Investigation of manganese nodules from the Malvinas (Falkland) Plateau

Manganese nodules occurring within marine sediments of presumably Upper Miocene-Lower Pliocene age from cores obtained by the Argentine oceanographic vessel ARA Islas Orcadas in 1977 on the Malvinas (Falkland) Plateau and neighbouring Scotia Sea were studied with the aim of comparing them with other fossil nodules found on the mainland of Argentina that were also ascribed to the marine environment. After optical mineralogical, chemical, X-ray and trace element analysis, the studied "nodules" proved to be actually wacke clasts cemented by manganese oxides with a high Fe/Mn ratio corresponding to a continental environment. The studied "nodules" thus differ from the Argentine mainland nodules and are supposed to have been transported from continental environments and then deposited in the marine realms. The wacke clasts became then nuclei for the deposition of the marine manganese oxides of the coatings. The proportion of trace elements, which is high, suggests the growth of the nodules in the marine environment.

1977年，阿根廷海洋考察船ARA Islas Orcadas号在马尔维纳斯（福克兰）高原及邻近斯科舍海采集了岩芯，其中赋存于推测为晚中新世-早上新世海相沉积物中的锰结核（Manganese nodules）成为本次研究对象，研究目的是将其与阿根廷大陆境内同样被归为海相环境的化石锰结核进行对比。经光学矿物学、化学、X射线及微量元素分析后，本次研究的“结核”实际为以高铁锰比的锰氧化物胶结的杂砂岩碎屑，其形成环境为大陆环境。因此，本次研究的“结核”与阿根廷大陆的锰结核存在显著差异，推测其源自大陆环境，经搬运后沉积于海相域中。这些杂砂岩碎屑随后成为了外壳中海相锰氧化物沉积的核心。其较高的微量元素占比，表明该类“结核”生长于海相环境中。