Mapping & Petrography Appendices · appendix-13
Petrography — Sheet 13
The QAP diagram transparently converts the BV modal framework-mineral proportions into an andesite classification. The plotted point is meaningful only after quartz, alkali feldspar and plagioclase are recalculated to 100 percent and after fine groundmass or altered material is treated consistently with the scheme.
SOURCE-LED TECHNICAL READING
Geological interpretation and evidential boundary
The QAP diagram transparently converts the BV modal framework-mineral proportions into an andesite classification. The plotted point is meaningful only after quartz, alkali feldspar and plagioclase are recalculated to 100 percent and after fine groundmass or altered material is treated consistently with the scheme. Analytical uncertainty should be propagated because a small counting change can move a point near a boundary, although this point appears well within the andesite field. The diagram corroborates the micrograph but does not independently verify mineral identification or sample representativeness. Its strongest use is reproducible nomenclature for the analysed clast, followed by comparison with additional clasts to test whether the coarse deposit is monomictic or polymictic.
- Source
- Private geological appendix archive · controlled source record
- Location in source
- Source-linked record
- Image quality
- HD
- Record ID
- appendix-13
