Proceedings of the Tomsk Order of the October Revolution and Order of the Red Banner of Labor Polytechnic Institute named after S. M. Kirov

Volume 236　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1976

QUARTZOLITES OF THE SOUTHERN KUZNETSK ALATAU (MOUNTAIN SHORIA)

V. A. SARAEV

(Presented by the scientific seminar of the Department of Petrography, TPI)

The term “quartzolites” was first used by Kaye in 1929. According to Kaye [2], quartzolites are quartz rocks formed by the silicification of limestones.

According to A. N. Aleshkov (1935), quartzolites consist predominantly of quartz with the presence of feldspars, sericite, and admixtures: mica, chlorite, epidote, etc. They occur in the form of dikes, stocks, laccoliths, and other bodies characteristic of intrusive rocks.

A. F. Korzhinskii (1967) calls quartzolites essentially quartz rocks formed in zones of rock brecciation and near fractures as a result of intensive leaching of bases and replacement of other minerals by silica.

As can be seen, by the term “quartzolites” the authors designate rocks of essentially quartz composition, formed as a result of hydrothermal metamorphism.

The author of the present article proposes to establish the name “quartzolites” as a term denoting a quite definite subgroup of siliceous rocks [4], and gives them the following definition.

Quartzolites are hydrothermal-metasomatic rocks of essentially quartz composition, formed in tectonic zones and zones of near-ore metasomatism, in the contact parts of intrusions, at the expense of rocks of various, but chiefly carbonate, composition.

Quartzolites are widely distributed in Mountain Shoria. The author distinguishes the following geological-genetic types: 1) quartzolites in skarn zones; 2) quartzolites in the contact aureoles of intrusions, chiefly of granitoid composition; 3) quartzolites in tectonic zones at the contacts of volcanites with carbonate rocks of Riphean-Cambrian age; 4) quartzolites in tectonic zones at the expense of carbonate rocks; 5) quartzolites in tectonic zones at the expense of silicate rocks.

Quartzolites of types 2, 3, and 4 have the greatest development, being distributed in the Biya and Shoria carbonate massifs. Quartzolites of the first type are known in skarn fields developed within the Tashelga-Kondoma mobile zone.

As can be seen, quartzolites develop in various geological settings. Especially favorable for the formation of quartzolites were those conditions where Riphean-Cambrian, essentially carbonate folds occurred, intruded by the massifs of the Lebed tonalite-granodio-

...of the rhyolite–plagiogranite complex \((Cm_{2-3})\), and broken by tectonic disturbances of various character.

The form of the quartzolite bodies is highly varied: from veins and lenses to stock-like and bed-like deposits, linearly elongated along faults. The thickness of the bodies ranges from tens of centimeters to 100 m and more; their length along strike ranges from several hundreds of meters to the first kilometers.

On the basis of structural-textural features, the author divides the quartzolites into the following types: 1) fine-grained, with preservation of the structural-textural features of the replaced rocks and with quartz grain size of 0.01–0.1 mm; 2) medium-grained, with relicts of the structural-textural features of the replaced rocks (0.1–1.0 mm); 3) coarse-crystalline, without relicts of the original rocks \((>1.0\) mm). The specific gravity of the quartzolites varies within the range 2.46–2.64.

1. Fine-grained quartzolites are the most widespread rocks of this subgroup. Their coloration is highly varied, but dark-gray tones with greenish and pinkish shades predominate. The texture is massive, spotted (expressed in the different coloration of individual parts of the rock), banded, and schistose. Under the microscope, depending on the replaced rock, different structures are observed. Quartzo­lites formed at the expense of effusive rocks have porphyroblastic, apointersertal, fluidal, and other structures. Quartz rocks after intrusive rocks have granoblastic, apohypidiomorphic-granular, and other structures. In quartzolites formed after dolomites, beautifully preserved rhomboid sections of dolomite are observed.

Mineralogical composition: quartz ~95%; among impurities there occur calcite, dolomite, biotite, sericite, chlorite, prismatic amphibole, graphite, hematite, and pyrite. Accessory minerals are apatite, leucoxene, zircon, and magnetite.

Quartz forms isometric grains of irregular, amoeboid form with serrated sutures of intergrowth. The degree of idiomorphism of quartz grains differs little from the degree of idiomorphism of quartz siltstones (microquartzites). In the quartz grains there is often observed the finest dust of carbonaceous or ore material.

1. Medium-grained quartzolites are a widely distributed type of quartz rocks. A characteristic feature of these quartzolites is their inequigranular structure. Grain sizes range within 0.1–1.0 mm, but the most common are 0.1–0.3 mm. Under the microscope a granoblastic structure is observed, with relicts of the structural-textural features of the original rocks. Mineralogical composition: quartz ~95%; impurities—muscovite, dolomite, calcite, garnets, diopside, epidote, graphite, hematite, pyrite. Accessory minerals are apatite, zircon, leucoxene, magnetite, rutile. Sometimes carbonates and skarn minerals form veinlet-like accumulations (Chulesh-Labysh area). Quartz forms isometric, polygonal, prismatic grains with straight, more rarely serrated, sutures of intergrowth.

2. Coarse-crystalline quartzolites are white and light-gray rocks with various shades of weak intensity. The texture is massive. They are closely associated with medium-grained quartzolites, forming nests and lenses among them. These formations are characterized by inequigranular structure, an almost monomineralic composition, and a high degree of idiomorphism of quartz. Impurities in quartz crystals are, as a rule, absent. In addition to quartz, rare inclusions of carbonates, muscovite, biotite, and pyrite are observed in the quartzolites. Geodes with translucent quartz crystals up to 10 mm long are often observed in the rocks. The sizes of the geodes are 10–40 mm. Their development is characteristic of quartzolites formed at the expense of carbonate rocks (the “Belka” area).

The most typical chemical composition of quartzolites is as follows:
SiO$_2$—97.12%; TiO$_2$—0.06%; Al$_2$O$_3$—0.71%; Fe$_2$O$_3$—0.04%; FeO—1.19%; MnO—0.06%; MgO—0.25%; CaO—0.27%; Na$_2$O—0.03%; K$_2$O—0.08%; P$_2$O$_5$—absent; CO$_2$—0.14%; S—absent; loss on ignition—0.13%; total—100.15%. Owing to an increase in mineral impurities, the amount of silica varies in individual areas within the range of 80–98%, but the overwhelming majority of samples show a silica content of 96–98%.

In conclusion, it is necessary to dwell on several general additional features of quartzolites. In addition to what has been noted above, all quartzolites are characterized by a manifested porosity, even a cavernous texture, as well as by limonitization. The porosity and limonitization of quartzolites are caused by the weathering and leaching of calcite, dolomite, and sulfides.

In certain areas of Mountain Shoria, quartzolites contain gold-sulfide and polymetallic mineralization. A certain spatial relationship is noted between them and talc schists (the Svetlo-Klyuchevskoye talc deposit).

The high thermal conductivity and brittleness of quartzolites facilitate the circulation of hydrothermal solutions within them and the appearance of ore mineralization.

REFERENCES

1. A. N. Aleshkov. Proceedings of Glacial Expeditions. Issue 4, Ural Publishing House of TsUEGMS, 1935.

2. F. Yu. Levinson-Lessing. Petrographic Dictionary. E. A. Struve. Gosgeoltekhizdat, Moscow, 1963.

3. A. F. Korzhinsky. Hydrothermally Altered Rocks of Rare-Metal Deposits of Eastern Siberia. Nauka Publishing House, Moscow, 1967.

4. V. A. Saraev. On the classification of siliceous rocks. In: New Data on the Geology and Geography of Kuzbass and Altai. Novokuznetsk, 1969.