Origin And Paleoceanographic Environments Response Of Ferromanganese Crusts (Nodules) In The East Philippine Sea

New-type deepwater ferromanganese crusts, ferromanganese nodules developed on the surface of sediment and the underlying sediment under ferromanganese crusts from the East Philippine Sea were selected to be researched. From the analyses on the microstructure, mineral composition, elemental composition, study on these elements occurrence modes, U-series and 10Be isotope dating of the research object, combining the ore-forming background and ore-controlling factors, origin and paleoceanographic environments response of the crusts (nodules) were studied and recovered. This fills up the research blank of synthetic study on the new-type deepwater ferromanganese crusts accreted on the surface of benthic sediments, deepens the consideration on the distribution rule, origin, forming processes and paleoceanographic environments record of ferromanganese crusts (nodules), enriches the benthic metal ore-forming theory, provides a theoretical base and support for the exploration and exploitation of those crusts (nodules) and also offers new research carrier and data for the unclear structral evolution of the studied area since the Late Miocene at the same time.Base on above studies, some conclusions were obtained as follows: (1) ore-forming background of the studied ferromanganese crusts (nodules) are mainly controlled by intensity of Antarctic Bottom Waters (AABW) and variations of material source; (2) it is confirmed that the ferromanganese crusts (nodules) are mainly hydrogenetic and their composition are affected by volcanic and continental material simultaneously; there are no obvious phosphatization reconstruction and element reaction occurred in them, so they have important paleoceanological significance; (3) from researches on element occurrence modes in the new-type ferromanganese crusts and the lying sediments, it is proposed that there is no great biological affection on the crusts formation and their composition mainly came from the adsorptive action of the ferromanganese oxides (hydroxides) in them; (4) two major types of ore-controlling factors are identified through compilation of ore-controlling factors, which are geological and oceanic factors; (5) considering the long-term variation trends of the crusts composition, combing the U-series and 10Be isotope dating results, it is proposed that the ore-forming processes of ferromanganese crusts in the studied areas can be divided into three major stages (5.6~2.8 Ma, 2.8~2.7 Ma and since 2.7 Ma), and then the activities of AABW since the Late Miocene, changes of input flux coming from volcanic and continental (dust) material are confirmed.