Deformation-Induced and Reaction-Enhanced Permeability in Metabasic Gneisses, Iona, Scotland: Controls and Scales of Retrograde Fluid Movement

Figure 4

Photomicrographs of fracture systems. (a) Brecciated texture of epidosite cataclasite (thin section I), with mylonitized quartz-filled vein (top left) and fragments of mylonitized quartz-filled vein (arrowed) within individual clasts of epidosite in a fine-grained epidote matrix (PPL); (b) cataclasite composed of clasts of amphibole in an epidote-rich matrix (thin section G) (PPL); (c) cataclasite of amphibole gneiss, cut by quartz- (qz-) and chlorite- (chl-) filled vein (thin section H) (PPL); (d) large highly deformed clast containing brecciated quartz and albite within epidote-rich altered cataclasite (thin section H). Calcite-bearing vein (cal) towards the top of the view (crossed polarized light: XPL); (e) thin band of quartz mylonite within large quartz grain in pegmatite. Original quartz shows extensive subgrain development (thin section F) (XPL); (f) mylonite texture in quartz vein that cuts the epidosite pictured in (a) (thin section I) (XPL); (g) X-ray distribution map showing Ca- (orange), Na- (green), and Mg- (blue) part of thin section G, with central epidote-bearing (intense orange) cataclasite containing small relict clasts of albite (green) and amphibole (pink). Calcite veins show as red (thin section G).

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