The Central Atlantic Magmatic Province (CAMP) is the most aerially extensive magmatic event in Earth’s history, but many questions remain about its origin, volume, and distribution. Despite many observations of CAMP magmatism near Earth’s surface, few constraints exist on CAMP intrusions at depth. Here we present detailed constraints on crustal and upper mantle structure from wide-angle seismic data across the Triassic South Georgia Rift that formed shortly before CAMP. Lower crustal magmatism is concentrated where synrift sedimentary fill is thickest and the crust is thinnest, suggesting that lithospheric thinning influenced the locus and volume of magmatism. The limited distribution of lower crustal intrusions implies modest total CAMP volumes of 85,000 to 169,000 km³ beneath the South Georgia Rift, consistent with moderately elevated mantle potential temperatures (<1500 °C). These results suggest that CAMP magmatism in the South Georgia Rift is caused by syn-rift decompression melting of a warm, enriched mantle.

中大西洋岩浆省（CAMP）是地球历史上最广泛的岩浆事件，但有关其起源，体积和分布方面仍存在许多疑问。尽管在地球表面附近观察到许多CAMP岩浆作用，但对CAMP深度侵入的约束很少。在这里，我们从CAMP之前不久形成的三叠纪南乔治亚大裂谷的广角地震数据中提出了对地壳和上地幔结构的详细约束。下地壳岩浆作用集中在同物沉积物充填最厚，地壳最薄的地方，这表明岩石圈变薄影响了岩浆作用的轨迹和体积。下地壳侵入体分布有限，意味着CAMP总量不大，为85,000至169,000 km ³在南乔治亚大裂谷以下，与地幔潜在温度（<1500°C）适度升高相一致。这些结果表明，南乔治亚大裂谷的CAMP岩浆作用是由温暖富集的地幔的同裂分离减压融化引起的。