A NEW PROMISING GOLD ORE DISTRICT IN THE TRANS-ANGARA PART OF THE YENISEI RIDGE

A. S. ALADYSHKIN (KO SNIIGGiMS)

A specific feature of the general metallogenic plan of the Trans-Angara part of the Yenisei Ridge is the subordination of the spatial distribution of endogenous mineralization to the principal northwestern structures of the region, with the manifestation of a clear zonality of a belt type. At the same time, the evolution of the overall character of metallogeny is highly indicative: from the amagmatic eastern zone, through the central zone saturated with endogenous Riphean deposits of gold, antimony, and rare metals, to the western zone, for which lead and zinc are the typical useful minerals. In turn, a characteristic feature of the internal structure of the central (essentially gold-ore) metallogenic zone should be considered the placement of the main mass of primary gold deposits within a relatively narrow belt extending in a north-northwestern direction along the periphery of the zone, along its boundary with the eastern zone. This regularity most definitely indicates the existence of a powerful ore-controlling system of a boundary regional fault. Apparently, this is the most important regularity, since the indicated tectonic control is more distinct and more determining than magmatic control (the genetic connection of the gold mineralization of the Yenisei Ridge with Riphean intrusions), which, for all its significance, is on the whole more general. In light of the foregoing, the entire area where the central and eastern metallogenic zones join should be regarded as potentially promising for gold.

Taking this proposition as a basis, we inevitably come to the conclusion that the “wedging out” of gold mineralization in the Trans-Angara part of the Yenisei Ridge to the south (south of the Gerfed ore cluster), as established by practice, is apparently most correctly connected not with a general “attenuation” of the processes of gold mineralization with increasing distance from the parent intrusions, but with the well-known plunging of the axis of the ridge in a southerly direction (i.e., the gold mineralization simply becomes “blind”). Thus, the entire area south of the “natural boundaries” of the gold-ore province, in the zone of attraction to the above-mentioned fault, should be considered promising for concealed or weakly eroded gold mineralization.

In favor of the opinion expressed, in addition to general geological premises, there are also concrete facts: the presence, within the limits of the given territory, of gold occurrences (for example—the Kozmodemy… [[unclear: word continues on next page]])

[[unclear: beginning of word]]novskoye gold-ore deposit, which was worked before the revolution and mothballed for unclear reasons) and locally occurring rich placers, now largely exhausted (an example is the basin of the upper course of the Kirgitey River).

On the basis of the foregoing, it seems possible to recommend this area as a target for gold prospecting. In this regard, the following will be of increased interest:

1) the belt of direct contact with the eastern metallogenic zone (the Angara–Pit synclinorium);

2) areas with manifestations of polymetallic and antimony mineralization, which, under the conditions of the Yenisei Ridge, is a frequent “companion” of gold;

3) areas where rocks with a relatively elevated degree of metamorphism are developed (phyllites, sericite schists), since to a certain extent they may indicate proximity to an intrusion, in particular to an ore-generating one;

4) areas where dikes occur, especially those of acidic composition.

Since within this area of the Trans-Angara region the development of predominantly “blind” gold mineralization is assumed, the criteria listed should generally be regarded only as indicators of concealed ores. However, this by no means excludes the possibility of discovering deposits that crop out directly at the surface, especially given the widespread manifestation of block tectonics in this part of the Yenisei Ridge.