(Table 1) Magnetic viscosity coefficient, VRM and NRM of DSDP Hole 6-57@en

THE magnetic properties of the basalts which form layer 2 of the oceanic lithosphere are important because of their relevance to the hypothesis (Vine and Matthews, 1963, doi:10.1038/199947a0) of seafloor spreading. Most studies of these magnetic properties have been carried out on basalts obtained from dredge hauls taken predominantly from ocean ridge systems and fracture zones. These constitute special areas of the oceanic crust where the sediment cover is negligible. It is of interest to compare the magnetic properties of the dredged basalts with samples recovered from holes drilled through the overlying sediments into the basaltic layer at places distant from ridge axes. Samples obtained from the abandoned Mohole project and, more recently, from the Deep Sea Drilling Project (DSDP) possessed magnetic properties similar to those of dredged basalts (Cox and Doell, 1962, doi:10.1029/JZ067i010p03997; Lowrie et al., 1973, doi:10.1016/0012-821X(73)90198-2). Here I describe highly unstable magnetic characteristics found in basalts from DSDP hole 57.构成海洋岩石圈（oceanic lithosphere）第二层的玄武岩的磁学性质具有重要研究意义，因其与维因和马修斯（Vine and Matthews, 1963, doi:10.1038/199947a0）提出的海底扩张假说密切相关。当前针对这类玄武岩磁学性质的研究，大多基于主要采自洋脊系统（ocean ridge systems）与断裂带（fracture zones）的拖网采样（dredge hauls）所得的玄武岩样品。这些采样区域属于洋壳的特殊区段，其上覆沉积盖层极薄，几乎可忽略不计。将拖网采样获得的玄武岩磁学性质，与远离洋脊轴（ridge axes）处、通过钻穿上覆沉积物到达玄武岩层的钻孔样品进行对比，具备重要研究价值。来自废弃的莫霍孔计划（Mohole project）以及近年深海钻探计划（Deep Sea Drilling Project, DSDP）所获取的样品，其磁学性质与拖网采样的玄武岩高度相似（Cox and Doell, 1962, doi:10.1029/JZ067i010p03997; Lowrie et al., 1973, doi:10.1016/0012-821X(73)90198-2）。本文描述了深海钻探计划第57号钻孔（DSDP hole 57）所获玄武岩中发现的高度不稳定的磁学特征。