Behavior of Pt, Pd, and Au During Crystallization of Cu-Rich Magmatic Sulfide Minerals

Experimental Modeling of Noble and Chalcophile Elements Fractionation during Solidification of Cu-Fe-Ni-S Melt

“…After dry grinding, the powdered sample was replaced into the ampoule, with an 8 mm diameter and a conical end, which was then evacuated and sealed. A scheme showing the experimental apparatus and the procedure of preparing the sample were described in detail in [18]. Crystallization was performed using the Bridgman method in a vertical two-zoned furnace, with a diaphragm, by lowering the ampoule with a homogeneous melt from the hot zone to the cold zone at a rate of 2.3 × 10 −8 m/s.…”

“…For the Noril'sk deposit, no less than two main types of zonality are observed, in one of which the fugacity of sulfur increases, and in the second, it decreases [1,2,10]. The possibility of several types of zonality is shown in the experiments on directed crystallization of Cu-Fe-Ni-sulfide melts [11][12][13][14][15][16][17][18][19] (The terms "directed crystallization" and "fractional crystallization" describe the process of gradual solidification of the melt in the absence of mixing in the solid ingot and complete or partial mixing in the melt. From the physicochemical point of view, when modeling the solidification of a cylindrical ingot in laboratory or industrial equipment, the term "directed crystallization" is more acceptable).…”

“…In [24], a hypothesis is presented about the pneumatolytic genesis of compounds of noble metals. Both hypotheses are based on the results of geochemical observations and on experimental data [1,2,4,10,[17][18][19][26][27][28][29][30][31][32][33][34][35]. Fundamental knowledge about the behavior of noble metals is contained primarily in the phase diagram of the systems related to this problem (see the review in [36][37][38][39][40][41]).…”

“…In this case, the composition of the samples is chosen by the experimenter. By contrast, in our works, we studied samples obtained by directed crystallization of melts of a given composition [11][12][13][14][15][16][17][18][19]. Usually, this method is applied in the case of gradual solidification of a cylindrical sample from one end to another.…”

“…The ingot is used for preparing genetically related samples, the composition of which is determined by the rules of directed crystallization. Thus, we simulated the formation of pyrrhotite-cubanite, pentlandite-bornite, and other mineral varieties of massive ore bodies from the Noril'sk deposit and also studied the behavior of ensembles of minor elements [11][12][13][14][16][17][18]33,42]. In particular, Cu-Fe-Ni sulfide melts with the following ensembles of impurities were crystallized by this method: of components were constructed, and phase and chemical compositions of inclusions containing PGE (drop-shaped included) were analyzed.Results of the geochemical and experimental studies described in the literature are insufficient for the verification of two hypotheses (magmatic and pneumatolytic) about the impurity mineralization of the Noril'sk deposits.…”