The Strontian Intrusive Complex: Petrography, Thermobarometry and the Influence of Titanite on Residual Melt Chemistry

Abstract Although the evolution of residual melts in magmatic systems controls their eruptability and ore-forming potential, compositions are obscured plutonic rocks by a protracted near-solidus absence interstitial glass. Here, we trace melt from Strontian Intrusive Complex, Scotland, using element chemistry amphiboles, titanites which intergrown with amphibole rims. Laser ablation mapping reveals an abrupt change certain elements rims, sharp increases Eu/Eu* Sr/Y, decreases rare earth elements, Ta, Nb, Ta/Nb ratios. Core-rim variations these titanite show same as amphibole, but more gradual. By reconstructing crystallisation sequence magmas textural observations thermobarometric estimates, determine that cores crystallised prior to saturation, rims simultaneously titanite. Using composition mineral phases modal abundance rock, comparison whole-rock chemistry, hosts majority high field strength budget rocks. We therefore propose onset had profound effect on late-stage at Strontian, were inherited subsequent titanites. This is supported Rayleigh fractional modelling, demonstrates cannot be explained without influence saturation element-rich represents significant geochemical event petrogenesis intermediate silicic magmas. has implications for provenance studies attempt reconstruct bulk rock compositions, those minerals crystallise can driven significantly different host magma accessory phase crystallisation.