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Strontianite in coral skeletal aragonite
R B Greegor1, N E Pingitore, F W Lytle
1Boeing Company, Seattle, WA 98124, USA.
Science (New York, N.Y.)
|March 7, 1997
Summary
Coral skeletons incorporate strontium in complex ways, with significant amounts forming strontianite (SrCO3) alongside strontium-substituted aragonite. This finding complicates using coral strontium for paleothermometry.
Area of Science:
- Geochemistry
- Paleoclimatology
- Marine Biology
Background:
- Scleractinian corals precipitate calcium carbonate skeletons.
- Strontium incorporation into coral skeletons is a key proxy for paleotemperature reconstruction.
- The exact mineralogical sites of strontium within coral skeletons are not fully understood.
Purpose of the Study:
- To investigate the mineralogical partitioning of strontium within scleractinian coral skeletons.
- To elucidate the structural environment of strontium in coral skeletons.
- To assess the implications for paleotemperature proxies.
Main Methods:
- X-ray spectroscopy was employed to analyze coral skeletons.
- Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy was used to determine local atomic environments.
- Fourier transform analysis of EXAFS data was performed.
Main Results:
- Strontium substitutes for calcium in the aragonite structure of coral skeletons.
- A significant portion (up to 40%) of strontium was found in a separate strontianite (SrCO3) phase.
- EXAFS analysis revealed distinct metal-oxygen neighbor distances for strontium in aragonite and strontianite.
Conclusions:
- The partitioning of strontium between seawater and coral skeletons is more complex than previously assumed.
- The presence of both strontium-substituted aragonite and strontianite influences the reliability of coral-based paleothermometry.
- Further research is needed to refine paleotemperature reconstructions based on coral strontium.