SEQUENCE OF SALT SEPARATION AND REGULARITY OF SOME TRACE ELEMENTS DISTRIBUTION DURING ISOTHERMAL EVAPORATION(25℃)OF THE HUANGHAI SEA WATER
Chen Yuhua Institute of Mineral Deposits, Chinese Academy of Geological Sciences
Experimental study of sea-water in the process of isothermal evaporation is very im-portant to further study of mechanism of halite and potash salts formation. Our water sam-ples were taken from the Huanghai Sea, the composition of which is nearly the same as thatof the ocean water. The samples were examined under 1 atmosphere at 25℃. Our experiments make sure that there should be seven stages in salt separation duringthe evaporation of normal sea-water. The sequence of salt mineral precipitation is as follows:aragonite, gypsum, halite. epsomite, sylvite, carnallite, bischofite. The primary precipitateof carbonate at the first stage is aragonite and not calcite, as suggested by M. G. Valyashko.The experimental study also affirms that epsomite is the only Mg-bearing sulphate whichcan be separated during static isothermal evaporation of normal sea-water at 25℃. This re-sult is also different from the conclusion obtained by N. S. Kurnakov, who determined thathexahydrite should be crystallized in the same condition. The geochemical behaviour of bromine, rubidium. lithium, strontium and boron hasbeen studied in the concentration process of sea-water. The examination has defined variousregularities of these elements in the process of salt formation and their function in the studyof salt deposits. These elements may be divided into three groups. During the normal sea-water concentration strontium is concentrated in brine till the later stage of sylvite precipi-tation. Strontium turns into precipitate by ion exchange, not in form of celestite crystalliza-tion.