The nature of shock-induced calcite (CaCO3) devolatilization in an open system investigated using a two-stage light gas gun
The nature of shock-induced calcite (CaCO3) devolatilization in an open system investigated using a two-stage light gas gun
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使用两级轻气枪研究开放系统中冲击引起的方解石 (CaCO3) 脱挥发分的性质
DOI：
10.1016/j.epsl.2012.05.022
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
S.
中科院分区：
文献类型：
--
作者：
Kurosawa;K.;Ohno;S.;Sugita;S.;Mieno;T.;Matsui;T.;Hasegawa;S.
利用二级轻气枪和四极质谱仪在开放体系中研究了冲击波作用下无孔方解石的脱碳酸反应。我们开发了一种新的实验技术，避免了枪中使用的加速气体的化学污染。同时进行高速成像和光谱观测，以研究实验过程的有效性。脱碳效率沿着Hugoniot曲线在50 GPa左右变化，这是以前理论研究预测的近似初始脱碳压力。在低于50 GPa阈值的压力下检测到脱碳，尽管效率较低，但正如在先前的实验研究中所观察到的那样，这可能是由于剪切带等过程导致的能量局部化的结果。基于熵方法和杠杆规则，在实验条件下，建立了冲击波诱导等熵释放脱碳的简单理论模型。当冲击压力超过50 GPa时，CO2释放量与峰值冲击压力的函数关系与实验结果吻合较好，表明冲击诱导CO2气体的释放量仅取决于冲击诱导熵增益和环境压力下初始脱碳酸和完全脱碳酸的熵。在今后的实验中，新方法将用于定量测量其他固体材料产生的撞击气体的化学成分。所提出的方法是有用的，在确定所需的峰值冲击压力的地质材料的汽化/脱挥发分，并估计最终的化学成分的影响引起的蒸汽云。
The shock-induced decarbonation of non-porous calcite was investigated in an open system over a wide range of peak shock pressures using a two-stage light gas gun and a quadrupole mass spectrometer. We developed a new experimental technique that avoids chemical contamination from the acceleration gas used in the gun. High-speed imaging and spectroscopic observations were conducted simultaneously to investigate the validity of the experimental procedure. The decarbonation efficiency along the Hugoniot curve changed at around 50GPa—the approximate incipient decarbonation pressure predicted by the previous theoretical studies. Decarbonation, albeit at a low efficiency, was detected at pressures below the 50GPa threshold, as observed in previous experimental studies, possibly as a result of energy localization due to a process like shear banding. A simple theoretical model for shock-induced decarbonation during isentropic release was constructed based on the entropy method and the lever rule, assuming the experimental conditions. The predicted amount of released CO2as a function of the peak shock pressure agreed well with the experimental results at pressures exceeding 50GPa, strongly suggesting that the amount of shock-induced CO2gas was determined only by the shock-induced entropy gain and by the entropies for incipient and complete decarbonation at the ambient pressure. In future experiments, the new method will be used for quantitative measurements of the chemical composition of impact-induced gases derived from other solid materials. The proposed method is useful in determining the peak shock pressure required for vaporization/devolatilization of geologic materials and for estimating the final chemical composition of impact-induced vapor clouds.