(Table 1) Chemisity of interstitial water at DSDP Leg 66 holes

During Leg 66, a transect was drilled across the Middle America Trench off Mexico. In this report, interstitial water analyses for Sites 487 (on oceanic crust), 490, 491, and 492 (continental slope apron), and 493 (upper continental slope) are presented. All sites are characterized by high sedimentation rates, and as a result sulfate reduction and methane generation processes are very important. At Sites 490 through 492 decreases in chlorinity are evidence of the presence of gas hydrates. At Site 493 a sharp increase in dissolved calcium and the complete depletion of dissolved magnesium just above basement indicate that weathering of continental crust is still an ongoing process.在第66航次（Leg 66）期间，科研团队横穿墨西哥外海的中美洲海沟（Middle America Trench）实施了断面钻探。本报告呈现了站位487（位于洋壳（oceanic crust）之上）、490、491、492（位于陆坡裙（continental slope apron））以及493（位于上陆坡（upper continental slope））的孔隙水（interstitial water）分析结果。所有站位均以高沉积速率为特征，因此硫酸盐还原作用与甲烷生成过程极为重要。在站位490至492处，氯度（chlorinity）降低是天然气水合物（gas hydrates）赋存的佐证。在站位493处，溶解态钙含量的骤增以及基底上方溶解态镁的完全耗尽，表明陆壳风化作用仍在持续进行。