Plutonic processes in transitional oceanic plateau crust: structure, age and emplacement of the South Rallier du Baty laccolith, Kerguelen Islands

Léandre Ponthus, Michel de Saint Blanquat*, Damien Guillaume, Marc Le Romancer, Norman Pearson, Suzanne O'Reilly, Michel Grégoire

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


The syenitic rocks of South Rallier du Baty Intrusive Complex (SRBIC) represent intrusions into the oceanic plateau basalts of the south-western Kerguelen Islands. The SRBIC was previously interpreted as a typical ring complex due to magma emplacement with cauldron subsidence. Our new structural and geochronological data reveal that it is a laccolith built between 11.6 and 7.9 Ma by successive injections of magma sheets around the crust–mantle boundary, with an average injection rate between 0.8 and 1.4 × 10−4 km3/year. These results establish strong similarities between the SRBIC, the only recorded example of a felsic laccolith in an oceanic intraplate setting, and many continental plutons emplaced in various geodynamic setting. The SRBIC thus has the characteristics of a continental plutonic complex emplaced in an oceanic plateau crust. We postulate the critical parameter relevant to causing such similarities and plutonic magmatism is crustal thickness.

Original languageEnglish
Pages (from-to)408-414
Number of pages7
JournalTerra Nova
Issue number6
Publication statusPublished - Dec 2020


  • alkaline magmatism
  • Kerguelen
  • oceanic plateau
  • pluton emplacement
  • syenite intrusion

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