Some pecularities of physical properties of the Kukulbei granitic massive with reference to their ore manifestation

The granites of the Kukulbei complex belong to the youngest mesozoic intrusive formations of south-eastern trans-Baikal. They occur as small blocks composed of acid and extremely acid biotitic and leucocratic granites that vary greatly in their structural features. The granites are spatially and paragenetically (and in some gases genetically) linked with numerous deposits of rare metals and fluorite. A variation in the type of ore mineralization is found to be linked with specific blocks; the variation is expressed as a preponderance of one or two metals with a marked subordination of others. A typical petrographical feature of Kukulbei granites is the high general radioactivity (18 - 25 mr/hr). It was established that the type of rare-metal mineralization depends on the nature of the radioactivity of the granites. For granites with a significant preponderance in their make-up of radioactive uranium and reduced concentrations of thorium and potassium, high concentrations of tantalum niobates are typical; where potassium and thorium play a greater role in the radioactivity, tungsten mineralization predominates, together with uranium. Despite some admixture of rare-metal mineralization, the types mentioned are typically quite clearly isolated. (V.Ya.)