Fig. 16. Evidence for fluid flow associated with faults. (A) Open fracture filled with calcite. Cross-polarized light image with quarter-wave plate in. (B) Calcite-filled vein (C), with iron oxide fill (dark material) subparallel to the fine-grained fault gouge of the Horton Creek fault. P is pumice. Cross-polarized light image. (C) Open fractures (f) cutting pumice (P) and feldspar (F). Red iron-oxide staining lies in a fault zone. Cross-polarized light image with reflected light. (D) Fine-grained fault gouge that cuts calcite (C) at the Crucifix site. Cross-polarized light image.