Triple oxygen isotope compositions of authigenic minerals are an emerging tool for the reconstruction of fluid temperatures and the fluid isotopic composition. In this study, we analyzed euhedral authigenic quartz crystals from a halite deposit of the Upper Permian Zechstein evaporitic basin for their triple oxygen isotope composition using laser fluorination isotope ratio mass spectrometry. In the triple oxygen isotope space, additional information, such as the triple oxygen isotope composition of the ambient water, provides insights into equilibrium conditions during quartz formation that cannot be identified from δO alone. The triple oxygen isotope composition of authigenic quartz shows, that single oxygen isotope (δO) thermometry is not applicable for samples from evaporitic environments, where the fluids' δO deviates from dynamic oxygen isotope equilibrium. By combining the Craig and Gordon evaporation model with HO – SiO triple oxygen isotope equilibrium fractionation, we reconstruct the formation temperature of authigenic quartz and the triple oxygen isotope composition of the marine-derived saline brine pore fluid in equilibrium with the quartz. We obtain temperatures of 90 to 130 °C that is interpreted as crystallization temperatures of microcrystalline quartz in pore fluid of halite during burial diagenesis. The triple oxygen isotope composition of authigenic quartz from evaporitic environments is suited as a geochemical tracer for fluid oxygen isotope compositions and ancient fluid or diagenetic temperatures.

中文翻译：

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自生石英揭示了盐水的三氧同位素组成和成岩温度


自生矿物的三重氧同位素组成是重建流体温度和流体同位素组成的新兴工具。在这项研究中，我们使用激光氟化同位素比质谱法分析了来自上二叠统 Zechstein 蒸发盆地岩盐矿床的自生石英晶体的三氧同位素组成。在三氧同位素空间中，其他信息（例如周围水的三氧同位素组成）可以深入了解石英形成过程中的平衡条件，而这些信息无法仅通过 δ18O 来识别。自生石英的三重氧同位素组成表明，单氧同位素 (δ18O) 测温法不适用于蒸发环境中的样品，因为蒸发环境中流体的 δ18O 偏离动态氧同位素平衡。通过将Craig和Gordon蒸发模型与H2O-SiO三氧同位素平衡分馏相结合，我们重建了自生石英的形成温度以及与石英平衡的海相盐水孔隙流体的三氧同位素组成。我们获得了 90 至 130 °C 的温度，这被解释为埋藏成岩过程中石盐孔隙流体中微晶石英的结晶温度。来自蒸发环境的自生石英的三重氧同位素组成适合作为流体氧同位素组成和古代流体或成岩温度的地球化学示踪剂。