HT-fabrics in a garnet-bearing quartzite from Western Portugal: geodynamic implications for the Iberian Variscan Belt
Palabra(s) clave:
garnet-bearing quartzite, Iberian Variscan belt
Fecha de publicación:
Editorial:
Wiley
Citación:
Descripción física:
Resumen:
The study of a garnet-bearing quartzite from a major suture zone in Iberia reports an unusual high-T fabric. Quartz c-axis patterns were plotted using shaped garnet as reference axis for the finite stretch (X-axis). The pole figures are characterized by a dominant single maximum around X together with other point maxima along the XY plane (mylonitic foliation). These patterns suggest that dominant <c> prism slip and subordinated <a> prism slip operated during quartz plastic deformation in agreement with P–T conditions for syntectonic garnet growth (4–5 kbar and 700 ± 50 C) and, pre-dating the well-known (late) Variscan D1 event (<6 kb and 600 ± 30 C). The geotectonic framework suggests that the fabrics were formed along the western shear margin of the Ossa-Morena Zone during the early stages of the Variscan orogeny.
The study of a garnet-bearing quartzite from a major suture zone in Iberia reports an unusual high-T fabric. Quartz c-axis patterns were plotted using shaped garnet as reference axis for the finite stretch (X-axis). The pole figures are characterized by a dominant single maximum around X together with other point maxima along the XY plane (mylonitic foliation). These patterns suggest that dominant <c> prism slip and subordinated <a> prism slip operated during quartz plastic deformation in agreement with P–T conditions for syntectonic garnet growth (4–5 kbar and 700 ± 50 C) and, pre-dating the well-known (late) Variscan D1 event (<6 kb and 600 ± 30 C). The geotectonic framework suggests that the fabrics were formed along the western shear margin of the Ossa-Morena Zone during the early stages of the Variscan orogeny.
Patrocinado por:
This study was supported by grants from the TECTIBER and MODELIB/FCT projects POCTI/35630/CTA/1999 (PEF, JM, AR), Centro de Geologia/UP (FSB, HIC), DGE 95/PB1052 project (FJF) and PRAXIS XXI/FCT (BD/2633/93-RN; SFRH/BPD/3641/2000) scholarships (HIC).
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