BEHAVIOR OF ORE ELEMENTS (W, SN, TI, AND ZR) IN LAYERED IMMISCIBLE SILICATE-SALT SYSTEMS

Immiscibility of phosphate and chloride salt melts with model silicate melts, the composition of which was determined by mixtures of such ro ck-forming minerals as albite, diopside, and K-feldspars, was experime ntally studied, along with the behavior of ore-forming elements (W, Sn , Ti, Zr) during the initiation and development of liquid immiscibilit y. The latter resulted in splitting the studied systems into silicate and salt phases, which composed drops or layers. The experiments were carried out in high gas-pressure equipment. Each experiment lasted six hours at T = 1200-1250 degrees C and P = 2 kbar and ended with quench ing. We established that in both the phosphate and chloride systems, t he silicate glass is depleted in W and the salt enriched in it. The sa lt phase contains segregations even richer in W; the origin of these s egregations was presumably related to the crystallization of W compoun ds. This notion is confirmed by the occurrence of scheelite crystals i n the salt layer of the silicate-chloride systems with diopside. Ti wa s predominantly extracted by phosphate melts. Ti compounds also crysta llized in the salt melts, but less actively than W phases. In the sili cate chloride systems, Ti was accumulated in the silicate melts, and Z r behaved in silicate-salt melts similarly to Ti. The behavior of Sn w as examined in silicate-phosphate systems; this element exhibited no c ontrasting distribution, and its contents in the phosphate and silicat e melts were similar. The regularities thus obtained can be utilized i n studies of the genesis and ore potential of layered massifs.