Lithospheric Alteration, Intraplate Crustal Deformation, and Topography in Eastern China

Abstract

Topography can be directly observed, but what controls topographic variation is not readily known. To investigate a prominent and remarkably consistent along‐trend topographic gradient belt (TGB) in intraplate eastern China and its connection to ongoing deformation and geodynamics, we examine the regional density structure of the crust and mantle lithosphere. We first use S velocities to derive an initial density and then refine the density model by joint inversion of topography and gravity. We use the final density model and receiver functions to strip away topographic contributions from the crust, and we subsequently estimate the thickness of the mantle lithosphere required to satisfy flexural isostasy. Crustal buoyancy overcompensates for the elevation change across the TGB. East of the TGB (eastern north China craton and southeastern south China), the lithosphere is thin (~ 90 km), suggesting that not only the eastern north China craton but also much of the eastern China has experienced lithospheric dismemberment. The TGB behaves as an important contour for the lithospheric thickness, except for the northeast China and Qinling‐Dabie. Proposed refertilization of the altered mantle lithosphere in the east side of TGB would result in even lower lithospheric thickness, while hydration and asthenosphere upwelling have the opposite effect. This systematic calculation gives a regional analysis of eastern China and could be a useful guide for the regions lacking seismic investigations.

New Insights Into the Heterogeneity of the Lithosphere‐Asthenosphere System Beneath South China From Teleseismic Body‐Wave Attenuation

“…Our findings of high  Δ p t provide another line of evidence to support the idea that easternmost China as a whole has undergone lithospheric dismemberment (Y. Deng & Levandowski, 2018;Q. Wang et al, 2017;T.…”

“…No matter the inverse approach, a pronounced negative Flexural isostatic LAB (Deng and Levandowski, 2018) Seismic LAB (Zhang et al, 2018a) Thermal LAB (Deng and Tesauro, 2016) ∼200 km to 400 km and attributed these anomalies to delaminated lithosphere from the SE Tibetan Plateau. Fu et al, (2017) observed high S-wave velocity from Moho depths to 150 km based on Rayleigh wave tomography over the ChinArray-I project.…”

“…low temperature and high strength within the lithosphere (Y Deng & Tesauro, 2016),. and thick flexural lithosphere (Y Deng & Levandowski, 2018…”

New Insights into Crust and upper Mantle Structure in Guangdong Province, China and Its Geothermal Implications

“…The receiver function results implied a lithosphere thickness of ~65 km in southeast China [11,31]. Deng and Levandowski proposed that the depth of the lithosphere-asthenosphere boundary (LAB) is ranging around 100 km, which is estimated by the final density model and receiver functions [12]. A joint inversion of Rayleigh wave dispersion data, topography, geoid height, and terrestrial heat flow with a probabilistic Monte Carlo method predicts the recent lithosphere in South China is ranging from 80-105 km [10].…”

“…These granites, Late Mesozoic granite, in particular, were formed by the remelting of the Neoproterozoic and Paleozoic crust [7] and extremely rich heat-producing elements (Th, U, and K) with average heat production of more than 5 µW/m 3 [8]. Second, various geophysical methods have led to the thin lithosphere (~80 km) present in South China [9][10][11][12]. Combining with studies on mantle peridotite enclaves/xenoliths in Paleozoic suggested that a lithospheric thinning process has occurred in Meso-Cenozoic [13][14][15].…”