Abstract

Hydrogenetic ferromanganese crusts in the northwestern (NW) Pacific seamounts are considered as potential future sources of strategic metals. The details of their regional and fine-scale variations in composition and structure are currently unknown. We attempted to characterize the variation patterns in a selected area of the NW Pacific seamounts, based on geological and geochemical analyses, which were performed with a TV-monitored drill machine and remotely operated vehicles, after full bathymetric mapping and an acoustic survey. Subsequent chemical, mineralogical, and structural analyses of the well-preserved crust cores indicated that the hydrogenetic crusts in the seamount area have similar distinct fine-scale variations throughout the growth layers from the substrate to the surface. The crust cores show almost continuous stratigraphic growth since the middle Miocene (approximately 15 Ma ago) or earlier, with significant variations in metal concentration, growth structure, and mineralogy. The fine-scale stratigraphic variations are surprisingly well-correlated across the seamount areas of approximately 1000 km apart; thus, the bulk compositional variation becomes much smaller than a secular variation when compared within the seamount area. Stratigraphic analysis is crucial for the compositional characterization of ferromanganese crusts on various scales.

摘要

西北（NW）太平洋海山的水生锰铁结壳被认为是未来潜在的战略金属来源。目前尚不清楚它们在成分和结构上的区域和细微变化的细节。我们试图根据地质和地球化学分析来描述西北太平洋海山选定区域的变化模式，这些分析是使用电视监控的钻机和遥控车辆在进行全面测深测绘和声学调查后进行的。随后对保存完好的地壳核心进行的化学、矿物学和结构分析表明，海山地区的加氢地壳在从基底到地表的整个生长层中具有相似的明显精细尺度变化。自中新世中期（约 15 Ma 前）或更早以来，地壳岩心显示出几乎连续的地层生长，金属浓度、生长结构和矿物学存在显着变化。在相距约 1000 公里的海山区域，精细尺度的地层变化具有惊人的相关性；因此，在海山区域内进行比较时，整体成分变化远小于长期变化。地层分析对于不同尺度上锰铁结壳的成分表征至关重要。在相距约 1000 公里的海山区域，精细尺度的地层变化具有惊人的相关性；因此，在海山区域内进行比较时，整体成分变化远小于长期变化。地层分析对于不同尺度上锰铁结壳的成分表征至关重要。在相距约 1000 公里的海山区域，精细尺度的地层变化具有惊人的相关性；因此，在海山区域内进行比较时，整体成分变化远小于长期变化。地层分析对于不同尺度上锰铁结壳的成分表征至关重要。