Search Results (84)

The SE Baltic area, the former Eastern Prussia, is renowned for complex natural history. Over the past millions of years, the area experienced major geological events and geomorphic landscape transformations, resulting in the present relief configuration. Past climates and environments gave rise to the specific life-forms that proliferated in the Paleozoic and Mesozoic–Early Cenozoic shallow sea/lacustrine basins, and the Late Cenozoic riverine and continental settings. During the Paleogene, forested sub-tropical lands and deltaic settings of coastal sea lagoons gave rise to the famed amber formations (Blue Ground) hosting inclusions of resin-sealed insect and other small invertebrates that offer an unprecedented look into the 35–34 million-year habitats. Ferruginous sandstones, formed in shallow waters incorporating remains of thermophilous fauna—bivalves and gastropods, bryozoans, and sea urchins, among others—lie above the amber-bearing deposits. Oligocene–Miocene continental (riverine, lacustrine, and palustrine) conditions relate to the “Brown Coal Formation”, embedding a variety of fossil plants. Finally, the Quaternary Period brought dramatic geo-environmental shifts, with cyclic interstadial sea transgressions and massive glacial erosion events delivering fossiliferous erratics with an array of primitive Paleozoic and later Mesozoic life-forms. Overall, the extraordinary paleontology of the SE Baltic area adds, within its geological context, to the European geoheritage and the world natural heritage. Full article

The Hongche Fault Zone in the Junggar Basin exhibits significant spatiotemporal variations in the relationship between fault systems and hydrocarbon accumulation across different structural belts. Two key factors contribute to this phenomenon: frequent tectonic activities and well-developed Paleozoic fault systems. To date, no detailed studies have been conducted on the fault systems in the Paleozoic strata of the Hongche Fault Zone. In this study, the fault systems in the Paleozoic strata of the Hongche Fault Zone were systematically sorted out for the first time. Furthermore, the controlling effects of active faults in different geological periods on hydrocarbon charging were clarified. Firstly, basing on the 3D seismic and well-log data, the structural framework and fault activity, fault systems, source-contacting faults were characterized. Vertically, the Hongche Fault Zone experienced three major thrusting episodes followed by one weak extensional subsidence Stage, forming four principal tectonic layers: Permian (Thrusting Episode I), Triassic (Thrusting Episode II), Jurassic (Thrusting Episode III), and Cretaceous–Quaternary (Post-Thrusting Subsidence). Laterally, six fault systems are identified: Middle Permian (Stage I), Late Triassic (Stage II), Jurassic (Stage III), post-Cretaceous (Stage IV), as well as composite systems from Middle Permian–Jurassic (Stages I–III) and Late Triassic–Jurassic (Stages II–III). These reveal multi-stage, multi-directional composite structural characteristics in the study area. According to the oil–source correlation, the Carboniferous reservoir is primarily sourced by Permian Fengcheng Formation source rocks in the Shawan Sag. Hydrocarbon migration tracing shows that oil migrates along faults, progressively charging from depression zones to thrust belts and uplifted areas. In this process, fault systems exert hierarchical controls on accumulation: Stage I faults dominate trap formation, Stages II and III faults regulate hydrocarbon migration, accumulation, and adjustment, while Stage IV faults influence hydrocarbon conduction in Mesozoic–Cenozoic reservoirs. By clarifying the fault-controlled hydrocarbon accumulation mechanisms in the Hongche Fault Zone, this study provides theoretical guidance for two key aspects of the Carboniferous reservoirs in the study area: the optimization of favorable exploration zones and the development of reserves. Full article

Three new species—Enneoxyela aculeata sp. nov., Enneoxyela eucalla sp. nov., and Hemixyela elongata gen. et sp. nov.—are described and illustrated from the Lower Cretaceous Yixian Formation at Huangbanjigou, Liaoning Province, China. Meanwhile, two new genera are established by the species previously described after re-examination, Tugnuxyela gen. nov. based on T. tugnuica comb. nov. (Rasnitsyn, 1982), from the Lower Jurassic of Transbaikalian in Russia, and Junfengixyela gen. nov. based on J. cenozoica comb. nov. (Zhang, 1989) from the Miocene of Shandong in E. China. This is the first occurrence of the tribe Xyelini in the Cretaceous of China. A male specimen is described for the first time in Mesozoic Xyelini; it is found sufficiently similar to the known (Cenozoic) males of the tribe, including the genitalia twisted for 180°. Keys to the genera of Xyelini and to the species of Enneoxyela are provided. Full article

The Dingri–Gangba fault, a major structure within the Himalayan Orogenic Belt, records significant geological events, including the tectonic evolution of the northern margin of the Indian plate and the uplift of the Tibetan Plateau. However, its geometry, kinematics, and tectonic characteristics remain debated. To constrain the tectonic evolution of the Dingri–Gangba fault, this study integrates detailed field investigations and structural analysis with Electron Spin Resonance (ESR) dating to characterize its three-dimensional architecture and quantify the timing of its deformation phases. The results show that the fault trends nearly E–W and exhibits multi-phase structural superimposition, including thrusting (60–40 Ma), normal faulting (35–11 Ma), and strike-slip shear (18–6.8 Ma). These phases reflect a multi-stage tectonic evolution following the India–Eurasia collision. Stratigraphic comparisons reveal that during the Mesozoic, the Dingri–Gangba fault played a significant basin-controlling role, marked by variations in sedimentary thickness, soft-sediment deformation, and volcanic activity. The sedimentary evolution alternated between periods of “differentiation” and “uniformity”. A comprehensive analysis suggests that the tectonic evolution of the Dingri–Gangba fault is closely linked to the dynamic transition of the Tethys Himalaya from a passive continental margin to a collision orogeny, also reflecting changes in the tectonic stress field following the India–Eurasia collision. These findings provide valuable insights into the tectono–sedimentary–magmatic coupling along the southern margin of the Tibetan Plateau. Full article

Research on the Mesozoic–Cenozoic magmatism and the tectonic framework within the Lhasa Terrane is voluminous. However, the sparse documentation of Early Cretaceous magmatism in this region fuels ongoing debate over the prevailing tectonic regime during this time period (i.e., normal subduction vs. flat subduction). The present study investigates the Luerma pyroxenite and Boyun granitoid in the Western Lhasa Terrane through zircon U-Pb dating, whole-rock geochemistry, mineral chemistry, and Sr-Nd-Hf isotopes. The findings date the formation of Luerma pyroxenite at 115 Ma and Boyun granites at 113 Ma to the Early Cretaceous period (115–113 Ma). SiO₂ content of pyroxenite is relatively low (34.27–44.16 wt.%), characterized by an enrichment in large ion lithophile elements (LILEs), light rare earth elements (LREEs), and a depletion in heavy field strength elements (HSFEs), indicative of a metasomatic origin. The εNd (t) and εHf (t) values of the Early Cretaceous ultrabasic rocks range from +2.1 to +2.7 and −0.8 to +10.1, respectively, suggesting their derivation from an enriched mantle source with asthenospheric material incorporation. The Early Cretaceous granodiorites and their mafic enclaves belong to the high-K calc-alkaline series, and show enrichment in LILEs (e.g., Rb, Ba, U, and Th) and depletion in HFSEs (e.g., Nb, Ta, Ti, and Zr). The acidic rocks and their developed mafic enclaves exhibit the geochemical characteristics of trace elements found in island arc magmas. Their εNd (t) values are (−6.0–−5.0), while their εHf (t) values are (−11.7–−1.8); the MMEs εHf (t) values are (−4.1–+0.9). In summary, the Early Cretaceous pyroxenite in the Gangdese Belt originated from a combination of asthenospheric and enriched lithospheric mantle melts, while the granitoids were generated by partial melting of the mantle wedge, a process driven by metasomatism resulting from the slab-derived fluids. At the same time, heat from upwelling mantle-derived melts induced the partial melting of lower crustal materials, leading to the formation of acidic magmas through varying degrees of mixing with basic magmas. This study suggests that Early Cretaceous magmatic activity occurred within a northward subduction setting, characterized by the rotation and fragmentation of the Neo-Tethys oceanic crust. Full article

The distribution and quality of the Lower Cretaceous reservoir sandstone units of the Mesozoic–Cenozoic Scotian Basin, offshore eastern Canada, is well known in producing fields but difficult to extrapolate to less-explored areas of the deep-basin floor. Prediction of reservoir risk is complicated by salt tectonism and the strong influence of diagenesis on reservoir quality. This study investigates the burial diagenetic dissolution of detrital K-feldspar in the subarkosic sandstones and the preservation of the resulting secondary porosity. K-feldspar abundance declines with increasing depth, creating secondary porosity, which in open systems is preserved but in closed systems is clogged by carbonates and clays. The distribution of detrital K-feldspar has been simulated using forward stratigraphic modeling and is compared to thermal modeling, fault mapping, and sand distribution to determine the risk due to the reservoir quality, illustrated as common risk segment maps. Sand deposits have the lowest risk of poor reservoir quality along the shelf edge and upper slope of the central and western basin, where growth faulting created an open diagenetic system. This novel combination of petrographic study and forward modeling has applications to other regions where diagenesis has a strong influence on the reservoir quality, such as the Gulf of Mexico. Full article

The East China Sea Shelf Basin (ECSSB) and its adjacent areas, as key regions of the ocean–continent transition zone, have been affected by multiple complex plate collisions, subduction, and back-arc tension since the Mesozoic Era. The structural deformation provides a large amount of geological information on the ocean–continent transition zone. There are significant spatiotemporal differences in the structural deformation within the basin. However, the research remains insufficient and understanding is inconsistent, especially regarding the systematic study of the differences and dynamic mechanisms of north–south structural deformation, which is relatively lacking. This study is based on two-dimensional multi-channel deep reflection seismic profiles spanning the southern and northern basin. Through an integrated re-analysis of gravity, magnetic, and OBS data, the deformation characteristics and processes of the Meso-Cenozoic structures in the basin are analyzed. The differences in structural deformation between the southern and northern basin are summarized, and the controlling effects of deep crust–mantle activity and the influencing factors of shallow structural deformation are explored. Based on deep reflection seismic profiles, the structural deformation characteristics of the Yushan–Kume fault are revealed for the first time, and it is proposed that NW faults, represented by the Yushan–Kume fault, have important tuning effects on the north–south structural differential deformation in the ECSSB. The thermal subsidence of the lithosphere is the direct cause of the development of the Mesozoic ECSSB, while the subduction of the Paleo-Pacific plate is one of the important factors contributing to it. The combined effect of the two has led to significant differences between the northern and southern Mesozoic basin. During the Cenozoic Era, the alternating subduction and changes in the direction of subduction of the Pacific Plate led to spatiotemporal differences in structural deformation within the ECSSB. The development of NW faults was a key factor in the differences in structural deformation between the northern and southern basin. The study of structural deformation differences in the ECSSB not only deepens our understanding of the tectonic evolution in the East Asian continental margin region, but also has important significance for the exploration and evaluation of deep hydrocarbon resources in the ECSSB. Full article

This study investigates the uplift and exhumation history of the southern segment of the western margin of the Ordos Basin using low-temperature thermochronology, including zircon (U-Th)/He (ZHe), apatite fission-track (AFT), and apatite (U-Th)/He (AHe) data, combined with thermal history modeling. The study area exhibits a complex structural framework shaped by multiple deformation events, leading to the formation of extensively developed fault systems. Such faulting can adversely affect hydrocarbon preservation. To better constrain the timing of fault reactivation in this area, we carried out an integrated study involving low-temperature thermochronology and burial history modeling. The results reveal a complex, multi-phase thermal-tectonic evolution since the Late Paleozoic. The ZHe ages (291–410 Ma) indicate deep burial and heating related to Late Devonian–Early Permian tectonism and basin sedimentation, reflecting early orogenic activity along the western North China Craton. During the Late Jurassic to Early Cretaceous (165–120 Ma), the study area experienced widespread and differential uplift and cooling, controlled by the Yanshanian Orogeny. Samples on the western side of the fault show earlier and more rapid cooling than those on the eastern side, suggesting a fault-controlled, basinward-propagating exhumation pattern. The cooling period indicated by AHe data and thermal models reflects the Cenozoic uplift, likely induced by far-field compression from the rising northeastern Tibetan Plateau. These findings emphasize the critical role of inherited faults not only as thermal-tectonic boundaries during the Mesozoic but also as a pathway for hydrocarbon migration. Meanwhile, thermal history models based on borehole data further reveal that the study area underwent prolonged burial and heating during the Mesozoic, reaching peak temperatures for hydrocarbon generation in the Late Jurassic. The timing of major cooling events corresponds to the main stages of hydrocarbon expulsion and migration. In particular, the differential uplift since the Mesozoic created structural traps and migration pathways that likely facilitated hydrocarbon accumulation along the western fault zones. The spatial and temporal differences among the samples underscore the structural segmentation and dynamic response of the continental interior to both regional and far-field tectonic forces, while also providing crucial constraints on the petroleum system evolution in this tectonically complex region. Full article

Recent updates to the reconstructions of Cenozoic environmental changes (global sea level, temperature, and atmospheric carbon dioxide content) have made it intriguing to compare them to paleontological records for original interpretations. Paleogene brachiopods have remained in the shadow of their Paleozoic–Mesozoic predecessors, and the reactions of their diversity to the Earth’s dramatic changes are poorly understood. The present work aims to fill this gap via a comparison of several diversity and paleoenvironmental curves. The generic diversity was established by stages with two essentially different paleontological datasets, and several fresh paleoenvironmental reconstructions were adopted. It was observed that neither Paleogene eustatic fluctuations nor changes in the atmospheric carbon dioxide content correspond well to the generic diversity dynamics of brachiopods. The changes in the total number of genera and the global temperatures demonstrate similarity at the Danian–Ypresian interval, but not later. The fluctuations in the brachiopod diversity are near the same level during the Eocene–Oligocene, despite strong paleoenvironmental changes, implying the intrinsic resistivity of these organisms to external influences. Additionally, the Cretaceous/Paleogene mass extinction, the Paleocene–Eocene thermal maximum, and the Early Eocene optimum could enhance the diversity dynamics together with the long-term temperature changes. In contrast, the influences of the Late Danian warming event and the Oi-1 glaciation were not observed. Full article

The Qiangtang Basin (Tibetan Plateau) poses significant geophysical challenges for seismic exploration due to near-surface widespread permafrost and steeply dipping Mesozoic strata induced by the Cenozoic Indo-Eurasian collision. These seismic geological conditions considerably contribute to lower signal-to-noise ratios (SNRs) with complex wavefields, to some extent reducing the reliability of conventional seismic imaging and structural interpretation. To address this, the common-reflection-surface (CRS) stack method, derived from optical paraxial ray theory, is implemented to transcend horizontal layer model constraints, offering substantial improvements in high-SNR prestack gather generation and prestack depth migration (PSDM) imaging, notably for permafrost zones. Using 2D seismic data from the basin, we detailedly compare the CRS stack with conventional SNR enhancement techniques—common midpoint (CMP) FlexBinning, prestack random noise attenuation (PreRNA), and dip moveout (DMO)—evaluating both theoretical foundations and practical performance. The result reveals that CRS-processed prestack gathers yield superior SNR optimization and signal preservation, enabling more robust PSDM velocity model building, while comparative imaging demonstrates enhanced diffraction energy—particularly at medium (20–40%) and long (40–60%) offsets—critical for resolving faults and stratigraphic discontinuities in PSDM. This integrated validation establishes CRS stacking as an effective preprocessing foundation for the depth-domain imaging of complex permafrost geology, providing critical improvements in seismic structural resolution and reduced interpretation uncertainty for hydrocarbon exploration in permafrost-bearing basins. Full article

The Chaoshan Depression, situated in the northern South China Sea, is a Mesozoic residual depression beneath the Cenozoic Pearl River Mouth Basin. Borehole LF35-1-1 has confirmed the existence of marine Jurassic layers rich in organic carbon within this depression. However, the understanding of petroleum geology in this area is limited due to the complex interplay of Mesozoic and Cenozoic tectonic activities and the poor quality of seismic imaging from previous surveys, which have obstructed insights into the characteristics of Mesozoic reservoirs and the processes of oil and gas accumulation. Recent quasi-3D seismic data have allowed for the identification of Mesozoic bioherms and carbonate platforms in the Middle Low Uplift of the Chaoshan Depression. This research employs integrated geophysical data (MCS, gravity, magnetic) and well data to explore the factors that influenced Middle Jurassic reef development and their implications for reservoir formation. The seismic reflection patterns of reefs and carbonate platforms are primarily characterized by high-amplitude discontinuous to chaotic reflections, with occasional blank reflections or weak, sub-parallel reflections, as well as significant high-velocity, high Bouguer gravity and low reduced-to-pole (RTP) magnetic anomalies. Atolls, stratiform reefs, and patch reefs are located on the local topographic highs of the platform. Three vertical evolutionary stages have been identified based on the size of atolls and fluctuations in relative sea level: initiation, growth, and submergence. The location of bioherms and carbonate platforms was influenced by paleotectonic topography, while their horizontal distribution was affected by variations in relative sea level. Furthermore, the reef limestone reservoirs from the upper member of the Middle Jurassic, combined with the mudstone source rocks from the Lower Jurassic and the lower section of the Middle Jurassic, as well as the bathyal mudstone caprocks from the lower part of the Late Jurassic, create highly favorable conditions for hydrocarbon accumulation. Full article

The Cenozoic Nankang Basin in China records a complex series of tectonic, magmatic, metamorphic, and sedimentary events associated with the surrounding Shiwanshan, Liuwanshan, and Yunkaishan orogenic systems. The Nankang Basin is a critical location for studying the Cenozoic tectono–sedimentary evolution and strategic mineral resources of the southern Cathaysia Block. We used core samples from multiple boreholes and regional geological survey data to analyze the rock assemblages, sediment types, and sedimentary facies of the Nankang Basin. In addition, we analyzed the detrital zircon U–Pb geochronology, sandstone detrital compositions, heavy mineral assemblages, and major element geochemistry. The detrital zircon grains from Cenozoic sandstones in the Nankang Basin have age peaks at 2500–2000, 1100–900, 500–400, and 300–200 Ma, with most grains having ages of 500–400 or 300–200 Ma. The provenance analysis indicates that the 300–200 Ma zircon grains originated mainly from the Liuwanshan pluton; the 500–400 Ma zircon grains originated from the Ningtan pluton; and the 2500–2000 and 1100–900 Ma zircon grains originated from the Lower Silurian Liantan Formation and Middle Devonian Xindu Formation. This indicates that the provenance of Cenozoic sandstones in the Nankang Basin primarily originates from Paleozoic–Early Mesozoic igneous in the surrounding area, while the regional old sedimentary rocks possibly serve as intermediate sedimentary reservoirs. The detrital compositions of the sandstones and heavy mineral assemblages indicate a change in the tectonic setting during the deposition of the Nankang and Zhanjiang Formations, with a change in the source of the sediments due to the uplift of the Shizishan. During the deposition of the Nankang Formation, the sediment transport direction was to the NNW, whereas during the deposition of the Zhanjiang Formation, it was to the NNE. The uplift of the Shizishan most probably occurred during the late Neogene and early Quaternary, separating the Hepu and Nankang Basins. Full article

The southwestern region of China is tectonically situated within the Tethyan tectonic domain, with the eastern part comprising the Upper Yangtze Block, while the western orogenic belt forms the main part of the Tibetan Plateau. This belt was formed by the subduction of the Paleo-Tethys Ocean and subsequent arc-continent collision, and was later further modified by the India-Asia collision, resulting in complex geological structures such as the Hengduan Mountains. The lithostratigraphy in this region can be divided into six independent units. In terms of mineralization, the area encompasses two first-order metallogenic domains: the Tethyan-Himalayan and the Circum-Pacific. This study synthesizes extensive previous research to systematically investigate representative rare earth element (REE) deposits (e.g., Muchuan and Maoniuping in Sichuan; the Xinhua deposit in Guizhou; the Lincang deposit in Yunnan). Through comparative analysis of regional tectonic-metallogenic settings, we demonstrate that REE distribution in Southwest China is fundamentally controlled by Tethyan tectonic evolution: sedimentary-weathered types dominate in the east, while orogenic magmatism-related types prevail in the west. These findings reveal critical metallogenic patterns, establishing a foundation for cross-regional resource assessment and exploration targeting. The region hosts 32 identified REE occurrences, predominantly light REE (LREE)-enriched, genetically classified as endogenic, exogenic, and metamorphic deposit types. Metallogenic epochs include Precambrian, Paleozoic, and Mesozoic-Cenozoic periods, with the latter being most REE-relevant. Six prospective exploration areas are delineated: Mianning-Dechang, Weining-Zhijin, Long’an, Simao Adebo, Shuiqiao, and the eastern Yunnan-western Guizhou sedimentary-type district. Notably, the discovery of paleo-weathering crust-sedimentary-clay type REE deposits in eastern Yunnan-western Guizhou significantly expands regional exploration potential, opening new avenues for future resource development. Full article

Recent exploration efforts in the Qiongdongnan Basin have revealed hydrocarbon resources within granitic basement rocks in buried hill traps. However, the formation mechanisms and primary controlling factors of these reservoirs remain poorly understood. In this study, we utilized data from six wells in the Qiongdongnan Basin, including sidewall cores, thin sections, imaging logging, and seismic reflection profiles, to analyze the petrological characteristics, pore systems, and fracture networks of the deep basement reservoir. The aim of our study was to elucidate the reservoir formation mechanisms and identify the key controlling factors. The results indicate that the basement lithology is predominantly granitoid, intruded during the late Permian to Triassic. These rocks are characterized by high felsic mineral content (exceeding 90% on average), with them possessing favorable brittleness and solubility properties. Fractures identified from sidewall cores and interpreted from image logging can be categorized into two main groups: (1) NE-SW trending conjugate shear fractures with sharp dip angles and (2) NW-SE trending conjugate shear fractures with sharp angles. An integrated analysis of regional tectonic stress fields suggests that the NE-trending fractures and associated faults were formed by compressional stresses related to the Indosinian closure of the ancient Tethys Ocean. In contrast, the NW-trending fractures and related faults resulted from southeast-directed compressional stresses during the Yanshanian subduction event. During the subsequent Cenozoic extensional phase, these fractures were reactivated, creating effective storage spaces for hydrocarbons. The presence of calcite and siliceous veins within the reservoir indicates the influence of meteoric water and magmatic–hydrothermal fluid activities. Meteoric water weathering exerted a depth-dependent dissolution effect on feldspathoid minerals, leading to the formation of fracture-related pores near the top of the buried hill trap during the Mesozoic exposure period. Consequently, the combination of high-density fractures and dissolution pores forms a vertically layered reservoir within the buried hill trap. The distribution of potential hydrocarbon targets in the granitic basement is closely linked to the surrounding tectonic framework. Full article

The water contents and geochemical evidence of nominally anhydrous minerals in peridotite xenoliths provide critical insights into lithospheric mantle features, offering a deep understanding of cratonic destruction and mantle evolution processes. Damaping, located in the central part of the intra-North China Craton, hosts abundant mantle peridotite xenoliths’ samples, providing new constraints on lithospheric mantle evolution. In this study, spinel lherzolite samples from Damaping Cenozoic basalts were analyzed for major and trace elements, water content, and oxygen isotope to investigate the factors controlling mantle water distribution and lithospheric mantle modification. The olivines of Damaping spinel lherzolite have a range of Mg# values from 89.73 to 91.01, indicating moderately refractory mantle characteristics. Clinopyroxenes display an LREE-depleted pattern, suggesting a consistency with 1–6% of batch partial melting and 1–5% fractional partial melting. The high (La/Yb)_N (0.20–0.73) and low Ti/Eu (3546.98–5919.48) ratios of Damaping clinopyroxenes reveal that the lithosphere mantle beneath the Damaping has undergone silicate metasomatism. The water contents of Damaping clinopyroxenes and orthopyroxenes range from 13.39 to 19.46 ppm and 4.60 to 7.82 ppm, respectively. The water contents of the olivines are below the detection limit (<2 ppm). The whole-rock water contents can be estimated based on the mineral modes and partition coefficients, with values ranging from 3.21 to 5.44 ppm. Partial melting indicators (Mg# in Ol and Yb_n in Cpx) correlate with the water content in clinopyroxenes and orthopyroxenes but show no correlation with the redox state (Fe³⁺/∑Fe ratios in spinel) or metasomatism ((La/Yb)_N in clinopyroxene). These results suggest that the degree of partial melting primarily controls the heterogeneous water distribution in Damaping spinel lherzolite, rather than the redox state or metasomatism. The δ¹⁸O values of clinopyroxenes from Damaping spinel lherzolites (5.27–5.59‰) fall within the range of mid-ocean ridge basalts (MORB), indicating a mantle source characterized by MORB-like isotopic signatures. The low whole-rock water contents are attributed to lithospheric reheating resulting from asthenospheric upwelling during the Late Mesozoic–Early Cenozoic. Therefore, the lithosphere is predominantly composed of ancient Proterozoic residues, with localized contributions of younger asthenospheric material near deep faults. Full article