Poorly crystalline carbonaceous matter in high grade metasediments: implications for graphitisation and metamorphic fluid compositions
Poorly crystalline carbonaceous matter in high grade metasediments: implications for graphitisation and metamorphic fluid compositions
复制标题
高品位变沉积岩中的低结晶碳质：对石墨化和变质流体成分的影响
DOI：
10.1007/bf00310693
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发表时间：
1994
影响因子：
3.5
通讯作者：
A. Fallick
中科院分区：
文献类型：
--
作者：
D. Large;A. Christy;A. Fallick
在Trois Seigneurs地块的绿泥石到硅线石级的变质沉积物中观察到结晶性差的碳质物质，与其他碳结晶度研究相反，在上部绿片岩相条件下观察到结晶良好的石墨。通过透射电镜鉴定出四种类型的碳颗粒；球状碳、复合薄片、均质薄片和结晶石墨。球状碳和复合薄片是结晶性差的微孔碳。均质薄片在电子束中分解，可能由重挥发性碳氢化合物组成。石墨仅限于来自逆行剪切带的样品，并且经常与球状碳一起出现。沉积中缺乏石墨化可能是碳质物质的微孔结构与低fO2相结合的结果。三期沉积中碳质物质的保存与被高XH2O流体同变质作用外部缓冲的沉积是不相容的。内部缓冲作用的另一种假设更适合用来解释三岛沉积中的碳质物质。
Poorly crystalline carbonaceous matter was observed in chlorite to sillimanite grade metasediments from the Trois Seigneurs Massif, in contrast to other studies of carbon crystallinity which observed well crystallised graphite under upper greenschist facies conditions. Using transmission electron microscopy four types of carbon particle were identified; globular carbon, composite flakes, homogeneous flakes and crystalline graphite. Globular carbon and composite flakes are poorly crystalline microporous carbon. Homogeneous flakes decompose in the electron beam and are probably composed of heavy volatile hydrocarbons. Graphite is confined to samples from retrograde shear zones and often occurs with globular carbon. The lack of graphitisation in metasediments is probably a consequence of the microporous structure of the carbonaceous matter combined with low fO2. The preservation of carbonaceous matter in the Trois Seigneurs metasediments is not compatible with the metasediments having been externally buffered by a high XH2O fluid syn-metamorphism. An alternative hypothesis of internal buffering is preferred to explain the carbonaceous matter in the Trois Seigneurs metasediments.