Evolution Of Cratons Research Articles

High-resolution 3-D lithospheric structure beneath the Qinling-Dabie orogenic belt from joint inversion of receiver functions and ambient noise

Resulting from the convergence of the Yangtze and North China Cratons, the Qinling-Dabie orogenic zone (QD) represents an important element in the central China orogenic system. To fully comprehend the craton evolution and lower crustal flow from the Tibetan Plateau, it is important to understand the crust and mantle structure of the QD. We reconstructed the three-dimensional lithospheric structure beneath the QD with high resolution using the joint inversion of receiver functions and ambient noise. Observations reveal that a high-velocity anomaly in the middle to lower crust beneath the western Qinling (WQL) orogen obstructs the eastward extension of a crustal low-velocity anomaly originating from the Tibetan Plateau. This finding provides unambiguous evidence that the WQL orogen is not crossed by eastward lower crustal flow from the Tibetan Plateau. The lithospheric mantle beneath the Weihe Rift and East Qinling orogen exhibits low-velocity characteristics, indicating that eastward asthenospheric flow from the Tibetan Plateau has caused substantial thermal-chemical erosion in the uppermost mantle beneath these regions. The results additionally indicate that the uppermost mantle high-velocity anomalies beneath the Dabie orogen is confined in a limited area and extends only to a depth of 70 km. We propose that during the Triassic, deeply subducted continental lithosphere returned into the uppermost mantle, forming the high-velocity anomalies beneath the Dabie orogen.

Embracing Craton Complexity at Depth

Variations within individual cratons, as well as across different cratons, are readily apparent at the Earth’s surface, providing indirect insight into the processes governing the formation and evolution of the underlying regions. However, our views at depth are more limited. As such, there is a risk of interpreting the cratonic lithosphere as a monolith. Recent modeling and advances in seismological imaging have enhanced our perspective of vertical variations within the cratonic lithosphere, which has helped build a general conceptual model. While lateral variations also are increasingly identified, their significance still presents unanswered questions. In this review, we summarize the current state of knowledge of cratonic lithospheric structure and demonstrate the importance of lateral heterogeneity in craton evolution and stability.

Evaluating the Rheological Controls on Topography Development During Craton Stabilization: Objective Approaches to Comparing Geodynamic Models

AbstractSurface topography is an important yet largely neglected aspect of the early evolution of cratons. The lateral accretion of cratonic nuclei inevitably forms orogenic belts that subsequently provide a sediment source for large, resource‐rich intracratonic basins, but to date, geodynamic models have focused exclusively on lithospheric root processes. Here we use two‐dimensional thermal‐mechanical models to study the topography and lithospheric deformation during 50 Myr of compression of a cratonic nucleus, to simulate the lateral accretion phase of craton growth in the Neoarchean. Although the cratonic nucleus thickens slightly during the compression phase, most of the deformation occurs in the regions adjacent to the nucleus that have weaker lithosphere. Here, crustal thickness triples developing high topography in excess of 10 km without active erosion. Models with different initial rheological parameters will have different final topography and lithosphere geometry, but in general it is difficult to shorten and deform the depleted cratonic nucleus, unless there are significantly weak heterogeneities in the mantle lithosphere. We apply two quantitative analysis techniques to objectively evaluate a multitude of model outputs. Cross‐correlation clustering (CCC) measures the degree of similarity between topography profiles and categorizes models based on the general topographic character. Six different topography families are possible in the context of our models and crustal strength is the most important parameter affecting the shape. From principal component analysis (PCA) we identify four dominant lithosphere geometries. When used together, these two methods provide distinct yet complementary information about the surface and subsurface deformation features in our models.

Secular craton evolution due to cyclic deformation of underlying dense mantle lithosphere

Secular craton evolution due to cyclic deformation of underlying dense mantle lithosphere

Continental Mid‐Lithosphere Discontinuity: A Water Collector During Craton Evolution

AbstractContinental mid‐lithosphere discontinuity (MLD) seems to be ubiquitous beneath cratons around the world with the dominant depth of 70–100 km, and is characterized by a shear‐wave velocity drop of 2%–7%, according to geophysical observations. The MLD is often considered to be related to a rheologically weak layer; however, the mechanism of MLD formation is widely debated. In this study, we have conducted systematic numerical modeling with a new and simplified deep hydration method to study the dynamics of craton evolution and MLD formation. The results indicate that the MLD may be induced by slow hydration processes within the mantle lithosphere during craton evolution. The top boundary of this hydrated layer is characterized by high water content and low shear‐wave velocities, and is consistent with the depth and properties of natural MLD observations. Thus, we propose that the MLD may act as a water collector during craton evolution.

Crustal structure beneath the central and western North China from receiver function analysis

The North China Craton (NCC) is one of the oldest cratons on earth. Several important tectonic transformations of Mesozoic-Cenozoic tectonic regime led to the destruction of the North China craton. The knowledge of crustal structure can provide important constraints for the formation and evolution of cratons. New maps of sediment thickness, crustal thickness (H) and vP/vS (κ) in the central and western NCC were obtained using sequential H-κ stacking. P-wave receiver functions are calculated using teleseismic waveform data recorded by 405 stations from ChinArray project. Benefiting from the densely distribution of temporary seismic stations, our results reveal details of the crustal structure in the study area. The thickness of sedimentary layer in North China ranges from 0–6.4 km, and the thickest sedimentary layer is in Ordos block and its surroundings (about 2.8–6 km); The thickness of sedimentary layer in the Mongolia fold belt and Yinshan orogenic belt is relatively thin (less than 1 km). The crustal thickness of the study area varies between 27–48 km, of which the crust of the North China Plain is about 30–33 km, the central NCC is about 33–40 km, and the Ordos block is 40–48 km thick. The average vP/vS ratios in the study area is mostly between 1.66 and 1.90, and that in the Yanshan-Taihang mountain fold belt is between 1.70 and 1.85, and that in the Ordos block is between 1.65 and 1.90, with an average value of 1.77, indicating the absence of a thick basaltic lower crust. The obvious negative correlation between crustal thickness and average vP/vS ratio within Ordos and Central Asia orogenic belt may be related to magmatic underplating during the crustal formation. There is no significant correlation between the crustal thickness and the vP/vS ratio in the Lüliang-Taihang mountain fold belt, which may be related to the multiple geological processes such as underplating and crustal extension and thinning in this area. The lack of correlation between crust thickness and topography in the central orogenic belt and the North China Basin indicates the topography of these areas are controlled not only by crustal isostatic adjustment but also by the lithospheric mantle processes.

A linked evolution for granite-greenstone terranes of the Pilbara Craton from Nd and Hf isotopes, with implications for Archean continental growth

Granite-greenstone terranes, such as in the Pilbara Craton (Western Australia), record the growth and stabilisation of Archean (>2.5 Ga) continental crust. Yet, uncertainty surrounds the formation of the silica-rich portions of these terranes, important for preservation of continental lithosphere, specifically whether this involved reprocessing of older continental nuclei over hundreds of millions of years, or rapid differentiation of juvenile mantle additions, as preserved in the greenstone belt volcanic sequences. In part, the uncertainty reflects difficulties with establishing the isotope evolution of the early Archean mantle, critical for ascertaining the time gap between the extraction of new crust and granitic emplacement in Archean cratons. To investigate the formation of silica-rich Archean crust, we report Hf and Nd isotope data for 46 mafic–ultramafic samples and zircon Hf isotope data for 83 felsic igneous rocks from the Pilbara Craton, selected to be representative of the major magmatic episodes from 3.56 to 2.72 Ga. The strikingly similar secular isotope trends defined by mafic and felsic rocks reveal a linkage between mantle and crustal processes throughout the history of the craton. From 3.56 Ga to 3.12 Ga, craton evolution was dominated by the transformation of juvenile mantle derived inputs into felsic igneous rocks on short timescales, thus recording sustained continental growth over 400 million years. Incorporation of older crust by felsic magmas was minor during this interval. Evolution toward sub-chondritic Nd and Hf after collision of the East and West Pilbara terranes at 3.1 Ga signals greater involvement of pre-existing crust in magma generation, possibly by recycling of crustal material into mantle source regions or by enhanced reworking of older, thickened cratonic lithosphere. Mafic–ultramafic rocks provide no evidence for anomalous or strongly depleted mantle domains in the Paleoarchean. Rather, the flat zircon εHf–time array indicates extraction of continental materials from mildly super-chondritic mantle from ca. 3.6 to 3.12 Ga and attests to a distinctive style of crust production that operated in the Archean. This study highlights the importance of comparing the mantle and crustal isotope records in order to reconstruct the crustal growth rates in ancient terranes.

Continental mid-lithosphere discontinuity: a water collector during craton evolution

Continental mid-lithosphere discontinuity: a water collector during craton evolution

Continental mid-lithosphere discontinuity: a water collector during craton evolution

Continental mid-lithosphere discontinuity: a water collector during craton evolution

Continental mid-lithosphere discontinuity: a water collector during craton evolution

Continental mid-lithosphere discontinuity: a water collector during craton evolution

Neoarchean to Rhyacian crustal records along the Middle Xingu River area, Amazonian craton

The Carajás (3.0–2.5 Ga) and Xingu-Iricoumé (1.99–1.86 Ga) blocks comprise the Central Amazonia Province (CAP) that is in contact with the Maroni-Itacaiúnas Province (MIP) within the Amazonian craton. The CAP is the oldest portion (Nd-TDM) of the craton and corresponds to an Archean nucleus bordered by younger Paleo-Mesoproterozoic mobile belts, including the MIP. Because the location and tectonic boundaries between these provinces are insufficiently known, we carried out a geological survey along the Middle Xingu River, cutting the WNW-ESE regional trend, to further understand cratonic evolution of the MIP and its southeastern boundary in this key area. Geochronologic results (Pb-evaporation and U-Pb SHRIMP in zircon and monazite), supported by petrographic and field observations, allowed identification of the following lithotypes and their ages: migmatitic gneisses (2859–2080 Ma), tonalitic gneisses (2554 ± 3 Ma, 2480 ± 9 Ma), enderbites (2114 ± 3 Ma), charnockites (2094 ± 4 Ma, 2084 ± 2 Ma), granodiorites (2079 ± 3 Ma), leucogranitic vein (2075 ± 2 Ma), and pelitic paragneisses (2062 ± 8 Ma). These ages are related to the reworking of Archean crust during Rhyacian magmatic arc amalgamation (2.22–2.13 Ga) and collision in the Transamazonian cycle (ca. 2.1 Ga).

Seismic anisotropy evidence for modified lithosphere below the Bohai Sea region, eastern North China Craton

The Bohai Sea is proposed as the center of deformation associated with destruction of the North China Craton, and its tectonic history is essential for understanding the response of craton evolution to oceanic subduction. However, interior deformation of the craton remains unclear due to a lack of high-resolution imaging in this region. Here, we present high-resolution 3-D azimuthally-anisotropic shear-wave velocity structure of the crust and uppermost mantle using direct inversion of Rayleigh-wave phase-velocity dispersion from ambient noise. The anisotropic velocity structures reveal significant consistency between the regional strain field and seismic activity in the shallow crust. The N-S fast direction and relatively high velocity anomalies observed in the uppermost mantle beneath the Tanlu fault zone, as well as prominent Moho uplift, support the conclusion that the Tanlu fault zone has facilitated lithospheric modification of the eastern North China Craton since late Mesozoic. Anisotropy images also indicate that the northern and southern Bohai Bay Basin have undergone different deformation histories. The strong and consistent azimuthal anisotropy within the uppermost mantle beneath the southern Bohai Bay Basin may originate primarily from re-orientation arrangement of the olivine induced by new lithosphere formed from rapid cooling of upwelling asthenosphere after lithosphere delamination due to the subduction of the (Paleo-) Pacific Plate.

From microanalysis to supercontinents: Insights from the Rio Apa Terrane into the Mesoproterozoic SW Amazonian Craton evolution during Rodinia assembly

AbstractDeciphering the tectono‐metamorphic evolution of Precambrian terranes can be difficult due to reworking by later superimposed events. Whole‐rock elemental and isotopic geochemistry and zircon U–Pb geochronology are often employed in those studies, but these approaches are often not sensitive to the presence of multiple events and medium‐grade metamorphic episodes. The Rio Apa Terrane (RAT), an allochthonous fragment of the Amazonian Craton, is a crustal block with a well‐characterized crustal evolution but with no detailed thermal constraints for its tectono‐metamorphic evolution. In contrast to previous studies, we show the existence of four tectono‐metamorphic events at c. 1,780, c. 1,625, c. 1,420–1,340, and c. 1,300–1,200 Ma on the basis of apatite, titanite, and rutile U–Pb, in situ white‐mica Rb–Sr, and in situ garnet Lu–Hf geochronology combined with mineral chemistry and phase‐equilibria modelling. The c. 1,780 Ma event is recorded in the basement of the Western domain, representing an extensional event coeval with the development of its Eastern domain in response to the retreat stage of the accretionary system. This is followed by juxtaposition of the Western and Eastern domains along a major crustal boundary at c. 1,625 Ma, which is defined by the magnetic profiles and zircon U–Pb–Hf data across the boundary. The third and fourth events correspond to progressive high‐pressure/medium‐temperature (HP/MT) metamorphism, characterized by an anticlockwise P–T path, suggesting a convergent‐to‐collisional tectonic setting. The RAT was accreted to the adjoining Paraguá Terrane at c. 1,420–1,340 Ma under an isobaric P–T evolution spanning ~530°C to 600°C and ~10.0 kbar. Subsequently, the combined Rio Apa and Paraguá terranes collided with the SW Amazonian Craton at c. 1,300–1,200 Ma, reaching P–T conditions of ~560–580°C and ~10.9–11.7 kbar during crustal thickening. This study reveals for the first time the existence of a HP/MT metamorphic evolution related to the growth of the SW Amazonian Craton as part of an accretionary orogenic system during Rodinia assembly in the Palaeoproterozoic to Mesoproterozoic.

Paleoproterozoic tectonic evolution of the Yangtze Craton: Evidence from magmatism and sedimentation in the Susong area, South China

Paleoproterozoic and Archean rocks in the poorly exposed Yangtze Craton provide a unique proxy for understanding early cratonic evolution. In this study, we report the newly discovered Paleoproterozoic granitoids, mafic dikes, and metasedimentary rocks in the Susong area near the northern margin of the Yangtze Craton. The zircon U–Pb analysis results of the Luohanjian granite (hereinafter referred to as LHJ-granite) and mafic dikes yielded 207Pb/206Pb ages of 2020–2002 Ma and 1837 ± 21 Ma, respectively. Metasedimentary strata that were intruded by the mafic dikes yielded detrital zircon 207Pb/206Pb ages of 2.55–2.32 Ga and 2.15–1.93 Ga, suggesting a depositional age of ∼ 1.90–1.85 Ga for the metasedimentary rock. The whole-rock εNd(t) and zircon εHf(t) values of the LHJ-granite were negative and ranged from − 10.4 to − 9.4 and − 11.4 to − 9.0, with corresponding TDM2 model ages of 3.3–3.2 Ga and ∼ 3.1 Ga, respectively. This implies that the granitic magma originated from the reworking of ancient pre-existing crustal components. The granitoids were weakly peraluminous (A/CNK = 1.00–1.18) with high SiO2 concentrations of 71.98–76.00 wt%, LREE enrichment, high (La/Yb)N values of 26.55–100.49, and moderately negative Eu anomalies, characterized by the enrichment of Rb, Ba, Th, U, and Nd, and the relative depletion of Nb, Ta, Sr, P, and Ti. These granite samples exhibited a negative correlation between SiO2 and P2O5 and low Rb/Ba (0.15–0.33) and Rb/Sr (0.30–1.55) ratios. All these features indicate that the LHJ-granite is most likely belongs to I-type granite, which may have formed via the reworking of the TTG gneiss during subduction–collisional events. In combination with the mafic dikes and metasedimentary strata, our study proposes a mid–late Paleoproterozoic geological transition from a compressional to an extensional setting, indicating a tectonic shift from a collision orogeny (2.0 Ga) to a post-collision extensional environment (1.84 Ga) in the Susong region.

Reconstructing craton‐scale tectonic events via in situ Rb‐Sr geochronology of poly‐phased vein mineralization

AbstractFault‐ and fracture‐hosted multi‐stage mineral assemblages that formed by fracture reactivation and fluid migration, constitute archives of the tectonic evolution of Precambrian cratons. Complex intergrowth patterns of these mineral records often hinder absolute dating of mineralization events for geological models. We apply LA‐ICP‐MS/MS in situ Rb‐Sr dating of single crystal growth zones in sub‐mm‐wide vein mineralization assemblages including illite, K‐feldspar, albite, calcite, mica, zeolites, fluorite and/or epidote at three Palaeoproterozoic crystalline bedrock sites over 300 km apart in the Fennoscandian Shield. The dating campaign reveals multiple age clusters between ca. 1757 ± 15 and 355 ± 12 Ma correlating with fluid flow and fracture reactivation events initiated by far‐field orogens and their foreland basin evolution. This new approach for reconstructing geological histories of Precambrian cratons connects micro‐scale age determinations of different mineral growth zones in fractures with regional‐scale crustal dynamic responses to tectonic events.

The NW Amazonian Craton in Guainía and Vaupés departments, Colombia: Transition between orogenic to anorogenic environments during the Paleo-Mesoproterozoic

In order to improve our understanding of the NW-Amazonian Craton evolution, we present new petrographic, geochemical and geochronological analyses of 27 samples from the geotectonic Rio Negro-Juruena Province in eastern Colombia (Guainía and Vaupés departments). New LA-ICP-MS zircon U-Pb ages suggest that the oldest known rocks in Colombia are metamorphic rocks (migmatitic gneisses) with ages between ~ 1850 and ~ 1800 Ma, and gneisses and granitoids with ages between ~ 1800–1720 Ma which form part of the Mitú Complex, interpreted as the result of Statherian collisional and orogenic events (Querari Orogeny). Detrital zircons in low-grade meta-sedimentary sequences of the Tunuí Group (sandstones, conglomeratic sandstones and mudstones), that crop out over almost the entire basement, indicate older than ~ 1770 Ma source rocks. Intrusions of different suites of granitic rocks with syn- to post-collisional affinities suggest a termination of the collisional events between ~ 1600–1500 Ma which had affected the whole region, occasionally metasomatically overprinting parts of the Tunuí meta-sedimentary sequence. The recognizable metamorphic and magmatic-processes finish with ~ 1400–1340 Ma anorogenic granites without signs of tectonic deformation, resembling anorogenic granites in the Western Amazonian Craton in Brazil and the Parguaza Batholith in Venezuela. This study allows us to conclude that the basement records the collision of a continental arc (Rio Negro-Juruena Province) against the NW-Amazonian Craton (Ventuari-Tapajos Province) and its subsequent transition to anorogenic conditions in a continental rift setting long before the actual stable craton conditions.

Hydrothermal Origin of Early Permian Chert Nodules in the Central North China Craton Linked to Northern Margin Cratonic Activation

AbstractSedimentary chert phases from the Archean to the present are widely used to trace sedimentary environments and tectonic settings. Recently, chert nodules occurring within carbonates have been the subject of possible hydrothermal or biogenic origin, in lieu of a diagenetic origin. However, chert nodules from a vast cratonic basin represent extremely rich silica accumulations but less noted is how they respond to submarine hydrothermal activity (and/or surface siliceous organism productivity). The links between the cratonic‐type chert depositions and environmental changes regarding cratonic evolution need to be revisited at a large temporal‐spatial scale. The chert nodules are widespread throughout the Lower Permian Taiyuan Formation in the North China Craton (NCC). Several Taiyuan chert‐rich successions across the NCC have been selected to study possible links between chert deposition and cratonic evolution in scenario of partial cratonic activation of the northern NCC margin during the Late Paleozoic. Based on stratigraphic correlation, the chert nodules are ubiquitously, evenly distributed throughout the Taiyuan Formation at a large craton‐basin scale from the northern to southern interior NCC. Petrological results, elemental abundances, together with silicon and oxygen isotopic compositions of chert samples infer significant hydrothermal contributions for the silica accumulations. Therefore, the cratonic‐scale chert depositions of hydrothermal origin infer a giant and remote silica reservoir, linking to the large igneous province and magmatism in the NCC northern margins. The Taiyuan chert nodules could be unique marine sedimentary archives recording the Late Paleozoic NCC partial activation, which also generated continental records of igneous rocks, bauxites and tuffs. The strong tectonics of the northern margin, south‐dipping topography and northward transgression of the Early Permian NCC facilitated the chert deposition on the shallow marine platform in the cratonic interior.

Sharpness of the Midlithospheric Discontinuities and Craton Evolution in North China

AbstractThe lithospheric layering and evolution of Archean cratons can be effectively constrained by seismic properties. We present fine‐scale lithospheric discontinuity images of the North China Craton (NCC) using the seismic daylight imaging (SDI) technique, which is also known as the autocorrelogram method. With the aid of large‐scale surface‐wave velocity models, the characters of autocorrelograms related to lithospheric discontinuities in the NCC are investigated. Spatial variation in discontinuity characteristics is revealed across the craton. In the modified/destroyed eastern NCC, both the midlithospheric discontinuity (MLD) and the lithosphere‐asthenosphere boundary (LAB) are rather sharp (~2 km). Various dynamic processes, including juvenile underplating, asthenospheric upwelling, and corner flow induced by paleo‐Pacific Plate subduction, may contribute to such sharp interfaces. In the stable western NCC, P wave reflections cannot easily reveal the LAB, suggesting a diffuse (thicker than 30 km) lithosphere‐asthenosphere transition (LAT). Multiple MLDs are also found that may have arisen during craton formation and multiple phases of rejuvenation of the cratonic lithosphere as evidenced by the petrological results. The use of higher‐frequency data enables us to distinguish among the lithospheric discontinuity styles and favor multiple origins of the MLDs and LAB in the cratonic lithosphere.

Assembly of the Siberian Craton: Constraints from Paleoproterozoic granitoids

The paper presents a synthesis of geochronological, geochemical, and isotopic data on Paleoproterozoic granitoids in the Siberian craton and, in some cases, on volcanics related to these granitoids. Different evolution stages of the craton, including its assembly, are recorded in several major events in the history of Paleoproterozoic granitic magmatism. They are 2.52–2.40 Ga and 2.15–2.04 Ga granitoids of different tectonic settings; 2.06–2.00 Ga subduction-related granitoids; 2.00–1.87 Ga collisional granitoids; 1.88–1.84 postcollisional granitoids, and 1.76–1.71 Ga within-plate (anorogenic) varieties. Granitoids with ages of 2.5–2.4 Ga and 2.15–2.04 Ga are distributed locally in separate blocks and terranes which later entered the craton structure. These rocks are of different types and represent different tectonic settings of the respective blocks and terranes, i.e., the Siberian craton did not exist yet as a single unit at that time. The 2.06–2.00 Ga subduction-related granitoids and volcanics are found in the southern and southeastern craton parts. Magmatism of that time interval probably was associated with subduction beneath the Archean Olekma-Aldan and Anabar continental microplates and with the formation of their active margins. Granitoids of the 2.00–1.87 Ga age interval represent a collisional stage of the craton evolution. Collisional granitoids that intruded between 2.00 and 1.95 Ga record the first large-scale stage of craton assembly with collisions of terranes that had built the core of the Anabar, Aldan, and Olenek superterranes. The intrusions of 1.95–1.90 Ga granitoids mark the consolidation of the southeastern craton part. Collisional granitoids with the 1.90–1.87 Ga ages, which are especially abundant in the south and southwest of the craton but almost lack from the north, led to general assembly of the craton. The granitoid and volcanic magmatic activity of 1.88–1.84 Ga in the craton south produced the South Siberian postcollisional magmatic belt that had completed the assembly of the craton which, in its turn, may have been part of the Paleoproterozoic supercontinent of Columbia. Granitic intrusions at 1.76–1.71 Ga are limited to the southwestern and southeastern craton parts and correspond to a setting of continental extension which never led to the breakup of the craton.

Isostatic state and crustal structure of North China Craton derived from GOCE gravity data

The crustal structure between different subregions of the North China craton (NCC) plays an important role in improving our understanding on the craton evolution. Here we present a flexural Moho map and isostatic residual gravity field of the NCC derived from the GO_CONS_GCF_2_TIM_R3 model.We first investigate the influence of additional sources on the forward flexure calculation, especially the distinct thinning of the lithospheric thickness from west to east. After removing the gravity effects of the LAB undulations, the flexural Moho and isostatic residual gravity field of the NCC are calculated using the Vening-Meinesz regional isostasy models. There are high to medium positive residual anomalies beneath the Eastern block and Trans-North China Orogen, while negative residual anomalies delineate the Yinshan block, Ordos plateau and Khondalite belt. This obvious disparity is consistent well with the decreasing depth of the flexural Moho from west to the east. A profile across the Eastern block, Trans-North China orogen and the Western block was employed to construct a density structure of the crust and uppermost mantle. By comparing the surface topography, Bouguer gravity, isostatic Moho and seismological Moho undulations, we find that the flexural Moho is much shallower than the seismic Moho beneath the northern margin of the Ordos block, possibly indicating the over-compensated isostatic state caused by the dominant NW–SE oriented compressional deformation in the lithospheric processes. Density modeling results further predicted that a high density body may exist in the lower crust beneath the northern margin of the Ordos block, which could be a westward-dipping upper-middle crust remnant stagnating in the lower crust beneath the Western block. Medium to high pressure metamorphism of granulite facies or eclogite facies, resulting from subsequent continental thickening during the continental collision may be responsible for modifying the remaining subduction remnant.