Global cooling forced increase in marine strontium isotopic ratios: Importance of mica weathering and a kinetic approach
Global cooling forced increase in marine strontium isotopic ratios: Importance of mica weathering and a kinetic approach
复制标题
全球变冷迫使海洋锶同位素比增加：云母风化的重要性和动力学方法
DOI：
10.1016/j.epsl.2006.11.045
复制
发表时间：
2007-02-28
影响因子：
5.3
通讯作者：
Sheng, Xuefen
中科院分区：
文献类型：
--
作者：
Li, Gaojun;Chen, Jun;Sheng, Xuefen
了解海洋 Sr-87/Sr-86 比率如何以及为何变化有助于了解地质过去许多过程对全球生物地球化学循环的影响。在这里，我们通过动力学方法研究了全球变冷对海洋 Sr-87/Sr-86 曲线演化的可能影响。云母风化的重要性因其放射性锶含量高和风化反应活化能低而被强调。由于活化能决定了风化速率对温度变化的敏感性，全球变冷将通过云母相对优先的风化来增加大陆通量的Sr-87/Sr-86比率。根据裸露上陆壳云母矿物的平均锶含量和Sr-87/Sr-86比值，建立了动力学模型来研究河流Sr-87/Sr-86对全球气温变化的响应。模型结果表明，全球变冷引起的河流Sr-87/Sr-86增加可以单独解释自3.4 Myr B.P.以来海水Sr-87/Sr-86增加的大部分。这一发现强调了风化动力学是将全球气候变化与海洋Sr-87/Sr-86曲线联系起来的重要机制；在气候-风化-构造联系中应谨慎使用海洋Sr-87/Sr-86曲线。 (c) 2006 Elsevier B.V 保留所有权利。
The knowledge of how and why marine Sr-87/Sr-86 ratios changed helps understand the impacts of many processes on the global biogeochemical cycle in the geological past. Here we examine the possible influence of global cooling on the evolution of marine Sr-87/Sr-86 curve by a kinetic approach. The importance of mica weathering is emphasized due to its high content of radiogenic strontium and low activation energy in weathering reaction. Since the activation energy determines the sensitivity of weathering rate in response to temperature changes, global cooling will increase the Sr-87/Sr-86 ratio of continental flux by relatively preferential weathering of mica. Based on the average strontium contents and Sr-87/Sr-86 ratios of the mica minerals in the exposed upper continental crust, a kinetic model is established to survey the response of riverine Sr-87/Sr-86 to the changes of global temperatures. The model result indicates that the increase of riverine Sr-87/Sr-86 caused by global cooling can solely account for most of the increase in seawater Sr-87/Sr-86 since 3.4 Myr B.P. This finding emphasizes that the weathering kinetics is an important mechanism relating the global climate change to marine Sr-87/Sr-86 curve; and the marine Sr-87/Sr-86 curve should be used with great care in the climate-weathering-tectonic connections. (c) 2006 Elsevier B.V All rights reserved.