Ar-39/Ar-40 systematics of Allende inclusionsA laser microprobe was used to measure the Ar isotopic contents of individual mineral grains in four neutron-irradiated Allende samples: two coarse-grained Ca-Al-rich inclusions; one fine-grained Ca-Al-rich inclusion; and one sample with matrix and miscellaneous chondrules. The following K-Ar ages (G.y.) were obtained after degassing low Ar retentive sites by preheating the samples for one hour at 675 C: matrix, 3.5 + or - 0.2; three miscellaneous chondrules, 4.4 + or - 0.1, 4.0 + or - 0.1, and 4.4 + or - 0.1; and the fine-grained inclusion, 4.5 + or - 0.2. The minerals in the coarse-grained Ca-Al-rich inclusions have ubiquitous chlorine, less than 10 ppm K and apparent ages ranging upwards from 4.6 G.y. to well over 10 G.y. Possible explanations for these apparent ages are atmospheric contamination, the decay of K-40 prior to the formation of the solar system, and the trapping of radiogenic Ar-40 lost by the matrix.
Document ID
19820038769
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Herzog, G. F. (New York, State University Stony Brook, NY; Rutgers University, New Brunswick, NJ, United States)
Bence, A. E. (State Univ. of New York Stony Brook, NY, United States)
Bender, J. (State Univ. of New York Stony Brook, NY, United States)
Eichhorn, G. (State Univ. of New York Stony Brook, NY, United States)
Maluski, H. (State Univ. of New York Stony Brook, NY, United States)
Schaeffer, O. A. (New York, State University Stony Brook, NY, United States)