Some Regularities in the Distribution of Sulfide Mineralization in the Kolyvan-Tomsk Fold Zone

P. N. Parshin

(Presented by the scientific seminar of the Department of Hydrogeology and Engineering Geology and the Problem Geological Laboratory)

The Hercynides of the Kolyvan-Tomsk fold zone belong to semi-covered geological structures. This circumstance, along with the poor geological study of the region, has led to the currently very limited and vague ideas about its metallogeny. Despite the considerable number (more than one hundred) of ore occurrences recorded by various researchers at different times within the region, there is still not a single explored deposit here. However, the prospects of the Kolyvan-Tomsk fold zone for various types of mineralization, and primarily sulfide mineralization, to which attention in general terms was drawn by I. V. Derbikov (1957), M. M. Konstantinov (1962), and others, remain very positive. This is also indicated by hydrogeochemical investigations carried out within the described region by the Tomsk Polytechnic Institute and already partly published (Udodov, Matusevich, Grigoriev, 1965, and other earlier works).

The results of regional hydrogeochemical investigations, together with confirmation of the general prospects of the zone with respect to sulfide mineralization, make it possible to identify certain regularities in the distribution of such mineralization.

The structure of the Hercynides of the Kolyvan-Tomsk fold zone includes formations from Lower Devonian (?) to Permian inclusive. Lower–Middle Devonian formations crop out and occur beneath Meso-Cenozoic sediments within geoanticlinal structures (the Bugotak, Mitrofanov, Ordynsk, and Podlomsk geoanticlines) (Matveevskaya, 1956). They are represented by effusives and tuffs of mixed composition (the spilite-keratophyre formation), with interbeds of sandy-shaly and carbonate sediments, and are known under ...

called the Bugotak suite in the central and southern parts of the region and the Omutninsk suite (formation) in the northern part. Their thickness is on the order of two kilometers.

Above them, with a hiatus and locally with angular unconformity, occur sandy-shaly formations of the Upper (and locally the upper Middle) Devonian and Lower Carboniferous, with a total thickness of about 3–5 km. The Devonian formations are divided into the Pachinskaya ($D_{2-3}$) and Yurginskaya ($D_3$) suites and contain several clearly lithologically expressed pyroclastic (Mitrofanovskaya $D_{2-3}$, Baranovskaya—$D_3^2$) and reefogenic (Yashkinskaya $D_{2-3}$, Iskitimskaya $D_3^1$) members, which usually have only local distribution. The Lower Carboniferous deposits, developed mainly in the area of the main Hercynian geosynclinal trough, have a sandy-clayey composition with rare thin interbeds of carbonate rocks. Their subdivision into suites has so far been possible only for the Viséan stage in the northern part of the region, where they are known as the Lagernosadskaya, Basandaiskaya, and Kolarovskaya suites (Ivanov, 1956).

Stratigraphically above, with unconformity and a basal conglomerate, lies the molasse coal-bearing formation $C_1—P_1$ (Ostrogskaya and Lower Balakhon suites), which has a very limited areal development in the region only within the frontal and transverse troughs of the Kolyvan–Tomsk Hercynian geosyncline (the Tashminsky, Kuznetsky, and Gorlovsky troughs), that is, essentially beyond the Kolyvan–Tomsk fold zone proper.

During the Late Hercynian phase of tectogenesis the Paleozoic formations were rather unevenly folded, for the most part into gentle folds of a general northeastern strike, and were cut by faults. In the area of the Novosibirsk Ob region, at this time there evidently occurred the most intensive formation of granitoid massifs, accompanied by hydrothermal alteration and sulfide mineralization of the intruding formations. The duration of the formation of granitoid bodies in the Kolyvan–Tomsk fold zone should probably be regarded as considerably greater than is now accepted (as Upper Paleozoic).

Thus, even according to the earliest data, if the age of the clay shales surrounding the massifs was usually defined as Paleozoic (Silurian according to Chersky, 1885; Devonian according to Petz, 1896, and Derzhavin, 1898), then the age of the magmatic formations of the region was interpreted within very broad limits. One of the first investigators of the area, I. D. Chersky (1885), near the village of Dubrovino on the Ob River, notes granite and gneiss, assigning them to the Archean. G. G. Petz (1896) held the same opinion about the age of these rocks. I. I. Bill’ (1895) comes to the conclusion that “the granite is apparently younger than the shale, because in places it cuts the latter as veins with selvages of altered shale; in one place a rather large fragment of shale is observed, surrounded on all sides by a mass of granite.” This position is also confirmed by all subsequent investigators of the region. The age of the granites of the Novosibirsk area came to be considered Late Hercynian. However, consideration of the possibility of a prolonged stage in the development of granitoids has been omitted. And in this there may be a certain value in considering the above-cited views of the first investigators of our area.

In the final stages of folding and faulting of the Paleozoic rocks, along transverse fractures there occurred intrusions of numerous dikes of diabases, monzonites, and dolerites, evidently accompanied by a minor introduction of lead, copper, and some other metals.

The dike formations attained their greatest development in areas of increased stress and metamorphism of the Paleozoic rocks of the os-

trough, in particular in the area of the village of Ordynskoye, the city of Novosibirsk, and especially the city of Tomsk. Their relationship with granitoid formations is complex. In a ditch near the Borok quarry, B. M. Levashov and I were able to observe how a diabase dike cuts granite and at the same time is itself cut by an aplite vein. This may indicate that some varieties of granitoids and diabase dikes are close in age. The latter probably came from deeper horizons and broke through solidifying granite massifs; moreover, as E. P. Izokh (1958) points out, channels in the solidifying granites “simultaneously serve as conduits both for deeper basic masses and for higher-temperature hydrotherms, with which the frequent spatial coincidence of the localization of these dikes and sulfides is connected.”

The area of granitoid development in the Novosibirsk Ob region is characterized by the development of rare-metal mineralization and may, with more detailed geological investigations, be distinguished as an independent rare-metal “ore belt,” in contrast to the polymetallic belt distinguished in the area of development of the Bugotak–Mitrofanovo geoanticlinal zone (Derbikov, 1957; Nuvar’eva, 1964). They are separated by a belt of development of flyschoid Upper Devonian–Lower Carboniferous formations, to the characterization of which we shall return somewhat below.

Within the Kolyvan–Tomsk fold zone, more than one hundred occurrences of nonferrous-metal ores are now known. Most of them are located in the area of development of the effusive-sedimentary Bugotak suite and its analogues and are predominantly polymetallic in character.

Such are the ore occurrences in the northeastern part of the Kolyvan–Tomsk fold zone: Omutninskoye on the Omutnaya River near the village of Omutnaya (with lead, copper, and zinc contents up to 0.3%), Lespromkhozovskoye on the Shcherbak River (lead, copper, and zinc contents also up to 0.3%), and Ivanovskoye on the Kuerbak River.

In the middle part of the Mitrofanovo geoanticline, polymetallic ore occurrences are known along the banks of the Tom River and its tributaries in the area of the village of Mitrofanovo. On the western flank of the geoanticline, along the Iskitimka and Nikolskaya rivers, occurrences of lead and zinc are known. In the headwaters of the Vlaskovo River, at the known Baranovskoye ore occurrence, in 1964 the first hydrothermal-metasomatic polymetallic deposit of disseminated type for the Kolyvan–Tomsk fold zone—the Baranovskoye deposit—was discovered, with maximum lead content up to 3.16%, zinc up to 3.60%, copper up to 0.1%, and gold in the oxidation zone up to 3 g/t (there are as yet no data on the quantitative content of gold in the primary sulfide ores).

The deposit is confined to the faunistically characterized Upper Devonian Baranovskaya tuffaceous-sedimentary member, evidently belonging to the upper horizons of the Yurga suite. The member forms a flexural fold with westward dips of 40 to 80°, complicated by a latitudinal and a series of meridional faults, with the formation of a crushing zone of isometric shape measuring approximately 1 × 1 km. The rocks of the crushing zone are intensely silicified, albitized, and chloritized. The sequence of hydrothermal alterations and ore occurrences for the deposit has not yet been established. Exploration of the deposit has been planned since 1968.

Many small polymetallic ore occurrences are known in the area of the Bugotak anticline. The principal ones are Mikhailovskoye, Permskoye, Ust-Kamenskoye, and one in the Koen–Talmenka interfluve, 6 km south of the village of Koen. In albitophyres near the village of V-Koen, an occurrence of chalcopyrite and malachite is known.

In the area of the main geosynclinal trough, in the southern part of the region, occurrences of copper and lead are known in the Lushnikovo-Boltovsk (the Suzun anticline, composed of effusive-sedimentary rocks of the Frasnian stage), Karakan (the Karakan anticline), and Kamen (the town of Kamen-on-Ob) areas. Several old workings are known here. Thus, according to archival data, at the Kuznetsovo working on the Karakan River, 2.7 km downstream from the village of Sharchino, the copper content in 1 pud of ore was up to 15 pounds (37.5%), and 5 km south of the village of Sharchino—up to 12 pounds of copper per pud of ore (30.63%) (Maksimov, 1950).

In the area of the town of Kamen-on-Ob, the old Tychinsky and Kalbinsky workings are known; they were examined in 1957 by E. I. Evdokimov and contain chalcopyrite, pale ores, malachite, and azurite in quartz veinlets up to 0.8 m thick.

In the area of the city of Novosibirsk, polymetallic ore occurrences are known in granitoid intrusions (often together with rare-metal ore occurrences), as well as on the eastern periphery: along the Izdrevaya River (at the mouth of the Izdrevaya River and near the villages of Gusiny Brod and Zherebtsovo), in the area of the Koinikha River (the villages of Evsino and Shibkovo), and also along the right tributaries of the Tom River: the Tugoyakovka, Sosnovka, and Basandaika. Most of the polymetallic ore occurrences in the clay shales of the Upper Devonian and Lower Carboniferous (especially in the area of the Karakan and Koinikha rivers) tend toward the Yurginskaya Formation of the Famennian stage.

If this brief list of ore occurrences is systematized, we can see that the principal number of nonferrous-metal occurrences falls within the geoanticlinal zone. However, the data of hydrogeochemical studies do not make it possible to give preference to the geoanticlinal zone, and especially to its central part. Dispersion streams of the zones of polymetallic mineralization appear here only on the western flanks of this zone. This makes it possible to draw a negative conclusion regarding the prospects of the central part of the Bugotak-Mitrofanovo geoanticline, to which Yu. A. Nuvar’eva (1964) pointed. It may be assumed that the rather numerous ore occurrences here are due to greater study and are connected with the lower parts of predominantly eroded zones of mineralization. Many hydrogeochemical anomalies of polymetallic and antimony-mercury complexes are spatially located in the zone of the main trough (according to Matveevskaya, 1956), between the geoanticlinal “polymetallic” and Priob “rare-metal” zones, which may indirectly indicate the manifestation here of an independent zone of polymetallic and antimony-mercury mineralization. Some of them are also confirmed by data on the metallometry of rocks.

Moreover, a definite structural and stratigraphic control of mineralization is observed. Structural-sulfide mineralization is confined to zones of crushing in Paleozoic formations affected by hydrothermal solutions, but the most intense mineralization is manifested at intersections of crushing zones of submeridional and sublatitudinal strike. The well-known Semiluzhenskoye antimony mineralization has such a tectonic position. The host rocks are sandy-clayey and carbonaceous-clayey shales of C₁. Occurrences of known polymetallic mineralization (Baranovskoye, Mitrofanovskoye, the Izdrevaya group, Shibkovskoye on the Karakan River, Lushnikovo-Boltovskoye) are found in the same structural-tectonic conditions, but the host rocks are usually either clastic (sandstones, siltstones) or volcanogenic formations. A fairly clear stratigraphic correlation of the host rocks of these ore occurrences is emerging. The rocks of the Mitrofanovskoye ore occurrence (the Mitrofanovo member of pa-

of the Chin suite \(D_{2-3}\)) and Boltovo (?) (Ukrop suite \(D_3^1\)), while the remaining ones listed above belong to the Yurgin suite; moreover, the most studied of them, and the one of definite industrial interest—Baranovskoye—belongs to the Baranovka volcanogenic-sedimentary member of the Yurgin suite, characterized by fauna resembling the fauna of the sulfide-bearing beds of Kazakhstan. Within the Shibkovo ore occurrence we collected fauna from four localities which, according to L. N. Kraevskaya, likewise indicates the Famennian age of each of the four collection points. The most characteristic for these points are Mezoplica ex. gr. proelonga (Hall.) and Cyrtospirifer tschernyschevi Khal f. Also characteristic is the great similarity of the Famennian fauna of the indicated points to the fauna from the Famennian deposits of Kazakhstan, to which, according to A. V. Orlova et al. (1964), the stratigraphic association of lead-zinc mineralization is also traced. Within the development of such rocks, geological prospecting should therefore be carried out first of all to identify sulfide deposits.

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