亳县陨石及其球粒的氧同位素特征

The Boxian chondrite and its separated chondrules was systematically researched in mineralogy, petrology, texture, Oxygen isotopes and the distribution of grain size. The range of mineral compositions is consistent with a reclassification of Boxian meteorite from LL4 to LL3.9. The chondrule size distribution is approximately log-normal, being consistent with the size sorting mechanisms, but the variation in diameter of different chondrule types and a hiatus in the size distribution at 0.6 mm indicate that there may have been complex controls. Existence of cristobalite-bearing and Al-rich chondrules indicates that they experience chemical fractionation, probably being resulted from both igneous and volatility controls. Three separate isotopic exchange events have been identified in Boxian meteorite, including low-temperature hydrous gas-solid exchange event between 16O-rich solid and 160-poor gas reservoirs that lay along a slope 1.0 line on three-isotope plots; partial equilibration with the gas by feldspar and cristobalite that led to formation of a slope 0.77 mixing line; and a dominant gas-solid exchange between the precursor O and the mineral phases during an earlier phase of mass-indepent fractionation.

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