ABSTRACT We present the results of an optical microscopy, cathodoluminoscopy and isotopic study on nine glendonite concretions (calcite pseudomorphs replacing metastable hexahydrate ikaite) from Lower-Middle Jurassic sediments of Northeast Russia (Anabar Bay and Lena River region). Glendonite concretions are mainly found within Late Pliensbachian, Toarcian, Aalenian, Bajocian and Lower Bathonian clastic sediments, correlating to episodes of global climatic cooling as determined by independent paleoclimate proxy data. Stable carbon and oxygen isotopic values of glendonite concretions suggest that the primary source of carbon was derived from diagenetically altered organic matter, and the source of oxygen was from seawater. The secondary diagenetic cement is characterized by a significantly lighter δ18O and significantly heavier δ13C signature than the isotopic characteristics of the bulk rock glendonite concretion. This secondary diagenetic cement is thought to have precipitated rapidly during burial diagenesis and since it occupies a significant volume of the glendonite concretion, it has the potential to significantly influence the isotopic composition of bulk rock glendonites.

中文翻译：

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西伯利亚侏罗系菱沸石稳定同位素和岩相研究新结果

摘要 我们介绍了对俄罗斯东北部（阿纳巴尔湾和勒拿河地区）下中侏罗统沉积物的九个格陵兰石结核（方解石假晶型取代亚稳六水合石）的光学显微镜、阴极发光和同位素研究的结果。Glendonite 结核主要发现于晚 Pliensbachian、Toarcian、Aalenian、Bajocian 和下巴松阶碎屑沉积物中，与由独立古气候代理数据确定的全球气候变冷事件相关。格陵脱石结核的稳定碳和氧同位素值表明，碳的主要来源来自成岩改变的有机物质，而氧的来源来自海水。次生成岩胶结物的特征是 δ18O 显着轻，δ13C 特征显着高于大块岩石菱沸石结核的同位素特征。这种次生成岩胶结物被认为在埋藏成岩作用过程中迅速沉淀，并且由于它占据了大量的锂辉石结核，它有可能显着影响大块岩辉石的同位素组成。