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Bishop tuff revisited: new rare Earth element data consistent with crystal fractionation
Science (New York, N.Y.)
|June 22, 1984
Summary
New analyses of the Bishop Tuff reveal that its rare earth element trends are consistent with crystal fractionation, not liquid-state differentiation as previously suggested. This finding supports the role of phenocryst precipitation in rhyolite evolution.
Area of Science:
- Geochemistry
- Volcanology
- Petrology
Background:
- The Bishop Tuff is a key example of high-silica rhyolite.
- Previous research suggested its evolution via liquid-state differentiation.
Purpose of the Study:
- To re-evaluate the evolutionary model of the Bishop Tuff.
- To investigate the rare earth element trends in the Bishop Tuff.
Main Methods:
- New chemical analyses of Bishop Tuff samples.
- Comparison of groundmass glass and whole rock compositions.
- Analysis of allanite-bearing pumice.
Main Results:
- The observed rare earth element trends mimic relationships between groundmass glasses and whole rocks.
- Elemental concentration differences are attributed to phenocryst precipitation.
- Data align with expectations for crystal fractionation.
Conclusions:
- The Bishop Tuff's elemental trends support crystal fractionation as the primary evolutionary mechanism.
- Revises the understanding of high-silica rhyolite evolution.
- Challenges the liquid-state differentiation model for this type example.
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