Strontium isotope geochemistry of a low potassium olivine tholeiite and two basalt-pyroxene andesite magma series from the Medicine Lake Highland, California
✍ Scribed by Stanley A. Mertzman
- Book ID
- 104745657
- Publisher
- Springer
- Year
- 1979
- Tongue
- English
- Weight
- 897 KB
- Volume
- 70
- Category
- Article
- ISSN
- 0010-7999
No coin nor oath required. For personal study only.
✦ Synopsis
Three contemporaneous yet mineralogically and chemically distinct lava series which range in composition from olivine basalt through basaltic andesire through two-pyroxene andesite, have been analyzed for their strontium isotopic composition, The Mammoth-Modoc lavas produce a mantle isochron which suggests derivation from a source approximately 243 m.y. old. The Medicine Lake shield-forming extrusives produce a minimum mantle isochron; the age of this source is likely greater than 760 m.y. old. Encompassing the entire time span of eruption for the two basalt-andesite series are a number of low potassium high alumina olivine tholeiite lavas which, when analyzed as a coherent group, produce a zero age. Lavas related to these three magma series have been extruded during the last 105 years and cover a limited geographic area. The isotope data suggest a model with substantial heterogeneity in the subcontinental lithosphere and asthenosphere, at least beneath the Medicine Lake Highland portion of the southern Cascade petrographic province.