Vein structures of the Peru Margin, Leg 112

Abstract

Mud-filled dewatering veins occur in four styles: wide discrete gashes, veins along extensional microfaults, tension-gash arrays, and injections into tension gashes about slump-fold noses. Formation of mud veins occurs during sediment dewatering, perhaps initiated by the collapse of diatom frustules during compaction, or by overloading during downslope slumping and sliding. Carbonate-filled veins in Peru margin samples include tension gashes and wide, banded zones filled with calcite or dolomite spar; these probably result from filling of open fractures. Some sparry veins are crosscut by dewatering veins filled with calcareous mud, suggesting that the carbonate veins begin to form very early, before mud interbeds have dewatered. -from Authors