Oxygen Isotopes in Low Temperature Minerals of Unequilibrated Chondrites

9805229沃森我们的主要目标是表征不同的富O水库推断已存在于太阳星云地区的个别球粒陨石群形成，或已存在于球粒陨石母体，并已负责越来越多地认识到在不平衡的球粒陨石的蚀变效应。 越来越多的证据表明，星云气体的氧同位素组成是在不同类别的南极陨石记录的时期演变的。 我们将使用UCLA Cameca 1270离子微探针研究在太阳星云低温下形成的关键阶段的O同位素，或在母小行星内发生的水蚀变期间形成的O同位素。 Cameca 1270的高效率和高分辨率使我们能够确定岩石薄片中暴露的三种氧同位素，从而保留了有关形成过程的结构和化学信息。在这项资助的头两年，我们计划把研究重点放在R和普通磁铁矿的蚀变产物磁铁矿上。 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，即CV陨石中的铁橄榄石。

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.