Abstract

The Ashuanipi complex of the Archean Superior Province consists of an older sequence of sedimentary rocks cut by sills and goblet-shaped intrusions of the Desliens igneous suite (DIS). The complex was regionally metamorphosed to granulite facies and subsequently intruded by peraluminous granodiorite batholiths. Tonalites of the DIS contain characteristic < 2 cm inclusion-filled orthopyroxene crystals of probable igneous origin, variably recrystallized and overgrown by garnet, biotite and blocky orthopyroxene that suggest metamorphic PT conditions of 0.5–0.62 GPa and 750–850 °C. Andesine in tonalite contains abundant drop-like quartz inclusions. Inclusion-filled pyroxene and plagioclase are both inferred to have nucleated on partly resorbed quartz and plagioclase grains within a melt. Similar poikilitic textures characterize subordinate leucotonalite, diorite, gabbro, and pyroxenite, which together with tonalite make up the DIS. Some of the petrological characteristics of the suite are unusual, but known from other regions: (i) some felsic magmatic rocks in the southern Sierra Nevada and Barrington Tops (Australia) batholiths contain primary orthopyroxene; (ii) goblet-shaped plutons are common in orogenic belts, and tonalites with this geometry occur within a sedimentary succession in the Trinity Alps of California; (iii) orthopyroxene oikocrysts characterize parts of the Bjerkreim–Sokndal lopolith of southwestern Norway.

You do not currently have access to this article.