Xia Zhiguang, Li Shilei, Hu Zhongya, Bialik Or, Chen Tianyu, Weldeghebriel Mebrahtu F, Fan Qishun, Fan Junxuan, Wang Xiangdong, An Shichao, Zhang Feifei, Xu Haoran, Chen Jiayang, Ji Zhihan, Shen Shuzhong, Lowenstein Tim K, Li Weiqiang
State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, Jiangsu, China.
Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing 210023, Jiangsu, China.
Sci Adv. 2024 Mar;10(9):eadj5474. doi: 10.1126/sciadv.adj5474. Epub 2024 Mar 1.
The surficial cycling of Mg is coupled with the global carbon cycle, a predominant control of Earth's climate. However, how Earth's surficial Mg cycle evolved with time has been elusive. Magnesium isotope signatures of seawater (δMg) track the surficial Mg cycle, which could provide crucial information on the carbon cycle in Earth's history. Here, we present a reconstruction of δMg evolution over the past 2 billion years using marine halite fluid inclusions and sedimentary dolostones. The data show that δMg decreased, with fluctuations, by about 1.4‰ from the Paleoproterozoic to the present time. Mass balance calculations based on this δMg record reveal a long-term decline in net dolostone burial (NDB) over the past 2 billion years, due to the decrease in dolomitization in the oceans and the increase in dolostone weathering on the continents. This underlines a previously underappreciated connection between the weathering-burial cycle of dolostone and the Earth's climate on geologic timescales.
镁的表层循环与全球碳循环相关联，而全球碳循环是地球气候的主要控制因素。然而，地球表层镁循环如何随时间演化一直难以捉摸。海水的镁同位素特征（δMg）追踪着表层镁循环，这可以为地球历史上的碳循环提供关键信息。在此，我们利用海洋石盐流体包裹体和沉积白云岩，重建了过去20亿年的δMg演化。数据显示，从古元古代到现在，δMg随波动下降了约1.4‰。基于这一δMg记录的质量平衡计算表明，在过去20亿年中，由于海洋中白云石化作用的减少和大陆上白云岩风化作用的增加，净白云岩埋藏量（NDB）长期下降。这凸显了在地质时间尺度上，白云岩风化 - 埋藏循环与地球气候之间一种此前未得到充分重视的联系。
