Genetic Types of Primary Gold Sources and Their Relationship to Placers in the Kuznetsk Alatau

B. N. Zimoglyadov (SNIIGGiMS)

Over the almost 150-year history of gold mining in the Kuznetsk Alatau, most placers have by now already been worked out, and the problem of searching for ore deposits has become quite urgent. To solve it, in addition to geological-metallogenic studies, it is necessary to make broader use of the available materials on placer gold content, since in nature there is a close spatial and genetic relationship between placers and their primary sources (as has been noted in the literature for other gold-bearing regions of the Union by E. Ya. Sinogina, L. V. Li, E. Z. Gorbunëv, and others).

The available materials on the gold content of the territory under consideration make it possible to say that a definite dependence is observed between the genetic types of primary sources, on the one hand, and the form, structure, productivity of placers, and their distance from these sources, on the other.

The known deposits and ore occurrences of gold in the Kuznetsk Alatau, through which industrial placers are formed, are represented mainly by the following genetic types. 1. Hydrothermal quartz-vein. 2. Sulfide-disseminated mineralization in zones of folding and schistosity. 3. Contact-metasomatic. 4. Gold-bearing conglomerates. The leading ones among these are the first two types of mineralization; the third type plays a somewhat lesser role, while among the conglomerates only the Cretaceous in the Kelbes district and the Lower Carboniferous and Upper Devonian deposits of the western margin of the Kuznetsk Alatau are of definite interest.

Hydrothermal vein deposits may be subdivided into two types: gold-quartz-sulfide and gold-quartz.

The gold-quartz-sulfide type of mineralization may be characterized by the example of the Berikul ore field (Timofeevsky, 1952; Bulyannikov, 1948; Beresnevich, 1912, and others). It is characterized by abundant sulfide mineralization, represented (in decreasing order) by pyrite, arsenopyrite, sphalerite, galena, chalcopyrite, pyrrhotite, and others. The bulk of the gold is represented by the 0.01–0.001 mm fraction, rarely 0.15 mm and larger, mostly associated with sulfides. In rich ores, nuggets up to 15 g and more were encountered. The form of the gold particles is varied. Among large gold particles, ob-

there is a predominance of irregular flattened forms; among the small ones—platy, film-like, dendritic, wire-like, droplet-like, and other forms. Its fineness is 400–600, and its color is pale yellow. The deposit is accompanied by a very poor, worked-out placer of the Sukhoi Berikul River (148 kg), whose productivity is tens of times lower than the productivity of its primary source, although in individual cases the gold content in it reached 2.5 g/m³ of sands. According to observations by Yu. P. Kazakevich, the beginning of the industrial placer is 0.5 km from the outcrops of the veins of the ore field on the sides of the valley. The form of the gold particles is relatively simple—scaly-platy, tabular, more rarely lump-like. In the assemblage of heavy minerals there are leached sulfides.

For relatively higher-temperature low-sulfide quartz-vein deposits, the presence is characteristic of a comparatively larger amount of pure, not sulfide-bound, coarser gold, sometimes macroscopically visible (up to 1–2 mm). Its fineness is about 800. Examples of this type of mineralization are the Burlevsko-Varvarinskaya, Khrebtovaya, and Dmitrievskaya groups of veins of the Central ore field (Timofeevsky, 1952; Bulyannikov, 1948, and others). Sulfide minerals in them are poorly developed and are represented by pyrite, sphalerite, galena; molybdenite occurs, scheelite is rare, and arsenopyrite is almost not characteristic. As a rule, these are small deposits with a sharply uneven, clustered distribution of gold, which creates certain difficulties in their mining; however, upon their destruction, comparatively rich industrial, well-sustained placers 3–5 km long are formed, the heads of which are practically not removed from their primary sources (placers of the Chirkovka, Burlevka, Shaltyr-Kozhukh rivers). The roundness of the gold is moderate; in the upper parts of the placers it is weak. The presence of nuggets and intergrowths with quartz is characteristic; the color is yellow to dark yellow. Gold coarser than 1.0 mm makes up about 70%. Fineness is 830–900. Characteristic is the presence in the heavy-mineral concentrates, along with gold, of the noted sulfide minerals. The productivity of this type of placer is many times higher than in the preceding case.

The sulfide-disseminated type of mineralization is characteristic of extended zones of crumpling and schistosity, in which gold-sulfide disseminations are developed either among schistose rocks or in small quartz and quartz-carbonate veinlets, stringers, lenses, etc. These zones by themselves have no practical significance, but ore occurrences and small gold deposits are found in them (Zabytoe, Kundatskoe, Pokrovskoe, Yurlovskoe, and others), and it is not excluded that industrial deposits may also be discovered in them. Subsequent river valleys with extended (8–15 km long) and relatively rich placers often develop along such zones (the Bol. Kundat, Talanovaya, and other rivers).

Gold in such placers has comparatively good, uniform roundness along their entire length and occurs as weakly rounded grains in intergrowths with quartz. The form of the gold particles is usually platy, scaly, rounded, more rarely lump-like; nuggets occur rarely. The fraction 1.115–0.345 mm makes up about 60%. Fineness is about 800.

For the contact-metasomatic skarn type of deposits, the presence is characteristic of comparatively coarse fractions of gold, often macroscopically visible and developed mainly in magnetite, garnet, wollastonite, tremolite coarse-crystalline skarns of drusy textures and least of all in massive epidote-pyroxene-amphibole varieties. The fineness is high—890–950. The form—

of the gold is varied: thin-plate, wire-like, lump-like, and octahedral. As a rule, these are small deposits with irregular, more rarely lens-like, ore bodies, which makes their exploration and exploitation difficult; however, the gold contents are sometimes fairly high, and when they are destroyed, rich, relatively short placers, 1–3 km long, are formed, directly adjoining their primary sources (the Lebedskoye, Sinyukhinskoye, Olginskoye, and other deposits).

The roundness of the gold in placers of this type is moderate to weak, especially in the upper parts; the color ranges from dark yellow to reddish yellow. The form of the gold particles is for the most part irregular and lump-like; intergrowths with magnetite, garnet, wollastonite, bornite, quartz, and calcite occur. The fineness is 900–950. The fraction coarser than 1.0 mm constitutes about 80% (the B. Kourchak, Sinyukha, and other rivers). In the heavy-mineral concentrates, along with gold, the above-mentioned minerals characteristic of this genetic type of deposit occur. The productivity of such placers is only several times lower than the productivity of their primary sources.

When gold-bearing conglomerates are destroyed, commercial placers are also formed, and virtually no spatial gap is observed between them (the Kelbess district, the N. Sueta River, and others). The gold in such placers is, as a rule, clean, well rounded, relatively fine, and sometimes in a “shirt.” The −0.5+0.1 mm fraction constitutes 45%. The fineness is high—870–930; the color is reddish yellow. Limonite and hematite occur in appreciable quantities in the heavy-mineral concentrates. Sometimes the gold-bearing conglomerates themselves were objects of working (the “Krasuli” of the Devonian deposits in the Kelbess district; Krasnopeeva, 1934).

Thus, owing to different genetic types of gold sources, placers are formed that differ in their form, structure, extent, distance from the source, and also in the morphology of the gold, its degree of roundness, fineness, grain size, assemblage of heavy-mineral indicator minerals, and so on.

It is necessary to dwell somewhat more fully on the relationship between the productivity of placers and that of their primary sources. This question, as Yu. G. Shcherbakov (1967) rightly noted, is still interpreted in different ways. There is an opinion that rich placers are formed at the expense of poor deposits, while poor placers accompany rich and large deposits. There are also opposite views. Examples can be found for each of these statements in various gold-bearing districts. For example, rich placers and poor deposits of the Lensky district, North America, and Martayga (the Talanovaya River, the B. Kundat River, and others); rich deposits and poor placers of Northern Kazakhstan and Martayga (the Sukh. Berikul River, and others); rich placers and rich deposits of the Chirkovka River and the Yubileino-Dmitrievka groups of veins of the Central ore field, and so forth.

It should be noted that there are not, and should not be, universal regularities in these relationships for different regions that are far removed from one another. Here the statement of F. N. Shakhov (1966) is quite correct: it is necessary to develop prospecting methods applicable to each district. The point is that the formation of placers is influenced mainly by climatic conditions, the history of relief formation, and the genetic types of their primary sources.

It therefore becomes clear that if the types of primary sources may be the same for different districts, the first two factors will in each case affect the process of placer formation differently. Hence the relationships between placers and

...with the primary sources will be different. For the conditions of the gold-bearing nature of the Kuznetsk Alatau, these interrelations will be expressed in the following way.

The bulk of the placers here is formed from gold of 0.5–1.5 mm size, which in its total mass averages about 90%. Fractions coarser than 1.5 mm and 0.3–0.5 mm usually make up to 10%, rarely more; the 0.1–0.3 mm fraction accounts for the first few percent, and the fraction smaller than 0.1 mm usually 0.03–0.04%. Therefore, the productivity of placers, all other conditions being equal, depends on the presence in ore deposits of coarse gold fractions (more than 0.3 mm) and on the ratio of free gold to gold bound with sulfides, which, in turn, depends on the genetic type of the deposits and on the conditions of their formation. The foregoing can be demonstrated quite convincingly by the example of the Tsentralninskii ore cluster.

The ore field of this cluster consists of several groups of veins (from north to south): Oktyabrskaya, Tsentralnaya, Yubileinaya, Khrebtovaya, Dmitrievskaya, Varvarinskaya, and Burlevskaya.

It is characteristic that in the structure of this ore cluster there is horizontal zonality, expressed in the fact that the two northern groups of veins (Oktyabrskaya and Tsentralnaya) are represented by a lower-temperature quartz–gold–sulfide type, with a large amount of sulfides (pyrite, arsenopyrite, less commonly galena, sphalerite, etc.). The gold occurs mainly in a state bound with sulfides and is represented by fractions of 0.05–0.001 mm. This group of veins is similar to the Berikul type of mineralization.

The southern groups are represented by a higher-temperature quartz-vein type with a small amount of sulfides (pyrite, galena, sphalerite, more rarely molybdenite and scheelite, rarely arsenopyrite). The gold here is represented by coarser fractions and is less bound with sulfides. The Yubileinaya group of veins occupies, as it were, an intermediate position. Accordingly, let us consider the productivity of the previously worked placers of this ore field. On the Alla-Kozhukh River, 1.1% was produced (Oktyabrskaya group); on the Taga-Kozhukh River, 5.7% (Tsentralninskaya group); on the Chirkovka River, 23.5% (Yubileinaya and Khrebtovo-Dmitrievskaya groups); on the Burlevka River and the upper reaches of the Shaltyr-Kozhukh River, 69.7% (Burlevsko-Varvarinskaya group).*

Here, too, the spatial interrelation of the placers with their primary sources is characteristic. According to observations by Yu. P. Kazakevich, along the Alla-Kozhukh River, from the beginning of the ore field and downstream over a stretch of up to 3 km, there is no industrial concentration of gold, although the geomorphological setting is favorable for the formation of a placer and the valley has been well prospected. Along the Taga-Kozhukh River, within the limits of the outcrop of the veins of the Tsentralninskaya group, there is no commercial placer; it begins 0.3 km lower. These same facts were noted earlier by M. A. Zheromskii and G. L. Pospelov. Along the Chirkovka and Burlevka rivers and in the upper reaches of the Shaltyr-Kozhukh River, no spatial break is observed between the placers and their primary sources.

Consequently, the most productive placers in the Tsentralnoye ore field were formed from the higher-temperature groups of quartz–gold-ore veins, and they have the closest spatial connection with their primary sources.

Thus, the preliminary study carried out of the interrelation of placers with their primary sources under the gold-bearing conditions of the Kuznetsk Alatau shows that, owing to different types of depo-

* The total production for the indicated streams of the Tsentralninskii cluster has been taken as 100%.

deposits, placers differing in form, productivity, morphology of the gold, its fineness, grain size, roundness, and assemblage of heavy-mineral accessory minerals are formed, at varying distances from the sources. This question requires further, more in-depth study, since its solution in specific cases will make it possible, from the character of the placers, to determine the types and assess the industrial value of their primary sources, and also to direct prospecting and exploration work more purposefully. For this it is necessary to carry out special studies of the morphology of placer gold, its grain size, trace elements, accessory minerals, intergrowths with other minerals, fineness, etc. At present several such areas are known where there are comparatively short and rich worked placers, whose productivity was more than 500 kg/km, but whose primary sources have not been identified. These include:

1. The headwaters of the Kundustuyul River, above the Verkh. Voskresenovka River.
2. The heads of the Petrovsky and Kompaneisky creeks, right tributaries of the Bolshoi Tuluul River.
3. A segment of the left terrace of the Elansky level of the Talanovaya River, in the area of the settlements of B. and M. Semenovka.
4. The headwaters of the Ust-Podarenny Creek, a tributary of the Talanovaya River.
5. The watershed of the Mal. Pokrovka River, a tributary of the Bol. Tuluul River, and the Nikolki River (Bogatyr Creek), a right tributary of the Kiya River.
6. The head of the Aleksandrovsky Brook, a left tributary of the Poludenny Kundat River.
7. The headwaters of the Voskresenka River with Aleksandrovsky Creek; right tributary of the Kundat River.
8. The headwaters of the Petropavlovka River, a right tributary of the Bazas River.
9. The headwaters of the M. Taz River, a right tributary of the Bol. Taz River.

The identified primary sources of placers in the areas indicated above may prove to be industrial gold-ore objects.

REFERENCES

1. Beresnevich I. P. Report on the statistical-economic and technical study of the gold-mining industry of the Tomsk Mining District, vol. 1, St. Petersburg, 1912.
2. Beresnevich I. P. Gold-ore formations and gold-bearing provinces of the Altai-Sayan mountain system. Tomsk, 1948.
3. Gorbunov E. Z. Regularities in the distribution of gold in alluvial placers and their practical significance in prospecting (on the example of the Northeast of the USSR). Geology of Placers. “Nauka,” 1965.
4. Krasnopeeva P. S. The Kelbes gold-bearing district. Materials on the Geology of the West Siberian Territory, issue 16, 1934.
5. Li L. V. Anthropogenic gold placers of the basin of the right bank of the Upper Kolyma, regularities of their distribution and conditions of formation. Geology of Placers. “Nauka,” 1965.
6. Sinyugina E. Ya. On the question of the connection of alluvial placers with primary sources (on the example of the South Yenisei district). Geology of Placers, “Nauka,” 1965.
7. Timofeevsky D. A. The Tsentralnoye gold-ore deposit. Geology of the Principal Gold-Ore Deposits of the USSR, vol. V, NIGRIzoloto, 1952.
8. Timofeevsky D. A., Shcheglov P. I., Borishanskaya S. S. The Berikul gold-ore deposit. Geology of the Principal Gold-Ore Deposits of the USSR, vol. V, NIGRIzoloto, 1952.
9. Shcherbakov Yu. G. Distribution and conditions of concentration of gold in ore provinces. “Nauka,” 1967.