Presented paper

IMWA2019 Students work

Hydrogenic Processes Of Authigenic Mineralization Of Native Gold In The Ural Placers

Kovrizhnykh, Svetlana Borisovna (1); Abroskin, Dmitry Nikolaevich (2); Naumov, Vladimir Aleksandrovich (3)
1: Perm State National Research University, Perm, Russia, Russian Federation; 2: UralStroyProgress; 3: Natural Science Institute at the Perm State National Research University

The natural processes of the formation of a "new" authigenic native gold are rather widely distributed, however, they are difficult and ambiguous to identify. The increased content of dissolved gold is found in weakly acidic, neutral or weakly alkaline hydrocarbonate and sulphate waters. The increased acidity of solutions pushes the gold migration forward.

The precipitaition of gold is controlled by geochemical barriers: oxygen, reducingsulfate, carbonate, alkaline, carbon, sulfide, evaporative, cryogenic, sorption, or their combinations.

The authigenic gold precipitated from solutions is represented by gold pellicles passively growing on the detrital particles, and kefilite borders.

Authigenic pellicles and microсrusts cover the surface of detrital particles of both rocks and any various minerals. The native gold is formed not only during the hydrothermal process, but also authigenic pellicles and shells grow under hot climates conditions in the tropical zone and during the freezing of "cold" waters under exogenous conditions. In gold-containing solutions, the concentration of the metal is increased and gold is precipitated in the form of metal pellicles and aggregates on the surface and in the intergranular space of the precipitates.

The hot epochs of crusts and gold placers formationon The Urals were manifested in the Mesozoic placer formation cycle. The gold placers of this time are characterized by the increased productivity. The significant role of the influence of the evaporation barrier, enlargement and the formation of clastogenic gold particles is probable. With seasonal freezing of alluvial sediments in the Quaternary and in connection with the stages of glaciation and interglacials, the authigenic processes of mineral formation and the gold crusts’ and scurfs’formation have been probably also intensified.

The parallel geochemically related process of formation of crusts and iron scurfs and manganese hydroxides is the result of surface interaction of auriferous phases with ore solutions, enriched with these elements. The iron-manganese phases form scurfs and crusts on gold, act as a cement formingthe larger aggregates. Such compounds are widely spread in the man-made formations (sandstones, gravelites and conglomerates), also noted in the man-made placers of the Amur region and the Far East, at the Urals, Canadasites.

The knowledge and account of natural processes of authigenic neoplasm of gold from “ore-containing technogenic” solutions forming during the working-out of sulphide ore deposits will allow to involve man-made under-ore and intra-dump waters in the technological process of their enrichment and purification while ensuring the environmental safety of mining operations.