Uranium and thorium microdistributions in stony meteorites |
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| Authors: | Ghislaine Crozaz |
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| Institution: | Department of Earth and Planetary Sciences, and McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130, U.S.A. |
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| Abstract: | Uranium distributions have been determined in seventeen meteorites using fission track techniques. In seven cases, Th was also determined by a new method using fast neutrons. The actinides are generally concentrated in phosphates, usually whitlockite and/or chlorapatite. Wherever whitlockite and chlorapatite coexist, chlorapatite is richer in uranium. U concentrations in a given phosphate phase are highly variable from meteorite to meteorite and sometimes also show large variations in the same meteorite. A clinopyroxene phase enriched in U (0.2–0.3 ppm) is usually found in Ca-rich achondrites. The ratios of phosphates differ considerably from whole rock values indicating that these elements were fractionated during the meteorite formation. |
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