Geology and Mining in Utah

The Duchesne fault zone (DFZ) in the Uinta Basin of Duchesne and Uintah Counties, Utah, consists of a 40-mile-long series of east-west trending, high-angle fault segments, lineaments, grabens, and folds.  Previous workers have noted individual normal faults with throws of up to 600' and claimed there was no evidence of horizontal movement.  It was also noted that the largest of these normal faults appear to die out within the upper Green River Formation at a depth of about 3200'.  Our research, utilizing surface mapping, outcrop kinematic reconstruction, plus vertical and horizontal well data demonstrate that, although high angle fault segments associated with the DFZ do loose vertical (dip-slip) throw at a relatively shallow depths, the fault zone is in fact a much larger feature that extends into basement rocks and records significant left-lateral (strike-slip and oblique-slip) movement.  The associated pop-up blocks, grabens and variable fault offsets relate to the complex, left lateral strike-slip and oblique-slip movement along the fault at different portions of its history.  During Eocene time, the DFZ influenced the development of the Uinta Basin, acting as a hinge point separating the deep basin to the north from the more shallow-dipping marginal-basin to the south.  Across the zone stratigraphic dips change from ranges within 1°–3° to ranges of 5°–7°.  The nature of the Basin’s structural rotation at the fault zone explains the relatively small surface grabens and anticlines that facilitates the decrease of throw with depth.  The area north of the hinge zone subsided more rapidly than south of the hinge zone, creating near surface tensional stresses that allowed shallow high-angle faults and associated grabens to form.  A long, shallow syncline that parallels the largest graben in the fault zone may record Laramide reactivation of deeper structures. The increased rate of subsidence at the developing DFZ exerted control on fluvial-deltaic deposition during Green River Formation time, allowing a large volume of deltaic sediments to be concentrated along its trace during certain intervals due to the increase in accommodation space. At other times, when the lake was higher, the DFZ separated marginal lacustrine sediments from profundal. The DFZ was reactivated during Neogene extension with abundant evidence of dip-slip kinematic indicators.  Although the DFZ forms a prominent escarpment of as much as 10'–20', no evidence has been currently found that indicates the fault zone has cut Pleistocene or younger deposits.
The DFZ also influences fluid migration, with oil and groundwater seeping to the surface along its many traces.  Hydrocarbon production is also impacted by the fault zone with wells results suggesting reservoir compartmentalization by fault strands at much deeper depths than previously documented.  Similar to previous workers, we found evidence of intense fracturing along the DFZ with resulting high oil IP’s and increased water cuts due to the enhanced permeability associated with these faults and fractures.  The evidence of both steady and pseudo-steady state boundary flow characteristics within the DFZ provide additional evidence that it is a much larger feature that continues through the deepest formations tested.

In 1906, the Guggenheim Exploration Company (GUGGENEX), financed the low-grade copper project that Daniel Cowen Jackling had started three years earlier at Bingham Canyon (Utah, US). With GUGGENEX’s investment, the exploitation of copper entered into the open-pit mining era. Nine years later, the Guggenheims applied the industrial experience acquired in Bingham Canyon in the opening of the Chuquicamata Mine (northern Chile). In both cases, all the crucial decisions about the mining were made in Manhattan, New York, while the local ter- ritories faced these projects’ outcomes. From a geohistorical standpoint, and through the analysis of several archives, in this paper, we explore how the extractive territories associated with these mines were remotely produced, transformed, and redefined; becoming “teleconnected miningscapes”. We aimed to visualize how the cross-sector partnership between large economic groups—GUGGENEX—and scientific personalities was essential in the emergence of open-pit copper mining. We argue that the miningscapes produced in Bingham Canyon and Chuquicamata mines are an entanglement of scientific discourses, research (geology and metallurgy), materi- alities (capital and technology), human bodies (workers) and nature (copper porphyries, water, air, etc.) that were unevenly and remotely produced from the headquarters of GUGGENEX.