Strontium in plagioclase feldspars from four layered basic masses in Somalia

Abstract

The petrological and structural characteristics of four layered basic masses in Somalia are described. Sr contents of feldspars from three of the masses are similar for comparable An contents; Sr varies between 1000 and 1850 p.p.m. and tends to increase as An decreases from An₆₈ to An₄₈. In feldspars from the other mass Sr also increases with decreasing An content (An₇₄ to An₅₆), but is at a much higher general tenure (1650 to 2350 p.p.m.). It is concluded that the four masses were not all part of the same layered intrusion.