Distribution of molybdenum,uranium, copper and other elements in northwestern spurs of North Tien Shan

A still undetermined general principle is clearly expressed in the periodicity of concentration coefficients of nearly all chemical elements in igneous rocks (fig. 14). Clarke concentration of Mo, U, Cu is correlated with the age and the composition of igneous rocks: in intrusive complexes, Mo and U increase, but Cu decreases with the age; Mo and U are higher in acidic rocks; Cu is higher in basic rocks. Subalkalic rocks and margins of acidic intrusions are enriched with Mo, U, Cu, particularly where feldspar-quartz metasomatites are abundant. During magmatism, the build-up of U in acidic rocks is more rapid than of Mo. The behavior of the elements, as ascertained, may help orientation in prospecting for Mo, whose deposits are known to be associated with certain metasomatites. - -V. P. Sokoloff.