Annotated record of the detailed examination of Mn deposits from the Mariana Arc area, Pacific Ocean

A detailed geophysical and geological survey of the Mariana Trough, an actively extensional back-arc basin, was conducted in 1976 and 1977 to provide data for selection of drilling sites for DSDP Leg 60. These surveys revealed large-scale bathymetric trends, sediment distribution, crustal seismic veolocity structure, and earthquake activity that suggest the basin is opening around an axial spreading center tectonically similar to the slowly spreading Mid-Atlantic Ridge. There are, however, significant differences in the character of the trough, such as poorly defined magnetic anomalies, extreme bathymetric relief, and the frequent occurrence of low-magnitude earthquakes but absence of larger seismic events. Seafloor spreading in the Mariana Trough may be characteristic of the initial opening stages of any oceanic rift system, whether or not it is in a back-arc setting.1976年至1977年间，研究团队针对作为活动伸展弧后盆地的马里亚纳海槽（Mariana Trough）开展了详尽的地球物理与地质调查，旨在为深海钻探计划（Deep Sea Drilling Project, DSDP）第60航次的钻井选址提供数据支撑。本次调查揭示了大规模水深地形趋势、沉积物分布特征、地壳地震波速度结构与地震活动规律，结果表明该海槽围绕轴部扩张中心发生张开，其构造特征与慢速扩张的大西洋中脊（Mid-Atlantic Ridge）极为相似。不过该海槽仍存在多项显著差异：例如磁异常特征模糊、极端水深地形起伏剧烈，且频繁出现低震级地震，但缺乏大型地震事件。马里亚纳海槽的海底扩张过程，可作为任何大洋裂谷系统（无论其是否处于弧后环境）初始张开阶段的典型代表。