304 Integrating Geochronology and Geochemistry to Decipher the Tectonic Evolution of Orogenic Belts (Posters)

This session focuses on deciphering magmatic, metamorphic, depositional and deformational events recorded in orogenic belts via the integration of geochemistry and geochronology. We welcome contributions from modern applications of analytical methods aimed at unraveling orogenic events worldwide, fostering interdisciplinary discussion.

Wednesday, 22 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Tectonomagmatic Implications from Metamorphosed Tuffs on Mesoproterozoic Intraplate Orogenesis in the Picuris Range, New Mexico

Paper number: 304-4
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The tectonomagmatic setting in which igneous melts evolve have been shown to impart a distinct trace element signature in crystallizing zircon. Trace element analysis of zircon may therefore be used to reconstruct the tectonomagmatic setting of host rocks that otherwise lack this context. Recent evaluation and reinterpretation of widespread Precambrian deformation across the Southwestern United States indicates that it is an expression of the Mesoproterozoic Picuris Orogeny rather than the Paleoproterozoic Mazatzal Orogeny. Progressive Laurentian assembly implies that the Picuris Orogeny was intraplate, inboard of the active convergent margin. Recent Mesoproterozoic tectonic models of Laurentian assembly and intraplate orogenesis integrate widespread pre- to synorogenic sedimentation, plutonism, metamorphism, and deformation. Here, we constrain the depositional history of the Mesoproterozoic Trampas basin using new SIMS zircon trace element compositions and U-Pb crystallization ages from rarely exposed Mesoproterozoic metavolcanic rocks and compare this basin history with the revised tectonic model for the Picuris Orogeny.

 

A significant part of the evolution of the Mesoproterozoic Trampas basin is recorded in the Pilar Formation, a thick sequence of black shale and interlayered tuffs that disconformably overlie the older continental shelf-related Hondo Group (Ortega Quartzite and Rinconada Formation). Zircon crystallization ages indicate that volcanic activity contributed tuffs to the Trampas basin from at least ~1489–1471 Ma, constraining the minimum duration of basin deposition. Metatuff zircon trace element compositions record two distinct geochemical signatures: one characterized by high U/Yb (>0.1), Nb/Yb (~0.01), and Sc/Yb (>0.1) consistent with continental arc magmatism, and another offset to low Sc/Yb (<0.06) characteristic of ocean island sources with contributions of enriched mantle and/or plume-influenced sources. We infer that continental arc tuffs were derived from a distal segment of the Laurentian margin that was experiencing subduction. The samples with enriched mantle affinities suggest distal plume-influenced volcanism, though the source location cannot be constrained. A single ~1472 Ma metatuff records an intermediate trace element signature possibly indicative of a mixed or transitional tectonic setting. Metatuff compositions and ages are broadly consistent with the recently revised tectonic framework for the intraplate Picuris Orogeny in which the Picuris segment of the Laurentian margin transitioned from a predominantly strike-slip to an obliquely convergent geometry, initiating Trampas basin closure and inversion after ~1470 Ma.

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

doi: 10.1130/abs/2025AM-414320

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