CESIUM VARIETY OF ULTRARARE-METAL GRANITE PORPHYRY (ELVAN)

Abstract

In topaz-bearing granite porphyry and microgranite porphyry dikes found in a rare-metal dike belt there was found a group unusually high in rate elements, chiefly rare alkalies. Apatite, topaz and, less commonly, talc pseudomorphs after pyroxene account for 2 to 7 percent of these phenocrysts, whose total amount usually ranges from 65 to 75 percent. In thin selvages and pinching-out patches, the phenocrysts decrease in size to 0.5 cm and in number to 40 percent. In muscovite, the concentration levels of Li, Rb and Cs are 0.1133, 0.1567 and 0.0077 percent, respectively (average of three analyses), i.e., two to seven times below the clarkes for granite muscovites. In the quartz there are primary crystallized melt inclusions, clustered along its growth zones or azonally and with homogenization temperatures of 640° to 780°C.