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Metal-silicate Partitioning at High Pressure and Temperature: Experimental Methods and a Protocol to Suppress Highly Siderophile Element Inclusions
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Copper systematics in arc magmas and implications for crust-mantle differentiation
Cin-Ty A Lee1, Peter Luffi, Emily J Chin
1Department of Earth Science, Rice University, MS-126, 6100 Main Street, Houston, TX 77005, USA. ctlee@rice.edu
Science (New York, N.Y.)
|April 12, 2012
Summary
Continental crust formation is linked to oxidizing conditions. However, copper tracking reveals arc magmas are initially reduced, with sulfide segregation during differentiation explaining crustal copper depletion.
Area of Science:
- Geochemistry
- Petrology
- Tectonic settings
Background:
- Arc magmas are key components of continental crust.
- Continent formation is often linked to oxidizing conditions due to oxidized arc lavas.
- The redox state of arc magmas is crucial for understanding crustal evolution.
Purpose of the Study:
- To investigate the redox state of arc magmas throughout their evolution.
- To use copper (Cu) as a redox indicator due to its affinity for sulfur.
- To determine the role of magmatic differentiation in continental crust formation.
Main Methods:
- Tracking copper (Cu) content in arc magmas from mantle source to crustal emplacement.
- Comparing Cu contents of arc basalts with mid-ocean ridge basalts.
- Analyzing Cu depletion during magmatic differentiation due to sulfide segregation.
Main Results:
- Primitive arc and mid-ocean ridge basalts show identical Cu contents, suggesting similar redox states.
- Most arc magmas experience significant Cu content decrease during differentiation via sulfide segregation.
- Global continental crust exhibits a similar Cu depletion pattern.
Conclusions:
- Primitive arc magmas are not necessarily oxidized.
- Sulfide segregation under reducing conditions during magmatic differentiation is a critical process.
- This process may be essential for the formation of continental crust and its characteristic copper depletion.
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