Multi-scale strainfield analysis using geostatistics: Investigating the rheological behavior of the hot Variscan crust of the Pyrenees (Axial Zone)

• Published in: Journal of structural geology 2018-11, Vol.116, p.114-130
• Main Authors: Cochelin, Bryan, Gumiaux, Charles, Chardon, Dominique, Denèle, Yoann, Le Bayon, Benjamin
• Format: Article
• Language: English
• Subjects: Earth Sciences; Hot orogen; Kriging interpolation; Sciences of the Universe; Strain partitioning; Tectonics; Transpression; Variogram analysis
• ISSN: 0191-8141; 1873-1201
• DOI: 10.1016/j.jsg.2018.07.024

The present study provides a quantitative way to analyze and interpolate strainfields from ductile fabric field measurements using geostatistics. Based on variogram analysis and kriging interpolations, the developed methodology allows computing automatic cleavage and lineation trajectory maps at different scales from a same field structural dataset. For the example provided by the hot Variscan crust of the Pyrenees, the analysis of cleavage/stretching lineations orientation and kinematic data document pure shear conditions recorded during convergence. Strain was vertically partitioned between an upper crust submitted to homogeneous thickening responding to N-S (orogen-normal) shortening and a hot and partially molten mid-lower crust affected by horizontal longitudinal (orogen-parallel) flow. The emplacement of plutons and gneiss domes generated heterogeneities in the upper crust and induced strain localization into steep anastomosed transpressional shear zones flanking those structures. The results show that geostatistics applied to structural geology are powerful tools for retrieving tectonic regimes of large orogenic segments by identifying and quantifying perturbations in the strainfields induced by protracted and potentially complex tectonic histories. The variogram analysis also gives first order clues to evaluate whether the considered structural domains underwent single continuous ductile or polyphased brittle-ductile deformation. •Spatial orientation variability of schistosity planes is quantified by variograms.•Building of quantitative regional and local strainfields using kriging interpolations.•The analysis of fabrics and kinematic data documents strain partitioning patterns.•Variogram analysis allows deciphering continuous from polyphased deformation.