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Forty-four burk samples of the H chondrite Jilin have been analysed for their contents ofspallogenic, trapped and radiogenic noble gases, and thirty-five samples have been determinedfor their radiocosmogenic nuclides. The Jilin meteorite has an extreme complicated history ofcosmic-ray irradiation. In the 1st-stage, the Jilin meteorite might be located between 0.2--2mbelow the surface of the parent body travelling about 8 m. y. in space and under a geometryof 2π subjected to the radiation of cosmic-ray. According to the data of ~(60)Co dating the burialdepth of all samples in the 2nd-stage can be determined and the preatmospheric form andsize of the parent body can be restored (under a geometry of 4π). The result of this recon-struction is that, the 2nd-stage has a nearly spheric form, with a radius of 85±5 cm, weighing9.7±1.7 Ts. The position of the center of the preatmospheric body is: X=55, Y=55 andZ=39. Jilin meteorite No.1 is located at the center of the parent body and is surroundedwith the fragments. The ablation rate is estimated at about 30%. We have proposed a new modelof the two-stage irradiation, and based on the contents of ~(21)Ne-~(60)Co in the samples, a classificationscheme can be worked out for the restoration of relative position of the samples within theparent body.
The Jilin meteorite has an extremely complicated history of cosmic-ray irradiation. In the 1st-stage, the Jilin meteorite might be located between 0.2--2mbelow the surface of the parent body about 8 my in space and under a geometry of 2π subjected to the radiation of cosmic-ray. ) Co dating the burialdepth of all samples in the 2nd-stage can be determined and the preatmospheric form and size of the parent body can be restored (under a geometry of 4π). The result of this recon-struction is that, the 2nd-stage has a nearly spheric form with a radius of 85 ± 5 cm and weighing 9.7 ± 1.7 Ts. The position of the center of the preatmospheric body is: X = 55, Y = 55 and Z = 39. located at the center of the parent body and is surr oundedwith the fragments. The ablation rate is estimated at about 30%. We have proposed a new model of the two-stage irradiation, and based on the contents of ~ (21) Ne- ~ (60) Co in the samples, a classificationscheme can be worked out for the restoration of relative position of the samples within the parent body.