The shoshonite association: A review

The absarokite‐shoshonite‐banakite series described from Yellowstone Park by Iddings and the ciminite‐toscanite series described from western Italy by Washington are compared. In both regions these rocks are associated with leucite‐bearing rocks, potassium‐rich trachytes and with andesitic rocks with above average potassium. A similar association of rock‐types is described from Indonesia and several other regions including the Rift Valley of Africa where, at Bufumbira, Holmes & Harwood have described members of the absarokite‐shoshonite‐banakite, potassium trachytes and leucite rocks. It is concluded that the absarokite‐shoshonite‐banakite series and the ciminite‐toscanite series are parts of a single rock association here called the shoshonite association. Intrusive members, such as monzonites, are also briefly discussed. The relation of the shoshonite association to the tholeiite, alkali basalt, calcal‐kaline and carbonatite associations are examined and an attempt is made to relate these to tectonic events. Rock names are recommended for both extrusive and intrusive members of the shoshonite association, the chemical characteristics of each rock‐type are tabulated.