Fig. 1
From: Reactivation of variably sealed joints and permeability enhancement in geothermal reservoir rocks
Pre-deformation microstructure. Photographs of samples prior to deformation (a, d, g), showing the extent of secondary mineral precipitation in naturally formed joints. Scanning electron microscope (SEM) images of the matrix (b, e, h) and joints (c, f, i) of the studied sandstones. a, b, c Couches Intermédiaires (Box 117); d, e, f Couches de Karlstal (Box 179); g, h, i Couches de Trifels (Box 388). Qz: quartz, Kfs: K-feldspar, Cal: calcite, Sd: siderite, Ilt: illite