富含二氧化碳的酸盐在地球上层地幔中融化
Rajdeep Dasgupta1, Ananya Mallik, Kyusei Tsuno
1Department of Earth Science, Rice University, Houston, Texas 77005, USA. Rajdeep.Dasgupta@rice.edu
Nature
|January 11, 2013
概括
实验表明,地球地幔中碳酸的融化开始比以前想象的更深,影响行星进化和地幔特性. 这种深层融化的产生解释了海洋上层地幔中关键的地质观测.
科学领域:
- 地质化学和地质物理学
- 行星科学 行星科学
- 地幔石器学地幔石器学
背景情况:
- 地球上层地幔的融化对于行星的热进化,挥发性物质的运输和地幔的特性至关重要.
- 酸盐化的确切深度和条件,特别是在碳化矿中,仍然不确定.
- 地质数据表明,在约200公里的深度存在融化物,但大型融化物通常与较浅的区域有关.
研究的目的:
- 实验性地限制压力-温度条件和碳酸矿中化酸盐开始的深度.
- 为了研究二氧化碳 (CO2) 和水 (H2O) 对中洋山脊下的地幔固体的影响.
- 将实验结果与海洋上层地幔的地球物理观测相关联,包括低速度区域和电导率.
主要方法:
- 在高压和高温实验中,碳酸矿样本的压力范围为2至5GPa.
- 对碳酸融化曲线的压力-温度斜率的分析.
- 模拟微量H2O对固体和融化生成深度的影响.
主要成果:
- 碳化酸融化的压力-温度倾斜率比无挥发性二氧化的固体更.
- 在大约180公里深处,干燥的二氧化碳化石与山脊下的二氧化碳的化物融化开始.
- 纳入50-200ppm的H2O压抑了固体,将酸融化的开始延长到220-300公里的深度,用于含有~100ppmCO2的亚地幔.
结论:
- 碳化酸在氧化还原阵线 (250-200公里深) 的融化生成解释了海洋的低速度区域和地幔电导率.
- 深层上层地幔可能富含二氧化碳,但缺乏H2O,这是融特性和导电率数据所表明的.
- 碳酸融化物限制了碳酸的稳定性,并控制了碳,H2O和不兼容元素在中洋山脊上的流动.
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