Sample BC

NavDat sample number 3669 · GRANODIORITE

Sample

Sample ID	BC
Rock name	GRANODIORITE
Rock type	PLUTONIC
Composition	INTERMEDIATE
Material	IGNEOUS
Comment	fine grained, light-gray, slightly porphyritic biotite granodiorite; large plagioclase phenocrysts; biotite is much more abundant than hornblende

Location

Latitude	45.4167
Longitude	-112.853
Location	roadcut at curve on Willow Creek Road north of Birch Creek Guard Station and BM6420; Beaverhead County
State / province	Montana
Volcanic field	Pioneer Batholith

Age

Age (Ma)	Error	Min	Max	Geologic age	Dated by
70.4		68	72.6

Analyses

Whole rock

Item	Value	Std. dev.	Unit	Method
SIO2	69.5		WT%	RAPID_ROCK
AL2O3	16.2		WT%	RAPID_ROCK
FE2O3	1.6		WT%	RAPID_ROCK
FEO	1.3		WT%	RAPID_ROCK
MGO	0.62		WT%	RAPID_ROCK
CAO	3.7		WT%	RAPID_ROCK
NA2O	3.8		WT%	RAPID_ROCK
K2O	2.7		WT%	RAPID_ROCK
H2O_PLUS	0.79		WT%	RAPID_ROCK
H2O_MINUS	0.15		WT%	RAPID_ROCK
TIO2	0.26		WT%	RAPID_ROCK
P2O5	0.16		WT%	RAPID_ROCK
MNO	0.08		WT%	RAPID_ROCK
CO2	0.04		WT%	RAPID_ROCK
TOTAL	101		WT%	RAPID_ROCK

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