Institute of Geophysics of the CAS, v. v. i.

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Dyke – rock salt interaction (Loulé salt diapir, Portugal)

Dyke – rock salt interaction (Loulé salt diapir, Portugal)

The 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 reveald, two following 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 palaeomagnetic results suggest significant rotation of the whole dyke, probably during the diapir ascent and/or the regional Tertiary to Quaternary deformation.

 

 

Block diagram showing the most important findings and interpretations of AMSBlock diagram showing the most important findings and interpretations of AMS, microstructural analysis and thermal modeling. Operating deformation mechanisms: SP+DC - solution precipitation + dislocation creep, DH - Fluid overpressure driven dilation hardening. Δσ - differencial stress. The geographic orientation of the block diagram is marked by the compass rose