ON THE RELATIONSHIP BETWEEN NICKEL MINERALIZATION AREAS AND THE RIVER NETWORK

A. G. BAKIROV

(Presented by Professor A. M. Kuzmin)

It is generally known that river valleys are often associated with disturbances, various fractures, downwarps, and zones of increased fracturing. In essence, the hydrographic network records the tectonic network of rupture disturbances in the substratum of a given region. These features in the inception of river valleys have attracted the attention of the authors of many textbooks on geology and geomorphology. In the Urals they have been noted by I. I. Krasnov [4], Ya. S. Edelshtein and A. P. Sigov [7, 5], V. A. Aprodov [1], V. P. Trifonov [6], and other researchers.

It is appropriate to recall that young fractured zones, to which rivers adapt themselves, often have an ancient origin of Precambrian or Paleozoic age. These zones were repeatedly renewed over the long history of the geological development of regions. The latest “rejuvenation” of the zones mentioned is usually associated with one or another stage of their neotectonic life.

Hypergene nickel deposits are sometimes associated with long-developing deep faults, disjunctives, and zones of increased fracturing that have influenced the hydrographic network. This is explained mainly by the connection between nickel-bearing hyperbasites and faults, and by the formation of the most substantial weathering crust at the intersections of ultrabasic rock massifs by disjunctives and fractured zones.

In the Urals there are latitudinal structures of diverse forms of manifestation, in the form of hidden faults, downwarps, flexures, folds, disjunctives, and zones of increased fracturing, to which we attach great importance in the localization of various deposits, including hypergene nickel deposits [2, 3].

The latitudinal dislocations that appeared in the Urals in Neogene and Quaternary time were mainly inherited in character. In many cases they emphasized ancient latitudinal structures and influenced the arrangement of the hydrographic network of the Urals. This is evidenced by the numerous latitudinal segments of its young river valleys.

On the basis of the foregoing, the question arises whether there are any connections between the spatial distribution of areas of hypergene nickel mineralization, on the one hand, and the latitudinal elements of the hydrographic network, on the other. Our investigations have shown that such connections exist.

At the same time, they are manifested not only in the Urals, but also in Ukraine, Kazakhstan, and Western Siberia.

We considered it possible to distinguish four forms in which such relationships appear. In the first of them, extended latitudinal segments of river valleys pass through areas where sectors of nickel mineralization are developed. A good example is the Pobuzhye region, dissected by the latitudinal valley of the Southern Bug River. The latitudinal segment of the Irtysh River and the sector of nickel mineralization of the Gornostayevka hyperbasite massif in Kazakhstan are in analogous relationships. Near latitudinal segments of river valleys are found the nickel-bearing sectors of the hyperbasite weathering crusts of the Nikopol district in Ukraine and of the Petrovsky district in the Urals.

The second form of relationship is manifested in the presence of latitudinal segments of river valleys that mark the boundaries of regions of hypergene nickel mineralization. In its classic form, this type of relationship is expressed in the Serov district of the Urals. There the latitudinal valleys of the Turya and Kakva rivers mark the boundaries of a latitudinal tectonic block. Within it there were favorable conditions for the preservation of nickel-bearing sectors of the weathering crust, owing to their confinement to a depression associated with meridional grabens. The hydrographic network outlines the boundaries of nickel-bearing hyperbasites in the Ufaley and Aydyrlinsky districts of the Urals and in other places.

Some latitudinal structures that influenced the formation of nickel-bearing sectors of the weathering crust are marked by clearly expressed loops or sharp bends of river valleys located near these sectors. In classic form, such relationships are expressed in the Urals in the Rezhevsky district near Golendukhino (the loop of the Rezh River). East of the loop of the Dnieper River lies the Slavgorod manifestation of nickel mineralization.

In a number of cases, when sectors of nickel mineralization are confined to latitudinal downwarps or to zones of increased fracturing, latitudinal segments of river valleys serve as distinctive indicators marking the direction toward a deposit or ore occurrence. A good example is the Neiva River, whose latitudinal segment indicates the location of the Anatolsky sector. A similar pattern is observed in the Kempirsay district and other places in the Urals,^1 as well as in the Salair and in Kazakhstan.

REFERENCES

1. V. A. Aprodov. On the river network in the middle part of the western slope of the Urals and the Cis-Urals. Materials on the Geomorphology of the Urals. Issue 1, 1948.

2. A. G. Bakirov. The relationship of ore formations of the Urals with its latitudinal structures. Doklady AN SSSR, vol. 148, No. 5, 1963.

3. A. G. Bakirov. Some structural regularities in the localization of hypergene nickel deposits of the Urals. Izv. TPI, vol. 127, issue 1, 1964.

4. I. I. Krasnov. An attempt to compare geomorphological elements of the Middle and Southern Urals with geological structures. Problems of Physical Geography, vol. XV, 1950.

5. A. P. Sigov. Principal features of the geomorphology of the Urals. Materials on the Geomorphology and Recent Tectonics of the Urals and the Volga Region, vol. 1, 1962.

6. V. P. Trifonov. Recent tectonics of the eastern slope of the Urals and the Trans-Urals. Geomorphology and Recent Tectonics of the Volga-Ural Region and the Southern Urals. Publishing House of the Bashkir Branch of the USSR Academy of Sciences, Ufa, 1960.

7. Ya. S. Edelshteyn, A. P. Sigov. Geomorphological Map of the Urals. Explanatory Note. ONTI, Moscow, 1932.

^1 Segments of some river valleys of the Urals are also “aimed” at endogenous deposits.