Cooling rates for glass containing lunar compositions.

Cooling rates required to form glassy or partly crystalline bodies of 14 lunar compositions were estimated using a previously introduced, simplified model. The calculated rates were found to be in good agreement with cooling rates measured for the same compositions. Measurements are also reported of the liquidus T and glass transition T for each composition. Inferred cooling rates are combined with heat-flow analyses to obtain insight into the thermal histories of samples 15422, 14162, 15025, 74220, 74241, 10084, 15425 and 15427. The critical cooling rates required to form glasses of 24 lunar compositions, including the 14 compositions of the present study, are suggested to increase systematically with increasing ratio of total network modifiers/total network formers in the compositions. This reflects the importance of melt viscosity in affecting glass formation.-P.Br.