To help understand bioapatite microstructures and related chemical variations, their impact on O-isotope compositions measured and give insights on sample preparation, this study analysed conodonts and shark teeth prepared in different orientations through microanalytical and bulk sampling techniques: scanning electron microscopy (SEM); electron probe microanalysis (EPMA); continuous-flow and high-temperature reduction – isotope ratio mass spectrometry; and secondary ion mass spectrometry (SIMS). The SEM and EPMA measurements in conodonts allowed to distinguish the tissues commonly analysed by SIMS, which included albid and hyaline crowns but given their often small-scale intergrowth, mixtures of these are difficult to avoid. In situ SIMS O-isotope analyses provided different δ¹⁸O values: lower values with higher variance (16 ± 1‰ n = 13, 15.7 ± 1.9‰ n = 11) for mixed albid-hyaline tissues, and higher, homogeneous values (17.1 ± 0.2‰, n = 13) for mainly hyaline tissues. Recent shark teeth δ¹⁸O_SIMS value for dentine of the same tooth was 10‰ lower than the mean δ¹⁸O_SIMS value for enameloid whereas the δ¹⁸O_PO4 values measured for enameloid and dentine using the HTR method were identical. The variation of δ¹⁸O seems sensitive to analytical artefacts related to sample textures, caused during the sample preparation over more porous biomineral surfaces.

中文翻译：

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关于牙形刺和鲨鱼牙齿生物磷灰石地球化学和氧同位素组成微尺度变化的新见解

为了帮助了解生物磷灰石微观结构和相关化学变化、它们对测量的 O 同位素成分的影响并深入了解样品制备，本研究通过微量分析和批量采样技术分析了不同方向制备的牙形刺和鲨鱼牙齿：扫描电子显微镜 (SEM)；电子探针微量分析（EPMA）；连续流高温还原-同位素比质谱法；和二次离子质谱（SIMS）。牙形刺中的 SEM 和 EPMA 测量可以区分通常由 SIMS 分析的组织，其中包括白化牙冠和透明牙冠，但鉴于它们通常是小规模共生，因此很难避免这些组织的混合。原位SIMS O 同位素分析提供了不同的 δ ¹⁸ O 值：对于混合白斑-透明组织，较低的值具有较高的方差 (16 ± 1 ‰ n = 13、15.7 ± 1.9 ‰ n = 11)，而较高的均质值 (17.1 ± 0.2‰，n = 13) 主要用于透明组织。最近的鲨鱼牙齿同一牙齿牙本质的δ ¹⁸ O _SIMS值比釉质的平均 δ ¹⁸ O _{SIMS值低 10‰，而使用 HTR 方法测量的釉质和牙本质的 δ} ¹⁸ O _PO4值相同。 δ ¹⁸ O的变化似乎对与样品纹理相关的分析假象敏感，这些假象是在多孔生物矿物表面的样品制备过程中引起的。