1California Institute of Technology, Pasadena 91109.
Tóm tắt
The lead isotopic compositions and uranium, thorium, and lead concentrations have been measured on six samples of material from the Sea of Tranquillity. The leads are moderately to very radiogenic; the initial lead concentrations are very low; the uranium and thorium levels are 0.26 to 0.88 and 0.87 to 3.35 parts per million, respectively. The Th/U ratios cluster about a 3.6 value. Apparent ages calculated for four rocks are 4.1 to 4.2 × 10
9
years. Dust and breccia yield apparent ages of 4.60 to 4.63 × 10
9
years. The uranium-lead ages are concordant, or nearly so, in all cases. The lunar surface is an ancient region with an extended record of events in the early history of the solar system. The discrepancy between the rock ages and dust ages poses a fundamental question about rock genesis on the moon.
Từ khóa
Tài liệu tham khảo
Apollo 11 Preliminary Science Report (1969).
10.1016/0016-7037(67)90112-3
Rama Murthy, V., Journal of Geophysical Research 67: 1161 (1962).
10.1016/0016-7037(55)90025-9
10.1126/science.150.3698.886
10.1126/science.153.3740.1094
Wetherill, G. W., Eos, Transactions American Geophysical Union 37: 320 (1956).
