Postintrusive thermal evolution of continental crust: A moving boundary approach

The structural setting of the Northwestern Mediterranean stems from tectonothermal processes which reflect on the nature of the crust. The Oligocene to Present evolution is here analysed with a thermal model which takes into account the significant extension of the continentallithosphere before the onset of sea-floor spread- ing in the bathyal zone. Subsidence data were used to set the boundaries of the oceanic realm which was com- pared with previous reconstructions inferred from other geophysical evidence. The thermal features of the transitional crust that lies between the oceanic crust and the stretched continental margins were also outlined. The Ligurian-Proven~al basin is a marginaI basin, whereas only the continental crust is expected in the Valen- cia trough. An evolutionary sketch of the study area that accounts for the observed subsidence and heat flux is proposed.

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Argon constraints on the early growth of felsic continental crust

Science Advances ◽

10.1126/sciadv.aaz6234 ◽

2020 ◽

Vol 6 (21) ◽

pp. eaaz6234 ◽

Cited By ~ 5

Author(s):

Meng Guo ◽

Jun Korenaga

Keyword(s):

Continental Crust ◽

Mantle Convection ◽

Thermal Evolution ◽

Early Growth ◽

Early Earth ◽

Crustal Growth ◽

Crustal Recycling ◽

Consistent Manner ◽

History Of ◽

Surface Environment

The continental crust is a major geochemical reservoir, the evolution of which has shaped the surface environment of Earth. In this study, we present a new model of coupled crust-mantle-atmosphere evolution to constrain the growth of continental crust with atmospheric 40Ar/36Ar. Our model is the first to combine argon degassing with the thermal evolution of Earth in a self-consistent manner and to incorporate the effect of crustal recycling and reworking using the distributions of crustal formation and surface ages. Our results suggest that the history of argon degassing favors rapid crustal growth during the early Earth. The mass of continental crust, highly enriched in potassium, is estimated to have already reached >80% of the present-day level during the early Archean. The presence of such potassium-rich, likely felsic, crust has important implications for tectonics, surface environment, and the regime of mantle convection in the early Earth.

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

10.5194/egusphere-egu2020-14296 ◽

2020 ◽

Author(s):

Geoffroy Mohn ◽

Michael Nirrengarten ◽

Andrea Schito ◽

Nick Kusznir ◽

Sveva Corrado ◽

...

Keyword(s):

Continental Crust ◽

Thermal Evolution ◽

Oceanic Lithosphere ◽

Seafloor Spreading ◽

Spreading Ridge ◽

Thermal Maturity ◽

Seismic Profiles ◽

Thinned Continental Crust ◽

Conjugate Margins ◽

Se China

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.

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