The Formation of Granite Magma Chambers in the Mourne Mountains, Northern Ireland

Sammanfattning: The Mourne Mountains situated in County Down, Northern Ireland, mainly consists of solidified granite magma chambers that intruded ~ 56 million years ago into the surrounding greywacke. How granite magma chambers are emplaced in the crust has for years been a debate amongst scientist of volcanology, and is referred to as the ‘space problem’ debate. There are two principle theories in how the granite magma chambers in the Mourne Mountains were formed; either the magma chambers were forcefully emplaced by doming the greywacke host-rock or the magma chambers were emplaced by passively by magma filling the space over a subsiding block of host-rock. In this study rock samples from Luke’s Mt. dyke has been investigated with anisotropy of magnetic susceptibility (AMS). AMS measures the orientation of magnetic minerals in a rock sample and thereby shows the magma movement. These measurements indicated that the magma in the studied Luke’s Mt dyke flowed into the connected magma chamber and thus are a feeding ring-dyke. This implies that the granite bodies of the Mourne Mountains were emplaced by a passive process like cauldron subsidence.