当前位置: X-MOL 学术Contrib. Mineral. Petrol. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Pressure dependence of graphitization: implications for rapid recrystallization of carbonaceous material in a subduction zone
Contributions to Mineralogy and Petrology ( IF 3.5 ) Pub Date : 2020-03-16 , DOI: 10.1007/s00410-020-1667-2
Yoshihiro Nakamura , Takashi Yoshino , Madhusoodhan Satish-Kumar

We report the results of kinetic experiments of graphitization at various pressures (0.5–8.0 GPa) and durations (1 s to 24 h) at 1200 °C. The natural carbonaceous material in sedimentary rocks from the Shimanto accretionary complex and the Hidaka metamorphic belt, Japan, underwent systematic changes in crystallinity and morphology with increasing pressure. To assess the pressure dependence of graphitization, we adopted three approaches to formulating the graphitization kinetics using a power law rate model, a Johnson–Mehl–Avrami–Kolmogorov model, and a superposition method. Activation volumes of − 21.7 ± 3.0 to − 45.7 ± 4.5 cm 3 mol −1 and − 0.7 ± 0.2 to − 16.8 ± 1.8 cm 3 mol −1 were obtained for pressures from 0.5 to 2.0 GPa and 2.0 to 8.0 GPa, respectively. Such large negative activation volumes might arise from structural modification and compression in the primary carbonaceous material. We applied the experimental data to the Arrhenius-type equation of graphitization, extrapolated to geological P–T–t conditions. Our model predicts that carbonaceous material undergoing metamorphism for ~ 10 Myr at pressures of 0.5–3.0 GPa will begin to crystallize at around 350–420 °C and transform fully to ordered graphite at around 450–600 °C, depending on the peak pressure. Thus, natural graphitization might proceed much more rapidly than previously estimated, owing to the large negative activation volumes for the reaction rate. This indicates that subducted carbonaceous materials will completely convert to fully ordered graphite by rapid recrystallization and metamorphic devolatilization before reaching sub-arc depths (< 100 km).

中文翻译:

石墨化的压力依赖性:对俯冲带中碳质材料快速再结晶的影响

我们报告了在 1200°C 下在不同压力 (0.5–8.0 GPa) 和持续时间 (1 秒到 24 小时) 下石墨化的动力学实验结果。日本四万十增生杂岩和日高变质带沉积岩中的天然碳质材料随着压力的增加,结晶度和形态发生系统变化。为了评估石墨化的压力依赖性,我们采用了三种方法来使用幂律率模型、Johnson-Mehl-Avrami-Kolmogorov 模型和叠加方法来制定石墨化动力学。对于0.5至2.0 GPa和2.0至8.0 GPa的压力,分别获得- 21.7 ± 3.0至- 45.7 ± 4.5 cm 3 mol -1 和- 0.7 ± 0.2至- 16.8 ± 1.8 cm 3 mol -1 的活化体积。如此大的负活化体积可能来自主要含碳材料的结构改性和压缩。我们将实验数据应用于 Arrhenius 型石墨化方程,外推到地质 P-T-t 条件。我们的模型预测,在 0.5–3.0 GPa 压力下经历约 10 Myr 变质的碳质材料将在 350–420 °C 左右开始结晶,并在 450–600 °C 左右完全转变为有序石墨,具体取决于峰值压力。因此,由于反应速率的负活化体积较大,自然石墨化可能比先前估计的进行得更快。
更新日期:2020-03-16
down
wechat
bug