Summary:
Goldrush deposit is part of the Cortez deposits, which are Carlin-type sedimentary rock-hosted deposits.
Exploration reveals that the deposit has a maximum thickness of 76 m, a width of about 425 m, and extends along strike for approximately 5,275 m. The deepest significant intercept is currently at 1,435 masl. The Goldrush system remains open to the north into Fourmile, to the southeast, and in multiple directions in the Ken Balleweg (KB) Domain.
Exploration to date shows that mineralization at Goldrush is primarily stratigraphically controlled, occurring within subunit 5 of the middle Wenban Formation and to a lesser extent along the contact between the Horse Canyon and Wenban formations.
Mineralization is associated with low-angle thrust faults and their related hanging wall antiforms that typically concentrate gold along fold hinges and/or east-dipping limbs. Gold occurs within extensive zones of decarbonatization and silicification within the Devonian rocks.
The system is marked by a large stratiform silicified and sulfidized breccia horizon from 15– 70 m thick that extends more than 7,000 m on a north–northwesterly strike.
Goldrush deposit length is 17,300 ft, deposit width is 1,400 ft, and deposit thicknesses range from 10-350 ft.
Mineralization
The main gold-bearing mineral is micrometre-sized arsenian pyrite that occurs as individual grains or as rims on pre-existing pyrite. Mineralization is primarily double-refractory and highly preg-robbing with both sulfides and active carbon present in the orebody. Mineralization exhibits low Ag:Au ratios with enrichment in arsenic, antimony, mercury, and thallium, and low base metal contents.
Seven mineralized domains are defined, from north to south, Crow’s Nest, Red Hill, KB North, KB South, 3½, Ranch, and Meadow.