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

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