ON THE SYSTEMATICS OF HYDROTHERMAL URANIUM DEPOSITS

V. K. Cherepnin

(Presented by Professor A. M. Kuzmin)

The intensive study of uranium deposits carried out over the past one and a half to two decades has placed in the hands of researchers an enormous body of factual material, which often does not fit within the framework of existing classifications. All this has led to fairly numerous attempts to create a rational classification. However, the basic principles for its construction have still not been developed.

In our country, classifications of uranium deposits have been proposed by M. M. Konstantinov [4], I. G. Magak’yan [6], V. S. Domarev [3], D. Ya. Surazhskii [8], V. G. Melkov [7], A. G. Betekhtin [1], V. N. Kotlyar [5], Ya. D. Gotman [2], and other authors.

Abroad, one of the earliest classifications belongs to C. Bain [12]. Later there appeared classifications by A. Lang [14], D. Everhart [11, 13], M. Roubault [15], E. Heinrich [10], and others.

The classifications of Soviet authors, in the overwhelming majority of cases, are constructed on a genetic basis and are often very similar to one another, differing only in the different placement of individual types or even groups of deposits within one class or another. For example, in D. Ya. Surazhskii’s classification the high-temperature hydrothermal davidite formation is assigned to pegmatites. Some authors (A. G. Betekhtin, V. N. Kotlyar) distinguish an independent group of contact-metasomatic (skarn) deposits. Others (V. G. Melkov, A. A. Yakkhin) include them among hydrothermal deposits, while still others (D. Ya. Surazhskii, V. S. Domarev) do not distinguish them at all. Such an important genetic feature as the mode of deposition of material from ore-bearing solutions is reflected differently in the classifications. Some authors (D. Ya. Surazhskii, A. A. Yakkhin, Ya. D. Gotman) divide hydrothermal deposits into vein and metasomatic deposits; others (V. G. Melkov, A. G. Betekhtin, V. N. Kotlyar) do not do this.

Foreign classifications, for the most part, are also built according to a genetic criterion. However, classifications are known that are based not on ore-forming processes, but on the composition of the enclosing rocks. In these classifications we see a reflection of the well-known ideas of Sullivan, who downplayed the role of hydrothermal solutions in the formation of ore deposits. An example of such classifications is precisely the earlier classification of D. Everhart [11], who later modified it, seeking to place at its foundation two features—

Thus, on the one hand, he grouped deposits into genetic groups according to mineral associations; on the other, he subdivided each group into smaller units according to the character of the host rocks.

Even this brief survey shows that among researchers engaged in the systematics of uranium deposits there is no single opinion regarding the very approach to the essence of the problem, not to mention differences in views on the genesis of certain types and even large groups of deposits.

In the present article we would like to dwell on several principles of systematics which, in our opinion, should be taken into account in constructing a classification of hydrothermal deposits—the most widespread and most important group of endogenous uranium deposits.

As the leading classificatory criterion, in our opinion, it is advisable to adopt the temperature of formation of the deposits; in this connection, apparently, the twofold division of the group under consideration that is widespread also among Soviet authors should be retained (high-temperature and medium- and low-temperature deposits).

As the basis for further subdivision, it seems timely to take the depth of formation of the deposits. As is known, studies in recent years throughout the world have revealed a large number of uranium deposits spatially, and possibly also genetically, associated with subvolcanic intrusions, vent facies of extrusions, and effusive formations. All these deposits, characterized by a commonality of features conditioned by their near-surface formation, naturally, in systematics, must in some way be combined and separated from deposits formed under deep-seated conditions. In this connection, in each of the above-mentioned subgroups, in our opinion, deposits of deep-seated and near-surface facies should be distinguished.

It should be noted that the facies principle is at present strongly recommended by many researchers and, in particular, by F. N. Shakhov [9] as the leading classificatory criterion for hydrothermal deposits in general.

Finally, such a very important classificatory criterion as the mode of deposition of the substance cannot but be taken into account; its use ultimately leads to the distinction of vein and metasomatic deposits.

The final members of the systematics should be ore formations distinguished on the basis of the leading mineral associations.

Taking into account all that has been set forth above, the classification of hydrothermal uranium deposits may be presented in the following form:

1. High-temperature deposits

Deposits of deep-seated facies

a) Vein deposits

1. Davidite formation.
2. Molybdenite–uraninite with gold formation.
3. Brannerite formation.

b) Metasomatic deposits

1. Hematite–magnetite–uraninite formation.
2. Formation of uranium-bearing albitites.
3. Copper–uraninite formation.

2. Medium- and Low-Temperature Deposits

Deposits of deep facies:

a) Vein deposits:

1. Pitchblende–sulfide formation.
2. Five-element formation.
3. Pitchblende–carbonate formation.
4. Pitchblende formation.

b) Metasomatic deposits:

1. Sulfide–uranium formation.

Near-surface deposits:

a) Vein deposits

1. Pitchblende–sulfide formation.
2. Sulfide–cassiterite formation with uranium.

b) Metasomatic deposits

1. Formation of uraniferous fluorite.

REFERENCES

1. A. G. Betekhtin. On the behavior of radioactive elements during the processes of formation of endogenous deposits. Geol. rudn. mestorozhd., No. 1, 1959.

2. Ya. D. Gotman, I. N. Gubrev. Genetic classification of uranium deposits. Sov. geolog., No. 3, 1963.

3. V. S. Domarev. Geology of uranium deposits in capitalist countries. Gosgeoltekhizdat, Moscow, 1956.

4. M. M. Konstantinov. Prospecting for uranium ores in foreign countries. Razvedka i okhrana nedr, No. 4, 1955.

5. V. N. Kotlyar. Geology of uranium deposits. Gosgeoltekhizdat, Moscow, 1961.

6. I. G. Magak’yan. Genetic types of foreign uranium deposits. Zapiski Vsesoyuznogo mineralog. obshch., issue 3, 1955.

7. V. G. Melkov, L. Ch. Pukhalskii. Prospecting for uranium deposits. Gosgeoltekhizdat, Moscow, 1957.

8. D. Ya. Surazhskii. Genetic types of industrial uranium deposits. Atomnaya energiya, No. 2, 1956.

9. F. N. Shakhov. Principles of the systematics of endogenous ore deposits. Geologiya i geofizika, No. 10, 1962. Publishing House of the Siberian Branch, Academy of Sciences of the USSR.

10. E. U. Heinrich. Mineralogy and geology of radioactive mineral raw materials. Foreign Literature Publishing House, Moscow, 1962.

11. D. L. Everhart. Vein deposits of uranium in the USA. Geologiya atomnykh syrevykh materialov. Gosgeoltekhizdat, Moscow, 1956.

12. Bain G. W. Geology of the fissionable materials. Econ. geol., 45, No. 4, 1950.

13. Everhart D. L. Origin of uranium deposits, a progress report. Am. Inst. Mining Engrs., Trans., 1954.

14. Lang A. H. Canadian deposits of uranium and thorium. Can. Geol. Survey., Econ. Geol. Ser., 16, 1952.

15. Roubault M. Essai de classification des gisements d’uranium et de thorium. Acad. sci. Paris., Compt. rend., 1955.