Аннотация:LIQUID IMMISCIBILITY – IMPORTANT MECHANISM OF ORE ELEMENTS CONCENTRATING IN MAGMGTIC PROCESSES
NATALIYA SUK
Institute of Experimental Mineralogy RAS, Chernogolovka, Moscow district, Russia
At the present time study of process of selective concentrating of ore matter in fluid-magmatic systems continues to be relevant.
According a number of experimental data magmas are concentrators of ore metals comparative equilibrial water fluids of different compositions. Data of study of maximum ore components (REE, Y, Nb, Ti and others) solubility in silicate melt evidence about their low content which generally does not exceed first percents (depending on melt composition). Such contents are insufficient for formation of reach deposits by direct crystallization from the melt.
Liquid immiscibility allows to explain mechanism of ore matter concentrating in magmatic process from initial low to economic concentration.
In layering silicate-salt systems selective concentration of different ore elements depending on salt type has been shown. High efficiency of phosphate extraction of REE, Sr, Ti, Nb, Ta, W, Sn; chloride extraction of W; sulphate and carbonate extraction of Sr and Ba has been experimentally evidentiated.
Consideration of layering intrusions in respect of their ore-bearing leads to conclusion that poor in silica (urtite and et. al.) horizons are most productive in respect to different types of mineral deposits (for example, in respect to apatite in Khibine alkaline massif and in respect to loparite (Ni-Nb) ores in Lovozerskiy alkaline massif).
Fluid-magmatic systems in which high concentrating salt melt separating from aluminosilicate melt can form own nonsilicate rocks (for example, carbonatites or apatite ores) exist.
Layering in silicate-phosphate system experimentally obtained schematically model segregation of apatite-urtite horizon in nepheline-syenite Khibine massif; concentration of ore elements as a result of titanate-silicate liquid immiscibility apparently has determinative significance for formation of rich REE-Nb (loparite) deposits at magmatic stage; silicate-carbonate liquid immiscibility and alkaline-calcareous splitting of carbonate melts contribute to REE concentration in carbonatite melt and to formation of carbonatite deposits of REE in relation with alkaline (agpaitic) magmatism.
So, experimental results evidence about important role of liquid immiscibility in ore matter concentrating at magmatic stage as a result of which ore deposits and mineralization of different types can form. These data allow considering liquid immiscibility as effective mechanism of concentrating of ore elements in magmatic systems.
