The conodont Color Alteration Index (CAI) has been widely used to determine the maximum temperature in carbonate rocks, despite recognition that conodont colour can be affected by other factors, such as diagenesis. Measurements of trace element characteristics in conodonts of varying CAI (1.5–6.0) from the Canadian Cordillera show that those specimens with the most anomalous CAI with respect to independent estimates of maximum temperature also have the highest concentrations of iron (> 3000 ppm). The adsorption of transition metals such as iron onto bioapatite crystals and permineralization by their oxides in conodont elements are herein proposed as mechanisms for the modification of CAI during diagenesis. Furthermore, the trace element characteristics of conodonts, primarily those of the lanthanide, or rare earth element (REE) series, have frequently been used as a proxy for palaeoceanographic conditions, including anoxic events. However, the impact of early diagenetic processes post-burial obscures this marine signal, and instead, the trace element characteristics of conodonts likely reflect the characteristics of pore waters or diagenetic fluids. Several geochemical ‘tools’ have been proposed to test for such overprinting of palaeoceanographic information, including Y/Ho vs. ΣREE, MREE/MREE*, U concentration, and La/Yb. However, REE and Raman structural characteristics in a suite of conodonts from the Canadian Cordillera indicate that these ‘tools’ cannot be systematically applied. The majority of conodont specimens analysed in this study appear to have been affected by post-burial diagenetic alteration using one or more of the ‘tools’, but seem to be unaltered when investigated using other ‘tools’. Additionally, several specimens which appear to be diagenetically unaltered when using the metrics of the geochemical ‘toolbox’ exhibit diagenetically induced structural changes. The geochemical ‘tools’ are thus unable to discriminate between diagenetic alteration induced before and after burial, and they should therefore be accompanied by structural analyses if REE characteristic of conodonts are used to infer palaeoceanographic conditions.

尽管认识到牙形体颜色会受到其他因素（例如成岩作用）的影响，但牙形体颜色变化指数（CAI）已被广泛用于确定碳酸盐岩中的最高温度。对来自加拿大山脉变化的CAI（1.5–6.0）的牙形体中痕量元素特征的测量表明，就最高温度的独立估计而言，那些具有最大CAI异常的样品也具有最高的铁浓度（> 3000 ppm）。本文提出过渡金属如铁在生物磷灰石晶体上的吸附以及其在牙形石元素中的氧化物的矿化作用，作为成岩过程中CAI改性的机理。此外，牙形合金的痕量元素特征，主要是镧系元素或稀土元素（REE）系列，经常被用作古海洋学条件（包括缺氧事件）的代表。但是，埋藏后早期成岩作用的影响掩盖了这种海洋信号，相反，牙形石的痕量元素特征可能反映了孔隙水或成岩流体的特征。已经提出了几种地球化学“工具”来测试这种古海洋学信息的叠印，包括Y / Ho与ΣREE，MREE / MREE *，U浓度和La / Yb。但是，来自加拿大山脉的一系列牙形石中的REE和拉曼结构特征表明，这些“工具”无法得到系统地应用。这项研究中分析的大多数牙形石标本似乎受使用一种或多种“工具”的埋葬后成岩作用的影响，但是使用其他“工具”进行调查时似乎并没有改变。此外，当使用地球化学“工具箱”的度量标准时，看起来似乎在数理学上没有改变的几个标本表现出了由数理学引起的结构变化。因此，地球化学“工具”无法区分在埋葬之前和之后引起的成岩作用变化，因此，如果用牙形石的REE特征来推断古海洋学条件，则应进行结构分析。