Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific)

Natalie Raia, Donna L. Whitney, Christian Teyssier, Stéphane Lesimple

Research output: Contribution to journalArticlepeer-review

Abstract

Owing to the importance of serpentinites for planetary geochemical and geodynamic processes, there has been much work discerning the origins of their parent rocks, including distinguishing between serpentinites derived from a subducting plate versus overlying mantle in exhumed subduction complexes. The island of New Caledonia (SW Pacific Ocean) provides a rare window into Cenozoic Pacific subduction processes. The island is unique in exposing both an exceptionally preserved high-pressure, low-temperature subduction complex and one of the largest supra-subduction zone ophiolites in the world. Previous studies disagree on the origin of serpentinites in the subduction complex. In this study, we analyze 23 serpentinites from this complex for whole-rock major and trace element geochemistry and stable isotope (δD, δ18O) compositions. Our data reveal two distinct groups of serpentinites: Group I samples in the northern portion of the complex are pervasively serpentinized, and exhibit enriched heavy rare earth element (REE) compositions and δ18O values between +6.7‰ and +10.2‰. In contrast, Group II serpentinites in the south preserve relict orthopyroxene and olivine, and show depleted trace element compositions and comparatively lower δ18O values between +5.1‰ and +8.0‰. We interpret Group I serpentinites to derive from downgoing plate mantle, whereas Group II serpentinites derive from overlying mantle wedge, exhibiting remarkable similarity to the REE geochemistry of the structurally overlying New Caledonia ophiolite. Our results establish the subduction complex in New Caledonia as an unusual natural record of the entrainment and exhumation of mantle from both the overlying mantle wedge and the downgoing plate in an oceanic subduction zone.

Original languageEnglish (US)
Article numbere2022GC010395
JournalGeochemistry, Geophysics, Geosystems
Volume23
Issue number8
DOIs
StatePublished - Aug 2022

Bibliographical note

Funding Information:
The authors thank Chief Guiart and Chief Heiec, tribal leaders of Yambé and Diahoué, respectively, for their authorization to access the Poadja Massif, and Mr. Hervé and family for their interest in our work and assistance in communicating our presence and purpose to the community. At DIMENC (New Caledonia), Pierre Maurizot and Bernard Robineau are thanked for thoughtful discussions and granting use of rock processing facilities. The UT-Austin High-Temperature Stable Isotope lab is thanked for assistance with run setup and data quality evaluation, particularly Jaime Barnes, Jeff Cullen, and Dan Breecker. The authors acknowledge Anette von der Handt (UMN EPMA) and Bing Luo (UMN Raman) for technical expertise and assistance. Ashley Steiner and Charles Knaack (WSU), Katie Kelley and Janine Andrys (URI), and Stan and Karen Mertzman (Franklin & Marshall College) are thanked for assistance in acquiring whole rock analyses. Mario Ramos Arias (UNAM) is thanked for discussion and participation during the collection of a subset of these samples. The authors thank Enrico Cannaò and an anonymous reviewer for constructive reviews and Whitney Behr for editorial handling. This work was partially supported by two GSA Graduate Student Research Grants to N. Raia with additional support from NSF grant EAR-1949895 (to D. L. Whitney). Funding for the electron microprobe facility used in this research was provided by the NSF grant EAR-1625422. The Characterization Facility of the College of Science and Engineering at the University of Minnesota receives partial support from the NSF through the MRSEC program.

Funding Information:
The authors thank Chief Guiart and Chief Heiec, tribal leaders of Yambé and Diahoué, respectively, for their authorization to access the Poadja Massif, and Mr. Hervé and family for their interest in our work and assistance in communicating our presence and purpose to the community. At DIMENC (New Caledonia), Pierre Maurizot and Bernard Robineau are thanked for thoughtful discussions and granting use of rock processing facilities. The UT‐Austin High‐Temperature Stable Isotope lab is thanked for assistance with run setup and data quality evaluation, particularly Jaime Barnes, Jeff Cullen, and Dan Breecker. The authors acknowledge Anette von der Handt (UMN EPMA) and Bing Luo (UMN Raman) for technical expertise and assistance. Ashley Steiner and Charles Knaack (WSU), Katie Kelley and Janine Andrys (URI), and Stan and Karen Mertzman (Franklin & Marshall College) are thanked for assistance in acquiring whole rock analyses. Mario Ramos Arias (UNAM) is thanked for discussion and participation during the collection of a subset of these samples. The authors thank Enrico Cannaò and an anonymous reviewer for constructive reviews and Whitney Behr for editorial handling. This work was partially supported by two GSA Graduate Student Research Grants to N. Raia with additional support from NSF grant EAR‐1949895 (to D. L. Whitney). Funding for the electron microprobe facility used in this research was provided by the NSF grant EAR‐1625422. The Characterization Facility of the College of Science and Engineering at the University of Minnesota receives partial support from the NSF through the MRSEC program.

Publisher Copyright:
© 2022. The Authors.

Keywords

  • fluid-rock interaction
  • mantle wedge
  • New Caledonia
  • serpentinite
  • stable isotope
  • subduction

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