Local and regional controls on the lateral emplacement of the Ben Hiant Dolerite intrusion, Ardnamurchan (NW Scotland)

摘要

Sub-volcanic and related satellite intrusions record the delivery, storage and accommodation of magma before eruption. However, when several volcanic centres are in close proximity, the relationship between centre and satellites may be ambiguous. Here we examine the structure of the Ben Hiant Dolerite satellite intrusion, discuss its relationship with the Ardnamurchan Central Complex located 2 km to the northwest and explore the possibility of a genetic connection with the next nearest centre, the Mull Central Complex (~35 km to the southeast). Structural field observations and anisotropy of magnetic susceptibility (AMS) fabric analyses reveal that the Ben Hiant Dolerite was emplaced as a series of lobes in a sequence of stacked sheets. The AMS fabric data further indicate that the Ben Hiant Dolerite intruded laterally and may have been sourced from either the Ardnamurchan Central Complex or the Mull Central Complex. Testing either model and discriminating between these two possible source reservoirs remains an outstanding challenge. However, the potential implications of the lateral movement of magma over many 10's of kilometres between upper crustal magmatic centres suggests hidden complexities associated with volcanic plumbing systems that must be tested structurally as well as geochemically.