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Structural change in molten basalt at deep mantle conditions
Chrystèle Sanloup1, James W E Drewitt, Zuzana Konôpková
11] Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Scottish Universities Physics Alliance, Edinburgh EH9 3JZ, UK [2] Université Pierre et Marie Curie, UMR-CNRS 7193, Institut des Sciences de la Terre Paris, F-75005, Paris, France.
Nature
|November 9, 2013
Summary
High pressure transforms silicate melt structure, impacting Earth's deep processes. This study reveals how silicon coordination changes in molten basalt under extreme pressure, influencing melt compressibility and element partitioning.
Area of Science:
- Geochemistry
- Mineral Physics
- High-Pressure Science
Background:
- Silicate liquids are crucial for Earth's evolution, from early formation to volcanic activity.
- Understanding silicate melt behavior under high pressure is vital for quantitative Earth models.
- Experimental challenges have historically limited data on deep Earth silicate melts.
Purpose of the Study:
- To investigate the structural changes and compression mechanisms of molten basalt at high pressures.
- To determine the equation of state for silicate melts relevant to the Earth's mantle.
- To explore the implications of melt compressibility on siderophile element partitioning.
Main Methods:
- In situ X-ray diffraction was used to probe the structure of molten basalt.
- Experiments were conducted at pressures up to 60 gigapascals (GPa).
- Analysis focused on silicon coordination and melt density evolution.
Main Results:
- Silicon coordination in molten basalt increases from four to six by 35 GPa.
- Melt compressibility decreases significantly after the silicon coordination change.
- A high-order equation of state is necessary to accurately model density at mantle pressures.
Conclusions:
- The observed structural transition in silicate melts affects their compressibility.
- Melt compressibility at high pressure influences the partitioning of elements like nickel between molten iron and silicates.
- These findings provide critical data for modeling deep Earth processes and core-mantle interactions.
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