The hydrogeological regime of the TAG sulfide mound on the Mid-Atlantic Ridge - Insights into metal fluxes from reaction-transport modeling

海底块状硫化物(SMS)是古代火山成因块状硫化物(VMS)的现代类似物，可能代表着一种未来的金属资源。它们的形成是对年轻洋底的热液冷却的反应，当时从岩浆热源上升的热液与海水混合，沉积它们的金属负载。中大西洋海脊上的TAG热液丘陵是最大的海底硫化物聚集地之一，是研究控制过程的绝佳地点。它的内部结构已通过大洋钻探(ODP158)进行了探测，并获得了大量的地质和地球物理数据。然而，形成丘陵的详细水文地质状况以及化学沉淀和溶解过程从未用反应-运输模型进行量化，仍然存在重大的知识差距--结果是，可能的全球SMS捐赠以及热液喷发在全球生物地球化学循环中的作用仍然受到很少的限制。在这里，我们将使用3-D反应-传输模型来缩小这些知识差距。我们的方法是使用Gibbs自由能最小化软件GEMS3K，将现有的3-D热液流动模型--热液泡沫与流体岩石相互作用的热力学矿山数据库相结合。这将使我们能够测试TAG热液丘陵形成的情景，并阐明控制热液金属通量流入、流入和流出热液丘陵的主导过程。

Submarine massive sulfides (SMS) are the modern analogues of ancient volcanogenic massive sulfides (VMS) and may represent a future metal resource. They form in response to hydrothermal cooling of the young ocean floor, when hot fluids rising from a magmatic heat source mix with seawater to deposit their metal load. The TAG hydrothermal mound on the Mid-Atlantic Ridge hosts one of the largest submarine sulfide accumulations and is an excellent location for studying the controlling processes. Its internal structure has been probed by ocean drilling (ODP 158) and extensive geological and geophysical data is available. Yet, the detailed hydrogeological regime and the chemical precipitation and dissolution processes that made the mound have never been quantified with reaction-transport models and major knowledge gaps remain – with the consequence that the likely global SMS endowment and also the role of hydrothermal venting in global biogeochemical cycles remain poorly constrained. Here, we will work on narrowing these knowledge gaps using 3-D reaction-transport modeling. Our approach is to couple an existing 3-D hydrothermal flow model, hydrothermalFoam, with the thermodynamic MINES database for fluid rock interactions using the GEMS3K software for Gibbs Free Energy minimization. This will allow us to test scenarios for the formation of the TAG hydrothermal mound and to elucidate the dominant processes that control hydrothermal metal fluxes into, within, and out of hydrothermal mounds.