Persistent Link:
http://hdl.handle.net/10150/187531
Title:
GEOLOGY AND GEOCHRONOLOGY OF THE SOUTH MOUNTAINS, CENTRAL ARIZONA
Author:
Reynolds, Stephen James
Issue Date:
1982
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The South Mountains are composed of two fundamentally different terranes. The western half of the range consists of Precambrian metamorphic and granitic rocks, whereas the eastern half is dominated by a composite middle Tertiary pluton. North-northwest-trending, middle Tertiary dikes have extensively intruded both terranes. A major episode of middle Proterozoic metamorphism and deformation produced a steep crystalloblastic foliation that generally strikes northeast. Middle Tertiary plutonism was accompanied by intense mylonitization that affected Precambrian and middle Tertiary rocks alike. Discrete phases of mylonitization were associated with each intrusive pulse between 28 and 25 m.y.B.P. Mylonitization generally produced a lowangle foliation and east-northeast-trending lineation. The attitude of mylonitic foliation defines a broad, east-northeast-trending anticline that controls the topographic axis of the range. Structurally low rocks in the core of the anticline are nonmylonitic, but intensity of mylonitic fabric increases progressively toward higher structural levels. Mylonitic Tertiary plutonic rocks are exposed as a gently dipping carapace overlying their less deformed equivalents. Mylonitic fabric cuts through the Precambrian terrane as a broad, west-dipping zone. Rocks above and below this mylonitic zone are lithologically identical and mostly retain their Precambrian structure. Fabrics in all rock types indicate that mylonitization resulted from extension parallel to east-northeast-trending lineation and flattening perpendicular to subhorizontal foliation. Mylonitization occurred under conditions of elevated temperature but relatively low confining pressure. Gold-bearing quartz veins occur in tension fractures that are late- to post-kinematic with respect to mylonitic deformation. Mylonitization was succeeded by more brittle deformation that produced chloritic breccia and microbreccia in the footwall of a major detachment fault that dips gently to the east. The detachment fault and underlying breccia were formed by normal faulting and brittle extension in an east-northeast direction. Rocks above and immediately below the detachment fault were antithetically rotated during faulting. Mylonitization, detachment faulting, and formation of the main east-northeast-trending anticline are all manifestations of eastnortheast-directed, middle Tertiary extension. Evidence for a possible continuum between mylonitization and detachment faulting has important implications regarding the evolution of Cordilleran metamorphic core complexes.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Geology -- Arizona -- South Mountains.; Geological time.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Coney, Peter J.
Committee Chair:
Coney, Peter J.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleGEOLOGY AND GEOCHRONOLOGY OF THE SOUTH MOUNTAINS, CENTRAL ARIZONAen_US
dc.creatorReynolds, Stephen Jamesen_US
dc.contributor.authorReynolds, Stephen Jamesen_US
dc.date.issued1982en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe South Mountains are composed of two fundamentally different terranes. The western half of the range consists of Precambrian metamorphic and granitic rocks, whereas the eastern half is dominated by a composite middle Tertiary pluton. North-northwest-trending, middle Tertiary dikes have extensively intruded both terranes. A major episode of middle Proterozoic metamorphism and deformation produced a steep crystalloblastic foliation that generally strikes northeast. Middle Tertiary plutonism was accompanied by intense mylonitization that affected Precambrian and middle Tertiary rocks alike. Discrete phases of mylonitization were associated with each intrusive pulse between 28 and 25 m.y.B.P. Mylonitization generally produced a lowangle foliation and east-northeast-trending lineation. The attitude of mylonitic foliation defines a broad, east-northeast-trending anticline that controls the topographic axis of the range. Structurally low rocks in the core of the anticline are nonmylonitic, but intensity of mylonitic fabric increases progressively toward higher structural levels. Mylonitic Tertiary plutonic rocks are exposed as a gently dipping carapace overlying their less deformed equivalents. Mylonitic fabric cuts through the Precambrian terrane as a broad, west-dipping zone. Rocks above and below this mylonitic zone are lithologically identical and mostly retain their Precambrian structure. Fabrics in all rock types indicate that mylonitization resulted from extension parallel to east-northeast-trending lineation and flattening perpendicular to subhorizontal foliation. Mylonitization occurred under conditions of elevated temperature but relatively low confining pressure. Gold-bearing quartz veins occur in tension fractures that are late- to post-kinematic with respect to mylonitic deformation. Mylonitization was succeeded by more brittle deformation that produced chloritic breccia and microbreccia in the footwall of a major detachment fault that dips gently to the east. The detachment fault and underlying breccia were formed by normal faulting and brittle extension in an east-northeast direction. Rocks above and immediately below the detachment fault were antithetically rotated during faulting. Mylonitization, detachment faulting, and formation of the main east-northeast-trending anticline are all manifestations of eastnortheast-directed, middle Tertiary extension. Evidence for a possible continuum between mylonitization and detachment faulting has important implications regarding the evolution of Cordilleran metamorphic core complexes.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectGeology -- Arizona -- South Mountains.en_US
dc.subjectGeological time.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorConey, Peter J.en_US
dc.contributor.chairConey, Peter J.en_US
dc.contributor.committeememberDavis, George H.en_US
dc.contributor.committeememberDamon, Paul E.en_US
dc.contributor.committeememberGuilbert, John M.en_US
dc.contributor.committeememberPeirce, H. Wesleyen_US
dc.contributor.committeememberDickinson, William R.en_US
dc.identifier.proquest8217506en_US
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