摘要
海底玄武岩风化及碳酸盐化是海洋的重要碳汇,调节了海洋和大气系统的碳循环.以往一般认为这一过程仅发生在年轻洋壳中,对俯冲带洋底玄武岩的风化和碳酸盐化几乎没有关注.本研究基于西太平洋Mussau海沟东侧崖壁的玄武岩样品,利用激光剥蚀原位铀系不平衡法对洋底玄武岩中的碳酸盐脉进行定年,发现其形成于(102±16)ka和(132±21)ka.通过矿物学、微形貌与稳定同位素手段,确认了碳酸盐脉的矿物相为方解石,并以侵染状分布于玄武岩中,无生物碳酸盐的形态,并沉淀于冷水环境中.这些证据综合表明碳酸盐脉很可能是玄武岩在海底风化,释放出碳酸氢根,局部方解石过饱和沉淀而成.该结果表明古老玄武岩在俯冲带的化学风化和碳酸盐化依然活跃,未来需进一步系统研究俯冲带的玄武岩风化通量.
Carbonate precipitation and weathering in basalts during seafloor low-temperature alteration constitute an important,yet poorly understood,sink of carbon in the ocean[1,2].It was estimated that~3.4×10^(12)mol carbon was stored each year by basalt carbonation and up to 30%of such storage was likely associated with submarine weathering[3].As such,oceanic basalt alteration and carbonation might provide an additional feedback[4–6]via their dependences on bottom water-carbon chemistry and temperature,in stabilizing the geological carbon cycle within the ocean and atmosphere system.Understanding the timing of weathering and secondary carbonate precipitation in the oceanic basalt is thus of high priority toward reliably evaluating the feedback between carbon flux into the seafloor and the global climate.
作者
王茂宇
李贺
杨昕瑜
孙卫东
陈天宇
Maoyu Wang;He Li;Xinyu Yang;Weidong Sun(State Key Laboratory for Mineral Deposits Research,Frontiers Science Center for Critical Earth Material Cycling,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China;Center of Deep Sea Research,Ocean Mega-Science Center,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;Deep-Sea Multidisciplinary Research Center,Laoshan Laboratory,Qingdao 266237,China;University of Chinese Academy of Sciences,Beijing 100049,China)
基金
supported by the National Natural Science Foundation of China to Weidong Sun(91958001)and Tianyu Chen(91858105)。
