The character and distribution of mineralized fractures in the Kodiak Formation, Alaska: implications for fluid flow in an underthrust sequence

The Kodiak Formation, an accreted slate belt in southwest Alaska, experienced two major episodes of fracturing and mineralization in the Late Cretaceous-early Tertiary. The earlier of these episodes is related to underthrusting of sediments below a major decollement (D₁), whereas a later episode is marked by development of fold and thrust structures and a regionally pervasive slaty cleavage within the accretionary wedge (D₂). D₁ and D₂ veins suggest substantial fluid flow within an ancient subduction complex, with development of hydrofractures first in the footwall and then in the hanging wall of a basal decollement that stepped from shallow to deeper structural levels. -from Authors