Promotion of graphite formation by tectonic stress – a laboratory experiment
Promotion of graphite formation by tectonic stress – a laboratory experiment
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DOI：
10.1111/j.1365-246x.2005.02395.x
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发表时间：
2005-03
影响因子：
2.8
通讯作者：
G. Nover;J. Stoll;J. V. D. Gönna
中科院分区：
文献类型：
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作者：
G. Nover;J. Stoll;J. V. D. Gönna
总结在原位压力和温度条件下，在上绿片岩相条件下，对无烟煤、黑页岩和合成方解石/无烟煤混合物上的较不有序六方碳的石墨化进行了研究。通过差热分析（DTA）和热重分析（TG）检测，无烟煤在100 ℃至850 ℃的温度范围内（450 ℃时为9.9%重量）表现出挥发分的连续损失。能量色散X射线衍射（EDX）揭示了广泛的无定形002石墨反射，而p，T-处理后，检测到几乎完美的结晶石墨碳。同时在0.7至100 kHz的频率范围内测量电导率。作为时间的函数，体电阻率在恒定压力和温度条件下（0.7 GPa，450 ℃）降低了约三个数量级，而复响应表现出阻抗虚部的连续降低。“准金属”导电现在占主导地位的电荷传输。施加压力，应变，温度和时间引起的有序性和以前的随机取向的碳片的互连程度的增加。实验结果是一种解释逆冲断层和推覆构造中大量存在结晶石墨的方法，这些构造以高导电性构造为特征。
SUMMARY Graphitization of less-ordered hexagonal carbon was studied under in-situ pressure and temperature conditions on anthracite, black shale and a synthetic calcite/anthracite mixture at upper greenschist facies conditions. Anthracite exhibited a continuous loss of volatiles in the temperature range from 100 ◦ Cu p to850 ◦ C (9.9 weight per cent at 450 ◦ C) as detected by Differential-Thermal-Analysis (DTA) and Thermo-Gravimetry (TG). Energy dispersive X-ray diffraction (EDX) revealed a broad amorphous 002 graphite reflection while after p, T-treatment nearly perfect crystallized graphitic carbon was detected. The electrical conductivity was measured at the same time in the frequency range from 0.7 up to 100 kHz. As a function of time the bulk resistivity was decreased by about three orders in magnitude at constant pressure and temperature conditions (0.7 GPa, 450 ◦ C), while the complex response exhibited a continuous decrease of the imaginary part of the impedance. ‘Quasi-metallic’ conduction now dominated the charge transport. Application of pressure, strain, temperature and time caused an increase in ordering and the degree of interconnection of the formerly randomly oriented carbon sheets. The experimental results are an approach towards the explanation of the abundant occurrence of crystalline graphite observed in overthrusts and nappe structures, which are distinguished by high-conductivity structures.