Transmogrification of ocean into continent: implications for continental evolution

Abstract

Significance This study proposes a geological mechanism for creating continental crust and lithosphere. When continents collide, the typical embayments and protrusions along their rifted margins make it likely that fragments of seafloor will be trapped within the growing mountain belt. These become preferential centers of sedimentation that eventually convert former seafloor into a unique form of continental crust and lithosphere, leading to characteristic temporal changes in the relative strength and uplift/subsidence of these regions. The Alpine–Himalayan mountain chain in Eurasia shows several stages of this process, which we further explore with a one-dimensional thermal-rheological model. In Asia, this process appears to have created a characteristic paired-mountain belt geomorphology (Himalaya/Tibet + Tian Shan) that has greatly strengthened the East Asian Monsoon.

Impact of Ancient Tectonics on Intracontinental Deformation Partitioning: Insights From Crustal Structures of the East Junggar‐Altai Area

“…Furthermore, the protective effect of the oroclines could lead to the preservation of oceanic basins inside them (X. Yang et al., 2022). The thick sediment pile within the trapped oceanic basins is highly radiogenic, the high radiogenic would gradually strengthen the crust and underlying lithosphere of these former oceanic fragments (Morgan & Vannucchi, 2022). With enhanced rheological strength and few pre‐existing decollements, the regions within oroclines would be highly resistant to deformation in subsequent intracontinental deformation processes.…”

Lower Crustal Rheology Controls Strain Partitioning and Mode of Intracontinental Deformation

“…The modern Tarim Basin has low heat flow (S. Liu et al., 2015), low topographic relief (Calignano et al., 2015), and experienced negligible Cenozoic deformation across the basin with flat‐lying and largely undeformed Cenozoic sedimentary strata (e.g., Guo et al., 2005). Although a transmogrification mechanism (Morgan & Vannucchi, 2022) would alternatively convert buried oceanic lithosphere (Kusky & Mooney, 2015) into continental lithosphere, based on this geologic history, and the observation of a voluminous Permian large‐igneous province (e.g., S. Yang et al., 2013), it has been interpreted that the Tarim continental block was welded to be a rigid craton‐like continent by Permian plume impingement across the western Tarim domain (X. Xu et al., 2023). This process ultimately thickened the Tarim lithosphere to its present‐day thickness of ∼200‐km (Y. Xu et al., 2002).…”

Various lithospheric deformation patterns derived from rheological contrasts between continental terranes: Insights from 2-D numerical simulations

“…It was then pushed northward by the Indian craton and was blocked by the Tarim/Qaidam craton during India-Asia collision, leading to double crustal thickness (Zhao and Morgan, 1985;Zhang et al, 2011). The lithosphere beneath the Tibetan Plateau does not thicken significantly like its crust, especially beneath northern Tibet (Owens and Zandt, 1997;Tunini et al, 2016). Numerous observations instead suggest that the Tibetan lithosphere has been detached from the crust and has sunk into deeper mantle, consistent with the presence of high-velocity regions in the deep mantle in western, southern and southeastern Tibet (Li et al, 2008;Feng et al, 2021).…”

“…A significant depression of the 660-km discontinuity beneath the Himalaya terrane and the uplift of 410-km discontinuity in western Tibet have also attributed to the presence of delaminated Tibetan lithosphere (Wu et al, 2022). In northern Tibet, anomalously high temperatures are assumed to be linked to a region of inefficient Sn propagation, while a remarkable low-velocity zone in the mantle and ultra-potassic volcanics also suggest lithosphere thinning (Barazangi and Ni, 1982;Turner et al, 1996;Owens and Zandt, 1997;Guo et al, 2006;Liang et al, 2012;Tunini et al, 2016). After lithosphere thinning commenced in the Miocene, the Tibetan Plateau rapidly grew outwards rapidly (Lu et al, 2018 and references therein;Molnar et al, 1993;Xie et al, 2023).…”