PROCEEDINGS
OF THE TOMSK ORDER OF THE RED BANNER OF LABOR POLYTECHNIC
INSTITUTE named after S. M. KIROV

Vol. 166　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1969

ON THE AGE OF THE ORE-HOSTING ROCKS OF THE BARANOVSKOYE POLYMETALLIC MINERALIZATION IN THE KOLYVAN–TOMSK FOLDED ZONE

P. N. PARSHIN, L. N. KRAEVSKAYA

(Submitted by Professor A. M. Kuzmin)

The Baranovskoye polymetallic mineralization is located within the western part of the village of Baranovo, in the upper reaches of the Vlaskovo River, a right tributary of the Pacha River. Earlier investigators (in particular, V. F. Loskutov) regarded the structural position of the area described as an anticline of NNE strike, with exposure at the surface from beneath the sandy-clayey shales of the Pachinskaya Formation ($D_{2-3}$), which overlie the latter effusive-sedimentary formations of the Mitrofanovskaya Formation of Givetian age.

The section along the Vlaskovo River compiled by us in 1963 (Fig. 1) did not confirm the presence of an anticlinal structure in the area of the village of Baranovo. Exposed along its eastern margin (from bottom to top) are gray-colored pyritized dense limestones, gravelites, clayey shales, and green-colored tuffaceous sandstones with nests of pyrite and an increased copper content (outcrop 3); these have a westward dip at an angle of 40°, i.e., they rest normally upon the gray-colored clayey and sandy-clayey shales of the Pachinskaya Formation, developed to the east of this outcrop.

Fig. 1. 1. Limestones $D_{2}^{2}=D_{3}^{1}$. 2. Sandy-clayey shales of the Pachinskaya Formation $D_{2-3}$. 3. Sandstones. 4. Gravelites. 5. Tuffs of acid and mixed composition. 6. Diabase porphyrites of the Baranovskaya Formation $D_{3}^{2}$. 7. Faults. 8. Fauna.

Note: dashed symbols show the presumed distribution of lithological varieties.

From the gravelites we collected a crinoid fauna, identified by Yu. A. Dubatolova as Anthinocrinus ex gr. florens Gelt. | A. florens Yelt.; Hexacrinites (?) ex gr. humilicarinatus Yelt.

Collection of fauna in this exposure is made difficult by the impossibility of obtaining a split of the samples along the bedding, which is disrupted by cleavage at an angle of 30°.

Farther west, over a distance of 600 meters, there are no signs of moraine rocks.

At the western edge of the village of Baranovo an effusive-sedimentary sequence is exposed (outcrop 4), crumpled into a flexural fold complicated by a fault. Here the following are exposed (from bottom to top):

1. Greenish sandy-clayey shales, similar to the upper bed of outcrop 3, passing upward in the section into light-colored silicified siltstones, 10 m.

2. Interbedding of tuff sandstones, tuff conglomerates, albitophyres, and albitized sericite-chlorite shales (the ore-bearing sequence), up to 100 m.

3. Diabase porphyrites, with a six-meter interbed of sandy-clayey shales and tuff sandstones, with abundant poorly preserved fauna and flora. The total thickness of the described sequence is up to 25 m.

Farther west, over a distance of 100 m, outcrops of albitophyres, diabase porphyrites, and occurrences of silicified siltstones with a westerly dip at an angle of 40° are observed; these terminate the tracing of bedrock exposures at the surface.

The fauna collected by us in 1964 from bed 3, according to the determination of L. N. Kraevskaya, contains Schisophoria cf. praeimpressa N. — a core; Cyrtospirifer ex gr. archiaci Murch., part of a core with sculpture; Cyrtospirifer sp., several impressions of large and medium size, similar to C. sulcifer H. C. The latter species, in its typical development, is characteristic of the sulcifer beds of the Famennian in Kazakhstan. Typical representatives of Schysophoria praeimpressa were first established in the Meister beds of the same stage by D. V. Nalivkin. Crinoids determined by Yu. A. Dubatolova are: Pentagonocyclicus sp. 2, Pentagonocyclicus sp. 5. (The age is presumably D₂).

On the basis of these determinations, we define the age of the ore-bearing rocks of the Baranovo polymetallic mineralization as Upper Devonian (possibly even Etrennian).

In light of the data described above, the age range of Devonian formations prospective for polymetallic mineralization in the Kolyvan-Tomsk folded zone is extended up to and including the Famennian stage; previously, in this region, only deposits no younger than the Middle Devonian were considered prospective.

In conclusion, it is necessary to give a brief substantiation of the age of the deposits of the Pachinskaya Formation, which underlie the volcanogenic-sedimentary Baranovo sequence.

In the practice of geological mapping in the territory of the Kolyvan-Tomsk folded zone, it is customary to assign the index D₃ to the Pachinskaya Formation. A. V. Tykhnov (1941), who first distinguished these deposits under the name “Pachinskaya sequence,” considered them to be of the same age; whereas the reefogenic limestones developed in the lower part of the formation (“Yashkino limestone,” according to A. V. Tykhnov) occupy a somewhat indefinite age position in the cited work, although they are described together with formations that are now united into the Pachinskaya Formation.

Within the Yashkino limestone, A. V. Tykhnov describes two varieties. The first consists of light-gray marbleized limestones (in our supposition, their continuation to the south is outcrop 2 of the section presented in this article); the second variety includes darker, likewise marbleized limestones, in whose composition

B. B. Chernyshov, from collections made by L. N. Kraevskaya in 1940, identified: Alveolites mailieuxi Lecompte; A. suborbicularis Lam; Heliolites polymorpha Goldf.; Amphypora sp.; Pachypora sp. Crinoidea. The age is most probably D₂.

The limestones of the second variety south of the village of Burlakovo, according to our data, pass facies-wise into argillaceous shales, from which V. F. Loskutov gives a list of fauna (determinations by Z. F. Pivovarova): Thamnopora nicholsoni Frech; Alveolitella polenovi Petz; Coenites fascicularis Radugin. The age is Givetian.

Thus, the age subdivision of the deposits of the Pacha Formation requires further field investigations. Until such work is carried out, the age of the entire Pacha Formation should be taken as D₂–₃.

REFERENCES

1. A. V. Tyzhnov. Geological description of the northern part of Kuzbass and the problem of its oil-bearing capacity. Vestn. ZSGU, No. 4, 1941.