Abstract Six solid bitumen samples from Paja Formation (Cretaceous of Colombia) were optically, chemically and structurally characterized using bulk chemistry, reflectance indicating surface (RIS), micro-Raman and X-ray diffraction (XRD) parameters. The volatile matter and carbon contents and high random reflectance (Ro%) placed these solid bitumens in the category of cata-impsonites according to Jacob's classification. RIS axes (RMAX, RINT and RMIN) form almost a sphere, and consequently, the anisotropy (Ram or bireflectance values) of these materials is very weak, comparatively to other carbonaceous materials (coals) of similar degree of evolution. The weak anisotropy character of the solid bitumen is related to the absence of pressure in the system, which did not promote the orientation of the basic structural units (BSUs) in a three-dimensional arrangement. The degree of ordering evaluated by Raman parameters, such as full width at half maximum (FWHM) of the D1 and G bands, and XRD parameters, including d002 and crystallite sizes Lc and La, showed that the solid bitumens of the Paja Formation have a low structural order equivalent to high-rank coals, specifically anthracites B (3.0% ≤ Ro 4.0%). The discrepancy between high reflectance and low degree of structural order can explain why some of the equations used to estimate equivalent vitrinite reflectance (Ro eq. Vite) from solid bitumens do not work universally. Taking in consideration several equations available in the literature, Jacob's equation ( Jacob, 1989 ) was the one that fitted the Ro eq. Vite values in the range of 3.0% to 4.0%, which parallels with the degree of structural order obtained for the solid bitumens. Consequently, Jacob's equation can now be extended to solid bitumen in the range of cata-impsonites.

中文翻译：

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高反射率固体沥青 (Impsonites) 的光学参数和微观结构特性。对其用作有机成熟度指标的思考

摘要 使用本体化学、反射指示表面 (RIS)、显微拉曼和 X 射线衍射 (XRD) 参数对来自 Paja 地层（哥伦比亚白垩纪）的六个固体沥青样品进行了光学、化学和结构表征。根据雅各布的分类，挥发性物质和碳含量以及高随机反射率 (Ro%) 将这些固体沥青置于 cata-impsonites 类别中。RIS 轴（RMAX、RINT 和 RMIN）几乎形成一个球体，因此，与演化程度相似的其他碳质材料（煤）相比，这些材料的各向异性（Ram 或双反射率值）非常弱。固体沥青的弱各向异性特征与系统中没有压力有关，这并没有促进基本结构单元（BSU）在三维排列中的定向。通过拉曼参数（例如 D1 和 G 带的半峰全宽 (FWHM)）和 XRD 参数（包括 d002 和微晶尺寸 Lc 和 La）评估的有序度表明，Paja 地层的固体沥青具有相当于高阶煤的低结构秩序，特别是无烟煤 B (3.0% ≤ Ro 4.0%)。高反射率和低结构有序度之间的差异可以解释为什么用于估计固体沥青的等效镜质体反射率 (Ro eq. Vite) 的某些方程不能普遍适用。考虑到文献中可用的几个方程，Jacob 方程 (Jacob, 1989) 是拟合 Ro 方程的方程。Vite 值在 3.0% 到 4 的范围内。0%，这与固体沥青获得的结构有序程度相一致。因此，Jacob 方程现在可以扩展到 cata-impsonites 范围内的固体沥青。