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The global pattern of trace-element distributions in ocean floor basalts
Hugh St C O'Neill1, Frances E Jenner
1Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory 0200, Australia. hugh.oneill@anu.edu.au
Nature
|November 30, 2012
Summary
Ocean floor basalt chemistry reveals mantle composition and thermal structure. Global trace element patterns indicate magma cycling through chambers, not just fractional crystallization, influences basalt chemistry.
Area of Science:
- Geochemistry
- Petrology
- Plate Tectonics
Background:
- Oceanic crust forms at constructive plate margins via mantle upwelling and partial melting.
- Ocean floor basalts are key products for studying mantle heterogeneity and thermal structure.
- Fractional crystallization has been the assumed process modifying magma before eruption.
Purpose of the Study:
- To investigate the global trace element patterns in ocean floor basalts.
- To determine if fractional crystallization alone explains observed chemical variations.
- To identify the processes responsible for magma composition modification.
Main Methods:
- Analysis of global distributions of trace elements in ocean floor basalts.
- Comparison of observed patterns with predictions from fractional crystallization models.
- Modeling of magma cycling through crustal magma chambers.
Main Results:
- Global trace element distributions in basalts show a systematic pattern.
- This pattern cannot be explained by fractional crystallization alone.
- Magma cycling through a global ensemble of magma chambers is the primary cause.
Conclusions:
- Ocean floor basalt chemistry is significantly influenced by magma cycling through crustal chambers.
- Variations in magma fluxes, chamber depth, and parental magma composition cause deviations from the global pattern.
- Understanding magma chamber processes is crucial for interpreting mantle composition from basalts.
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