Minerals Filling in Anhydrite Dissolution Pores and Their Origins in the Ordovician Majiagou Formation of the Southeastern Ordos Basin, China

Figure 4

Minerals filling in anhydrite dissolution pores of the Ordovician carbonate in Yican 1 well in the southeastern Ordos Basin. (a) Anhydrite nodule-bearing dolomite in Yi14 well, 2298.6 m, Ma₅¹. (b) Anhydrite dissolution pores in the core of Yican 1 well, 2635 m, Ma₅¹. (c) Anhydrite dissolution pores filled with dolomite, calcite, and pyrite in Yican 1 well, 2642.5 m, Ma₅¹, sample 96. (d) Anhydrite dissolution pores filled with dolomite, calcite, and quartz, 2641.4 m, Ma₅¹, sample 92. (e) Anhydrite dissolution pores filled with dolomite, calcite, and pyrite, 2642.5 m, Ma₅¹, sample 96. (f) Ultraviolet fluorescence photo shows hydrocarbon inclusions enriched in dolomite at the bottom of the nodule and lattice defect of calcite at the top of nodule, 2642.5 m, Ma₅¹, sample 96. (g) Saddle dolomite showing undulose extinction in the anhydrite dissolution pores, 2951.5 m, Ma₂, sample 242. (h) Calcite with crossed twinning and euhedral quartz filling in anhydrite dissolution pores, 2641.4 m, Ma₅¹, sample 92. (i) Anhydrite dissolution pores filled with calcite and quartz, 2642.5 m, Ma₅¹, sample 96. (j) Anhydrite dissolution pores filled with dolomite and calcite, 2640.9 m, Ma₅¹, sample 90. (k) Ultraviolet fluorescence photo shows hydrocarbon inclusions enriched in dolomite at the bottom of the nodule and lattice defect of calcite at the top of nodule, 2640.9 m, Ma₅¹, sample 90. (i) SEM photo of calcite, pyrite, and quartz filling in the anhydrite dissolution pores, 2641.4 m, Ma₅¹, sample 92.

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