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Lateral isotopic discontinuity in the lower crust: an example from antarctica
Science (New York, N.Y.)
|September 4, 1987
Summary
Investigating Antarctic lower crustal granulites reveals a significant compositional and age discontinuity. This geological boundary, identified through strontium and oxygen isotopes, may indicate an ancient suture beneath the Transantarctic Mountains.
Area of Science:
- Geochemistry
- Petrology
- Tectonics
Background:
- The lower continental crust's composition and evolution remain poorly understood.
- Understanding crustal heterogeneity is key to deciphering Earth's crust-mantle dynamics.
Purpose of the Study:
- To investigate the nature and compositional heterogeneity of the lower continental crust in the McMurdo Sound region, Antarctica.
- To analyze strontium and oxygen isotopes, major, and trace elements of lower crustal granulite inclusions.
Main Methods:
- Analysis of over 20 granulite inclusions from volcanic rocks in Antarctica.
- Strontium and oxygen isotope geochemistry.
- Major and trace element analysis.
Main Results:
- A distinct discontinuity in lower crustal composition and age was identified.
- This discontinuity aligns with the boundary between the Transantarctic Mountains and the Ross Embayment.
- Isotopic differences suggest this boundary may represent an ancient crustal suture.
Conclusions:
- The lower crust in the McMurdo Sound region exhibits significant heterogeneity.
- The observed boundary likely signifies a long-lived tectonic feature, possibly an ancient suture zone.
- Current Cenozoic rifting may be reactivating this older crustal boundary.
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