海洋内部板块的爆炸性喷发直接来自地幔
Charlotte L DeVitre1, Esteban Gazel1, Ricardo S Ramalho2,3,4
1Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14850.
概括
海洋内板火山,如Fogo,由于来自地幔的挥发性丰富的岩而具有爆炸性. 深层二氧化碳 (CO2) 排放驱动这些爆炸性喷发,影响全球挥发性循环.
科学领域:
- 地质化学和火山学.
- 深层地球过程和挥发性循环.
背景情况:
- 了解岩的挥发性含量对于喷发过程和地球深层循环至关重要,影响行星的可居住性.
- 之前关于岩挥发物的研究主要集中在俯冲区,对板内火山活动及其全球作用的关注有限.
- 马菲火山,尽管它们的丰富,往往被低估,因为它们的爆炸潜力比状火山.
研究的目的:
- 为了研究来自佛得角的福戈火山原始岩的挥发性含量和来源.
- 评估海洋内部板块岩石火山活动在全球波动周期中的作用.
- 了解驱动不和地形系统中的爆炸性喷发的机制.
主要方法:
- 分析Fogo火山原始融化含量 (MI) 数据,重点关注主体和融化主要元素组成.
- 计算融化Mg# (数) 以确定原始的岩组成.
- 在融物中确定挥发性度 (CO2,H2O,S,F,Cl) 和氧化状态 (NiNiO/NiNiO+1).
主要成果:
- 福戈火山原始的融化含量 (融化Mg# 70-71%) 显示了氧化和高度挥发性丰富的岩石.
- 挥发性度高达2重%的CO2,2.8重%的H2O,6,000 ppm的S,1,900 ppm的F和1,100 ppm的Cl,将Fogo归类为一个全球的终端成员.
- 计算的岩储存深度表明地幔起源 (~20-30公里),深度二氧化碳脱溶压力高达~800MPa.
结论:
- 海洋内部板块爆炸性喷发,以Fogo为例,样本含有挥发性物质丰富的地幔来源.
- 高度的挥发物,特别是从地幔源中继承的二氧化碳,维持了这些喷发.
- 深度二氧化碳排放是这些系统中岩上升和爆炸的主要驱动因素,突出了它们在全球挥发性运输中的重要性.
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