Rubidium-strontium age of hypersthene (L) chondrites

Five normal gray hypersthene chondrite falls were analyzed for Rb, Sr, and Sr isotopic composition. One (Bath Furnace) has such low Rb/Sr and Sr87/Sr86 ratios that it, in conjunction with others, permits determination of an isochron for L-chondrites alone, without resort to the data of any other types of meteorite and attendant assumptions of cogenesis. An age of 4.48 ± 0.14 × 109 years (λ = 1.39 × 10-11 year-1) and initial Sr87/Sr86 ratio of 0.7008 + .001 were measured. Blank corrections were less than 0.2 and 0.1% for Rb and Sr, respectively, in processing about 300 mg of sample