Three‐Dimensional Density Structure of the Pamir Plateau and Adjacent Regions: Implications for Deep Tectonics, Dynamics, and Metallogeny

The Pamir Plateau is situated at the northwestern edge of the India–Eurasia Plate collision zone, making it a key region for studying continental collision and plateau uplift. The deep structure and dynamic processes of this region have long been of great scientific interest. This paper synthesizes recent advancements in the application of geophysical techniques to investigate the deep structure of the Pamir Plateau. The study focuses on the heterogeneity of the crust and lithosphere, the morphology of the Moho and the double Moho structure, the depth variations of the lithosphere‐asthenosphere boundary (LAB), and the complex features of the mantle transition zone (MTZ). The results indicate that the deep tectonic structure of the Pamir region is closely associated with subduction of the Indian Plate, the southward compression of the Asian lithosphere, and lateral tectonic interactions from the Tarim Basin, which jointly drive the region's uplift and deformation. The paper further examines the deep interactions between the Pamir Plateau and adjacent regions. Additionally, the study discuss key controversies in current research, such as the spatial relationship between the Moho and deep seismic zones, the mechanisms of lithosphere delamination, and its effects on shallow structural deformation, etc.

The improved Moho depth imaging in the Arabia-Eurasia collision zone: A machine learning approach integrating seismic observations and satellite gravity data

The Eastern Pontide orogenic belt is divided into three subzones (northern, southern and axial zones) based on present lithologies and facies associations. NE-SW-, NW-SE- and E-W-trending fault systems, which play an important role in palaeotectonics and neotectonics of the Eastern Pontides, separate these zones. Three different methods were used to estimate the Moho depth from observed gravity value, namely (i) empirical relationship between Moho depth and Bouguer anomaly; (ii) spectral analysis of the radial wave number and; (iii) by the gravity inversion method. Power spectrum, a statistical approach, is a widely used technique to determine the depth of geological sources successfully. The empirical linear relations between the Bouguer anomalies and seismically determined crustal thicknesses have been used to compute depths to the Conrad and Moho discontinuities, which are consistent with the average depths obtained from the power spectrum method. The crustal structure was also determined from the inversion of a Bouguer anomaly profile along longitude 39°. Gravity inversion results are consistent with those obtained from the empirical relations and power spectrum methods. We calculated the maximum crustal thickness of 43.8 km in the studied region by using the gravity inversion method, which also showed that crustal thickness increases from north to south.

The data of Bouguer gravity and topography are inverted to obtain the crust thickness of China. In order to reduce the effect of regional non-isostasy we corrected the reference Moho depth in the inversion with regional topography relief, and performed multiple iterations to make the result more reliable. The obtained crust thickness of China is plotted on a map in cells of 1°×1°. Then we analyzed the correlation between the Bouguer gravity anomaly and fluctuation of the Moho depth. A good linear correlation is found, with a correlation coefficient of −0.993. Different correlation coefficients, 0.96 and 0.91, are found for the data in land and ocean region, respectively. The correlation result also shows that the boundary between land and ocean is generally along the bathymetric line of −800 m. In order to examine the influence of the Earth’s curvature on the calculated result, we tried two inversion models: the inversion for the whole region and the inversion for 4 sub-regions. The difference in the crust thickness deduced from the two models is less than 5 km. Possible explanation for the difference is discussed. After comparing our result with that of other studies, we suggest that with our method the Bouguer gravity and the topography data can be independently inverted to obtain the crust thickness of China and its adjacency.

Crustal thickness beneath Atlas region from gravity, topographic, sediment and seismic data

A model for the structure, composition and evolution of the Kenya rift

Density structure and isostatic state of the crust in the Longmenshan and adjacent areas

The crust and upper mantle structure beneath Yunnan from joint inversion of receiver functions and Rayleigh wave dispersion data

The Moho depth, crustal thickness and fault systems of the East Vietnam Sea (EVS) are determined by 3D interpretation of satellite gravity. The Moho depth is calculated by 3D Parker inversion from residual gravity anomaly that is obtained by removing the gravity effects of seafloor and Pre-Cenozoic sediment basement topographies from the free air anomaly. The 3D inversion solution is constrained by power density spectrum of gravity anomaly and seismic data. The calculated Moho depths in the EVS vary from 30–31 km near the coast to 9 km in the Central Basin. A map of the lithosphere extension factor in the Cenozoic is constructed from Moho and Pre-Cenozoic sediment basement depths. The fault systems constructed by the maximum horizontal gradient approach include NE-SW, NW-SE, and N-S oriented faults. Based on the interpretation results, the EVS is sub-divided into five structural zones which demonstrated the different characteristics of the crustal structure.

Moho depth inferred from gravity and topography in an intraplate area (Iberian Chain)

Global volcanic arc magma composition correlates with thickness of both arc crust (Moho depth) and arc lithosphere (LAB depth): A revealing message on arc basement histories and arc magmatism

Considering the influence of the density anomaly of the crust and upper mantle on the gravity, we provide a new arithmetic to invert the crustal thickness. Applying the result of seismic tomography, we calculated the lateral density heterogeneity of the crust and upper mantle and the gravity anomalies caused by such lateral density heterogeneity, and then subtracted gravity anomalies caused by mentioned density anomalies from observational Bouguer anomalies, finally in view of the correction on the initial crustal thickness based on the hypothesis of isostasy, inverted the regional crustal thickness. Using the data of seismic tomography from XU et al, we inverted the Moho depth beneath northwestern China. It is shown that the gravity anomalies on the surface of the earth are −6×10−4 m/s2–×10−4 m/s2. Compared with the result inverted directly using Bouguer anomalies, this method can bring correction of 6 km to the Moho depth. And this method make it further mature in theory and feasible in practice to invert the thickness of the crust using data of grarity and provide a new arithmetic for us to understand the conformation of the Moho.

Inverse and 3D forward gravity modelling for the estimation of the crustal thickness of Egypt

The gravity and magnetic survey lines of about 13,500 km were carried out in the centraland northern parts of the South China Sea from 1977 to 1978. The results obtained showthat the Bouguer gravity and magnetic anomalies have a tendency to increase gradually theirvalues from the northern continental shelf, through the slope, to the central abyssal basin of theSouth China Sea. The change in free-air gravity anomaly values coincides to a certain degreewith the undulation of the sea-bottom topography. The primary factor determining regionalvariation of the Bouguer gravity anomayl values is the Moho depth. The main factor deter-mining the magnetic anomly values is the nature of the basement rock. The high magnetieand Bouguer gravity anomaly values observed in some fault basin areas are inferred to becaused by draping the basic and ultrabasic magma extruding along the faults on the basementof the metamorphic rock,or by intrusion of the same magma into the basement.

Lithospheric structure of the South China Sea and adjacent regions: Results from potential field modelling