ON THE POSSIBILITY FOR THE OCCURRENCE OF HYDROSILICATES IN THE LUNAR MANTLE

The hypothesis that the Moon was formed. from a dust fraction of the p rotoplanetary cloud depleted in Fe but enriched in Ca and Al and conta ining hydrosilicates leads to explanation of the Lunar seismic profile . Anomalously low values of seismic velocities depths of 270-500 km ca n result from stable existence of ultrabasic rocks containing hydrous phases. Both the nature of the seismic boundary between the middle and lower mantle at depth of 500 km and absence of hydrosilicates in lowe r mantle can be explained by the hydrous phases dehydratation at the P -T-parameters exceeding the upper stability limit. The seismic boundar y between the upper and middle mantle at depth of 270 km can be explai ned by a thermal alteration of initial Moon-formig rocks to the depths of 250-300 km leading in particular to melting of crust material and complete lost of H2O and FeS in the upper mantle.