The magmatic systems under consideration are the final derivatives of mantle and crustal ultrabasic-basic-plagiogranitic series that resulted from the effect of deep-seated paleodiapirs. Silica-poor intrusions productive for gold are characterized by the predominance of sodium over potassium (0.5-2.5 wt %) and chlorine over fluorine (Cl/F = 2-50), and by the presence of sulfur in the fluid phase. The two compositionally contrasting rock types - diorite and plagiogranite - bear pronounced evidence of autometasomatic alterations. The calculated coefficients of gold distribution between magma and solid phases of crystallizing melts are estimated at (1.3-2.5) : 1 for tholeiitic magmas and (1-5.5) : 1 for ore-forming granitoid magmas. Under subsolidus conditions, the coefficient of gold distribution between solid and fluid phases is 1 : (3-21) for tholeiitic magmas and 1 : (53-290) for granitoid magmas. An increase in sulfur potential in the mineral-forming systems gave rise to the accumulation of chalcophile elements and gold in suitable geologic structures.
|Состояние||Опубликовано - мая 1997|
ASJC Scopus subject areas
- Geochemistry and Petrology