表生环境中镁同位素的地球化学循环

发布时间：2017-12-27 07:41

  本文关键词：表生环境中镁同位素的地球化学循环　出处：《地球科学进展》2016年01期 　论文类型：期刊论文

  更多相关文章： 镁同位素 风化作用 碳酸盐岩沉淀 水岩反应 地球化学循环

【摘要】：近些年表生环境中镁同位素分馏取得了一系列重要研究进展,这些新认识为深入理解表生环境中镁同位素地球化学循环奠定了基础。表生环境中镁同位素的地球化学循环主要涉及风化、河流搬运、碳酸盐沉淀、水岩反应等重要地质过程。风化过程中镁同位素发生显著分馏,硅酸盐风化产物中富集重的镁同位素,轻的镁同位素易进入水体。河流搬运过程中,镁同位素不发生分馏,但外源输入可能影响水体的镁同位素组成。河水汇入海洋后,碳酸盐沉淀过程可导致轻的镁同位素以碳酸盐的形式从海水中移出。在海底高温水岩反应过程中,海水中绝大多数的镁(80%~87%)都进入岩石,循环后的热液可能富集轻的镁同位素。海底低温水岩反应过程中海水的镁可以进入岩石并形成次生矿物,此过程的镁同位素分馏主要与次生矿物的形成有关。此外,海水中的镁易与黏土矿物发生交换反应,此过程黏土矿物倾向于吸附轻的镁同位素。总之,在表生环境中上地壳的镁(δ26Mg约为-0.22‰)经历风化作用、河流搬运、海洋贮存,最终以碳酸盐岩(δ26Mg一般小于-1‰)或与玄武岩发生反应的形式重新回到岩石圈。
[Abstract]:In recent years, a series of important research progresses in magnesium isotope fractionation in epigenetic environments have been made. These new understandings provide a basis for further understanding of the magnesium isotope geochemistry cycle in the epigenetic environment. The geochemical cycles of magnesium isotopes in the epigenetic environment are mainly related to the important geological processes such as weathering, river transport, carbonate precipitation, water rock reaction and so on. During the weathering process, the isotopes of magnesium are fractionated, and the heavy magnesium isotopes are enriched in the weathering products of the silicate, and the light magnesium isotopes are easy to enter the water body. In the process of river transportation, the isotopes of magnesium are not fractionated, but exogenous input may affect the composition of magnesium isotopes. After the river flows into the ocean, the carbonate precipitation process can lead to the removal of light magnesium isotopes from the sea water in the form of carbonate. In the process of high temperature water rock reaction in the sea bottom, most of the magnesium (80%~87%) in the sea water enters the rock, and the circulating hydrothermal solution may enrich the light magnesium isotopes. In the process of submarine low temperature water rock reaction, magnesium in seawater can enter the rock and form secondary minerals. The magnesium isotope fractionation in this process is mainly related to the formation of secondary minerals. In addition, magnesium in seawater is easily exchanged with clay minerals, and clay minerals tend to adsorb light magnesium isotopes. In conclusion, in the epigenetic environment, the upper crust magnesium (delta 26Mg is about -0.22 per thousand) has undergone weathering, river transportation and marine storage, and finally returned to the lithosphere with carbonate (delta 26Mg generally less than -1 per thousand) or basalt reaction.
【作者单位】： 中国地质科学院地质研究所国土资源部同位素地质重点实验室/大陆动力学国家重点实验室;
【基金】：国家自然科学基金项目“辽东裂谷带菱镁矿镁同位素特征及其对矿床成因的制约”(编号:41203004) 国土资源部行业专项基金项目“Fe;Mg同位素在辽东裂谷带菱镁矿及硼镁铁矿中的应用研究“(编号:201211074)资助~~
【分类号】：P597
【正文快照】： 1引言镁是主要的造岩元素,也是动植物所必需的生命元素,主要富集于地幔中,在地壳、水体和生物体中也广泛分布。镁可富集于岩浆过程早期结晶的矿物中(如橄榄石、辉石等),易在风化过程中以镁离子的形式进入水体。经水体搬运至海洋后,可通过碳酸盐的形式沉淀或在水岩反应过程中从，

本文编号：1340847