Water-rock interaction in hydrothermal systems at 'liquid-vapor' equilibrium conditions: An experimental approach

考虑到许多缓慢扩张的海脊位于水深大于3000m的位置，位于大西洋中脊(MAR)5°S处的海底热液作用具有极高的热通量、金属通量和独特的稀土元素化学(REE)，对海洋元素收支具有普遍意义。在这些高压(P)/高温(T)水热系统中，传输-反应过程受到的约束很差。我们建议(1)在类似于MAR5°S的p-T条件下进行实验，以研究海水-岩石相互作用和由此产生的元素分配；(2)时间分辨岩石蚀变和次生矿物的产生；(3)随后流体和岩石化学的时间综合变化的模拟。初始材料将是天然大西洋深水，与来自IODP孔U1309D的未改变的辉长岩碎片发生反应(辉长岩：1020米BSL，橄榄辉长岩：~1050米BSL，沸石：~1125米BSL；在第一期资金中仅对辉长岩进行了实验)。此外，系统地研究IODP站U1309D玄武岩和辉长岩样品的次生矿物组合的元素组成和REE模式，并结合文献中的其他数据，将有助于更好地解释我们的实验结果，了解洋壳的自然蚀变过程。总之，我们实验得出的过渡金属和稀土元素的水-岩分配行为以及模拟将增加我们对海水-岩石相互作用过程的了解，并将提高我们对在极端温度和大水深的热液系统中上升过程中的迁移反应和元素通量的理解。

Given the fact that many sections of slow-spreading ridges are at water depths greater than 3000 m, the submarine hydrothermalism at 5°S on the Mid Atlantic Ridge (MAR) with extreme fluxes of heat, metals and unique rare earth element chemistry (REE) is of general significance for oceanic element budgets. Transport-reaction processes in these high-pressure (p) / high-temperature (T) hydrothermal systems are poorly constrained. We propose (1) experiments under p-T-conditions similar to those at MAR 5°S for the study of seawater-rock interaction and resulting element partitioning as well as (2) of time-resolved rock alteration and generation of secondary minerals and (3) subsequent modelling of time-integrated changes of fluid and rock chemistry. The starting materials will be natural Atlantic Deep Water reacting with unaltered gabbroic fragments from IODP Hole U1309D (gabbro: 1020 m bsl, Olivine-gabbro: ~1050 m bsl, troctolite: ~1125 m bsl; only experiments with gabbro were performed in the first period of funding). In addition, a systematic study of elemental composition and REE pattern of secondary mineral assemblages of recovered basaltic and gabbroic samples from IODP Site U1309D will - together with other data from the literature - help to better interpret our experimental findings and understand the natural alteration processes of oceanic crust. In summary, our experimentally derived water-rock partitioning behaviour of transition metals and REE as well as the modelling will add to our knowledge of seawater-rock interaction processes and will improve our understanding of transport reactions and element fluxes during ascent in hydrothermal systems that run at extreme temperatures and great water depths.