PROCEEDINGS

of the Tomsk Order of the Red Banner of Labor
Polytechnic Institute named after S. M. Kirov

Volume 135 1965

POSTMAGMATIC ALTERATION OF ROCKS

OF THE DIKE COMPLEX OF THE KOMMUNAROVSKOYE

GOLD ORE FIELD (KHAKASSIA)

A. F. Korobeinikov

(Presented by Professor A. M. Kuzmin)

The Kommunarovskoye ore field, located on the eastern slope of the Kuznetsk Alatau Range near its axial line, is composed of rocks of a diabase-porphyrite and sedimentary-volcanogenic sequence, presumably of Middle Cambrian [15] or even Precambrian [8, 12] age. The rocks of both sequences are assembled into a large anticlinal fold with an axis gradually plunging to the north-northeast, and are intruded by small subconcordant bodies of amphibolized gabbro-diorites and diorites of the most ancient Boi gabbro-diabase intrusive complex [7], by the large Solgonsky granodiorite massif (an intrusion of quartz monzonites according to A. Ya. Bulynnikov [3]), and by small stock- and dike-like bodies of olivine gabbros and gabbro-porphyrites, genetically related, most likely, to the Devonian gabbro-syenite intrusion [9].

The folded structure of the district is complicated by numerous large, steeply dipping faults of submeridional and sublatitudinal trends, creating a block tectonic structure. Most of the disjunctives predate the ore and even the pre-dike emplacement; moreover, the largest of them controlled the distribution of dikes and of gold mineralization.

In the contact aureole of the Solgonsky intrusion, abundant contact-metasomatic and quartz-gold-ore formations are developed, genetically related to the granodiorite intrusion.

The rocks of both sequences, the gabbro-diorites, and the granodiorites are cut by numerous dikes of acid, intermediate, subalkaline, and basic composition. They are situated chiefly within the exocontact zone of the broad aureole of the Solgonsky granodiorite massif, forming in the southern part of the ore field a sublatitudinal dike belt. The petrographic composition and petrochemical and geochemical features of the dike rocks have been considered by us in a separate communication. Here it should only be emphasized that, in petrographic composition and in petrochemical and geochemical features, the dike formations, except for olivine gabbro-porphyrites and teschenites, are genetically related to the granodiorite intrusion. On the basis of the mutual intersections of dike bodies, we have distinguished three major age groups¹:

1. First group—dikes of intermediate composition (diorite porphyries, fine-grained diorites), cutting diorites and granodiorites of the Solgon intrusion. In this case they are intensely hornfelsed. The formation of these dikes is apparently connected with the augite diorites of the first phase of emplacement of the Solgon granodiorite intrusive body²) (Fig. 1, a). Within the ore field, dikes of the first group are rare.

2. Second group—dikes ranging from acidic to basic in composition, comprising the main quantity of all dike formations of the ore field, and evidently connected with the formation of the second, most widely manifested phase of emplacement of the granodiorite intrusion. On the basis of mutual intersections (Fig. 1, b, v, g, z) they are grouped into two age subgroups (in order of their emplacement): a) diorite and labradorite porphyries, monzonites, fine-grained diorites and microdiorites, vogesites, kersantites, spessartites, syenites, syenite porphyries, quartz porphyries; b) pegmatites and aplites. Veins of granite-aplite and hornblende diorite porphyrite often contain xenoliths of granodioritic and dioritic (tonalitic) composition.

Dikes of the first and second age groups are pre-ore.

1. Third group—dikes of olivine gabbro-porphyrites and subalkaline diabase porphyrites (teschenites) are not widespread and are post-ore. They lack quartz–ore mineralization, have a relatively fresh appearance, and are not affected by near-ore alterations, although some of them are situated in zones of intense hydrothermal metamorphism and gold mineralization, and teschenite dikes sometimes cut quartz–gold-ore mineralization.

An interesting circumstance is that the pegmatite and aplite dikes are few in number and are located mainly among the rocks of the Solgon pluton, whereas the other dikes are confined to the country rocks and are more rarely situated in the endocontact zone of the granodiorite massif. As regards the orientation and mode of occurrence of the vein bodies, within the granodiorite massif they tend toward steeply dipping fracture systems of submeridional and northeastern strike and toward gently dipping (bedding-parallel) prototectonic fractures. In the country rocks, steeply dipping dikes of sublatitudinal direction are confined to the tectonic-fracture systems prevailing there.

In general, the confinement of dike and hydrothermal formations to the same systems of tectonic fractures is established (Fig. 2, a, b), which probably indicates the common structural plan of deformations during the period of dike formation and subsequent gold–quartz mineralization.

It should be noted that sufficiently complete studies of the dike formations of the ore field have not been carried out to date, despite the fact that a spatial confinement of some gold-ore occurrences to junctions of large submeridional

²) Within the Kommunarovskoye gold-bearing district, the Solgon granodiorite massif is composed of rocks of three intrusive phases: early—diorite porphyrites, augite diorites, meladiorites and hybrid gabbro-diorites, tonalites; middle—granodiorites, leucodiorites, monzonites; and late—syenites and fine-grained granites. In mineralogical-petrographic composition and petrochemical features, the intrusive formations of the Solgon pluton correlate with the early phase of emplacement of the Ulen-Tuim (Tigertysh) granitoid complex of Upper Cambrian–Lower Ordovician age [6, 7] and with formations of the Martaiga intrusive complex [5], and belong to the mid-depth facies group according to the classification of Yu. A. Kuznetsov [11]. The age of pyroxene-biotite quartz diorites of the Solgon intrusion, determined by the potassium-argon method on biotite in the laboratory of ZSGU, is 476 million years.

Fig. 1. Sketches of the relationships of dikes of different composition and age within the Kommunar ore field: 1 — effusives of basic composition and their tuffs; 2 — sublayered and dike-like bodies of uralitized gabbro-diorites and diorites of the Solgon intrusive complex; 3 — granodiorites and diorites of the Solgon intrusion; 4 — dikes of diorite porphyries and fine-grained diorites of group I; 5 — pegmatites and pegmatoids; 6 — diorite porphyries, lamprophyres; 7 — fine-grained diorites and microdiorites; 8 — diabase porphyrites; 9 — olivine gabbro-porphyrites and gabbro, and zones of endocontact influence of dike bodies; з — summary diagram of the relationships of intrusive bodies and their vein series of different ages; 1 — uralitized diorites and gabbro-diorites are cut by rocks of the first (2) and second (3) phases of emplacement of the Solgon granodiorite intrusion; olivine gabbro and gabbro-porphyrites (4) cut all intrusive formations of the area.

fractures with dikes (D. I. Kallinikov, N. A. Fogelman). Therefore, in the present communication a first attempt is made to consider certain questions concerning the relationships of the dike complex with the contact-metasomatic and gold-ore formations of the district and, in particular, the near-skarn and near-ore alterations in the dike rocks. The resolution of these questions will make it possible to clarify certain aspects of the genetic connection of the gold mineralization with the intrusions of the district.

Fig. 2. a—point diagram of the orientation of dikes of the Kommunarovskoye ore field (poles to dike planes are plotted): 1—dikes of the first age group (diorite porphyrites and fine-grained diorites); 2—dikes of the second group (pegmatoids, aplites, diorite porphyrites, fine-grained diorites, quartz porphyries, lamprophyres, and labradorite porphyrites); 3—syenites and syenite-porphyries; 4—diabase porphyrites and olivine gabbro-porphyrites; 5—dominant structural elements of the rocks enclosing the saddle-effusive sequence; b—point diagram of the orientation of quartz–gold-ore veins and veinlets of the ore field.

Relationships of dike and skarn-metasomatic formations and near-skarn alterations in them

Within the ore field, contact-metasomatic formations are rather widespread and are represented by preskarn, skarn, and postskarn metasomatites. With respect to the dikes of the first two age groups, genetically connected with the Solgonskaya intrusion, all known skarn and postskarn metasomatites belong to post-dike formations and fall into two groups: 1) skarn-metasomatic bodies genetically connected with the emplacement of the granodiorite intrusion, and 2) skarn-metasomatic formations genetically connected with the dike complex (skarnification of dikes of pegmatoids and syenites by their own or later postmagmatic solutions [1]). The formations of the first group of metasomatites are the most widespread and are represented both by typical skarns and by skarn-magnetite lenses, sometimes containing aposkarn gold mineralization [3, 10].

The dikes of the third age group, with respect to the skarn-metasomatic bodies, are crosscutting (postskarn) and have not undergone metasomatic alteration. Metasomatites formed during the emplacement of this group of dikes have not been established.

Skarnization of dike rocks in connection with the formation of skarn-metasomatic lenses is observed rather often, especially in the areas of skarn-magnetite formations of the Southern and Ninth lenses of the Kalyustrovskoye deposit, where dikes of diorite and labradorite porphyries of the second group are not infrequently widespread. In these cases the dikes prove to be, as it were, crosscutting with respect to the metasomatites. At the contact with skarn-magnetite bodies, the diorite and labradorite porphyries are intensely altered, cut by thin (up to 2–7 cm) magnetite veinlets, and impregnated with numerous metacrysts of magnetite. The porphyritic segregations of the dike rocks, represented by plagioclase and augite, are completely replaced by epidote, zoisite, and actinolite. The groundmass of the rock, composed of a fine-grained aggregate of plagioclase and pyroxene, is likewise almost entirely replaced by an actinolite–serpentine aggregate. In addition, diopside–garnet–epidote and serpentine–asbestos veinlets up to 0.1–0.8 cm thick, cutting the dike rocks, are often encountered. As a result of metasomatic processes the diorite and labradorite porphyries acquire a greenish-gray color and become saturated with veinlets and irregular segregations of actinolite with magnetite, pyrite, and chalcopyrite. Sometimes scapolite develops intensively after plagioclase ($No = 1.553$, $Ne = 1.538$, $No - Ne = 0.015$) and serpentine ($Ng = 1.558$, $Np = 1.552$, $Ng - Np = 0.006$, which corresponds to antigorite [14]). In turn, scapolite is replaced by actinolite ($Ng = 1.665$, $Np = 1.645$, $cNg = 14$–$16^\circ$), calcite, pistacite ($Ng = 1.758$–$1.671$, $2V = (-)78$–$80^\circ$), and zoisite. Pyroxene–garnet–epidote thin veinlets are found only directly at the contact of the dike rock with the skarn-magnetite lens and are accompanied by an unevenly disseminated sprinkling of pyroxene and epidote. In optical properties the pyroxene ($Ng = 1.691$–$1.697$, $Np = 1.667$–$1.670$, $2V = 58^\circ$, $cNg = 38^\circ$) belongs to diopside containing up to 3–5% of the ferrisilicate molecule [14] and is analogous to the diopside that is part of the skarn formations proper. The garnet (by specific gravity, equal to 3.77–3.78²) belongs to andradite, containing up to 70% of the andradite molecule [14], is fairly rare, and in composition also corresponds to the garnets of skarn-metasomatic bodies.

According to recalculation of the chemical-analysis data (after Barth, [16]), the material balance during metasomatism of diorite porphyries that underwent skarnization³ is as follows (in ions): introduced: calcium, magnesium—133, hydroxyl—266; removed: potassium—15, sodium—42, divalent iron—16, aluminum—89, silicon—73, phosphorus—5, titanium—2.

Graphically, the material balance is shown in Fig. 3 and Table 1. Thus, the formation of apodike metasomatic rocks is accompanied by a certain mobility of such elements as magnesium, silicon, calcium, iron, alkalis, etc.

As already noted, skarn formations of the second group have been established only in connection with dikes of pegmatoids, consisting of 80–90% andesine No. 37–42, quartz, and muscovite, and with veins of syenites. Thus, at the contact of a pegmatoid vein with acid effusives, thin (up to 0.2–0.3 m) rims and lenses of coarse-grained, locally drusy skarn were observed, developing both in the enclosing effusives and in the dike rock. These skarn bodies are composed of 90% garnet (specific gravity 3.67–3.73), which corresponds to a variety containing

about 60–65% of the andradite molecule [14], more rarely by diopside \((Ng = 1.692—1.696,\ Np = 1.671—1.675),\ Ng - Np = 0.023,\ 2V = 58—59^\circ\), actinolite \((Ng = 1.663—1.667,\ Np = 1.643—1.647,\ Ng - Np = 0.020,\ cNg = 14^\circ;\ 2V = (-)\ 78^\circ,\) i.e., in optical properties it belongs to the variety containing about 50% of the ferro-silicate [14]), albite-oligoclase No. 10–12, and rare quartz.

Table 1

Note: 1—chemical analysis of unaltered diorite porphyrite, Central Laboratory of the Krasnoyarsk Geological Administration; 2—calculation based on data from chemical analyses of individual minerals composing the altered diorite porphyrite (serpentine—25%, diopside—20, garnet—10, chlorite, carbonates, quartz, sphene, epidote—10, relicts of the dike rock—35%).

Rock formula according to Barth:

\[ \begin{aligned} 1.\;& K_{25}\ Na_{68}\ Ca_{60}\ Mg_{33}\ (Fe_{\text{tot}})_{68}\\ & Al_{195}\ Ti_{6}\ Si_{486}\ P_{6}(O_{151}\ OH_{93});\\ 2.\;& K_{10}\ Na_{26}\ Ca_{112}\ Mg_{188}\ (Fe_{\text{tot}})_{52}\\ & Al_{106}\ Ti_{3}\ Si_{413}\ P_{1}(O_{1364}OH_{236}). \end{aligned} \]

Fig. 3. Variation diagram of changes in the composition of diorite-porphyrite dikes during near-skarn metamorphism (Ninth skarn-magnetite lens), 1—unaltered diorite porphyrite and 2—metamorphosed diorite porphyrite.

Relation of dikes to gold-ore mineralization

In the areas of all known stockwork gold-ore deposits and occurrences of Kommunar, a spatial association of dike and hydrothermal formations is very clearly evident. Usually, the areas of greatest development of quartz-ore veins and veinlets are characterized at the same time by a significant distribution of dikes. Most of the gold-ore deposits of the ore field are located in the near-contact zone (up to 1 km wide) of the Solgonsk granodiorite massif; the main number of dikes is also confined to this same zone. A spatial confinement of quartz-ore veinlet development to individual dike bodies of intermediate composition is often observed. For example, at the stockwork deposit of Podlunnyi Golets, in a beresitized dike 0.5 m thick, 43 quartz veinlets are concentrated, whereas in the enclosing porphyro-

in the visible diorites, at a distance of 2–3 m on both sides of the dike, barely 10–15 quartz-ore veinlets are counted.

In other cases the quartz–gold-ore veinlets are arranged along the dikes; moreover, near the dikes they change their strike from crosscutting to subparallel, as if spreading out along the contacts of the dike bodies. In these places, although not always intensively, the dike rocks undergo silicification, chloritization and actinolitization of pyroxenes and amphiboles, sericitization, carbonatization, epidotization, and, more rarely, albitization of plagioclases. Evidently, in these cases the dikes played the role of peculiar barriers limiting the spread of hydrothermal mineralization, thereby promoting the formation of separate rich ore shoots and nests. The author was unable to establish facts of an obvious intersection of quartz-ore veinlets and veins by dikes, or to detect xenoliths of silicified rocks and ores in the dike bodies themselves of the first and second age groups. Within the Solgonsky area a quartz vein (Ust-Saktychulskaya) has been established, which occurs on the footwall side of a dike of fine-grained diorites, and from it numerous small quartz apophyses extend into the rocks of the dike.

In addition, almost everywhere there is an established confinement of dikes and hydrothermal manifestations to the same types of fissure structures (Fig. 2, a, b), which we have treated in detail in another article.

A close connection is established between dike formation and ore deposition, which is expressed in the presence within the ore field of both pre-ore (first and second groups) and post-ore (third group) dikes. The dikes of the first and second age groups, evidently associated with a single magmatic source, are pre-ore, whereas the olivine gabbro-porphyrites and teschenites, belonging to a younger, presumably Devonian magmatism, are post-ore. The pre-ore dikes are often intensely hydrothermally altered, up to the formation of beresites, whereas the post-ore dikes remain unaffected by processes of hydrothermal metamorphism, although they occur under analogous conditions.

A close geochemical connection is observed between the dike and hydrothermal formations. Thus, many trace elements contained in the dikes of the second age group (copper, lead, zinc, cobalt, molybdenum, arsenic) in hydrothermalites usually enter into the composition of chalcopyrite, faded ores, galena, sphalerite, and cobalt-bearing pyrite. Such trace elements as manganese, titanium, vanadium, zirconium, cobalt, and molybdenum are through-going for the dikes and gold ores.

Conversely, in the ores and dikes of the first age group no such distinct continuity is observed with respect to trace elements, with the exception of such elements as manganese, titanium, and vanadium, which are widespread in almost all rocks. This probably indicates that the formation of the dikes of the first group and of the gold ores took place from melts and solutions supplied from different magmatic chambers. Chemical analyses almost constantly establish the gold content in dikes of fine-grained diorites of the second age group; in the enclosing rocks, aureoles of weak gold content are often revealed, although in the dikes themselves no traces of visible hydrothermal mineralization have been found. It is possible that the formation of dikes of fine-grained diorites preceded the subsequent gold mineralization. If it is taken into account that the dikes of the first and second age groups are genetically connected with the Solgonsky granodiorite intrusion, then we arrive at the conclusion that there is a close connection between the dikes and gold minerali—

formation of the same intrusion. This relationship is probably due not only to the unity of the structural pathways along which the magmatic melt that formed the dikes of the second age group, and the hydrothermal solutions, penetrated, but also to the commonality of the magmatic source.

Hydrothermal alterations in dikes in areas of gold mineralization are manifested rather widely. The most typical alterations in dike rocks of acidic and intermediate composition (of the first and second age groups) are albitization, actinolitization, silicification, chloritization, carbonatization, sericitization, pyritization, and beresitization.

Albitization is the earliest process, as a result of which the autometamorphically altered plagioclases of dikes of the second group are regenerated with a change in composition from No. 35—45 to 15—8. Characteristically, where albite veinlets cut plagioclase twins, the latter is oriented in the plane of orientation of the intersected plagioclase; as a result, twins appear in the hydrothermal albite that are continuations of the twins of magmatic plagioclase. Pyroxenes and amphiboles are likewise corroded by albite along cleavage and parting cracks, and sphene appears among the albite aggregates.

In studying hydrothermally metamorphosed dikes of fine-grained diorites of Podlunnyi Golets, linear zones of albitized rocks were encountered. Zones of albitization up to 2—3 m thick arise in zones of maximum fracturing confined to the endocontacts of the dikes. The front of metasomatic replacement follows along the contacts of the dikes, extending into the dike bodies along diagonal and longitudinal shear fractures for a distance of 1.0—4 m, with the total thickness of the dikes up to 12 m. As a result, metasomatic zones arise, with uneven bay-like margins on the side of the dike diorites and even linear contacts on the side of the enclosing porphyritic gabbro-diorites.

The mineral composition of the metasomatic rock is represented by albite No. 1—3 (up to 70%), quartz (up to 20%), green hornblende ($2V = (-) 56^\circ$; $cNg = 16^\circ$; $Ng = 1.676—1.680$, $Nm = 1.667—1.672$, $Np = 1.659—1.661$; $Ng—Np = 0.015—0.019$), calcite, and epidote (up to 2—3% of the total volume of the rock).

A very interesting circumstance is that, during the subsequent ore stage, the zones of albitized diorites underwent silicification and gold mineralization. Vein quartz, together with gold, following along the selvages of amphibole veinlets, replaces and cements individual grains of hornblende or, in the form of small lenses and cluster-like segregations, impregnates the quartz-albite metasomatic aggregate.

The next process of hydrothermal alteration in rocks of all types of aschist dikes is the actinolitization of pyroxenes and hornblende, during which brown iron oxides are released in the form of irregular small accumulations. Actinolite ($2V = (-) 82^\circ$, $cNg = 16^\circ$, $Ng—Np = 0.022$) is in turn replaced by pale-green pennine ($cNg = 3—5^\circ$, $Nm = 1.570$). Needles of rutile and irregularly shaped accumulations of sphene are often encountered in the chlorite. Ultimately, only outlines remain of the primary mafic minerals, filled with chlorite, sphene, iron oxides, calcite, epidote, and zoisite. Large flakes of biotite are usually replaced by chlorite with an admixture of calcite, epidote, sphene, iron oxides, and fine-needled actinolite and rutile, which often form

sagenite lattice. In dikes of more acidic composition, however, hornblende is replaced not by actinolite but by tremolite, in the form of tangled-fibrous and radial-fibrous aggregates.

Carbonatization is manifested most intensely in dike rocks in areas where late quartz-carbonate and carbonate veinlets are developed. The carbonates, usually represented by calcite ($Ng = 1.666$, $Np = 1.491$, i.e., containing up to 7–6% of the $MnCO_3$ molecule [13], which is confirmed by spectral analysis) and rarely by ankerite ($Ng = 1.722$, $Np = 1.530$, containing up to 25% of the $(Mg, Fe)CO_3$ molecule [13]), sometimes replace feldspars, forming uneven-grained clustered segregations or individual veinlets up to 0.05–0.5 mm thick and more. In places the dike rock is almost entirely replaced by calcite, where, in addition to calcite, sericite and pyrite are found.

Within stockwork-type deposits, hydrothermal alterations in dikes of intermediate composition are often manifested in the formation of beresites. In appearance, the beresitized rocks acquire a very characteristic light yellowish-gray color and in places are intensely impregnated with large (up to 0.5–2.0 mm) pyrite metacrystals. The process of beresitization often affects considerable portions of dikes of diorite porphyrites, fine-grained diorites, and quartz porphyries, usually spreading along the contacts of the dikes and often altering the rocks of the dike bodies completely. Belts of rocks altered by beresitization are usually linearly elongated along the contacts of dikes, more rarely have sinuous outlines, and sometimes display a semblance of zonal structure: at the contact with quartz-ore veinlets the rocks are intensely beresitized, and then gradually pass into weakly beresitized varieties. No dependence has been established between the size of the beresitization halo and the thickness of the dike bodies or their petrographic composition. It has been noted that the degree of beresitization increases somewhat in areas where zones of intense fracturing or disjunctive seams develop in the near-contact belt of dikes, and also in cases of pinch-outs of quartz-ore veinlets.

The beresitized rocks consist of muscovite, calcite, albite, and pyrite, with relicts of actinolite, primary quartz, and chlorite, and sometimes preserve a relict porphyritic texture, clearly distinguishable in thin sections. Primary plagioclase contains numerous small flakes and clustered segregations of muscovite and sericite ($Ng = 1.587$–$1.608$, $Nm = 1.593$–$1.605$, $Np = 1.557$–$1.565$, $Ng - Np = 0.040$–$0.43$, $2V = (-) 5$–$6^\circ$), belonging to a variety containing up to 10–25% ferrisilicate [14]. The size of the muscovite flakes is up to 0.05–0.3 mm; their aggregates sometimes form a lattice oriented along (001) and (010) in the plagioclases.

A finely scaly aggregate of sericite often replaces the fine-grained groundmass and, frequently together with chlorite, replaces biotite. The amount of muscovite in the rock ranges from 5 to 15–25% of the total volume.

The second most important mineral is calcite, which develops over all minerals in the form of uneven-grained aggregates, sometimes together with secondary quartz. It often forms independent small veinlets and clustered segregations, sometimes constituting up to 30% of the total mineral composition of the rock.

Pyrite is sometimes present in appreciable quantities and forms cubic metacrystals up to 0.2–2 mm and more in size, irregularly disseminated in the rock.

Quartz–gold-ore veinlets are often located both in weakly and in deeply beresitized dike rocks and always

have a cross-cutting position with respect to the hydrothermally altered formations. Spectral analyses have established that pyrite from beresitized dikes contains basically the same set of impurity elements as pyrite from ore veinlets: manganese, titanium, nickel, cobalt, vanadium, copper, arsenic, but lacks lead and zinc, which are characteristic of ore pyrite. Even these far from complete facts quite clearly indicate that the processes of hydrothermal alteration of the dike rocks proceeded under the influence of the first portions of hydrothermal solutions, which did not yet carry ore components; i.e., the “near-vein” alterations preceded the stage of formation of the quartz-ore veins.

According to recalculations of chemical analyses of unaltered and beresitized rocks (after Barth \[16\]), the material balance during hydrothermal metamorphism of dikes of diorite porphyrites and fine-grained diorites has the following form (in ions):

input: potassium — 2, silicon — 54;
removal: sodium — 6, calcium — 19, magnesium — 16, iron — 33, aluminum — 29; relatively immobile elements: titanium and phosphorus.

The chemical composition of the rocks is given in Table 2, and the material balance is shown graphically in Fig. 4.

Table 2

Note: 1—chemical analysis of a sample of unaltered diorite porphyrite; 2—chemical analysis of albitized diorite porphyrite; 3—chemical analysis of weakly beresitized diorite porphyrite (dike of Podlunny Golets); 4—chemical analysis of beresitized diorite porphyrite (dike of Podlunny Golets). All analyses were performed in the Central Laboratory of the Krasnoyarsk Geological Administration.

Formulas of rocks after Barth:

1. \(\mathrm{K}_{25}\mathrm{Na}_{68}\mathrm{Ca}_{60}\mathrm{Mg}_{35}(\mathrm{Fe}_{\mathrm{tot.}})_{68}\mathrm{Al}_{195}\mathrm{Ti}_{5}\mathrm{Si}_{486}\mathrm{P}_{6}(\mathrm{O}_{1510}\mathrm{O}_{90});\)
2. \(\mathrm{K}_{22}\mathrm{Na}_{54}\mathrm{Ca}_{45}\mathrm{Mg}_{32}(\mathrm{Fe}_{\mathrm{tot.}})_{39}\mathrm{Al}_{189}\mathrm{Ti}_{2}\mathrm{Si}_{497}\mathrm{P}_{3}(\mathrm{O}_{1364}\mathrm{O}_{236});\)
3. \(\mathrm{K}_{4}\mathrm{Na}_{107}\mathrm{Ca}_{34}\mathrm{Mg}_{16}(\mathrm{Fe}_{\mathrm{tot.}})_{36}\mathrm{Al}_{196}\mathrm{Ti}_{3}\mathrm{Si}_{502}\mathrm{P}_{3}(\mathrm{O}_{1459}\mathrm{OH}_{141});\)
4. \(\mathrm{K}_{27}\mathrm{Na}_{62}\mathrm{Ca}_{41}\mathrm{Mg}_{19}(\mathrm{Fe}_{\mathrm{tot.}})_{35}\mathrm{Al}_{166}\mathrm{Ti}_{3}\mathrm{Si}_{550}\mathrm{P}_{1}(\mathrm{O}_{1509}\mathrm{OH}_{91}).\)

From the graph presented it is evident that the process of beresitization is accompanied by high mobility of such elements as sodium, potassium, divalent iron, calcium, magnesium, aluminum, silicon, sulfur, etc.

In the process of hydrothermal albitization of dike rocks, which usually precedes beresitization, the material balance is as follows (in ions) (Table 2 and Fig. 4):

addition: sodium — 39, silicon — 16, hydroxyl — 51;

Fig. 4. Variation diagram of changes in the composition of dikes of diorite porphyrites during hydrothermal metamorphism:
1 — unaltered diorite porphyrite;
2 — albitized diorite porphyrite;
3 — weakly beresitized diorite porphyrite;
4 — beresitized diorite porphyrite.

removal: potassium — 21, calcium — 26, magnesium — 19, ferrous iron — 32, titanium — 3, phosphorus — 3;

slightly mobile elements — aluminum.

Conclusions

1. Skarn-metasomatic and gold-ore formations are post-dike in relation to dike bodies of the shoshonite series (the first and second groups, genetically connected with the granodiorite intrusion) and pre-dike in relation to the dikes of subalkaline diabase porphyrites (teschenites) and olivine gabbro-porphyrites and gabbro, genetically connected most likely with younger Devonian magmatism. The observed alternation of dikes and mineralization evidently indicates the multistage character of magmatic processes and dike formation.

2. The formation of the dike series and subsequent mineralization proceeded with preservation of the plan of tectonic deformations that determined the emplacement of similar fracture structures and controlled both the intrusion of dikes of different generations and the hydrothermal mineralization.

3. Near-vein alterations in the dike rocks were expressed as albitization, amphibolization, sericitization, and carbonatization, and sometimes also beresitization, which was especially clearly manifested in areas of stockwork-type mineralization. The intensity of hydrothermal alterations was apparently determined by the favorable geological-structural position of individual dike bodies, which predetermined the degree of con-

connection with the magmatic chamber that emitted the metalliferous emanations. Wall-rock alterations usually precede the stage of principal ore formation and are evidently associated with the influx of the earliest portion of hydrothermal solutions.

Comparing the hydrothermal alterations noted with the typical processes of beresitization of dike rocks in the Urals, described by N. and M. Borodaevsky [2], we come to the conclusion that, in general, these processes are similar. The distinguishing features are that during beresitization of the rocks of the Kommunar dike complex there is no significant introduction of potassium and aluminum, as is observed in the process of formation of the Ural beresites, and a significant introduction of sodium is noted, especially in the initial period of hydrothermal alteration (albitization), which probably indicates the specific composition of the metamorphosing solutions. In addition, the beresitized rocks of Kommunar are very strongly enriched in calcite, which is probably due to the higher calcium content in the original rocks of the ore field, as a result of which the excess calcium ions entering the solution was consumed in the formation of calcite and was removed only in part. A second reason for the enrichment of the altered rocks of Kommunar in calcite is the superposition of later, substantially carbonate solutions on previously beresitized varieties of the dike rocks (replacement of muscovite by late calcite is observed).

Thus, the products of hydrothermal metamorphism of the dike series of intrusive rocks of Kommunar may serve as an additional prospecting criterion for gold mineralization in the district.

REFERENCES

1. Kh. M. Abdullaev. Dikes and Ore Formation. Gosgeoltekhizdat, 1957.

2. N. P. Borodaevsky and M. B. Borodaevskaya. The Berezovskoye Ore Field (Geological Structure). Moscow, Metallurgizdat, 1947.

3. A. Ya. Bulynnikov. Gold-ore formations and gold-bearing provinces of the Altai-Sayan mountain system. Publishing House of Tomsk State University, vol. 102, Geological Series, 1948.

4. A. Ya. Bulynnikov. On small intrusions and the gold mineralization associated with them. Materials on Mineralogy, Petrography, and Mineral Resources of Western Siberia. Publishing House of Tomsk State University, 1962.

5. T. M. Dembo. Phenomena of anatexis, hybridism, and assimilation in the Caledonian granitoid intrusion of the northern part of the Kuznetsk Alatau. Soviet Geology, collection 51, 1956.

6. G. N. Ivanova, N. M. Polevaya, et al. Absolute age of some magmatic and metamorphic rocks of the central part of the Altai-Sayan region. In: Materials on the Regional Geology of the Altai-Sayan Region, VSEGEI, Leningrad, 1961.

7. G. A. Ivankin, Yu. A. Kuznetsov. Magmatism and metamorphism of the Kuznetsk Alatau. Geology of the USSR, vol. XV, part 1, Krasnoyarsk Territory, Gosgeoltekhizdat, 1961.

8. G. A. Ivankin et al. On the stratigraphy of ancient sequences of the eastern slope of the Kuznetsk Alatau. Collection of Reports Dedicated to the Memory of Academicians V. A. Obruchev and M. A. Usov. Publishing House of Tomsk State University, 1964.

9. S. S. Ilyenok. Principal features of the petrology of the Patyn massif. Geology and Geophysics, Siberian Branch of the Academy of Sciences of the USSR, No. 4, 1960.

10. A. F. Korobeynikov. Relation of skarns to gold mineralization in the district of the Kommunar gold-ore cluster. Materials on Mineralogy, Petrography, and Mineral Resources of Western Siberia, Publishing House of Tomsk State University, 1962.

11. Yu. A. Kuznetsov. On principles for distinguishing and classifying magmatic rocks. In: The Basic Ideas of M. A. Usov in Geology, Publishing House of the Academy of Sciences of the Kazakh SSR, 1960.

12. A. A. Mossakovsky. Tectonic Development of the Minusinsk Depressions and Their Mountain Framework in the Precambrian and Paleozoic. Gosgeoltekhizdat, 1963.

13. V. B. Tatarsky. Microscopic Determination of Carbonates of the Calcite and Aragonite Groups. Gosgeoltekhizdat, Leningrad, 1955.

14. V. E. Treger. Tables for the Optical Determination of Rock-Forming Minerals. Gosgeoltekhizdat, 1958.

15. N. A. Fogelman, A. E. Shabalovsky. Conditions of localization of stockwork deposits within the Kommunar ore field on the eastern slope of the Kuznetsk Alatau. Proceedings of NIGRIZoloto, No. 21, 1956.

16. S. D. Chetverikov. Manual for Petrochemical Calculations. Gosgeoltekhizdat, 1956.

1. In the present communication we do not consider dike-like bodies of dioritoids of the Boi intrusive complex, since they belong to an independent group of small intrusions of the district [4]. ↩

2. The specific gravities of the minerals were determined by the pycnometric method. ↩

3. In the recalculation, metasomatically altered dike rocks significantly enriched in magnetite were not taken into account. ↩