Abstract

The generation of Large Igneous Provinces (LIPs) – huge outpourings of lavas associated with tectonic rifting – is a hotly debated topic with competing models variously invoking hot mantle plumes, insulative heating by supercontinents or edge driven convective instabilities. Mantle temperature and its temporal variation during LIP magmatism is key to distinguishing between these different models. Despite this, there are as yet no detailed stratigraphically constrained studies of mantle temperature through a LIP succession.

To address this, we have applied olivine-spinel and melt-only thermometry to constrain mantle potential temperature through a sequence of lavas from Co. Antrim, Northern Ireland, formed during the earliest expression of the North Atlantic Igneous Province. Mantle potential temperature derived from olivine-spinel and melt-only methods give consistent temperature ranges of 1374–1472°C and 1403–1521°C, respectively. Notable both temperature records indicate significant (100-120°C) variation in melting temperature over a relatively short stratigraphic during earlier forming magmas and much less variation in later formed magmas, suggesting initial instability or pulsing which stabilised with time.

Variability in melting temperature is mirrored by proxies for crustal and volcanic processes; Ni contents of olivine are elevated (