李久庆, 秦 勇, 陈义林, 申 建, 李 耿, 郑长东. 闽西南永安煤田煤系石墨显微组分光学特征及石墨化组分形成路径[J]. 煤炭学报, 2022, 47(12): 4323-4335.
引用本文: 李久庆, 秦 勇, 陈义林, 申 建, 李 耿, 郑长东. 闽西南永安煤田煤系石墨显微组分光学特征及石墨化组分形成路径[J]. 煤炭学报, 2022, 47(12): 4323-4335.
LI Jiuqing, QIN Yong, CHEN Yilin, SHEN Jian, LI Geng, ZHENG Changdong. Optical characteristics of macerals and formation path of graphitic components in coal⁃based graphite in the Yongan coalfield,Southwest Fujian[J]. Journal of China Coal Society, 2022, 47(12): 4323-4335.
Citation: LI Jiuqing, QIN Yong, CHEN Yilin, SHEN Jian, LI Geng, ZHENG Changdong. Optical characteristics of macerals and formation path of graphitic components in coal⁃based graphite in the Yongan coalfield,Southwest Fujian[J]. Journal of China Coal Society, 2022, 47(12): 4323-4335.

闽西南永安煤田煤系石墨显微组分光学特征及石墨化组分形成路径

Optical characteristics of macerals and formation path of graphitic components in coal⁃based graphite in the Yongan coalfield,Southwest Fujian

  • 摘要: 石墨作为重要的矿物类非金属矿产,是炭素材料的基础原材料,煤系石墨是煤变质形成的 一种隐晶质石墨,在新型碳材料领域应用广泛。 为研究煤系石墨显微组分的光学特征和石墨化显 微组分的形成路径,以闽西南永安煤田广泛发育的煤系石墨为研究对象,采用不同观察组合的光学 显微镜和扫描电镜等方法,识别煤系石墨显微组分组成及其光学特征,探讨不同显微组分的趋石墨 化行为和形成方式。 结果表明,煤系石墨显微组成以煤原有显微组分的变镜质体为主(86.15%~ 97.24%),变惰质体次之,偶见变类脂体,新生显微组分包括各向异性体和石墨微晶(0.68% ~ 7.32%)。 反射单偏光旋转载物台观察,变镜质体呈多色性和强光学各向异性,不同显微亚组分之 间光性差异明显,交叉偏光清晰观察植物组织结构,是区分亚组分的有效方法。 变惰质体以变丝质 体为主,反射单偏光观察以弱光学各向异性为特征,交叉偏光观察近全黑,基本保持光学“惰性”。 变类脂体中变孢子体、变角质体和变树脂体形态清晰,多色性和光学各向异性强于变镜质体。 流动 状结构各向异性体以透镜状或条带状依附于原显微组分表面,石墨微晶产状有微裂缝充填和胞腔 充填两种,以前者为主,呈片状、针状和镶嵌状形貌,簇状集合体产出。 正交偏光加石膏试板观测条 件下,石墨微晶呈一级黄和二级蓝干涉色,指示石墨微晶不同的排列方向,等色区线径 10 ~ 50 μm 的石墨微晶数量最多且分布最广。 扫描电镜电子能谱显示,石墨微晶呈不规则鳞片状并见流动状 结构和气泡膜状结构,元素以碳为主。 富氢变镜质体和变类脂体是煤系石墨中新生显微组分的主 要碳质来源,煤系石墨趋石墨化显微组分以 3 种路径形成:一是充填于原显微组分颗粒边界的渗 出沥青体,形成方式类似于沥青焦;二是高活性变类脂体受热软化熔融冷却结晶形成各向异性 体;三是活性显微组分热解产生的含碳气体在开放空间以气相沉积方式形成石墨微晶。 煤系石 墨的形成和分布受岩浆-构造热活动制约,岩浆热力与侵位压力是闽西南煤系石墨形成的主要 地质因素。

     

    Abstract: As an important non⁃metallic mineral, graphite is a basic raw ingredient of carbon materials. Coal⁃ based graphite is one of cryptocrystalline graphite formed by coal metamorphism, which is widely used in the produc⁃ tion of new carbon materials. To study the optical characteristics of macerals and the formation path of graphitic macer⁃ als in the coal⁃based graphite, several coal⁃based graphite samples in the Yong’an Coalfield in southwest Fujian Prov⁃ ince was selected. Using an optical microscope with different observation modes and a scanning electron microscope, the macerals and its optical properties of the coal⁃based graphite were characterized. The graphitization behavior and formation mode of graphitic macerals were explored as well. The results showed that the macerals of coal⁃ based graphite were dominated by meta⁃vitrinite with a proportion of 86.15%-97.24%, followed by meta⁃inertinite and meta⁃liptinite. Anisotropic body and graphite crystallite were newly formed components with a proportion of 0.68%-7.32%. Under the observation of reflected single⁃polarized light combined with rotating platform, the sub⁃macerals meta⁃vitrinite showed a pleochroism and strong optical anisotropy, along with significant differences a⁃ mong macerals. The plant tissue structure was clear under a cross⁃polarized light, which was an effective tool to distin⁃ guish the meta⁃vitrinite. The meta⁃inertinite was mainly composed of meta⁃fusinite, with a weak optical anisotropy un⁃ der a reflected single⁃polarized light, and it was almost black under a cross⁃polarized light observation, exhibiting an optical ‘inertia’ feature. The meta⁃sporinite, meta⁃cutinite and meta⁃resinite of meta⁃liptinite presented clear mor⁃ phologies, and its pleochroism and optical anisotropy were stronger than those of meta⁃vitrinite. Flow⁃like anisotropic bodies were attached to the original macerals’ surface in a lens⁃like or strip⁃like shape. Graphite crystallite occurred in two modes, e.g., micro⁃crack filling and cell cavity filling. The former was common, showing a flake, needle⁃like, and mosaic morphology as a cluster aggregate. Using the orthogonal polarized light plus a gypsum plate, the graph⁃ ite crystallite showed an interference color of the first order yellow and second order blue, indicating a different ar⁃ rangement orientation of graphite crystallites. The graphite crystallites with line diameters of 10-50 μm in the isochro⁃ matic zone were the most common one. Under a scanning electron microscopy and an electron probe analysis, the graphite crystallites occurred mostly as irregular flakes with flow⁃ and bubble⁃like structures, showing the features of pure carbon. The hydrogen⁃rich meta⁃vitrinite and meta⁃liptinite were the main carbon sources of the newly formed components in the coal⁃based graphite, and there were three formation paths of graphitization macerals. The first was an exsudatinite filled at the boundary of the original maceral particles, which was similar to that of asphalt coke. The second was the anisotropic body formed by thermal softening, melting, and cooling crystallization of a meta⁃liptinite. The third was the carbon⁃containing gas formed by the pyrolysis of active macerals producing graph⁃ ite crystallites in an open space by the vapor deposition. The formation and distribution of coal⁃based graphite were re⁃ lated to tectonics and igneous activities. The combined magmatic heat and emplacement pressure were the main geolog⁃ ical factors of the formation of coal⁃based graphite in southwest Fujian Province.

     

/

返回文章
返回