Hybridization of shoshonitic lamprophyre and calc‐alkaline granite magma in the early Proterozoic Mt Bundey igneous suite, Northern Territory

Abstract

The Mt Bundey igneous suite (1831 ± 6Ma) intrudes deformed and low‐grade metasedimentary rocks of the Early Proterozoic Pine Creek Inlier. The suite consists of a composite pluton of calc‐alkaline granite (Mt Bundey Granite) and shoshonitic syenite (Mt Goyder Syenite), and a swarm of spatially, temporally and probably genetically associated, K‐rich shoshonitic lamprophyre dykes. Grey, ovoid to tabular lamprophyric enclaves, up to about 1 m in length, are widespread within the syenite. The enclaves have the same mineralogy as, and similar mineral and whole‐rock compositions to, the lamprophyre dykes. These features, in conjunction with textural studies, imply that the enclaves represent lamprophyre magma injected into a partly crystalline syenite magma. Lamprophyre dykes, lamprophyric enclaves and syenite contain numerous, widely dispersed uralitized clinopyroxenite enclaves 0.5–5.0 mm in diameter, suggesting that magma mingling was preceded by hybridization of lamprophyric and granitic magmas. The syenite...