ON THE DISCOVERY OF NATIVE LEAD AND ZINC IN THE KUZNETSK ALATAU

E. V. Vladimirova

(Presented by Professor A. M. Kuzmin)

The literature \[1, 4\] notes that the appearance of metallic lead is closely connected either with phenomena of radioactive decay or with special reducing conditions. The formation of native zinc also occurs under special reducing conditions.

We discovered native lead and zinc on the eastern slope of the Kuznetsk Alatau, in rocks of the Beloyussky and Kolodzhulsky granitoid massifs and in a dike from the zone of the Makarak fault (Martaiga).

On the eastern slope of the Kuznetsk Alatau, intrusive formations of the Lower Paleozoic are widely developed and are grouped into a number of complexes \[3\]. In the area of the right bank of the Bely Iyus River, the rocks of the Beloyussky granitoid complex are most widespread. The latter is subdivided by most researchers into three phases: 1) syenite–diorite, 2) granite, and 3) aplite–pegmatite, which together constitute an intrusive massif of complex composition.

Somewhat north of the outcrop of the rocks of the Beloyussky massif, erosion exposes a stock-like body of the Kolodzhulsky massif, composed of medium-grained granites of adamellite composition.

To study accessory minerals from the rocks of the above-mentioned massifs, 230 crushed samples weighing from 1.0 to 9.0 kg were selected (175 samples from the Beloyussky massif and 55 samples from the Kolodzhulsky massif). Native metals were found in 39 samples.

Native lead was found in all varieties of the rocks studied. In some samples its quantity reaches 100 grains. Noteworthy is the fact that native lead occurs in the greatest amount and most frequently in samples together with a mineral containing a significant quantity of rare and radioactive elements.

The sizes of native-lead grains usually range from 0.08 to 0.2 mm; very rarely do they reach 0.6–1.0 mm. The grains have the form of scales, elongated spindle-shaped, threadlike, and irregular formations. The surface of the grains is uneven, in places—especially along the uneven edges of the scales—with thin smears of the finest whitish formations of cerussite (?). The color of the lead ranges from gray to dark lead-gray, almost black. In section the mineral is shiny metallic, very malleable, easily flattened into a thin plate, ductile, opaque and nonmagnetic, and decomposes in nitric

acid (especially its purest gray-colored varieties); with KJ it gives golden-yellow crystals opalescing in solution.

Spectral analysis of the mineral gave the following results: Pb $\gg 10.0\%$, Sb $> 1.0\%$, Sn $> 1.0\%$, As — $0.1\%$.

By mass-spectrometric determination, carried out in the laboratory of the GRF at the TPI by R. M. Gol'd, the following isotopic composition of the lead under study was established: Pb$^{204}$ — $1.426 \pm 0.005\%$; Pb$^{206}$ — $24.56 \pm 0.07\%$; Pb$^{207}$ — $21.41 \pm 0.05\%$; Pb$^{208}$ — $52.61 \pm 0.09\%$. The ratios are

\[ \frac{\mathrm{Pb}^{206}}{\mathrm{Pb}^{204}} = 17.22;\qquad \frac{\mathrm{Pb}^{207}}{\mathrm{Pb}^{204}} = 15.02;\qquad \frac{\mathrm{Pb}^{208}}{\mathrm{Pb}^{204}} = 36.89. \]

Such a ratio of lead isotopes, according to A. P. Vinogradov [2], is characteristic of formations whose age is close to Cambrian.

Native zinc occurs together with lead, but in a significantly smaller amount than the latter. It has so far been found only in rocks of the second granite phase of the Beloiussk complex and in adamellites of the Kolodzhul massif.

In outward appearance and size, grains of native zinc are very similar to grains of native lead and differ from the latter by a smoother, even surface, lighter color, and somewhat greater hardness. In HCl and HNO$_3$, native zinc dissolves vigorously. In a solution with K$_2$[Hg(NCS$_4$)], by the Shamo method, it gives white feathery crystals. Spectral analysis detected the following elements in native zinc: Zn $\gg 10.0\%$, Pb — $0.001$–$0.003\%$, Cd — $0.003\%$, Nb $> 1.0\%$, Cr — $0.002\%$, Mn — $0.03$–$0.06\%$.

It is not possible to determine more fully the properties of the minerals described, because of the small size of the grains and their small quantity.

In the territory of the Mariinsk taiga, in the basin of the Kiya River, within the Makarak fault, which cuts the Devonian volcanogenic sequence with small bodies of titanaugite gabbro, veins of hydrothermal dolomite with disseminated sulfides are widespread. In this area, in three placer samples along the Madrigenkov stream (samples of B. D. Vasiliev), isolated signs of native lead and zinc were also found. The grains of native lead here have a compacted irregular form and sizes of $1.0$–$3.0$ mm, while the single grain of native zinc is represented by a dense, smooth, shell-like plate up to $1.0$ mm thick and up to $4.0$ mm long. Spectral analysis revealed admixtures of Sb $> 1.0\%$ and Sn $> 1.0\%$ in the native lead from the Mariinsk taiga; in the native zinc, admixtures of Cd — $0.003$–$0.006$ and traces of Nb were established.

The genesis of native lead and zinc has not yet been clarified.

LITERATURE

1. V. I. Vernadsky. Selected Works, vol. II, Publishing House of the Academy of Sciences of the USSR, Moscow, 1955.
2. A. P. Vinogradov. Proceedings of the session of the Department of Chemical Sciences of the Academy of Sciences of the USSR on the peaceful use of atomic energy. Publishing House of the Academy of Sciences of the USSR, Moscow, 1955.
3. G. A. Ivankin, Yu. A. Kuznetsov. Magmatism and metamorphism of the eastern slope of the Kuznetsk Alatau. Geology of the USSR, vol. XV, Krasnoyarsk Territory, 1961.