DeVitre Charlotte L, Gazel Esteban, Ramalho Ricardo S, Venugopal Swetha, Steele-MacInnis Matthew, Hua Junlin, Allison Chelsea M, Moore Lowell R, Carracedo Juan Carlos, Monteleone Brian
Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14850.
School of Earth and Environmental Sciences, Cardiff University, Cardiff CF10 3AT, United Kingdom.
Proc Natl Acad Sci U S A. 2023 Aug 15;120(33):e2302093120. doi: 10.1073/pnas.2302093120. Epub 2023 Aug 7.
Constraining the volatile content of magmas is critical to our understanding of eruptive processes and their deep Earth cycling essential to planetary habitability [R. Dasgupta, M. M. Hirschmann, , 1 (2010)]. Yet, much of the work thus far on magmatic volatiles has been dedicated to understanding their cycling through subduction zones. Further, studies of intraplate mafic volcanism have disproportionately focused on Hawaii [P. E. Wieser et al., , e2020GC009364 (2021)], making assessments of the overall role of intraplate volcanoes in the global volatile cycles a challenge. Additionally, while mafic volcanoes are the most common landform on Earth and the Solar System [C. A. Wood, , 387-413 (1980)], they tend to be overlooked in favor of silicic volcanoes when it comes to their potential for explosivity. Here, we report primitive (olivine-hosted, with host Magnesium number - Mg# 78 to 88%) melt inclusion (MI) data from Fogo volcano, Cabo Verde, that suggest that oceanic intraplate silica-undersaturated explosive eruptions sample volatile-rich sources. Primitive MI (melt Mg# 70 to 71%) data suggest that these melts are oxidized (NiNiO to NiNiO+1) and very high in volatiles (up to 2 wt% CO, 2.8 wt% HO, 6,000 ppm S, 1,900 ppm F, and 1,100 ppm Cl) making Fogo a global endmember. Storage depths calculated from these high volatile contents also imply that magma storage at Fogo occurs at mantle depths (~20 to 30 km) and that these eruptions are fed from the mantle. Our results suggest that oceanic intraplate mafic eruptions are sustained from the mantle by high volatile concentrations inherited from their source and that deep CO exsolution (here up to ~800 MPa) drives their ascent and explosivity.
限制岩浆中的挥发成分对于我们理解喷发过程以及地球深部循环（这对行星宜居性至关重要）至关重要[R. 达斯古普塔，M. M. 赫希曼， ，1 (2010)]。然而，迄今为止，关于岩浆挥发物的许多研究都致力于理解它们在俯冲带中的循环。此外，对板内镁铁质火山作用的研究过多地集中在夏威夷[P. E. 维泽等人， ，e2020GC009364 (2021)]，这使得评估板内火山在全球挥发物循环中的整体作用成为一项挑战。此外，虽然镁铁质火山是地球和太阳系中最常见的地貌[C. A. 伍德， ，387 - 413 (1980)]，但在讨论其爆发潜力时，它们往往被忽视，而更倾向于硅质火山。在此，我们报告了佛得角福戈火山原始（以橄榄石为主，主镁指数 - Mg# 为78%至88%）熔体包裹体（MI）数据，这些数据表明大洋板内硅不饱和爆炸性喷发采样自富含挥发物的源区。原始MI（熔体Mg#为70%至71%）数据表明这些熔体被氧化（NiNiO至NiNiO + 1）且挥发物含量极高（高达2 wt% CO、[此处原文似乎有误，推测可能是2 wt% H₂O]2.8 wt% H₂O、6000 ppm S、1900 ppm F和1100 ppm Cl），使福戈成为全球的一个端元。根据这些高挥发物含量计算出的储存深度还意味着福戈的岩浆储存在地幔深度（约20至30千米），且这些喷发由地幔供给。我们的结果表明，大洋板内镁铁质喷发由其源区继承的高挥发物浓度在地幔中维持，并且深部CO₂出溶（此处高达约800 MPa）驱动其上升和爆发性。
