Geology of the Northern Part of the Harcuvar Complex, West-Central Arizona Professional Paper 1752 U.S. Department of the Interior U.S. Geological Survey Geology of the Northern Part of the Harcuvar Complex, West-Central Arizona By Bruce Bryant and J.L. Wooden Professional Paper 1752 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DIRK KEMPTHORNE, Secretary U.S. Geological Survey Mark D. Myers, Director U.S. Geological Survey, Reston, Virginia: 2008 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 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Suggested citation: Bryant, Bruce, and Wooden, J.L., 2008, Geology of the Northern Part of the Harcuvar Complex, West-Central Arizona: U.S. Geological Survey Professional Paper 1752, 52 p. iii Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................1 Previous Work .......................................................................................................................................3 Present Work .........................................................................................................................................5 Geology ............................................................................................................................................................5 Rock Units ..............................................................................................................................................6 Proterozoic and Cretaceous Layered Gneiss .........................................................................6 Proterozoic Granodiorite to Granite Gneiss ............................................................................7 Proterozoic Porphyritic Granodiorite to Granite Gneiss .......................................................8 Paleozoic and Mesozoic Metasedimentary Rocks ................................................................8 Jurassic Metagabbro, Metadiorite, and Amphibolite ........................................................10 Late Cretaceous Granite of Tank Pass ...................................................................................11 Oligocene(?) and Miocene Swansea Plutonic Suite ...........................................................12 Rocks Probably Correlative with the Swansea Plutonic Suite ..........................................15 Geochronology .............................................................................................................................................15 Proterozoic Granitic Rocks ...............................................................................................................15 Jurassic Plutonic Rocks ....................................................................................................................15 Rocks Migmatized in the Cretaceous ..............................................................................................16 Swansea Plutonic Suite .....................................................................................................................19 Whole-Rock and Feldspar Pb-Isotopic Compositions ..................................................................19 Geochemistry................................................................................................................................................19 Analytical Methods.............................................................................................................................19 Proterozoic Granitic Rocks ...............................................................................................................21 Jurassic Plutonic Rocks ....................................................................................................................23 Cretaceous Plutonic Rocks ...............................................................................................................23 Swansea Plutonic Suite .....................................................................................................................23 Comparison with Poachie Crust and Possible Origin ..........................................................31 Relation Between Magmatism, Extension, and Core Complex Formation. ......................32 Structure........................................................................................................................................................32 Faults ..................................................................................................................................................32 Major Folds ..........................................................................................................................................34 Dikes ..................................................................................................................................................34 Lineation ...............................................................................................................................................37 Foliation ................................................................................................................................................37 Minor Folds ..........................................................................................................................................41 Older Foliation......................................................................................................................................42 Summary of Structural and Metamorphic Events ..................................................................................43 Acknowledgments .......................................................................................................................................44 References Cited..........................................................................................................................................44 Appendix. Location and Description of Analyzed Samples ..................................................................49 iv Figures 1. Map showing location of northern Harcuvar complex and core complexes of west-central Arizona and adjacent part of California .........................................................2 2. Geologic map of the northern Harcuvar complex showing locations of analyzed and(or) dated rocks ..................................................................................................4 3–12. Photographs of: 3. Migmatitic layered gneiss and granite in the eastern Harcuvar Mountains ..............7 4. Layered mylonite from layered gneiss in the eastern Buckskin Mountains ...............7 5. Mylonitic granodiorite gneiss from the eastern Buckskin Mountains .........................8 6. Mylonitic coarse-grained granite gneiss from the central Buckskin Mountains ......9 7. Thin layers of marble in migmatitic layered gneiss in the eastern Buckskin Mountains .......................................................................................................10 8. Mylonitic biotite hornblende gneiss derived from gabbro containing trondhjemite sills that have been deformed into “fish” .............................................11 9. Mylonitic biotite granite in the eastern Buckskin Mountains correlated with the Late Cretaceous granite of Tank Pass in the Harcuvar Mountains ..........12 10. Mylonitic biotite granodiorite from the felsic phase of the Swansea Plutonic Suite ....................................................................................................................13 11. Mylonitic porphyritic granite or monzogranite from inclusion in felsic phase of the Swansea Plutonic Suite ...........................................................................13 12. Small intrusion of granodiorite of the felsic phase of the Swansea Plutonic Suite into layered migmatitic gneiss ............................................................................14 13. U-Pb zircon concordia diagram for mylonitic granitic gneiss and mylonitic porphyritic granite and porphyritic granodiorite inclusion in felsic rocks of the Swansea Plutonic Suite ..............................................................................................18 14. U-Pb zircon concordia diagram for sample B–566 of mylonitic horblende diorite from the eastern Buckskin Mountains. MSWD, mean standard weighted deviation. ...................................................................................................................................18 15. U-Pb zircon concordia diagram for sample HA–118 from a migmatitic-looking granite layer in layered gneiss in the eastern Harcuvar Mountains ..............................18 16. U-Pb concordia diagrams for gabbro and