Iron Ore Deposits of the Khakass-Minusinsk Region*)

Academician M. A. Usov

I. Introduction

During the First Five-Year Plan and at the beginning of the Second Five-Year Plan for the development of the national economy of the USSR, major geological-prospecting work was carried out in the Khakass-Minusinsk region, performed almost exclusively by the West Siberian Geological Prospecting Administration (now the Geological Trust), chiefly through the Minusinsk base of the administration. These works were deployed to solve two principal tasks: to identify and define more precisely the region’s mineral raw-material resources in connection with copper and ferrous metallurgy, and also to provide a reserve base for the Kuznetsk Metallurgical Plant. Kuznetskstroy partially financed these investigations.

Thus, the geological-prospecting works conducted in the Khakass-Minusinsk region covered all known points of iron-ore deposits and revealed a whole series of new iron-ore deposits. They were of a comprehensive character, expressed in geological-prospecting and magnetometric surveys, in prospecting and exploration investigations, and in prospective exploration using core drilling, as well as in expert work of a heavy type at the most interesting deposits.

The geological-prospecting and magnetometric survey covered the most accessible parts of the mountain regions surrounding the Minusinsk Basin. Therefore it cannot be asserted that all the region’s potential possibilities with respect to iron-ore reserves have been revealed. Moreover, many of the discovered ore points have not been subjected to more detailed investigations. However, it may be thought that all the principal types of iron-ore deposits of the region have been established by the investigations carried out, and almost all the results of the investigations have already been published, at least in the form of preliminary reports. A summary of these results is given in volume 1 of the collection Mineral Resources of the West Siberian Region, issued by the Geological Trust in 1934 (18). Nevertheless, the present essay contains a number of new data, chiefly of a theoretical character, since during the past three years the study of the geology of Western Siberia has made significant progress, illuminating the geological conditions and the Khakass-Minusinsk iron-ore deposits; in addition, more detailed processing of materials from certain explored deposits has continued throughout this time.

The chief achievements in the understanding of the geology of Western Siberia consist in the fact that, by means of a proper subdivision of the strata of mountain rocks into

*) The present work by Acad. M. A. Usov was written in 1937–38 and, in respect of numerical data, cannot at the present moment be considered entirely exact. Questions of stratigraphy have also been subjected to further clarification. Thus, for example, the formation of ferruginous quartzites of the Western Sayan, assigned in this work to \(S_1^a\), most probably has a Proterozoic age (Editors).

formations, with the identification of the corresponding phases of tectogenesis, it has been possible to establish the age of the principal groups of mineral formations, i.e., to establish the specific geochemical epochs of the country, and at the same time to show that, in fact, each epoch was characterized by its own complex of rocks and associated useful minerals (16). Table 1 lists all the formations established to date in Western Siberia in which appreciable accumulations of iron-ore minerals occur.

Table 1.

Iron-ore formations of Western Siberia.

Of these formations, quartz porphyries of Lower Mesozoic and Middle Cambrian age, with their sulfide deposits, have not yet been found in the Khakass-Minusinsk region. Furthermore, the outlines of the magnetite deposits genetically connected with Lower Carboniferous granodiorites are very unclear; the presence of such deposits in this region has only recently begun to be suggested. Moreover, even in the Altai, where Lower Carboniferous granodiorites are widespread and have already been studied rather well, no serious magnetite deposits of this age have been found. Finally, the complex hematite ores of Upper Silurian age, of presumably telemagmatic origin, are as yet unknown; up to now they are known only in Salair, where their reserves are also insignificant. From the survey of iron-ore deposits we may exclude the spherosiderites of the coal-bearing deposits of the Minusinsk Basin, since these ore formations have not been subjected here to special investigations.

The following survey of explored iron-ore deposits of the Khakass-Minusinsk region is made by groups or by individual deposits, depending on their importance, in stratigraphic order from bottom to top. The survey will include ore occurrences both of the Minusinsk depression and of the slopes of the mountainous areas that border it.

II. THE CHEBAKOVSKAYA GROUP OF GOLD-IRON-ORE DEPOSITS

The most ancient age belongs to complex iron-ore deposits genetically connected with the intrusion of quartz monzonites, which everywhere occur only in the Upper Algonkian formations and entered the pebbles of the Lower Cambrian conglomerates, as was established by the detailed investigations of K. V. Radugin in Gornaya Shoria (12). The rocks of the intrusion crop out

mainly in the NE part of the Kuznetsk Alatau, where they were studied in connection with the extraction of gold belonging to the suite of minerals of this formation. Especially notable are the gold–iron-ore deposits of the Chebaki district, which yielded a large quantity of gold. In 1931, magnetometric investigations were carried out at the Kaliostrov and Spassk deposits of the group in order to establish the magnetite reserves contained in them (18, 64 and 14, 49).

The intrusion has a complex composition. In the first phase, gabbro-diorites and quartz-augite diorites were formed. They compose coarsely crystalline bodies in the schists, having the form of small acmoliths and dikes. Under the influence of subsequent hydrotherms, which readily spread along these bodies, the rocks underwent considerable greenschist alteration, having the character of epidiorites.

In the following phase, a more acidic magma rose, giving rise to a comparatively small number of rather large bodies of granitoid rocks belonging to the quartz monzonites. The dark-colored components of these rocks for the most part passed into actinolite and chlorite, but, in comparison with the diorites, the monzonites have been preserved rather well.

Subsequent postmagmatic emanations were abundant, producing considerable alteration both of the intrusives and of the rocks of the continent. Among the secondary minerals, epidote, actinolite, chlorite, quartz, calcite, and sulfides predominate, in particular pyrrhotite. In places, typical skarns with garnet were formed, more readily associated with limestones, but sometimes also produced at the expense of replacement of porphyrites. It should be noted that, for example, in the Kaliostrov deposit the skarns occur in contact with diorite, whereas in the Spassk goltsy they compose vein-like masses among porphyrites, at a considerable distance from the intrusives. Thus, here we are once again convinced of the proposition, which is beginning to become ever more widespread, that the so-called contact-metamorphic or metasomatic deposits were formed at the expense of emanations coming from a deep magmatic source after the emplacement of the visible magmatic bodies (14). If such metasomatic deposits are very often found in contacts with intrusive bodies, this is only because at the boundary between heterogeneous masses, seams in the expansion phase open more readily, and along these paths the differentiated solutions rise.

Skarns, sometimes magnetite-bearing, and more or less massive magnetite deposits belong to the first, comparatively high-temperature formations. Almost everywhere they underwent brecciation by lower-temperature minerals, especially quartz and sulfides. Thus the magnetite ores of the district—although according to the few available incomplete analyses—contain on average about 45% iron, being contaminated by such harmful impurities as silica and sulfur compounds.

In general, for this formation the gold mineralization is more typical, in the form of quartz-sulfide veins and disseminations; among the sulfides, bismuth glance is especially characteristic, which is not encountered in other gold-ore formations of the region. It is interesting that the industrial gold deposits are associated mainly with bodies of epidiorites. Such, for example, are the Kommunar deposit, represented by a complex rich vein, and the Podlunnoe deposit, which is actually an ore-bearing epidiorite with very large gold reserves. Apparently, the diorite bodies cracked especially readily before the rise of the corresponding hydrotherms, in connection with which they experienced strong mineralization (5,55).

Quartz-sulfide solutions readily penetrated both the skarn and the magnetite deposits, which are intersected by a fine network of quartz veins.

veinlets, are directly impregnated with quartz and sulfides. In particular, the Kaliostrovskoye deposit, though a small iron-ore deposit, proved to be very rich in gold ore.

The reserves of iron ores in the deposits of the group are insignificant. The ore has a complex composition and requires beneficiation. Evidently, the ores of the region will be used primarily for gold—especially since the region is of a high-mountain character.

III. THE MAINA GROUP OF SULFIDE DEPOSITS

Small magnetite deposits are genetically connected also with an intrusion of trondhjemites of Middle Cambrian age, which actually produced the sulfide mineralization. This mineralization was studied during exploration of the Maina deposit, located on the left side of the Yenisei River, 7 km upstream from its exit from the Western Sayan; but several other ore occurrences are known within the limits of the development of the corresponding formation, for which reason one may speak of the Maina group of deposits.

The Maina deposit was explored over the course of several years, up to and including 1933; it was described in considerable detail by M. E. Nekipelov (9). However, the age of the formation was established only during the geological-prospecting survey of the Tabat sheet, carried out in 1934 by O. K. Poletaeva and I. E. Shatrov (11). Here they were able to show that the sedimentary-effusive sequence with trondhjemites had been dislocated and denuded before the deposition of the Arbat suite, which begins with basal conglomerates with pebbles from the rocks of the underlying formation. On the other hand, the Arbat suite is overlain by the West Sayan formation with hyperbasites, which contains limestones with trilobites of an age approximately corresponding to the middle of the Middle Cambrian. After this, by correlation with the corresponding formations of Salair, it was possible to show that the sedimentary-effusive formation with trondhjemites belongs to the lower part of the Middle Cambrian (16, 72).

The Maina deposit studied lies among porphyries of the greenstone facies and consists of several ore zones, most of them revealed by geophysical surveying. Only the main ore zone has been explored; it has been traced along strike for 450 m. According to core-drilling data, it probably pinches out at a depth of 250 m; moreover, the ores are oxidized and largely leached down to a depth of approximately 100 m, since the deposit is confined to the summit of a mountain having an absolute elevation of 634 m.

The main ore zone consists of lenses of massive sulfides and, in places, magnetite, alternating with a more or less dense dissemination of sulfides, as well as with porphyries that have undergone considerable metasomatism, with predominant development of chlorite, and recently have been transformed into chlorite schists. If the comparatively insignificant magnetite-bearing sections are disregarded, the total thickness of the sulfide ores varies within the zone almost from 0 to 44.1 m, with a prevailing average thickness of 7 m.

The ore bodies consist essentially of pyrite, which, with a small amount of magnetite, was deposited among other ore minerals. After some compression, emanations penetrated, introducing chalcopyrite and sphalerite; the commercial ores contain copper from 0.31 to 2.10% and zinc from 0.77 to 0.94%. The iron content in the commercial ores ranges from 30.40 to 36.34%, sulfur from 28.96 to 33.85%, and silica from 11.53 to 20.40%.

Evidently, this deposit, like the entire group, is significant only for sulfuric-acid production, as well as for nonferrous metallurgy.

However, the iron slags that will be obtained in this process may also be used in ferrous metallurgy.

The Maina deposit is interesting genetically. As was established as early as 1924 by I. K. Bazhenov (1), the paragenesis of the minerals of the ore zone is in places very close to normal skarns, which were usually regarded as contact-metamorphic formations produced from limestones at their contact with intrusive rocks. But here there is no direct contact of the ore zones with the intrusive body, and the ore bodies occur in altered porphyrites. Then, using the example of the Maina deposit, I began to develop the idea of the metasomatic origin of skarns and of the ore deposits associated with them, irrespective of the composition of the rocks being replaced. This idea found full confirmation in the subsequent study of the iron ores of the Telbes district, which belong to the contact-metasomatic type and at the same time in places are entirely unrelated to the contact zone of intrusions (13).

I am now convinced that the form of manifestation and the composition of emanation deposits depend on two principal factors: first, on the composition of the parent magma, and second, on the time of manifestation of the phases of contraction and expansion in the given magmatic cycle. Complex ores, of course, can form only in a hypabyssal setting.

IV. THE TUIM-KARYSH GROUP OF COMPLEX-ORE DEPOSITS

Accumulations of magnetite, this time of industrial significance, are also associated with the Upper Cambrian granosyenite intrusion, which is well represented on the eastern slope of the Kuznetsk Alatau, where it has been well studied, since the mineralization accompanying this intrusion is complex, being characterized by the presence of copper and rare heavy metals. It must be said that there is no precise proof of an Upper Cambrian age for the granosyenite intrusion, for everywhere it cuts only the Algonkian and the Lower and Middle Cambrian. An opinion has even been expressed that the intrusion is Silurian in age. However, in the Lower Silurian conglomerates studied by K. V. Radugin in Gornaya Shoria (12), the pebbles consist in part of the intrusions under consideration.

I think that such an occurrence of the granosyenite intrusions is due to powerful denudation in the second half of the Upper Cambrian, when Western Siberia was land that had completed the Salairian cycle of tectogenesis. The same relationship is characteristic of the Variscan granitic intrusions of the Sayan-Altai region: they usually occur among Silurian formations, although in a few places where Upper Paleozoic deposits have been preserved, the latter are cut by these intrusive rocks (16, 197).

Notable accumulations of magnetite in the skarns of the contact belt of the intrusion have been found in some deposits of the Tuim-Karysh group, located in the area of Son station on the Achinsk-Minusinsk railway. Here, in recent years, a geological prospecting survey at a scale of 1:100,000 has been carried out, refined at the deposit sites at scales of 1:25,000 and 1:10,000 by the West Siberian Branch of the Redmetrazvedka. The same survey has been carried out in the Ulen and Kamyshta groups, and everywhere approximately the same picture has been revealed.

Thus, according to the as yet unpublished data of I. S. Tseiklin and G. L. Pospelov, the granosyenite intrusion was emplaced mainly along the horizon between the Algonkian and the Lower Cambrian, being very complex. As a result of mutual intersection of rocks of different phases, a variegated picture of intrusive tectonics was produced. The first phase of the intrusion yielded diorites, which before the following phase in places underwent brecciation. Such

the fractured zones were then subjected to clear hornfelsing through the fine dissemination of biotite and amphibole. The main phase of the intrusion is represented by granosyenites, usually having the composition of quartz mangerites.

The intrusion of the mangerites was accompanied by very sharp contact metamorphism: such vivid hornfelses, rich in biotite and amphibole, did not form during the other magmatic cycles of the region. Pegmatites were emplaced into the rocks that had already been hornfelsed. Then abundant emanation streams followed, producing a whole series of skarns and ore bodies; these formations are usually located in the contact belt of the intrusions, but sometimes also far from it, and in part within the intrusion itself. The period of skarn formation was also complex: at least three phases can be distinguished in it.

The first phase of skarn formation includes pyroxenes, garnets, magnetite, and scapolite, listed in the order of their deposition. The second phase, preceded by brecciation of the earlier formations, is characterized by muscovite, quartz, epidote, prehnite, actinolite, and scheelite. Finally, the third phase includes sericite, quartz, calcite, chlorite, serpentine, and tremolite, as well as a number of sulfides: molybdenite, pyrrhotite, pyrite, chalcopyrite, and others. These are the most widespread minerals of the mangerite emanations; locally, minerals such as vesuvianites also occur.

In connection with such a complex composition of the granosyenite intrusion, there is also a diversity of useful minerals associated with it, namely: asbestos, dolomite, and ores of copper, tungsten, molybdenum, iron, and gold. Of these, in recent times the ores of rare heavy metals have attracted the greatest interest, before which copper has receded into the background. As for the magnetite ores, they do not form especially large accumulations.

Among the deposits of the group containing magnetite, Kiyalykh-uzen has been well studied; it is located 6 km from the Tuim junction of the Achinsk–Minusinsk railway line. Heavy-type exploration was carried out there, first for copper, and more recently essentially because of molybdenum. One of the methods used for delineating the ore bodies was a magnetometric survey. According to the report by D. D. Staroverov on the work of 1934–35, the composition and structure of the deposit may be briefly presented as follows.

The deposit is confined to a mountain that represents a remnant of an ancient sedimentary-metamorphic sequence submerged in a granosyenite massif. The base of this remnant consists of marbled limestones. They form an anticlinal fold, closing in the north, with a steeply dipping axis, and overturned to the east. The eastern overturned limb has still preserved an overlying sedimentary-pyrogenic metamorphosed suite.

The folded structure of this remnant of the ancient sequence is emphasized by numerous sills and small laccoliths of at least two ages. These include, first, gabbro- and diorite porphyries, which, together with the enclosing sequence, underwent intense metamorphism. It must be thought that this is an intrusion of the Scandinavian phase of tectogenesis, which took place at the end of the Algonkian (16, 61). Second, numerous dikes are composed of aplite-pegmatites and granite porphyries of the granosyenite cycle of intrusion. The structure of the sequence is also emphasized by various metasomatic formations associated with the granosyenite intrusion, including ore bodies.

All Algonkian and Lower Paleozoic formations are cut by numerous dikes of diabase porphyrites, oriented in the NW–SE direction, so characteristic of the Abramov phase of tectogenesis of the Middle Devonian (16, 132).

As a result of contact metamorphism from the granosyenite magma,

limestones were transformed into marbles, and the siliceous rocks associated with them into quartzites, whereas the silicate rocks passed into amphibole and biotite hornfelses. As for the deep emanation streams, they passed selectively along structural lines and produced various skarns, formed not only at the expense of marbles but also at the expense of silicate rocks, including granosyenite. Garnet, diopside-garnet, hedenbergite-magnetite skarns and diopsidized marbles are distinguished.

It is not without interest to dwell on the composition of the skarnized granosyenites. Megascopically these are medium-grained pink rocks, penetrated by quartz and garnet. Under the microscope it is seen that of the original composition of the rock only irregular grains of sericitized and epidotized feldspars have been preserved, immersed in an allotriomorphic aggregate of epidote, zoisite, calcite, and quartz, with clump-like accumulations of brown garnet. Characteristic is the presence of a considerable amount of secondary sphene, as well as sulfides.

The ore bodies, having vein- and lens-like forms, occur according to the structure of the sedimentary-metamorphic block. They are quite numerous within the body of marbles, where they are confined to interbeds and sills of silicate rocks. But the main ore zone follows the contact between the limestone and silicate series; and since in the N. and NW. parts of the block the silicate series is absent, having been broken off along this junction by a steep fracture, here the ore zone is confined to the contact between the granosyenites and the marbles. Thus, in the Kiyalykh-uzen deposit the structural origin of the “contact”—metasomatic ore zones is excellently revealed.

The indicated ore zone is divided into three parts. The western part has been traced at the surface for 120 m; its thickness ranges from 0.8 to 4.6 m, with an average thickness of 2 m. The middle part, corresponding to the closure of the fold, is about 116 m long. Its thickness varies at the surface from 6 to 30 m, and at a depth of 200 m, according to core-drilling data, in the middle part of the body reaches even 80 m. The eastern part of the zone, located along the junction between marbles and hornfelses, has been traced along strike for 322 m, and its thickness ranges from 2 to 32 m, averaging 13 m.

The ore deposit has an irregularly banded structure, consisting of bands and stringers of various skarns, hornfelses, amphibolites, and marbles. In general the composition of the ores is very variegated. To characterize the chemical composition of the ore, we shall give the results of a chemical analysis (in percent) of a section of core from borehole No. 1, 7.06 m long, from a depth of 180 m, represented by magnetite skarn.

Barium, lead, selenium, tellurium, antimony, tin, and tungsten—absent.

Let us also note that in the ores of the deposit there are only traces of gold and up to 20 g/t of silver. It is characteristic that tungsten has not been found here, whereas in neighboring deposits of the group, having the same age,

tungsten ores became the chief object of industrial exploration. The ore minerals are represented, in order of abundance, by magnetite, pyrite, molybdenite, sphalerite, pyrrhotite, and chalcopyrite, with arsenopyrite and tennantite present in small amounts.

Magnetite is an almost constant component of skarn ores, but pure accumulations of it are encountered very rarely. What, by outward appearance, may be called iron ore contains from 15 to 60% iron, with an average content of 29%. In garnet-magnetite skarns the iron content averages 19%, while in ore-bearing hornfelses and amphibolites it is only 5%.

Thus, from the industrial point of view, Kiyalykh-Uzen is not an iron-ore deposit, although in the oxidation zone, which extends to a depth of only 5 m and is almost freed of sulfides, individual parts of the ore body are precisely iron-ore in character.

The Spirinskoye deposit, located 7 km from the Achinsk–Minusinsk railway line, may perhaps be of greater significance as an iron-ore occurrence. In 1932 a magnetometric survey was carried out there. It must be said that the ore in the outcrops is strongly limonitized. This indicates the sulfurous composition of the primary ores of the deposit, which may be similar to the ores of Kiyalykh-Uzen. Consequently, the industrial significance of the Spirin ores has not yet been established, since they have not been sampled and have not been subjected to experimental beneficiation.

V. THE IRDZHINSKOYE MAGNETITE DEPOSIT

In the history of the organization of Siberian ferrous metallurgy this deposit played a noticeable role. Specifically, in 1925, when the question of building a metallurgical plant in the Siberian Region was raised in Sibrevkom, there were two approaches to resolving this question: some considered it necessary to restore Kopikuz’s project and organize the Kuznetsk plant on the iron ores of the Telbes region and the coals of Kuzbass; others, taking into account the small size of the iron-ore reserves identified by Kopikuz in the Telbes region, proposed turning to the Minusinsk basin, where, according to the available data, the iron-ore reserves were more considerable, and in particular pointed to the Irdzhinskaya group of deposits, which lies on the right side of the Yenisei River, opposite the well-known Bateny landing stage, and is fully accessible to water transport. As is known, the question was decided in favor of the Kuznetsk plant; in 1926 Telbesbyuro was organized for the preparation of materials, and in 1929 construction of the Kuznetsk plant was already begun, which now operates at full capacity, being the pride of the ferrous metallurgy of the USSR.

At the same time, the Irdzhinsky district was covered by geological-exploration work of the First Five-Year Plan, which showed that this group of deposits has no industrial significance under present conditions. In view of this, the materials collected during the indicated exploration work were not subjected to detailed processing, and only recently, in studying these materials, did it become clear that the basis of the structure of the Irdzhinskaya group is formed by effusives of Middle Cambrian age. They are, it is true, rather strongly altered and fractured, but previously it was supposed that this was the result of ore metamorphism and that the effusives were Devonian in age, like those rocks that are exposed on the steep right bank of the Yenisei River.

The pyrogenic sequence is cut by a complex intrusion, which includes both diorites and granosyenites. It is characteristic that the contact metamorphism caused by the intrusion is very strong and distinctive: even in the effusives there appears a large quantity of biotite and amphibole sheaves, in

in prospecting workings—though they have suffered severely from weathering. In short, we have before us a fairly typical picture of an Upper Cambrian granosyenite intrusion.

Already after the formation of the intrusion and its contact aureole, as also in the Tuim-Karysh group described above, emanational derivatives of deep-seated magma appeared from the depths; having passed along fissure paths in the effusives, they produced skarn formations, as well as magnetite deposits.

The country was denuded approximately down to the present surface, possibly with the formation of a considerable weathering crust, when powerful subaerial volcanism appeared, producing extensive covers of acid rocks with dikes of labradorite porphyrites. Now, when the Middle Paleozoic continental formations of the West Siberian region have been rather well distinguished (16), it must be thought that the Irdzhin effusives are not of one age: in all probability the acid rocks belong to the Upper Silurian, whereas the labradorite porphyrites are undoubtedly Middle Devonian.

On Irdzhin Mountain with its ore deposits, denudation has already removed the effusive cover, and the Cambrian is cut by a rather dense network of felsite dikes which, in accordance with their facies, are rather strongly autometasomatized, chiefly ocherized. But in places there have been preserved patches of both dike and blanket felsites, which, given the poor exposure of the area, would readily be taken for dike formations if these felsites were not distinguished by their relative freshness. It is interesting to note that the felsite dikes tend not to cut ore and skarn bodies, as comparatively resistant formations.

Exploration of the Irdzhin deposit was carried out at a time when its age was unknown, and when the geochemistry of the Upper Cambrian granosyenite intrusion of Western Siberia was also unknown. Therefore the deposit in the oxidation zone, with which the prospecting workings were associated, seemed, like Kiyalykh-Uzen, to be specifically an iron-ore deposit, although it may probably be significant as a deposit of rare-metal ores.

VI. THE PATYN DEPOSIT OF TITANOMAGNETITE ORES

On the boundary between Khakassia and Mountain Shoria, deep within the Kuznetsk Alatau, lies the prominent Mount Patyn, whose highest point reaches an absolute elevation of 1617 m and which represents an exhumed lopolith of banded gabbro-norites, ore-bearing in separate bands. This lopolith has an area of about 40 sq. km, being the largest body of basic rocks known in Western Siberia. It occurs among Algonkian marbelized limestones and microquartzites, but its age is considerably younger. Thus, in the Amyl district of the Western Sayan, similar banded gabbro-norites, though still poorly studied, occur among the Lower Silurian West Altai formation; and according to other data it may be supposed that they are Ardennian in age (16).

The lopolith consists of large, as it were stratified, zones of rocks of differing composition. Since the rocks of these zones alternate without any particular differentiational order, they must be recognized as the result of successive intrusions, so that the lopolith has a complex structure. The zones, in turn, are more or less finely banded, which already represents the result of differentiation in situ of the gabbro-norite magma, generally prone to such a manifestation of differentiation. In general the whole massif appears thinly layered, and the layering, corresponding to the form of the lopolith, forms one broad synclinal fold, closing on the NE side, with the limbs dipping no more than 35°.

The principal rocks of the lopolith are, in general, rich in titaniferous magnetite. In certain zones the amount of this ore admixture increases so much that it becomes an essential component of the rock, which thereby acquires the character of an ore. Such ore gabbros make up four zones 50–70 m thick, as established by the two-year prospecting work conducted by I. P. Komarov (6, 3.53). The reserves of mineralized rocks here are therefore colossal.

Among individual belts of ore gabbros there occur comparatively small beds of ore pyroxenites, in which apatite is present, with a phosphoric anhydride content of up to 3%.

The lopolith is cut in several places by small stocks and dikes of alkaline rocks, represented by alkaline granites, nepheline syenites, and peculiar pseudo-wollastonite nephelinites—patynites. This is the latest and somewhat isolated phase of the same cycle of volcanism, for intrusions of Ardennian age everywhere within Western Siberia are distinguished by such a complex character, having a gabbro-syenite composition.

With the exception of a few rare samples, the ore gabbros and pyroxenites are very poor ores. Indeed, the average iron content in them ranges from 15 to 20%, with 10–12% titanium oxide and 0.3% vanadic anhydride. Therefore at present these are not ores. But in the future, after a railway is built through the Kuznetsk Alatau and after this high-mountain region has been developed, it will be possible to raise the question of the comprehensive utilization of the Patyn titanium-magnetite ores, which will require the application of rather complex mechanical beneficiation.

VII. FERRUGINOUS QUARTZITES OF THE SAYANS

The Algonkian and Cambrian deposits considered up to now, as well as the most important Devonian iron-ore deposits described below, are genetically connected with intrusions and have a contact-metasomatic character. Only in the very lowest parts of the Ordovician, chiefly in the Western Sayan, have iron-ore formations of bedded type been encountered, represented by ferruginous quartzites. Since in world practice sedimentary iron ores are of special importance, much attention was paid to these formations, and in 1929–30, in the Western Sayan, under the general direction of I. K. Bazhenov, substantial prospecting and exploration work was carried out, which established that the ferruginous quartzites have no industrial value. Their general characterization is given according to the report of I. K. Bazhenov (2), with minor corrections concerning stratigraphic relations, in accordance with the latest geological investigations.

The Western Sayan, to the southwest of the Yenisei River, is a broad synclinorium consisting of Cambrian and Lower Silurian rocks, which are represented by several independent formations that underwent tectogenesis separately and were folded together into the indicated synclinorium during the West Altai phase of tectogenesis (16). The southwestern limb of the synclinorium is complicated by a fairly large anticlinal fold, owing to which the lower horizons of the Lower Silurian in general form three more or less parallel belts.

The ferruginous quartzites are confined to the Lower Silurian metamorphic formation. It consists essentially of sandy-clayey rocks that were formed through the erosion of Cambrian effusives; however, it also contains its own effusives, chiefly in the sill facies, strongly altered and in this case difficult to distinguish from sandstones.

The question of the metamorphism of the sequence is very interesting. Earlier, when the Lower Paleozoic of the Western Sayan had not been subdivided into independent formations, it seemed that the metamorphism was caused by intrusions of hyperbasites, as well as granites. But now it has become clear that the hyperbasites are older than the Lower Silurian sequence (17). As for the granites, being considerably younger than it, they nevertheless could not have caused the metamorphism of the entire sequence, since the contact metamorphism caused by them occupies a narrow belt and has a hornfels character, whereas the sequence is permeated with actinolite, epidote, chlorite, sericite, quartz, calcite, and pyrite. And it must be said that in all the mountainous regions of Western Siberia it has approximately one and the same appearance.

Thus, the Lower Silurian sequence, usually called green-violet, was metasomatized by emanations that are connected with the volcanism of the epoch of its tectogenesis (15). The peculiarity of this volcanism consisted in the fact that, owing to a special distribution of the phases of compression and extension, only small portions of magma rose to the presently visible horizon of the earth’s crust, producing the occasionally encountered dikes of quartz albitophyres, and abundant gas–water emanations.

Of the three indicated belts of ferruginous quartzites situated in the lower part of the formation, detailed exploration was carried out on the northern, or Dzhoi, belt, extending in the upper reaches of the left tributaries of the Dzhoi River. The layers of this belt impregnated with iron glance have a thickness from 0.35 to 3.4 m and are very inconstant, pinching out and reappearing, which must be explained by intensive bedding-plane movements that took place both before metasomatism and in the later phases of tectogenesis. In this belt the ore layers, in mineralogical composition, differ little from ordinary chlorite schists, consisting of quartz, albite, epidote, chlorite, sericite, calcite, and other hydrothermal minerals in various combinations, only with some concentration of iron glance and, at times, magnetite.

But in other belts, distinct banded ferruginous quartzites were also recorded, with thin bands of a bridge-like structure of quartz and predominantly iron glance, with a comparatively small quantity of other components. Here it is also evident that, besides primary quartz, much quartz introduced by emanations entered the ore formations; it composes reticulate veinlets.

Thus, here there is undoubtedly the presence of primary layers of ferruginous quartzite. But the emanation currents reworked it to a considerable degree, displacing substances and introducing new elements. In this way, it seems to me, the contradiction is resolved between the sedimentary basic and metasomatic forms of the modern ferruginous quartzites of the Western Sayan, concerning the genesis of which opinions have differed greatly (18, 73).

It is necessary to note one more feature of the ore formations under consideration: together with the enclosing schists, they were readily schistosed during all subsequent phases of tangential tectogenesis, and the iron glance was smeared along the surfaces of schistosity, giving the specimens of the ore formations a “rich” appearance.

In reality, the ferruginous quartzites and the ore formations associated with them contain little iron. The richest specimen from the southern belt yielded only 40% iron; usually the metal content fluctuates around 15–20%. It is clear that this is not ore, and, despite the considerable quantity of reserves of all these sedimentary-metasomatic formations of the Western Sayan, they cannot yet be taken into account as industrial objects.

Iron-ore deposits of this type are manifested somewhat better in the Eastern Sayan, where they have been studied to some extent at the Sydinskoye depo-

deposit located in the headwaters of the Syda River amid mountainous, dense taiga. “Red ironstones” had long been known from here, and in 1932 a special prospecting and exploration party worked here (18).

The area of the deposit is composed essentially of a green-violet metamorphic Ordovician sequence. In the lower parts of this sequence, as in the Western Sayan, there is an ore horizon up to 200 m thick. It has been traced along strike for 7 km. However, noticeable accumulations of ore minerals take the form of separate lenses within this zone, having so far been identified only over a distance of 2.4 km, nine in number; the largest lens has outcrop dimensions of 525 by 115 m.

These enriched ore formations nevertheless contain a sufficient amount of albite, chlorite, and quartz. The ore minerals are represented by magnetite and specular iron ore, the relative amounts of which vary from place to place. In addition, sulfides occur almost everywhere. The ores of the deposit have not been subjected to special sampling. Only for some samples has the average content of ore iron been established at 33%. It is clear that this is not yet ore, but it is possible that it may be easily beneficiated.

VIII. ABAKAN MAGNETITE DEPOSIT

The principal iron-ore deposits of the Khakass-Minusinsk Territory, like those of all Western Siberia, are of Middle Devonian age, being genetically associated with the intrusive Telbes formation. Among them the Abakan deposit stands out sharply; no equal to it in reserves of iron ores has yet been found in Western Siberia.

A detailed geological survey of the deposit area was carried out by Yu. A. Kuznetsov in 1927 (7). If minor corrections of a stratigraphic nature are introduced on the basis of later investigations, the geological structure of this area may be presented as follows.

The western part of the area is composed of the lower Middle Cambrian, namely the Pecherkino, Ancheshevo, Novoprosvetovka, and Arbat formations, of which the first and third are rich in acidic and partly basic effusives. They also contain limestones with archaeocyathids, which determine the age of the sequence. All these formations are strongly dislocated, but in general they form the steep WNW limb of some broad syncline.

The Lower Paleozoic denuded structure is overlain from the east and northeast by diagenetized porphyrites, which, by their general connection with the effusives of the southwestern part of the Minusinsk depression, must be recognized as Devonian. The Middle Devonian age of this formation, synchronous with the Telbes formation of Gornaya Shoria, may now be considered established (16, 142).

Into the Devonian formation, affecting at the present denudation level also the basement of the Lower Paleozoic, there intruded a hypabyssal magma that produced quartz albitite, passing into mangerite. Probably later, namely of the end of the Middle Devonian, are the fairly numerous dikes of quartz albitite-porphyries and diabase-aphyrites.

Near the intrusion, the enclosing rocks—especially the more fractured Cambrian rocks—underwent metasomatism, with the development of amphibole, titanite, epidote, chlorite, albite, calcite, and partly quartz, as well as magnetite, hematite, and sulfides, in particular pyrite and chalcopyrite. In some fracture zones there are also true skarn formations with garnet. However, no ore accumulations have been found near the visible intrusive bodies.

The ore deposits are located 2 km from the intrusion to the WNW. They are confined to the Middle Cambrian Novoprosvetovka sedimentary-effusive sequence, being subordinated to its structure. However, despite repeated

geological exploration work, from 1930 to 1933, which had the character of heavy-type prospecting, the details of this structure could not be reconstructed, since the rocks of the sequence are rather strongly altered. In addition, up to the present time the materials of all geological exploration work carried out at the deposit have not yet been fully processed, and the description below is given according to the report of K. S. Filatov (18).

The ore bodies extend along the upper part of the steep right slope of the Rudnoy Kenni brook, only 5 km from the Abakan River and from the village of Abakansky Zavod, at an absolute elevation of 800–900 m. Ore body I is a lens, 845 m long at the surface and 10 to 75 m thick. It thickens toward the NE end and thins toward the SW, and in the latter direction its dip is also observed. At depth the thickness of the lens in its middle part increases, at least within the limits of core drilling carried out to a depth of 300 m. It is accepted that this ore body wedges out at a depth of 500 m.

Ore bodies II and III are situated somewhat aside from the NE end of lens I. They are close, irregular ore outcrops, roughly 120 × 40 and 120 × 60 m in size. This is the “Abakan Blagodat,” which was worked, as was part of body I, for the Abakan metallurgical plant, which existed, with interruptions, from 1867 to 1926 and had an output of 1,650 t of pig iron per year.

As drilling has shown, ore bodies II and III probably join at depth, with their general dip to the SW, and, according to magnetometric profiles, the underground continuation of these joined bodies extends along the footwall of body I at a small distance from it; however, this supposition has not been verified by exploratory workings.

The ore bodies are rather sharply separated from the enclosing rocks, which near them have undergone substantial chloritization and epidotization. However, the ore contains quite a few vein minerals, namely: chlorite, amphibole, epidote, calcite, quartz, and partly titanite and apatite. The ore minerals—in order of decreasing abundance—are magnetite, hematite, and siderite, with magnetite grain size from 0.007 to 0.5 mm. In the upper parts of the ore bodies magnetite has passed into martite. The ores of the primary zone are fairly rich in sulfides, chiefly pyrite, pyrrhotite, and chalcopyrite; chemical analyses showed the presence also of zinc. In the oxidation zone the sulfides are usually leached out, but in places they have been preserved, which is why, during the operation of the plant, the ore was preliminarily roasted to remove sulfur. The sulfide content is uneven.

The chemical composition of the primary ores, according to samples from boreholes, fluctuates within the following limits (in percent):

Ores from the oxidation zone are somewhat richer, but the zone itself has an insignificant depth. However, along individual fissure zones, limonite injections were encountered by boreholes at depths of up to 100 m.

The average content of ore iron adopted in calculating the ore reserves, according to many hundreds of analyses, is 43%, with an average sulfur content of 2.4%.

In terms of its reserves, the Abakan deposit exceeds all other explored iron-ore deposits of Western Siberia. But the reserves of the deposit are in reality still more significant, since boreholes in the middle parts of the ore bodies, drilled to a depth of 300 m, showed an increase in the thickness of the bodies. This applies especially to bodies II and III, which are exposed by denudation in their very upper part; in one area of “Abakan Blagodat” it is clearly visible how the ore body is overlain by the enclosing mass of rocks. In addition, the underground continuation of these bodies along body I has not been explored at all and has not been included in the calculation of ore reserves.

The ore bodies of the deposit are, in general, monolithic, although within them there are many small zones of crushing and slickensiding, along which confined waters are formed. The experience of working the analogous Temir-tau deposit in the Telbes region showed that this does not hinder exploitation of the mine.

IX. IRBINSK GROUP OF MAGNETITE DEPOSITS

This group is located in the Kuragino district, on the western slope of the Eastern Sayan, approximately 100 km northeast of the city of Minusinsk, with which it is connected by a good cart road. The group consists of several deposits situated over a distance of 4 km in a single row of meridional strike, along the western contact of a quartz monzonite massif with Cambrian limestones and with basic and acidic effusives of indeterminate age, also including the intrusive itself. In composition, the deposit is contact-metasomatic. But from the description of all the preceding deposits of this type it is evident that the contact position of these ore bodies is determined by structure, and not by the influence of those emanations that issued into the contact zone from the visible intrusive massif.

A. I. Aleksandrov, in his candidate dissertation, cites the general opinion that the Irbinsk deposit is of Telbes age. Indeed, the similarity with the structure of the typical iron-ore districts of Gornaya Shoria is confirmed by the fact that the indicated contact zone is intersected by dikes of albitite-porphyries and diabasophyrites of the Abrámov phase of tectogenesis.

Exploration of the group was interrupted in 1933, and the results of processing the collected materials have already been published, though in the form of a very brief article (18, 73). The exploration consisted of geological and magnetometric surveying, the driving of surface and shallow exploratory workings, and core drilling at one of the deposits of the group, namely Zheleznoe. In all, there are five deposits in the group (from south to north): Granatovoe, Rudnoe, Svintsovoe, Zheleznoe, and Bezymyannoe. Of these, only the Granatovoe, Zheleznoe, and Svintsovoe deposits are of considerable size.

The ore bodies have the form of lenses and stocks dipping steeply to the west. In most cases they have recently been exposed by denudation, while at the Granatovoe deposit they are, to a considerable degree, still covered by garnet skarns, having been revealed only by exploratory work in 1930; although the group has been known for a long time, and on its ores from 1734 to 1829 there worked ...

the first small metallurgical plant in Siberia. At the same time, the dimensions of the bodies in their outcrops at the surface are quite considerable. Thus, the main ore body of the Granatovoe deposit measures 385 × 45 m, with a depth of continuation, according to magnetometric data, in the middle part of the body of up to 420 m; the dimensions of the main ore body of the Zheleznoe deposit are 320 × 17 m, with a possible depth of continuation of not less than 225 m, penetrated by drilling only to 75 m.

The composition of the Irba ores has not yet been completely studied, since a large part of the samples comes from the oxidation zone. Table 2 gives the results of a chemical analysis of an average ore sample from the cores of borehole No. 1 on the main body of the Zheleznoe deposit and from surface workings on the main body of the Granatovoe deposit.

Magnetite is locally replaced by specularite, which at the Svintsovoe deposit was taken for galena. In the oxidation zone—for example, of the Rudnoe deposit—magnetite has partly changed into martite. Among the sulfides encountered so far are pyrite and a little marcasite, chalcopyrite, arsenopyrite, and sphalerite. The skarn minerals are represented by andradite, epidote, actinolite, quartz, and calcite. In general, the mineralogical and chemical composition of the ores is of the Telbes type.

Table 2.

Chemical composition of average ore samples from the Irba deposits.

It is likely that it will prove to be more varied when deeper horizons of the deposits are studied. It must also be thought that the ore will prove to be more sulfurous than is shown by the analyses.

The ore reserves in the deposits of the group have been calculated essentially from data from surface workings and from magnetometric indicators, which have been sufficiently verified at a number of well-studied deposits of the same type.

The principal reserves of the group are located in the Granatovoe deposit. They have been classified only in category C, since no core drilling has been carried out here. It is possible that the actual iron content in the primary ore of the deposits will prove lower than that revealed in the oxidation zone, and then the average iron content in the ores of the Irba deposits will be the same as in the Abakan deposit.

X. THE TEYA GROUP OF MAGNETITE DEPOSITS

The group is located on the watershed of the Abakan and Tom rivers, in the upper reaches of the Teya River, of the Abakan River system, and of the Tuzuksu River, of the Tom River system, at an absolute elevation of about 1,000 m. The terrain is mountainous taiga, with only trails. The group is most readily accessible from the side of the Abakan steppe.

The ores of the group were found by I. K. Bazhenov during the geological-prospecting survey of 1930. In the following two years exploratory work was carried out here, interrupted in 1933. The materials of the geological-exploration work were processed and published by I. V. Derbikov (4) and A. A. Mesyaninov (8). But since the investigations carried out were still insufficient—especially as the watershed is poorly supplied—a number of disputed questions remained concerning the geology of the district. In the light of later achievements in the study of the geology of Western Siberia, the geological structure of the district of the group may be represented as follows.

The foundation of the district consists of Carboniferous limestones and dolomites, which, as may now be considered established, belong to the Algonkian. The structure of this formation is subordinate to akmolith bodies of gabbro-diorites and quartz-augite diorites, to a considerable degree amphibolized and sossuritized. This, it must be thought, is an intrusion of the end of the Algonkian. Gold mineralization in the Kuznetsk Alatau is usually associated with it. And it must be said that placer gold, as well as heaps of gold-bearing quartz, have been encountered in the district.

The limestone-dolomite sequence with interbeds of siltstones is overlain by a formation of green-gray sandy shales, outside the limits of the district also containing effusives and limestones with archaeocyaths, apparently of Middle Cambrian age.

Apparently, at the end of the Cambrian this ancient sequence was intruded by magma of granodiorites and quartz mangerites, which produced a rather sharp contact metamorphism of the enclosing rocks. During almost the whole of the Silurian denudation took place. In the Tuvinian age of the Gothlandian there were powerful extrusions here of acid lava, lying directly on the denuded surface of the indicated intrusive bodies. The intrusion of nordmarkite should probably be assigned to the Ardennian phase of Caledonian tectogenesis; under its influence the acid effusives in the corresponding places underwent slight contact metamorphism.

I. V. Derbikov considers that the intrusion of the nordmarkite magma occurred after the formation of a large fault, along which the deposits of the group are situated, and that the latter are genetically connected with this intrusion, to which a Telbessian age was assigned. Now, however, this conception has to be changed. First, nordmarkites, or alkaline syenites in general, are unknown for the Telbessian phase of tectogenesis; it is true that in the Abramovka phase of the end of the Middle Devonian there were intrusions of alkaline syenites, but they have a different composition and were not accompanied by magnetite emanations. Secondly, as is evident from the geological card of the Elgentag deposit of the Teya group, the magnetite bodies are situated in a zone that cuts the nordmarkite, as well as other more ancient rocks. Finally, as is evident from the general section of the district, the fault and the uplift of the NE part of the district occurred after the emplacement of the nordmarkite intrusion. It may be thought that movements along the fault zone also occurred after ore formation, for the ore bodies are confined chiefly to the lying SW wing of the dislocation; moreover, only on this wing have deposits of the end of the Middle Devonian, characterized faunistically and not having undergone any changes, been preserved from denudation.

Thus, the mineralization of the district was after the Upper Silurian and

until the end of the Middle Devonian; i.e., it belongs to the Telbess tectogenetic phase. It is interesting that no visible bodies of the corresponding intrusion have been found at the deposit sites. But this is not essential, since, as we have seen in a number of examples, the ore-bearing emanations are connected not with visible magmatic bodies, but with a deep-seated magmatic source. True, the skarned effusives of area II of the Teiskoye deposit proper are cut by a dike of some porphyritic granite, but the age both of this granite and of the effusives of the deposit, which occur among dolomitized limestones, is unclear.

The Tei group consists of the Teiskoye, Tuzukhinskoye, Elgentag and Khabzasskoye deposits, arranged in the indicated order from south to north along one zone for a distance of 8 km. Of these, the Khabzasskoye and Tuzukhinskoye deposits are insignificant, while Elgentag has been studied only by magnetometric survey and opened by a sparse network of trenches. The principal object of exploration work was area II of the Teiskoye deposit proper, whereas its areas I, III, IV, V and VI, being insignificant, have been explored very poorly. In turn, area II consists of the Main body and bodies A, B, C and D, and almost all workings are confined to the Main body, to which we shall now turn.

The Main body has a detailed magnetometric characterization; it has been cut by transverse lines of continuous or discontinuous trenches 25–50 m apart and opened by five core drill holes to a maximum depth of 185 m. It is elongated in a meridional direction, with a surface length of 1070 m, and is divided into northern and southern parts, being strongly constricted in the middle part, which is composed of skarns; this is fully reflected also in the magnetometric map of the area. The average visible width of the body is 131 m. The total area of its outcrop beneath the cover deposits is 140,630 sq. m, which almost corresponds to the area enclosed within the contour of the isoline of the vertical component of magnetic intensity at 0.5 H₀.

The ore body dips rather steeply to the west. On its footwall side there are predominantly dolomitized limestones, and on the hanging wall side, certain effusives, which farther west are again replaced by ancient limestones. It has a very variegated composition, and it is almost impossible megascopically to distinguish poor skarns from ores, since everything is impregnated with serpentine, which imparts to all formations a dark and “ore-like” coloration; only individual portions of limestones and slightly altered effusives can be separated from the general monotonous mass of the body. Therefore very detailed sampling was required in order to form a proper idea of the composition and structure of the ore body. In general, it proved possible and necessary to distinguish: mineralized rocks with an iron content below 25%, ores with 25–30%, 30–35%, and more than 35% iron, occupying respectively 35, 14, 9, and 42% of the area of the ore body’s outcrop beneath the cover deposits. Approximately the same ratio is also found in the drill holes.

The weighted average content of ore iron in the explored part of the Main body is 30.84%. To characterize the chemical composition of the ores of the deposit, Table 3 gives the results of analysis of three samples: No. 1—sample from trenches of the X exploration line of the northern field, No. 2—the same from the southern field, and No. 3—from drill hole No. 3. It should be noted that the Tei ores are distinguished by a high content of magnesium oxide, corresponding to the constant presence of serpentine in them. In addition, mineragraphic analysis reveals in the ores an admixture of chalcopyrite, as well as sphalerite, galena and safflorite, the elements of which were not detected by chemical analysis.

I. V. Derbikov, who studied the ores of the deposit chalсographically, distinguishes three stages of mineral formation, separated by deformational unconformities. In the first, skarn stage, diopside, hedenbergite, garnet, epidote, chlorite, prehnite, tremolite, and quartz were deposited successively. The second, ore stage proper, is characterized by the almost simultaneous separation of two varieties of magnetite and of serpentine, as well as phlogopite and calcite. In the third, carbonate-sulfide stage, dolomite, siderite, calcite, pyrite, and a small amount of other sulfides, hematite, and hydrohematite were deposited.

Table 3

Chemical composition of average ores of the main body of Sector II of the Teya deposit

Of particular interest are the mineral formations of the ore stage, which are a very fine mixture of magnetite and serpentine; in the opinion of I. V. Derbikov, this mixture was formed through the interaction of colloidal saturated solutions with dolomites, with part of the magnetite receiving magnesium oxide and alumina into solid solution.

The very fine-grained structure of the ore greatly hampers its beneficiation, as shown by preliminary tests by Mekhanobr. It was found that only ores with an iron content above 35% can be considered industrial. As for the poorer ores, which make up the main content of the Teya deposits, substantial additional investigations are necessary in order to determine the possibility of using them.

In calculating ore reserves, it was not possible to distinguish especially rich sectors. Therefore, the ore reserves calculated from data from workings and magnetometry can be used only after the basic question has been resolved concerning the possibility and limits of beneficiation of the generally poor ores of the Teya group.

XI. OTHER DEPOSITS.

In addition to the deposits described, on which integrated exploration was carried out, many ore occurrences have been identified in recent years during geological prospecting investigations. Some of them have been covered by magnetometric surveying and light exploratory work. A brief characterization of them is given below (18).

1. In the watershed area of the Kuznetsk Alatau, in the region of the already described city of Patyn and the Shor-Taiga bald mountain, many points have been discovered with dumps of magnetite ores or with significant magnetic anomalies. Of these, only the Kaskyl deposit, located near the summit of the Shor-Taiga bald mountain at an absolute elevation of 1400 m, has been surveyed by a sparse network of magnetometric measurements and slightly opened by earthworks.

The ore sectors of the deposit, discovered in 1933, are confined to the contact of an intrusive body with an ancient sequence composed of clay shales, graywackes, and limestones. In all, 5 sectors have been identified. Of these, only one is of comparatively significant size, having, within the contour \(V_a = 0.5 H_0\), an area of 67,500 sq. m. But even this sector consists of separate lenses and stockworks of magnetite ore in skarns.

Apparently, the intrusion is of Upper Cambrian age, since it is represented by various rocks, from gabbro-diorites to granites. If this is so, then by analogy with the studied deposits of this age one may think that the Kaskyl deposit, too, is hardly of industrial value as an iron-ore deposit. In addition, it is located on a bald mountain, under difficult economic conditions.

1. In 1932, a magnetometric prospecting survey was carried out over the area between the rivers Kamyshty, Syry, and Uzyundzha. This Kamyshta-Syry district occupies a favorable geographical position, and several points with magnetite-hematite ores were known from it. Unfortunately, the magnetometric survey revealed only areas of weak magnetic disturbances. The opinion was expressed that this might be due to the substantially hematitic composition of the ores. However, this is hardly so. Recently, a detailed geological-prospecting survey for rare heavy metals, and partly for barium, has been carried out here in many places. These surveys established that the mineralization everywhere is caused by an Upper Cambrian intrusion. In particular, M. M. Runin showed this in 1934 in the area of Lake Bulan-Kul. But we have already seen that this intrusion did not yield serious reserves of industrial iron ores.

2. Turning to the Eastern Sayan, we find several ore points in the region of the Irba deposits. Such, for example, is the Nizhne-Kizyr deposit. In 1931, a detailed magnetometric survey was carried out on it, and in the following year light exploratory work. It turned out that, in structure and ore composition, this deposit is of the same type as the Irba deposit.

3. At 30 km from Irba, on the left bank of the Kizyr River, near the Minusinsk-Artemovsk road, lies the Mulga deposit, discovered in 1932. The geological setting of this deposit is approximately the same as in the Irba group. A detailed magnetometric survey was carried out on it. By analogy with Irba, the area contoured by the isoline \(V_a = 0.5 H_0\) was taken as ore-bearing, and the depth of ore distribution was taken as 100 m.

XII. CONCLUSION.

A summary of the more or less explored reserves of iron ores of the Khakass-Minusinsk deposits shows that the situation is not entirely favorable.

First, the average content of ore iron in these reserves is only 38%. Hence it is evident that the ores require complex and, perhaps, rather expensive beneficiation, experiments on which have been carried out on a sufficient scale only for the ores of the Abakan deposit.

Second, and this is the main point, some deposits have still been studied so ...

is so weak that it is impossible to rely on the existing estimates of ore reserves. This remark applies especially to the Sydinskoye deposit, whose ores are very poor and, because of the presence of a large amount of silica, are probably difficult to beneficiate. The same must also be said, relatively, of the Teya group of deposits, whose ores are likewise very poor and, as the first beneficiation experiments have shown, are almost not amenable to improvement. In any case, the utilization of the Syda and Teya ores remains a problem not yet solved.

Third, sufficiently reliable ore reserves exist only in the Abakan and Irba deposits. However, the reserves of ores in the higher categories of exploration at the Irba deposit amount to only 7% of the total reserves.

It is therefore necessary to resume exploration work in the Irba group, where few boreholes were drilled and only to shallow depths. And, in general, prospecting and exploration investigations should be resumed in the iron-ore districts of the krai, for, as we have seen, the degree of exploration of most of the identified ore occurrences is slight. It is also necessary to undertake beneficiation experiments.

LITERATURE

1. Bazhenov, I. K.—Report on geological investigations in the area of the Maina copper deposit, Minusinsk uezd.—Izvestiya of the Siberian Branch of the Geological Committee IV-1, 1924.

2. Same.—New iron-ore deposits of the Western Sayan.—Bulletin of the West Siberian Geological Prospecting Trust, 1932, No. 2; 34—41.

3. Vasiliev, A. A.—Iron ores of Western Siberia. Mineral Resources of the West Siberian Krai, 1. Metals.—1934, 10—56.

4. Derbikov, I. V.—The Teya-Tuzukhsinsky iron-ore district of the Kuznetsk Alatau.—Materials on the Geology of the West Siberian Krai. Issue 26, 1935, 1—III.

5. Kalinnikov, D. I.—Podlunnyi Golets—the base of the Bolshoi Kommunar.—Collected Works of the All-Union Trust “Zolotorazvedka.” Issue 2, 1936, 45—68.

6. Komarov, I. P.—The Patyn titanomagnetite deposit.—Mineral-Raw-Material Base of the Kuznetsk Metallurgical Combine named after I. V. Stalin, Tomsk, 1933, 122—127.

7. Kuznetsov, Yu. A.—Geological structure of the Abakan iron-ore deposit.—Izvestiya of the Siberian Branch of the Geological Committee VIII. 3—1929.

8. Mesyaninov, A. A.—The main body of the Teya iron-ore deposit.—Materials on the Geology of the West Siberian Krai. Issue 26, 1935; 113—145.

9. Nekipelov, M. E.—The Maina sulfur-pyrite copper-zinc occurrence.—Materials on the Geology of the West Siberian Krai, Issue 16, 1934.

10. Obruchev, V. A.—Deposits of iron and manganese ores of Siberia and their industrial significance.—Proceedings of the Commission on Metal under Gosplan of the USSR. No. 6, 1926; 27—54.

11. Poletaeva, O. K. and Shatrov, I. E.—Geological structure of the northern slope of the Western Sayan in the area of the rivers Tabat and B. and M. Arbaty.—Materials on the Geology of the West Siberian Krai. Issue 33, 1936.

12. Radugin, K. V.—Elements of the stratigraphy and tectonics of Gornaya Shoria.—Materials on the Geology of the West Siberian Krai. Issue 37, 1937.

13. Usov, M. A.—Geological structure and reserves of iron ores of the Telbes district.—Materials for the Study of Siberia. Tomsk, 1, 1930, 1—75.

14. Same.—Geology of ore deposits of the West Siberian Krai.—Tomsk, 1935.

15. Same.—Sources of metasomatic alterations of the Lower Silurian sequence of the West Siberian Krai.—Article in Izvestiya of the Academy of Sciences of the USSR for 1936.

16. Same.—Phases and cycles of tectogenesis of the West Siberian Krai.—Tomsk, 1936.

17. Same.—The hyperbasite formation of the West Siberian Krai.—Article in the jubilee collection for Academician V. A. Obruchev, 1937.

18. Filatov, K. S.—Khakass-Minusinsk iron-ore deposits.—Mineral Resources of the West Siberian Krai, 1. Metals. 1934, 57—83.