Salt minerals that are used to reconstruct paleoenvironments should be either primary or samples that provide primary-level information. Using hydrated sulfate minerals that are commonly found in saline lacustrine sediments (i.e., bloedite and polyhalite), the paleoenvironment of the Qaidam Basin, in the northeastern Tibetan Plateau was reconstructed. In this study, we determined the primary and secondary mineral formations based on their S, Mg, H, and O isotopic compositions. While polyhalite is a secondary mineral, bloedite precipitated out from the brine at 0.39 Ma, and ultimately became a secondary mineral at 0.36 Ma. The bloedite and polyhalite Mg isotopes did not record primary signals, but they still provide valuable insights into the paleoenvironments in which they formed. The climate in our study area is very dry; based on the temperature of the brine, this region experienced high temperatures at 0.39 Ma, 0.36 Ma, and 0.12 Ma. We identified one major chemical inconsistency: the bloedite 18O-hydrated water and 18O-SO4 values had basically achieved equilibrium, while the polyhalite and gypsum exhibited no oxygen exchange between their SO4 and hydrated water components. The possible reason for the inconsistency was the differences in mineral crystal structures. We hope that future studies will reconcile this conflicting information.

中文翻译：

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水合硫酸盐矿物（bloedite 和 polyhalite）：形成和古环境影响

用于重建古环境的盐矿物应该是原始的或提供原始信息的样本。利用盐湖相沉积物中常见的水合硫酸盐矿物（即白斑和杂卤石），重建了青藏高原东北部柴达木盆地的古环境。在这项研究中，我们根据 S、Mg、H 和 O 同位素组成确定了原生和次生矿物的形成。杂卤石是次生矿物，0.39 Ma时从卤水中析出的杂卤石，最终在0.36 Ma时成为次生矿物。血钙石和杂卤石 Mg 同位素没有记录原始信号，但它们仍然为了解它们形成的古环境提供了宝贵的见解。我们研究区的气候非常干燥；根据卤水的温度，该地区经历了 0.39 Ma、0.36 Ma 和 0.12 Ma 的高温。我们发现了一个主要的化学不一致性：杂卤石 18O-水合水和 18O-SO4 值基本达到平衡，而杂卤石和石膏在其 SO4 和水合水组分之间没有氧交换。不一致的可能原因是矿物晶体结构的差异。我们希望未来的研究能够调和这些相互矛盾的信息。不一致的可能原因是矿物晶体结构的差异。我们希望未来的研究能够调和这些相互矛盾的信息。不一致的可能原因是矿物晶体结构的差异。我们希望未来的研究能够调和这些相互矛盾的信息。