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Crystals and melt inclusions as emissaries of magmatic plumbing systems

Juliette Pin 1,2,3, Lydéric France2,4, Gilles Chazot1, Etienne Deloule2, Yafet Gabrewold Birhane2, Mohamed Ahmed Daoud5, Bernard Le Gall1

  • Affiliations:  1 Laboratoire Geo-Ocean (LGO), Institut Universitaire Européen de la Mer (IUEM), Université de Bretagne Occidentale (UBO), Place Copernic, 29280 Plouzané, France; 2 Université de Lorraine, CNRS, CRPG, F-54000 Nancy, France; 3 Now at: University of Nevada, Reno, USA; 4 Institut Universitaire de France (IUF), France; 5 Centre d'Etudes et de Recherches de Djibouti (CERD), Djibouti 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 234

  • Programme No: 1.1.20

  • Theme 1 > Session 1

Abstract

The active Asal rift in the Afar region is an ideal site to study volcanism and magmatism associated with continental rifting. Our study examines the volatile element composition of magmas in the Asal rift segment, focusing on samples collected from various volcanic sub-segments within the active area, including a subset documenting the 1978 Ardoukoba eruption. Over 400 analyses of melt inclusions from plagioclase and olivine crystals reveal insights into the magma pre-eruptive volatile content. Using SIMS analyses, we quantified volatile components (H2O, CO2, Cl, S) to reconstruct the initial magmatic volatile content at reservoir depth. Combined with petrographic studies, field observations, major, trace and hydrogen isotopic composition, and new dating, our findings offer a comprehensive view of magmatic processes in the Asal rift, illustrating their spatial and temporal evolution. We assessed the contributions of primary (source composition, melting, differentiation) and secondary (degassing, contamination) processes to volatile composition variations. Our findings reveal that the Asal plumbing system extension has varied across time, both vertically and horizontally. We highlight cycles of magma differentiation over the range 1250-1050°C and degassing, accompanied by assimilation of hydrothermally altered rocks. In summary, this high-resolution dataset enhances our understanding of magma reservoir dynamics, providing new insights into the evolution, differentiation, and degassing of magmas in continental rift systems.