腕足类生物壳体在沉积、成岩过程中同位素平衡问题研究

综合分析了现代腕足类生物壳体方解石中的C、O同位素特征，以及有关古生代腕足类生物壳体方解石构造和地球化学研究成果，分析结果证明：只有那些无发光性特点、无胶结和溶蚀构造特点、有较好纤维构造特点、含高Sr、Na和低Mn、Fe（Mg）的第二层腕足类生物壳体方解石的δ18O值不受成岩作用影响；而原始层和壳体中的特殊部位如铰合轴、腕骨、茎孔、交互面、肌痕等在沉积、成岩过程中与海水处于非同位素平衡状态。

A STUDY ON ISOTOPE EQUILIBRIUM OF BRACHIOPOD SHELLS WITH AMBIENT SEAWATER DURING PRECIPITATION AND DIAGENESIS

Carbon and oxygen isotope geochemistry of calcite in modern brachiopod shells during precipitation, in combination with previous studies of textural and chemical characterization of Paleozoic brachiopod shells, suggests that the δ18O values of calcite from secondary shells with nonluminescent fibre, no visible dissolution and cementation features, and containing relatively high Sr, Na and lowMn, Fe(Mg), have not been affected by diagenetic alteration. However, the primary shell calcite andsome special portions such as hinges, brachidia, foramen, interarea and muscle scars are not in isotopeequilibrium with ambient seawater during precipitation and diagenesis.