BGS Rock Classification Scheme
Foid-diorite - A type of foid-dioritic-rock. In the Rock Classification Scheme, it is a coarse-grained crystalline igneous rock whose mineral mode plots in field 14 of the quartz - alkali feldspar - plagioclase - feldspathoid (QAPF) diagram. Foid-diorite and foid-gabbro are distinguished according to the average composition of their plagioclase: if An (the anorthite content of plagioclase) is less than 50% the rock is foid-diorite. British Geological Survey Research Report RR/99/06, section 5.1 and figs. 9, 11, 12.
| Code | FDIO |
|---|---|
| Description | Foid-diorite - A type of foid-dioritic-rock. In the Rock Classification Scheme, it is a coarse-grained crystalline igneous rock whose mineral mode plots in field 14 of the quartz - alkali feldspar - plagioclase - feldspathoid (QAPF) diagram. Foid-diorite and foid-gabbro are distinguished according to the average composition of their plagioclase: if An (the anorthite content of plagioclase) is less than 50% the rock is foid-diorite. British Geological Survey Research Report RR/99/06, section 5.1 and figs. 9, 11, 12. |
| Qualifiers | No qualifiers currently exist. |
| Definition | Coarse-grained, av. between 2-16mm normal crystalline intrusive rock; feldspathoids 10-60% of QAPF, feldspar >90% plagioclase (<50% An) +/- mica/pyroxene/amphibole/olivine |
| Linked data | http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/FDIO |
CAVEAT
"Thumbnail" definitions attached to some of the table entries are an interim attempt to provide simple short descriptions of the "unqualified" rock types presented within the BGS Rock Classification Scheme. Every effort has been made to ensure accuracy and consistency but minor contradictions or omissions might be present. The BGS welcomes any feedback pointing out such minor imperfections and/or providing constructive comment and suggestions for improvement of the definitions. In the first instance such feedback should be directed to Dr Tim McCormick.