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Phil Ryder Senior Geologist Resolution Copper Mining, LLC September, 2006

Geologic Evolution of southeast Arizona including the Pioneer Mining District and Resolution, Pinal County. Phil Ryder Senior Geologist Resolution Copper Mining, LLC September, 2006. Geologic Setting.

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Phil Ryder Senior Geologist Resolution Copper Mining, LLC September, 2006

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  1. Geologic Evolution of southeast Arizona including the Pioneer Mining District and Resolution, Pinal County Phil Ryder Senior Geologist Resolution Copper Mining, LLC September, 2006

  2. Geologic Setting • eastern margin of the Basin and Range physiographic province, characterized by ~N60E to N80E oriented extension on N10W to N30W trending normal and listric faults with variable right-lateral strike-slip component. • Western edge of the Transition Zone province, characterized by exhumed ancient basement rocks, pre-B&R folds, basement lineaments, and thrust, reverse, and strike-slip faults.

  3. Geologic Evolution:Proterozoic ? ~1800 Ma Prescott-Jerome Arc • NW oceanic slab subducting to the SE ? • Development of the Prescott-Jerome Arc Modified from Anderson, 1985

  4. Geologic Evolution:Proterozoic ? ~1740 Ma Prescott-Jerome Arc • Subduction reverses, SE oceanic slab begins NW subduction beneath the Archean craton ? Modified from Anderson, 1985

  5. Geologic Evolution:Proterozoic 1740 Ma 1730 Ma Antler ~1740-1720 Ma Bagdad Prescott-Jerome 1720 Ma • NW subduction zone migrates SE, back-arc plutonism as Antler, Bagdad, and Prescott-Jerome belts evolve Modified from Anderson, 1985

  6. Geologic Evolution:Proterozoic 1740 Ma 1730 Ma Antler ~1700 Ma Bagdad Prescott-Jerome Central Volcanic Arc 1720 Ma • Development of fore arc Central Volcanic Arc and Pinal Basin Pinal Basin • Subduction and related accretion complexes continues migrating SE 1720 Ma Modified from Anderson, 1985

  7. Geologic Evolution:Proterozoic Antler ~1650 Ma Bagdad Prescott-Jerome Central Volcanic Arc • Mazatzal Orogeny, NW-SE compression, NE-trending fold axes and fabric Mazatzal Uplift Pinal Basin • Subduction zone migrates SE (suturing?) Modified from Anderson, 1985

  8. Geologic Evolution:Proterozoic ~1650—1100 Ma • Stable, regional deposition of Pioneer Shale, Dripping Spring Quartzite, Mescal Limestone, and Troy Quartzite, with discontinuous thin basalt flows

  9. Geologic Evolution:Proterozoic ~1100 Ma • Widespread (though volumetrically insignificant) emplacement of rift-derived (?) diabase dikes and sills “inflates” section

  10. Geologic Evolution:Proterozoic Summary ~1800—1650 Ma • Development (and recurrent reactivation?) of strong NW-trending compressional, strike-slip, and tensional basement fabric • Development (and recurrent reactivation?) of through-going NE-trending basement structural lineaments

  11. Modified from Hale, 1976 Geologic Evolution:Laramide ~75—50 Ma Two “phases,” or “styles,” of Laramide deformation identified in southeastern Arizona Phase 1: • NE-vergent • (recumbent) folding • thrust and reverse faulting • localized fault-block uplift

  12. Geologic Evolution:Laramide ~75—50 Ma • Thrusting compartmentalized into 2 discrete lobes in southern AZ • Separated by right-lateral “tear structures” • NE-trending tension fractures between “tear structures” Modified from Hale, 1976 • NW-trending reverse and thrust faults • Probable reactivation of preexisting fabric

  13. Geologic Evolution:Laramide ~75—50 Ma Similar “tear structures” (accommodation zones) exist in other thrust belts, e.g. Appalachian and Ouchita structural provinces (Proterozoic through Paleozoic), USA. Modified from Krantz, 1985

  14. Geologic Evolution:Laramide ~75—50 Ma Modified from Hale, 1976 Two “phases,” or “styles,” of Laramide deformation identified in southeastern Arizona Phase 2: • NW-oriented transpression • Accommodated by NW-oriented right-lateral strike-slip • NE-trending reverse and thrust faults • Reactivation of preexisting, well-established basement anisotropy

  15. Geologic Evolution:Laramide ~67—61 Ma Local Plutonism: • Emplacement at ~67—61 Ma of east-northeast-oriented granitic plutons and quartz monzonite porphyry dikes, i.e. Schultze Granite and localized rhyodacite and rhyolatite porphyry dikes. • RCM porphyry dikes bracketed between 62 Ma (from K-Ar dates on dikes of similar composition from the Christmas District, 40 km south of PMD, and 61.2 Ma (from K-Ar dates on various intrusive phases of the Schultze Granite 15 km east of PMD, and 67-61 Ma Schultze Granite (Stavast, 2006).

  16. Geologic Evolution:Laramide ~67—61 Ma Local Plutonism: • “Cu-bearing porphyry dikes of the Superior East and Resolution may have come from the Schultze or another intrusion of similar age…[this intrusive complex] could account for the copper in those two deposits (Stavast, 2006, p. 160-161).” • Porphyry dikes are hosted in Precambrian through Cretaceous rocks within the district.

  17. Modified from Spencer and Reynolds, 1987 Geologic Evolution:Basin & Range ~28—0 Ma • crustal extension began ~28 Ma as regional brittle-ductile low-angle detachment faulting and metamorphic core complex development (modified from Spencer and Reynolds, 1987), though thickening of Tw to the east suggests earlier onset of (brittle listric) extension locally.

  18. Geologic Evolution:Basin & Range ~28—0 Ma • Extension presently accomplished through regional brittle large-scale block, listric, and normal-oblique faulting locally as characteristic throughout active portions of the Basin and Range (Spencer and Reynolds, 1987). • Basin and Range structures likely sole into low-angle structures at depth. Modified from Marsh and Hart, 2003

  19. Structural Proposals:Fabric • Present trend of faults, structural basins, mineralization, and brecciated zones are consistent with well-established basement weaknesses, lineaments, and structures developed and reactivated from at least 1800 Ma through Basin & Range.

  20. Structural Proposals:Fabric • Regionally, these trends are well expressed. Consider the geology between Resolution and Ray, AZ.

  21. Modified from Gant and Wilkins, 2004

  22. Structural Proposals:The Kvs Graben • Locally, trend of faults, structural basins, mineralization, and brecciated zones are consistent with these same basement weaknesses, lineaments, and structures.

  23. Structural Proposals:The Kvs Graben • Furthermore, observed and interpreted orientations and dextral/sinistral strike-slip fault displacements are consistent with regional NE-oriented and localized NW-oriented Laramide transpression.

  24. Structural Proposals:The Kvs Graben • Structural problem: attenuation to absence of the Paleozoic section beneath the Tertiary cover, within the “Kvs graben.” Modified from Paul and Manske, 2002

  25. SW NE Structural Proposals:The Kvs Graben • Ca. 80 Ma • Deposition within a stable marine basin, with brief periods of transgression/ regression

  26. Structural Proposals:The Kvs Graben SW NE • Ca. 70 Ma • Onset of Laramide Orogeny, with Phase 1 NE-SW-oriented compression, and development of reverse and thrust faults, and folding

  27. Structural Proposals:The Kvs Graben SW NE • Ca. 65 Ma • In “Phase 1” Laramide deformation, upthrown fault blocks are “bevelled off,” removing Paleozoic section from discrete blocks.

  28. Structural Proposals:The Kvs Graben • Ca. 62—60 Ma • “Phase 2” is NW-SE localized transpression coeval with “Phase 1” NE-oriented Laramide compression, whereby crustal shortening is accomplished through NW-oriented right-lateral strike-slip. Kvs basin • Previously upthrown fault blocks are downdropped as transpressional rhombochasms are developed.

  29. 65-62 Ma Structural Proposals:The Kvs Graben • Ca. 62 Ma • Localized NW-SE transpression in the Laramide NE-SW compressional regime • Shortening accomplished through NW-oriented right-lateral strike-slip. • Previously upthrown fault blocks are downdropped as transpressional rhombochasms are developed. SW NE

  30. Structural Proposals:The Kvs Graben SW NE • Ca. 62 Ma • Emplacement and evolution of granitic plutons and associated porphyry dikes. • Local volcanic activity related to plutonism.

  31. Structural Proposals:The Kvs Graben SW NE • Ca. 60 Ma • Localized rhombochasm becomes locus of volcaniclastic sedimentation and volcanic activity

  32. Structural Proposals:The Kvs Graben SW NE • Ca. 38 Ma • “White Tail Basin” begins ~38 Ma as incipient (or proto?) Basin and Range extension commences. • Transpressional extension evolves to listric-style extension east of the White Tail Basin.

  33. Structural Proposals:The Kvs Graben SW NE • Ca. 22 Ma • “White Tail Basin” deepens to the east. • Older structures rotate as bounding fault blocks rotate.

  34. Structural Proposals:The Kvs Graben • Ca. 19 Ma • Eruption and emplacement of the Apache Leap Tuff. • Activity on Devils Canyon Fault diminishes as Concentrator Fault becomes active. • Oblique extension continues. SW NE

  35. Structural Proposals:The Kvs Graben SW NE • Ca. 0 Ma • Development of present-day topography through erosion and diminishing fault offset.

  36. Transpression Zones:http://www.dur.ac.uk/grl/Downloads/JSG_2004_v26_08_1531_Jones.pdf

  37. Oblique Transpression Zones:The Kvs Graben?

  38. Some of R.R.Jones, et. al. ConclusionsInclined Transpression in the Kvs Graben? R.R.Jones, et. al. (2004)

  39. Oblique Transpression Zones:Inclined Transpression in the Kvs Graben? Highlighted member of the R.R.Jones, et. al. (2004) diagram closely resembles our evolving understanding of the structure within the Resolution graben as data from core logging and field mapping are entered into our evolving model.

  40. From Jones, et. al., 2004 Ryder, 2007 Oblique Transpression Zones:Inclined Transpression in the Kvs Graben? Laramide “transpression fault blocks” (including internal faults) probably reactivated during Basin & Range extension along “master” listric faults…

  41. Some of R.R.Jones, et. al. ConclusionsRelevancy to the Kvs Graben? • First, plate tectonics is not a plane strain process and cannot be approximated by simple shear. • Second, transpression models recognize the vital importance of the upper free surface of the earth in controlling crustal scale deformation. • Third, deformation in the crust IS NOT homogeneous, and is strongly influenced by pre-existing anisotropy. • Fourth, though simplistic, transpression models produce realistic, testable predictions about the complicated nature of progressive three-dimensional strain that can advance our understanding of complex zones of deformation in the earth’s crust.

  42. Summary 1) Tectonic evolution of the region including the Pioneer Mining District dates back to at least 1740 Ma. 2) Lower Proterozoic subduction and accretion off of the western margin of the early craton established northeast-oriented basement anisotropies that were reactivated by later compressive and extensional events.

  43. Summary 3) The Laramide occurred in two coeval “phases,” as compartmentalized northeast folding and thrusting, and as transpressional northwest- oriented shortening and rhombochasm development accommodated by strike-slip faulting. 4) NE-oriented Laramide folding and thrusting progressed regionally as discrete, northeast- vergent folding and thrust lobes, separated by northeast-trending tear zones, controlled by preexisting and well-established anisotropies in the Proterozoic basement.

  44. Summary 5) NE-oriented compression uplifted discrete fault blocks, resulting in partial to total erosion of the Paleozoic section. 6) Transpressional rhombochasm developmentthroughright-lateralstrike-slipreactivation of preexisting NW-oriented basement anisotropies locally down-dropped previously uplifted fault blocks denuded of their Pz cover (elsewhere, similar blocks were uplifted, e.g. Ray).

  45. Summary 7) Repeated northeast- and northwest-oriented shortening from 1740-60 Ma produced a northeast-oriented structural fabric and brecciation at depth in country rock, creating anisotropic weakness later exploited by late Laramide granitic pluton and dike emplacement. 8) Cenozoic Basin and Range extension further modified the section through northeast- southwest-oriented extension, accommodated by northwest-oriented, down-to-the-west block and listric normal faults with minor to major oblique right-lateral component.

  46. Things to ponder… Implications for the Resolution ore body? Further exploration of the district? Is Pz section truly absent from Kvs graben? New information on bedding orientations? What have we learned so far from VSP? New info as per alteration / mineralization shells?

  47. Acknowledgements Drewes, Harald, 1981, Tectonics of southern Arizona: U.S. Geological Survey Professional Paper 1144 Jones, Richard R., et. al., 2004, Inclined transpression: Journal of Structural Geology v. 26, p. 1531-1548. Krantz, R. W., 1987, Laramide structures of Arizona: in Jenney, J.P., and Reynolds, S. J., eds., Geologic evolution of Arizona: Tucson, Arizona Geological Society Digest 17. Spencer, J. A., and Reynolds, S. J., 1987, Middle Tertiary tectonics of Arizona and adjacent areas: in Geologic evolution of Arizona, Arizona Geological Society Digest 17, Jenney, J. P., and Reynolds, S. J., eds., 1989. Manske, S. L., and Paul, A. H., 2002, Geology of a major new porphyry copper center in the Superior (Pioneer) district, Arizona: Economic Geology, v. 97, p. 197-220. Figures credited to Hale, 1976, appear on the cover of AZ Geological Society Digest, Volume X, Tucson, Arizona, March 1976. Special thanks to Gustavo Zulliger, Carl Hehnke, Geoff Ballantyne, Marty Houhoulis, Adam Schwarz, Alan Seymour, Bill Hart, and all other RCM staff and contractors whose ideas, edits, graphics, and especially time, were gracious and very much appreciated. Prepared for submission to RCM, LLC, SEP2006, by Phil Ryder, RCM Senior Geologist.

  48. Acknowledgements Drewes, Harald, 1981, Tectonics of southern Arizona: U.S. Geological Survey Professional Paper 1144 Jones, Richard R., et. al., 2004, Inclined transpression: Journal of Structural Geology v. 26, p. 1531-1548. Krantz, R. W., 1987, Laramide structures of Arizona: in Jenney, J.P., and Reynolds, S. J., eds., Geologic evolution of Arizona: Tucson, Arizona Geological Society Digest 17. Spencer, J. A., and Reynolds, S. J., 1987, Middle Tertiary tectonics of Arizona and adjacent areas: in Geologic evolution of Arizona, Arizona Geological Society Digest 17, Jenney, J. P., and Reynolds, S. J., eds., 1989. Manske, S. L., and Paul, A. H., 2002, Geology of a major new porphyry copper center in the Superior (Pioneer) district, Arizona: Economic Geology, v. 97, p. 197-220. Figures credited to Hale, 1976, appear on the cover of AZ Geological Society Digest, Volume X, Tucson, Arizona, March 1976. Special thanks to Gustavo Zulliger, Geoff Ballantyne, Marty Houhoulis, Adam Schwarz, and all other RCM staff and contractors whose ideas, edits, graphics, and especially time, were gracious and very much appreciated. Prepared for submission to RCM, LLC, SEP2006, by Phil Ryder, RCM Senior Geologist.

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