Why are Western U.S. Volcanic and Hypabyssal Rocks So Rich in Ba?
Abstract
Many volcanic and hypabyssal magmatic provinces in the western U.S. are characterized by unusually high Ba. This characteristic extends as far east as Spanish Peaks and Two Buttes in central and eastern Colorado respectively. This characteristic can be quantified by Ba/La ratios but is not consistently, and does not appear to correlate with another important column 2 element, Sr, 87Sr/86Sr ratios nor Th, a marker of marine sediments. Intriguingly the relatively high Ba/La ratios is characteristic of some Rio Grande Rift volcanics, but not of East African Rift volcanics (Kivu, Virunga) although ranges in the latter approach the western U.S. values. The easy solution is to attribute the high Ba to subduction of the Juan de Fuca plate but neither Sr nor Th correlate with the Ba. Consequently, the high Ba cannot easily be attributed to being a subduction signature and may be instead a signature of the asthenosphere beneath the western U. S.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V12A..07R
- Keywords:
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- 1037 Magma genesis and partial melting;
- GEOCHEMISTRYDE: 1038 Mantle processes;
- GEOCHEMISTRYDE: 1040 Radiogenic isotope geochemistry;
- GEOCHEMISTRYDE: 1065 Major and trace element geochemistry;
- GEOCHEMISTRY