Strontium Isotopic Composition of Basaltic Lavas from the Snake River Plain, Southern Idaho
Leeman WP and Manton WI. 1971. Strontium Isotopic Composition of Basaltic Lavas from the Snake River Plain, Southern Idaho. Earth and Planetary Science Letters. 11:420-434
Projects SR86/SR87 ratios as a model for theorizing the origin and evolution of Snake River basalts including those at CRMO (Craters of the Moon National Monument). Geographic location: Regional, including CRMO. The isotopic composition of strontium has been measured in 54 basalts and associated igneous rocks from the Snake River Plain, southern Idaho. Thirty Pliocene-Holocene olivine tholeiites have 87SR/86SR ratios ranging from 0.7060 to 0.7080 and averaging 0.070 +/- 0.0003; 17 basalts and associated latites from CRMO, King Hill, and the Blackfoot River Canyon have ratios ranging from 0.7080 to 0.7180. The 87SR/86SR ratios in the tholeiites are similar to those in other continental tholeiites, but are greater than those in oceanic basalts and in alkali-olivine basalts from Basin-Range province. The constancy in isotopic composition suggests that the high ratios are characteristic of the parent magma(s) and are not due to crustal contamination. Major and trace element data suggests that the CRMO lavas are differentiates of the olivine tholiites. The high 87SR/86SR ratios of these lavas may be explained by crustal contamination of small volumes of theoliitic magma which differentiated at shallow depth in a Precambrian metamorphic terrain near the margins of the Snake River Plain. Pliocene silicic volcanic rocks which may underlie the Snake River basalts are not likely source of contamination, because five such rocks have present-day 87SR/86SR ratios ranging from 0.7110 to 0.7134.
- Type
- Journal Article
- Authors
- Leeman, W; Manton, W
- Units
- CRMO
- Keywords
- Basalts, Lava Flows, Physical Sciences, Strontium (Sr)