29-31 Textural Insights into the 200-million-year-old Magmatic System Beneath the Central Atlantic Magmatic Province.

Session: Undergraduate Research, Part II (Posters)

Presenting Author:

Authors:

Abstract:

The Central Atlantic Magmatic Province (CAMP) formed as a series of lava fields, sill complexes and dike swarms during the breakup of Pangea (~201 Ma). It is one of the world’s largest igneous provinces with individual dikes reaching lengths of 800 km and widths between 200 – 500 m. Much is still debated about the development of the province and its intrusions. The dikes are mafic in composition and have been described variously as porphyritic, glomerophyric and hypocrystalline (Macêdo Filho et al., 2019). Textural analysis of these Brazilian samples was used to suggest crystallization occurred in static magma chambers at depth. This study focuses on the Carolina group dikes to provide textural insights into what the magmatic plumbing system under the Southeastern U.S. may have looked like during the development of CAMP. 

Quantitative textural analysis through the calculation of crystal size distributions were applied to three textural endmembers: olivine basalt (≤1 mm), olivine micro-gabbro (1-3 mm), and olivine gabbro (≥ 3mm). All samples display a range of plagioclase crystal sizes, stellate plagioclase structures as well as disequilibrium textures with embayed olivine crystals. Crystal size distribution analyses can provide insights into how the preserved rock textures developed from primary accumulation to textural coarsening. All samples show overprinting effects of textural coarsening, with significant kinks at the larger crystal sizes. When the larger plagioclase crystals are excluded from the CSD plots, the kinks, no longer appear, indicating that their cause is mixed crystal populations. This indicates that the larger plagioclase crystals and stellate structures in all samples represent crystals sourced from deeper within a complex magmatic system. This provides evidence for a complex transcrustal magmatic system feeding the Carolina group dikes. 

Reference: 

Macêdo Filho, A.A., Archanjo C.J. Hollanda, M.H.B.M., and Negri,F A., 2019, Mineral chemistry and crystal size distributions of mafic dikes and sills on the eastern border of the Parnaíba Basin, NE Brazil: Journal of Volcanology and Geothermal Research, v. 377, p. 69-70, https://doi.org/10.1016/j.jvolgeores.2019.03.021

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

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