DOI: 10.1594/pangaea.820353
title: AMS and EBSD maps of rock salt - lamprophyre dyke contact zone, Loule diapir, Algarve basin, Portugal

description: 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.
description: The low field anisotropy of magnetic susceptibility (AMS) was measured with a MFK1-FA Kappabridge (Jelínek and Pokorný, 1997) in the field of 200 A/m and for a frequency of 976 Hz (Institute Dom Luiz - Univ. Lisbon). File columns: sample Name, rock type, distance from dyke centre, magnetic field in A/m (Field), operating frequency (Freq.), measured bulk magnetic susceptibility (Km), anisotropy factors L, F, P, Pj, T, U (for explanation please see Jelínek, 1981) , orientation of principal magnetic susceptibilities (orientation of principal axes of magnetic susceptibility tensor K1&gt;K2&gt;K3) dec -declination (0 - 360°), inc - inclination (0 - 90°) in geographic coordinates (North = 0, horizontal = 0), K11- K13 - description of symmetrical AMS tensor.The Loulé salt diapir in the Mesozoic-Cenozoic Algarve basin was chosen as case study to show the relationship between mafic dyke emplacement and host-rock salt deformation. The studied lamprophyre dyke is 3m thick, strikes N310 and dips 80º to the NW. In both margins of the dyke, the texture is aphanitic with devitrified volcanic glass and abundant euhedral as well as skeletal xenocrysts of olivine and olivine xenoliths, with serpentinized olivine xenocrysts at the SE margin. The dyke centre shows subophitic texture of plagioclase laths, needle crystals of amphibole and large anhedral crystals of biotite, with high amount of volcanic glass. The olivine xenocrysts are significantly less abundant in the dyke core. Only brittle structures have been observed in the dyke itself. Fractures within the dyke are filled with halite. Within the host-rocks close to the SE dyke margin, angular fragments of lamprophyre of various sizes can be observed. Samples were collected in rock salt and within and around a lamprophyre dyke in the Loulé Mine. A profile across the host-rock salt and dyke was sampled in detail. The salt rock was sampled on the NW and SE sides of the dyke, between a distance of 5 to 220 cm and 10 to 75cm of dyke margins, respectively. The dyke was also sampled along a complete cross-section. Crystalographyc prefered orientation maps of salt rock (SaltEBSDmaps.zip) in Channel text files *.ctf obtained using NORDLYS II (HKL Technology) EBSD system mounted on TESCAN Vega scanning electron microscope (Institute of Petrology and Structural Geology of the Faculty of Science at Charles University in Prague) in the mapping mode with 10 µm step size. The .ctf file is a text file containing header with information about mineral phases measured and the data consists of phase orientation in each point measured. The .ctf file can be read by commercial HKL Technology (Oxford Instruments) software or better using the MATLAB® Toolbox for Quantitative Texture Analysis (MTEX) (Bachmann et al., 2010; 2011; https://code.google.com/p/mtex/) under GNU GPL v2 licence.
description: Supplement to: Machek, Matěj; Roxerová, Zuzana; Závada, Prokop; Silva, P F; Henry, B; Dedecek, P; Petrovský, E; Marques, F O (2014): Intrusion of lamprophyre dyke and related deformation effects in the host rock salt: A case study from the Loulé diapir, Portugal. Tectonophysics, 629, 165-178