EGU2020-14296
https://doi.org/10.5194/egusphere-egu2020-14296
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Tectono-magmatic and thermal evolution of the SE China margin-NW Palawan breakup

Geoffroy Mohn1, Michael Nirrengarten1, Andrea Schito2, Nick Kusznir3, Sveva Corrado2, Stephen Bowden4, Manuel Pubellier5, François Sapin6, and Hans-Christian Larsen7
Geoffroy Mohn et al.
  • 1Université de Cergy-Pontoise, Departement de Geosciences et Environnement, Neuville sur Oise, France (geoffroy.mohn@u-cergy.fr)
  • 2Università degli Studi di Roma Tre, Dipartimento di Scienze, Sezione di Scienze Geologiche, Largo San Leonardo Murialdo 1, 00146 Rome, Italy
  • 3University of Liverpool, Department of Earth and Ocean Sciences, Liverpool, UK (L69 3BX)
  • 4University of Aberdeen, Department of Geology and Petroleum Geology, Aberdeen AB24 3UE, UK
  • 5Laboratoire de Géologie, UMR 8538, École Normale Supérieure, CNRS, Paris, France
  • 6Total SA Frontier Exploration R&D Program, CSTJF, Pau, France
  • 7Geological Survey of Denmark and Greenland, Copenhagen, Denmark

Continent Ocean Transitions (COTs) record the processes leading to continental breakup and localized oceanic accretion initiation. The recent IODP Expeditions 367-368 and 368X at the SE China margins combined with high quality multi-channel seismic profiles provide a unique dataset to explore the tectono-magmatic and thermal evolution from final rifting to early seafloor spreading. To investigate these issues, we developed a multi-disciplinary approach combining reflection seismic interpretations with geophysical quantitative analysis calibrated thanks to drilling results, from which we measured and modelled the thermal maturity in pre-/syn- to post-rift sediments.

Drilling results show that the transition from the most thinned continental crust to new, largely igneous crust is narrow (~20 km). During final rifting, decompression melting forming Mid-Ocean Ridge type magmatism emplaced within thinned continental crust as deep intrusions and shallow extrusive rocks concomitant with continued deformation by extensional faults. The initial igneous crust of the conjugate margins is asymmetric in width and morphology. The wider and faulted newly accreted domain on the SE China side indicates that magmatic accretion was associated with tectonic faulting during the formation of initial oceanic lithosphere, a feature not observed on the conjugate Palawan side. We suggest that deformation and magmatism were not symmetrically distributed between the conjugate margins during the initiation of seafloor spreading but evolved asymmetrically prior to the spreading ridge stabilising.

Organic matter from post-rift sediments has low thermal maturities due to limited burial and the absence of late post-rift magmatism. In contrast, pre to syn-rift sediments show significant variability in thermal maturities across the COT. Localised high thermal maturities for the pre- to syn-rift sediments requires that significant additional heat be imparted at shallow depths during breakup, likely related to magmatic intrusion or subsurface expressions of volcanism. The heterogeneous variation in thermal maturity observed across the COT reflects localised thermal perturbations caused by magmatic additions.

How to cite: Mohn, G., Nirrengarten, M., Schito, A., Kusznir, N., Corrado, S., Bowden, S., Pubellier, M., Sapin, F., and Larsen, H.-C.: Tectono-magmatic and thermal evolution of the SE China margin-NW Palawan breakup, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14296, https://doi.org/10.5194/egusphere-egu2020-14296, 2020

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