(Table 1, page 215) Chemical composition Mn deposits from the Middle Jurassic part of the Austrian Kalkalpen

The X-ray diffraction analyzes of two ferromanganese crust samples found at the base of the Klaus red Jurassic limestone beds of the Unterberg formation indicate pyrolusite as the main mineral. The crusts contain also a range of trace elements in concentrations comparable of present day oceanic deposits. The low Fe/Mn ratio found in sample 06-32a is in agreement with the geochemical data from Pacific Ocean manganese nodules and crusts of hydrothermal genesis. However, the simultaneously high contents in cerium and yttrium (rare earth metals) are more likely to suggest a precipitation of the manganese from the free water column (hydrogenetic origin). In addition, there are no identified hydrothermal sources in the vicinity of the hosting limestone beds. Iron-rich manganese nodules have also been found in the Jurrasic limestones beds of the Ruhpolding formation. In these deposits, hematite is the dominant mineral phase. The high Fe/Mn ratio as well the detritic material they contain (quartz, mica) lead to a possible continental margin origin for these nodules.

对采自翁特贝格组（Unterberg formation）克劳斯红色侏罗纪灰岩地层底部的两件铁锰结壳（ferromanganese crust）样品开展的X射线衍射（X-ray diffraction）分析显示，其主要矿物为软锰矿（pyrolusite）。该类铁锰结壳还含有一系列微量元素，其浓度与现代海洋沉积物中的微量元素水平相当。样品06-32a测得的低铁锰比（Fe/Mn ratio），与太平洋锰结核及热液成因（hydrothermal genesis）铁锰结壳的地球化学数据一致。不过，该类结壳中铈与钇（均为稀土金属（rare earth metals））的含量同时偏高，更倾向于指示锰质从自由水体（free water column）中沉淀形成，即水成成因（hydrogenetic origin）。此外，在该赋存灰岩地层的周边未识别到热液源（hydrothermal sources）。在鲁波尔丁组（Ruhpolding formation）的侏罗纪灰岩地层中，同样发现了富铁锰结核；这类沉积物的主要矿物相为赤铁矿（hematite）。其偏高的铁锰比以及所含的陆源碎屑物质（detritic material，即石英（quartz）与云母（mica）），表明这些锰结核可能形成于大陆边缘成因（continental margin origin）环境。