High-temperature pyroxenes from an ironstone at Scourie, Sutherland

Abstract

SummaryThe coexistence of clinopyroxene (Wo18 En32 Fs44 Rh06) and pigeonite (W08 En35 Fs50 Rh07) in a meta-ironstone from Scourie is described. By comparison with experimental data, the temperature at which they were in equilibrium is estimated as at least 1000°C. The exsolution history of the two pyroxenes is documented. As the rock is an unambiguous metasediment, its presence among granulite facies rocks containing evidence of metamorphism at pressures greater than 10 kbar constrains at least part of the Scourie complex to a supracrustal origin and indicates that tectonic processes of burial were operative in the late Archaean.