Structures in metamorphic rock - #6
During metamorphism, this migmatitic gneiss rock experienced partial melting owing to extreme heat and pressure, and was chemically (and mineralogically) segregated into felsic (light: quartz and feldspar) and mafic (dark) layers. These layers (about 1-5 cm wide/thick) were subsequently tightly folded, with probable shearing (layer-parallel deformation) and stretching along the fold limbs, resulting in discontinuous layers of uneven width/thickness.
For other similar geological explanations of this rock, see the previously posted photos in this series, in my "Geology in building stone" album.
C. J.R. Devaney
Structures in metamorphic rock - #6
During metamorphism, this migmatitic gneiss rock experienced partial melting owing to extreme heat and pressure, and was chemically (and mineralogically) segregated into felsic (light: quartz and feldspar) and mafic (dark) layers. These layers (about 1-5 cm wide/thick) were subsequently tightly folded, with probable shearing (layer-parallel deformation) and stretching along the fold limbs, resulting in discontinuous layers of uneven width/thickness.
For other similar geological explanations of this rock, see the previously posted photos in this series, in my "Geology in building stone" album.
C. J.R. Devaney