33-1 Kinematic Complexity and Syn-Kinematic Magmatism in the Santa Catalina–Rincon Metamorphic Core Complex: New Insights from Tanque Verde Wash

Session: Going with the Shear - New Insights into Lithospheric Extensional and Strike-Slip Systems (Posters)

Poster Booth No.: 237

Presenting Author:

Lindsey Frenia

Authors:

Frenia, Lindsey¹, McCraine, Will², Kapp, Paul A.³, Hughes, Amanda N.⁴, Wu, Jonny⁵, Allen, Wayne⁶, Basler, Luke⁷, Bodine, Brett⁸, Comisac, Parker⁹, Martinez, Priscilla¹⁰, Padilla, Michael¹¹, Peppiatt, Trent¹², Zuza, Andrew¹³

(1) University of Nevada, Reno, Reno, NV, USA; University of Arizona, Tucson, AZ, USA, (2) University of Arizona, Tucson, AZ, USA, (3) University of Arizona, Tucson, AZ, USA, (4) University of Arizona, Tucson, AZ, USA, (5) University of Arizona, Tucson, AZ, USA, (6) University of Arizona, Tucson, AZ, USA, (7) University of Arizona, Tucson, AZ, USA, (8) University of Arizona, Tucson, AZ, USA, (9) University of Arizona, Tucson, AZ, USA, (10) University of Arizona, Tucson, AZ, USA, (11) University of Arizona, Tucson, AZ, USA, (12) University of Arizona, Tucson, AZ, USA, (13) University of Nevada, Reno, Reno, NV, USA; Nevada Bureau of Mines and Geology, Reno, NV, USA,

Abstract:

The lower-plate infrastructure of many metamorphic core complexes (MCC) in the North American Cordillera exhibits complex structural and magmatic relationships. It remains unclear whether these complexities represent a unified process operating in the mid-crust related to Cenozoic MCC generation during regional extension or reflect polyphase tectonomagmatic events such as Late Cretaceous-Paleogene Sevier/Laramide shortening, plutonism, metamorphism, and later Cenozoic MCC exhumation. The Santa Catalina-Rincon metamorphic core complex, Arizona, records multiple pulses of magmatism and variations in shear zone orientations and kinematics. For example, it has been postulated that structurally deep, E-trending lineations reflect Laramide structures, whereas structurally shallower SW-trending lineations reflect MCC exhumation beneath a brittle detachment fault. We conducted detailed geologic mapping along a ~10-km NE-SW traverse across a prominent swing in lineation orientations in the Tanque Verde Wash / Redington Pass area between the Santa Catalina and Rincon Mountains. Mylonitic shear sense varies from top-to-SW in the southwest closest to the main MCC detachment fault to top-to-NE in the northeast toward the range interior. As a course project at the University of Arizona, our cohort of 12 students and professors measured ductile foliation and lineation fabrics using the StraboField app (n > 500 measurements), along with documenting mylonitic sense-of-shear fabrics. Our data document intensely top-to-SW sheared gneiss and synextensional mafic to felsic igneous rocks in the proximal footwall of the top-to-SW Catalina detachment fault, with a spatially abrupt (~100 m) transition northeastward to top-to-NE sheared leucocratic igneous rocks and mylonite. Top-to-SW slip along semi-ductile subdetachment faults locally rotated foliation to NE dips in an extensional duplex. Subdetachments are absent in NE Tanque Verde Wash. The systematically rotating lineation trends (counterclockwise in map view) in the Tanque Verde Wash is consistent with those in the Molino Basin shear zone ~10 km to the northwest, suggesting either the extensional exhumation of an older Laramide-aged top-NE shear zone or complex kinematics due to enhanced mid-crust mobility associated with the syn-kinematic magmatism. Brittle normal faults preferentially terminate into these existing structural anisotropies to exhume the lower plate of the Santa Catalina-Rincon MCC. Our study emphasizes the importance of renewed structural characterization of MCC shear zones to better understand the complexity of their generation.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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