Liquid Immiscibility and Problems of Ore Genesis: Experimental Data

Resumo

The paper reports the results of an experimental study of phase relations and distribution of elements in silicate melt–salt melt systems (carbonate, phosphate, fluoride, chloride), silicate melt I – silicate melt II, and fluid–magmatic systems in the presence of alkali metal fluorides. Extraction of a number of ore elements (Y, REE, Sr, Ba, Ti, Nb, Zr, Ta, W, Mo, Pb) by salt components was studied in liquid immiscibility processes within a wide temperature range of 800–1250°С and pressure of 1–5.5 kbar. It is shown that partition coefficients are sufficient for concentration of ore elements in amounts necessary for the genesis of ore deposits. In a fluid-saturated trachyrhyolite melt, the separation into two silicate liquids has been determined. The partition coefficients of a number of elements (Sr, La, Nb, Fe, Cr, Mo, K, Rb, Cs) between phases L₁ and L₂ have been obtained. The interaction processes of a heterophase fluid in the granite (quartz)–ore mineral–heterophase fluid (Li, Na, K-fluoride) system were studied at 650–850°C and P = 1 kbar. The formation of the phase of a highly alkaline fluid-saturated silicate melt concentrating Ta and Nb is shown as a result of the interaction of the fluid with rock and ore minerals.