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Fig. 6 | Geothermal Energy

Fig. 6

From: Pore-fluid-dependent controls of matrix and bulk thermal conductivity of mineralogically heterogeneous sandstones

Fig. 6

Thin section photographs of sandstone samples (blue stained epoxy), showing a altered alkali feldspar showing dissolution effects (red arrow), b ferrogeneous ghost structure remains of completely dissolved alkali feldspar (red arrows), c, d authigenic, worm-like kaolinite booklets (red arrows), resulting from alkali feldspar degeneration (a Buntsandstein sandstone, Hardegsen Formation; bd Keuper sandstone, Löwenstein Formation/Upper Burgsandstein)

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