37 Cordilleran Margin Evolution and Supercontinent Tectonics: From Pangea Assembly to North American Orogenesis (Posters)

This session integrates tectonics, petrology, geochronology, stratigraphy, and paleontology to illuminate how Paleo-Pacific plates drove subduction dynamics, crustal evolution, and paleogeographic reconstructions across the complex geological architecture of the American Cordilleras.

Friday, 24 April 2026
8:00 AM - 5:30 PM
LMH, 5th Floor Chapel

Contrasting Magma Evolution during Rodinia and Pangea Assembly: insights from the Igneous Western Guatemala basement

Paper number: 37-9
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The igneous and meta-igneous basement of western Guatemala provides a unique record of magmatism associated with two supercontinent cycles: Rodinia and Pangea. Understanding magma evolution in this key region helps to constrain the stages of supercontinent assembly and breakup. This study integrates new zircon U-Pb ages, zircon REE geochemistry, and new whole-rock Sm-Nd isotopic data to examine assembly-related magmatism during both cycles. The meta-igneous Malacatancito suite, composed of basic and quartz-feldspathic orthogneisses metamorphosed under amphibolite-facies conditions, records Rodinia-related magmatism between ca. 1094 and ca. 940 Ma. Zircon geochemistry shows a decrease in U and Th through time, decreasing U/Yb and Nb/Yb ratios, increasing Eu anomalies, and progressively more hydrous conditions. These trends indicate a depleted-mantle magma source with a continuous addition of subduction fluids. Granitic rocks show eNd values near CHUR, whereas basic rocks range from +5 to +9. Nd model ages are distributed in two groups, one at ca. 1.5-1.8 Ga and another at ca.1.1 Ga, which indicates two different reservoirs or a mixing between an old crust and a ca1.0 Ga mantle. The metaigneous Sacpic suite consist of intercalated basic, quartz-feldspathic, and peraluminous gneisses metamorphosed under amphibolite-facies conditions, which record Pangea-related magmatism. Three magmatic pulses are identified: (1) intermediate to felsic magmatism from ca. 283 to ca. 261 Ma, (2) bimodal magmatism from ca.235 to ca.215 Ma, and (3) peraluminous magmatism at 183-173 Ma. Zircon geochemistry shows an increase in the Th/U ratio with decreasing age, a decrease in U/Yb and Nb/Yb ratios, high Eu anomalies in Permian-Triassic samples, lower Eu anomalies in Jurassic samples, and a progressive magmas dehydration, consistent with late-stage assembly and orogenic collapse. Basic and quartz-feldspathic rocks show eNd values from zero to -5 and Nd model ages of 1.1-1.4 Ga which suggest a younger magma source or magma mixing. Comparisons between the two cycles reveal similar trends but greater compositional dispersion during the Pangea cycle, reflecting more complex magmatic processes.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3

doi: 10.1130/abs/2026CD-410848

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