Major and minor elements in hydrothermal and pelagic sediments at DSDP Leg 70 Holes

Interaction between young basaltic crust and seawater near the oceanic speading centers is one of the important processes affecting the chemical composition of the oceanic layer. The formation of metalliferous hydrothermal sediments results from this interaction.
The importance of the interaction between seawater and basalt in determining the chemical composition of pore waters from sediments is well known. The influence of mineral solutions derived from this interaction on ocean water composition and the significant flux of some elements (e.g., Mn) are reported by Lyle (1976), Bogdanov et al. (1979), and others. Metal-rich sediments found in active zones of the ocean basins illustrate the influence of seawater-basalt interaction and its effect on the sedimentary cover in such areas. The role of hydrothermal activity and seawater circulation in basalts with regard to global geochemistry cycles has recently been demonstrated by Edmond, Measures, McDuff, McDuff et al. (1979), and Edmond, Measures, Mangum (1979).
In the area of the Galapagos Spreading Center the interaction of sediments and solutions derived from interaction of seawater and basalt has resulted in the formation of hydrothermal mounds. The mounds are composed of manganese crusts and green clay interbedded and mixed with pelagic nannofossil ooze. These mounds are observed only in areas characterized by high heat flow (Honnorez, et al., 1981) and high hydrothermal activity.

大洋扩张脊（oceanic spreading centers）附近的年轻玄武质地壳（young basaltic crust）与海水相互作用，是影响大洋层化学成分的关键过程之一。含金属热液沉积物（metalliferous hydrothermal sediments）的形成正是源于这一相互作用。
海水与玄武岩的相互作用对沉积物孔隙水化学成分的调控作用早已获得学界广泛认同。Lyle（1976）、Bogdanov等（1979）及其他学者的研究均表明，该相互作用产生的矿物溶液会改变海水化学组成，且部分元素（如锰Mn）会发生显著的通量变化。在洋盆活动区域发现的富金属沉积物，也佐证了海水-玄武岩相互作用对该区域沉积盖层的影响。近期，Edmond、Measures、McDuff、McDuff等人（1979）以及Edmond、Measures、Mangum（1979）的研究证实了玄武岩内热液活动与海水循环在全球地球化学循环中的核心作用。
在加拉帕戈斯扩张脊（Galapagos Spreading Center）区域，沉积物与海水-玄武岩相互作用产生的溶液发生反应，形成了热液丘（hydrothermal mounds）。这类热液丘由锰结壳（manganese crusts）与绿黏土（green clay）互层混杂，并混合有远洋颗石藻软泥（pelagic nannofossil ooze）。根据Honnorez等（1981）的观测结果，此类热液丘仅分布于高热流（high heat flow）与强热液活动区域。