Intrusion of lamprophyre dyke and related deformation effects in the host rock salt: A case study from the Loulé diapir, Portugal

• We studied the rock salt–lamprophyre dyke contact zone.
• AMS, microstructural, CPO, paleomagnetic and heat transfer studies were performed.
• Magnetic fabric of the dyke itself is still related to magma flow during intrusion.
• Salt structure and AMS records dyke intrusion, diapir ascent and later reworking.

A rock salt–lamprophyre dyke contact zone (sub-vertical, NE–SW strike) was investigated for its petrographic, mechanic and physical properties by means of anisotropy of magnetic susceptibility (AMS) and rock magnetic properties, coupled with quantitative microstructural analysis and thermal mathematical modelling. The quantitative microstructural analysis of halite texture and solid inclusions revealed good spatial correlation with AMS and halite fabrics. The fabrics of both lamprophyre and rock salt record the magmatic intrusion, “plastic” flow and regional deformation (characterized by a NW–SE trending steep foliation). AMS and microstructural analysis revealed two deformation fabrics in the rock salt: (1) the deformation fabrics in rock salt on the NW side of the dyke are associated with high temperature and high fluid activity attributed to the dyke emplacement; (2) On the opposite side of the dyke, the emplacement-related fabric is reworked by localized tectonic deformation. The paleomagnetic results suggest significant rotation of the whole dyke, probably during the diapir ascent and/or the regional Tertiary to Quaternary deformation.