氧同位素温度计已被用于古温度变化研究多年.生物化石磷酸盐中的氧同位素组成对古气候环境变化响应灵敏,牙形石在古生代到中生代的古海洋地层中广泛存在,并具有较为重要的地层学意义,是研究古温度变化的最佳样品之一.SHRIMP具备高分辨、高灵敏、高精度和微量及原位微区分析的特点,可以进行20 μm范围内的原位(in-situ)同位素分析.本文介绍了作者利用SHRIMP IIe-MC建立的牙形石微区原位氧同位素分析方法,这是国内关于该方法的首次报导.本文对磷灰石标准样Durango进行了测定,连续七昼夜获得的253次测定结果,平均值为δ18Oapatite=9.78‰±0.29‰,与该标准参考值δ18Oapatite=9.81‰±0.25‰(Williams,未刊资料)一致.作者并以二叠系—三叠系界线上下海水温度变化研究为示范,对采自西藏文布当桑二叠系—三叠系剖面上的49个层位中的237件牙形石样品进行了914个氧同位素分析,为研究二叠系—三叠系界线上发生的生物灭绝事件前后的海水温度变化提供了可靠详实的数据.%O isotopes thermometer has been used to study changing in the paleo-climate for dacades. O isotopes in phosphate from fossils are sensitive to the variation of the paleo-climate. Conodont is one of the best samples for the O isotopes study due to its abundant existence within the marine stratum from Paleozoic to Mesozoic and significance in stratigraphy. Sensitive High Resolution Ion Microprobe (SHRIMP) is capable of doing in-situ O isotopes analysis with the diameter of the ion spots less than 20 μm by consuming only very few sample and is characterized by high resolution, sensitivity and precision. In this work, we introduce the analytical methods and measuring instruments established in Beijing SHRIMP Ile-MC center for the in-situ O isotopes analysis on conodont for the first time. The continuous 7 days with 253 spots analysis on the apatite standard Durango yields the mean value of δ18 Oapatite = 9. 78‰±0. 29‰, which is consistent with the reference value of 9. 81‰±0. 25‰(Williams, unpublished). As an example, we also measure the O isotopes of 237 conodont samples from 49 strata from the Permian-Triassic profile in Wenbusangdang, Tibet, with 914 analysis spots, and provide reliable and accurate data on the variation of the paleo-temperature during the mass extinction at the Permian-Triassic boundary.
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