The mechanism of native gold mineral aggregate formation

The coarsening of the particles in a wide temperature range with the attraction of the theoretical and practical methods of studies was analyzed for the minerals of natural gold and gold-silver alloys. The methods of thermodynamic and chemical analyses determined the parameters of this process: kinetic features and the valid concentrations of gold and silver. The deep difference between the energy states and the manifested properties of chemical behavior for the surface and inner layers of atoms in these particles was shown. The research used a large number of reference materials, parameters of thermodynamic states, data of the studies of other authors and of the present authors, who studied these states in the manifestations of the gold-ore mineralization of the Upper and Middle Amur Region. The presence of a dual electrical layer on the surface of these particles is confirmed; its geometric dimensions are estimated, including the thermodynamic and chemical parameters of the states of the atoms of gold and silver in them. The dual electrical layer consists of the negatively charged ions of oxygen O and positively charged ions of the noble metals Ag+, Au+, Au +. It is shown that it is the surface atoms that were active elements in the process of coarsening of the gold silver particles; the stages of this process were described. The process is limited by the geometric parameters of the joined particles and, additionally, by kinetic restrictions. A mechanism of nucleophilic aggregation of native gold minerals based on the interaction of the dual charged surface layers was offered. The reactions of aggregation in standard conditions for conducting are thermodynamically possible for gold and forbidden for silver; in the interval (433-1336 K) they are possible for both metals. The reaction rate constant is limited by the probability of a collision of two native gold particles; it grows sharply with an increase in the temperature. Reactions are also influenced by the physical and chemical conditions (Eh, pH) of the natural geochemical environment, they control the morphology of the aggregates. The intergrowth lines are contrasting in roentgen graphic studies as a result of the adsorptive surface contamination by light and heavy chemical elements. This mechanism of native gold mineral aggregation (600-999 %) is thermodynamically possible in natural environment at the maximum temperature (433 K), and is possible in a temperature interval (433-1336 K) for crystals with the purity of gold (100-999 %).

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