Influence of seawater-rock interaction on global cycle

本项目取得的重要成果如下：(1)阐明了中新世弧后盆地(日本绿凝灰岩地区)碳酸盐岩的地球化学特征。这些数据表明，碳酸盐的形成影响了当时的海洋和大气环境。(2)来自弧后盆地和岛弧的热液中二氧化碳浓度和来自这种构造背景的二氧化碳通量很大。(3)全球碳循环模拟包括来自相关板块边界的热液和火山气体通量，可以解释早、中中新世的变暖，但不能解释从中中新世到现在的降温。(4)这一结果表明，这种冷却不是喜马拉雅风化和热液活动的抬升造成的。

Important results obtained by this project can be summarized as follows.(1) Geochemical characteristic features of carbonates at Miocene back arc basins (Green tuff region in Japan) were elucidated. These data indicate that the formation of carbonates affects the oceanic and atmospheric environments at that time.(2) The concentrations of carbon dioxide in hydrothermal solutions from back arc basins and island arcs and fluxes from such tectonic setting are large.(3) Global carbon cycle simulations including hydrothermal and volcasic gas fluxes from concergant plate boundary can explain warming at early and Middle Miocene but cannot cooling from Middle Miocene toward present.(4) This results suggest that the cooling has not been caused by up lift of Himalaya weathering and hydrothermal activity.