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The Canterbury Basin is a portion of the mostly submerged continent of Zealandia that formed along the eastern portion of the Gondwanan front. Based on tectonic subsidence analyses of IODP Expedition 317 boreholes and Clipper-1 well data, we argue for a rapid subsidence event (∼84 Ma to ∼76 Ma) which we interpret as transit away from a region of mantle upwelling. Breakup was followed by thermal subsidence between 76 Ma and 20 or 10 Ma. Sea-level estimates based on our data are consistent with eustatic estimates in the literature between 76 and 30 Ma. From about 7 Ma to 3.8 Ma, there is evidence that over a kilometre of uplift could have occurred within the basin. This uplift event is consistent with earlier suggestions of lower mantle delamination based on local volcanism and the thickness of the lithosphere. Isostatic calculations are consistent with the hypothesis that delamination of some dense mantle lithosphere could account for the uplift seen in our tectonic subsidence analyses. [ABSTRACT FROM AUTHOR]

Adakitic rocks provide important data on Early Cretaceous magmatism and the tectonic setting of the eastern North China Craton. This study reports new data on adakitic alkali rhyolites in the offshore Bohai Bay Basin, eastern China. The eruption age of the rhyolites is represented by a weighted mean206Pb/238U age of 114.4 Ma. The geochemical characteristics of the samples are similar to those of adakitic rocks, with high Sr (307–1686 ppm) and low Y (3.18–11.3 ppm) and Yb (0.30–1.39 ppm) contents, as well as high Sr/Y (40–70) ratios. Moreover, the samples show relatively uniform εNd(t) values (−15.48 to −16.51) and older TDM2 values (2253–2170 Ma). These geochemical features indicate that they were mainly derived from partial melting of the lower continental crust. Amphibole rather than garnet is the main residual phase in the source, indicating that the magma originated from the normal lower crust (<40 km) rather than from the thickened lower crust. Our data, along with regional geology, lead us to suggest that the lithosphere was being stretched and thinned before ca. 114 Ma in the eastern North China Craton, and the region was already under an intraplate tectonic setting associated with a large mantle wedge at ca. 114 Ma. The tectonic regime was triggered by the rollback of the Paleo-Pacific Plate during the late Early Cretaceous. [ABSTRACT FROM AUTHOR]

The lithosphere beneath the eastern part of the North China Craton (NCC) is widely recognized as having undergone extensive thinning and destruction since the Mesozoic. Although most models propose that the destruction was related to the Paleo-Pacific subduction, the timing and mechanism of the destruction remains controversial. The Tanlu Fault is the largest deep strike-slip fault zone in eastern China. It is an ideal object to study the destruction of the NCC and the subduction history of the Paleo-Pacific. In this review, we compile the ages and geochemical data of the Mesozoic magmatic rocks along the Tanlu Fault zone, in combination with evidence related to the tectonic evolution of the Tanlu Fault during this time. We further discuss the relationship between subduction of the Paleo-Pacific and the thinning and destruction processes affecting the NCC lithosphere. In the Late Triassic period, adakitic rocks, A-type granites, and mafic rocks generated from depleted asthenosphere were distributed in Liaoning and Shandong provinces along the Tanlu Fault. These magmas were related to an extensional environment caused by exhumation of the Yangtze block after subduction. The magmatic characteristics indicate that the lithospheric mantle began to change from cold and refractory to a hot and active, suggesting that the NCC began to undergo cratonic destruction at this time. The magmatic lull ranging from 200–185 Ma represents the transition for the Tanlu Fault zone tectonic domain from Paleo-Asian Ocean subduction in the north to the Paleo-Pacific subduction in the east. During the Jurassic, the NCC was also affected by subduction and compression of the Mongol – Okhotsk domain in the north and the influence of the Tethys tectonic domain in the south. Under this multi-directional compression, the crust thickened and the subducted slabs were dehydrated and melted, triggering partial melting of the overlying lithospheric mantle, providing a heat source for partial melting of the crust. At the end of the Jurassic, due to the steepening of the subduction angle of the Paleo-Pacific plate and the roll-back of the plate at that time, another magmatic lull (155–145 Ma) occurred in the Tanlu Fault area. In the early Early Cretaceous, due to a change of the Paleo-Pacific subduction direction (from NW to NNW), a large-scale strike-slip movement took place along the Tanlu Fault zone, and the study area began to experience extensive magmatism. At ca. 125 Ma, A-type granites were formed, representing the large-scale extension. At ca. 122 Ma, OIB-like mafic rocks began to intrude, which indicate that the geochemical properties of the lithospheric mantle of the NCC underwent a fundamental transformation at this time. Hence, the lithospheric mantle of the NCC was replaced by new lithospheric mantle. Slab subduction certainly weakened the NCC. However, the studies of mantle peridotite xenoliths in Cenozoic basalts indicate that the large fault zone (Tanlu Fault) was the priority area for lithospheric mantle transformation and replacement. Taking the time and space distribution characteristics of the NCC destruction into consideration, thermochemical erosion was an indispensable destruction model. According to magmatic and structural evidence, the destruction of the NCC was indeed related to the Paleo-Pacific movement. Besides, it should be noted that the Tanlu Fault was also a factor that cannot be ignored. [ABSTRACT FROM AUTHOR]

The North‐South Gravity Lineament (NSGL), characterized by an abrupt variation in both the Bouguer gravity anomaly and topography, acts as a significant geological boundary in eastern China. The formation of such a lateral feature is believed to be associated with lithospheric thinning. The Songliao Basin (SLB) is considered to mark the centre of the lithospheric thinning in Northeast China, whereas its thinning mechanism remains unclear. Here we perform integrated geophysical‐petrological modelling of the crust and upper mantle structure along a passive‐source seismic profile crossing the NSGL, to understand the thinning mechanism beneath the SLB based on the constructed lithospheric extension and delamination models. Our delamination model identifies the compositional variation across the NSGL and the S‐wave velocity signature dominated by high velocity beneath the SLB, which are compatible with previous geochemical and geophysical results. The multidisciplinary analyses suggest that the lithospheric delamination is a plausible mechanism to account for the thinning to the east of the NSGL. The resulting model also shows that the NSGL is a lithospheric‐scale geophysical and geochemical boundary separating two distinct structural domains. In combination with previous evidence, structural discrepancies across the NSGL can be attributed to the lithospheric delamination driven by the subduction of the Palaeo‐Pacific plate. [ABSTRACT FROM AUTHOR]

Continents with cratonic cores can resist deformation, and thus survive billions of years in the geological record. Tectonic reworking is a significant process that weakens and destructs cratons, but our understanding of the process remains incomplete. In the South China Block, Mesozoic cyclical tectonics destructed a large portion of its cratonic lithosphere. Here, we synthesized the structural evolution of extensional domes and illustrated the process of lithospheric thinning. Unlike the previous rapid, one-cycle delamination model, we propose a newmodel that multicycle compression and extension progressively destructed the lithosphere, which reconciles both surface geology and deep process. [ABSTRACT FROM AUTHOR]

While the western part of northern Tarim Craton has long been considered as a Paleozoic passive margin, a pronounced Silurian‐Devonian magmatism developed on eastern part of this margin may indicate different but active margin setting. In this contribution, detailed structural mapping, petro‐structural analysis, and geochronological investigations were conducted in the Korla area, eastern part of northern Tarim Craton. Three main generations of fabrics were recognized. The earliest pervasive fabric is an originally sub‐horizontal metamorphic S1 foliation that is in part associated with migmatization characterized by high temperature/low pressure metamorphic mineral assemblages, interpreted as reflecting crustal extension. S1 foliation was affected by D2 contraction forming regional‐scale F2 upright folds associated with sub‐vertical axial planar foliation S2. D3 is marked by development of NW‐SE oriented dextral fault, asymmetric mega‐folding of S2 and spaced NW‐SE‐striking S3 foliation, likely in response to dextral transpression. Geochronological data indicate that D1 extension occurred from ca. 420 to 410 Ma, D2 contraction started around 410 Ma and lasted till 400 Ma or later, and D3 transpression was ongoing around ∼370 Ma. Integrated with regional data, an updated geodynamic model is proposed by interpreting the Central Tianshan, South Tianshan and NE Tarim Craton as an early Paleozoic supra‐subduction system. We suggest that the Silurian‐Devonian event reflects thermal softening and horizontal stretching of the supra‐subduction crust, resulting in drifting of the Central Tianshan continental arc from the proto Tarim Craton in association with opening of the South Tianshan back‐arc basin in‐between. Key Points: NE Tarim Craton formed a sub‐horizontal HT/LP foliation in response to crustal extension in the late Silurian‐early DevonianThinned and thermally softened northern Tarim margin was affected by middle Devonian shorteningEarly Paleozoic northern Tarim, South Tianshan, and Central Tianshan evolved into one supra‐subduction environment [ABSTRACT FROM AUTHOR]

Plate tectonics was originally established as a kinematic theory of global tectonics, in which the Earth's rigid outer layer, the lithosphere, consists of different size plates that move relative to each other along divergent, convergent or transform boundaries overlying the ductile asthenosphere. It comprises three elements: rigid lithosphere plates, ductile asthenosphere, and coupled movement systems. It operates through the interlinked processes of continental drift, seafloor spreading and lithospheric subduction, resulting in the generation, modification and demise of lithospheres throughout geological time. The system of lithospheric plates in horizontal and vertical movements forms the spatiotemporal linkages of matter and energy between the surface and interior of Earth, advancing the kinematic theory with a dynamic explanation. While top-down tectonics through lithospheric subduction plays a key role in the operation of plate tectonics, it is balanced for the conservation of both mass and momentum on the spherical Earth by bottom-up tectonics through asthenospheric upwelling to yield seafloor spreading after continental breakup. The gravity-driven subduction of cool lithosphere proceeds through convergence between two plates on one side, and rollback of the subducting slab makes the vacancy for upwelling of the hotter asthenosphere to form active rifting in backarc sites. Plate convergence is coupled with plate divergence between two plates along mid-ocean ridges on the other side, inducing passive rifting for seafloor spreading as a remote effect. Thus, plate tectonics is recognizable in rock records produced by tectonic processes along divergent and convergent plate margins. Although the asthenospheric upwelling along fossil suture zones may result in continental breakup, seafloor spreading is only induced by gravitational pull of the subducting oceanic slab on the remote side. Therefore, the onset and operation of plate tectonics are associated with a series of plate divergent-convergent coupling systems, and they are critically dependent on whether both construction and destruction of plates would have achieved and maintained the conservation of both mass and momentum on the spherical Earth. Plate margins experience different types of deformation, metamorphism and magmatism during their divergence, convergence or strike-slip, leaving various geological records in the interior of continental plates. After plate convergence, the thickened lithosphere along fossil suture zones in intracontinental regions may be thinned by foundering. This causes the asthenospheric upwelling to reactivate the thinned lithosphere, resulting in superimposition and modification of the geological record at previous plate margins. The operation of plate tectonics, likely since the Eoarchean, has led to heat loss at plate margins and secular cooling of the mantle, resulting in the decrease of geothermal gradients and the increase of rheological strength at convergent plate margins. Modern plate tectonics is characterized by the predominance of rigid plate margins for cold subduction, and it has prevailed through the Phanerozoic. In contrast, ancient plate tectonics, that prevailed in the Archean and Proterozoic, is dominated by relatively ductile plate margins for collisional thickening at forearc depths and then warm subduction to subarc depths. In either period, the plate divergence after lithospheric breakup must be coupled with the plate convergence in both time and space, otherwise it is impossible for the operation of plate tectonics. In this context, the creation and maintenance of plate divergent-convergent coupling systems are responsible for the onset and operation of plate tectonics, respectively. Although a global network of mobile belts is common between major plates on modern Earth, it is difficult to find its geological record on early Earth if microplates would prevail at that time. In either case, it is important to identify different types of the geological record on Earth in order to discriminate between the different styles of plate tectonics in different periods of geological history. [ABSTRACT FROM AUTHOR]

Lithospheric thinning occurred in the North China Craton (NCC) that resulted in extensive Mesozoic magmatism, which has provided the opportunity to explore the mechanism of the destruction of the NCC. In this study, new zircon U–Pb ages, geochemical and Lu–Hf isotopic data are presented for Early Cretaceous adakitic rocks in the Liaodong Peninsula, with the aim of establishing their origin as well as the thinning mechanism of the NCC. The zircon U–Pb data show that crystallization occurred during 127–120 Ma (i.e. Early Cretaceous). These rocks are characterized by high Sr (294–711 ppm) content and Sr/Y ratio (38.5–108), low Yb (0.54–1.24 ppm) and Y (4.9–16.4 ppm) contents, and with no obvious Eu anomalies, implying that they are adakitic rocks. They are enriched in large-ion lithophile elements (e.g. Ba, K, Pb and Sr) and depleted in high-field-strength elements (e.g. Nb, Ta, P and Ti). These adakitic rocks have negative zircon ϵ Hf(t) contents (−28.9 to −15.0) with two-stage Hf model ages (T DM2) of 3004–2131 Ma. Based on the geochemical features, such as low TiO2 and MgO contents, and high La/Yb and K2O/Na2O ratios, these adakites originated from the partial melting of thickened eclogitic lower crust. They were in an extensional setting associated with the slab rollback of the Palaeo-Pacific Ocean. In combination with previous studies, as a result of the rapid retracting of the Palaeo-Pacific Ocean during 130–120 Ma, the asthenosphere upwelled and modified the thickened lithospheric mantle, which lost its stability, resulting in the lithospheric delamination and thinning of the NCC. [ABSTRACT FROM AUTHOR]

The formation of post-collisional mantle-derived rocks in the Tibetan Plateau has been linked to the deep geodynamic processes that cause surface uplift. Co-existing silica-oversaturated to silica-undersaturated mantle-derived rocks have been identified in the northern Qiangtang Terrane (NQT). However, the origins of silica-undersaturated magmas are controversial, and the mechanisms responsible for variable silica activity in the mantle-derived rocks are unclear. Here, we present 40Ar/39Ar chronology, mineral chemistry, and whole-rock geochemical data for the Bamaoqiongzong (BMQZ) volcanic rocks of the NQT. The BMQZ volcanic rocks consist of olivine leucitites, trachybasalts, and phonolites and were erupted at ca. 29 Ma. All samples are unsaturated in silica and characterized by enrichment in light rare earth elements and large-ion lithophile elements, depletion in high-field-strength elements, and the presence of negative Nb–Ta–Ti anomalies and positive Pb anomalies. All samples show limited variation in (87Sr/86Sr)i (0.7079–0.7085) and εNd(t) values (−6.9 to −5.3). The geochemical compositions of the BMQZ volcanic rocks indicate that they were produced by partial melting of carbonated phlogopite–lherzolite within the lithospheric mantle. The formation of the olivine leucitites-trachybasalts-phonolites suite was controlled by fractional crystallization and magma mixing in a magmatic plumbing system. This plumbing system included several independent reservoirs and conduits within the crust. The enriched mantle sources of the BMQZ volcanic rocks were formed by the addition of carbonate-rich melts released from the southward-subducted Songpan–Ganzi Terrane after the Late Cretaceous. Our new results, together with published data, reveal systematic variations in geochemical compositions between silica-undersaturated and silica-oversaturated rocks in the NQT, which are ascribed to variations in the nature of the subducted continental materials added during intracontinental subduction. Carbonate-rich melts that were formed by the breakdown of carbonate minerals helped to generate the mantle sources of silica-undersaturated rocks, whereas silicate melts produced by the partial melting of sediment diapirs contributed to the generation of the silica-oversaturated rocks. On the basis of published numerical modelling of continental subduction and crustal deformation records in the NQT, we suggest that intracontinental subduction and lithospheric thinning together contributed to the generation of post-collisional mantle-derived rocks in the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The Middle‒Late Mesozoic massive volcanism formed a considerable thickness of volcanic‐sedimentary strata in western Liaoning, northern China. Concomitantly, it elevated phosphorus (P) availability for the rapid bloom of the terrestrial Yanliao and Jehol biotas, which developed highly abundant biodiversity and biomass. Hence, systematic tectonic and geochemical analyses of these volcanic‐sedimentary sequences with a significant P fluctuation would advance our understanding of the coevolutionary relationship between terrestrial biotas and regional tectonics. Here, we show that the secular variation of P availability in the Mesozoic volcanic rocks were the immediate results of the changes in volcanic intensity and lithospheric thickness controlled by the geological background of the cratonic destruction resulting from the paleo‐Pacific plate subduction. This study reveals the constraint effect of regional tectonics on the evolution of terrestrial ecosystems through the volcanism and P cycle. Plain Language Summary: The phosphorus (P) is necessary for biotas and mainly comes from volcanics in areas dominated by volcanism closely related to deep‐Earth processes. Thus, the origin of P changes in volcanics can provide key evidence for the intrinsic relations between deep processes and biota evolution. Here, we present tectonic and geochemical analyses for the Mesozoic fossil‐bearing volcanic‐sedimentary strata in northern China. The westward subduction of the paleo‐Pacific plate triggered the crustal thickening and subsequent lithospheric thinning of the East Asia continent. These dynamic processes controlled the volcanic intensity and P variation, resulting in remarkable changes in P availability that led to the rise and fall of terrestrial biotas. Hence, P variations in volcanic sequences reveal the linkage between regional tectonics and biota evolution. This study represents an effort to explore how tectonic processes constrained terrestrial biotas involving multidisciplinary methods. Key Points: The paleo‐Pacific subduction triggered the cratonic destruction and thus controlled the intensity of volcanism in the Middle‒Late MesozoicThe change of lithospheric thickness triggered by the paleo‐Pacific subduction caused the variation of P content in the volcanicsRegional tectonics could impact the evolution of terrestrial ecosystems through the volcanism and nutrient P cycle [ABSTRACT FROM AUTHOR]

[Display omitted] • Intermediate–mafic dyke swarms in Jiaodong peninsula are dated (122–121 Ma). • The dykes were formed in a WNW-ESE oriented extensional stress field. • Tectono-magmatic processes at crust–mantle depths were decoupled along the Moho. • Destruction of the lithospheric keel in southeastern NCC occurred at 122–120 Ma. • Tectonic extension acted as the major driving force for destruction of the craton. The coupling/decoupling relationships between shallow crustal deformation and deep mantle tectono-magmatic activities, during lithospheric thinning and destruction of cratons, remain hotly debated in the last decades. Multidisciplinary studies were done on intermediate–mafic dyke swarms diffusively located in southern Jiaodong peninsula, southeastern North China craton (NCC) to explore the crustal and lithospheric mantle responses to regional tectonic extension. Uniform ages (122–121 Ma) of the dykes indicate intensive magma generation at the mantle depth around 122 Ma related to large-scale tectonic extension of regional lithospheric mantle. Systemic anisotropy of magnetic susceptibility (AMS), geochemical, and Sr-Nd isotope analyses suggest that the dykes were originated from enriched lithospheric mantle sources and emplaced along crustal fractures formed in a WNW-ESE oriented extensional stress field. We show that the Jiaodong lithosphere experienced two stages of Early Cretaceous tectonic evolution, i.e., an early stage (135–122 Ma) lithospheric thinning characterized by large-scale tectonic extension of the crust and limited magmatic activities of crustal sources, and a late stage (122–108 Ma) lithospheric root collapse dominated by intensive tectonic extension and magmatism in the lithospheric mantle level. The decoupling crust-mantle evolution during lithospheric thinning and destruction of the NCC is ascribed to continuous tectonic extension in WNW-ESE direction. [ABSTRACT FROM AUTHOR]

Abstract The Middle‒Late Mesozoic massive volcanism formed a considerable thickness of volcanic‐sedimentary strata in western Liaoning, northern China. Concomitantly, it elevated phosphorus (P) availability for the rapid bloom of the terrestrial Yanliao and Jehol biotas, which developed highly abundant biodiversity and biomass. Hence, systematic tectonic and geochemical analyses of these volcanic‐sedimentary sequences with a significant P fluctuation would advance our understanding of the coevolutionary relationship between terrestrial biotas and regional tectonics. Here, we show that the secular variation of P availability in the Mesozoic volcanic rocks were the immediate results of the changes in volcanic intensity and lithospheric thickness controlled by the geological background of the cratonic destruction resulting from the paleo‐Pacific plate subduction. This study reveals the constraint effect of regional tectonics on the evolution of terrestrial ecosystems through the volcanism and P cycle.

The modification of the Archaean lithospheric mantle root beneath the eastern North China Craton (NCC) has been noticed. However, the degree of modification and the characteristics of metasomatic agents for the NCC lithospheric mantle are still unclear. Here, we compile the geochemistry and 87Sr/86Sr and 143Nd/144Nd isotope ratios of Cretaceous primitive basalts (Yixian, Sihetun, Fangcheng and Feixian) from the eastern NCC and estimate the inputs of subduction-related elements into the Archaean lithospheric mantle beneath the NCC. These basalts show primitive (high MgO, Cr and Ni contents) and arc-like geochemical features (enrichments in LILEs and depletions in HFSEs) that indicate that the mantle sources were modified by fluids related to subducted crustal materials. Substantial proportions of subduction-mobile elements (e.g. ~95% Ba and ~90% Th) transferred to the basalt sources via hydrous melts. Thus, a large volume of fluids transferred into the lithospheric mantle. The data support the model that the NCC Archaean lithospheric mantle was weakened by hydrous melts, which resulted in a fusible weakened lithospheric mantle. Preliminary lithospheric thinning was induced by the extension of the NCC resulting from trench retreat of the Paleo-Pacific plate at ~140-120 Ma. Then, decompression melting of the lithospheric mantle caused pervasive melts in the weakened lithospheric mantle, resulting in the lithospheric mantle having a low viscosity comparable to the asthenospheric mantle, which principally reduced the lithospheric mantle. [ABSTRACT FROM AUTHOR]

Despite numerous years and avenues of investigation, the timing, evolution, and mechanism of lithospheric thinning of the North China Craton (NCC) are still highly debated. Late Triassic igneous rocks especially mantle derived mafic rocks could provide critical information related to the post-collisional lithospheric thinning of the Liaodong Peninsula in the eastern NCC. Using newly acquired geochronological data points, we determined that the intrusive rocks have emplacement ages of 219–209 Ma, which are typical of Late Triassic magmatism. The studied Qinghekou gabbros have low SiO2 (49.43–51.86 wt.%), Na2O+K2O (3.59–7.20 wt.%), high MgO (3.70–8.54 wt.%) and transition metal element contents, with Mg# values ranging from 49.2 to 69.3. While these samples are enriched in large ion lithophile elements such as Rb, Ba, and K and light rare earth elements, they are depleted in high field strength elements such as Nb, Ta, Ti, and P and heavy rare earth elements. We conclude that these gabbros samples were formed in a subduction-related tectonic setting, where the primary magmas were derived from partial melting of the lithospheric mantle that experienced metasomatism via slab-related fluids. Our Tongyuanpu granite samples have I-type granite affinity, as indicated by their high SiO2 (73.60–75.30 wt.%) and low MgO (0.08–0.32 wt.%) contents, as well as the A/CNK values of 0.99–1.25 and the zircon saturated temperature values of 757–832°C, the parental magmas for these granites were generated by partial melting of the lower crust. Combined with the spatio-temporal distribution and rock-assemblages of the Late Triassic intrusive rocks, we conclude that these rocks were formed in an extensional environment characterized by lithospheric thinning caused by lithospheric delamination after the collision between the NCC and the Yangtze Craton. Furthermore, we infer that the initial lithospheric thinning of the eastern NCC occurred during the Late Triassic. [ABSTRACT FROM AUTHOR]

While hotspot tracks beneath thin oceanic lithosphere are visible as volcanic island chains, the plume‐lithosphere interaction for thick continental or cratonic lithosphere often remains hidden due to the lack of volcanism. To identify plume tracks with missing volcanism, we characterize the amplitude and timing of surface heat flux anomalies following a plume‐lithosphere interaction using mantle convection models. Our numerical results confirm an analytical relationship in which surface heat flux increases with the extent of lithosphere thinning, which is primarily controlled by the viscosity structure of the lower lithosphere and the asthenosphere. We find that lithosphere thinning is greatest when the plate is above the plume conduit, while the maximum heat flux anomaly occurs about 40–140 Myr later. Therefore, younger continental and cratonic plume tracks can be identified by observed lithosphere thinning, and older tracks by an increased surface heat flux, even if they lack extrusive magmatism. Plain Language Summary: Extra heat is transmitted through Earth's tectonic plates above hot upwellings called plumes, and contributes to the heat budget of glaciated regions such as Greenland. A thin oceanic plate moving over such an upwelling typically yields a chain of age‐progressing volcanic islands such as Hawaii. However, such volcanism is often missing in continental regions such as Africa or Greenland, which have thicker plates. Nonetheless, the passage of the plate over the upwelling leaves a trace in the form of a reduced plate thickness and an increased amount of emitted heat even millions of years after the plume passage. In this study, we use numerical models of mantle convection to show that these two observations are directly linked to each other, with a larger heat flux anomaly observed for areas that have been thinned more extensively. Furthermore, we demonstrate that there is a significant time delay between the thinning, which happens during the passage of the upwelling, and the heat flux that is observed many millions of years later. As a consequence, past interactions of plates with plumes can influence today's heat output in continental regions. Key Points: We used numerical and analytical approaches to characterize heat flux anomalies following plume impingement on the lithosphereSurface heat flux anomalies follow an analytical relationship that predicts increasing heat flux with increasing basal lithospheric erosionLithosphere thinning is mostly controlled by viscosity structure, with a maximum surface heat flux anomaly following 40–140 Myr later [ABSTRACT FROM AUTHOR]

Unlike stable cratons elsewhere in the world, the lithosphere is strongly thinned in the east of both the North China Craton (NCC) and the Yangtze Craton (YZC) compared with the west. We deployed four active-source onshore-offshore wide-angle seismic survey lines in the eastern NCC and YZC from 2010 to 2016 with the aim of revealing the mechanism of lithospheric thinning and the process of the collision between the NCC and YZC. We obtained high-resolution crustal P-wave velocity models for the eastern NCC and YZC based on seismic forward modeling, travel-time tomography, and finite-difference wave-field modeling. Based on our integrated geophysical study and previous work, we propose a five-stage model for the collision between the YZC and NCC, with different dominant geodynamic mechanisms in each stage. Our collision model shows that lithospheric thinning in the eastern NCC and YZC is a consequence of the NCC-YZC collision and subduction of the Pacific plate.

Late Mesozoic lithospheric extension in NE China resulted in the development of a large extensional province and widespread formation of volcanic-sedimentary basins. The Songliao Basin is the largest one and contains voluminous volcanic rocks composing the majority of the basin fill. This study focuses on two adjacent eruption cycles, the Huoshiling Formation (K1h) and the first member of the Yingcheng Formation (K1yc1), in the Changling fault depression of the Songliao basin, constrains their time ranges and compares the origins of volcanic rocks. Zircon populations from K1h yield U-Pb ages of 124–118 Ma; those from K1yc1 yield younger ones (115–106 Ma). Different volcanic rocks are identified in K1h (alkaline basic rocks, calc-alkaline intermediate-acid rocks) and K1yc1 (alkaline basic rocks, A-type rhyolites), and their geochemistry and isotope characteristics confirm their different origins. The alkaline basic rocks from K1h have the similar magma source as those from K1yc1; both formed under within-plate conditions from an ocean island basalt (OIB)-type mantle source, assumed to be the heterogeneous shallow asthenosphere. The calc-alkaline intermediate-acid volcanic rocks from K1h formed by fractional crystallization of magma, related to the enriched lithospheric mantle, whereas the A-type rhyolites from K1yc1 directly originated from the partial melting of crust newly formed from the depleted mantle. The development of alkaline basic rocks and A-type acid rocks, a typical bimodal volcanic assemblage in K1yc1, requires a relatively thin lithosphere and thus implies that lithospheric thinning reached its maximum during this time (115–106 Ma). However, the rare expression of alkaline basic rocks and the formation of acid rocks mainly by fractional crystallization in K1h indicate that the lithosphere was relatively thick; during this time (124–118 Ma), the lithosphere below the Songliao Basin had just begun thinning. These different stages of lithospheric extension may be due to the intermittent rollback of the Palaeo-Pacific Plate. [ABSTRACT FROM AUTHOR]

The timing and mechanisms of lithospheric thinning and destruction of the North China Craton (NCC) remain controversial, and the overall geodynamics of the process are poorly understood. This paper documents Late Triassic igneous rocks including monzogranite, gabbro, and diorite from the Xiuyan District on the Liaodong Peninsula in the eastern NCC, which have LA‐ICP‐MS zircon U‐Pb ages of 229.0 ± 0.4 Ma, 216.2 ± 0.9 Ma, and 210.6 ± 2.0 Ma, respectively. Monzogranite shows high‐SiO2 adakite affinity, negative ∊Hf(t) values (–20.6 to –17.9), and old TDM2 ages (3.53–3.29 Ga), suggesting that their parental magma was derived from thickened Paleoarchean mafic lower crust and minor mantle materials that were also involved their generation. Gabbro is ultrapotassic, strongly enriched in LREEs and LILEs, depleted in HFSEs, and has evolved zircon Hf isotopes with negative ∊Hf of –10.04 to –5.85 and old TDM2 ages (2.59 –2.22 Ga). These are diagnostic signatures of a crustal component, but their high contents of MgO, Cr, Co, Ni indicate that the primary magma originated from enriched mantle. Diorite is enriched in LILEs and LREEs, depleted in HFSEs (with negative Nb, Ta, and Ti anomalies), and contains negative ∊Hf(t) values (–13.64 to –11.01). Compared with the gabbro, the diorite is relatively enriched in Nb, Ta and HREEs, and also contains younger TDM2 ages (2.11–1.94 Ga), suggesting that the diorite was formed by mixing between ancient lower crust‐derived felsic magmas and asthenospheric mantle‐derived magmas. Field observations, geochronology, geochemistry, and zircon Lu‐Hf isotopes indicate that Late Triassic magmatism and tectonic activity resulted from deep subduction of the Yangtze Craton beneath the NCC in the Xiuyan area. This phase of tectonic activity was completed in the eastern NCC by the Late Triassic (216 Ma), and was subsequently followed by lithospheric thinning that began in the Late Triassic. [ABSTRACT FROM AUTHOR]

The existence of historical flat slabs remains debated. We evaluate past subduction since 200 Ma using global models with data assimilation. By reproducing major Mesozoic slabs whose dip angles satisfy geological constraints, the model suggests a previously unrecognized continental‐scale flat slab during the Late Cretaceous beneath East Asia, a result independent of plate reconstructions, continental lithospheric thickness, convergence rate, and seafloor age. Tests show that the pre‐Cretaceous subduction history, both along the western Pacific and Tethyan trenches, is the most important reason for the formation of this prominent flat Izanagi slab. Physically, continuing subduction increases the gravitational torque, which, through balancing the suction torque, progressively reduces dynamic pressure above the slab and decreases the slab dip angle. The flat Izanagi slab explains the observed East Asian lithospheric thinning that led to the formation of the North‐South Gravity Lineament, tectonic inversion of sedimentary basins, uplift of the Greater Xing'an‐Taihang‐Xuefeng mountains and the abrupt termination of intraplate volcanism during the Late Cretaceous. Plain Language Summary: Flat subduction refers to a downgoing slab whose dip angle is smaller than 15°. Although we can observe the present‐day flat slabs through seismic imaging, it is harder to detect the ancient ones. In this study, we use global geodynamic models to simulate subduction during the past 200 Ma and find that there was a flat Izanagi slab beneath East Asia during the Late Cretaceous. This previously unrecognized flat slab provides an alternative and unified explanation for multiple synchronous geological events in East Asia, including the thin lithosphere to the east of the North‐South Gravity Lineament, inversion of sedimentary basins in the region, uplift of the Greater Xing'an‐Taihang‐Xuefeng mountains and the termination of intraplate volcanisms. We also evaluate different mechanisms for the formation of the flat Izanagi slab and find that the most important reason is the long‐lasting Mesozoic subduction along the western Pacific margin. Key Points: Global data‐assimilation models reproducing past subduction discovered a previously unrecognized continental‐scale flat Izanagi slabThe flat Izanagi slab caused the unique East Asian lithospheric structure, basin inversion and regional uplift during the Late CretaceousThe key mechanism of this flat slab is dynamic suction due to long‐lived prior subduction along the west Pacific and south Asian margins [ABSTRACT FROM AUTHOR]

A suite of Jurassic–Cretaceous migmatites was newly identified in the Liaodong Peninsula of the eastern North China Craton (NCC). Anatexis is commonly associated with crustal thickening. However, the newly identified migmatites were formed during strong lithospheric thinning accompanied by voluminous magmatism and intense deformation. Field investigations show that the migmatites are spatially associated with low-angle detachment faults. Numerous leucosomes occur either as isolated lenses or thin layers (dykes), parallel to or cross-cutting the foliation. Peritectic minerals such as titanite and sillimanite are distributed mainly along the boundaries of reactant minerals or are accumulated along the foliation. Most zircons show distinct core–rim structures, and the rims have low Th/U ratios (0.01–0.24). Zircon U–Pb dating results indicate that the protoliths of the migmatites were either the Late Triassic (224–221 Ma) diorites or metasedimentary rocks deposited sometime after c. 1857 Ma. The zircon overgrowth rims record crystallization ages of 173–161 Ma and 125 Ma, which represent the formation time of leucosomes. These ages are consistent with those reported magmatic events in the Liaodong Peninsula and surrounding areas. The leucosomes indicate a strong anatectic event during the Jurassic–Cretaceous period. Partial melting occurred through the breakdown of muscovite and biotite with the presence of water-rich fluid under a thermal anomaly regime. The possible mechanism that caused the 173–161 Ma and 125 Ma anatectic events was intimately related to the regional crustal extension during the lithospheric thinning of the NCC. Meanwhile, the newly generated melts further weakened the rigidity of the crust and enhanced the extension. [ABSTRACT FROM AUTHOR]

The dynamic process of ocean-continent subduction depends on not only the properties of the subducting oceanic plate, but also the characteristics and state of the overriding continental plate. Numerical models conducted to date have mostly focused on the oceanic lithosphere in this regard; research on the properties of overriding continental lithosphere remains relatively limited, especially the influence of its thermal state on subduction dynamics. Here we explored the performance of continental lithosphere with different thermal states during the subduction process using two-dimensional thermal-mechanical modeling and systematically investigated the effects of the thermal state of overriding continental plate, the age of subducting oceanic plate, and relative convergence rate on subduction dynamics. Modeling results show that: (1) When the geothermal gradient of continental crust is low (between 10 and 15 °C km−1), the oceanic plate first subducts at a low angle. As subduction continues, the slab dip gradually increases and the slab begins to retreat rapidly driven by its negative buoyancy, opening an ocean basin ranging from 600 to 1100 km in width. This leads to the decoupling between the overriding continental plate and oceanic plate. As the trench retreat continues, the horizontal deviatoric stress inside the overriding continental crust alternates between being positive and negative in a local area. Thinning of the overriding lithosphere mainly occurs at the region adjacent to the subduction zone, where the surface experiences significant subsidence. (2) When the geothermal gradient of continental crust is higher (greater than 15 °C km−1), oceanic plate retreat causes the overriding continental plate to be strongly stretched. In this case, the trench retreat distance decreases and the width of the ocean basin also reduces by between 100 and 1000 km. The horizontal deviatoric stress inside the whole overriding continental crust first manifests as compression and then changes into extension, which causes the surface to first uplift and then slowly subside. (3) Increasing the age of oceanic lithosphere accelerates trench retreat and promotes overriding plate thinning. (4) An advancing overriding continental plate slows down trench retreat. In cases where the geothermal gradient of continental crust is greater than 17.5 °C km−1, the hot continental crust experiences gravitational collapse and is overthrusted onto oceanic lithosphere, resulting in slow trench retreat. We analyzed the subduction process of the western Paleo-Pacific Plate in the Early Cretaceous based on our modeling results and discussed its possible control on the tectonic evolution of the rift basins in east Asia. We suggest that the development of a wide rift basin system on the Amurian Superterrane in the Early Cretaceous was likely related to slow trench retreat and the collapse of the hot crust, and the formation of a series of passive rift basins in the North China Craton was likely caused by the relatively cold thermal state of the lithosphere and the rapid retreat of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

The gold mineralization of the North China Craton (NCC) is characterized by regional heterogeneous distribution. Such a feature is mainly reflected by the spatial dispersity and local concentration, as well as multiperiods of gold‐forming events. Gold deposits are principally converged in the Jiaodong, Xiaoqinling‐Xiong'er Mountain, Jidong, Liaodong, and Taihang Mountain regions. The northern margin of the NCC is strongly enriched in Au, Mo, and Cu elements, whereas its southern and eastern margins trend to show significant enrichment of Au–Mo and Au, respectively. Among them, the early period of Mesozoic mineralization is Au–Mo–Pb–Zn combination, the peak is Au, and the late period is Au–Ag combination. The Early Cretaceous is the main gold metallogenic epoch of the NCC followed by the Middle–Late Triassic and Jurassic. Generally, gold mineralization time of the Xiaoqinling‐Xiong'er Mountain and Taihang Mountain is a little earlier than those of Jiaodong gold deposits; some of Jidong (Jinchangyu, Yuerya, and Niuxinshan) and the Liaodong (Baiyun and Maoling) gold deposits were formed in the Triassic–Jurassic. Overall, the uneven distribution of gold deposits in the NCC is generally controlled by the tectonic evolution and interaction of the regional geological blocks, the hydrothermal alteration and gold activation in the metamorphic basement, and the Mesozoic magma activity. In the Middle Jurassic and before, the tectonic evolution of the NCC was mainly influenced by the Central Asian Orogenic Belt and the Qinling Orogenic Belt. Tectonic system transition from extrusion to extension, locally developed mantle upwelling and lithospheric thinning, as well as a series of Middle Triassic–Jurassic magmatic activities, and even the presence of alkaline rocks along the east–west direction occurred on the northern margin of the NCC, which generated a series of Au–Mo deposits. This is the first craton destruction and gold mineralization event that occurred in the northern margin of the NCC after its formation. In the Cretaceous and after, the geological evolution of the NCC was mainly controlled by the ancient Pacific Plate. The NCC was subjected to extensive lithospheric thinning, which in turn led to a more large‐scale gold mineralization. In addition, it is found that these ore‐forming materials sourced from the metamorphic rock are not entirely dependent on the gold content but also affected by one or more geological processes, which activate and extract gold from the wall rock and upgrade it in suitable tectonic environments. The influence of granitoids and intermediate–basic dikes in these gold deposits seems like a "hot machine," which is the source of metallogenic hydrothermal fluid, and it is also a possible source of some ore‐forming minerals. [ABSTRACT FROM AUTHOR]

A section from the Linglong gold deposit on the northwestern Jiaodong Peninsula, East China, containing Late Mesozoic magmatic rocks from mafic and intermediate dikes and felsic intrusions, was chosen to investigate the lithospheric evolution of the eastern North China Craton (NCC). Zircon U–Pb data showed that low-Mg adakitic monzogranites and granodiorite intrusions were emplaced during the Late Jurassic (~145 ​Ma) and late Early Cretaceous (112–107 ​Ma), respectively; high-Mg adakitic diorite and mafic dikes were also emplaced during the Early Cretaceous at ~139 ​Ma and ~118 ​Ma, and 125–145 ​Ma and 115–120 ​Ma, respectively. The geochemical data, including whole-rock major and trace element compositions and Sr–Nd–Pb isotopes, imply that the mafic dikes originated from the partial melting of a lithospheric mantle metasomatised through hydrous fluids from a subducted oceanic slab. Low-Mg adakitic monzogranites and granodiorite intrusions originated from the partial melting of the thickened lower crust of the NCC, while high-Mg adakitic diorite dikes originated from the mixing of mafic and felsic melts. Late Mesozoic magmatism showed that lithosphere-derived melts showed a similar source depth and that crust-derived felsic melts originated from the continuously thickened lower crust of the Jiaodong Peninsula from the Late Jurassic to Early Cretaceous. We infer that the lower crust of the eastern NCC was thickened through compression and subduction of the Palaeo-Pacific plate beneath the NCC during the Middle Jurassic. Slab rollback of the plate from ~160 ​Ma resulted in lithospheric thinning and accompanied Late Mesozoic magmatism. Image 1 • Late Mesozoic low-Mg and high-Mg adakitic rocks are found in the northwestern Jiaodong Peninsula. • NCC lower crust thickened via compression and Middle-Jurassic subduction of Palaeo–Pacific plate. • The low crust of NCC is invariable and its lithospheric thinning occurred at the lithospheric mantle depth. • Slab rollback at ~160 ​Ma caused lithospheric thinning and Late Mesozoic magmatism. [ABSTRACT FROM AUTHOR]

The 595–560 Ma post-collisional magmatism in the Alto Pajeú Domain, Borborema Province, northeastern Brazil, is characterized by the intrusion of voluminous high-K calc-alkaline, shoshonitic and ultrapotassic magmas. The nature of the source rocks and the geodynamic context associated with the generation and emplacement of this post-collisional magmatism is still enigmatic. In this study, we report new U Pb ages, elemental geochemistry, mineral chemistry and Sr Nd isotope data for rocks from the Pajeú batholith. LA-ICP-MS zircon U Pb dating revealed that this batholith was formed by at least two distinct magma pulses. The oldest pulse (ca. 592 Ma) consists mainly of porphyritic quartz monzonites to monzogranites with abundant mafic microgranular enclaves (MMEs), while the younger pulse (ca. 568 Ma) is composed of equigranular biotite granites. The porphyritic monzogranites are magnesian, have intermediate to acidic compositions (SiO 2 = 62.2–67.6 wt%) and high Mg# (44–55) values. In contrast, biotite granites are ferroan, have high SiO 2 (69.3–73.1 wt%) and low Mg# (16–36) values. Both rock types are characterized by enrichment in LREE and LILE and depletion in HREE and HFSE, but with more fractionated REE patterns for biotite granites ([La/Yb] N = 67.4–101.5) than for porphyritic rocks ([La/Yb] N = 35.8–54.8). The Sr Nd isotopic values for the different rock types are roughly similar. However, biotite granites show slightly higher initial 87Sr/86Sr (0.71265–0.71412) ratios and more negative ε Nd (t) (−18.45 to −18.67) values than porphyritic monzogranites (initial 87Sr/86Sr ratios from 0.71077 to 0.71155 and ε Nd (t) from −16.04 to −16.96). These geochemical and isotopic signatures, together with mineral chemistry data, suggest different sources for the two rock types. The biotite granites are of purely crustal origin, derived by partial melting of a Paleoproterozoic amphibolitic lower continental crust, while a mixture of melts derived from the Paleoproterozoic continental crust and magmas derived from an enriched lithospheric mantle could explain the origin of porphyritic monzogranites. Based on the spatial and temporal distribution of magmatic rocks from the Alto Pajeú Domain, we suggest that a local lithospheric thinning model could explain the evolution of post-collisional magmatism in this region of the Borborema Province. • Several sources were involved in the generation of the Pajeú batholith granitoids. • Heterogeneous continental crust is most likely the source of the ferroan granitoids. • Domains of the lithospheric mantle were metasomatized rather than the entire mantle. • Post-collisional magmatism in the APD was triggered by a lithospheric thinning event. [ABSTRACT FROM AUTHOR]

[Display omitted] • Basalts in Cuona and diabases in Zhegucuo were formed at 137–131 Ma. • Both these basalts and diabases were derived from melts formed via melting of the Kerguelen plume and lithospheric mantle, respectively. • Eastern Gondwana breakup resulted from the reactivated suture zone and the Kerguelen plume. Geochronological, geochemical, and Sr–Nd isotope data for the mafic rocks from Cuona and Zhegucuo areas, Southern Tibet are presented to understand better the connection between the Kerguelen mantle plume and the breakup of eastern Gondwana. Zircon U–Pb dating yielded a concordant, weighted-mean 206Pb/238U age of 131 Ma for the Zhegucuo diabases. Compared to the Cuona basalts, the Zhegucuo diabases have higher Mg# values and MgO, Ni, and Cr contents closer to those of primary mantle melts. The Cuona basalts have ocean island basalt-like compositions, including light rare-earth element enrichments, positive Nb–Ta anomalies, and positive ε Nd (t) values (+1.20 to +2.97). The Zhegucuo diabases are characterized by Nb depletion, Zr and Hf enrichment, and negative ε Nd (t) values (−2.71 to −2.26). Modeling implies that low degrees (4––7%) of partial melting of garnet lherzolites (3–5 % garnet) within the Kerguelen mantle plume can produce Cuona basalts. However, the Zhegucuo diabases were formed by similar degrees (4–7%) of partial melting of spinel-bearing lherzolite (2 vol% spinel) in the shallow enriched lithospheric mantle. The positive anomalies of Zr–Hf in the Zhegucuo diabases are because their sources have melted. The Tethyan Himalaya underwent lithospheric thinning during the Early Cretaceous, resulting from the impact of the Kerguelen mantle plume. The breakup of eastern Gondwana could have been a combination of the reactivation of the former suture zone and the arrival of a new mantle plume beneath the Tethyan Himalaya. [ABSTRACT FROM AUTHOR]

• A thin and flat LAB is observed in Central Eastern China, suggesting uniform destruction. • We attribute the destruction to lithospheric delamination along a mid-lithospheric discontinuity. • After the destruction, slab rollback and trench retreat further stretched the lithosphere. Detailed knowledge of the lithospheric thickness is important for understanding the tectonic evolution in central Eastern China, characterized by ore deposits in the Middle-Lower Yangtze Metallogenic Belt (MLYMB). We realize this goal by applying the common conversion point (CCP) stacking to Sp receiver functions (SRF) computed from 234 broadband seismic stations in central Eastern China. Distinct negative signals are identified below the Moho in all the CCP stacking profiles, which we interpret as the S-to-P conversions from the lithosphere-asthenosphere boundary (LAB). The imaged LAB is as shallow as ∼60 km with a standard deviation of ∼5 km in the whole region, in contrast to the typical cratonic lithosphere root down to 200 km depth or more, indicating the widespread lithospheric thinning in the study region. Such a flat LAB indicates that the regional lithosphere has been destructed uniformly, shedding light on its destructive mechanism, which we attribute to lithospheric delamination along a mid-lithospheric discontinuity (MLD). Compared to the MLD (∼80–100 km) observed in the western North China Craton, our observations suggest that the destructed lithosphere probably has been further stretched due to slab rollback and trench retreat. In contrast, lithospheric cooling-induced accretion plays a minor role in the lithospheric evolution after destruction. [ABSTRACT FROM AUTHOR]

Knowledge the initial extension in the Indian continent during the Jurassic is important for understanding the dynamics of its breakup from Eastern Gondwana. The absence of Jurassic magmatic activity in the eastern Tethyan Himalaya hinders the understanding of this process. We report a provenance and tectonic setting study on the Middle Jurassic Zhela and Late Jurassic Weimei Formations sandstone in Gyangze, eastern Tethyan Himalaya. Detrital zircons of Jurassic sediments indicate four major age peaks: ∼500 Ma, ∼820 Ma, ∼950 Ma, and ∼2450 Ma, which reflect the affinity between the Tethyan Himalaya and India. The differences between the crystallization age and depositional age of isolated detrital zircons from the Middle Jurassic Zhela and Late Jurassic Weimei Formations, indicate that they were formed in an extensional continental margin and deposited on the passive continental margin of India. Combined with regional geological information, our results show that extensional tectonics was dominant on the northern margin of the Indian continent during the Jurassic. The source-sink sedimentary system and the topography remained stable at this time. After the extension event in the Middle and Late Jurassic, the Kerguelen mantle plume commenced activity, indicating the transition from the lithospheric thinning process to active rifting. The mantle plume activity in the Early Cretaceous led to large-scale uplift in the southeast part of the Tethyan Himalaya, that ultimately led to the breakup of India from Eastern Gondwana. • The Tethyan Himalaya terrane and India had paleogeographic affinity in Jurassic. • The Tethyan Himalaya terrane was in an extensional setting in Jurassic. • Lithospheric thinning dominated in the Tethyan Himalaya terrane during Jurassic. • The active of Kerguelen mantle plume made passive rift transition to active rift. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) hosts some of the world-class gold deposits that formed more than 2 billion years after the major orogenic cycles and cratonization. The diverse models for the genesis of these deposits remain equivocal, and mostly focused on the craton margin examples, although synchronous deposits formed in the interior domains. Here we adopt an integrated geological and geophysical perspective to evaluate the possible factors that contributed to the formation of the major gold deposits in the NCC. In the Archean tectonic framework of the NCC, the locations of the major gold deposits fall within or adjacent to greenstone belts or the margins of micro-continents. In the Paleoproterozoic framework, they are markedly aligned along two major collisional sutures – the Trans North China Orogen and the Jiao-Liao-Ji Belt. Since the Mesozoic intrusions hosting these deposits do not carry adequate signals for the source of gold, we explore the deep roots based on available geophysical data. We show that the gold deposits are preferentially distributed above zones of uplifted MOHO and shallow LAB corresponding to thinned crust and eroded sub-lithospheric mantle, and that the mineralization is located above regions of high heat flow representing mantle upwelling. The NCC was at the center of a multi-convergent regime during the Mesozoic which intensely churned the mantle and significantly enriched it. The geophysical data on Moho and LAB upwarp from the centre towards east of the craton is more consistent with paleo-Pacific slab subduction from the east exerting the dominant control on lithospheric thinning. Based on these results, and together with an evaluation of the geochemical and isotopic features of the Mesozoic magmatic intrusions hosting the gold mineralization, we propose a genetic model that invokes reworking of ancient Au archives preserved in the lower crust and metasomatised upper mantle and which were generated through multiple subduction, underplating and cumulation events associated with cratonization of the NCC as well as the subduction-collision of Yangtze Craton with the NCC. The heat and material input along zones of heterogeneously thinned lithosphere from a rising turbulent mantle triggered by Mesozoic convergent margins surrounding the craton aided in reworking the deep roots of the ancient Au reservoirs, leading to the major gold metallogeny along craton margins as well as in the interior of the NCC. Image 1 • Mesozoic world-class gold deposits in the NCC distributed along Precambrian sutures. • Geophysical data indicate Moho uplift, shallow LAB and high heat flow beneath the gold deposits. • Au archives in lower crust and mantle built through ancient subduction-accretion events. • Reworking and gold concentration through Mesozoic multiple convergence and subduction. [ABSTRACT FROM AUTHOR]

There are usually abrupt changes in lithospheric thickness at the boundaries between ancient cratons and adjacent young mobile belts. Lateral variations in temperature and density between the two can trigger small-scale mantle convection (edge-driven convection, EDC). Here, we use two-dimensional thermal-mechanical simulations to explore the EDC caused by the lithospheric step between a craton and a mobile belt, and its role in the thinning of the craton lithosphere. The results show that the impact of EDC on a craton depends on the properties of the craton lithosphere and on their contrasts with the adjacent mobile belt, given the same initial condition. When the craton lithospheric density is relatively large, a high-strength craton has strong ability to resist EDC, and craton lithospheric thinning is limited to the edge. In contrast, the ability of a low-strength craton to resist EDC is weak, and the craton lithosphere is gradually eroded by the downward flow, eventually leading to large-scale thinning of the cratonic lithosphere. When the craton lithospheric density is relatively small, regardless of the strength of the cratonic lithosphere, the craton can well withstand the impacts of EDC. In this case, upwelling flow drives cratonic lithosphere materials to the base of the mobile belt, and lithospheric thinning only occurs at the edge of the craton lithosphere. The Archean North China Craton (NCC) was surrounded by Phanerozoic mobile belts, and its lithospheric thinning first occurred on the northern and eastern margins, a process that lasted for a long time. We suggest that EDC has played an important role in lithospheric thinning of the NCC, in particular the initiation of lithospheric thinning, but we cannot rule out the additional contributions from other mechanisms. [ABSTRACT FROM AUTHOR]

We present detailed geochronological, geochemical and Sr-Nd-Pb isotopic data for late Mesozoic mafic intrusions in the Taili region (western Liaodong Province) of the eastern North China Craton (NCC). We obtained laser-ablation inductively-coupled plasma mass spectrometry U-Pb zircon ages from lamprophyres with ages ranging from 139 to 162 Ma and diorites with clusters of ages at 226 ± 11 Ma, 165 ± 5.8 Ma and 140 ± 4.8 Ma. We interpret the Triassic zircons in diorites to be inherited from the Paleo-Asian Ocean slab. Both the lamprophyres and diorites contain abundant inherited grains (2644–2456 Ma) that were likely derived from the ancient NCC basement, reflecting a contribution from old lower crustal material. Like contemporaneous late Mesozoic mafic rocks in the Jiaodong and Liaodong Peninsula areas of the NCC, the Taili lamprophyres reveal a strong subduction signature in their normalized trace element patterns, including depletion of high field strength elements and enrichment of large ion lithophile elements. The rare-earth element patterns of the Taili intermediate-mafic intrusions are best explained if they were principally derived from partial melting of amphibole-bearing lherzolite in the spinel-garnet transition zone. Slab-derived melts likely contributed to the formation of late Mesozoic mafic rocks along three margins of the craton: due to accretion of the Yangtze Block along the southern margin of the craton, subduction of the Paleo-Asian Ocean along the northern margin, and subduction of the Paleo-Pacific oceanic plate along the eastern margin of NCC. We present a synthesis of the geochemical, spatial, and temporal patterns of magmatic rocks and periods of deformation that contributed to decratonization of the NCC in response to the Mesozoic tectonic evolution of adjacent plates along its northern, southern, and eastern margins. Unlabelled Image • The Taili intermediate-mafic rocks were emplaced between 165 Ma and 140 Ma. • Mafic rocks in the eastern NCC can be divided into three main stages. • Mafic rocks display distinctly different evolution processes in different regions of the NCC. • A subduction-collision model is proposed for the lithospheric thinning and decratonization of the eastern NCC. [ABSTRACT FROM AUTHOR]

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• Provide lithological and P – T –H 2 O– f o 2 conditions of the Mesozoic lithospheric mantle. • Existence of Archean lithospheric mantle under the eastern NCC in the Early Cretaceous. • The Mesozoic NCC lithospheric mantle was both largely rehydrated and highly oxidized. • The rehydration and oxidization are related to wet upwelling of the MTZ component. • New insights into the role of Earth's deep cycling in lithospheric thinning of cratons. Cratons are the most ancient parts of continents that are underlain by thick, cold, old and refractory lithospheric roots. However, how cratonic roots remain stable for billions of years and become remobilized later is still not well understood. The eastern North China Craton (NCC) is the best region to illuminate this issue because of its well-known lithospheric thinning and decratonization during the Mesozoic–Cenozoic. The thinning mechanism is debated because of limited constraints on the thermal-chemical conditions (lithology and P – T –H 2 O– f o 2) of the Archean lithospheric mantle before and during its removal. Here, we provide constraints on these thermal-chemical conditions for the Archean lithospheric mantle beneath the eastern NCC during its extensive thinning in the form of whole-rock chemical and Sr–Nd–Pb isotopic compositions and mineral (especially olivine) chemistry of the Early Cretaceous primitive basalts (MgO > 10 wt.%) from Yixian and Sihetun in the western Liaoning Province. Our data support a model in which the Yixian and Sihetun basalts were derived from metasomatized Archean lithospheric mantle under shallow (∼50–60 km), hot (∼1,290–1,350 °C) conditions. This indicates the existence of a relict (∼25 km) of the Archean lithospheric mantle during the Early Cretaceous, supporting gradual or episodic erosion of the eastern NCC lithospheric mantle. Furthermore, the NCC lithospheric mantle was not only widely rehydrated (>1,000 ppm H 2 O) but also highly oxidized (Δlog f o 2 FMQ = + 1.5 ∼ + 1.9 at 1.7–2.0 GPa) during its extensive thinning. Such rehydration and oxidization are demonstrated to be closely related to wet upwelling from the Mantle Transition Zone (MTZ) triggered by the deep subduction of the Paleo-Pacific oceanic slab in the period ∼200–125 Ma. We emphasize that the water released from the upwelling MTZ component and associated hydrous melt influx played a key role in the lithospheric thinning of the eastern NCC by oxidizing the lithospheric mantle and lowering its melting point, which led to redox melting, promoting the erosion of cratonic lithosphere. Our study provides key evidence for the role of deep volatile cycling from the MTZ in modifying thermal-chemical conditions and in the lithospheric thinning of cratons. [ABSTRACT FROM AUTHOR]

• Joint inversion of P-RFs and group velocity dispersion is done for the Singhbhum Craton. • Crustal and lithospheric thicknesses are estimated at 15 broadband sites. • A marked crustal thinning of 5–10 km is delineated below the Singhbhum Craton. • A 20 km lithospheric thinning in Singhbhum is explained by lithospheric delamination. • A flat Moho over 200 km × 200 km characterizes the Chotanagpur plateau. • A marked lithospheric thinning of 15–20 km is modelled in the Chotanagpur plateau. • Inferences are drawn for the evolution of Iron Ore Group basin in the Singhbhum Craton. An improved image of crust-mantle structure has been obtained through the joint inversion of P-to-s receiver functions and fundamental mode group velocity data (7–70 s) of Rayleigh and Love waves at fifteen broadband stations in the Eastern Indian Craton. Our modelling reveals a marked crustal thinning of 5–10 km below the Singhbhum-Odisha-Craton (SOC) while the modelled Moho depths show a flat crust with a thickness of 42 km below the Chotanagpur Granitic Gneissic Terrain (CGGT). The modelled lithosphere is thin (∼90 km) beneath the SOC and deepens on both north and south sides to ∼100 km with a sharp drop of ∼4.4% in shear velocity across the lithosphere-asthenosphere boundary. The amount of melt required in the asthenosphere to account for this drop in shear velocity is ∼1%. The isotopic constituents of the Dalma volcanic rocks contains asthenospheric component. We suggest that the modeled crustal and lithospheric thinning might have been resulted from the earlier magmatism or plume episodes that led to lithospheric delamination below the SOC. Our modeling also detects a common elongated feature (extending between latitude 21–23°N and longitude 85–86.4°E), which is characterized by a marked crustal (5–10 km) as well as lithospheric (10–15 km) thinning and a significant drop in Vs (−2.1 to −4.4%) in the upper mantle, below the SOC. This mapped area coincides with the horse-shoe shaped broad Singhbhum synclinorium known as Iron Ore Group (IOG) basin that hosts huge iron ore and to some extent manganese deposits of Precambrian age. This lithospheric feature is inferred to have played a key role in forming the passage for melts to carry various iron rich minerals and metals to the uppermost oceanic crust during the Archean plume associated with magmatism episode. [ABSTRACT FROM AUTHOR]

Abstract The Jiaobei Terrane in the southeastern North China Craton (NCC) witnessed intense magmatic pulses during Mesozoic in response to lithospheric thinning. These include sporadic felsic-porphyritic dikes which preserve important information on the magmatic processes and of its implications on lithospheric thinning. Here we present a detailed investigation of representative felsic-porphyritic dikes based on whole-rock geochemical analysis, zircon LA-ICPMS U-Pb geochronology, trace elements and hafnium isotopic compositions. Our results identify stages of felsic dikes in the Jiaobei Terrane with ages in the range of 131–127 Ma and 123–116 Ma. The early stage felsic dikes (ESFDs) have negative zircon ɛ Hf (t) (−22.4 to −11.1), high zircon Eu N /Eu N * (0.41–0.92) and Ce4+/Ce3+ (62–944), low Ti-in-zircon crystallization temperatures (524–738 °C), and are geochemically comparable to the coexisting Guojialing granodiorite. Abundant inherited zircons and scattered zircon Hf, Yb/Gd, Th/U, and Ce/Sm values suggest that the magmas from which the dikes formed involved crustal contamination. They are interpreted to be the hypabyssal phase of the Guojialing suite sourced from the Paleoproterozoic lower crust of the eastern NCC with input of mantle components, associated with extensive crust-mantle interaction during the peak lithospheric thinning. The late stage felsic dikes (LSFDs) are characterized by variable zircon ɛ Hf (t), Eu N /Eu N * and Ce4+/Ce3+ values (−20.1 to −12.2, 0.38–0.88 and 64–956 for the granodiorite- and quartz-porphyritic dikes; −27.6 to −16.2, 0.17–0.75 and 22–503 for the monzogranite-porphyritic dikes), low Ti-in-zircon crystallization temperatures (562 to 774 °C), and display geochemical similarity with the Aishan granitoids. Systematic variations of zircon Hf, Yb/Gd, Th/U and Ce/Sm suggest that fractional crystallization of hornblende played a significant role in the formation of the late dikes. The LSFDs originated from the Neoarchean-Paleoproterozoic lower crust of the NCC with heterogeneous involvement of lesser amounts of mantle materials than the early dikes, consistent with weak crust-mantle interaction during the waning stage of lithospheric thinning. In the LSFDs, the granodiorite and monzogranite porphyries are broadly coeval (123–118 Ma) with large scale gold mineralization in the area as also favored by the high zircon Ce4+/Ce3+ ratios. Our study also provides new insights into the formation of gold deposits. Graphical abstract Unlabelled Image Highlights • Two distinct pulses of Cretaceous felsic dike emplacement in the Jiaobei Terrane • Early stage emplaced at 131-127 Ma with magma sourced from Paleoproterozoic lower crust • Late stage formed at 123-116 Ma with magma source from Neoarchean-Paleoproterozoic crust • High zircon Ce4+/Ce3+ and EuN/Eu N * ratios reflect oxidized conditions with potential to generate metallic mineralization. [ABSTRACT FROM AUTHOR]

Mesozoic granitoids are widely distributed in South China, but the mechanism for generating the felsic magmas is still in debate. To understand the possible origin of the granitoids, we use joint inversion methods and forward modelling of receiver functions to reveal the lithospheric structure in the Cathaysia block. The joint inversion of receiver functions and surface wave dispersion with P-velocity constraints is applied to a dense array in the Cathaysia block, and the specific crustal Vp/Vs ratios obtained from a generalized H-κ stacking method are introduced to the traditional joint inversion for passive seismic stations. The detailed structures provide valuable knowledge of the geological processes: 1) The present-day lithosphere is 60–70 km thick, which has been thinned since the Late Mesozoic with reference to geochemical data; 2) there is a lack of high Vp and Vs in the lower crust in this region. The results may have limited resolution on the localized magmatic underplating, but they do not support the extensive magmatic underplating at the Late Mesozoic. Other factors could be the mechanism for the granitoid formation in this region. • Performed joint inversion of receiver function and dispersion with Vp constraint • Found lithospheric thickness of Cathaysia block comparable to that of eastern North China Craton • No high velocity in the lower crust that is consistent with the magmatic underplating [ABSTRACT FROM AUTHOR]

A combined study of whole-rock major and trace elements, Sr-Nd-Hf isotopes, and zircon U-Pb geochronology was conducted on late Mesozoic volcanic rocks along the Tan-Lu fault zone (the Anqiu, Gaoqiao, Juxian, and Junan regions) of Shandong Province, eastern China. The results constrain the petrogenesis of the volcanic rocks and provide important insights into the significance of the Tan-Lu fault zone for lithospheric thinning. The volcanic rocks are composed of basaltic trachyandesite, trachyandesite, trachydacite, andesite, dacite, and rhyolite, which yielded zircon U-Pb ages of 125.4 ± 0.9, 126.2 ± 1, 125.7 ± 1, 127.1 ± 1.2, 120 ± 0.65, and 122.8 ± 1 Ma, respectively, indicating eruption in the Early Cretaceous. A large amount of Palaeoproterozoic and Archaean inherited zircons exist in Anqiu and Gaoqiao volcanic rocks, but Neoproterozoic inherited zircons in Juxian and Junan volcanic rocks, in agreement with the age spectrum of the basement rocks of the North China Craton (NCC) and Neoproterozoic protolith ages of ultrahigh-pressure metaigneous rocks in Sulu orogenic belt, respectively. The volcanic rocks have high Na2O + K2O concentrations (5.94-11.33 wt.%), indicating that they are alkaline. All the rocks are characterized by enriched in light rare earth elements and large ion lithophile elements (e.g. Rb, Th, U, and K) but are depleted in high field strength elements (e.g. Nb, Ta, and Ti). Anqiu and Gaoqiao volcanic rocks have wide initial 87Sr/86Sr ratios (0.707678-0.711259), variable negative εNd(t) values (-15.2 to −11) and εHf(t) values (−19.5 to −2.2). The varied isotopic compositions and the abundance inherited zircons, together with mineral disequilibrium features, suggest that the Anqiu and Gaoqiao volcanic rocks were produced by the mixing of magmas from enriched lithospheric mantle and lower crust. The enriched lithospheric mantle originated from the ancient lithospheric mantle beneath the NCC, which was modified by the subduction of Yangtze crustal material. Juxian and Junan voalcanic rocks have initial 87Sr/86Sr ratios of 0.707502-0.709238, low εNd(t) values of −20.5 to −16.1, and negative zircon εHf(t) values of −24.6 to −16.4, similar to granitoids in Sulu orogenic belt, suggesting that they derived from similar crustal sources. Combining the existence of the Neoproterozoic inherited zircons and the isotope characteristics, we propose that the Juxian and Junan volcanic rocks were dominantly derived from partial melting of the Subducted Yangtze crust but with contributions from the mantle. The volcanic rocks along the Tan-Lu fault zone were produced under an extensional regime linked with lithospheric thinning in the eastern NCC during the Early Cretaceous. According to the characteristic spatial and temporal distributions of late Mesozoic volcanic activity along the Tan-Lu fault zone, combined with the distributions of regional adakitic rocks and the evolutionary history of the fault, we suggested that the Tan-Lu Fault played an important role in the initiation of lithospheric thinning and provide a favourable channel and beneficial conditions for magma activity. [ABSTRACT FROM AUTHOR]

Abstract The mechanisms responsible for the formation of extremely thinned continental crust (<10 km thick) and lithosphere during rifting remains debated. Observations from present-day and fossil passive margins highlight the role of deep-seated deformation, likely controlled by heterogeneities within the continental lithosphere, such as changing lithologies, mechanical anisotropies and inherited structures. We investigate the mechanisms of lithospheric thinning by exploring the role of pre-existing heterogeneities on the architecture and evolution of rifted margins. We estimate pre-rift pressure conditions (P 0) vs. depth diagrams of crustal to lithospheric sections, to quantify rift-related modifications on inherited lithostatic pressure gradients. Two field examples from the Alpine Tethys margins in the Eastern and Southern Alps (SE Switzerland and N Italy) were selected to characterize: (1) the pre-rift architecture of the continental lithosphere; (2) the localization of rift-related deformation in distinct portions of the lithosphere; and (3) the interaction between pre-existing heterogeneities of the lithosphere and rift-related structures. These observations are compared with high-resolution, two-dimensional thermo-mechanical numerical models. The design of the models takes into account pre-existing mechanical heterogeneities representing the initial pre-rift architecture of the continental lithosphere. Extensional structures consist of high-angle and low-angle normal faults, anastomosing shear-zones and decoupling horizons. Such structures accommodate the lateral extraction of mechanically stronger levels derived from the middle to lower crust. As a result, the extremely thinned continental crust in Tethyan passive margins represents the juxtaposition and amalgamation of distinct strong levels of the crust separated by major extensional structures identified by sharp pressure gradients. Future work should determine the applicability of these results to other present-day and fossil rifted margins. Graphical abstract Highlights • Pre-rift architecture of the continental lithosphere is important during rifting. • Initial mechanical heterogeneities control strain partitioning. • Extraction tectonics is an efficient thinning mechanism. • Various crustal levels can be exhumed in distal margins. [ABSTRACT FROM AUTHOR]

The Tongcheng ultrapotassic rocks intrude in Mesoproterozoic limestones in Chongxin County, Gansu Province, China, at the south‐western margin of the Ordos Block. They are characterized by high K2O and Al2O3 but low SiO2, FeOT, MgO, and CaO. The ultrapotassic rocks are relatively depleted in Nb, Ta, Ti, Zr, and Hf and enriched in the large‐ion lithophile elements Rb, Ba, and Th. Zircons from the ultrapotassic rocks yield an Early Cretaceous U–Pb age of 120 Ma. The slightly enriched whole‐rock Sr and Nd isotopic compositions ((87Sr/86Sr)i = 0.705–0.706; εNd = −4.9 to −5.2) indicate an enriched lithospheric mantle source. Combined with regional tectonic data, the Tongcheng ultrapotassic rocks were generated in an extensional environment, which were caused by the upwelling of asthenospheric mantle. Subduction of the palaeo‐Pacific Plate in Early Cretaceous resulted in large‐scale lithospheric thinning in the eastern North China Craton (NCC), which may have also occurred in the western part of the NCC, but the scale of thinning was smaller compared with that of the eastern NCC. [ABSTRACT FROM AUTHOR]

The Edolo diabase dykes intruded the Variscan basement in the central Southalpine domain. Biotite 40Ar / 39Ar dating shows that the emplacement occurred during the final stage of Permian-Triassic lithospheric thinning. In this phase on the Adria passive margin, middle Triassic magmatism with disputed arc affinity is followed by a late Triassic alkaline event associated with continental rifting. The Edolo diabase dykes are Ti-rich and alkaline, with high Nb and Ta contents and ratios in igneous amphibole, biotite, and ilmenite. These features are typical of the late Triassic magmatism. In contrast, the early-crystallized clinopyroxene shows low Nb and Ta contents and ratios and an apparent arc affinity may be thus envisaged in the clinopyroxene parental melt. However, given the coexistence of both features in the same dykes, their composition cannot be interpreted in terms of transition between tectonic environments. Instead, it is likely attributed to the heterogeneity of the Adriatic lithosphere inherited from the Variscan to Permian evolution, which underwent asthenospheric upwelling due to Permian-Triassic extensional tectonics. • Alkaline mafic dyke intruded the Adria passive margin in the late Triassic. • Clinopyroxene and amphibole are not in textural and compositional equilibrium. • The clinoyroxene parental melt reveals an arc-signature. • The amphibole parental melt is alkaline and Nb Ta rich. • The dykes were derived from chemically heterogeneous source rocks. [ABSTRACT FROM AUTHOR]

Abstract Intense magmatism and voluminous sedimentation occurred in the Jiaodong Peninsula during Mesozoic in response to the lithospheric thinning in eastern North China Craton (NCC). Here we report the results from an integrated geochemical and Sr-Nd-Pb-Hf isotopic study on granitoids and U Pb and Lu Hf isotopes of the detrital zircons from Mesozoic sediments in the Jiaodong Peninsula to provide new constraints on the crustal response to the lithospheric thinning. Geochronologic data reveal three distinct magmatic pulses at 170–140 Ma, 140–125 Ma and 125–105 Ma in this region. The Sr-Nd-Pb isotope data (0.7080–0.7139 for 87Sr/86Sr, −22.3−−10.8 for ɛ Nd (t), 16.97–17.47 for 206Pb/204Pb, 15.42–15.55 for 207Pb/204Pb, 37.36–38.34 for 208Pb/204Pb) and zircon ɛ Hf (t) values (−29−−10) for the Mesozoic plutons show more similarities with those of the lower crust of the Yangtze Craton (YC) wedged beneath the NCC, than those of the NCC. The Sr/Y, (La/Yb) N and Nb/Ta ratios for the three episodes of granitic magmatism show a gradual decrease, which is interpreted to reflect upward migration of the depth of partial melting from ~170 Ma to ~105 Ma. The dominant detrital zircon population in the sediments deposited during ca. 125–105 Ma was derived from pre-Jurassic sources in the NCC and YC basement whereas the Cretaceous population was derived from volcanic rocks in the interior of the craton. The alternating sequence suggests episodic uplift of the NCC and YC basements during this period. The data obtained in this study allow us to summarize the crustal evolution of this region into three phases. (1) During 170–140 Ma, partial melting of wedged YC lower crust resulted in high magmatic flux. (2) During 140–125 Ma, intense magmatism continued, accompanied by uplift and erosion of basement, and initiation of basin filling. (3) During 125–105 Ma, the source depth of granitoid magma became shallower associated with continuing episodic basement uplift, representing the peak of lithospheric thinning. Graphical abstract Unlabelled Image Highlights • Gradual shallowing of magma source for Late Mesozoic granitoids in Jiaodong. • The magmas were sourced from the Yangtze lower crust. • The crustal evolution in Jiaodong Peninsula includes three distinct phases. • The deep magmatism was synchronized with the surface uplift. [ABSTRACT FROM AUTHOR]

Geochronological, elemental and isotopic data of the Dashizhuzi granites and lamprophyre dykes from the eastern Hebei – western Liaoning on the northern North China Craton (NCC) provide an insight into the nature of their magma sources and subcontinental lithospheric mantle. The Dashizhuzi granites have an emplacement age of 226 Ma. They have enriched lithospheric mantle type 1 (EM1-like) Sr–Nd isotopic compositions, and have distinctive features of high Na2O and Sr and low Y with high Sr/Y and (La/Yb)N ratios. These characteristics show that the Dashizhuzi granites originated directly from melting of mafic lower crust composed of pre-existing ancient crustal and enriched mantle-derived juvenile crustal materials at normal continental crustal depth of 33–40 km. The lamprophyre dykes are dated at 167 Ma, and can be divided into two groups. The Group 1 dykes have variable Sr–Nd isotopic compositions and mid-ocean-ridge basalt (MORB-) like Th/U, Ba/Th and Ce/Pb ratios, whereas the Group 2 dykes have enriched Sr–Nd isotopic compositions and notable high Co, Cr, MgO and low Al2O3 characteristics. These distinctive features suggest that the Group 1 dykes were derived from a relatively fertile lithospheric mantle source (garnet-facies amphibole-bearing lherzolite) which has experienced variable degrees of asthenospheric mantle-derived melt–peridotite interaction prior to melting. However, the Group 2 dykes were derived from an ancient garnet-facies phlogopite and/or amphibole-bearing lherzolite lithospheric mantle. Thinning of the Early Mesozoic lithospheric mantle beneath the northern NCC is dominantly through melt–peridotite interaction and thermo-mechanical erosion prior to Middle Jurassic time. The chemical compositions have been modified at the bottom of the lithospheric mantle through melt–peridotite interaction processes. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) is one of the classic examples of decratonization through extensive lithospheric destruction during Mesozoic time. Among the various pulses of magmatism associated with cratonic erosion are the rare mafic intrusions in the Yanshan Belt. Here we investigate the Shangzhuang layered intrusion belonging to this suite, which is characterized by compositional layering with troctolite, noritic gabbro and gabbro/gabbroic anorthosite/gabbrodiorite from the bottom to top. The different lithologies of this intrusion exhibit close field relationships, similar chemical patterns and overall identical Lu–Hf isotopes indicating a co-magmatic nature. The fine-grained gabbros occurring near the margin of the intrusion display U–Pb ages similar to those of the other rocks and are considered to represent the composition of the parent magma, characterized by Fe, Mg and Ti enrichment. The magma was sourced from low-degree partial melting of spinel lherzolite sub-continental lithospheric mantle, which had been enriched by crust–mantle interaction and metasomatic fluids derived from the Mongolian oceanic slab subduction beneath the NCC during Late Palaeozoic time. In addition, limited asthenospheric or deeper-mantle materials were also locally mixed with the enriched mantle as the final source component. Our zircon U–Pb data constrain the emplacement age of this intrusion as c. 128–123 Ma in Early Cretaceous time, and correlates with the regional extensional tectonics between c. 135 and 115 Ma in the eastern and central NCC. Mantle upwelling associated with this event resulted in the thermal and chemical erosion of the lithospheric mantle, and emplacement of the parent magma of this layered intrusion. [ABSTRACT FROM AUTHOR]

The stratigraphic and structural characteristics of the initial phase of continental rift basins have been widely studied. However, the initial rifting geodynamic processes in many rift basins remain poorly understood because the relevant structures and stratigraphic successions tend to be deeply buried in result of continued rift evolution. Using an extensive database of geological (stratigraphic and structural) and geophysical data we investigate when and how rift initiation occurred in the Jianghan Basin. The correlation of the Lower Cretaceous strata across the basin reveals that they were deposited within a series of localized depressions distributed on the basin margin while the Late Cretaceous tectonic stage was characterized by widespread rifting with a maximum stratal thickness of ∼4500 m. The major faults controlling this Late Cretaceous sediment distribution are radially striking, suggesting a distributed, transtensional stress system or multi-directional extension during the Late Cretaceous. It is a common feature that pre-rift basement strata of the major faults in the hanging wall are older than that in the footwall and become progressively older approaching the fault plane, indicating a reactivation of pre-existing unroofed fault-related folds. Together with the regional geodynamic context for the South China Block, we divide the initial rifting processes into two distinct stages. During the Early Cretaceous, the lithosphere beneath the Jianghan Basin got rapidly thinned under the influence of the large-scale roll-back and dehydration of the subducted Pacific slab. Meanwhile, the upwelling asthenosphere and intruded dykes/magma heated and weakened the lithosphere, leading to thermal doming of most of the Jianghan Basin. However, on the basin margin, which was relatively unaffected by the thermal doming event, a set of localized depression sequences were deposited. Due to the Early Cretaceous lithospheric thinning, the lithosphere was thin enough to rift during the Late Cretaceous. Under the diapirism of the continuously upwelling asthenospheric mantle, the pre-existing thrusts with radial strikes simultaneously underwent extensional reactivation, forming a series of normal faults with multiple orientations. By providing the detailed stratigraphic and structural evidence for active rifting model, this study provides new insights into the processes of early rift initiation. [ABSTRACT FROM AUTHOR]

Cenozoic intraplate basalts are low in volume but widespread in eastern China. They are predominantly alkaline and have oceanic island basalt (OIB)-like trace element compositions. Despite numerous studies, the origin of Cenozoic basalts in eastern China remains elusive. Possible roles of lithosphere thickness, subduction of Pacific plate and lithosphere-asthenosphere interaction in triggering spatial geochemical variations have not yet been clarified. Here, we have carried out mineral chemistry, major and trace element and Sr Nd Hf isotope analyses of the late Cenozoic (<20 Ma) basaltic rocks from the Changbaishan-Baoqing Volcanic Belt (CVB), NE China, which revealed clear spatial compositional variations. The North CVB is dominated by basanites and alkali basalts with OIB-like trace element patterns and depleted Sr Nd Hf isotopic compositions ( 87 Sr/ 86 Sr = 0.7039–0.7047, ε Nd  = 3–5.6; ε Hf  = 6.7–12), which may have been derived from low degree partial melting of a depleted source from asthenospheric mantle beneath a thick lithosphere. On the other hand, the South CVB consists of both alkali and sub-alkali lavas (alkali basalts, tholeiites and basaltic andesites) that display generally higher SiO 2 , Sm/Nd, Ba/Nb, Th/U, and lower Nb/Th, La/Sm and more enriched Sr Nd Hf isotopic compositions ( 87 Sr/ 86 Sr = 0.7038–0.7056, ε Nd  = −2.4 – +3.2; ε Hf  = 3–8.2). These rocks may have been produced by larger degrees of partial melting of asthenospheric mantle beneath a relatively thin lithosphere. Ancient metasomatized lithospheric mantle might also have contributed to their genesis. In addition, the similar ranges of Mn, Ni and Fe/Mn for olivine phenocrysts from both the North and the South CVB suggest that they may have been derived from hybrid mantle sources containing similar proportions of peridotite and pyroxenite/eclogite components. We propose that decompression melting of upwelling asthenosphere and mechanical-chemical erosion of basal lithosphere related to lithosphere-asthenosphere interaction responsible for the genesis of the CVB magmas were likely associated with upper mantle convection and back-arc extension induced by deep subduction of the Pacific plate and its stagnancy in the transition zone. [ABSTRACT FROM AUTHOR]

Tongling, in eastern China, is an area well-known for intra-plate adakites. Here, we present the mineral chemistry and zircon U-Pb ages for amphibole cumulate xenoliths, the mineral chemistry of amphibole megacrysts, and the whole-rock chemistry, zircon U-Pb age and Sr-Nd isotopic compositions of host gabbros from Tongling. Zircon U-Pb dating yields a crystallization age of 120.6 ± 1.2 Ma (MSWD = 4.2) for the host gabbros, which are characteristically depleted in high field strength elements (Nb, Ta, and Ti) and enriched in large ion lithophile elements (Ba and Sr), with εNd (t) of −3.00 to −4.52 and initial 87Sr/86Sr ratios of 0.7068-0.7072, suggesting an enriched mantle source. Parental melts, as estimated from average amphibole megacryst and cumulate compositions, have Mg# values of 26-33, are enriched in Ba, Th, U, and Nd, and depleted in Nb, Ta, Zr, Hf, and Ti, similar to 136 Ma mafic magmas in Tongling. Zircon U-Pb dating yields a crystallization age of 135.4 ± 1.0 Ma (MSWD = 1.6) for the amphibole cumulates. It is concluded that the Tongling adakitic rocks were formed by polybaric crystallization involving early high-pressure intracrustal fractional crystallization of cumulates comprising hornblende and clinopyroxene, and late low-pressure fractional crystallization of hornblende and plagioclase phenocrysts. The flat subduction of Pacific plate and its subsequent foundering during the Cretaceous may have triggered the generation of extensive adakitic magmas and lithospheric thinning in the Lower Yangtze Region. [ABSTRACT FROM AUTHOR]