Sukhoy log gold deposit and possible prospecting for ores on its flanks
Authors: Nekrasov E. M. , Dorozhkina L. A. 
Published: November 2020

Background. Experimental exploitation of ores from the Sukhoi Log deposit has shown that its geology and structure requires elucidation.

Aim. To study the geology and structure of the Sukhoi Log deposit and to determine the main mineralisation patterns in the plan, on the flanks and at depth. This information can be useful when mining gold both directly at the deposit and when prospecting new deposits on its flanks.

Materials and methods. The existing maps, diagrams, sketches and block diagrams describing ore bodies and their behaviour in plan and at depth were used. A new structural layout of mineralisation at the Sukhoi Log deposit, both on its flanks and at depth was built.

Results. The gold mineralisation in the Sukholozhskaya and Verninsko-Nevskaya ore-bearing areas is controlled by various elements of the fracture structure. At the same time, in the Sukholozhskaya area, the mineralisation is confined to a thick zone of a sublatitudinal shingled thrust-fault zone, in places accommodating a narrow strip of small faults, slip planes and fracturing in the northwestern direction. The fracture strip intersects sub-latitudinally laying Riphean argillaceous-shale rocks of the Khomolkhin formation approximately in the middle part of the field. The shingled thrust-fault zone accommodates the fissure faults, which open during mineralisation of the north-west extension, and flattens out. Its thickness in some places reaches 130 m. In the curved and flattened thrust interval, an ore gold-arsenopyrite-pyrite-quartz formation is localised, morphologically resembling a “thick pillow” with a thickness of 130 m. It bends and gently plunges in the north-north-east direction. The bulk of gold reserves is contained in this ore formation. The ores of the vein-disseminated type, veinlet and vein formations are the richest formations. Between them, the dissemination of gold-bearing pyrite and subordinate arsenopyrite is always manifested. The boundary of industrial mineralisation is determined by the density of the interveinous ore.On the western flank of the deposit, within the bounds of another — Ugakhan — deposit, vein and vein gold-quartz-pyrrhotite ores are found at a deeper level. Here, the search for Sukholozhsky pyrite-quartz ores (if they even existed) is not promising, since they were eroded long time ago, and the liberated gold was concentrated in placers. Prospecting is promising only along the Bezymyanny ore-controlling fault, which directly limits the western flank of the Sukholozhskoye deposit.The mineralisation of the Verninsk-Nevsky area is controlled by the Verninsky Fault of the east–north-east extension and separated by a series of single feathering ore-bearing overthrust zones of the east-west extension. To the east, this mineralisation gradually decreases. The search for the Sukholozhsk type ores is more promising on the eastern side of the Nyrli river, 2 km east of the fault of the same name and 7 km north of the Verninskoye deposit near a small, poorly explored area with commercial gold mineralization, marked on the deposit map with a sign TM.

Conclusion. The main geological and structural laws of the localisation of gold ores were determined, which could be useful when conducting exploration works on the flanks of the deposit.