Syenogranite
Granite with Q 20–60% and plagioclase 10–35% of total feldspar.
Language and route: IUGS systematic compound: syenite + granite. IUGS systematic compound: syenite + granite
Literal gloss: syenite-like feldspar balance + granite
The name and its history
IUGS systematic terminology; first individual coinage not claimed · Not securely established
- What does the word literally mean?
- Literal naming sense: syenite-like feldspar balance + granite. Immediate language/formation: IUGS systematic compound: syenite + granite. This compound preserves a misleading old geographical name inside an accurate modern quantitative category.
- What did the original author mean?
- A systematic subdivision of the granite field identifying rocks comparatively rich in alkali feldspar.
- Why was the name needed?
- Older granite labels concealed the relative importance of alkali feldspar and plagioclase.
- What evidence supported the original concept?
- Quantitative modal mineral proportions, not proximity to ancient Syene.
- How has geology changed the concept?
- Modern syenogranite denotes a granite compositional field; it should not be mistaken for quartz-poor syenite or ancient Egyptian syenites.
Further historical context
A systematic subdivision of the granite field identifying rocks comparatively rich in alkali feldspar.
Older granite labels concealed the relative importance of alkali feldspar and plagioclase.
Quantitative modal mineral proportions, not proximity to ancient Syene.
Modern syenogranite denotes a granite compositional field; it should not be mistaken for quartz-poor syenite or ancient Egyptian syenites.
Related names
Granite · Monzogranite · Syenite · Feldspar · QAPF classification
Sources
- Streckeisen (1976), To each plutonic rock its proper name — IUGS QAPF classification, basis and limits
- BGS, Rock Classification Scheme — Modern descriptive rock-naming principles and definitions
- USGS, Lithologic classification of geologic map units — Modal definitions and named plutonic-rock categories
- IUGS / Le Maitre et al. (2002), Igneous Rocks: A Classification and Glossary of Terms, ch. 3 — Authoritative IUGS rock-name history and bibliographic attributions