Chemical and structural complexities in interstratified clay minerals arising from mineral transformations and evolving formation conditions should be recorded in their stable isotope signatures. This paper examines the controls on the stable hydrogen and oxygen isotope compositions of Fe-rich, glauconite-nontronite, talc-nontronite and talc-saponite from submarine hydrothermal sites, with a focus on the Red Sea Atlantis II Deep. Values of O became less positive in the order nontronite > glauconite-nontronite > talc-nontronite > talc-saponite, yielding oxygen isotope temperatures ranging from ∼40 °C for nontronite to ∼135–300 °C for talc-saponite. These clay minerals have low H, ranging from −145 to −127‰ for talc-nontronite, −135‰ for nontronite, −129 to −85‰ for glauconite-nontronite, and −95 to −59‰ for talc-saponite. The clay mineral-water hydrogen isotope fractionation is strongly affected by Fe content, with increasing structural Fe causing progressive weakening of O-H bonds. The large ionic radius and high charge of Fe cause it to be more poorly shielded by surrounding oxygen from hydroxyl hydrogen relative to other octahedral or tetrahedral cations. The resulting lengthening of O-H bonds favours H over H. Our results confirm that Fe-rich phases, such as nontronite-glauconite, are produced at the lowest temperatures and Mg-rich phases, such as talc-saponite, are formed at the highest temperatures in seafloor hydrothermal environments. Evolving fluid chemistry and fluid pathways during clay mineral formation are also important. Glauconite layer formation from precursor nontronite likely occurred during diagenesis; redox changes causing Fe-reduction and an increase in layer charge facilitated interlayer K-fixation. Talc-saponite compositions vary with temperature and fluid chemistry, forming at variable sediment depths depending on access to the hottest hydrothermal fluids.

中文翻译：

---

海底热液区富含 Fe3+ 的层间粘土矿物的稳定氢和氧同位素地球化学

由矿物转化和不断演变的形成条件引起的层间粘土矿物的化学和结构复杂性应记录在其稳定同位素特征中。本文研究了对海底热液地点富铁、海绿石-绿脱石、滑石-绿脱石和滑石-皂石的稳定氢和氧同位素组成的控制，重点关注红海亚特兰蒂斯二号深海。 O 值按照囊脱石>海绿石-囊脱石>滑石-囊脱石>滑石-皂石的顺序变得不太正，产生的氧同位素温度范围从囊脱石的∼40°C到滑石粉-皂石的∼135–300°C。这些粘土矿物的 H 值较低，滑石-绿脱石的 H 值范围为 -145 至 -127 ‰，绿脱石的 -135 ‰，海绿石 - 绿脱石的 -129 至 -85 ‰，滑石粉 - 皂石的 -95 至 -59 ‰。粘土矿泉水氢同位素分馏受 Fe 含量的强烈影响，随着结构 Fe 的增加，导致 OH 键逐渐减弱。相对于其他八面体或四面体阳离子，Fe 的大离子半径和高电荷导致其受到周围氧与羟基氢的屏蔽更差。由此产生的 OH 键延长有利于 H 而非 H。我们的结果证实，富铁相（例如绿脱石-海绿石）在最低温度下生成，富镁相（例如滑石皂石）在最高温度下形成在海底热液环境中。粘土矿物形成过程中流体化学和流体路径的演变也很重要。海绿石层的形成可能发生在成岩作用过程中。氧化还原变化导致铁还原和层电荷增加促进层间钾固定。滑石皂石的成分随温度和流体化学性质的变化而变化，根据最热的热液流体的情况，在不同的沉积深度处形成。