Abstract
The Etive complex, one of the Caledonian ‘Newer Granites’ of Scotland, is a ring complex of Devonian age, ranging in composition from pyroxene-diorite to leucogranite. Six samples, representing the major rock units in the southern parts of the Etive complex were chosen for mineral chemical studies and for estimation of the pressure and temperature conditions of magmatic crystallisation. Application of Al- in-hornblende barometry and crossite contents of amphiboles indicates a pressure <3 kbar for the intrusion, in good agreement with published independent pressure estimates of ∼2 kbar from mineral equilibria in metasedimentary hornfelses in the Etive thermal aureole. Thermometry, using ternary and binary feldspar systems, yields low temperatures, which probably reflect late-stage, post-magmatic re-equilibration of these minerals. Several geothermometers have been applied to the Quarry Diorite, the outermost intrusion of the complex. The highest temperature for the rocks comes from orthopyroxene–clinopyroxene solvus thermometry, and is ∼1000 °C; this is interpreted to reflect the initial crystallisation of the diorite magma immediately after its emplacement. The maximum temperature from hornblende-plagioclase thermometer is ∼816 °C, which probably reflects late-stage crystallisation of the magma.
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