29-30 Mineral Chemical 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) is distinct from other large igneous provinces due to its large aerial extent: eastern North America, northeastern South America, northwestern Africa, and into western Europe. Collectively, the CAMP dikes extend over 10,000 km with an estimated magmatic volume of 3 million km³, developing in association with the breakup of Pangea, with peak activity at ~201 Ma. The province is divided into six geochemical groups, likely associated with variations due to local assimilation and contamination. The Carolina Group, on which this project focuses, in the southeastern U.S., is MgO-rich and TiO2-poor (Marzoli et al., 2017). Samples from the Piedmont region of western South Carolina were studied for mineral chemical insights into the magmatic plumbing system.

Electron probe microanalysis was used to determine the compositions of plagioclase, clinopyroxene, olivine, and Cr-spinel, as well as to produce element maps of samples from olivine basalt to olivine gabbro. Plagioclase compositions range from An₇₃ (core) to An₄₃ (rim), with the rims always having lower An-contents. All the larger plagioclase crystals display oscillatory zoning. Clinopyroxene is augite in composition, and interstitial crystals may be zoned. Olivine compositions range from Fo₉₀ to Fo₆₆, indicating effects of diffusive equilibration and magmatic recharge. Cr-spinel (Cr# 35 - 38) occurs in association with olivine. Together, these data indicate that the larger plagioclase and clinopyroxene crystals, as well as the olivine and Cr-spinel crystals, were sourced from deeper within a complex magmatic system. Olivine and Cr-spinel may have been sourced from close to the mantle, while the plagioclase and clinopyroxene crystal cores likely represent mid-crustal depths.

Reference:

Marzoli, A., Callegaro, S., Dal Corso, J., Davies, J.H.F.L, Chiaradia, M., Youbi, N., Bertrand, H., Reisberg, L., Merle, R., and Jourdan, F, 2017, The Central Atlantic Magmatic Province (CAMP): A Review in Tanner, L.H. (ed), The Late Triassic World: Springer Topics in Geobiology v. 26, p. 91–125, https://doi.org/10.1007/978-3-319-68009-5_4

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

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