Center for Mineral Resources: U.S. Geological Survey-University of Arizona, Department of Geosciences Porphyry Copper Deposit Life Cycles Field Conference, southeastern Arizona, May 21-22, 2002

Barton, Mark D.; Brown, James; Haxel, Gordon B.; Hayes, Timothy S.; Jensen, Eric; Johnson, David; Kamilli, Robert; Long, Keith R.; Maher, David J.; Seedorff, Eric

doi:10.3133/sir20055020

Cited by 9 publications

(1 citation statement)

References 10 publications

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“…The Galiuro Mountains are located within the Basin and Range province of southeastern Arizona. Even though the San Pedro Valley and Tortilla Mountains, located immediately west of the Galiuro Mountains, have been highly extended and tilted by middle to late Cenozoic extension (Barton et al, ; Dickinson, ; Favorito & Seedorff, ; Maher, ; Nickerson et al, ), the Galiuro Mountains are cut by only a few normal faults and are only mildly extended (Creasey et al, ; Dickinson, ). Nearby towns include Mammoth and Dudleyville, and nearby Laramide porphyry copper deposits include Copper Creek, San Manuel‐Kalamazoo, Chilito, and Christmas (Leveille & Stegen, ), each of which is no farther than 15 km from boundaries of the study area.…”

Section: Geologic Settingmentioning

confidence: 99%

Discovery of Major Basement‐Cored Uplifts in the Northern Galiuro Mountains, Southeastern Arizona: Implications for Regional Laramide Deformation Style and Structural Evolution

Favorito

Seedorff

2018

Tectonics

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The Laramide orogeny is poorly understood in southeastern Arizona, largely because of complex structural overprinting by mid-Cenozoic extension that occurred over large areas. This study integrates new geological mapping with previous work, combined with structural reconstructions and forward modeling, to determine the primary structural style, timing, evolution, and kinematics of Laramide shortening in the northern Galiuro Mountains. Cenozoic normal faulting in the study area is minor and has only resulted in up to 13°of eastward tilting, as indicated by the gentle dips of synextensional strata. Detailed mapping has revealed newly identified reverse fault systems measuring at least 50 km in combined strike length. Each major fault strikes north-northwest, dips moderately to the west, places older rocks on younger, and has related fault-propagation folds. Once restored to their original orientation, reverse faults range in dip from 38°to 47°. These moderate dips of faults combined with related folds, the significant degree of basement involvement, and cover sequence lacking obvious penetrative deformation indicate that these faults are thick-skinned, basement-cored uplifts. Forward modeling and Cenozoic erosion surfaces suggest regionally extensive Laramide-age tilting to the west-southwest and gentle folding, possibly caused by a regional-scale reverse fault underlying the study area. These results are consistent with the interpretation that Laramide shortening in southeastern Arizona was primarily characterized by thick-skinned tectonics. Kinematic indicators, folded basement rocks, north-northwest strikes of reverse faults, and lack of evidence for basin inversion suggest that preexisting basement faults and fabrics had little or no effect on the subsequent structural evolution.Plain Language Summary The Late Cretaceous to early Eocene Laramide orogeny was a period of crustal shortening in the North American Cordillera that involved two different styles of reverse faulting. One style involves low-angle thrusts that typically slip parallel to bedding planes in layered rocks, whereas the other style involves faults that cut across bedding at moderate angles and continue downward through underlying crystalline basement rock. In southeastern Arizona, the style of Laramide shortening is debated and not well understood, in part because most of the region has undergone subsequent Cenozoic extension that has significantly rotated, dismembered, and buried most faults formed during Laramide crustal shortening. This study examines a newly discovered set of Laramide reverse faults that extend for more than 50 km along strike and that have only been affected by minor extension. Results from field mapping and structural modeling indicate that these faults are basement-involved, moderate-angle reverse faults. Because the upper crustal architecture across the region is largely consistent, the region as a whole may be characterized by moderate-angle reverse faults. Thus, nearby Laramide faults that have been previously interpr...

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Section: Geologic Settingmentioning

confidence: 99%

Discovery of Major Basement‐Cored Uplifts in the Northern Galiuro Mountains, Southeastern Arizona: Implications for Regional Laramide Deformation Style and Structural Evolution

Favorito

Seedorff

2018

Tectonics

Self Cite

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Coarse muscovite veins and alteration in porphyry systems

Runyon

Seedorff

Barton

et al. 2019

Ore Geology Reviews

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Crustal shortening and porphyry copper mineralization in the Laramide arc and superimposed extension: Introduction and themes

Seedorff

Richardson

Favorito

et al. 2019

Geologic Excursions in Southwestern North America

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The Laramide continental arc formed in southwestern North America at about the same time the Sierra Nevadan arc was shutting down, and the Laramide arc was active concurrent with the progress of the Laramide orogeny, from ca. 80 Ma to ca. 45 Ma. East-central Arizona offers an excellent opportunity to explore aspects of tectonics, structural geology, magmatism, and hydrothermal systems in a segment of the Laramide arc that is exceptionally well endowed with porphyry copper deposits. The structure of this region is especially complicated, with multiple generations of normal faults commonly superimposed on originally moderate-angle reverse faults with associated fault-propagation folds. A large new porphyry copper deposit, Resolution, was discovered near Superior in the mid-1990s. The discovery started a new round of development in the mining life cycle at the Resolution deposit; in the region, it contributed to copper exploration again becoming vigorous in the last decade. In the years since discovery of Resolution, important new scientific insights have been gained, including at the regional scale. Post-ore crustal extension exposed multiple levels of Laramide and older igneous and hydrothermal systems at the surface where they can be more easily mapped and sampled, and palinspastic reconstructions of post-mineral normal faulting permit the exposures to be restored to their original positions. The porphyry-related products that are observed at higher levels include local advanced argillic alteration and Cordilleran-style veins and associated mantos, such as at the Magma mine, Resolution deposit, and Old Dominion mine in the shallowest levels of the Superior-Globe-Miami area. Most porphyry copper ore bodies were developed at intermediate depths, where porphyry intrusions exhibit sericitic and potassic alteration and carbonate rocks were converted to skarn, such as in the heart of the Miami-Inspiration, Resolution, Ray, and Christmas deposits. Plutonic rocks are exposed at deeper paleodepths, where pegmatites, quartz veins, and greisen muscovite are locally observed, especially directly beneath porphyry copper orebodies, as in the Schultze and Granite Mountain plutons. Likewise, sodic-calcic alteration may be developed on the deep flanks of porphyry systems, such as adjacent to the Tea Cup pluton. Subsequent Cenozoic extension variously buried or exhumed the hypogene portions of these hydrothermal systems, leading to the development of various supergene products, both in situ and exotic.

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Center for Mineral Resources: U.S. Geological Survey-University of Arizona, Department of Geosciences Porphyry Copper Deposit Life Cycles Field Conference, southeastern Arizona, May 21-22, 2002

Cited by 9 publications

References 10 publications

Discovery of Major Basement‐Cored Uplifts in the Northern Galiuro Mountains, Southeastern Arizona: Implications for Regional Laramide Deformation Style and Structural Evolution

Discovery of Major Basement‐Cored Uplifts in the Northern Galiuro Mountains, Southeastern Arizona: Implications for Regional Laramide Deformation Style and Structural Evolution

Coarse muscovite veins and alteration in porphyry systems

Crustal shortening and porphyry copper mineralization in the Laramide arc and superimposed extension: Introduction and themes

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