Rare-earth, metal, and phosphorite ores of Caradocian stage, northeast portion of Central Kazakhstan
High concentration of a number of metals, associated with feeder reservoir rocks emplaced at shallow depths, and the volcanic rocks which these produced, is discussed. The intruded feeder reservoirs tend to occupy faults which branch out from regional master faults at high angles (nearly 90° in the usual case). The enrichment of the intrusives, country rocks, and extrusives is taken to be consequent upon segregation processes in larger reservoirs situated considerably deeper in the crust. The combination of intrusive and extrusive processes leads to high concentrations of lead, zinc, molybdenum, and other metals in granite porphyries and in contact-metamorphic zones. It is noted that the concentrations of lead and zinc vary in opposite senses in acid extrusives. M. E. Burgunker.