Leonardson, R.W., Barrick Gold Exploration, Inc., HC 66, Box 1250, Crescent Valley, Nevada 89821
Mapping in the Pipeline, Gold Acres, and gap open pits in addition to logging old and new drill holes has revealed an interesting geological story. The ore deposits and their host rocks are dominated by low angle compressional structural architecture with relatively minor high angle structural control.
Lower plate carbonate rocks, the Roberts Mountains thrust (RMT), and overlying upper plate siliciclastic rocks in the mines forms an allochthonous sequence thrust eastward over a potentially normal upper plate over lower plate sequence at depth. The allochthonous mine rocks (herein termed Mine Rocks) comprise a large folded hanging wall anticline that contains the entire upper plate sequence, the RMT, and lower plate Devonian through Cambrian carbonate sequence above the Abyss thrust fault. An age younger than early Mississippian is suggested for this event because the RMT has been involved in the folding.
The Cretaceous Gold Acres quartz monzonite stock is contained within the Mine Rocks but its timing relationship with thrusting has not been established. Its magnetic metamorphic aureole in conjunction with the leading limb of the hanging wall anticline created a locus for mineralization.
A potential disruption of the hanging wall anticline in several of the carbonate units is suggested by extension that slightly pulled the anticline apart and locally thinned some of the carbonate units. This created tectonic damage zones that localized mineralization in the late Eocene. At Pipeline, rock damage zones, alteration, and mineralization appear to be confined to the mine rocks indicating non-involvement of rocks below the Abyss thrust fault.