Genetic interpretation of lead-isotopic data from the Columbia River basalt group, Oregon, Washington, and Idaho.
Geological Society of America Bulletin
By: S. E. Church
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Abstract
Lead-isotopic data for the high-alumina olivine plateau basalts and most of the Colombia River basalt group plot within the Cascade Range mixing array. The data for several of the formations form small, tight clusters and the Nd and Sr isotopic data show discrete variation between these basalt groups. The observed isotopic and trace-element data from most of the Columbia River basalt group can be accounted for by a model which calls for partial melting of the convecting oceanic-type mantle and contamination by fluids derived from continental sediments which were subducted along the trench. These sediments were transported in the low-velocity zone at least 400 km behind the active arc into a back-arc environment represented by the Columbia Plateau province. With time, the zone of melting moved up, resulting in the formation of the Saddle Mt basalt by partial melting of a 2600 m.y.-old sub-continental lithosphere characterized by high Th/U, Th/Pb, Rb/Sr and Nd/Sm ratios and LREE enrichment. Partial melting of old sub-continental lithosphere beneath the continental crust may be an important process in the formation of continental tholeiite flood basalt sequences world-wide. -L.di H.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Genetic interpretation of lead-isotopic data from the Columbia River basalt group, Oregon, Washington, and Idaho. |
| Series title | Geological Society of America Bulletin |
| Volume | 96 |
| Issue | 5 |
| Year Published | 1985 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Geological Society of America Bulletin |
| First page | 676 |
| Last page | 690 |
| Google Analytic Metrics | Metrics page |