EFFECT OF GOLD-ACCOMPANYING ELEMENTS ON G OLD BEHAVIOR IN THE FE-S-AQUA-SALT SOLUTION SYSTEM AT 450 DEGREES-C AND 100 MPA

The interphase distribution and forms of gold occurrence in minerals a re studied by hydrothermal experiments in the presence of typical gold -accompanying elements: As, Se, and Te. It is shown that the geochemic al role of As and Se differs from that of Te: arsenic and selenium ten d to elevate the Au content in the fluid phase giving rise to the form ation of <<invisible gold>> in coexisting pyrite as the consequence of this elevation, whereas Te elevated the apparent distribution coeffic ient of gold between pyrite crystals and fluid phase. That is why As a nd Se could be considered as gold-guide elements which provide the gol d transfer as combined complexes, so these elements may be used as ind icators of gold ore deposits. High values of the apparent distribution coefficients of Au between pyrrhotite (magnetite) and fluid together with low gold contents in these minerals even if they occur in gold-be aring ore deposits shaw a rather different chemical conditions during crystallization of these minerals and gold-containing pyrite indicatin g low activities of Au-bearing species during crystallization of pyrrh otite and magnetite. Rather, the natural pyrite crystals with high con centrations of <<invisible gold>> might be formed from solutions with Au contents of about 3-7 ppm. The chloride complexes are unable to pro vide such high contents which, alternatively, could easily be provided by gold-guide elements, primarily As. It is confirmed that the format ion of <<invisible gold>> in minerals is affected by unstable intermed iate phases and compounds which contain gold-guide elements. The proce ss of invisible gold formation should be most effective under low temp erature conditions where the crystallization passes via intermediate p hases, under high supersaturations giving rise to development of cryst al microstructure.