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

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.

[1]  Léandre Ponthus.  Origine, évolution et mise en place d'un pluton alcalin récent en contexte intraplaque océanique : exemple du complexe sud de Rallier du Baty, Kerguelen (T.A.A.F.) , 2018 .

[2]  J. Vervoort,et al.  Elucidating the magmatic history of the Austurhorn silicic intrusive complex (southeast Iceland) using zircon elemental and isotopic geochemistry and geochronology , 2016, Contributions to Mineralogy and Petrology.

[3]  R. Mills,et al.  The pace of plutonism , 2016 .

[4]  B. Schoene,et al.  Evaluating the construction and evolution of upper crustal magma reservoirs with coupled U/Pb zircon geochronology and thermal modeling: A case study from the Mt. Capanne pluton (Elba, Italy) , 2015 .

[5]  R. Sparks,et al.  Construction and evolution of igneous bodies: Towards an integrated perspective of crustal magmatism , 2015 .

[6]  M. Ducea,et al.  Arc magmatic tempos: Gathering the evidence , 2015 .

[7]  R. Wintsch,et al.  Primitive layered gabbros from fast-spreading lower oceanic crust , 2013, Nature.

[8]  F. Bussy,et al.  Timing of incremental pluton construction and magmatic activity in a back-arc setting revealed by ID-TIMS U/Pb and Hf isotopes on complex zircon grains , 2013 .

[9]  L. Baumgartner,et al.  Time resolved construction of a bimodal laccolith (Torres del Paine, Patagonia) , 2012 .

[10]  E. Horsman,et al.  Multiscale magmatic cyclicity, duration of pluton construction, and the paradoxical relationship between tectonism and plutonism in continental arcs , 2011 .

[11]  F. Innocenti,et al.  Rapid incremental assembly of the Monte Capanne pluton (Elba Island, Tuscany) by downward stacking of magma sheets , 2010 .

[12]  S. Burchardt,et al.  Mode of emplacement of the Slaufrudalur Pluton, Southeast Iceland inferred from three-dimensional GPS mapping and model building , 2010 .

[13]  E. Horsman,et al.  Emplacement and assembly of shallow intrusions from multiple magma pulses, Henry Mountains, Utah , 2009, Earth and Environmental Science Transactions of the Royal Society of Edinburgh.

[14]  M. Tivey,et al.  Plutonic foundation of a slow‐spreading ridge segment: Oceanic core complex at Kane Megamullion, 23°30′N, 45°20′W , 2008 .

[15]  D. Miller,et al.  Oceanic Core Complexes and Crustal Accretion at Slow-Spreading Ridges. Indications From IODP Expeditions 304-305 and Previous Ocean Drilling Results , 2006 .

[16]  J. Crisp,et al.  Long‐term volumetric eruption rates and magma budgets , 2006 .

[17]  R. Sparks,et al.  The Genesis of Intermediate and Silicic Magmas in Deep Crustal Hot Zones , 2006 .

[18]  A. Glazner,et al.  Are plutons assembled over millions of years by amalgamation from small magma chambers , 2004 .

[19]  F. Innocenti,et al.  Two-stage growth of laccoliths at Elba Island, Italy , 2002 .

[20]  S. Morgan,et al.  Internal structure and emplacement of the Papoose Flat pluton: An integrated structural, petrographic, and magnetic susceptibility study , 2001 .

[21]  A. Cruden,et al.  Granite magma formation, transport and emplacement in the Earth's crust , 2000, Nature.

[22]  D. Bideau,et al.  A long in situ section of the lower ocean crust: results of {ODP} Leg 176 drilling at the Southwest Indian Ridge , 2000 .

[23]  J. Cottin,et al.  The meta-igneous granulite xenoliths from Kerguelen Archipelago: evidence of a continent nucleation in an oceanic setting , 1998 .

[24]  Cruden Alexander.R..  On the emplacement of tabular granites , 1998, Journal of the Geological Society.

[25]  B. Weaver,et al.  Origin of Differentiated Volcanic and Plutonic Rocks from Ascension Island, South Atlantic Ocean , 1998 .

[26]  M. Cannat.  How thick is the magmatic crust at slow spreading oceanic ridges , 1996 .

[27]  S. Operto,et al.  Deep structure of the northern Kerguelen Plateau and hotspot-related activity , 1995 .

[28]  H. Schmincke,et al.  Syenite Nodules as a Long-Term Record of Magmatic Activity in Agua de Pao Volcano, Sao Miguel, Azores , 1993 .

[29]  D. Weis,et al.  Petrology and geochemistry of the Kerguelen Archipelago basalts (South Indian Ocean): evolution of the mantle sources from ridge to intraplate position , 1990 .

[30]  W. Hildreth,et al.  Crustal contributions to arc magmatism in the Andes of Central Chile , 1988 .

[31]  H. R. Shaw.  Links between magma‐tectonic rate balances, plutonism, and volcanism , 1985 .

[32]  J. Crisp.  Rates of magma emplacement and volcanic output , 1984 .

[33]  N. Watkins,et al.  Kerguelen: Continental Fragment or Oceanic Island? , 1974 .

[34]  B. Moine,et al.  The Neogene to Recent Rallier-du-Baty nested ring complex, Kerguelen Archipelago (TAAF, Indian Ocean): stratigraphy revisited, implications for cauldron subsidence mechanisms , 2004, Geological Society, London, Special Publications.

[35]  J. Cottin,et al.  Oceanic mafic granulite xenoliths from the Kerguelen archipelago , 1994, Nature.