Proceedings of the Tomsk Technological Institute

of Emperor Nicholas II.

Vol. 12. 1908. No. 4.

I.

S. Yu. Doborzhinsky.

The Southeastern Part of the South Russian Manganese Deposit

With appended tables, drawings, and a map.

1–19.

Owing to the historical events of recent times, the Caucasus, the chief supplier of manganese ore to the world markets, has greatly reduced its productivity. At the same time, demand for this material—because it is finding ever greater application in metallurgy—has not only failed to decrease, but on the contrary has greatly increased. These circumstances have compelled mining industrialists to pay greater attention to the South Russian manganese deposit in the vicinity of the city of Nikopol on the Dnieper, where the extraction of manganese ores at the present time is relatively small in comparison with their reserves.

In the summer and autumn of 1906 I carried out exploration in the vicinity of the village of Gorodishche, by commission of the Dnieper Society; the data obtained I set forth here. From a technical standpoint these explorations present nothing exceptional; therefore I shall touch upon this aspect only in passing, devoting greater attention to the conditions of occurrence of the ore and to its properties.

The excellent monograph on the manganese deposit of this region, compiled by Sokolov, enables me to confine myself solely to the new facts obtained by the explorations, and to the new views that have arisen as a result of the broadening of our horizon in the field that interests us.

Since Sokolov studied chiefly the western part of the deposit—the Pokrov economy and others—whereas I explored the vicinity of the village of Gorodishche, these new works constitute a natural supplement to the factual material published by Sokolov.

Geological sketch of the village of Gorodishche and its environs.

In orographic terms, the area of interest to us is uneven and undulating. The relief of its surface is generally similar to that of other parts of the Dnieper littoral in the steppe portion of its course. The undulating character of the area is due to a system of ravines and dry streams, the so-called balkas, along the slopes of which one may observe excellent natural exposures of the rocks composing the surface of the earth. The totality of natural exposures, mine workings for the extraction of manganese ore, and exploratory workings gives us the opportunity to form a fully clear idea of the geological structure of this locality.

The foundation of all the sedimentary rocks here is gneisso-granite, whose outcrops may be observed along the banks of the bed of the Tomakovka stream, in the Greater and Lesser Kamenka rivers. Granite, moreover, was discovered in a whole series of shafts sunk by mining engineer Voinovich on the northern side of the present mine between the Tomakovka and B. Kamenka. This rock consists chiefly of quartz and orthoclase, with a small amount of mica, which at times is entirely absent. Sometimes no foliation is noticeable, and then the rock we are describing must be regarded as granite; at other times the schistosity is quite clearly expressed, and then it should be called gneiss. Besides schistosity there is also jointing, caused by an entire series of systems of vertical and horizontal fissures. The predominant directions of the fissures are NW 350° and 310°, NO 55°–60°; there are NO 20°–70°, as well as 140°–150°. In addition, veins of coarse-grained granite and dark-gray syenite occur in the gneisses. Between the B. Kamenka and Tomakovka streams one must suppose the existence of a granitic ridge, along which the named streams flow. In the balkas that empty into these streams, as well as along their banks, the granite is covered directly by diluvium: loess and brown-red clays; in the shafts on the northern side of the mine, however, green Oligocene clay is already encountered. In the southerly direction the section becomes more complete, as far as the broad river valleys of the Tomakovka, Revun, and Rechishcha,

in which the granites are directly overlain by the most recent alluvia, consisting chiefly of quartz sand of various grain sizes, with an admixture of grains and pebbles of feldspar and, more rarely, pyrolusite, as well as of interbeds of river silt.

On the southern, lowered part of the above-described ridge is situated the Gorodishche mine; on the southeastern slope—the Nikolaevsky; and on the southwestern slope several boreholes were put down by the mine surveyor Boikovsky, which discovered manganese ore. The conditions of occurrence of the manganese ore in the Gorodishche mine are as follows: upon an extremely uneven, wavy, jagged surface of granite-gneisses lie the products of their own decomposition: sand, consisting of angular quartz grains; kaolin, white or pink, or sometimes gray from the finest particles of pyrolusite; and green sandy clay. In these deposits, which partly smooth out the irregularities of the granite floor, there are abundant remains of marine fauna, on the basis of which the age of these deposits is assigned to the Tertiary—Oligocene—stage.

The manganese-ore bed is extremely uneven, chiefly owing to the unevenness of the granite, but there are also traces of erosion: for example, the upper part is absent, so that the overlying green clay rests directly upon its lower part; this is an old erosion. Near ravines one sometimes observes the occurrence, directly upon the manganese, of brown clays or loess; this is the result of erosion in the post-Tertiary epoch, before the deposition of diluvial sediments. I am also aware of cases of direct occurrence of modern deposits upon manganese ore.

The lower part of the ore-bearing bed consists of small pea-like concretions of pyrolusite up to an inch in diameter; the thickness of this layer averages about 0.4 meters. This is the part of the bed richest in percentage content of manganese. Above lies a black sandy clay (black from an admixture of pyrolusite), in which there are two or three interbeds of granular ore, and, in addition, grains of pyrolusite are unevenly scattered through it.* The layer of granular ore is sometimes found in the middle of the bed. The total thickness of the bed is up to 2.8 meters.

The extent of the part of the bed now being worked is bounded on the southern side by the valley of the Tomakovka River, in which it has been washed away, and it appears again on the other side of the said valley on the lands of Nevelina and Trubchaninov, where it was discovered by means of several prospect pits and boreholes and, in part, was even worked.

* Cf. Sokolov.

Natural exposures in the Otchepatevka ravine and in the gullies that fall into the Tomakovka valley, near the state forest dacha of Rakshina, are in general similar to those described by Sokolov in the ravines of the estates Mys Dobroi Nadezhdy and Grushevka.

The lower parts of the Sarmatian stage and the bed of manganese ore are not exposed in these ravines and lie below the level of the Dnieper. The limestones of the Pontic stage are also exposed on the island of Gorodishche, a former Cossack stanitsa, from which the present village took its name; the same limestones occur in the stone quarry on the boundary with the lands of Krasnogrigorievka, near which Bonkovsky’s boreholes were sunk. Apparently the Pontic limestones are distributed over almost the entire area under study in its more elevated parts; they, and likewise the whole Sarmatian stage, lie somewhat discordantly with the bed of manganese ores and with the surface of the granites, which have a certain dip to the south, whereas the upper beds are either entirely horizontal or at times somewhat inclined to the north.

General Plan of Exploration

Since it was necessary to determine, in the shortest possible time, the area occupied by the manganese deposit and its average thickness, then, despite the incompletely clarified character of the occurrence of these ores, it was decided to drill boreholes at fairly large distances from one another, namely at 400 meters along lines of the general strike, EW, and, moreover, in such a way that the boreholes would fall in a staggered arrangement. Since the northern boundary of the Trubchaninov estate approximately coincides with this direction, it was decided not to wait for the final survey of the plans and the staking out, but to begin work on this boundary, and then, as the number of drilling tools increased, on other lines parallel to this boundary, at a distance of 400 meters from one another. The boreholes were made according to the assigned position, without being troubled by differences in the indications of two adjacent ones, in view of the known variability of the manganese bed both with respect to thickness and to other properties. In the event of a major discrepancy in the determinations obtained by two adjacent boreholes, it was intended to drill intermediate ones between them; in actual fact, however, it was almost never necessary to resort to this measure.

In order to make it possible to compare the quality of the ore in the boreholes, the samples obtained were subjected to analysis: it was determined ...

the quantity of grains \(>2'\) tons and \(<2\) tons, and the percentage content of manganese and silica. Although by this means it is not possible to learn the actual suitability or unsuitability of the ore for extraction, nevertheless the data of the analysis, taken together with the other data—that is, the character of the ore grains, the thickness of the bed, its structure, strike and dip, and the properties of the rocks covering it—finally make it possible to draw certain conclusions as to whether the properties of the ore in the given area are uniform or varied. From the area explored by boreholes there were selected plots of 600,000–800,000 m², along which the bed proved, in its thickness, suitable for development, and the ore on the whole uniform; and in the middle of these a prospect pit or shaft was sunk, depending on the depth and stability of the rocks. In the case of shallow occurrence, pits of \(1 \text{ m.} \times 2 \text{ m.}\) were sunk; when it was necessary to go to a depth of 20–40 meters, especially if quicksands were present, shafts of \(2.10 \text{ m.} \times 2.30 \text{ m.}\) were used, more substantial in dimensions and in the method of timbering, and therefore better ensuring the success of the sinking.

Examination of the section of the bed in the drifts driven from the shaft, chemical analysis of the ore from samples taken from different points of the bed and the drift, and, chiefly, the bulk sample of ore obtained at the washing plant, served as material for the final determination of the suitability or unsuitability of the given area for development.

Performance of Exploratory Works

At the same time 8 drilling rigs were in operation; the drilling was mainly hand-rotary, with the aid of an auger and a spoon. Harder rocks (limestones) were penetrated by percussion drilling with sliding shears. The work was made somewhat difficult by water-bearing sands and quicksands, of which the lower one, lying directly on the green clays that cover the manganese, was in places rather troublesome and required casing with casing pipes. During further work the upper sands became smeared with clay and ceased to cave in by themselves.

Work in the upper horizons proceeded very well: 3–4 and up to 6 sazhen were drilled per shift; in the viscous clays of the Sarmatian stage it became less successful. With the lower quicksand one generally had to struggle for several days, so that for shallow boreholes of 20 to 30 meters one must count on 4 meters per shift, and for deeper ones 2 meters or less, depending on circumstances.

With each raising of the rods, a sample of the drilled rock was taken and placed in a special box with partitions. The thickness and name of these rocks were recorded in a notebook by the senior worker of the borehole himself or, in the event of his illiteracy, by the foreman. Each day the depth of the boreholes was checked with a tape measure and entered, as was the name of the rocks, in the rough journal of drilling operations kept by the foreman. During the drilling of the manganese bed, the foreman or a senior worker was invariably present. After completion of a borehole, the records, checked and compared with the rock samples, were entered in the general drilling journal, in which the results of analysis and of hand washing of the ore from the boreholes were also noted.

The lines of drilling work were leveled along the boreholes, each of which is marked in the journal and on the plan with a number according to the order in which it was laid out. Five new shafts and prospect pits were sunk; in addition, for conclusions we made use of ready-made shafts in the estates of the Shishkins and Nevelina.

The timbering in the prospect pits was, at the top, in loess and clays, sheeting timbering with lagging boards; in the sands, close-set timbering. The shafts were secured throughout with close-set timbering. Driving proceeded rather slowly, especially in the clays of the Sarmatian stage.

To a depth of 16 meters, hoisting by a hand windlass was used; thereafter two horse gins were installed, one for hoisting the ore, the other for water drainage.

The journal of shaft sinking was kept according to the general method described above.

The Trubchaninovs’ Estate.

The first borehole (No. 1) was laid out on the northern boundary of this estate, which we shall regard as the first reconnaissance line. The borehole passed through loess, river sand, green clay, and was stopped in angular quartz gravel with clay and a small quantity of pieces of feldspar, as well as lumps of calcareous material. Borehole No. 2 revealed the same rocks, only the layer of green Sarmatian clay above the gravel was somewhat thicker. Exactly the same results were obtained from boreholes Nos. 3 and 4; it was then decided to turn westward; in borehole No. 5, after passing through the same rocks, 0.60 m of manganese was found; the adjacent borehole No. 6 already passed through a full bed of manganese ore, beneath which lies sand very similar to that described above under No. 1, with white kaolin. Borehole No. 7 showed 0.80 m of manganese ore, directly—

directly beneath the river alluvium, into which rounded pebbles of pyrolusite had occasionally fallen; green clay is absent here. Borehole No. 8 ran throughout in river sands, interbedded with thin layers of silt; pebbles of pyrolusite were encountered. It is evident that on the western side we are dealing with a river scour, which washed away all the Tertiary deposits, including the manganese bed; traces of it remained in the river deposits in the form of pebbles.

On the eastern side, however, toward boreholes Nos. 1, 2, 3, and 4, there apparently approaches part of that granite ridge of which we spoke earlier; here we have, probably, a bar of shoal, which, in the form of a long narrow strip, cut into the Oligocene sea; angular gravel and lumps of limestone are nothing other than the littoral deposits of this sea.

A schematic section of this part of the property along the exploration line may be represented as shown in Drawing No. 1.

The works described outlined the further course of exploration: on the one hand, it was necessary to determine the limit of the scour by the Tomakovka River; on the other, the extent of the granite ridge of the shoal, by which the spread of the manganese deposit is bounded from the east. The former is provided by the terminal western boreholes, the latter by the eastern ones; the boundary of the spread of the manganese deposit is marked on the appended plan. As regards the thickness of the bed, the deposit is also fairly variable, although a certain general decrease of it toward the south is observed. On the plan, at each borehole, the thickness of the bed of ore passed through is indicated.

The direction of strike and dip of the bed is, in general, extremely variable. Upon a more careful consideration of these directions, however, a whole series of local trough-like depressions and saddle-like elevations becomes clear. Along the line of the old second Trubchaninov mine, Nos. 5 and 15 of the drilled boreholes, there exists some irregularity of structure, which is apparent from the data of the indicated boreholes; moreover, granite was encountered by the western exploration adit from mine No. 1, and the ore began to rise. The magnitude of the angle of dip fluctuates between 0 and 10′, with all possible directions of this dip, as was indicated.

In mineralogical respect, judging by the fragments of grains obtained from washing the drilling samples, the properties of the ore change in the direction from north to south; namely, its grains become harder, more angular, and in color it is browner. It should be supposed that the change in physical properties is connected with the chemical composition, and the question arises whether here we are dealing with pyrolu—

South Russian Manganese Deposit

...zit? Is this ore not, in a certain sense, a transition to brownite? Of course, the phenomenon observed in the sample must outline itself in its clearest form at Shishkin’s outcrop; this we see in fact, and therefore we shall return once more to this subject.

In the northern part of the Trubchaninovs’ estate the ore, in general, does not differ from that mined at the Gorodishche mine. The southern part beyond shaft No. 1 serves as a transitional link to the Shishkins’ type of ore. Test pit No. 0 and shaft No. 1, sunk in order to determine the quality of the ore by means of samples at the washing plant, confirmed the supposition, made on the basis of drill samples, concerning the similarity of the ore in the northwestern part of the Trubchaninovs’ estate to the ore of the Gorodishche mine. It proved to be quite good-quality. The bed consists chiefly of granular ore with several short interlayers of gray clay not confined to definite horizons. Above lies the so-called prisukha, that is, fine ore disseminated in a thin, 0.2-meter bed of limestone. The thickness of the entire bed in the test pit and in the crosscuts driven from it—that is, granular ore with soot—is about 2.70 m; in shaft No. 1, 2.00 m. The entire area occupied by the bed in the western part of the Trubchaninovs’ estate amounts, in round numbers, to 1,250,000 sq. meters, if from this figure one subtracts 150,000 sq. meters of those parts in which, apparently, the bed, owing to its small thickness, is unsuitable for exploitation. Over the remaining area its average thickness is 2.20 m; thus its reserve in cubic meters is determined approximately by the figure 2,400,000 cu. m.

In the eastern part of the estate, exploratory borehole No. 29 found 1.20 m of manganese ore; from the sample obtained it is not even possible to determine approximately the character of the ore, still less its suitability or unsuitability for exploitation. The sample contains a large quantity of sand; this phenomenon is explained by the fact that wet sand, lying above the green clays, being uncased by the pipes, freely penetrated to the ore and mixed with it during drilling. In the fragments of ore grains, pieces of quartz were not observed, so that the question whether this ore will resemble the ore of the neighboring Nikolaev mine or not remains open for the present. The considerable quantity of sand in the sample indicates a similarity to the Nikolaev ore, which, precisely because of its high quartz content, was deemed unsuitable and is not being mined at the present time; but, on the other hand, the sandiness of the Nikolaev ore is closely connected with the structure of its grains themselves, which are something like lumps of coarse-grained sandstone cemented by manganiferous material;

even small fragments of grains of this ore are not devoid of quartz inclusions, which are absent in the ore from No. 29.

The deposit—a bed—found by us undoubtedly lies on the eastern slope of the granite ridge, whose western boundary, in relation to the manganese bed, has been traced almost throughout the entire extent of the Gorodishche, Trubchaninov, and Shishkin mines; and future exploration of it in this part should be conducted eastward and southward.

In all probability borehole No. 29, judging by the thickness of the ore bed penetrated by it, struck its western edge, so that the boundary of the granites must lie not far from it. Since this boundary, in its general outlines and approximately, should be parallel to the axis of the granite ridge (NS), with some deflection to the west caused by the gradual narrowing of the ridge, it may be supposed that the eastern corner of the Trubchaninovs’ estate will prove ore-bearing.

The Shishkins’ Estate.

Exploration work has revealed that the entire eastern part of the estate is occupied by granites, whose boundary is indicated on the map. Outcrops of the granite ridge on the surface have been found at the Rechishche ravine, so that the direction of the ridge axis can now be indicated rather precisely: throughout the Trubchaninovs’ and Shishkins’ estates the axis of the ridge has a N S direction and passes near the eastern boundary of the Shishkins’, so that the absence of manganese ore in this part of the estate is almost beyond doubt. This conclusion, based on general data, is confirmed by: 1) the exploratory boreholes of Mr. Miklashevsky, drilled prior to the present explorations; 2) the fact that manganese ore was found much farther east in the estates of the Ilyins and Shponka, adjoining the eastern boundary of the Shishkins’. Borehole No. 29, which discovered ore at the Trubchaninovs’, also lies much farther east. According to the information I have collected, the ore at the Ilyins’ and Shponka’s is bounded on the west by granites, which are in all probability nothing other than the eastern slope of the ridge with which we are dealing.

Thus, only the western part of the estate is ore-bearing, constituting the direct continuation of the bed of Gorodishche and the Trubchaninovs’. The northern boundary of this area is the boundary of the Trubchaninovs’; the western boundary is the washout of the Tomakovka River; from the southwest adjoin the likewise ore-bearing lands of the village of Marievka, explored by Mr. Beklemishev. The southern boundary is formed by the Dnepr washout, marked—

shown on the appended map. The boundary of the erosion of the Tomakovka River has been determined quite precisely, from the relief of the locality and from boreholes; the erosion of the Dnipro had to be indicated, guided by the relief, by the direction of flow of the branch of the Rechishche, and by the outermost southern boreholes of Miklashevsky. In any case, a completely exact determination of the southern boundary of the deposit has no practical significance for ascertaining the size of the field suitable for exploitation.

A schematic section of the southern part of the area under discussion may be represented by Drawing No. 2.

Thus, between the vertical lines AA′ and BB′ the Upper Tertiary deposits have been washed away; their place has been occupied by new river formations—sands and gravel, naturally saturated with water. In view of this, the part of the bed, in the area bounded by the line AA′, which on the plan corresponds to the blue line, and BB′—on the plan the dotted blue line—lies either directly beneath quicksands, or is separated from them by a thin interlayer of clays that have survived the erosion; consequently this area is wholly unsuitable for exploitation, owing to the technical difficulties in sinking shafts through quicksands and the possibility of their breaking into the workings during collapses. I consider it necessary to draw attention to the circumstance that the sands lying above the green clays that cover the manganese are in the southern part of the Shishkin estate everywhere water-bearing, so that in general the sinking of at least one quicksand horizon must be borne in mind.

Thus, from a practical point of view, it is more necessary to determine precisely not the boundary of erosion, but the boundary of the upper quicksands, which occupy the entire ancient Dnipro channel, outlined on the surface by terraces. In the locality I describe, terraces I and II merge almost imperceptibly into one only slightly sloping plain; only the third terrace, III, is quite distinct, at the foot of which the river deposits and quicksands end. At this place we sank shaft No. V, abandoned because of the malignancy of the quicksand encountered in the lower part of the yellow loess-like clays, and boreholes Nos. 48, 49, and 51, in the first two of which no quicksand was found. Taking into account the data from these prospecting works and the relief of the locality, which by itself makes it possible to reconstruct fairly accurately the outlines of the ancient channel, I have designated the boundary of the quicksands (presumed) by a dotted blue line, passing north of No. V and south of 48 and 49.

In the valley of the Tomakovka River the same phenomenon is observed, though not in so pronounced a form, so that the boundary of the complete and partial erosion in that part of its course which it washes from

west of the estates of the Shishkins and Trubchaninovs, pass very close to one another; to the north of the Trubchaninovs’ boundary, and likewise to the south of the present Gorodishche mine, these lines diverge more widely (see the plan).

Thus we may regard the southern boundary of the useful area of the ore-bearing tract of the Shishkins as known with sufficient accuracy.

On the eastern side the deposit is bounded by a granite ridge: in boreholes Nos. 39, 32, 42, and 43 granite was encountered; the boundary of the manganese bed extends in a serpentine line from N to S. Since outcrops of granites have been found at Riechiitsa, it is possible, theoretically, to reconstruct here also the limit of distribution of the manganese-ore bed (eroded) on the basis of the following consideration: the bed lies below the mean water level in the Dnieper by plus or minus 3 sazhen. The dip of the granites is approximately \(1^{1/2} : 1000\), according to the exploration data. Thus the boundary at the level corresponding to the eroded manganese bed lies west of the outcrops at a distance of 500 meters (Drawing No. 3).

In the part near the bank of the Riechiitsa, the line of contact of the granites with the manganese is shown partly as a continuous, partly as a dotted line, in general parallel to the direction of the axis of the ridge. The thickness of the bed in the northern and middle parts of the bed is about 1.95 meters, in the southern 1.35 meters. Since the former contains about 189,000 sq. meters of area, the reserve is therefore determined by the figure 3,685,000 cubic meters. The southern part contains about 500,000 sq. meters; hence its reserve is 675,000 cubic meters. In all, 4,360,000 cubic meters. To determine the quality of the ore, we had the ready shaft of Miklashevsky in the Otchenashevskaya ravine, from which extraction was carried out for a bulk sample. In addition, Nos. II and III were also driven at the western boundary, from which ore was obtained for samples. As regards shafts Nos. IV and V, marked on the plan, they were not brought to completion: No. IV because of lack of time, and No. V because of the difficulty of driving through quicksands. The ore proved to be quite good-quality, but in type it differs rather sharply from that of Gorodishche. Namely, its grains are much larger, harder, and more brown in color. According to analysis it contains not only \(\mathrm{MnO_2}\), but also \(\mathrm{Mn_3O_4}\), \(\mathrm{MnO}\), which ultimately remained unexplored. In respect of percentage yield it is not inferior to the Gorodishche and Trubchaninov ores.

Estate of Nevelina

Our exploration works on this estate were limited to determining the southeastern boundary of the distribution of manganese ore

by means of boreholes Nos. 35, 36, which determined the granite. The ore-bearing area of this estate is generally insignificant; on the north it is bounded by the boundary of the Trubchaninovs, on the south-west by the washout valley of the Tomakovka River, on the south by the railway right-of-way, and on the south-east and east by a granite ridge, to which all the uplifts of the ore deposit adjoin. The shape of the ore-bearing area is, in appearance, approximately a trapezoid; it contains about 42,000 sq. meters. We may judge the thickness of the manganese bed in this tract from boreholes sunk along the northern boundary of the Trubchaninovs, namely Nos. 6, 38, and 40, which give an average of 2.34 meters; consequently there are here, in round numbers, 98,000 cubic meters of ore. As to the quality of the ore, we are able to judge from the stockpile that existed in this tract, extracted from a mine located in the middle of the ore-bearing tract. In character and general type it is not distinguishable from the Gorodishche ore, although it is somewhat poorer.

Lands of the village of Gorodishche.

The ore deposit of Gorodishche was described by Sokolov; since, however, mining operations have since then been expanded and some prospecting has been carried out, I must say a few words about this deposit.

Thus, the part now being worked, which forms the northern end of the general Shishkino–Trubchaninov–Gorodishche deposit, will soon be completely worked out. But this part does not constitute the only ore-bearing place on the lands of Gorodishche. Ore has been found by Boikovsky’s boreholes on the western side of B. Kamenka. In addition, ore was found in several shafts laid to the west of the present mine by mining engineer Voinevich. In view of this, the tract described may be considered ore-bearing, irrespective of whether this deposit constitutes a continuation of the Krasnogrigorievka deposit or not. If one singles out the tract bounded on the west by the Krasnogrigorievka boundary, on the south by the washout of the enormous liman in which the Tomakovka and B. Kamenka streams join, this boundary being approximately indicated by the relief of the locality, and finally, on the north-east, assumes granites in a direction from SE to NW, the beginning of which is indicated by Voinevich’s prospecting shafts, then an area of considerable size will result, which, taking into account even the most unexpected deviations of the granites, must nevertheless contain a respectable reserve of ore.

However, besides the depth of the present occurrence, the entire factor determining the character of the ore is, so to speak, the geographical position of the investigated part of the deposit: the farther south it is, the more braunite-like its grains become, despite all possible fluctuations in the depth of occurrence. Thus, in shaft No. I, at a depth of 42 m, the ore more closely resembles that of Gorodishche than in shaft No. III, at a depth of 36 m. Of course, one may suppose here that the change in the relief of the surface occurred relatively recently, that formerly at No. III there lay a thicker layer of rocks.... however, such an explanation is rather arbitrary.

Thus, without entirely denying the possibility of the action of oxygen-bearing atmospheric waters upon the ore deposited in the form of $\mathrm{Mn_3O_4}$, owing to which it could pass into the more stable manganese compound $\mathrm{MnO_2}$, we shall seek the principal cause of complete and partial metamorphization in the conditions of its occurrence in the sea in which it was formed. And so, on shallower, coastal horizons, seawater containing more oxygen could, during the very process of deposition of the manganese ore, exert an oxidizing action more strongly than in a deeper zone farther from the shore. Moreover, the fact of a certain general wedging-out of the ore in the southern direction, as well as the circumstance that the ore is underlain in the southern areas by a thicker layer of clays and sands than in the northern areas, suggests that the ore was deposited during a positive movement of the sea floor (uplift). If so, then the ore of the southern regions is younger than that of the northern ones, since in this case the ore bed was formed by gradually retreating from the shore as the sea became shallower owing to uplift of the bottom and its being covered with sand and silt. This conclusion follows directly from the fact that formations conditioned by the life of microorganisms are, by their origin, strictly confined to the marine horizon of the life of these microorganisms*). We shall return to the discussion of this question.

Some general conclusions.

In a general geological respect, the explorations could not and did not yield much that was new. Here is the small number of facts and considerations that I can share:

Thus, 1) the Pontic stage is distributed over all elevated places of the locality described. In petrographic res—

*) See Sokolov.

...in composition it may be called limestone, since this rock, in the most varied varieties, constitutes the principal mass of the stage; the green-gray interbeds of clay are subordinate to it. The limestone beds do not maintain the same character over any great distance; they wedge out, pass into other varieties, and also into clays. 2) The Sarmatian stage consists chiefly of clays of the most varied properties and colored in every possible color: gray, green, blue, and even black. Limestones occur in this stage in the form of short and thin interbeds, and also in the form of separate, sometimes very hard boulders of crystalline structure. The upper part of the stage consists of short beds of clays, rapidly replacing one another or imperceptibly passing one into another or into sand. Thus, for example, blue clays pass into green and black ones. The lower part, consisting of pure or clayey sand, is a bed having enormous extent, so that it may be considered a characteristic member of this stage. 3) The bed of green clays that almost everywhere covers the manganese ore, assigned by Sokolov, on the basis of stratigraphic data, conditionally to the Sarmatian stage, since no paleontological remains have been found in it, must, in my view, be regarded as a transitional member: its lower part is of Oligocene age, its upper part transitional; there is no sharply expressed boundary between the Sarmatian and Oligocene stages. Sokolov does not indicate precisely the stratigraphic relations on the basis of which the green clays were assigned by him to the Sarmatian stage, except perhaps the fact that they sometimes penetrate into the irregularities of the manganese bed, which Sokolov explains by erosion and subsequent deposition. Since I have not been able to observe facts of this kind, I think that they are exceptions and may be explained by factors acting in the Oligocene sea itself, for example, by coastal currents. I have more than once had difficulty in determining the end of the blue-green, conditionally Sarmatian clays and the beginning of the green supra-manganese clays. On the other hand, the lower parts of these clays are closely connected with the manganese bed; in them occur lumps of limestone resembling those present in the manganese ore and in the green clay underlying it. Moreover, the thin layer of brown clays accompanying the manganese bed should be considered not an independent bed, but simply a part of the green clays, colored brown by manganiferous matter. Everywhere that manganese is absent, the brown interbed is also absent. The lower part of the green clays is rich in many places in detrital quartz grains, exactly like those...

are found in the sub-manganese “apple-green” clay. In color, as well as in other properties, the lower and upper green clays are indistinguishable. In cases where the manganese bed pinches out, it is usually impossible to know whether we are dealing with supra-manganese or sub-manganese clays until their position relative to the granites is determined.

I believe that the lower parts of the green clays, the manganese bed, and the apple-green clays lying beneath it are contemporaneous formations, so that the clayey substance of the bed is nothing other than the same clays, colored by a large quantity of \(MnO_2\). The manganese bed seems to split the green clays and is in very close connection with them.

As regards the structure of the manganese deposit itself, I can say the following: there is reason to suppose a close connection between the longitudinal folding of the South-Russian ancient crystalline massif and the structure of the Nikopol–Gorodishche district of manganese ores, just as this has been done with respect to the Krivoy Rog red-iron-ore deposits.

According to Sokolov’s theory, by which the manganese minerals were formed at a certain, strictly defined horizon of the sea, their deposits must be closely dependent on the structure of the sea floor—that is, of the sea floor in the Oligocene period. Since the sea floor, like the continent at that time, was not covered by any formations, then in a vertical section perpendicular to the folds, whose axes are directed along the meridians, and consequently in a section along a geographic parallel, the surface of the floor gives an undulating line. Any horizontal plane intersects these folds along elongated ellipsoid-like lines, which, when combined, give us a somewhat sinuous line, in view of the fact that the surface of the granite massif has, at least in the part under consideration by us, a general dip from \(N\) to \(S\). The scheme of the deposits is obtained from the incision of the submerged surface of the granites by two horizontal planes corresponding to the minimum and maximum depths at which the manganese minerals could accumulate (see drawing No. 4).

According to the opinion expressed, it must be assumed that: 1) the thickness of the bed in the direction from north to south should generally decrease. This is observed in fact: the average thickness at the Gorodishche mine is 2.80 meters, at Trubchaninovsky 2.20 meters, in the northern part of Shishkin’s 1.70 meters, and in the southern part, at the boundary with the village of Maryevka, it decreases to 1.20 meters. 2) At a certain distance from the boundary with the granites, the thickness should reach its Max., so that

as near the ridges everywhere there must be depths corresponding to the most favorable horizon for the accumulation of manganese. In Voznesenie this is confirmed by a whole series of boreholes and by the Otchenashevskaya mine, in which the thickness of the manganese bed is 3.00 (meters; see the plan).

3) Let us turn to Sokolov’s “Map of the Distribution of Manganese Ores,” leaving aside the environs of Krivoi Rog, little studied with respect to manganese deposits and unfamiliar to me. We see a successive alternation of manganese deposits and granite ridges: a ridge of granites west of the Solenaya River, and east of it a manganese bed. At the Chertomlyk River, in the southern part of its course, granites appear, and farther east again manganese. This deposit is separated from the Krasnogrigorievskaya deposit by a ridge washed by the Malaya Kamenka ravine, with outcrops of granites. Again, between Krasnogrigorievka and Gorodishche there is a small ridge, past which the Bolshaya Kamenka River flows. The end of this ridge is known; it is located at the miners’ residential colony; somewhat to the south, manganese was found in a well, so that at this point there exists a connection between the Krasnogrigorievskaya and Gorodishchenskaya deposits.

The common bed of the Gorodishchensky mine, the western part of the Trubchaninovs’ property, the Shishkins’ estate, and the village of Marievka is separated from the Nikolaevskaya deposit, the eastern part of the Trubchaninovs’ property, from the deposit explored at the Ilins’, Shponka’s, and in the village of Grushevka, by a granite ridge, the western edge of which has been traced by exploration as far as Rechishche.

Of course, I have not indicated all the ridges; besides those marked by granite outcrops, there may be others still unknown to us.

According to the communication of civil engineer Miklashevsky, at Shponka’s there is only a very narrow strip of manganese ore, several tens of sazhens wide, which corresponds to the middle part of the deposit according to the scheme. Farther east no exploration was carried out, so that nothing positive can be said here about the structure of the deposits. It goes without saying that, in applying the general theory to reality, secondary factors must also be taken into account. Thus the magnitude of the folded ridges is in general not the same; then, even before the deposition of manganese, they were subjected to weathering and erosion, all of which is reflected in the outline of the boundaries of the deposit.

No less weighty a factor is the most recent and diluvial fluvial erosion. Since the rivers and ravines of this region flow between the granite folds along them, the relief of the locality may to some extent serve as an indication of the location of the manganese bed; I say “to some extent” because elevations do not always correspond to ridges, while stream valleys at times

intersect the ridges perpendicularly to their axes; the largest example of this phenomenon is the course of the Dnieper from the village of Belenkovo to the town of Nikopol.

In any case, the ore-bearing areas known at present have been discovered chiefly thanks to the proximity of the Dnieper—that is, thanks to the irregularities of the surface caused by its tributaries. Thus, for future exploration and prospecting there still remains a large field ahead. The reserve of manganese ores must for the present be regarded as an undetermined quantity, but in any case as much greater than is known at present.

Plate to the article by S. D. Dobrotvorsky, “Manganese Deposit.”

Drawing 1

Labels visible in the section:

• [[unclear: upper bed label]]
• [[unclear: middle bed label]]
• Underlying clay

Drawing 2

Labels visible in the section:

• Chernozem
• Clayey tier
• Limestone tier
• Ore tier
• Underlying rocks
• [[unclear: label at left margin]]
• [[unclear: label in the lower part of the section]]

Legend:

• Clayey tier
• Limestone tier
• Ore tier
• Underlying rocks
• Clayey sands

Drawing 3

Labels visible in the section:

• Chernozem
• Ore deposit on the surface
• [[unclear: lower bed label]]

Drawing 4

Plan

Letters and section lines marked on the plan:

• a
• b
• c
• d
• e
• f

Captions beneath the plan:

• Sections along ab
• along cd
• along ef

“Deposits of Manganese Ore” by S. F. Dobrokhotov.

[[map/plan page; no prose body text visible]]

Visible map labels include:

• Zhel. Nikolayevka
• Bobrov
• Mukhov
• Sof. Mokranets
• Petrikovskii
• Kutrova
• Vladimirov
• Novotroitskoye
• Estate of Mikhailovka (Osadchikov)
• Shirokaya
• Shirokaya gully
• Belyaev’s gully
• Klinovskii
• Chernyavka
• Manganese
• Usadba
• Khutornaya
• Tsymbalev
• Lisitsa
• Nikolskoye
• Dolgintsevka
• Malakhovo
• Ryabova
• ch. Tikho— [[unclear: remainder of label]]
• South Russian Association of Manganese Ores [[unclear: exact wording]]
• Village of [[unclear: Mokranets?]]
• Estate of [[unclear: Alekseyevka?]]

Numerous plot numbers, boundary lines, pits/shafts, and survey marks are shown throughout the map.

Conventional Symbols

• Boundary of the mining allotment with a plan.
• Boundary of the manganese deposit.
• Boundary of exploratory workings.
• Outcrop of limestones at the surface.

Visible Map Inscriptions

• Mine of Dmitrii “Rotmistrov.”
• I.
• II.
• V.
• [[unclear: handwritten/rotated locality label near the center of the map]]
• 450
• 440
• 430
• 420
• 410
• 150
• 970
• 980
• 990
• 1000
• 500
• 510