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Journal Articles Contributions to Mineralogy and Petrology Year : 2020

Serpentinization of New Caledonia peridotites: from depth to (sub-)surface

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1
Marc Ulrich
Manuel Muñoz
  • Function : Author
Philippe Boulvais
  • Function : Author
Michel Cathelineau
  • Function : Author
Dominique Cluzel
  • Function : Author
  • PersonId : 1065693
Stéphane Guillot
  • Function : Author
Christian Picard
  • Function : Author

Abstract

Serpentinization processes occur at geological settings notably during oceanic subduction and obduction, where mantle rocks interact with water. Different types of serpentine minerals form according to temperature and pressure conditions, and potentially chemical exchanges. Therefore, the characterization of serpentine minerals, and the possible occurrence of multiple serpentine generations in mantle rocks provide essential constraints on the conditions of fluid-rock interactions in the mantle. The serpentinite sole of the Peridotite Nappe of New Caledonia (Southwest Pacific) is the result of several superimposed serpentinisation events. The latter were discriminated using mineralogical and geochemical approaches and modeling. Lizardite represents more than 80% of the entire serpentine content of the ophiolite. It is crosscut by several veins of other serpentine species in the serpentinite sole. The relative chronology appears as follows: lizardite 1 → lizardite 2 → antigorite → chrysotile → polygonal serpentine. The transition from primary/magmatic minerals to lizardite 1 is almost isochemical. Then, the development of lizardite 2 yields an enrichment in fluid-mobile elements such as Cs, Rb, Ba, U and light rare-earth elements and an apparent increase of the Fe 3+ /Fe T ratio. The modeling of δ 18 O values (1.9-13.9‰) and δD values (88-106‰) of all serpentine species through Monte-Carlo simulations show that New Caledonia serpentines were mainly formed in equilibrium with fluids released by the dehydration of altered oceanic crust (AOC) during subduction between 250 and 350 °C. AOC-derived fluids are not the unique source of fluids since a low temperature (100-150 °C) meteoric component is also predicted by the models. Thus, serpentine acts as a tape-recorder of fluid-rock interactions into the mantle from depth to (sub-)surface.
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hal-03510813 , version 1 (30-01-2022)

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Marc Ulrich, Manuel Muñoz, Philippe Boulvais, Michel Cathelineau, Dominique Cluzel, et al.. Serpentinization of New Caledonia peridotites: from depth to (sub-)surface. Contributions to Mineralogy and Petrology, 2020, 175 (9), pp.91. ⟨10.1007/s00410-020-01713-0⟩. ⟨hal-03510813⟩

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