CHEMICAL-COMPOSITION, TEMPERATURE, AND RA DIUS OF THE LUNAR CORE FROMGEOPHYSICAL EVIDENCE

Thermodynamic modeling of phase relations and physical properties of m ulticomponent mineral systems was used to develop a method for solving the inverse problem of reconstructing the bulk composition and temper ature conditions in the mantle and the core radius of the Moon from th e totality of geophysical evidence (seismic velocities, moment of iner tia, and mass of the Moon). The seismically permissible ranges of the bulk chemical compositions in various zones of the Lunar mantle were d etermined within the system CaO-FeO-MgO- Al2O3SiO2. Isochemical models fail to explain the topology of the seismic structure. Consequently, the lunar mantle is chemically stratified. The bulk composition of the Moon's silicate portion (crust + mantle) falls within the following c oncentration ranges (in wt %): 26 < MgO < 31, 11 < FeO < 12, 5 < Al2O3 < 7, 3.6 < Ca < 5.0, and 48.5 < SiO2 < 51. A probable law of temperat ure variation with depth in the lunar mantle was obtained. The tempera tures range from 350 to 460 degrees C at the crust-mantle boundary (58 km) and from 1000 to 1200 degrees C at a depth of 1000 km. Models of the Moon's internal structure without density inversions were construc ted, and values of the core radius were calculated. The most likely co re sizes fall within the interval 500-590 km for a FeS core, and 330-3 90 km for a gamma-Fe-core.