Oxygen isotope studies of minerals in stony meteorites
1965; Elsevier BV; Volume: 29; Issue: 5 Linguagem: Inglês
10.1016/0016-7037(65)90043-8
ISSN1872-9533
AutoresHugh P. Taylor, Michael B. Duke, Leon T. Silver, Samuel Epstein,
Tópico(s)Groundwater and Isotope Geochemistry
ResumoOxygen isotope analyses demonstrate the following sequence (as in terrestrial igneous rocks) of increasing O18 content for coexisting minerals of stony meteorites: olivine, pyroxene, plagioclase, free silica. Except for the carbonaceous chondrites, the O18O16 ratio of a given mineral is quite uniform in each meteorite class. Differences exist between classes of meteorites, however, as well as between certain meteorites and terrestrial igneous rocks. For example, the O18O16 ratios of meteoritic pyroxenes vary from δ = −0.5 permil to δ = + 8.6 permil (relative to SMOW), whereas pyroxenes in 8 terrestrial igneous rocks have δ-values which range only from + 5.5 to +6.6. The oxygen isotope data suggest a separation of the stony meteorites into three groups, as follows: I. Basaltic achondrites, hypersthene achondrites, and mesosiderites—with pyroxene δ-values of 3.7 to 4.4. II. Hypersthene-olivine chondrites, bronzite-olivine chondrites, enstatite chondrites, enstatite achondrites, and nakhlites—with pyroxene δ-values of 5.3 to 6.3. III. Types I, II and III carbonaceous chondrites, and ureilites—with highly variable olivine and pyroxene δ-values.
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