GENETIC FEATURES OF THE LYUBAVINSKOYE GOLD ORE DEPOSIT

G. V. Shubin, A. V. Matsushevsky (TPI)

The Lyubavinskoye gold ore deposit is located in the south of Chita Oblast and is confined to an intraregional zone of increased fracturing of sublatitudinal strike. Within this zone magmatic and ore formations are concentrated.

The geological structure of the Lyubavinskoye deposit includes: 1) granitoid stocks of Triassic age, having a complex morphology with an overall elongation in the sublatitudinal direction; 2) dike rocks, represented, in the sequence of formation, by albitophyres, granite-porphyries, quartz porphyries and porphyrites, microdiorites, porphyrites, and spessartites. These rocks form a dike belt of complex morphology with a general sublatitudinal strike. A number of investigators regard the dike formations as a complex of small intrusions of Upper Jurassic age.

The magmatic formations listed above cut through a Permian sandy-shaly sequence of aleurolite-pelitic shales interbedded with sandstones. Quartz–gold ore veins are also confined to this same zone of fracturing, being concentrated within the granitoid stocks. All the circumstances listed above concerning the spatial distribution and conditions of formation of the magmatic and ore formations make it possible to regard the Lyubavinskaya zone of increased fracturing as an expression at the surface of a deep-seated fault.

The ore bodies are represented by quartz veins with an insignificant amount of sulfides and mainly fill structures of latitudinal, northwestern, northeastern, and meridional trends. Study of the mineralization of the ore bodies made it possible to distinguish six mineral associations in the deposit (arsenopyrite–pyrite, quartz, quartz–sulfide, quartz–ankerite–gold–sulfide, quartz–pyrite, quartz–calcite–sulfide), which can be combined into five stages (Fig. 1). Below is a description of these stages in their age sequence.

The arsenopyrite stage is represented by arsenopyrite, more rarely by pyrite, and is associated with the first portions of hydrothermal solutions, which, impregnating zones of pre-ore tectonic disturbances, deposited in the host rocks and in these zones sporadically disseminated euhedral crystals of arsenopyrite and pyrite. The latter are accompanied by the formation of a small amount of sericite. A characteristic feature of this mineralization is the presence of dispersed gold, associated—

associated with arsenopyrite. In order to determine what kind of gold this is—syngenetic with the arsenopyrite or later gold adsorbed on the surfaces of its crystals—the following analyses were carried out: fire assay, dithizone, and dithizone after preliminary treatment of the surface of the arsenopyrite crystals with the aim of removing possible adsorbed gold.

Fig. 1. Paragenetic scheme of mineral formation

Labels in the scheme:

• Hypogene epoch
• Stages
  • Arsenopyrite
  • Quartz
  • Quartz–sulfide
  • Gold–sulfide
  • Carbonate
• Hypergene epoch
• Minerals
• Arsenopyrite
• Pyrite
• Wolframite
• Molybdenite
• Sphalerite
• Galena
• Pyrrhotite
• Chalcopyrite
• Tetrahedrite
• Boulangerite
• Gold
• Fahlore
• Albite
• Anorthoclase
• Quartz
• Ankerite
• Calcite
• Chlorite
• Chalcosine
• Anglesite
• Cerussite
• Covellite
• Goethite
• Malachite
• Pyromorphite
• Ore-forming elements
• Arsenopyrite stage: Au, As
• Quartz stage: W
• Quartz–sulfide stage: As, Mo
• Gold–sulfide stage: Pb, Cu, Zn, Sb, Au
• Carbonate stage: As
• Specific elements
• Arsenopyrite stage: Bi, Sn
• Quartz stage: W
• Quartz–sulfide stage: Bi, Sn
• Gold–sulfide stage: Hg, Cd, In, Bi, Sn, Cr, Ga
• Carbonate stage: Sr
• Persistent elements
• Pb, Mo, Cu, Zn, Ag, Sb, Mn, Co, Ti, Ni, As, Ba

gold. All these analyses showed the presence of gold in arsenopyrite. Thus, the analyses carried out make it possible to say that the gold was syngenetic with the arsenopyrite and was located inside its crystals.

The quartz stage is characterized by the formation both of large veins and of a whole series of small veinlets, with simultaneous silicification and sericitization of the enclosing rocks. The principal mineral is gray medium- and fine-grained quartz, often with drusy cavities—

with comb quartz, sometimes together with sulfides of later stages.

Examination of a large number of quartz veins and stringers indicates the superimposed character of the sulfide mineralization; the quartz itself was accompanied by the deposition of anorthoclase, albite, and a small amount of wolframite.

Quartz-sulfide stage. This stage is characterized by sulfides represented by pyrite, arsenopyrite, and molybdenite, which occur as nests, more rarely as veinlets, in the main mass of milky-white, mostly fine-grained quartz. Associated with this stage are small-scale phenomena of silicification and sericitization of the enclosing rocks. A characteristic feature of this stage is the presence of molybdenite, which, occurring in platy and radial-radiating aggregates, is for the most part spatially separated from associations of the other sulfides. Most often molybdenite is confined to the selvages of quartz veins.

Gold-sulfide stage determines the ore mineralization proper, manifested in the form of low-thickness veinlets consisting of quartz, ankerite, and chlorite in association with pyrite, sphalerite, galena, pyrrhotite, chalcopyrite, tetrahedrite, boulangerite, and gold. The manifestation of the mineralization described was accompanied by an intensive process of sericitization both of the enclosing rocks and of the quartz veins themselves, with the formation, in the latter case, of typical quartz-sericite rocks. After the establishment of the main gold-sulfide mineralization, minor intrastage movements occurred, marked by the appearance of bluish-gray chalcedony-like quartz accompanied by fine-grained monomineralic aggregates of pyrite. Among the minerals of this stage, attention is drawn to sphalerite, which contains varying amounts of bodies of solid-solution exsolution. The latter are represented by chalcopyrite, pyrrhotite, and stannine (?). Usually the exsolution products have an oval (chalcopyrite) or spindle-shaped (pyrrhotite) form and are located either inside twinned individuals or along cleavage planes and twin seams.

In individual cases the exsolution bodies are distributed unevenly over the entire area of the grain—the marginal parts of sphalerite grains contain a larger number of exsolution bodies than the central parts of the grains. Sometimes exsolution bodies are encountered that are represented not by one, but simultaneously by two minerals—chalcopyrite and pyrrhotite. In this case the boundary between chalcopyrite and pyrrhotite is a clear straight or smoothly curved line without traces of corrosion.

In isolated cases, aggregates of sphalerite occur with inclusions of pyrite crystals arranged as parallel zones. We regard this fact as a structure of periodic-rhythmic deposition of sphalerite and pyrite. In the association galena—chalcopyrite—tetrahedrite—boulangerite—gold, the bulk of the galena was deposited predominantly earlier than all the listed minerals; however, there are data allowing one to say that the process of galena deposition from solutions continued in small amounts up to the deposition of tetrahedrite, as evidenced by graphic intergrowths of galena with tetrahedrite.

A distinctive feature of chalcopyrite is the established presence within it of sphalerite inclusions. The form of these inclusions is very diverse: four-rayed stars, skeletal forms with a “cubic cross of axes” [13], branched and paw-like segregations. The sphalerite bodies have sharp, even boundaries and are monocrystalline—

...grains. It should also be noted that the rays of the starlets within a single chalcopyrite grain are arranged parallel to one another. All of the above, taking into account the fact that the dimensions of the elementary cells of the spatial lattices of sphalerite \((a_0 = 5.39)\) and chalcopyrite \((a_0 = 5.24)\) are approximately equal at coordination number 4 of these minerals, makes it possible to regard these sphalerite segregations in chalcopyrite as bodies of decomposition of a solid solution. Similar conclusions may also be found in a number of other investigators [13, 19].

Gold is the latest mineral of the fourth stage. Characteristic is the close spatial association of gold with arsenopyrite, galena, and chalcopyrite. Gold is not infrequently observed without any visible association with sulfides, forming anhedral segregations in quartz. As investigations have shown, the morphology of the gold particles is highly varied (Fig. 2) and depends on the character of the space filled by the gold. The entire variety of morphogenetic types of gold particles may be reduced to three

Fig. 2. Morphology of gold particles. Explanations in the text

groups [9, 10]: 1) gold particles formed by the filling of fissure cavities; here the following forms of gold particles are distinguished: lumpy-angular (Fig. 2, е), veinlet-like platy (Fig. 2, ж), dendritic-leaflike (Fig. 2, д), amoeboid (Fig. 2, а); 2) gold particles formed by filling intergranular space in quartz veins; in this case the following forms of gold particles occur: acicular (Fig. 2, б), complex-patterned with impressions of individual crystals of quartz and other minerals (Fig. 2, в), thin-platy, angular (Fig. 2, г); 3) gold particles formed by replacement of minerals deposited earlier. Gold particles of this group are characterized by granular, droplet-like, and amoeboid forms.

The carbonate stage is expressed in the formation of veinlets and nests composed of calcite or a quartz-calcite aggregate, commonly with cavities filled by well-formed...

rhombohedral calcite crystals and small quartz druses. In this stage, an extremely insignificant amount of pyrite and arsenopyrite was deposited; these, like quartz, did not always accompany calcite in equal measure, calcite being the principal mineral of this stage.

An analysis of the factual material on the development of mineral associations during the formation of all the stages described above permits the following considerations to be expressed regarding the genetic features of the deposit.

At the very beginning of their development, the mineral-forming solutions were capable of transporting arsenic, iron, gold, sulfur, and potassium, which are characteristic of the arsenopyrite stage. It should evidently be assumed that these first portions of the solutions were enriched in volatile components, owing to which the deposition of mineral matter occurred not in the form of veinlets or small veins, characteristic of liquid solutions, but in the form of sporadic disseminations of separate, well-formed crystals, which is usually characteristic of mineral-forming solutions with a predominance of the gaseous phase. A. E. Fersman considered the crystallization of arsenopyrite approximately in phase G—that is, in the final supercritical phase of the pneumatolytic process—to be quite probable. During this same period a certain amount of sericite was formed, which may indicate the alkaline character of the gaseous phase. It should be added that the alkaline character of this stage was evidently influenced to some degree by earlier alkaline processes of autometasomatism, manifested in the intrusive rocks, after which the postmagmatic processes under consideration began. As follows from the nature of the mineral association of the first stage, the solutions from which it formed had a comparatively low value of oxidation-reduction potential. In this case, gold and the elements accompanying it were present in the solutions, probably in the form of a sulfide complex [15] and arsenic-sulfur compounds in the presence of potassium.

Subsequently, after preliminary tectonic impulses, as the solutions developed, the role of aqueous solutions, still alkaline in character, increased, leading to an intensive superposition of hydrothermal mineralization. Quartz veins and the accompanying phenomena of silicification and sericitization were formed. During this same period, anorthoclase, more rarely albite, and small amounts of wolframite were separated. The presence of sericite, anorthoclase, and albite indicates the alkaline character of the initial solutions, in which silica was transported, most probably, in the form of a complex compound of the type \((K, Na)_2SiO_3\) [6], and wolframite in the form of the compound \((K, Na)_2WO_4\) [1]. This assumption is confirmed by the data of chemistry, experimental work, and, finally, by direct study of the features of the paragenesis of the minerals of this stage.

As A. G. Betekhtin [2] indicates, the conditions necessary for the separation of wolframite in the early stages of the ore process, with an increased concentration of free oxygen ions, may indicate that the formation of the quartz–gold-ore veins occurred at shallow depths.

The presence of a predominant amount of sulfides, the presence of ankerite, sericite, and chlorite indicate that the formation of the mineral associations of the quartz-sulfide and gold-sulfide stages proceeded from alkaline or weakly alkaline solutions. The disseminated textures of the ores widely developed at the deposit, the thin ore veinlets, the clear sequence of ore minerals, the corrosion relations between them, and also the absence of colloform structures—all this rather indicates the formation of the ores from true solutions.

The presence of carbonates and sulfides, as V. F. Barabanov [1] points out, is regarded as direct evidence for the absence in the solutions of stronger acids. A. G. Betekhtin considers alkaline solutions to be a very favorable medium for the formation of sulfides, as well as chlorite, sericite, and carbonates. R. L. Folk [21] showed that sericite forms in weakly alkaline solutions, since with increasing acidity of the solutions sericite becomes unstable. V. V. Shcherbina [17], considering the forms of transport of chemical elements during processes of postmagmatic mineral formation, showed from numerous examples that, for 90% of deposits of this type, the conditions of ore deposition are characterized by the presence of a weakly alkaline medium.

As for the forms of transport of ore material in hydrothermal solutions of these stages, this can be judged only indirectly, on the basis of analysis of the products of their activity, and also by evaluating the available experimental data. As theoretical and experimental studies on this question have shown, the principal form of transport of metals in solutions is complex compounds [4, 11, 14, 18]. Of special importance for complex formation is the constant presence in ore-forming solutions of sodium and potassium, which leads to the obligatory formation of stable complexes [11].

In connection with this, let us consider the nature of the transport of the principal components of the ore veins by hydrothermal solutions, which throughout the quartz–sulfide and gold–sulfide stages of mineral formation remained essentially potassium-bearing.

Taking the foregoing into account, it appears to us that the transport of silica occurred in the form of a compound of the type \(K_2SiO_3\); the transport of the principal ore elements, taking into account the data of N. G. Tyurin [15], occurred in the form of a complex compound \(K_n[Me(S_2O_3)^{3-}_2]\), with the possible participation of the anion \(CO_3^{2-}\), as indicated by the presence of carbonates. At the same time, it remains to be noted that the gold complex, as N. G. Tyurin indicates, possesses exceptional stability and surpasses analogous complexes of copper, lead, and other metals. This circumstance is one of the essential factors determining the very latest time of gold deposition at the deposit.

As A. G. Betekhtin [2] points out, the sulfur and oxygen regime, taking into account changes in pressure and temperature, exerts a great influence on the sequence of mineral deposition. If we consider the sequence of mineral deposition in the quartz–sulfide stage, represented by the association arsenopyrite—pyrite—molybdenite, we shall see that, first of all, a general increase in the sulfur concentration takes place toward the end of the stage. This circumstance determined first the deposition of “low-sulfur” arsenopyrite, and then of pyrite and molybdenite as “high-sulfur” compounds. In this same sequence there is also an increase in the oxidation potential, which is expressed in the replacement of the ion \(S_{--2}\) by \(S_2^{2-}\), since the presence of arsenopyrite indicates a low oxidation–reduction potential [2] in the initial period of this stage.

Further, after preliminary tectonic movements, deposition of the mineral association of the gold–sulfide stage began; during this period the solutions, while continuing to remain “high-sulfur,” at the same time are characterized by a variable oxidation–reduction potential. This is indicated by the alternation of deposition of pyrite and sphalerite. Following this, the oxidation potential levels off in the direction of its decrease, which caused the precipitation of galena, pyrrhotite, and chalcopyrite. The final stages in the development of the gold–sulfide stage are characterized by an increase in oxidation–reduction potential and by the deposition of sulfoantimonides. Experimental works

S. Robinson [20] and the studies of G. S. Lisetskaya (1954), as noted by G. N. Gamyanin [4], showed that the formation of sulfoantimonites takes place only in an alkaline medium as a result of the formation of the complex antimony anion \(\mathrm{SbS_2^-}\), determining, as we have at the deposit, the paragenesis galena–tetrahedrite–boulangerite, which can be clearly seen on the composition–paragenesis diagram \(\mathrm{Pb—Cu—S^{2-}—SbS_2^-}\) presented by G. N. Gamyanin (Fig. 3).

The separation of a relatively large mass of galena caused a decrease in the concentration of \(\mathrm{S^{2-}}\), \(\mathrm{Pb^{2+}}\), and an increase in the role of \(\mathrm{SbS_2^-}\) [4], which led to the crystallization of tetrahedrite. For the formation of boulangerite, the complex anion \(\mathrm{SbS^-}\) is likewise necessary; its appearance is possible only under alkaline conditions.

Fig. 3. Composition–paragenesis diagram in the system \(\mathrm{Pb—Cu—S^{2-}—SbS_2^-}\): 1) galena, 2) boulangerite, 3) tetrahedrite

We have already noted that gold, forming stable complex compounds, precipitates at the very last moment, which is what we observe in the gold-sulfide stage. The preceding profound changes in physicochemical conditions (\(\mathrm{Eh—pH}\)) as a result of changes in the regime of sulfur and oxygen in the solutions caused the destruction of complex compounds with the release of gold and the entire spectrum of sulfides.

At the concluding stage in the formation of the gold-sulfide stage, after the deposition of gold, minor intrastage movements occurred; after them, the concentration of sulfide ion and silica changed under a high degree of supersaturation of the mineral-forming solutions. These circumstances promoted the appearance of numerous crystallization centers, with the formation of veinlets of chalcedony-like quartz with small but numerous pyrite crystals.

The above-described processes of formation of the quartz-sulfide and gold-sulfide stages can evidently be identified with the “late alkaline stage” of postmagmatic processes, according to D. S. Korzhinsky [8].

On the basis of an analysis of mineral parageneses, the interrelations of paragenetic associations, and the sequence of mineral formation, the following conclusions may be drawn.

A change in the acidity—alkalinity regime is observed not only for the ore process as a whole, but also for individual stages. In particular, it is clearly manifested in the third and fourth stages. This circumstance, taking into account the spatial position of the stages, may indicate the possible presence of portions of solutions, differing in time, that participated in the formation of the mineral associations. Analysis of the latter makes it possible, according to N. V. Petrovskaya [12], to distinguish two principal types of productive associations: a) the first of them, taking into account the relative constancy of the degree of its gold content, is a “type of variably productive associations”—this is the arsenopyrite stage of mineral formation; b) the second type, corresponding to the gold-sulfide stage, should be distinguished under the name of a late, gold-bearing productive association, or the “type of constantly productive associations.”

In addition to the chemistry of the solutions discussed above, the temperature of the mineral-forming solutions has a major influence on the course of mineral formation and the appearance of definite mineral associations. At present, to determine the temperature of solutions, use is made mainly of analysis of a number of indirect indicators and of data from experimental studies. One such indicator is the decomposition of solid solutions, arising in the process of exsolution of a definite group of sulfides. At the Lyubavinskoye deposit the presence of two systems of solid solutions has been noted: sphalerite—chalcopyrite—pyrrhotite and chalcopyrite—sphalerite. Decomposition of the indicated solid solutions leads to the appearance of inclusions (exsolution bodies) of chalcopyrite and pyrrhotite in sphalerite, and of sphalerite in chalcopyrite. The presence of such decomposition products, as a number of researchers indicate, characterizes a high-temperature mineralization process. Thus, A. A. Filimonova [16], referring to a number of researchers, gives the following temperatures for the decomposition of the sphalerite—chalcopyrite system: 350°—400°, and of the chalcopyrite—sphalerite system: 470°—300°. As P. Ramdohr [13] and Trdlicka Zdenek [19] note, the appearance of sphalerite stars in chalcopyrite is associated only with high-temperature deposits. On the basis of the materials presented, it may be concluded that the quartz-gold-ore mineralization of the Lyubavinskoye deposit formed at medium-to-high temperatures and belongs, on the basis of the criteria of R. M. Konstantinov [7] that we have distinguished, to the gold-arsenopyrite ore formation. The latter is characterized by two mineral types—arsenopyrite and quartz-carbonate-sulfide—and by specific trace elements: mercury, cadmium, indium, bismuth, tin, gallium, strontium, zirconium, and tungsten.

Under the influence of hydrothermal solutions the enclosing rocks underwent alteration. The width of the alteration halos does not exceed 1.5 meters, depending on the thickness of the quartz-gold-ore veins. The near-ore alterations were expressed in silicification, sericitization, carbonatization, and pelitization.

Comparison of the chemical composition of altered and unaltered rocks, recalculated by Barth’s method, showed that, as a result of the action of hydrothermal solutions, the enclosing rocks were enriched in potassium, magnesium, trivalent iron, and partly aluminum, and that sodium, calcium, and divalent iron were removed (Fig. 4).

The character of the near-ore alterations confirms the conclusion we have drawn that the ore-forming process proceeded from alkaline, substantially potassium-bearing solutions. Spectral analyses showed that elements characteristic of the ore process were introduced into the enclosing rocks: tungsten, gallium, molybdenum, zinc, vanadium, silver, beryllium.

Taking into account the morphology of the occurrence of the quartz–gold-ore veins, their textural and structural features (Table 1), the character of the genetics of the mineral associations and the types of near-ore alterations, we, following

Fig. 4. Diagram of gains and losses during near-ore alterations of granitoid stocks: M-11 — unaltered granite of the Gritsevsky stock; L-3 — granite in contact with the Kolonkovaya vein; L-4 — granite 80 cm from the Kolonkovaya vein; L-5 — granite in contact with the Sekushchaya vein; L-6 — granite 1 m from the Sekushchaya vein.

D. P. Gorzhevsky and V. N. Kozerenko [5], may conclude that the formation of the Lyubavinskoye deposit took place at depths fluctuating within the range from 1 to 2 km, and that it belongs to the group of deposits of the hypabyssal facies.

Table 1

Note: The classification of textures is given according to F. N. Shakhov (1961); the classification of structures is given according to M. P. Isaenko (1964).

In conclusion, it should be noted that there is a close paragenetic connection of the mineralization with the dike complex, and a close correspondence in the time of formation of the ore deposition and the Upper Kora intrusive complex, which have as their source a single deep-seated magmatic chamber.

REFERENCES

1. Barabanov V. F. Mineralogy of the tungsten deposits of Eastern Transbaikalia. Leningrad University Press, 1961.

2. Betekhtin A. G. Hydrothermal solutions, their nature and ore-forming processes. Main problems in the doctrine of magmatogenic ore deposits. Publishing House of the Academy of Sciences of the USSR, Moscow, 1953.

3. Beus A. A., Sobolev B. P. Geochemistry of the processes of high-temperature postmagmatic ore formation in granitoids. International Geological Congress, 22nd session. Problems of ore genesis. “Nedra,” 1964.

4. Gomyanin G. P. Parageneses of ore minerals of gold-ore deposits of the Upper Indigirka district. Geology and Geophysics, No. 7, 1965.

5. Gorzhevsky D. I., Kozerenko V. N. Facies of the depth of magmatic rocks and magmatogenic ore deposits. Soviet Geology, No. 8, 1963.

6. Zakharchenko A. I. Mineral-forming solutions and the genesis of quartz veins. Gosgeoltekhizdat, Moscow, 1955.

7. Konstantinov R. M. Methods of study and criteria for distinguishing magmatogenic ore formations in large-scale metallogenic investigations. Endogenic ore formations of Siberia and the Far East. “Nedra,” Moscow, 1966.

8. Korzhinsky D. S. Acidity regime in postmagmatic processes. International Geological Congress, 22nd session. Problems of ore genesis. “Nedra,” 1964.

9. Korobeinikov A. F., Kuzmin A. M. Morphology of gold particles from the area of the Kommunar mine. Proceedings of TPI, vol. 127, issue 1, 1964.

10. Moiseenko V. G. Metamorphism of gold deposits of the Amur region. 1965.

11. Ovchinnikov L. N., Shlyapnikov D. S., Shur A. S. Mobilization and transport of matter in endogenic ore formation. International Geological Congress, 22nd session. Problems of ore genesis. “Nedra,” 1964.

12. Petrovskaya N. V. On productive mineral associations in gold-ore deposits. ZVMO, vol. 84, issue 3, 1955.

13. Ramdohr P. Ore minerals and their intergrowths. IL, 1962.

14. Tyurin N. G. On the question of the composition of hydrothermal solutions. Geology of Ore Deposits, No. 4, 1963.

15. Tyurin N. G. The role of oxidation-reduction potential in the processes of dissolution and precipitation of gold. Collection “Investigations of Natural and Technical Mineral Formation,” Publishing House “Nauka,” 1966.

16. Filimonova A. A. Ore-forming minerals and their intergrowths as geological thermometers. Collection “Mineralogical Thermometry and Barometry.” Publishing House “Nauka,” 1965.

17. Shcherbina V. V. Forms of transport of chemical elements in the process of mineral formation and the conditions of their concentration. Collection “Problems of Geochemistry and Mineralogy,” Publishing House of the Academy of Sciences of the USSR, 1956.

18. Shcherbina V. V. Methods for determining the forms of transport of chemical elements in geochemical processes. Geochemistry, No. 11, 1962.

19. Trdlicka Zdenek, Hoffman Vladimir. New data on the genesis of star-shaped segregations of sphalerite in the copper-colchedanites of Chorni-Krupka in the Ore Mountains. Abstract journal, Geology, Geochemistry, Mineralogy, Petrography, No. 4, 1966.

20. Robinson S. G. Sintensis of LEAD Sulfoantimonites. Econ. geol., vol. 33, 4, 1948.

21. Folk R. L. The alteration of feldspar and its products as studied in the laboratory. Amer. j. sci., vol. 245, No. 6, 1947.