Structural Controls And Genesis Of Carlin-Type Gold Deposits In The Evolution Of The Basin And Range Province

The structural setting of disseminated-replacement gold deposits of the Carlin-type and other aspects of their genesis are closely related to events which took place during the evolution of the Basin and Range province. The deposits formed as a result. of chemical and physical processes which took place at shallow depths in the roots of hot spring systems at moderate temperatures (about 200°C) and low pressures (about 25 bars) (Radtke and Dickson, 1974). Locations of Carlin-type gold deposits in the Basin and Range province are shown in Figure 1. Most of the block-faulted mountain ranges in the Great Basin formed by tectonic activity that happened since Miocene time, although faulting in some places probably began in Eocene to Oligocene time (Hamilton and Myers, 1966). The Carlin-type deposits are spatially related to Basin and Range-type faults: Many deposits, such as Getchell, Pinson, Preble, and Cortez, occur along the flanks of ranges, while other deposits, including Carlin (Radtke, 1974) occur within the ranges in areas characterized by crosscutting and intersecting high-angle or Basin and Range-type faults. The association of the ore deposits with Basin and Range-type faults is evidence that ore deposition is young, Miocene or later. The steep, high-angle faults played three roles: first, they provided deep channels for upward-flowing solutions; second, in preparing the rocks for fluid penetration by brecciation and general rock dislocation; and third, they moved sedimentary carbonate rocks, favorable for ore deposition, from deep levels to near-surface positions where the physico-chemical conditions were more suitable for the deposition of ore.