Objective The nearly parallel N-S-trending rifts in southern Tibet represent the E-W extension of the Tibet Plateau. Most data which constrained the age of the extensional deformation come from isotopic dating of the...Objective The nearly parallel N-S-trending rifts in southern Tibet represent the E-W extension of the Tibet Plateau. Most data which constrained the age of the extensional deformation come from isotopic dating of the dikes probably related to the activity of the nearly N-S faulting and micas from hydrothermal activity and the low- temperature thermochronology of plateau uplift. Previous research shows that there are at least three different ideas about the age of the rifts： （1） older than 16-12 Ma, （2） 14- 10 Ma, and （3） 8-4 Ma （Fig. la）. For the old sedimentary strata represented the beginning of the rifting, the dating of the sediments helps to better define the initial rifting age.展开更多
The Tarim block,located in northwestern China,is one of the largest blocks in China.Precambrian rifts in the Tarim block control the evolution of Paleozoic rifts.On the basis of previous research by other authors,and ...The Tarim block,located in northwestern China,is one of the largest blocks in China.Precambrian rifts in the Tarim block control the evolution of Paleozoic rifts.On the basis of previous research by other authors,and also展开更多
On the basis of reprocessing 34 new two-dimensional spliced long sections(20,191 km) in the Tarim Basin, the deep structure features of the Tarim Basin were analyzed through interpreting 30,451 km of two-dimensional s...On the basis of reprocessing 34 new two-dimensional spliced long sections(20,191 km) in the Tarim Basin, the deep structure features of the Tarim Basin were analyzed through interpreting 30,451 km of two-dimensional seismic data and compiling basic maps. Seismic interpretation and geological analysis conclude that the Nanhua-Sinian strata are a set of rift-depression depositional systems according to their tectonic and depositional features. The rift valley formed in the Nanhua Period, and the transformation became weaker during the late Sinian Period, which eventually turned into depression. From bottom to top, the deposited strata include mafic igneous, tillite, mudstone, and dolomite. Three major depocenters developed inside this basin during the rift stage and are distributed in the eastern Tarim Basin, the Awati area, and the southwestern Tarim Basin. Among them, the rift in the eastern Tarim Basin strikes in the near east-west direction on the plane and coincides with the aeromagnetic anomaly belt. This represents a strong magnetic zone formed by upwelling basic volcanic rock along high, steep normal faults of the Nanhua Period. Controlled by the tectonic background, two types of sedimentary systems were developed in the rift stage and depression stage, showing two types of sequence features in the Sinian depositional stage. The Nanhua System appears as a wedge-shaped formation, with its bottom in unconformable contact with the base. The rifting event has a strong influence on the current tectonic units in the Tarim Basin, and affects the distribution of source rock in the Yuertus Formation and reservoir beds in the Xiaoerbulake Formation in Lower Cambrian, as well as the gypseous cap rock in Middle Cambrian. The distribution features of the rifts have important and realistic significance for determining the direction of oil and gas exploration in the deep strata of the Tarim Basin. Comprehensive analysis suggests that the Tazhong region is the most favorable zone, and the Kalpin-Bachu region is the optimal potential zone for exploring sub-salt oil and gas in deep Cambrian strata.展开更多
Based on seismic data,outcrop evidence,logging data and regional aeromagnetic data,the distribution of Nanhua–Sinian rifts in the southwestern Tarim Basin was analyzed,and on the basis of restoration of lithofacies p...Based on seismic data,outcrop evidence,logging data and regional aeromagnetic data,the distribution of Nanhua–Sinian rifts in the southwestern Tarim Basin was analyzed,and on the basis of restoration of lithofacies paleogeography in different periods of Neoproterozoic–Cambrian,the evolution model of the proto-type rift basin was discussed.The Neoproterozoic Rodinia supercontinent split event formed the trigeminal rift system at the edge and inside of the craton in the southwestern Tarim Basin located in the Kunlun piedmont and Maigaiti slope.The rift in Kunlun piedmont zone was distributed along the E-W direction and was the oceanic rift in the trigeminal rift system.Two decadent rifts in N-E strike developed in the Luonan and Yubei areas of Maigaiti slope,and the interior of the rifts were characterized by a composite graben-horst structure composed of multiple grabens and horsts.The Neoproterozoic–Cambrian proto-type basin evolution in the southwestern Tarim Basin can be divided into three stages:rift in the Nanhua,embryonic passive continental margin in the Sinian,and stable passive continental margin in the Cambrian.Despite the regional tectonic movements in the end of Nanhua and Sinian,the tectonic framework of the southwestern Tarim Basin had not changed significantly,the sedimentary center of Nanhua rift basin showed the characteristics of succession in the Sinian–Early Cambrian.The Nanhua rift in Kunlun piedmont evolved into a craton marginal depression during the Sinian–Early Paleozoic,while the Luonan decadent rift in the midsection of Maigaiti slope evolved into a sag inside platform in Early Cambrian,constituting the paleogeographic framework of"two paleouplifts and one sag"with the paleouplifts in east and west sides of the slope.The later evolution of the Luonan decadent rift in the midsection of the Maigaiti slope formed two sets of reservoir-forming assemblages,the Sinian and the Lower Cambrian ones,which are important exploration targets in future.展开更多
Continental rifting is one of the fundamental components in the Wilson cycle,and its comprehensive investigation is essential for understanding the geodynamic mechanisms of plate tectonics.Furthermore,continental rift...Continental rifting is one of the fundamental components in the Wilson cycle,and its comprehensive investigation is essential for understanding the geodynamic mechanisms of plate tectonics.Furthermore,continental rifts host significant mineral and hydrocarbon resources and also preserve valuable records of climatic environmental evolution.This study presents a systematic synthesis of their classification and magmatism after reviewing the research history of continental rifts.The formation and evolution of continental rifts are spatiotemporally associated with magmatic activity.Based on magmatic productivity,rifted margins that develop from successful continental rifts are categorized into different types,including magma-rich and magmapoor,with the intermediate category encompassing margins developed in active continental margin settings.Previous studies and systematically compiled data in this study indicate that distinct magmatic rock assemblages are characteristic of different rift types.Magma-rich rifts and rifted margins typically exhibit bimodal magmatism,including highly alkaline–silica poor alkaline rocks during the early rifting stage,alkalic basalt–trachyandesite–peralkaline rhyolite,transitional basalt and rhyolite during the evolutionary stage,and predominantly tholeiitic basalt during the final stage.Magma-poor rifted margins primarily consist of mafic rocks,including carbonatite and alkaline rocks during the initial rifting stage,followed by alkalic and tholeiitic basalts during the evolutionary stage.The lithospheric mantle in magma-poor rifted margins experienced extensive melt-induced metasomatism,making it an important research target for understanding continental rifting processes and magmatic evolution.In active continental margin rifts,magmatic rocks are dominated by bimodal magmatism,primarily encompassing the entire calcalkaline suite from basalt to rhyolite,along with minor alkalic basalt.During continental rifting,these magmatic processes effectively weaken the lithosphere,localize deformation,and ultimately facilitate the rifting progression to continental breakup.Further questions meriting attention include:(1)petrogenesis and geodynamics of magmatic rocks in continental rifts;(2)controlling factors for success or failure of continental rifting;(3)the nature of the ocean-continent transition and the process of transitioning from continental rifting to seafloor spreading;(4)controlling factors for the generation of magma-rich versus magma-poor rifted margins;and(5)the impact of continental rifting on climate change.Addressing these questions necessitates integrated approaches combining systematic geological,geochemical,and geophysical investigations of both modern and ancient rift systems with advanced techniques of numerical geodynamic modeling.展开更多
The lithosphere of the North China Craton(NCC)has experienced significant destruction and deformation since the Mesozoic,a notable feature of which is the widespread extensional structure and lithospheric thinning in ...The lithosphere of the North China Craton(NCC)has experienced significant destruction and deformation since the Mesozoic,a notable feature of which is the widespread extensional structure and lithospheric thinning in the eastern NCC.Since the thermo-rheological structure of the lithosphere is one of the main factors controlling these dynamic processes,a threedimensional thermo-rheological model of the present lithosphere in the NCC was developed based on a geophysical-petrological method using a variety of data,and its relationship with the extensional structures and the formation of rifts was further analyzed.Our results show that the western NCC is characterized by thick lithosphere,low Moho temperature(TMoho<600°C),as well as high lithospheric strength and mantle-crust strength ratio(Sm/Sc>1).The deformation of the western narrow rift is consistent with the localized deformation dominated by the strength of lithospheric mantle.On the other hand,the lithosphere in the eastern NCC is characterized by extensive thinning(with lithospheric thickness of about 80–110 km).However,the decrease of lithospheric strength is not uniform,with high strength(10×1012 Pa m)observed in some areas(such as the Bohai Bay Basin and Hehuai Basin).Most of the eastern lithosphere is characterized by high TMoho(600–750°C)and low Sm/Sc(<1),which is inconsistent with the widespread extensional structure in the eastern NCC.Incorporating results from palaeo-geothermal and petrological studies,we developed a thermo-rheological structure model of the lithosphere at different evolutionary stages of the NCC,and suggested that the eastern NCC had a significantly thinned and weakened lithosphere in the early stages of the formation of the rift,leading to a regional distributed extension deformation dominated by crustal strength,which eventually evolved into a series of wide rifts.However,the cooling and accretion of the lithosphere in the subsequent stages significantly increased the strength of the lithospheric mantle,resulting in the inconsistency between the present thermo-rheological structure of the lithosphere and the extensional structure formed in the past.展开更多
The Meso-Neoproterozoic strata are wildly distributed in North China Craton(NCC),of which Changchengian strata are most widely developed.Taking Changchengian strata in south margin of NCC as the study object,and combi...The Meso-Neoproterozoic strata are wildly distributed in North China Craton(NCC),of which Changchengian strata are most widely developed.Taking Changchengian strata in south margin of NCC as the study object,and combined with comprehensive analysis of isotopic chronology and petrology,it can be concluded that the Xiong'er rift is a plume rift which responds to breakup of Columbia supercontinent.Seismic data shows that Changchengian rifts are developed in the Qinshui Basin and the southern part of Ordos Basin covered by Phanerozoic strata,respectively are large-scale graben rifts and half-graben rifts.Aero magnetic data indicates that a NE-trending rift is developed in the west of the Xiong'er rift,and the Qinshui Basin rift is the extension of the north branch of the Xiong'er rift.The filling process of Changchengian rifts can be divided into four stages:the early rifting stage developing thick andesitic volcanic rocks,the late rifting stage developing large suite of coarse clastic sedimentary rocks,the depression stage developing fine clastic rocks,and the epeiric sea stage developing carbonate rocks.The dark argillaceous rocks are developed in Cuizhuang Formation and Chenjiajian Formation during the depression stage,and the black shale in Cuizhuang Formation is the effective source rocks.The bitume is filled in fractures of dolomite in Luoyukou Formation,as well as dissolution pores and large caves in Longjiayuan Formation.The argillaceous sandstone and muddy limestone of Lower Cambrian is the effective cap rocks,which can form an potential accumulation assemblage of Changchengian strata with underlying source rocks of Cuizhuang Formation and reservoirs of Luoyu Group,and this assemblage may be still effective at present.展开更多
Large-scale Danian-age(post-K/Pg boundary)Deccan magmatism is well known from the Mumbai metropolitan area,located in the structurally complex Panvel flexure zone along the western Indian rifted continental margin.Thi...Large-scale Danian-age(post-K/Pg boundary)Deccan magmatism is well known from the Mumbai metropolitan area,located in the structurally complex Panvel flexure zone along the western Indian rifted continental margin.This compositionally diverse late-Deccan magmatic suite contains subaerial tholeiitic lavas and dykes typical of the main Deccan province,with many features atypical of the Deccan,such as spilitic pillow lavas,“intertrappean”sediments(often containing considerable volcanic ash),rhyolitic lavas and tuffs,gabbro-granophyre intrusions,and trachyte intrusions containing alkali basalt enclaves.Most of these units,previously dated at 62.5 Ma to 61 Ma,are contemporaneous with or slightly postdate the 62.5 Ma India-Seychelles continental breakup and Panvel flexure formation.In the Dongri-Uttan area,two samples of a>50-m-thick,columnar-jointed rhyolite from the Darkhan Quarry and from a section behind the current Uttan Sagari Police Station have previously been dated at 62.6±0.6 Ma and 62.9±0.2 Ma(^(40)Ar/^(39)Ar,2r errors).New exposures reveal that these two statistically indistinguishable 40 Ar/39 Ar ages correspond to two distinct rhyolite units,separated by well-bedded silicic ash.The columnar rhyolites are microcrystalline,composed of quartz and alkali feldspar,with rare small(1–2 mm),altered feldspar phenocrysts,and no recognisable relict vitroclasts.Given the westerly structural dip,most of their lateral extent is submerged under the Arabian Sea,and we consider them to be possible flood rhyolite lavas.We interpret the ash beds,composed of pumice clasts and glass shards,as a low-grade(nonwelded)vitric ash,derived from a possibly distal Plinian eruption and deposited by fallout.The lavas and ash are peraluminous rhyolites.The lavas are Sr-Ba-poor and Rb-Zr-Nb-rich,and show“seagull-shaped”rare earth element patterns with deep negative europium anomalies.These crystal-poor lavas are“hot-dry-reduced”rhyolites typical of intraplate,continental rift and rifted margin settings.The very different high-field strength element contents of the lavas and the ash indicate compositionally distinct magma batches.The 62.5 Ma Dongri-Uttan sequence provides clear evidence for rapid silicic eruptions of effusive and explosive nature,alternating with each other and sourced from distinct magma chambers and eruptive vents.A newly identified,highly feldspar-phyric trachyte intrusion marks the last phase of magmatic activity in the area,corresponding with late-stage trachyte-syenite intrusions exposed in coastal western India and the Seychelles,and shows that the Mumbai rhyolites and trachytes form a compositional continuum.展开更多
Geological deformations are generally attributed to compressional, extensional and strike-slip processes. Since the breakup of Gondwana, torque deformation has been responsible for the current configuration of the wes...Geological deformations are generally attributed to compressional, extensional and strike-slip processes. Since the breakup of Gondwana, torque deformation has been responsible for the current configuration of the western coasts of Africa and the eastern shore of South America and the morphotectonic geometry of the rift basins of South America, conditioning the morphostructure of the Andean chain and the current geoforms of the foreland.展开更多
A-type rocks have drawn considerable attention in the past few decades due to their distinctive mineralogical and geochemical fingerprints and prospective utility for geodynamic reconstruction of the lithosphere.A com...A-type rocks have drawn considerable attention in the past few decades due to their distinctive mineralogical and geochemical fingerprints and prospective utility for geodynamic reconstruction of the lithosphere.A comprehensive study,involving zircon U-Pb geochronology,wholerock elemental and Sr-Nd-Pb isotopic geochemistry,was undertaken to elucidate the origin and evolutionary process for syenites from the Daguiping area in the North Daba mountains,South Qinling belt.The syenites revealed an Ordovician igneous crystallization age of 454.4±17 Ma,coeval with the neighboring mafic rocks.All samples show high SiO_(2),LREEs,and HFSEs(Nb,Ta,Zr and Hf)contents,with negative to slightly positive Eu(Eu/Eu^(*)=0.78-1.08)anomalies.The geochemical characteristics of the Daguiping syenites imply that they are of A_1-type magmatic affinity,which is confirmed by their high total alkali levels(8.57 wt.%-11.94 wt.%),Zr+Nb+Ce+Y contents(738.00 ppm-1734.78 ppm),and 10000×Ga/Al ratios(3.25-4.22),as well as low Y/Nb ratios(0.30-0.40).Our samples exhibit a wide range of initial^(87)Sr/^(86)Sr ratios of 0.701943 to 0.709802 and a narrow range of^(143)Nd/^(144)Nd ratios of 0.512205-0.512246 withε_(Nd)(t)values from+3.0 to+3.8.These rocks display(^(206)Pb/^(204)Pb)_(initial),(^(207)Pb/^(204)Pb)_(initial),and(^(208)Pb/^(204)Pb)_(initial)ratios range from 17.96 to 18.62,15.55 to 15.59,and 36.87 to 38.22,respectively.All of the isotopic data indicate that the syenites were essentially mantle-derived.A cogenetic source for the Daguiping syenites and coeval mafic rocks in the South Qinling belt is supported by their uniform Sr-Nd-Pb isotope data and linear major/trace elemental changes,with prolonged fractional crystallization considered as the essential mechanism for these geochemical discrepancies.Mass-balance and Rayleigh fractionation modeling estimate~85 vol%fractional crystallization involving amphibole,clinopyroxene,plagioclase,Kfeldspar,biotite,Fe-Ti oxide,and quartz,to reproduce the compositional varieties between a coeval mafic rock and the Daguiping syenites.The Daguiping syenites and associated alkaline rocks were likely related to a rifting episode triggered by asthenospheric upwelling,which led to the South Qinling detaching from the South China Block along the Mianlue suture during the Early Paleozoic.展开更多
Mantle plumes and surface erosion and sediment deposition affect the modes of continental lithospheric rupturing in extensional tectonic settings,modulating the evolution of rifting margins.However,their relative cont...Mantle plumes and surface erosion and sediment deposition affect the modes of continental lithospheric rupturing in extensional tectonic settings,modulating the evolution of rifting margins.However,their relative contributions to the overall evolution of rifting margins and possible roles in the formation of microcontinent are still elusive.Here,we use coupled geodynamic and surface processes numerical modeling to assess the extent to which surface processes may determine the formation of microcontinent during lithospheric stretching in presence or absence of a mantle plume underneath.Our modeling results indicate that fast extension rates and hillslope(i.e.,diffusion)erosion promote ridge jump events and therefore the formation of microcontinents.On the contrary,efficient fluvial erosion and far-reaching sediment transport(i.e.,stream power erosion)inhibits ridge jump events and the formation of microcontinents.The ridge jump event and overall evolution in our numerical models is consistent with the shift from the Mascarene Ridge to the Carlsberg Ridge that determined the formation of the Seychelles microcontinent.We therefore speculate that hillslope erosion,rather than fluvial erosion,was predominant during the formation of the Seychelles,a possible indication of overall dry local climate conditions.展开更多
As 1.5 million wildebeest pierce the dawn mist of the East African Rift Valley and the roar of lions merges with the cry of zebras beneath sprawling acacia trees,this land unveils life at its rawest-majestic and achin...As 1.5 million wildebeest pierce the dawn mist of the East African Rift Valley and the roar of lions merges with the cry of zebras beneath sprawling acacia trees,this land unveils life at its rawest-majestic and achingly fragile.展开更多
A wide northeast-trending belt of intraplate alkaline volcanism,exhibiting similar geochemical characteristics,stretches from the Eastern Atlantic Ocean to the Cenozoic rift system in Europe.Its formation is associate...A wide northeast-trending belt of intraplate alkaline volcanism,exhibiting similar geochemical characteristics,stretches from the Eastern Atlantic Ocean to the Cenozoic rift system in Europe.Its formation is associated with both passive and active mechanisms,but it remains a source of ongoing debate among geoscientists.Here,we show that seismic whole-mantle tomography models consistently identify two extensive low-velocity anomalies beneath the Canary Islands(CEAA)and Western-Central Europe(ECRA)at mid-mantle depths,merging near the core-mantle boundary.These low-velocity features are interpreted as two connected broad plumes originating from the top of the African LLSVP,likely feeding diapir-like upwellings in the upper mantle.The CEAA rises vertically,whereas the ECRA is tilted and dissipates at mantle transition zone depths,possibly due to the interaction with the cold Alpine subducted slab,which hinders its continuity at shallower depths.While plate-boundary forces are considered the primary drivers of rifting,the hypothesis that deep mantle plumes play a role in generating volcanic activity provides a compelling explanation for the European rift-related alkaline volcanism,supported by geological,geophysical,and geochemical evidence.展开更多
Taking the Wangfu fault depression in the Songliao Basin as an example,on the basis of seismic interpretation and drilling data analysis,the distribution of the basement faults was clarified,the fault activity periods...Taking the Wangfu fault depression in the Songliao Basin as an example,on the basis of seismic interpretation and drilling data analysis,the distribution of the basement faults was clarified,the fault activity periods of the coal-bearing formations were determined,and the fault systems were divided.Combined with the coal seam thickness and actual gas indication in logging,the controls of fault systems in the rift basin on the spatial distribution of coal and the occurrence of coal-rock gas were identified.The results show that the Wangfu fault depression is an asymmetrical graben formed under the control of basement reactivated strike-slip T-rupture,and contains coal-bearing formations and five sub-types of fault systems under three types.The horizontal extension strength,vertical activity strength and tectono-sedimentary filling difference of basement faults control vertical stratigraphic sequences,accumulation intensity,and accumulation frequency of coal seam in rift basin.The structural transfer zone formed during the segmented reactivation and growth of the basement faults controls the injection location of steep slope exogenous clasts.The filling effect induced by igneous intrusion accelerates the sediment filling process in the rift lacustrine area.The structural transfer zone and igneous intrusion together determine the preferential accumulation location of coal seams in the plane.The faults reactivated at the basement and newly formed during the rifting phase serve as pathways connecting to the gas source,affecting the enrichment degree of coal-rock gas.The vertical sealing of the faults was evaluated by using shale smear factor(SSF),and the evaluation criterion was established.It is indicated that the SSF is below 1.1 in major coal areas,indicating favorable preservation conditions for coal-rock gas.Based on the influence factors such as fault activity,segmentation and sealing,the coal-rock gas accumulation model of rift basin was established.展开更多
Previous studies have indicated that sediment gravity flow deposits developed in lacustrine active extensional rift basins are primarily influenced by tectonics and to a lesser extent by climate.Our present work revea...Previous studies have indicated that sediment gravity flow deposits developed in lacustrine active extensional rift basins are primarily influenced by tectonics and to a lesser extent by climate.Our present work reveals that climate can obscure the effect of tectonic subsidence by regulating sediment supply;conversely,tectonics can impede the sedimentary manifestation of climatic impacts.Here a case study has been presented to assess the impact of climate-modulated rapid lake-level rise and tectonic subsidence on the development of coarse-grained gravity flow deposits in the Dongying rift margin of the Bohai Bay Basin,eastern China.The lithofacies analysis reveals frequent bed amalgamation,abundant thick massive coarse-grained deposits,widespread cross bedding and plant fragments,and incomplete composite bed formed by high-energy erosion,indicating that the hyperpycnal flow is an important mechanism driving the deposition of these coarse-grained sediments.Detailed sequence stratigraphic analysis and sediment dispersal pattern suggest that the long-striped nearshore subaqueous fan systems induced by outburst-flood hyperpycnal flow distributed along the border fault,are primarily controlled by long-term tectonics,while the rapid rise of lake level driven by short-term climate change possibly intensifies seasonal flood-generated hyperpycnal flow occurrences and consequently promotes the basinal fan progradation.The maximum scale of these coarse-grained gravity flow deposits of the basinal fan systems are typically attained during the transgressive systems tract,which deviates from the classical sequence stratigraphic model.Furthermore,it presented a continuous transition from the proximal to the distal part,encompassing traction flows and turbidity currents during the periods of relatively stable tectonics.Nevertheless,gravel-rich debris flows appear to predominate the dispersion of coarse-grained sediments during periods characterized by intense tectonic activity.The coarse-grained gravity flow deposits in the lacustrine rift margin reported here,challenge the traditional beliefs:this study suggests that subaqueous deposits abundantly preserved in the transgressive setting.展开更多
The Cambrian Qiongzhusi Formation in the Sichuan Basin harbors significant potential for shale gas harvesting.However,systematic disparities in mineral composition and reservoir architecture have been observed between...The Cambrian Qiongzhusi Formation in the Sichuan Basin harbors significant potential for shale gas harvesting.However,systematic disparities in mineral composition and reservoir architecture have been observed between intra-and extra-trough reservoirs within the Deyang-Anyue Rift Trough.These variations were primarily determined by divergences in the sedimentary environments developed during the evolution of the rift trough,which were a main factor in fostering the heterogeneous distribution of shale gas enrichment found today.However,the genetic mechanisms that govern reservoir heterogeneity across distinct structural domains(intra-trough,trough margin,and extra-trough)remain poorly understood,particularly regarding the coupling relationships between depositional environments,reservoir characteristics,and gas-bearing properties.This study adopts a multidisciplinary approach to investigating this issue that integrates core analysis,well-log interpretations,and geochemical data.Through systematic comparisons conducted using X-ray diffraction mineralogy,organic carbon quantification,and spontaneous imbibition experiments,we characterize the mineral assemblages,organic geochemical signatures,and pore structures found across the three structural domains of the Deyang-Anyue Rift Trough.The key findings are as follows:(1)The depositional environment is the main influence on reservoir distribution and organic matter enrichment,with intra-trough shales exhibiting a higher abundance of organic matter than their trough-margin and extra-trough counterparts.(2)Enhanced brittleness in intra-trough zones correlates with the predominance of biogenic silica therein.(3)Synergistic organic-inorganic interactions govern pore system development.(4)Gas-bearing capacity is jointly determined by effective porosity and organic matter content.These findings establish the rift trough as a preferential exploration target,providing critical geological guidance for optimizing shale gas exploration strategies in the Cambrian Qiongzhusi Formation.展开更多
Lacustrine rift basins in China are characterized by pronounced structural segmentation,strong sedimentary heterogeneity,extensive fault-fracture development,and significant variability in thermal maturity and mobilit...Lacustrine rift basins in China are characterized by pronounced structural segmentation,strong sedimentary heterogeneity,extensive fault-fracture development,and significant variability in thermal maturity and mobility of shale oil.This study reviews the current status of exploration and development of shale oil in such basins and examines theoretical frameworks such as“binary enrichment”and source-reservoir configuration,with a focus on five key subjects:(1)sedimentation-diagenesis coupling mechanisms of fine-grained shale reservoir formation;(2)dynamic diagenetic evolution and hydrocarbon occurrence mechanisms of organic-rich shale;(3)dominant controls and evaluation methods for shale oil enrichment;(4)fracturing mechanisms of organic-rich shale and simulation of artificial fracture networks;and(5)flow mechanisms and effective development strategies for shale oil.Integrated analysis suggests that two major scientific challenges must be addressed:the coupled evolution of fine-grained sedimentation,differential diagenesis,and hydrocarbon generation under tectonic influence and its control on shale oil occurrence and enrichment;and multi-scale,multiphase flow mechanisms and three-dimensional development strategies for lacustrine shale oil in complex fault blocks.In response to current exploration and development bottlenecks,future research will be conducted primarily to:(1)deeply understand organic-inorganic interactions and reservoir formation mechanisms in organic-rich shales,and clarify the influence of high-frequency sequence evolution and diagenetic fluids on reservoir space;(2)elucidate the dynamic processes of hydrocarbon generation,expulsion,and retention across different lithofacies,and quantify their relationship with thermal maturity,including the conditions for the formation of self-sealing systems;(3)develop a geologically adaptive,data-and intelligence-driven shale oil classification and grading evaluation system of shale oil;(4)reveal artificial fracture propagation pattern and optimize physical field coupled fracturing technologies for complex lithofacies assemblages;and(5)overcome challenges in multi-scale geological modeling and multiphase flow characterization,and establish advanced numerical simulation methodologies.展开更多
Distinguishing high-grade mafic-ultramafic rocks originally crystallized from within-plate basaltic magmatism is challenging and crucial because the chemical composition of the igneous rocks has been modified during h...Distinguishing high-grade mafic-ultramafic rocks originally crystallized from within-plate basaltic magmatism is challenging and crucial because the chemical composition of the igneous rocks has been modified during high-grade metamorphism,causing misidentification of the characters of the parental magma.Proterozoic metamorphosed mafic dykes occur throughout the Chhotanagpur Gneissic Complex(CGC)of eastern Indian shield.The E-W trending mafic dykes from the Saltora area in the southeastern CGC underwent metamorphism in two episodes:M1(650 MPa;770℃)and M2(300 MPa;744℃).The metamafics are enriched in LILE,depleted in HFSE,and display strong fractionation of LREE,nearly flat HREE patterns in a chondrite-normalized REE diagram,and show tholeiitic differentiation trend.Their geochemical affinity is towards rift-related,continental within-plate basalts.About 7%–10%melting of the carbonated spinel-peridotite sub-continental lithospheric mantle(SCLM)produced the parental mafic magma.The pre-existing SCLM was metasomatized by slab-derived fluid during the previous subduction.The upwelling of the asthenosphere in a post-collisional tectonic setting caused E-W trending fractures,lithospheric thinning,and gravitational collapse.These dykes were emplaced during crustal extension around 1070 Ma.The remarkable geochemical similarity between the mafic dykes of Saltora and Dhanbad,the ca.1096 Ma Mahoba(Bundelkhand craton),and the ca.1070 Ma Alcurra mafic dykes in Australia supports a genetic link.展开更多
Based on a large amount of basic research and experimental analysis data from Shengli Oilfield,Bohai Bay Basin,guided by the theory of whole petroleum system,the distribution of sedimentary systems,the distribution an...Based on a large amount of basic research and experimental analysis data from Shengli Oilfield,Bohai Bay Basin,guided by the theory of whole petroleum system,the distribution of sedimentary systems,the distribution and hydrocarbon generation and expulsion process of source rocks,the variation of reservoir properties,and the control of fracture systems on hydrocarbon accumulation in the Paleogene of the Jiyang Depression,Boahai Bay Basin,were systematically analyzed,and the geological characteristics of the whole petroleum system in the rift basin were identified.Taking the Dongying Sag as an example,combined with the distribution of discovered conventional,tight,and shale oil/gas,a hydrocarbon accumulation model of the fault-controlled whole petroleum system in rift basin was proposed,and the distribution patterns of conventional and unconventional oil and gas reservoirs in large geological bodies horizontally and vertically were clarified.The research results show that paleoclimate and tectonic cycles control the orderly distribution of the Paleogene sedimentary system in the Jiyang Depression,the multi-stage source rocks provide sufficient material basis for in-situ shale oil/gas accumulation and other hydrocarbon migration and accumulation,the changes in reservoir properties control the dynamic threshold of hydrocarbon accumulation,and the combination of faults and fractures at different stages controls hydrocarbon migration and accumulation,and in-situ retention and accumulation of shale oil/gas,making the whole petroleum system in the rift basin associated,segmented and abrupt.The above elements are configured to form a composite whole petroleum system controlled by faults in the Paleogene of the Jiyang Depression.Moreover,under the control of hydrocarbon accumulation dynamics,a whole petroleum system can be divided into conventional subsystem and unconventional subsystem,with shale oil,tight oil and conventional oil in an orderly distribution in horizontal and vertical directions.This systematic understanding is referential for analyzing the whole petroleum system in continental rift basins in eastern China.展开更多
基金supported by the National Natural Science Foundation of China(grant No.41571013)Project of China Geological Survey(grant No.12120114002101)
文摘Objective The nearly parallel N-S-trending rifts in southern Tibet represent the E-W extension of the Tibet Plateau. Most data which constrained the age of the extensional deformation come from isotopic dating of the dikes probably related to the activity of the nearly N-S faulting and micas from hydrothermal activity and the low- temperature thermochronology of plateau uplift. Previous research shows that there are at least three different ideas about the age of the rifts： （1） older than 16-12 Ma, （2） 14- 10 Ma, and （3） 8-4 Ma （Fig. la）. For the old sedimentary strata represented the beginning of the rifting, the dating of the sediments helps to better define the initial rifting age.
基金supported by funds from the National Natural Science Foundation of China (Grant No. 41530207)State Key Projects (2014A0213 and 2016ZX05051004)
文摘The Tarim block,located in northwestern China,is one of the largest blocks in China.Precambrian rifts in the Tarim block control the evolution of Paleozoic rifts.On the basis of previous research by other authors,and also
基金the projects of the China Geological Survey Program(Grant No.DD20160169.12120115001801,1211302108022 and DD20190708).
文摘On the basis of reprocessing 34 new two-dimensional spliced long sections(20,191 km) in the Tarim Basin, the deep structure features of the Tarim Basin were analyzed through interpreting 30,451 km of two-dimensional seismic data and compiling basic maps. Seismic interpretation and geological analysis conclude that the Nanhua-Sinian strata are a set of rift-depression depositional systems according to their tectonic and depositional features. The rift valley formed in the Nanhua Period, and the transformation became weaker during the late Sinian Period, which eventually turned into depression. From bottom to top, the deposited strata include mafic igneous, tillite, mudstone, and dolomite. Three major depocenters developed inside this basin during the rift stage and are distributed in the eastern Tarim Basin, the Awati area, and the southwestern Tarim Basin. Among them, the rift in the eastern Tarim Basin strikes in the near east-west direction on the plane and coincides with the aeromagnetic anomaly belt. This represents a strong magnetic zone formed by upwelling basic volcanic rock along high, steep normal faults of the Nanhua Period. Controlled by the tectonic background, two types of sedimentary systems were developed in the rift stage and depression stage, showing two types of sequence features in the Sinian depositional stage. The Nanhua System appears as a wedge-shaped formation, with its bottom in unconformable contact with the base. The rifting event has a strong influence on the current tectonic units in the Tarim Basin, and affects the distribution of source rock in the Yuertus Formation and reservoir beds in the Xiaoerbulake Formation in Lower Cambrian, as well as the gypseous cap rock in Middle Cambrian. The distribution features of the rifts have important and realistic significance for determining the direction of oil and gas exploration in the deep strata of the Tarim Basin. Comprehensive analysis suggests that the Tazhong region is the most favorable zone, and the Kalpin-Bachu region is the optimal potential zone for exploring sub-salt oil and gas in deep Cambrian strata.
基金Supported by China National Science and Technology Major Project(2016ZX05004-003)the PetroChina Science and Technology Major Project(kt2018-02-04)
文摘Based on seismic data,outcrop evidence,logging data and regional aeromagnetic data,the distribution of Nanhua–Sinian rifts in the southwestern Tarim Basin was analyzed,and on the basis of restoration of lithofacies paleogeography in different periods of Neoproterozoic–Cambrian,the evolution model of the proto-type rift basin was discussed.The Neoproterozoic Rodinia supercontinent split event formed the trigeminal rift system at the edge and inside of the craton in the southwestern Tarim Basin located in the Kunlun piedmont and Maigaiti slope.The rift in Kunlun piedmont zone was distributed along the E-W direction and was the oceanic rift in the trigeminal rift system.Two decadent rifts in N-E strike developed in the Luonan and Yubei areas of Maigaiti slope,and the interior of the rifts were characterized by a composite graben-horst structure composed of multiple grabens and horsts.The Neoproterozoic–Cambrian proto-type basin evolution in the southwestern Tarim Basin can be divided into three stages:rift in the Nanhua,embryonic passive continental margin in the Sinian,and stable passive continental margin in the Cambrian.Despite the regional tectonic movements in the end of Nanhua and Sinian,the tectonic framework of the southwestern Tarim Basin had not changed significantly,the sedimentary center of Nanhua rift basin showed the characteristics of succession in the Sinian–Early Cambrian.The Nanhua rift in Kunlun piedmont evolved into a craton marginal depression during the Sinian–Early Paleozoic,while the Luonan decadent rift in the midsection of Maigaiti slope evolved into a sag inside platform in Early Cambrian,constituting the paleogeographic framework of"two paleouplifts and one sag"with the paleouplifts in east and west sides of the slope.The later evolution of the Luonan decadent rift in the midsection of the Maigaiti slope formed two sets of reservoir-forming assemblages,the Sinian and the Lower Cambrian ones,which are important exploration targets in future.
基金supported by the Strategic Priority Research Program(A)of the Chinese Academy of Sciences(Grant No.XDA0430102)the Deep Earth Probe and Mineral Resources Exploration(Grant No.2024ZD1001103)。
文摘Continental rifting is one of the fundamental components in the Wilson cycle,and its comprehensive investigation is essential for understanding the geodynamic mechanisms of plate tectonics.Furthermore,continental rifts host significant mineral and hydrocarbon resources and also preserve valuable records of climatic environmental evolution.This study presents a systematic synthesis of their classification and magmatism after reviewing the research history of continental rifts.The formation and evolution of continental rifts are spatiotemporally associated with magmatic activity.Based on magmatic productivity,rifted margins that develop from successful continental rifts are categorized into different types,including magma-rich and magmapoor,with the intermediate category encompassing margins developed in active continental margin settings.Previous studies and systematically compiled data in this study indicate that distinct magmatic rock assemblages are characteristic of different rift types.Magma-rich rifts and rifted margins typically exhibit bimodal magmatism,including highly alkaline–silica poor alkaline rocks during the early rifting stage,alkalic basalt–trachyandesite–peralkaline rhyolite,transitional basalt and rhyolite during the evolutionary stage,and predominantly tholeiitic basalt during the final stage.Magma-poor rifted margins primarily consist of mafic rocks,including carbonatite and alkaline rocks during the initial rifting stage,followed by alkalic and tholeiitic basalts during the evolutionary stage.The lithospheric mantle in magma-poor rifted margins experienced extensive melt-induced metasomatism,making it an important research target for understanding continental rifting processes and magmatic evolution.In active continental margin rifts,magmatic rocks are dominated by bimodal magmatism,primarily encompassing the entire calcalkaline suite from basalt to rhyolite,along with minor alkalic basalt.During continental rifting,these magmatic processes effectively weaken the lithosphere,localize deformation,and ultimately facilitate the rifting progression to continental breakup.Further questions meriting attention include:(1)petrogenesis and geodynamics of magmatic rocks in continental rifts;(2)controlling factors for success or failure of continental rifting;(3)the nature of the ocean-continent transition and the process of transitioning from continental rifting to seafloor spreading;(4)controlling factors for the generation of magma-rich versus magma-poor rifted margins;and(5)the impact of continental rifting on climate change.Addressing these questions necessitates integrated approaches combining systematic geological,geochemical,and geophysical investigations of both modern and ancient rift systems with advanced techniques of numerical geodynamic modeling.
基金supported by the National Natural Science Foundation of China(Grant Nos.41731072,41574095)the National Key R&D Program of China(Grant No.2017YFC1500305)Most figures were prepared with the Generic Mapping Tools(Wessel and Smith,1998)。
文摘The lithosphere of the North China Craton(NCC)has experienced significant destruction and deformation since the Mesozoic,a notable feature of which is the widespread extensional structure and lithospheric thinning in the eastern NCC.Since the thermo-rheological structure of the lithosphere is one of the main factors controlling these dynamic processes,a threedimensional thermo-rheological model of the present lithosphere in the NCC was developed based on a geophysical-petrological method using a variety of data,and its relationship with the extensional structures and the formation of rifts was further analyzed.Our results show that the western NCC is characterized by thick lithosphere,low Moho temperature(TMoho<600°C),as well as high lithospheric strength and mantle-crust strength ratio(Sm/Sc>1).The deformation of the western narrow rift is consistent with the localized deformation dominated by the strength of lithospheric mantle.On the other hand,the lithosphere in the eastern NCC is characterized by extensive thinning(with lithospheric thickness of about 80–110 km).However,the decrease of lithospheric strength is not uniform,with high strength(10×1012 Pa m)observed in some areas(such as the Bohai Bay Basin and Hehuai Basin).Most of the eastern lithosphere is characterized by high TMoho(600–750°C)and low Sm/Sc(<1),which is inconsistent with the widespread extensional structure in the eastern NCC.Incorporating results from palaeo-geothermal and petrological studies,we developed a thermo-rheological structure model of the lithosphere at different evolutionary stages of the NCC,and suggested that the eastern NCC had a significantly thinned and weakened lithosphere in the early stages of the formation of the rift,leading to a regional distributed extension deformation dominated by crustal strength,which eventually evolved into a series of wide rifts.However,the cooling and accretion of the lithosphere in the subsequent stages significantly increased the strength of the lithospheric mantle,resulting in the inconsistency between the present thermo-rheological structure of the lithosphere and the extensional structure formed in the past.
基金The work was supported by the National Key Research and Development Program of China(No.2016YFC0601002)Frontier Basic Research Program of PetroChina Research Institute of Petroleum Exploration and Development(No.2015yj-09).
文摘The Meso-Neoproterozoic strata are wildly distributed in North China Craton(NCC),of which Changchengian strata are most widely developed.Taking Changchengian strata in south margin of NCC as the study object,and combined with comprehensive analysis of isotopic chronology and petrology,it can be concluded that the Xiong'er rift is a plume rift which responds to breakup of Columbia supercontinent.Seismic data shows that Changchengian rifts are developed in the Qinshui Basin and the southern part of Ordos Basin covered by Phanerozoic strata,respectively are large-scale graben rifts and half-graben rifts.Aero magnetic data indicates that a NE-trending rift is developed in the west of the Xiong'er rift,and the Qinshui Basin rift is the extension of the north branch of the Xiong'er rift.The filling process of Changchengian rifts can be divided into four stages:the early rifting stage developing thick andesitic volcanic rocks,the late rifting stage developing large suite of coarse clastic sedimentary rocks,the depression stage developing fine clastic rocks,and the epeiric sea stage developing carbonate rocks.The dark argillaceous rocks are developed in Cuizhuang Formation and Chenjiajian Formation during the depression stage,and the black shale in Cuizhuang Formation is the effective source rocks.The bitume is filled in fractures of dolomite in Luoyukou Formation,as well as dissolution pores and large caves in Longjiayuan Formation.The argillaceous sandstone and muddy limestone of Lower Cambrian is the effective cap rocks,which can form an potential accumulation assemblage of Changchengian strata with underlying source rocks of Cuizhuang Formation and reservoirs of Luoyu Group,and this assemblage may be still effective at present.
基金supported by the research award project RI/0220-10000618-001 to Sheth from the Industrial Research and Consultancy Centre(IRCC)IIT Bombay.Shekhar and Astha were supported by Prime Minister’s Research Fellowships(PMRF,File Nos.1303100 and 1303103,respectively)+4 种基金Naik was initially supported by an IIT Bombay Institute Post-Doctoral Fellowship(File No.HR-1(HRM-1)/Rect/33/2022/20003002)subsequently by a Goa State Research Foundation Post-doctoral Fellowship(File No.PDF2024003)We express our sincere gratitude to Prof.N.Prabhakar for kindly granting us access to the WD-XRF spectrometry facility(SIP ProjectWBS Code:IN/22-1111039E-01)the ICP-MS facility,and the SERB-funded EPMA National Facility(IRPHA Grant No.IR/S4/ESF-16/2009(G))in the Department of Earth Sciences,IIT Bombay.
文摘Large-scale Danian-age(post-K/Pg boundary)Deccan magmatism is well known from the Mumbai metropolitan area,located in the structurally complex Panvel flexure zone along the western Indian rifted continental margin.This compositionally diverse late-Deccan magmatic suite contains subaerial tholeiitic lavas and dykes typical of the main Deccan province,with many features atypical of the Deccan,such as spilitic pillow lavas,“intertrappean”sediments(often containing considerable volcanic ash),rhyolitic lavas and tuffs,gabbro-granophyre intrusions,and trachyte intrusions containing alkali basalt enclaves.Most of these units,previously dated at 62.5 Ma to 61 Ma,are contemporaneous with or slightly postdate the 62.5 Ma India-Seychelles continental breakup and Panvel flexure formation.In the Dongri-Uttan area,two samples of a>50-m-thick,columnar-jointed rhyolite from the Darkhan Quarry and from a section behind the current Uttan Sagari Police Station have previously been dated at 62.6±0.6 Ma and 62.9±0.2 Ma(^(40)Ar/^(39)Ar,2r errors).New exposures reveal that these two statistically indistinguishable 40 Ar/39 Ar ages correspond to two distinct rhyolite units,separated by well-bedded silicic ash.The columnar rhyolites are microcrystalline,composed of quartz and alkali feldspar,with rare small(1–2 mm),altered feldspar phenocrysts,and no recognisable relict vitroclasts.Given the westerly structural dip,most of their lateral extent is submerged under the Arabian Sea,and we consider them to be possible flood rhyolite lavas.We interpret the ash beds,composed of pumice clasts and glass shards,as a low-grade(nonwelded)vitric ash,derived from a possibly distal Plinian eruption and deposited by fallout.The lavas and ash are peraluminous rhyolites.The lavas are Sr-Ba-poor and Rb-Zr-Nb-rich,and show“seagull-shaped”rare earth element patterns with deep negative europium anomalies.These crystal-poor lavas are“hot-dry-reduced”rhyolites typical of intraplate,continental rift and rifted margin settings.The very different high-field strength element contents of the lavas and the ash indicate compositionally distinct magma batches.The 62.5 Ma Dongri-Uttan sequence provides clear evidence for rapid silicic eruptions of effusive and explosive nature,alternating with each other and sourced from distinct magma chambers and eruptive vents.A newly identified,highly feldspar-phyric trachyte intrusion marks the last phase of magmatic activity in the area,corresponding with late-stage trachyte-syenite intrusions exposed in coastal western India and the Seychelles,and shows that the Mumbai rhyolites and trachytes form a compositional continuum.
文摘Geological deformations are generally attributed to compressional, extensional and strike-slip processes. Since the breakup of Gondwana, torque deformation has been responsible for the current configuration of the western coasts of Africa and the eastern shore of South America and the morphotectonic geometry of the rift basins of South America, conditioning the morphostructure of the Andean chain and the current geoforms of the foreland.
基金jointly supported by the Natural Science Foundation of China(Nos.42172056,41772052)。
文摘A-type rocks have drawn considerable attention in the past few decades due to their distinctive mineralogical and geochemical fingerprints and prospective utility for geodynamic reconstruction of the lithosphere.A comprehensive study,involving zircon U-Pb geochronology,wholerock elemental and Sr-Nd-Pb isotopic geochemistry,was undertaken to elucidate the origin and evolutionary process for syenites from the Daguiping area in the North Daba mountains,South Qinling belt.The syenites revealed an Ordovician igneous crystallization age of 454.4±17 Ma,coeval with the neighboring mafic rocks.All samples show high SiO_(2),LREEs,and HFSEs(Nb,Ta,Zr and Hf)contents,with negative to slightly positive Eu(Eu/Eu^(*)=0.78-1.08)anomalies.The geochemical characteristics of the Daguiping syenites imply that they are of A_1-type magmatic affinity,which is confirmed by their high total alkali levels(8.57 wt.%-11.94 wt.%),Zr+Nb+Ce+Y contents(738.00 ppm-1734.78 ppm),and 10000×Ga/Al ratios(3.25-4.22),as well as low Y/Nb ratios(0.30-0.40).Our samples exhibit a wide range of initial^(87)Sr/^(86)Sr ratios of 0.701943 to 0.709802 and a narrow range of^(143)Nd/^(144)Nd ratios of 0.512205-0.512246 withε_(Nd)(t)values from+3.0 to+3.8.These rocks display(^(206)Pb/^(204)Pb)_(initial),(^(207)Pb/^(204)Pb)_(initial),and(^(208)Pb/^(204)Pb)_(initial)ratios range from 17.96 to 18.62,15.55 to 15.59,and 36.87 to 38.22,respectively.All of the isotopic data indicate that the syenites were essentially mantle-derived.A cogenetic source for the Daguiping syenites and coeval mafic rocks in the South Qinling belt is supported by their uniform Sr-Nd-Pb isotope data and linear major/trace elemental changes,with prolonged fractional crystallization considered as the essential mechanism for these geochemical discrepancies.Mass-balance and Rayleigh fractionation modeling estimate~85 vol%fractional crystallization involving amphibole,clinopyroxene,plagioclase,Kfeldspar,biotite,Fe-Ti oxide,and quartz,to reproduce the compositional varieties between a coeval mafic rock and the Daguiping syenites.The Daguiping syenites and associated alkaline rocks were likely related to a rifting episode triggered by asthenospheric upwelling,which led to the South Qinling detaching from the South China Block along the Mianlue suture during the Early Paleozoic.
基金financially supported by the National Science Foundation of China(No.41920104010)the China Postdoctoral Science Foundation(No.2024M762767)+3 种基金the Fundamental Research Funds for the Central University,CHD(No.300102264104)by the Postdoctoral Fellowship Program of CPSF(No.GZC20241444)supported by Fondazione Cariplo and Fondazione CDP(No.2022-1546_001)by the Italian Ministry of Education,MUR(Project Dipartimenti di Eccellenza,TECLA,Department of Earth and Environmental Sciences,University of Milano-Bicocca)。
文摘Mantle plumes and surface erosion and sediment deposition affect the modes of continental lithospheric rupturing in extensional tectonic settings,modulating the evolution of rifting margins.However,their relative contributions to the overall evolution of rifting margins and possible roles in the formation of microcontinent are still elusive.Here,we use coupled geodynamic and surface processes numerical modeling to assess the extent to which surface processes may determine the formation of microcontinent during lithospheric stretching in presence or absence of a mantle plume underneath.Our modeling results indicate that fast extension rates and hillslope(i.e.,diffusion)erosion promote ridge jump events and therefore the formation of microcontinents.On the contrary,efficient fluvial erosion and far-reaching sediment transport(i.e.,stream power erosion)inhibits ridge jump events and the formation of microcontinents.The ridge jump event and overall evolution in our numerical models is consistent with the shift from the Mascarene Ridge to the Carlsberg Ridge that determined the formation of the Seychelles microcontinent.We therefore speculate that hillslope erosion,rather than fluvial erosion,was predominant during the formation of the Seychelles,a possible indication of overall dry local climate conditions.
文摘As 1.5 million wildebeest pierce the dawn mist of the East African Rift Valley and the roar of lions merges with the cry of zebras beneath sprawling acacia trees,this land unveils life at its rawest-majestic and achingly fragile.
基金supported by grant D86-RALMI23CIVIE_01 awarded by the Italian Ministry of University and Research under the Program for Young Researchers“Rita Levi Montalcini”.
文摘A wide northeast-trending belt of intraplate alkaline volcanism,exhibiting similar geochemical characteristics,stretches from the Eastern Atlantic Ocean to the Cenozoic rift system in Europe.Its formation is associated with both passive and active mechanisms,but it remains a source of ongoing debate among geoscientists.Here,we show that seismic whole-mantle tomography models consistently identify two extensive low-velocity anomalies beneath the Canary Islands(CEAA)and Western-Central Europe(ECRA)at mid-mantle depths,merging near the core-mantle boundary.These low-velocity features are interpreted as two connected broad plumes originating from the top of the African LLSVP,likely feeding diapir-like upwellings in the upper mantle.The CEAA rises vertically,whereas the ECRA is tilted and dissipates at mantle transition zone depths,possibly due to the interaction with the cold Alpine subducted slab,which hinders its continuity at shallower depths.While plate-boundary forces are considered the primary drivers of rifting,the hypothesis that deep mantle plumes play a role in generating volcanic activity provides a compelling explanation for the European rift-related alkaline volcanism,supported by geological,geophysical,and geochemical evidence.
基金Supported by the National Natural Science Foundation of China(42472190)Chongqing Natural Science Foundation Innovation and Development Joint Fund Project(CSTB2022NSCQ-LZX0020)Chongqing Talent Innovation and Entrepreneurship Leading Talent Project(0255-19230101042)。
文摘Taking the Wangfu fault depression in the Songliao Basin as an example,on the basis of seismic interpretation and drilling data analysis,the distribution of the basement faults was clarified,the fault activity periods of the coal-bearing formations were determined,and the fault systems were divided.Combined with the coal seam thickness and actual gas indication in logging,the controls of fault systems in the rift basin on the spatial distribution of coal and the occurrence of coal-rock gas were identified.The results show that the Wangfu fault depression is an asymmetrical graben formed under the control of basement reactivated strike-slip T-rupture,and contains coal-bearing formations and five sub-types of fault systems under three types.The horizontal extension strength,vertical activity strength and tectono-sedimentary filling difference of basement faults control vertical stratigraphic sequences,accumulation intensity,and accumulation frequency of coal seam in rift basin.The structural transfer zone formed during the segmented reactivation and growth of the basement faults controls the injection location of steep slope exogenous clasts.The filling effect induced by igneous intrusion accelerates the sediment filling process in the rift lacustrine area.The structural transfer zone and igneous intrusion together determine the preferential accumulation location of coal seams in the plane.The faults reactivated at the basement and newly formed during the rifting phase serve as pathways connecting to the gas source,affecting the enrichment degree of coal-rock gas.The vertical sealing of the faults was evaluated by using shale smear factor(SSF),and the evaluation criterion was established.It is indicated that the SSF is below 1.1 in major coal areas,indicating favorable preservation conditions for coal-rock gas.Based on the influence factors such as fault activity,segmentation and sealing,the coal-rock gas accumulation model of rift basin was established.
基金supported by the National Natural Science Foundation of China(Nos.42172109,41872113,42172108)China National Petroleum Corporation-China University of Petroleum(Beijing)strategic cooperation science and technology project(ZLZX2020-02)+2 种基金Science Foundation of China University of Petroleum(Beijing)(Nos.2462020BJRC002,2462020YXZZ020)Natural Science Foundation of Chongqing(CSTB2022NSCQ-MSX1166)Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN202201511).
文摘Previous studies have indicated that sediment gravity flow deposits developed in lacustrine active extensional rift basins are primarily influenced by tectonics and to a lesser extent by climate.Our present work reveals that climate can obscure the effect of tectonic subsidence by regulating sediment supply;conversely,tectonics can impede the sedimentary manifestation of climatic impacts.Here a case study has been presented to assess the impact of climate-modulated rapid lake-level rise and tectonic subsidence on the development of coarse-grained gravity flow deposits in the Dongying rift margin of the Bohai Bay Basin,eastern China.The lithofacies analysis reveals frequent bed amalgamation,abundant thick massive coarse-grained deposits,widespread cross bedding and plant fragments,and incomplete composite bed formed by high-energy erosion,indicating that the hyperpycnal flow is an important mechanism driving the deposition of these coarse-grained sediments.Detailed sequence stratigraphic analysis and sediment dispersal pattern suggest that the long-striped nearshore subaqueous fan systems induced by outburst-flood hyperpycnal flow distributed along the border fault,are primarily controlled by long-term tectonics,while the rapid rise of lake level driven by short-term climate change possibly intensifies seasonal flood-generated hyperpycnal flow occurrences and consequently promotes the basinal fan progradation.The maximum scale of these coarse-grained gravity flow deposits of the basinal fan systems are typically attained during the transgressive systems tract,which deviates from the classical sequence stratigraphic model.Furthermore,it presented a continuous transition from the proximal to the distal part,encompassing traction flows and turbidity currents during the periods of relatively stable tectonics.Nevertheless,gravel-rich debris flows appear to predominate the dispersion of coarse-grained sediments during periods characterized by intense tectonic activity.The coarse-grained gravity flow deposits in the lacustrine rift margin reported here,challenge the traditional beliefs:this study suggests that subaqueous deposits abundantly preserved in the transgressive setting.
基金supported by the National Natural Science Foundation of China(No.24A20592).
文摘The Cambrian Qiongzhusi Formation in the Sichuan Basin harbors significant potential for shale gas harvesting.However,systematic disparities in mineral composition and reservoir architecture have been observed between intra-and extra-trough reservoirs within the Deyang-Anyue Rift Trough.These variations were primarily determined by divergences in the sedimentary environments developed during the evolution of the rift trough,which were a main factor in fostering the heterogeneous distribution of shale gas enrichment found today.However,the genetic mechanisms that govern reservoir heterogeneity across distinct structural domains(intra-trough,trough margin,and extra-trough)remain poorly understood,particularly regarding the coupling relationships between depositional environments,reservoir characteristics,and gas-bearing properties.This study adopts a multidisciplinary approach to investigating this issue that integrates core analysis,well-log interpretations,and geochemical data.Through systematic comparisons conducted using X-ray diffraction mineralogy,organic carbon quantification,and spontaneous imbibition experiments,we characterize the mineral assemblages,organic geochemical signatures,and pore structures found across the three structural domains of the Deyang-Anyue Rift Trough.The key findings are as follows:(1)The depositional environment is the main influence on reservoir distribution and organic matter enrichment,with intra-trough shales exhibiting a higher abundance of organic matter than their trough-margin and extra-trough counterparts.(2)Enhanced brittleness in intra-trough zones correlates with the predominance of biogenic silica therein.(3)Synergistic organic-inorganic interactions govern pore system development.(4)Gas-bearing capacity is jointly determined by effective porosity and organic matter content.These findings establish the rift trough as a preferential exploration target,providing critical geological guidance for optimizing shale gas exploration strategies in the Cambrian Qiongzhusi Formation.
基金Supported by the National Natural Science Foundation of China(U24B6002)National Science and Technology Major Project(2024ZD14001)Project of the Sinopec Science and Technology Department(P25196,P24207).
文摘Lacustrine rift basins in China are characterized by pronounced structural segmentation,strong sedimentary heterogeneity,extensive fault-fracture development,and significant variability in thermal maturity and mobility of shale oil.This study reviews the current status of exploration and development of shale oil in such basins and examines theoretical frameworks such as“binary enrichment”and source-reservoir configuration,with a focus on five key subjects:(1)sedimentation-diagenesis coupling mechanisms of fine-grained shale reservoir formation;(2)dynamic diagenetic evolution and hydrocarbon occurrence mechanisms of organic-rich shale;(3)dominant controls and evaluation methods for shale oil enrichment;(4)fracturing mechanisms of organic-rich shale and simulation of artificial fracture networks;and(5)flow mechanisms and effective development strategies for shale oil.Integrated analysis suggests that two major scientific challenges must be addressed:the coupled evolution of fine-grained sedimentation,differential diagenesis,and hydrocarbon generation under tectonic influence and its control on shale oil occurrence and enrichment;and multi-scale,multiphase flow mechanisms and three-dimensional development strategies for lacustrine shale oil in complex fault blocks.In response to current exploration and development bottlenecks,future research will be conducted primarily to:(1)deeply understand organic-inorganic interactions and reservoir formation mechanisms in organic-rich shales,and clarify the influence of high-frequency sequence evolution and diagenetic fluids on reservoir space;(2)elucidate the dynamic processes of hydrocarbon generation,expulsion,and retention across different lithofacies,and quantify their relationship with thermal maturity,including the conditions for the formation of self-sealing systems;(3)develop a geologically adaptive,data-and intelligence-driven shale oil classification and grading evaluation system of shale oil;(4)reveal artificial fracture propagation pattern and optimize physical field coupled fracturing technologies for complex lithofacies assemblages;and(5)overcome challenges in multi-scale geological modeling and multiphase flow characterization,and establish advanced numerical simulation methodologies.
基金funded by a major research project grant from the UGC (F.-43-367/2014(SR)) and teachers’ research grant from the University of Calcutta awarded to Dr Bapi GoswamiDST-sponsored Women Scientist scheme-A (SR/WOS-A/EA-47/2018 (G) dated 06.05.2019) awarded to Ms. Poulami Roy is highly acknowledged for their financial help
文摘Distinguishing high-grade mafic-ultramafic rocks originally crystallized from within-plate basaltic magmatism is challenging and crucial because the chemical composition of the igneous rocks has been modified during high-grade metamorphism,causing misidentification of the characters of the parental magma.Proterozoic metamorphosed mafic dykes occur throughout the Chhotanagpur Gneissic Complex(CGC)of eastern Indian shield.The E-W trending mafic dykes from the Saltora area in the southeastern CGC underwent metamorphism in two episodes:M1(650 MPa;770℃)and M2(300 MPa;744℃).The metamafics are enriched in LILE,depleted in HFSE,and display strong fractionation of LREE,nearly flat HREE patterns in a chondrite-normalized REE diagram,and show tholeiitic differentiation trend.Their geochemical affinity is towards rift-related,continental within-plate basalts.About 7%–10%melting of the carbonated spinel-peridotite sub-continental lithospheric mantle(SCLM)produced the parental mafic magma.The pre-existing SCLM was metasomatized by slab-derived fluid during the previous subduction.The upwelling of the asthenosphere in a post-collisional tectonic setting caused E-W trending fractures,lithospheric thinning,and gravitational collapse.These dykes were emplaced during crustal extension around 1070 Ma.The remarkable geochemical similarity between the mafic dykes of Saltora and Dhanbad,the ca.1096 Ma Mahoba(Bundelkhand craton),and the ca.1070 Ma Alcurra mafic dykes in Australia supports a genetic link.
基金Supported by the National Science and Technology Major Project(2024ZD1400101)Project of Sinopec(P23234)。
文摘Based on a large amount of basic research and experimental analysis data from Shengli Oilfield,Bohai Bay Basin,guided by the theory of whole petroleum system,the distribution of sedimentary systems,the distribution and hydrocarbon generation and expulsion process of source rocks,the variation of reservoir properties,and the control of fracture systems on hydrocarbon accumulation in the Paleogene of the Jiyang Depression,Boahai Bay Basin,were systematically analyzed,and the geological characteristics of the whole petroleum system in the rift basin were identified.Taking the Dongying Sag as an example,combined with the distribution of discovered conventional,tight,and shale oil/gas,a hydrocarbon accumulation model of the fault-controlled whole petroleum system in rift basin was proposed,and the distribution patterns of conventional and unconventional oil and gas reservoirs in large geological bodies horizontally and vertically were clarified.The research results show that paleoclimate and tectonic cycles control the orderly distribution of the Paleogene sedimentary system in the Jiyang Depression,the multi-stage source rocks provide sufficient material basis for in-situ shale oil/gas accumulation and other hydrocarbon migration and accumulation,the changes in reservoir properties control the dynamic threshold of hydrocarbon accumulation,and the combination of faults and fractures at different stages controls hydrocarbon migration and accumulation,and in-situ retention and accumulation of shale oil/gas,making the whole petroleum system in the rift basin associated,segmented and abrupt.The above elements are configured to form a composite whole petroleum system controlled by faults in the Paleogene of the Jiyang Depression.Moreover,under the control of hydrocarbon accumulation dynamics,a whole petroleum system can be divided into conventional subsystem and unconventional subsystem,with shale oil,tight oil and conventional oil in an orderly distribution in horizontal and vertical directions.This systematic understanding is referential for analyzing the whole petroleum system in continental rift basins in eastern China.
