Oxygen and hydrogen isotopes at DSDP Leg 65 Holes@en

In order to provide information on the degree of alteration of the very young basaltic basement drilled on Leg 65 in the mouth of the Gulf of California, we have measured the oxygen isotopic composition of whole rocks and mineral separates. Considerable data already exist for older ocean crust, in particular for the deep holes drilled in the Atlantic Ocean on Deep Sea Drilling Project (DSDP) Legs 37, 45, 46, and 51-53. These data indicate that in all of these holes, which include crust as young as 3.5 m.y. old, a significant amount of alteration has taken place as the result of low-temperature interaction between basalt and seawater (cf. Muehlenbachs, 1977, 1980; Hoernes et al., 1978; Friedrichsen and Hoernes, 1980). It is therefore of interest to determine whether Leg 65 crust, which is only 0.5 to 1.5 m.y. old, has experienced a similar degree of alteration.为明确加利福尼亚湾口第65航次钻获的年轻玄武岩基底的蚀变程度，我们测定了全岩样品与矿物分离组分的氧同位素组成。目前针对较古老洋壳已积累了大量相关数据，尤以深海钻探计划（Deep Sea Drilling Project, DSDP）第37、45、46及51-53航次在大西洋钻取的深孔数据为代表。上述数据显示，所有此类钻孔（涵盖年龄可达3.5百万年的洋壳）均因玄武岩与海水发生低温相互作用而发生了显著蚀变（参见Muehlenbachs, 1977, 1980; Hoernes et al., 1978; Friedrichsen and Hoernes, 1980）。因此，探究仅0.5至1.5百万年的第65航次洋壳是否经历了同等程度的蚀变，具备重要的研究价值。