Evidence for multiple intrusion and deformation within the Santa Catalina-Rincon-Tortolita crystalline complex, southeastern Arizona

Recent field work and accumulated Rb-Sr studies, when combined with previous U-Th-Pb and K-Ar investigations, allow a new synthesis of the crystalline terrane within the Santa Catalina-Rincon- Tortolita crystalline complex. When all the available data are integrated, it is apparent that the crystalline core is mainly a composite batholith that has been deformed by variable amounts of cataclasis. The batholith was formed by three episodes of geologically, mineralogically, geochemically, and geochronologically distinct plutons. The first episode (75 to 60 m.y. B.P.) consisted of at least two (and probably three) calc-alkalic, epidote-bearing biotite granodiorite plutons (Leatherwood suite). The Leatherwood suite is intruded by distinctive leucocratic muscovite-bearing peraluminous granitic plutons (Wilderness suite), which are 44 to 50 m.y. old. At least three Wilderness suite plutons are known, and their origin has been much debated. Leatherwood and Wilderness plutons are intruded by a third suite of four biotite quartz monzonite to granite plutons (Catalina suite) that mark the final consolidation of the batholith 29 to 25 m.y. ago. Much of the mylonitic (cataclastic) deformation of the plutonic rocks and recrystallization of the enclosing host rocks may be related to intrusion of the various plutons. At least three episodes of mylonitization (cataclasis) may be delineated by observing relations between mylonitic and nonmylonitic crosscutting plutons. The southern part of the Leatherwood pluton bears a moderate to strong mylonitic foliation that is cut by undeformed leucogranites and pegmatite phases of the Wilderness pluton. Elsewhere in the Santa Catalina-Rincon-Tortolita crystalline core, Wilderness suite plutons contain penetrative mylonitic foliation. Foliated Wilderness suite plutons are intruded by an undeformed portion of a Catalina suite pluton. In the Tortolita Mountains, however, intrusions of the Catalina suite themselves contain evidence for at least two events of mylonitic deformation. The most significant of these events is clearly constrained to the Catalina intrusive episode because it formed during or after the emplacement of Tortolita quartz monzonite (about 27 m.y. B.P.) but before the intrusion of postfoliation dikes (about 24 m.y. B.P.). All three episodes of mylonitization contain the distinctive and much discussed east-northeast-trending lineations. All events of mylonitization are constrained to a 50-m.y. interval of time from 70 to 20 m.y. ago. Although continuous mylonitization from 70 to 20 m.y. ago cannot be unequivocally disproved, the strong association of mylonitization with the three plutonic episodes suggests that deformation in the Santa Catalina-Rincon-Tortolita crystalline core, like intrusion, was episodic.