The stability of hydrous silicates in Earth's lower mantle: Experimental constraints from the systems MgO–SiO2–H2O and MgO–Al2O3–SiO2–H2O

DOI: 10.1016/j.chemgeo.2015.05.001

Authors: M. J. Walter (University of Bristol) , A. R. Thomson (University of Bristol) , W. Wang (University of Bristol) , O. T. Lord (University of Bristol) , J. Ross (University of Bristol) , S. C. Mcmahon (University of Bristol) , M. A. Baron (University of Bristol) , E. Melekhova (University of Bristol) , A. K. Kleppe (Diamond Light Source) , S. C. Kohn (University of Bristol)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemical Geology , VOL 418 , PAGES 16 – 29

State: Published (Approved)
Published: December 2015
Diamond Proposal Number(s): 8669 , 9788

Abstract: We performed laser-heated diamond anvil cell experiments on bulk compositions in the systems MgO–SiO2–H2O (MSH) and MgO–Al2O3–SiO2–H2O (MASH) that constrain the stability of hydrous phases in Earth's lower mantle. Phase identification by synchrotron powder diffraction reveals a consistent set of stability relations for the high-pressure, dense hydrous silicate phases D and H. In the MSH system phase D is stable to ~ 50 GPa, independent of temperature from ~ 1300 to 1700 K. Phase H becomes stable between 35 and 40 GPa, and the phase H out reaction occurs at ~ 55 GPa at 1600 K with a negative dT/dP slope of ~− 75 K/GPa. Between ~ 30 and 50 GPa dehydration melting occurs at ~ 1800 K with a flat dT/dP slope. A cusp along the solidus at ~ 50 GPa corresponds with the intersection of the subsolidus phase H out reaction, and the dT/dP melting slope steepens to ~ 15 K/GPa up to ~ 85 GPa.

Journal Keywords: Phase D; Phase H; Hydrogen; Lower mantle; Hydrous silicate melt

Subject Areas: Chemistry, Earth Science


Instruments: I15-Extreme Conditions

Added On: 16/11/2015 16:22

Documents:
1-s2.0-S0009254115002351-main.pdf

Discipline Tags:

Earth Sciences & Environment Mineralogy Geology Geochemistry

Technical Tags:

Diffraction