Modeling Heat and Mass Transport in the TAG Active Hydrothermal Mound Using a Combined Theoretical/ Observational Approach

摘要P.I.：Tivey提案编号：97-12153机构：世界卫生组织标题：采用理论和观测相结合的方法模拟TAG活动热液丘陵中的热和质量传输，山脊-峰热液系统在将能量和质量通量从地球内部转移到地球表面的过程中发挥着重要作用。1994年秋季，在大洋钻探计划第158航段期间，在大西洋中脊直径200米的TAG活动热液丘陵上钻了17个孔，以调查活跃热液丘陵的流体流动、地球化学通量和地下性质。这个山丘可能是最接近塞浦路斯矿体的大洋中脊，估计来自黑烟的对流热流为225兆瓦，整个山丘区域的对流热流为500-1000兆瓦。将进行理论计算，以检查流出土丘的不同流体之间的关系，并研究TAG处海水夹带的作用，包括夹带的海水数量，以及这种夹带在沉积物和流出土丘的流体中留下的印记。还将进行输送和反应的计算，以便在流体化学和所观察到的钻芯样品的矿物学和结构之间建立联系。重点将放在模拟热液活动最近阶段发生的过程，即：(I)硬石膏(CaSO4)脉的形成，(Ii)与脉状脉有关的蚀变和矿化，(Iii)烟囱和硫化物结壳在土丘表面的沉积，以及(Iv)目前流出土丘的流体的形成。这些研究将能够量化质量通量，并检查大洋中脊系统沿线已知最大的活跃热液丘陵之一的矿物沉积、分区和区域细化过程。

Abstract P.I.: Tivey Proposal Number: 97-12153 Institution: WHOI Title: Modeling heat and mass transport in the TAG active hydrothermal mound using a combined theoretical/observational approach Ridge-crest hydrothermal systems play a fundamental role in transferring energy and mass fluxes from the Earth's interior to its surface. In the fall of 1994, 17 holes were drilled in the 200 meter diameter TAG active hydrothermal mound on the Mid-Atlantic Ridge during Leg 158 of the Ocean Drilling Program to investigate the fluid flow, geochemical fluxes, and the subsurface nature of an active hydrothermal mound. This mound is perhaps the closest mid-ocean ridge analog to Cyprus ore bodies and has an estimated convective heat flux from the black smokers of 225 MW, and from the entire mound area of 500-1000 MW. Theoretical calculations will be carried out to examine the relationships among the different fluids exiting the mound, and to examine the role of seawater entrainment at TAG, including the amount of seawater entrained, and what imprint such entrainment leaves in the deposits, and in fluids exiting the mound. Calculations of transport and reaction will also be done, allowing establishment of links between fluid chemistry and observed mineralogy and texture of drillcore samples. The emphasis will be on modeling processes occurring during the most recent phase of hydrothermal activity, i.e., related to (i) formation of anhydrite (CaSO4) veins, (ii) alteration and mineralization associated with veining, (iii) deposition of chimneys and sulfide crusts at the mound surface, and (iv) formation of fluids currently exiting the mound. These studies will allow quantification of mass fluxes and examination of processes involved in mineral deposition, zoning, and zone refinement in one of the largest known active hydrothermal mounds along the mid-ocean ridge sys tem.