Oxygen Isotopes in Low Temperature Minerals of Unequilibrated Chondrites

9805229WassonWasson我们的主要目标是确定不同的富氧储集层的特征，这些储集层被推测存在于形成单个球粒陨石群的太阳星云区域，或存在于球粒陨石母体中，并对不平衡球粒陨石中日益被认识到的蚀变效应负责。越来越多的证据表明，星云气体的氧同位素组成是在球粒陨石的不同类别中记录的时期内演化的。我们将使用加州大学洛杉矶分校Cameca 1270离子微探测器来研究在太阳星云中的低温或在母小行星内发生的水溶液变化期间形成的关键阶段的氧同位素。Cameca 1270的高效率和高分辨率使我们能够在岩石薄片中暴露的相中测定三种氧同位素，从而保留了有关形成过程的结构和化学信息。在这笔赠款的头两年，我们计划集中研究R中的蚀变产物磁铁矿和普通球粒陨石。当磁铁矿由金属或FeS形成时，所有的O都来自氧化剂，推测在大多数情况下是H2O。我们还将研究另一种蚀变产物--CV球粒陨石中的铁闪石。

9805229WassonOur main goal is to characterize the different O-rich reservoirs inferred to have been present in the solar nebula region where individual chondrite groups formed, or to have been present in the chondrite parent bodies and have been responsible for alteration effects increasingly recognized in the unequilibrated chondrites. There is increasing evidence that the oxygen-isotopic composition of the nebular gas evolved during the period recorded in the various classes on chondritic meteorites. We will use the UCLA Cameca 1270 ion-microprobe to study O-isotopes in key phases that were formed at low temperatures in the solar nebula or during aqueous alteration that occurred within the parent asteroid. The high efficiency and high resolution of the Cameca 1270 permits us to determine the three oxygen isotopes in phases exposed in petrographic thin sections, thus textural and chemical information about the formation process is preserved. During the first two years of this grant we plan to focus our studies on the alteration product magnetite in R and ordinary chondrites. When magnetite forms from metal or FeS, all the O comes from the oxidant, inferred to have been H2O in most cases. We will also study another alteration product, the fayalite present in CV chondrites.