Density and compressibility of the molten lunar picritic glasses: Implications for the roles of Ti and Fe in the structures of silicate melts

摘要: Abstract The density and compressibility of four synthetic molten lunar picritic glasses was investigated from 0 to 10 GPa 1748 2473 K. were collected the surface during Apollo missions, they are hypothesized have rapidly quenched as glass beads pyroclastic fire fountain eruptions. specific melt compositions in present study 15 green Type C (A15C, TiO2 = 0.26 wt%), 14 yellow (A14Y, TiO2 = 4.58 wt%), 17 orange 74220-type (A17O TiO2 = 9.12 wt%), black (A14B, TiO2 = 16.40 wt%). These reported represent primary unfractionated melts, making them a prime candidate for experimental studies into basalt partial melting mantle. Sink–float experiments conducted on using piston-cylinder apparatus (P   2.5 GPa) order bracket melts. New sink–float data A15C, A14Y, A17O, which combined with previously published A14B. Although Ti-rich liquids highly compressible at lower pressures, become nearly incompressible much higher pressures when compared low-Ti glasses. Consequently, melts most TiO2 (A14B) least dense reversal what is seen pressures. This change attributed changes coordination Ti Fe silicate structure. As Ti4+ abundances increase, predominantly [IV]Ti4+ [IV]Fe2+ [VI]Ti4+ [VI]Fe2+ All used calculate Birch–Murnaghan equation-of-state (BM-EOS) each composition. BM-EOS model composition then estimates residual mantle source mineralogy depth origin assess respect its point origin. information determine whether or not would rise sink region. We determined that all compositions, exception A17O melt, should been able crust-mantle boundary result buoyancy forces alone, although different mechanisms likely required magma ascent through crust. For other modes extract this mantle, volatiles plausible solution grounds alone.