Primary carbonatite melt from deeply subducted oceanic crust
M J Walter1, G P Bulanova, L S Armstrong
1Department of Earth Sciences, University of Bristol, Queen's Road, Bristol BS8 1RJ, UK. m.j.walter@bris.ac.uk
Nature
|August 1, 2008
Summary
Diamond inclusions reveal that carbonatite melts, originating from subducted oceanic crust, form deep within the Earth's mantle. These ancient melts influence mantle geochemistry and geodynamics over billions of years.
Area of Science:
- Geochemistry
- Mineralogy
- Petrology
- Geodynamics
Background:
- Partial melting in the Earth's mantle generates geochemical diversity in volcanic rocks.
- Mantle geochemical reservoirs and geodynamic processes are linked to primary melt compositions.
- Mineral inclusions in diamonds offer insights into deep mantle processes.
Purpose of the Study:
- To identify the composition of primary and evolved carbonatite melts in the mantle.
- To link mantle geochemical reservoirs to geodynamic processes using diamond inclusions.
- To understand the role of subducted crust in mantle evolution.
Main Methods:
- Experimental petrology
- Geochemical analysis of mineral inclusions in diamonds
- Trace element abundance calculations
Main Results:
- Silicate mineral inclusions in Juina diamonds crystallized from carbonatite melts.
- Melt inclusions indicate melting of carbonated oceanic crust at transition zone depths.
- Garnet inclusions record crystallization from evolved melts resembling primitive carbonatites.
Conclusions:
- Carbonatite melts derived from subducted crust are significant agents of chemical mass transfer in the mantle.
- These melts leave a lasting chemical imprint on the upper mantle and transition zone.
- Diamond inclusions provide crucial evidence for deep mantle processes and crust-mantle interactions.
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