Characteristics of an Altered Diabase Dike in a Coal Seam: A Case Study from the Datong Coalfield, Shanxi, China

Figure 5

(a) Plane-polarized light (PPL), (b) cross-polarized light (XPL), (c) PPL, and (d) XPL photomicrographs of TS3. Euhedral plagioclase (Pl), olivine (Ol) (the cracks and margins of olivine changed into serpentine), and subhedral augite (Aug) were partially altered into chlorite and smectite. (e) PPL and (f) XPL photomicrographs of TS5. Augite was mostly converted into carbonate and mixtures of chlorite and smectite, while euhedral olivine was completely converted into carbonate minerals. (g) PPL and (h) XPL photomicrographs of TS5. Carbonate mineral spherulite (Cb). (i) PPL, (j) XPL, (k) PPL, and (l) XPL photomicrographs of TS2. Euhedral plagioclase was completely replaced by fine-grained clay minerals, and mafic minerals were completely converted into brown mixtures of chlorite, smectite, and carbonate minerals.

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