Abstract

The complex structural setting of the Goldstrike mining district developed over a period of time extending from the Late Cretaceous to the late Tertiary. The oldest structures are thrust faults and asymmetrical folds that reflect southeast directed compressional tectonism related to the Sevier orogenic episode. A thick conglomerate of presume Late Cretaceous to Paleocene (or Eocene?) age in the eastern part of the district reflects erosion of the highland that was created during this interval. Continued erosion produced a region of very low topographic relief prior to the deposition of a widespread but relatively thin sequence of Eocene (?) and Oligocene lacustrine sediments containing two interbedded ash flow tuff units. Lacustrine sedimentation gave way to widespread volcanism in Miocene time. Basin-Range faulting and local doming probably began during the later part of the volcanic episode and continued thereafter. A complex network of arcuate, braided faults developed in the Goldstrike area during this interval and displacements on these resulted in the formation of many large and small, east-west to northeast elongate grabens, horsts, and tilted blocks. Several faults have had large scale strike-slip displacement along them. Repeated intermittent displacements of both a dextral and sinstral nature occurred on faults of different orientations. The district appears to have been localized by the intersection of at least two, and probably three, important structural trends.