Abstract
From petrographic study, a large Allende type B inclusion, Golfball has experienced at least two melting events. In the present study, we report preliminary results of oxygen and Al-Mg isotopic measurements of spinel and melilite in Golfball to determine ages of the multiple melting events and the oxygen isotopic composition of each melt. Delta O-18= -50 to -40permil for spinel, and the oxygen isotopic composition of melilite is distinct in each petrographic occurrence: Delta O-18= -20 to -10permil for gehlenitic core melilite and Delta O-18= ~0permil for melilite in the rim. Two isochrons are defined by the Al-Mg data. The gehlenitic core melilite and rim melilite yield initial 26Al/27Al ratios of 4.9+-0.8 and 1.9+-1.2x10-5, respectively. The age difference between the two isochrons is calculated to be about 1 My. From the chronological and the previous petrographic studies, we discuss the crystallization history of Golfball.
