).
Table 5.
Gold losses with cyanidation tailings
| Degree of ore oxidation, % | Gold losses as % of the initial content due to scorodite and clay minerals | Gold losses as % of the initial content due to iron hydroxides | Gold losses as % of the initial content due to fine inclusions in quartz | Gold losses as % of the initial content due to unoxidized sulfides | Gold losses as % of the initial content, total |
|---|---|---|---|---|---|
| 0–30 | 4.1 | 6.9 | 10.3 | 65.6 | 87.4 |
| 30–50 | 2.9 | 6.4 | 6.1 | 43.6 | 59.0 |
| 50–80 | 3.2 | 5.7 | 5.9 | 17.5 | 32.3 |
| 80–100 | 4.2 | 4.5 | 6.0 | 2.6 | 17.3 |
Analysis of the data in the table makes it possible to draw the following conclusions:
-
The higher the degree of oxidation, the smaller the total losses of gold with cyanidation tailings.
-
Gold losses with scorodite decrease almost twofold as the degree of oxidation increases. At an ore oxidation degree of 80–100%, a slight increase in gold losses is observed, probably due to adsorption of the liberated gold by clay minerals.
-
With an increase in the degree of sulfide oxidation, gold begins to be liberated from its association with iron hydroxides; as a result, gold losses with them decrease noticeably.
-
The amount of gold lost in the form of fine inclusions in quartz changes insignificantly.
-
Gold losses with sulfides are inversely dependent on the degree of oxidation. The calculations carried out make it possible to express this dependence by the equation \(Y = 0.7x - 1.1\), where \(Y\) is the amount of gold associated with sulfides, %; \(x\) is the relative percentage of unoxidized sulfides.
Gold extraction into cyanide solutions is expressed by the equation (Fig. 2): \(y = 1.629x - 0.005x^2 - 22.9\), where \(y\) is gold extraction, %; \(x\) is the degree of ore oxidation, %;
The use of flotation established an inverse relationship between gold recovery and the degree of oxidation (Fig. 2). This relationship is expressed by the equation \(y = 95 + 0.2x - 0.01x^2\), where \(y\) is gold recovery into the flotation concentrate, %; \(x\) is the degree of oxidation, %.
The above-described changes in the technological properties of ores indicate that the effectiveness of applying one or another flowsheet is determined by the degree of oxidation. In this connection, it is necessary to determine the boundaries for assigning ores to oxidized, mixed, or sulfide ores. In determining the boundaries, the following provisions must be taken into account:
- Gold losses during processing according to the adopted flowsheet must be discardable.
Fig. 2. Graph of the dependence of gold recovery on the degree of oxidation of the ores.
1, 2 — curves characterizing gold recovery by cyanidation and flotation, respectively; 3 — curve characterizing overall gold recovery according to the flowsheet: flotation, cyanidation of the flotation concentrate after roasting; 4 — numbers of the technological samples studied; 5 — curve of gold recovery according to the combined flowsheet.
- Gold recovery must be sufficiently high.
- The processing flowsheet must be economically justified.
The technological indices, the character of ore oxidation in space, and the techno-economic calculation performed made it possible to distinguish 3 types of ores:
-
Oxidized. As the lower boundary of oxidized ores, a degree of oxidation of 85–90% is recommended; the average for the ores is 94%. Their processing may be carried out by cyanidation.
-
Mixed. As the boundaries of mixed ores, a degree of oxidation from 85–90% down to 30% is recommended. Processing may be carried out according to the combined flowsheet: cyanidation, flotation of gold-bearing sulfides, roasting of the concentrate, cyanidation of the calcines.
-
Sulfide. As the boundary of sulfide ores, a degree of oxidation below 30% is recommended. Processing may be carried out according to the flowsheet: flotation of gold-bearing sulfides, roasting of the concentrate, cyanidation of the calcines.
The recommended method for distinguishing industrial ore types may also be applied at other gold-ore deposits with a well-developed oxidation zone.
References
- Perelman A. I. Migration capacity of chemical elements in the weathering crust. In: The Weathering Crust, issue 4, Moscow, Publishing House of the Academy of Sciences of the USSR, 1956.