40 Mesozoic Magmatism, Postrift Tectonics, and Passive Margin Development of Northeastern North America (Posters)

The northeastern region experienced protracted Mesozoic (Triassic-Cretaceous) magmatism associated with continental rifting and subsequent passive margin development. We welcome contributions related to the occurrence, tectonics, or driving mechanisms of these syn- and postrift events.

Tuesday, 24 March 2026
8:00 AM - 12:00 PM
CCC, Ballroom C

Analysis of Crosscutting Mineralized Veins at the Early Cretaceous Cuttingsville Complex, Vermont

Paper number: 40-1
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The Early Cretaceous New England-Quebec igneous province (NEQ) represents a portion of the widespread postrift magmatism along the Eastern North American passive margin. The quartz syenite unit of the Cuttingsville Complex in Shrewsbury, Vermont is dated to 103 ± 0.53 Ma (LA-ICP-MS-U-Pb) making it the youngest postrift pluton in New England (Cooper Boemmels et al., 2021). The Cuttingsville Complex displays evidence of hydrothermal alteration and postrift deformation in a passive margin. This investigation examines structural data and petrographic observations of the mineralized veins at the Cuttingsville Complex to better understand the timing of vein formation and its relationship to the magmatism that occurred at the site.  

Fieldwork focused on structural data collection of mineralized veins, faults, and fractures. Representative samples were collected for laboratory analysis. The mineral composition of the veins and textural relationships were described using the petrographic microscope and the scanning electron microscope (SEM). 

The quartz syenite and porphyritic syenite units are crossed by mineralized veins that are steeply dipping with dominant E–W and NE–SW orientations. The veins primarily consist of quartz with large quantities of sulfide minerals including pyrite, sphalerite, and galena. They exhibit blocky textures with anhedral to subhedral mineral grains. Evidence for hydrothermal alteration such as feldspar sericitization and the development of biotite and chlorite along vein margins, occurs in the surrounding wall rock and host syenite. 

Field and petrographic results suggest that vein formation occurred during cooling just after the brittle–ductile transition following pluton emplacement. The veins exhibited fracture-controlled geometry and blocky textures suggesting brittle deformation provided a passage for hydrothermal fluids to deposit sulfide minerals during late-stage cooling of the complex. This work expands on previous investigations and contributes to a better understanding of hydrothermal processes and postrift deformation within the Eastern North American passive margin. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411117

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