| Summary: | In this study, the volumetric compression of jadeite (NaAlSi<sub>2</sub>O<sub>6</sub>) melt at high pressures was determined by three-dimensional volume imaging using the synchrotron-based X-ray microtomography technique in a rotation-anvil device. Combined with the sample mass, measured using a high-precision analytical balance prior to the high-pressure experiment, the density of jadeite melt was obtained at high pressures and high temperatures up to 4.8 GPa and 1955 K. The density data were fitted to a third-order Birch-Murnaghan equation of state, resulting in a best-fit isothermal bulk modulus <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>K</mi> <mrow> <mi>T</mi> <mn>0</mn> </mrow> </msub> </mrow> </semantics> </math> </inline-formula> of <inline-formula> <math display="inline"> <semantics> <mrow> <msubsup> <mrow> <mn>10.8</mn> </mrow> <mrow> <mo>−</mo> <mn>5.3</mn> </mrow> <mrow> <mo>+</mo> <mn>1.9</mn> </mrow> </msubsup> </mrow> </semantics> </math> </inline-formula> GPa and its pressure derivative <inline-formula> <math display="inline"> <semantics> <mrow> <msubsup> <mi>K</mi> <mrow> <mi>T</mi> <mn>0</mn> </mrow> <mo>′</mo> </msubsup> </mrow> </semantics> </math> </inline-formula> of <inline-formula> <math display="inline"> <semantics> <mrow> <msubsup> <mrow> <mn>3.4</mn> </mrow> <mrow> <mo>−</mo> <mn>0.4</mn> </mrow> <mrow> <mo>+</mo> <mn>6.6</mn> </mrow> </msubsup> </mrow> </semantics> </math> </inline-formula>. Comparison with data for silicate melts of various compositions from the literature shows that alkali-rich, polymerized melts are generally more compressible than alkali-poor, depolymerized ones. The high compressibility of jadeite melt at high pressures implies that polymerized sodium aluminosilicate melts, if generated by low-degree partial melting of mantle peridotite at ~250−400 km depth in the deep upper mantle, are likely denser than surrounding mantle materials, and thus gravitationally stable.
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