Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific)
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 co...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2022-08-01
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| Series: | Geochemistry, Geophysics, Geosystems |
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| Online Access: | https://doi.org/10.1029/2022GC010395 |
| _version_ | 1797638144940572672 |
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| author | Natalie H. Raia Donna L. Whitney Christian Teyssier Stéphane Lesimple |
| author_facet | Natalie H. Raia Donna L. Whitney Christian Teyssier Stéphane Lesimple |
| author_sort | Natalie H. Raia |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-03-11T12:58:17Z |
| format | Article |
| id | doaj.art-2d231bd0db9d4843a4053dcde4057bf3 |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T12:58:17Z |
| publishDate | 2022-08-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-2d231bd0db9d4843a4053dcde4057bf32023-11-03T16:55:34ZengWileyGeochemistry, Geophysics, Geosystems1525-20272022-08-01238n/an/a10.1029/2022GC010395Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific)Natalie H. Raia0Donna L. Whitney1Christian Teyssier2Stéphane Lesimple3Department of Earth & Environmental Sciences University of Minnesota Minneapolis MN USADepartment of Earth & Environmental Sciences University of Minnesota Minneapolis MN USADepartment of Earth & Environmental Sciences University of Minnesota Minneapolis MN USAService Géologique de la Nouvelle‐Calédonie Direction de l’Industrie, des Mines et de l’Energie Nouméa New CaledoniaAbstract 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.https://doi.org/10.1029/2022GC010395serpentiniteNew Caledoniamantle wedgesubductionstable isotopefluid‐rock interaction |
| spellingShingle | Natalie H. Raia Donna L. Whitney Christian Teyssier Stéphane Lesimple Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific) Geochemistry, Geophysics, Geosystems serpentinite New Caledonia mantle wedge subduction stable isotope fluid‐rock interaction |
| title | Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific) |
| title_full | Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific) |
| title_fullStr | Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific) |
| title_full_unstemmed | Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific) |
| title_short | Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific) |
| title_sort | serpentinites of different tectonic origin in an exhumed subduction complex new caledonia sw pacific |
| topic | serpentinite New Caledonia mantle wedge subduction stable isotope fluid‐rock interaction |
| url | https://doi.org/10.1029/2022GC010395 |
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