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The Mongol‐Okhotsk suture and the Adaatsag ophiolite belt are associated with the closure of the Mongol‐Okhotsk paleo‐ocean and are located within the Central Asian Orogenic Belt (CAOB) and Mongolia. The suture zone is flanked by volcanic‐plutonic belts that host significant metallogenic zones, containing deposits of copper and gold. The tectonic evolution of this region is not fully understood and the lithospheric structure has been poorly studied. We analyze magnetotelluric data and generate a model of the electrical resistivity distribution across this region. Whereas the northern segment has a sharp transition from a high‐resistivity upper crust to a low‐resistivity lower crust, as observed beneath the Hangai Dome, the southern segment does not show this transition. A wide, low‐resistivity zone (1–100 Ωm) imaged in the crust and lithospheric mantle is coincident with the Mongol‐Okhotsk suture and ophiolite, revealing a clear and significant lithospheric‐scale feature. Across the profile, numerous narrow, vertically oriented, low‐resistivity features (1–100 Ωm) are spatially associated remarkably well with the proposed boundaries of tectonic domains. These results confirm ideas about the development of the CAOB. Some of these low‐resistivity features are beneath the surface locations of large mineral zones, and likely represent fossil fluid pathways. We show congruent seismic velocity models for comparison and the results show a large‐scale low‐velocity anomaly (decrease of 2%–3%) that correlates with the location of the low‐resistivity anomaly below the Mongol‐Okhotsk suture. The geophysical results, combined with geological and geochemical data, provide insights into the structure of this region and help shed light on unanswered questions. When the ancient Mongol‐Okhotsk ocean closed, due to subduction from tectonic re‐arrangement, it left the Mongol‐Okhotsk suture zone and the Adaatsag ophiolite as a trace of its location. Similarly, other tectonic boundaries are hypothesized to exist from terrane accretion across the Central Asian Orogenic Belt (CAOB) and Central and Southern Mongolia, which is located between the Siberian and North China cratons. This region is also rich in economically significant copper and gold deposits. The tectonic evolution of this region and especially the lithospheric structure is not fully understood and has been poorly studied. We analyze magnetotelluric data and generate a model of the electrical resistivity distribution. Additionally, we show models of the seismic velocity for comparison. Examining multiple complementary geophysical models helps to reduce interpretation uncertainty. Anomalies are observed in both models (e.g., low resistivity and low velocity). The suture zone is proven to be a strong lithospheric‐scale boundary. The proposed boundaries of tectonic domains are also imaged, confirming ideas about the development of the CAOB, and solving some controversies. Lithospheric‐scale, wide, low‐resistivity zone revealed below the ophiolite belt associated with the closure of the Mongol‐Okhotsk oceanVertical, narrow low‐resistivity features aligned with proposed tectonic boundaries and locations of large mineral zones (copper and gold)The northern part of central Mongolia has a sharp mid‐crustal transition from high to low resistivity, whereas the southern part does not Lithospheric‐scale, wide, low‐resistivity zone revealed below the ophiolite belt associated with the closure of the Mongol‐Okhotsk ocean Vertical, narrow low‐resistivity features aligned with proposed tectonic boundaries and locations of large mineral zones (copper and gold) The northern part of central Mongolia has a sharp mid‐crustal transition from high to low resistivity, whereas the southern part does not

The tectonic dynamics of the Lhasa‐Gangdese terrane, southern Tibet, are still unclear and open questions persist regarding the structure, physical properties, and rheology of the lithosphere. A three‐dimensional electrical resistivity model was generated beneath the Lhasa terrane, 79°−94°E and 28°–33°N, an area of ∼1,500 by ∼600 km, using data from 537 magnetotelluric measurements. To overcome computational challenges, we present an approach in which multiple high‐resolution models from overlapping subregions are combined by means of an error‐weighted averaging scheme to construct a continuous electrical resistivity model. Based on the electrical structure, the rheology of the mid‐lower crust was investigated by constraining the melt fraction, in order to explore controls on dynamic mechanisms from a whole‐system perspective. The models shed light on the vertical and lateral migration of crustal materials, magma transportation, and continental deformation in the Lhasa terrane. The model shows resistive features in the south that may represent the Indian plate, and conductive features above this that may represent the migration of materials beneath the Lhasa terrane, both of which vary substantially along the Indus‐Yarlung Zangbo suture. In the mid‐lower crust, conductive features (with a likely corresponding decrease of the effective viscosity) may be related to underplating, magma reservoirs, mineralization sources, and vertical motion of buoyant materials. A weakened mid‐lower crust has consequences for surface deformation and may have contributed to the formation of (north‐south) rift zones. Furthermore, the inhomogeneous distribution of weakened areas in the mid‐lower crust has implications for the local lateral migration of materials. There is considerable debate over the structure and dynamic processes beneath the Lhasa‐Gangdese terrane. To explore this region, variations of the electric and magnetic fields at 537 measurement locations across an array were used to generate the electrical resistivity structure in three‐dimensional. Based on the electrical structure, the volume and distribution of melt are estimated and the corresponding decrease of the effective viscosity is constrained in the mid‐lower crust. These results can help to understand the development and formation of this region and have important implications for open questions. In the south, differences in the E‐W direction may indicate a variable geometry of the underthrust Indian Plate and the southern extrusion of materials beneath the Lhasa terrane. Conductive features with high melt fraction and low viscosity in the mid‐lower crust may result from underplating, and may have contributed to past magmatic activities. Furthermore, the variation in rheology may also contribute to the surface deformation and the formation of N‐S rifts. In some areas, the weak zones in the mid‐lower crust appear to be discontinuous, and thus there are implications for the local flow of material. We present a scheme in which separate high‐resolution 3‐D electrical resistivity models are generated and combined into a continuous modelThe distribution of partial melt is estimated throughout the crust of the Lhasa terrane, with implications for rheologyEvidence for an uneven distribution of melt along the Indian plate has implications for material migration and distinct dynamic processes We present a scheme in which separate high‐resolution 3‐D electrical resistivity models are generated and combined into a continuous model The distribution of partial melt is estimated throughout the crust of the Lhasa terrane, with implications for rheology Evidence for an uneven distribution of melt along the Indian plate has implications for material migration and distinct dynamic processes

The creation and evolution of the Songliao Block, Northeast China, is believed to be related to the closure of the Paleo‐Asian and Mongol‐Okhotsk oceans, and to the subduction of the Paleo‐Pacific Ocean. Geochemical and geophysical data indicate a complex tectonic history that may have left signatures of the superposition of separate tectonic events. However, the relationship between the current lithospheric structure of the Songliao Block and those tectonic events is not clear. In order to shed light on this question, a three‐dimensional electrical resistivity model of the crust and mantle was generated from 138 magnetotelluric sites. The results show a heterogenous lithosphere with anomalous low‐resistivity zones (∼10 Ω·m). The position of upper‐crustal features (<10 km) correlates with a network of fault systems and rift basins. Based on estimates of high crustal temperatures, mid‐lower crustal features (15–35 km), some of which appear near seismic reflectors, are attributed to partial melts (∼5%) containing moderate‐high water contents (4.5 wt. %). A deep (>45 km) feature is interpreted as an asthenospheric upwelling near the center of the Songliao Block, where seismic evidence indicates a thin lithosphere. It is proposed that the collision, convergence, and suturing of blocks caused by the closure of the Paleo‐Asian Ocean and the bidirectional convergence between the Mongol‐Okhotsk and Paleo‐Pacific Ocean may have produced weak tectonic zones throughout the lithosphere. They provided a structural basis for the later upward movement of fluids and melt, likely due to hydrous upwellings caused by the subduction of the Paleo‐Pacific system. The Songliao Block, Northeast China, which contains the Songliao Basin region that is rich in energy resources, is known to have a complex history of formation. In order to understand the influence of the surrounding tectonic environment on the Songliao Block, we collected magnetotelluric measurements, which can determine the electrical properties of underground structures. These measurements allowed us to build a three‐dimensional electrical resistivity model, to depths of 60 km, in the north of the Songliao Block. Analysis of the model showed various low‐resistivity features with different explanations: upper‐crustal features correlated with a network of fault systems and rift basins; mid‐lower crustal features were attributed to melts; a deep feature was interpreted to be a mantle upwelling near the center of the Songliao Block. Combined with evidence from other geophysical and geological studies, we proposed that the superposition of past tectonic systems may have produced weak tectonic zones and increased subsurface heating. The deep structure of the Songliao block is important to understand because it can help to track the source of energy resources and facilitate the development of energy exploration. A 3‐D electrical resistivity model of the subsurface beneath the northern Songliao Block was generated from 138 magnetotelluric sitesLow‐resistivity features are attributed to rift and fault systems, mid‐lower crustal partial melts, and an asthenospheric upwellingPast tectonic events, for example, collisions of blocks due to ocean closures, may have produced weak zones allowing for the ascent of melt A 3‐D electrical resistivity model of the subsurface beneath the northern Songliao Block was generated from 138 magnetotelluric sites Low‐resistivity features are attributed to rift and fault systems, mid‐lower crustal partial melts, and an asthenospheric upwelling Past tectonic events, for example, collisions of blocks due to ocean closures, may have produced weak zones allowing for the ascent of melt

The Xainza‐Dinggye rift, an approximately north‐south trending Cenozoic fault zone across the Lhasa Terrane, is an ideal location to investigate extensional mechanisms in the upper crust and lithospheric deformation caused by the subducting Indian Plate beneath the central‐southern Tibetan Plateau. The 3‐D electrical resistivity structure was obtained by modeling magnetotelluric data from an array across the rift zone. Using the temperature distribution throughout the crust combined with the pressure and water content, we compute the pure melt conductivity. This enables estimation of the partial melt fraction of large‐area conductive zones imaged throughout the crust, and thus allows their rheology and strength to be evaluated. The heterogeneous distribution of high melt fraction areas in the crust has implications for the local continuous migration of fluids in the east‐west direction. The electrical structure also reveals a dipping resistive zone beneath the Tethys‐Himalaya terrane that represents the subducted Indian Plate. Significantly, its depth is observed to vary substantially from east (deeper) to west (shallower), which may indicate tearing of the plate. We suggest that the cause of extension and the formation of the crustal rift zone is related to tearing of the plate directly below this location, and the subsequent partial melting of the mid‐lower crust. Furthermore, the ascent of deep hydrothermal fluids, and heating of the shallow subsurface, likely led to the formation of the congruent Xainza‐Dinggye Thermal Belt. Additionally, the emplacement of numerous adjacent magmatic‐hydrothermal ore deposits is also likely related to partial melting and hydrothermal fluid migration in the crust. The Xainza‐Dinggye rift is a north‐south trending fault in the central‐southern Tibetan Plateau. The 3‐D electrical structure is imaged using the magnetotelluric method, which uses natural electromagnetic signals to measure the subsurface electrical resistivity structure and is particularly sensitive to the presence of fluids and partial melts. The resulting model shows resistive regions beneath the Tethys‐Himalaya terrane that represent the subducted Indian plate. Several conductors in the mid‐lower crust may be related to partial melting. With the constraints of the temperature, pressure and water content, estimates of pure melt conductivity were obtained. This analysis is used to evaluate the strength characteristic of the mid‐lower crust. The results show that the formation and scale of the rift‐zone is likely caused by subduction features of the Indian plate (e.g., tearing of the plate) and the deformation characteristic of the mid‐lower crust (e.g., partial melting). Additionally, the rise of hot materials and fluids may have heated the circulating system of underground water and led to the formation of the Xainza‐Dinggye thermal belt and the formation of widespread hot springs. This work provides critical constraints for southward extrusion along the Main Himalaya Thrust and for possible conditions of east‐west fluid migration. 3‐D electrical resistivity model used to constrain crustal melt fraction using experimentally derived estimates of pure melt resistivityHeterogeneous distribution of melt zones has implications for the possible east‐west migration of fluid along the Indian Plate below TibetTearing of the plate (East part steeper) and melting of the mid‐lower crust caused congruent rifting, thermal springs, and ore districts 3‐D electrical resistivity model used to constrain crustal melt fraction using experimentally derived estimates of pure melt resistivity Heterogeneous distribution of melt zones has implications for the possible east‐west migration of fluid along the Indian Plate below Tibet Tearing of the plate (East part steeper) and melting of the mid‐lower crust caused congruent rifting, thermal springs, and ore districts

Intraplate surface deformation is enigmatic and the underlying mechanisms responsible are not fully understood. We use thermo‐mechanical numerical modeling to explore the conditions under which lithospheric removal processes can occur and investigate the timing and amplitude of consequent surface deformation. We allow lithospheric removal to develop dynamically and self‐consistently by applying a phase transition and density jump that is hypothesized to be a consequence of metamorphic eclogitization in a thickened crust, rather than simply imposing an initial dense block. By systematically varying parameters, we test their influence and control on lithospheric removal. We confirm that a weak and dense lower crust, a hot crust‐mantle boundary, and a convergent regime are critical requirements for delamination‐style removal. We apply these results to central Mongolia, which is an ideal natural laboratory for studying intraplate surface uplift because of its high topography and location in the continental interior. We determine that the physical parameters and structure inferred in this region match the conditions for delamination. Thus, model outputs are evaluated against the available observational evidence. We find that the removal of the lithosphere by delamination can explain: the dome‐shaped topographic pattern and elevated surface; the thin lithosphere and its structure; the elevated temperature at the crust‐mantle boundary. Additionally, it is hypothesized that delamination leads to magmatism due to mantle decompression melting, consistent with intraplate volcanism. Ultimately, the results suggest that lithospheric removal by delamination is a physically plausible mechanism and a potential explanation for intraplate uplift. Conditions for lithospheric removal‐induced surface deformation are investigated and applied to intraplate uplift in central MongoliaA weak and dense lower crust (modeled with a phase transition to eclogite) and convergent motion are required for removal by delaminationModel outputs—topography, lithospheric structure, timing—match observational evidence, suggesting a physically plausible mechanism Conditions for lithospheric removal‐induced surface deformation are investigated and applied to intraplate uplift in central Mongolia A weak and dense lower crust (modeled with a phase transition to eclogite) and convergent motion are required for removal by delamination Model outputs—topography, lithospheric structure, timing—match observational evidence, suggesting a physically plausible mechanism