← Search
Sample DR
NavDat sample number 3665 · DIORITE
Sample
| Sample ID | DR |
|---|
| Rock name | DIORITE |
|---|
| Rock type | PLUTONIC |
|---|
| Composition | INTERMEDIATE |
|---|
| Material | IGNEOUS |
|---|
| Comment | medium to fine grained; dark bluish-gray, biotite hornblende quartz diorite; igneous foliation is very weakly developed; large hornblende laths; biotite grains have two distinct sizes; plagioclase is equant; sphene is rare |
|---|
Location
| Latitude | 45.5933 |
|---|
| Longitude | -112.953 |
|---|
| Location | prominent ledge at 9540 ft elevation on NW side of Keokirk Mountain; Beaverhead County |
|---|
| State / province | Montana |
|---|
| Volcanic field | Pioneer Batholith |
|---|
Age
| Age (Ma) | Error | Min | Max | Geologic age | Dated by |
|---|
| 79.8 |
|
77.6 |
82 |
|
|
References
- Zen, E-an; Marvin, R F; Mehnert, H H (1975) Preliminary petrographic, chemical, and age data on some intrusive andassociated contact metamorphic rocks, Pioneer Mountains, southwesternMontana. Geological Society of America Bulletin, vol.86, no.3, pp.367-370,1975 doi:10.1130/0016-7606(1975)86<367:PPCAAD>2.0.CO;2
