Illustrated Glossary- Lecture 5
| TOC | Lecture 1 2 3 4 a b 5 a b | Lab 1 a b c 2 a b c 3 a b 4 a b 5 a b| Glossary Table 1 2 3 4 5 Index |
VIEPS Deformation Microstructures Course Lab 5 -
Fibrous (vein/fringe) - crystals in a vein or pressure fringe that have a very high length/width ratio. All fibres are parallel and the fibrous shape is not related to the crystallographic habit or lattice orientation of the mineral. Common in calcite, but can also occur in other minerals such as quartz.
Elongate-blocky - crystals in a vein that are elongate, but not as extreme as in fibrous crystals. Crystals get wider in the growth direction as some crystals 'lose' in the growth competition. Common in crack-seal veins.
See the lecture notes for other terms, such as blocky, stretched & slicken-fibres.
Syntaxial vein - Vein with one growth surface in the middle of the vein. The fibres or elongate crystals started growing at the edge of the vein and are in continuity with the wall rock.
Antitaxial vein - Vein with two growth surfaces on the edge of the vein. The vein-forming fibres are usually of another mineral than the wall rock and there is no continuity with the wall rock. Usually there is continuity of fibres on both sides of the median plane where the fibres started growing.
Composite vein - Vein with two growth surfaces. The mineral growing in the middle between the growth surfaces grows in a antitaxial manner, whereas the mineral on the outside, between the wall rock and the growth surface grows syntaxially.
Ataxial or stretched vein - Vein without a localised growth surface or where the growth surface (crack) varies in position over time.
Syntaxial fringe - Fringe with the growth surface on the outside of the fringe (between fringe and wall rock). Often mineralogical or crystallographical continuity with the rigid object causing the fringe, hence the term 'syntaxial'.
Anitaxial fringe - Fringe with the growth surface between the rigid object and the fringe. Possible continuity with the wall rock but no continuity with the object, hence the name 'antitaxial'
Displacement-controlled growth - The growth direction of fibres is determined by the opening trajectory.
Face-controlled growth - The growth direction of fibres is determined by the shape of the rigid object, with the fibres growing perpendicular to its surface.