Moho depth model for the Central Asian Orogenic Belt from satellite gravity gradients

Abstract

The main purpose of this study is to construct a new 3‐D model of the Central Asian Orogenic Belt (CAOB) crust, which can be used as a starting point for future lithospheric studies. The CAOB is a Paleozoic accretionary orogen surrounded by the Siberian Craton to the north and the North China and Tarim Cratons to the south. This area is of great interest due to its enigmatic and still not completely understood geodynamic evolution. First, we estimate an initial crustal thickness by inversion of the vertical gravity component of the Gravity Field and Steady‐State Ocean Circulation Explorer (GOCE) and DTU10 models. Second, 3‐D forward modeling of the GOCE gravity gradients is performed, which determines the topography of the Moho, the geometry, and the density distribution of the deeper parts of the CAOB and its surroundings, taking into account the lateral and vertical density variations of the crust. The model is constrained by seismic refraction, reflection, and receiver function studies and geological studies. In addition, we discuss the isostatic implications of the differences between the seismic Moho and the resulting 3‐D gravity Moho, complemented by the analysis of the lithostatic load distribution at the upper mantle level. Finally, the correlation between the contrasting tectonic domains and the thickness of the crust reveals the inheritance of Paleozoic and Mesozoic geodynamics, particularly the magmatic provinces and the orocline which preserve their crustal features.

Structures and geodynamics of the Mongolian tract of the Central Asian Orogenic Belt constrained by potential field analyses

“…However, our study shows that firstorder topographic features are mainly related to the Cenozoic reactivation of Permian-Triassic upper crustal steep deformation zones. Similarly, the Altai and Tien Shan mountain ranges, associated with significant increases of the Moho depth (Guy et al, 2017), correlate well with the positions of the crustal scale Paleozoic tectonic units e.g. Tien Shan subduction wedge in the south and the MAAW in the north (Xiao et al, 2015).…”

“…(2) the Moho topography established by seismic and gravity studies (Guy et al, 2017;Wang et al, 2003; J o u r n a l P r e -p r o o f Zhao et al, 2003); and (3) the density values assigned according to dominant lithologies forming both units, some of them deduced from thermodynamic modelling of metamorphic rocks (Jiang et al, 2016), and the magnetic susceptibility values from general tables (e.g. Clark and Emerson, 1991).…”

Revision of the Chinese Altai‐East Junggar Terrane Accretion Model Based on Geophysical and Geological Constraints

“…This discrepancy between upper and deep crustal signal trends indicates that the origin of the strong gradient north of the EZ is located in the deep crust, probably reaching the Moho depth. It is therefore possible that the observed gradient is due to important thickening of the Chinese Altai crust and the formation of an unusually thick orogenic root during Cenozoic convergence (Guy et al, 2017). In both cases, the surface traces of the EZ portrayed in Figure 14 are probably an unsuccessful candidate for contact between the two crustal domains.…”

The Lithospheric Structure of the Saharan Metacraton From 3‐D Integrated Geophysical‐Petrological Modeling

“…(2016), Guy et al. (2017), and Holzrichter et al. (2016) reported that gravity gradients are particularly sensitive to the density structure of the crust and uppermost mantle.…”

“…Bouguer anomaly values of −95 mGal are observed beneath the DD, whereas the TM and the HS show values that range between −85 and −80 mGal. The Murzuq, Al-Kufrah, and Chad basins are characterized by Bouguer anomaly values of approximately −70, approximately −45, and approximately −20 mGal, respectively.In addition to gravity data, satellite gravity gradient data at 225 km height were used for the evaluation of modeling results(Figure 3) Bouman et al (2016),Guy et al (2017),and Holzrichter et al (2016). reported that gravity gradients are particularly sensitive to the density structure of the crust and uppermost mantle.…”