The study of serpentinites and ophicarbonates from ophiolitic terrains provides a three-dimensional perspective on the hydration and carbonation processes affecting modern oceanic lithosphere. The Chenaillet ophiolite (western Alps) is interpreted as a fragment of an oceanic core complex that resembles a modern slow spreading center, and it was weakly affected by Alpine metamorphism. Ophicarbonates from the Chenaillet ophiolite were targeted in this study for in situ analysis by Secondary Ion Mass Spectrometry (SIMS) of oxygen and carbon isotopes in serpentine, calcite, dolomite and magnetite. The high spatial resolution of SIMS allowed us to target different serpentine, carbonate and magnetite generations intergrown at scales ≤ 50 μm, and reveal systematic zoning in δ¹⁸O with a range of 5.8‰ in serpentine (from 3.0 to 8.8‰, V-SMOW), 21.2‰ in carbonate (9.4 to 30.6‰), and 5.6‰ in magnetite (–5.0 to –10.6‰). Coupled analysis of oxygen isotopes in seven different touching-pairs of co-crystallized serpentine + carbonate and serpentine + magnetite provides independent constraints on both the temperatures and δ¹⁸O_(water) values during serpentinization and carbonation responsible for the formation of the Chenaillet ophicarbonates. The new stable isotope data and thermometric estimates can be directly linked to textural and petrographic observations. These new results identify at least four different stages of hydrothermal alteration in the Chenaillet ophicarbonates: (1) peridotite hydration during seafloor exhumation at temperatures down to 200–130 °C and water δ¹⁸O values varying from 5 to 2‰, as documented by serpentine + magnetite in mesh textures; (2) carbonation during exhumation near the seafloor at temperatures as low as 10 °C assuming water δ¹⁸O values of –1‰, as documented by the highest oxygen isotope ratios in texturally older calcite; (3) serpentinization and carbonation at temperatures up to 240 °C and water δ¹⁸O values of 2-3‰, as documented by serpentine + magnetite in veins crosscutting mesh textures (T = 192 ± 66 °C, δ¹⁸O_(water) = 2 ± 1‰, 2 standard deviation), serpentine + magnetite (T = 182 ± 32 °C, δ¹⁸O_(water) = 2 ± 1‰) and serpentine + dolomite (T = 243 ± 79 °C, δ¹⁸O_(water) = 3 ± 2‰) in recrystallized hourglass domains within serpentinite clasts, serpentine + dolomite (T = 229 ± 50 °C, δ¹⁸O_(water) = 3 ± 1‰) and serpentine + calcite (T = 208 ± 40 °C, δ¹⁸O_(water) = 2 ± 1‰) within the fine-grained calcite matrix surrounding serpentinite clasts; (4) late stage carbonation at temperatures down to 70–40 °C assuming water δ¹⁸O values of 3 to –1‰, as documented by the highest oxygen isotope ratios in a large calcite vein crosscutting both serpentinite clasts and fine-grained carbonate matrix. We suggest that the textural and isotopic observations are consistent with a protracted serpentinization and carbonation of the lithospheric mantle that started during progressive exhumation to the seafloor and continued due to interaction with hot and isotopically shifted seawater, which circulated at depth in the oceanic crust and was then discharged near the seafloor, similar to modern mid-ocean ridge venting systems.

蛇绿岩地形中蛇纹岩和蛇纹石的研究为影响现代海洋岩石圈的水化和碳化过程提供了三维视角。Chenaillet蛇绿岩（西阿尔卑斯山）被解释为类似于现代缓慢扩张中心的大洋核心复合体的碎片，它受到高山变质作用的影响较弱。本研究的目标是使用来自 Chenaillet 蛇绿岩的 Ophicarbonates，通过二次离子质谱 (SIMS) 对蛇纹石、方解石、白云石和磁铁矿中的氧和碳同位素进行原位分析。SIMS 的高空间分辨率使我们能够以≤ 50 μm 的尺度共生不同的蛇纹石、碳酸盐和磁铁矿世代为目标，并揭示 δ ^{18 的}系统分带O 在蛇纹石中的范围为 5.8‰（从 3.0 到 8.8‰，V-SMOW），在碳酸盐中为 21.2‰（9.4 到 30.6‰），在磁铁矿中为 5.6‰（–5.0 到 –10.6‰）。对共结晶蛇纹石 + 碳酸盐和蛇纹石 + 磁铁矿的七种不同接触对中氧同位素的耦合分析提供了对温度和 δ ¹⁸ O _（水）的独立约束蛇纹石化和碳酸化过程中的值，负责形成 Chenaillet 奥氏碳酸盐。新的稳定同位素数据和测温估计可以直接与结构和岩相观察相关联。这些新结果确定了 Chenaillet 磷碳酸盐中至少四个不同的热液蚀变阶段：(1) 海底开采过程中橄榄岩的水合作用，温度低至 200–130 °C，水的 δ ¹⁸ O 值从 5 到 2‰ 不等，如文献所述网状纹理中的蛇纹石 + 磁铁矿；(2) 在温度低至 10 °C 的情况下，假设水为 δ ^18，在海底附近挖掘过程中的碳化作用O 值为 –1‰，如结构较老的方解石中最高氧同位素比率所记录的；(3) 在高达 240 °C 的温度和水 δ ¹⁸ O 值为 2-3‰ 的情况下蛇纹石化和碳化，正如在脉中横切网格纹理中的蛇纹石 + 磁铁矿所记录的那样 ( T  = 192 ± 66 °C, δ ¹⁸ O _(水)  = 2 ± 1‰, 2 标准差), 蛇纹石 + 磁铁矿 ( T  = 182 ± 32 °C, δ ¹⁸ O _(water)  = 2 ± 1‰) 和蛇纹石 + 白云石 ( T  = 243 ± 79 °C, δ ¹⁸ O _(水)  = 3 ± 2‰) 在蛇纹岩碎屑、蛇纹石 + 白云石 ( T = 229±50℃，δ ¹⁸ Ô _（水）  = 3±1‰）和蛇纹石+方解石（Ť  = 208±40℃，δ ¹⁸ Ô _（水） 的细粒度方解石内= 2±1‰）围绕蛇纹石碎屑的基质；(4) 后期碳酸化，温度低至 70–40 °C，假设水 δ ¹⁸O 值为 3 至 –1‰，如横切蛇纹岩碎屑和细粒碳酸盐基质的大型方解石脉中最高氧同位素比所记录的那样。我们认为，结构和同位素观察结果与岩石圈地幔的长期蛇纹石化和碳化一致，该地幔在逐渐挖掘到海底期间开始，并由于与热的和同位素转移的海水相互作用而继续，这些海水在大洋地壳深处循环并被然后在海底附近排放，类似于现代大洋中脊通风系统。