Identifying deformational mechanisms and associated structures at various scales,ranging from regional-scale structures to microscopic fabric,is crucial for the assessment of tectonic development.Thirty-three samples ...Identifying deformational mechanisms and associated structures at various scales,ranging from regional-scale structures to microscopic fabric,is crucial for the assessment of tectonic development.Thirty-three samples were taken from the Qazzaz metamorphic core complex to estimate the finite strain for felsic and mafic minerals.These samples included gneisses rocks,monzogranite,and metavolcano-sedimentary rocks for both the Thalbah and Bayda groups.Using the Rf/j and Fry methods,the axial ratios(XZ)range about 2.20 to 7.10 and 1.90 to 9.10,respectively.For various rock units,the strain measurements show moderate to highly deformation.Most of the observed samples show shallow WNW dipping along a N to WNW trend of finite strain(X).The short axes(Z)based to be subvertical foliation related with a subhorizontal foliation.The results demonstrate that contacts generated at semi-brittle to ductile deformation and that the strain of magnitude has the same value for different lithologic units.It concluded that nappe generation in orogens results from pure shear deformation.展开更多
The Late Jurassic Monviso ophiolite in the Western Alps is a multiply deformed,eclogite-facies metaophiolite that represents a remnant of the Alpine Tethyan oceanic lithosphere.The recent recognition of a pre-Alpine d...The Late Jurassic Monviso ophiolite in the Western Alps is a multiply deformed,eclogite-facies metaophiolite that represents a remnant of the Alpine Tethyan oceanic lithosphere.The recent recognition of a pre-Alpine detachment fault in the Lower Tectonic Unit of this ophiolite has led to the discovery of an oceanic core complex,which developed during the initial stages of the tectonic evolution of the Alpine Tethys.The NNWstriking,20–25-km-long shear zone(Baracun Shear Zone)contains ductilely to cataclastically deformed blocks and clasts of Fe-Ti and Mg-Al metagabbros in a matrix made of mylonitic serpentinite and talc-chlorite schist with high Ni–Cr concentrations and high Cl contents.Intensely sheared ophicarbonate rocks and brecciated serpentinite within this shear zone are deformed by the Alpine-phase S1 foliation and D2 folds,providing a critical age constraint for the timing of its formation.Metabasaltic–metasedimentary rocks in the hanging wall increase in thickness away from the shear zone,characteristic of syn-extensional rock sequences in supradetachment basins.展开更多
The Heilongjiang Complex in northeast China(NE China)separates the Jiamusi and Songliao blocks and marks the suture zone of the former Mudanjiang Ocean,as evidenced by a variety of oceanic basalt-derived blueschists.U...The Heilongjiang Complex in northeast China(NE China)separates the Jiamusi and Songliao blocks and marks the suture zone of the former Mudanjiang Ocean,as evidenced by a variety of oceanic basalt-derived blueschists.Understanding the closure history of the Mudanjiang Ocean is crucial to unravelling the tectonic transition from the final amalgamation of the Central Asian Orogenic Belt(CAOB)to the onset of the Paleo-Pacific subduction.In this study,we investigate epidote-ferroglaucophane(Ep-Fgl)and garnet-ferrobarroisite(Grt-Fbrs)schists from the Yilan area of the Heilongjiang Complex through petrological,mineralogical,thermodynamic modelling,whole-rock geochemical,and geochronological analyses.The Ep-Fgl schists preserve a peak assemblage of ferroglaucophane+epidote+chlorite+clinopyroxene+phengite+titanite with peak P-T conditions of 13.5-15.8 kbar and 458-495℃.On the other hand,the Grt-Fbrs schists exhibit a peak assemblage of garnet+glaucophane/ferroglaucophane+lawsonite+chlorite+phengite+rutile±clinopyroxene±titanite,deriving peak P-T conditions of 16.4-18.3 kbar and 457-475℃.Both types of schist record similar clockwise P-T paths,with three metamorphic stages:a peak epidote-to-lawsonite blueschist-facies stage,a post-peak decompression stage in the epidote amphibolite-facies,and a late greenschist-facies overprint stage.The Ep-Fgl schists display alkaline OIB-like geochemical affinities,while the Grt-Fbrs schists show tholeiitic MORB-like characteristics,suggesting that the protoliths represent fragments of the Mudanjiang oceanic crust.Magmatic zircon grains from Ep-Fgl schists yield protolith ages of 276±1 Ma and 280±1 Ma,whereas zircon of Grt-Fbrs schists document protolith ages of 249±2 Ma and 248±2 Ma,indicating that the Mudanjiang Ocean existed since at least the early Permian.Reconstruction of the metamorphic P-T evolution,combined with previous magmatic and metamorphic age data from rocks of the Heilongjiang Complex and of adjacent tectonic units suggests that the subduction and eventual closure of the Mudanjiang Ocean occurred between the late Triassic and middle Jurassic,driven by a regional stress regime shift caused by the westward subduction of the Paleo-Pacific Plate beneath Eurasia.展开更多
Subduction initiation is a critical part of the plate tectonic system,but its geodynamic process is still poorly understood due to the lack of well-preserved geological records.Based on new zircon U–Pb–Hf isotopic a...Subduction initiation is a critical part of the plate tectonic system,but its geodynamic process is still poorly understood due to the lack of well-preserved geological records.Based on new zircon U–Pb–Hf isotopic and whole-rock geochemical data,we report the first discovery of a latest Cambrian–Early Ordovician forearc-arc rock sequence in the Eastern Alps.This sequence includes granitic gneisses,amphibolites,and amphibole plagiogneisses from the ophiolitic Speik Complex and Gleinalpe Complex.These rocks exhibit geochemical affinities with typical oceanic plagiogranites,forearc basalts(FABs),and island arc basalts,respectively.The latest Cambrian plagiogranitic protoliths(491±2 Ma)are shearing-type plagiogranites that were formed in the tectonic setting of forearc spreading.The latest Cambrian FABs(496–489 Ma)have similar geochemical compositions and positiveεHf(t)values(+2.5 to+14.9)to the depleted mid-ocean ridge basalts.However,they show depletion in high field strength elements(HFSEs;e.g.,Nb,Ta,and Zr)and have relatively low Ti/V ratios.These features suggest that they were derived from a depleted mantle source modified by subducting slab-released components in a forearc environment.The Early Ordovician basaltic protoliths(476–472 Ma)of amphibole plagiogneisses show enrichment in large ion lithophile elements and depletion in HFSEs(e.g.Nb,Ta,Zr,and Hf),implying a mature island arc environment.These metaigneous rocks,along with the coeval boninite-like high-Mg amphibolites near the study area,form a typical rock sequence resembling that of the Izu–Bonin–Mariana(IBM)arc system.The Speik and Gleinalpe complexes document a complete magmatic evolution from subduction initiation to mature arc development within the West Proto-Tethys Ocean.Integrating our new data with published work,we reconstruct the late Ediacaran–early Paleozoic tectonic evolution of the northern Gondwana.During the late Ediacaran–early Cambrian,the rollback of the West Proto-Tethys oceanic plate triggered the separation of the Wechsel-Silvretta-Gleinalpe continental arc from the northern Gondwana.This process led to the formation of the Speik back-arc oceanic basin,a southwestern branch of the West Proto-Tethys Ocean.In the latest Cambrian–Early Ordovician,subduction initiation occurred in the Speik Ocean,which subsequently developed into an intra-oceanic arc system.During the Early Devonian,the Speik Ocean closed and the Wechsel-Silvretta-Gleinalpe continental arc reattached to the Gondwana,as evidenced by the metamorphic event at ca.400 Ma.展开更多
The Central Asian Orogenic Belt(CAOB)is one of the largest and best preserved accretionary type orogenic belts in the world.Due to its complex tectonic history,the timing and location of the final closure of the Paleo...The Central Asian Orogenic Belt(CAOB)is one of the largest and best preserved accretionary type orogenic belts in the world.Due to its complex tectonic history,the timing and location of the final closure of the Paleo-Asian Ocean and its tectonic evolution have been hotly discussed.To determine the petrogenesis and tectonic characteristics of the poorly exposed Triassic volcanic-intrusive complex on the northern margin of the eastern North China Craton,the authors conducted a study of zircon Lu-Hf isotopes,integrated with zircon U-Pb dating and whole-rock geochemistry.Zircons from eight representative volcanic and intrusive samples yielded concordant U-Pb ages of 251-245 Ma.The volcanic and intrusive rocks are all characterized by enrichments in large ion lithophile elements and depletions in high field strength elements,and they have features similar to those of highly fractionated Ⅰ-type granites.TheεHf(t)values for the volcanic and intrusive rocks,respectively,range from-1.69 to+3.75(mean=+1.22)and-2.17 to+3.15(mean=+0.38),with two-stage model ages of 1035-1345 Ma(mean=1196 Ma)and 1073-1401 Ma(mean=1250 Ma).The Hf isotopic features indicate that these rocks were formed by partial melting of young crustal material that was newly accreted from the depleted mantle,together with a degree of contamination by other crustal material.The volcanic-intrusive complex was related to an active continental margin in a volcanic arc and syn-collisional setting,indicating that the Paleo-Asian Ocean was closed after the Middle Triassic(245 Ma)along the northern margin of the North China Craton.This provides a constraint on the timing of the change in tectonic setting in this area from compression to extension.The results enhance our understanding of the evolution of the Paleo-Asian Ocean.展开更多
PSⅡ core antenna complexes, CP43 and CP47, were purified from spinach (Spinacia oleracea L.) by DEAE Fractogel TSK 650S anion exchange chromatography. Their normal temperature (298 K) resonance Raman spectra were...PSⅡ core antenna complexes, CP43 and CP47, were purified from spinach (Spinacia oleracea L.) by DEAE Fractogel TSK 650S anion exchange chromatography. Their normal temperature (298 K) resonance Raman spectra were measured. The results suggest that all β carotenoids bound to CP43 and CP47 are in all trans configuration and likely in twisted conformations.展开更多
Cytochrome b_559 in photosystem Ⅱ reaction center was purified from spinach ( Spinacia oleracea L.) and rice ( Oryza sativa L.) by a rapid and simple procedure. Their low temperature fluorescence emission and e...Cytochrome b_559 in photosystem Ⅱ reaction center was purified from spinach ( Spinacia oleracea L.) and rice ( Oryza sativa L.) by a rapid and simple procedure. Their low temperature fluorescence emission and excitation spectra, ultraviolet fluorescence spectra and absolute absorption spectra were presented. The author's purification methods, which enhanced the yield of pure protein and shorted the time for isolation, have several advantages: 1. use of oxygen_evolving PSⅡ core complexes as the starting material in order to avoid disturbing from other cytochromes; 2. isocratic elution of cytochrome b_559 from a DEAE_Sephacel column for eliminating the impurity and yielding the protein in pure state; 3. a simple column procedure for removal of excess Triton X_100. Purified cytochromes b_559 from these species have similar optical spectra and mobility during gel electrophoresis under native conditions. From the results of novel electrophoresis (Tricine_SDS_PAGE), cytochrome b_559 from both spinach and rice reveal two polypeptide bands (apparent molecular weight 9 kD and 4 kD, respectively). By measuring of 77 K fluorescence spectra, it was shown that for the purified cytochrome b_559 there were two excitation peaks at 439 nm and 413 nm, and two emission peaks at 563 nm and 668 nm. This is the first indication that Cyt b_559 is able to emit fluorescence and also transfer excited electrons to chlorophyll. By the use of ultraviolet fluorescence spectra, it was demonstrated for the first time that the location of Trp residue could be in the hydrophobic transmembrane region of cytochrome b_559.展开更多
Abstract There are two extensional systems in the Xiaoqinling metamorphic core complex (XMCC). One is the detachment fault system developed along the peripheries of the XMCC, which extended in an ESE-WNW direction and...Abstract There are two extensional systems in the Xiaoqinling metamorphic core complex (XMCC). One is the detachment fault system developed along the peripheries of the XMCC, which extended in an ESE-WNW direction and whose upper plate moved towards the WNW. The other extensional system includes the retrograde shear zones and normal faults developed within the XMCC, which represent the collapse of the XMCC. Ar-Ar and K-Ar dating shows that the extension of the detachment fault system continued from 135 to 123 Ma, i.e. in the late stage of its evolution at about 127 Ma. The collapse represented by the extensional system within the XMCC was operative during 120–106 Ma, and its main activity occurred about 116 Ma ago. These suggest that the XMCC experienced two extensional stages in its evolution, i.e., the syn-orogenic regional extension and post-orogenic collapse extension.展开更多
The Louzidian metamorphic core complex (LMCC) in southern Chifeng is located on the northern margin of the North China craton. Structural analyses of the LMCC and its extensional detachment system indicate that the LM...The Louzidian metamorphic core complex (LMCC) in southern Chifeng is located on the northern margin of the North China craton. Structural analyses of the LMCC and its extensional detachment system indicate that the LMCC experienced two-stage extension. The ductile regime experienced top-to-northeast shearing extension and the brittle detachment fault underwent top-down-outwards slipping. Between these two stages, a semi-ductile regime recorded the transition from ductile to brittle. The hanging wall of the detachment fault is similar to those classic supradetachment basins in western North America. Analyses of provenance and paleocurrent directions in the basins show that there were two filling stages. In the early stage, materials came from the southwest margin of the basin and the hanging wall of the detachment system and were transported from southwest to northeast; while in the late stage, deposits were derived from the footwall of the detachment fault and transported outwards to the two sides of the core complex. Since the filling period of the basins is from the late Jurassic to the late Cretaceous and it is coeval with the extension, the two filling stages reflect the two-stage history of the detachment fault. The large-scale late Jurassic underplating in the deep crust of the Chifeng area led to thickening and heating of the middle-upper crust and trigged the extension at depths and volcanism on the surface. In the early Cretaceous the upper plate of the detachment fault moved northeastwards and sediments were transported from southwest to northeast, while in the late Cretaceous the core complex was uplifted rapidly, the original basin was separated by the uplifted core, and lower-plate-derived debris was deposited in the adjacent upper-plate basins of the detachment fault. Evidentially, the development of the supradetachment basins were controlled by the extension and in turn the fillings in the basins recorded information of the extension, which has provided new evidence for kinematic interpretation of the Louzidian core complex.展开更多
: The kinematic vorticity number and strain of the mylonitic zone related to the detachment fault increase from ESE to WNW along the moving direction of the upper plate of the Xiaoqinling metamorphic core complex (XMC...: The kinematic vorticity number and strain of the mylonitic zone related to the detachment fault increase from ESE to WNW along the moving direction of the upper plate of the Xiaoqinling metamorphic core complex (XMCC) and the geometry of quartz c-axis fabrics changes progressively from crossed girdles to single girdles in the same direction. Therefore, pure shear is dominant in the ESE part of the XMCC while simple shear becomes increasingly important towards WNW. However, the shear type does not change with the strain across the shear zone, thus the variation of shear type is of significance in indicating the formation mechanism. The granitic plutons within the XMCC came from the deep source and their emplacement was an active and forceful upwelling prior to the detachment faulting. The PTt path demonstrates that magmatism is an important cause for the formation of the XMCC. The formation mechanism of the XMCC is supposed to be active plutonism and passive detachment. Crustal thickening and magmatic doming caused necking extension with pure shear, and magmatic heating and doming resulted in detachment extension with simple shear and formed the XMCC.展开更多
The Liaonan metamorphic core complex （mcc） has a three-layer structure and is constituted by five parts, i.e. a detachment fault zone, an allochthonous upper plate and an supradetachment basin above the fault zone, ...The Liaonan metamorphic core complex （mcc） has a three-layer structure and is constituted by five parts, i.e. a detachment fault zone, an allochthonous upper plate and an supradetachment basin above the fault zone, and highly metamorphosed rocks and intrusive rocks in the lower plate. The allochthonous upper plate is mainly of Neoproterozoic and Paleozoic rocks weakly deformed and metamorphosed in pre-Indosinan stage. Above these rocks is a small-scale supradetachment basin of Cretaceous sedimentary and volcanic rocks. The lower plate is dominated by Archean TTG gneisses with minor amount of supracrustal rocks. The Archean rocks are intruded by late Mesozoic synkinematic monzogranitic and granitic plutons. Different types of fault rocks, providing clues to the evolution of the detachment fault zone, are well-preserved in the fault zone, e.g. mylonitic gneiss, mylonites, brecciated mylonites, microbreccias and pseudotachylites. Lineations in lower plate granitic intrusions have consistent orientation that indicate uniform top-to-NW shearing along the main detachment fault zone. This also provides evidence for the synkinematic characteristics of the granitic plutons in the lower plate. Structural analysis of the different parts in the mcc and isotopic dating of plutonic rocks from the lower plate and mylonitic rocks from detachment fault zone suggest that exhumation of the mcc started with regional crustal extension due to crustal block rotation and tangential shearing. The extension triggered magma formation, upwelling and emplacement. This event ended with appearance of pseudotachylite and fault gauges formed at the uppermost crustal level. U-Pb dating of single zircon grains from granitic rocks in the lower plate gives an age of 130±2.5 Ma, and biotite grains from the main detachment fault zone have ^40Ar-^39Ar ages of 108-119 Ma. Several aspects may provide constraints for the exhumation of the Liaonan mcc. These include regional extensional setting, cover/basement contact, temporal and spatial coupling of extension and magmatism, basin development and evolution of fault tectonites along detachment fault zone. We propose that the exhumation of the Liaonan mcc resulted from regional extension and thinning of crust or lithosphere in eastern North China, and accompanied with synkinematic intrusion of granitic plutons, formation of detachment fault zone, uplifting and exhumation of lower-plate rocks, and appearance of supradetachment basin.展开更多
Metamorphic core complexes are a basic structural pattern related to extensional tectonics. Several characteristics of different scales of metamorphic core complexes in the Fangshan and Yunmengshan (Beijing) , Zhongti...Metamorphic core complexes are a basic structural pattern related to extensional tectonics. Several characteristics of different scales of metamorphic core complexes in the Fangshan and Yunmengshan (Beijing) , Zhongtiaoshan (Shanxi) , and Dengfong (Henan) are examined. A three-layer model for metam orphic core complexes is suggested . The conclusion is that metam orphic core complexes are the result of multiphase intracontinental crustal extensions and are an important tectonic pattern. which exposes the basement metam orphic rocks to the ground surface in the intracontinental cover .展开更多
Widespread magmatism, metamorphic core complexes(MCCs), and significant lithospheric thinning occurred during the Mesozoic in the North China Craton(NCC). It has been suggested that the coeval exhumation of MCCs with ...Widespread magmatism, metamorphic core complexes(MCCs), and significant lithospheric thinning occurred during the Mesozoic in the North China Craton(NCC). It has been suggested that the coeval exhumation of MCCs with uniform northwest-southeast shear senses and magmatism probably resulted from a decratonization event during the retreat of the paleo-Pacific Plate. Here we used two-dimensional finite element thermomechanical numerical models to investigate critical parameters controlling the formation of MCCs under far-field extensional stress. We observed three end-member deformation modes: the MCC mode, the symmetric-dome mode, and the pure-shear mode. The MCC mode requires a Moho temperature of ≥700 ℃ and an extensional strain rate of ≥5 × 10^(-16)s^(-1), implying that the lithosphere had already thinned when the MCC was formed in the Mesozoic. Considering that the widespread MCCs have the same northwest-southeast extension direction in the NCC, we suggest that the MCCs are surface expressions of both large-scale extension and craton destruction and that rollback of the paleo-Pacific slab might be the common driving force.展开更多
This study utilizes ANSYS to establish FEM's model of metamorphic core complex,and used thermal-structure analysis to simulate metamorphic core complex's temperature field and stress field.The metamorphic core...This study utilizes ANSYS to establish FEM's model of metamorphic core complex,and used thermal-structure analysis to simulate metamorphic core complex's temperature field and stress field.The metamorphic core complex formation mechanism is discussed.The simulation results show that the temperature field change appearing as the earth surface's temperature is the lowest,and the temperature of metamorphic core complex's nucleus is the highest.The temperature field is higher along with depth increase,and the stress field change appearing as the biggest stress occurs in the nucleus.The next stress field occurs at the top of the cover.展开更多
As anticipated from studies of ophiolite complexes,direct investigations of the oceanic crust confirm that basaltic dikes are an integral part of the upper 2 km of the oceanic crust.Currently available information sug...As anticipated from studies of ophiolite complexes,direct investigations of the oceanic crust confirm that basaltic dikes are an integral part of the upper 2 km of the oceanic crust.Currently available information suggests展开更多
There is a belt of metamorphic core complexes in the western margin of the Yangtze craton . The geological setting of the belt is similar to that of the Cordilleran metamorphic core complexes . A typical one in this b...There is a belt of metamorphic core complexes in the western margin of the Yangtze craton . The geological setting of the belt is similar to that of the Cordilleran metamorphic core complexes . A typical one in this belt is the Jianglang metamorphic core complex , which has a configuration consisting of three layers : a core complex consisting of Mesoproterozoic schist sequence . a ductile middle slab consisting of Paleozoic meta- sedimentary -basalt characterized by the development of ' folding layer' and an upper cover consisting of Xikang Group which has suffered both buckling and flattening . A detachment fault developed along the contact boundary between the cover and basement causes the omission of Upper Sinian and Cambrian at the base of cover . A lot of normal ductile shear zones developed in the cover causes the thinning of it . All the features show that the early extension results in the thinning of crust , but the formation of the dome and exposure of basement rocks may be the results of superimposing of the E-W directed contraction and the following southward thrusting during Indosinian to Yanshanian orogeny . Syntectonic plutonism and pervasive thermo - metamor-phism in the cover suggest that the thermal uplift also causes the uplift of the MCC .展开更多
Even though light is the unique source of enengy forphotosynthesis,it can also be hannful to plant,Photoin-hibition occurs when light energy absorption largely ex-ceeds the energy consumption of photosynthetic reactio...Even though light is the unique source of enengy forphotosynthesis,it can also be hannful to plant,Photoin-hibition occurs when light energy absorption largely ex-ceeds the energy consumption of photosynthetic reactions.Today,the mechanisnu of photoinhibition has become amajor topic of photosynthesis research.It is generally ae-cepted that PS IⅡis affected predominantly by photounhi-bition[1],which causes a loss of electron transfer caparityand oxygen evolution activity,bleaching of pigment,degradation of D,and other proteins,croes-linking be-tween polypeptidesi.展开更多
The reaction of a ruthenium carbide complex RuCl2（C：）（PCy3）2 with [H（Et2O）x]＋[BF4]- at a molar ratio of 1：2 produced a two-core ruthenium carbene complex, {[RuCl（=CHPCy3）（PCy3）]2（μ-Cl）3}＋·[BF4]-,...The reaction of a ruthenium carbide complex RuCl2（C：）（PCy3）2 with [H（Et2O）x]＋[BF4]- at a molar ratio of 1：2 produced a two-core ruthenium carbene complex, {[RuCl（=CHPCy3）（PCy3）]2（μ-Cl）3}＋·[BF4]-, in the form of a yellow-green crystalline solid in a yield of 94%. This two-core ruthenium complex is a selective catalyst for ring closing metathesis of unsubstituted terminal dienes. More importantly, no isomerized byproduct was observed for N-substrates when the two-core ruthenium complex was used as the catalyst at an elevated temperature（137 °C）, indicating that the complex is a chemo-selective catalyst for ring closing metathesis reactions.展开更多
The Earth’s Free Core Nutation(FCN) causes Earth tides and forced nutation with frequencies close to the FCN that exhibit resonance effects.High-precision superconducting gravimeter(SG) and very long baseline interfe...The Earth’s Free Core Nutation(FCN) causes Earth tides and forced nutation with frequencies close to the FCN that exhibit resonance effects.High-precision superconducting gravimeter(SG) and very long baseline interferometry(VLBI) provide good observation techniques for detecting the FCN parameters.However,some choices in data processing and solution procedures increase the uncertainty of the FCN parameters.In this study,we analyzed the differences and the effectiveness of weight function and ocean tide corrections in the FCN parameter detection using synthetic data,SG data from thirty-one stations,and the 10 celestial pole offset(CPO) series.The results show that significant discrepancies are caused by different computing options for a single SG station.The stacking method,which results in a variation of0.24-5 sidereal days(SDs) in the FCN period(T) and 10^(3)-10^(4) in the quality factor(Q) due to the selection of the weighting function and the ocean tide model(OTM),can effectively suppress this influence.The statistical analysis results of synthetic data shows that although different weight choices,while adjusting the proportion of diurnal tidal waves involved,do not significantly improve the accuracy of fitted FCN parameters from gravity observations.The study evaluated a series of OTMs using the loading correction efficiency.The fitting of FCN parameters can be improved by selecting the mean of appropriate OTMs based on the evaluation results.Through the estimation of the FCN parameters based on the forced nutation,it was found that the weight function P_(1) is more suitable than others,and different CPO series(after 2009) resulted in a difference of 0.4 SDs in the T and of 103 in the Q.We estimated the FCN parameters for SG(T=430.4±1.5 SDs and Q=1.52×10^(4)±2.5×10^(3)) and for VLBI(T=429.8±0.7 SDs,Q=1.88×10^(4)±2.1×10^(3)).展开更多
基金supported and funded by the Researchers Supporting Project(Project No.RSPD2024R781),King Saud University,Riyadh,Saudi Arabia。
文摘Identifying deformational mechanisms and associated structures at various scales,ranging from regional-scale structures to microscopic fabric,is crucial for the assessment of tectonic development.Thirty-three samples were taken from the Qazzaz metamorphic core complex to estimate the finite strain for felsic and mafic minerals.These samples included gneisses rocks,monzogranite,and metavolcano-sedimentary rocks for both the Thalbah and Bayda groups.Using the Rf/j and Fry methods,the axial ratios(XZ)range about 2.20 to 7.10 and 1.90 to 9.10,respectively.For various rock units,the strain measurements show moderate to highly deformation.Most of the observed samples show shallow WNW dipping along a N to WNW trend of finite strain(X).The short axes(Z)based to be subvertical foliation related with a subhorizontal foliation.The results demonstrate that contacts generated at semi-brittle to ductile deformation and that the strain of magnitude has the same value for different lithologic units.It concluded that nappe generation in orogens results from pure shear deformation.
基金“ex 60%–2013 and 2014”Universitàdegli Studi di Torino and PROGEO Piemonte(Universita degli Studi di Torino and Compagnia San Paolo)to A.Festa and G.Balestrothe Italian Ministry of University and Research Cofin-PRIN 2010/2011(“GEOPROB–GEOdynamic Processes of Oceanic Basins”)to A.Festa and P.Tartarotti“Subduction and exhumationof continental lithosphere:Implications on orogenic architecture,environment and climate”to G.Balestro.
文摘The Late Jurassic Monviso ophiolite in the Western Alps is a multiply deformed,eclogite-facies metaophiolite that represents a remnant of the Alpine Tethyan oceanic lithosphere.The recent recognition of a pre-Alpine detachment fault in the Lower Tectonic Unit of this ophiolite has led to the discovery of an oceanic core complex,which developed during the initial stages of the tectonic evolution of the Alpine Tethys.The NNWstriking,20–25-km-long shear zone(Baracun Shear Zone)contains ductilely to cataclastically deformed blocks and clasts of Fe-Ti and Mg-Al metagabbros in a matrix made of mylonitic serpentinite and talc-chlorite schist with high Ni–Cr concentrations and high Cl contents.Intensely sheared ophicarbonate rocks and brecciated serpentinite within this shear zone are deformed by the Alpine-phase S1 foliation and D2 folds,providing a critical age constraint for the timing of its formation.Metabasaltic–metasedimentary rocks in the hanging wall increase in thickness away from the shear zone,characteristic of syn-extensional rock sequences in supradetachment basins.
基金the support of Yajing Mao and Lingquan Zhao during the preparation of the manuscript.This research was financially supported by the National Natural Science Foundation of China(No.U2244206).
文摘The Heilongjiang Complex in northeast China(NE China)separates the Jiamusi and Songliao blocks and marks the suture zone of the former Mudanjiang Ocean,as evidenced by a variety of oceanic basalt-derived blueschists.Understanding the closure history of the Mudanjiang Ocean is crucial to unravelling the tectonic transition from the final amalgamation of the Central Asian Orogenic Belt(CAOB)to the onset of the Paleo-Pacific subduction.In this study,we investigate epidote-ferroglaucophane(Ep-Fgl)and garnet-ferrobarroisite(Grt-Fbrs)schists from the Yilan area of the Heilongjiang Complex through petrological,mineralogical,thermodynamic modelling,whole-rock geochemical,and geochronological analyses.The Ep-Fgl schists preserve a peak assemblage of ferroglaucophane+epidote+chlorite+clinopyroxene+phengite+titanite with peak P-T conditions of 13.5-15.8 kbar and 458-495℃.On the other hand,the Grt-Fbrs schists exhibit a peak assemblage of garnet+glaucophane/ferroglaucophane+lawsonite+chlorite+phengite+rutile±clinopyroxene±titanite,deriving peak P-T conditions of 16.4-18.3 kbar and 457-475℃.Both types of schist record similar clockwise P-T paths,with three metamorphic stages:a peak epidote-to-lawsonite blueschist-facies stage,a post-peak decompression stage in the epidote amphibolite-facies,and a late greenschist-facies overprint stage.The Ep-Fgl schists display alkaline OIB-like geochemical affinities,while the Grt-Fbrs schists show tholeiitic MORB-like characteristics,suggesting that the protoliths represent fragments of the Mudanjiang oceanic crust.Magmatic zircon grains from Ep-Fgl schists yield protolith ages of 276±1 Ma and 280±1 Ma,whereas zircon of Grt-Fbrs schists document protolith ages of 249±2 Ma and 248±2 Ma,indicating that the Mudanjiang Ocean existed since at least the early Permian.Reconstruction of the metamorphic P-T evolution,combined with previous magmatic and metamorphic age data from rocks of the Heilongjiang Complex and of adjacent tectonic units suggests that the subduction and eventual closure of the Mudanjiang Ocean occurred between the late Triassic and middle Jurassic,driven by a regional stress regime shift caused by the westward subduction of the Paleo-Pacific Plate beneath Eurasia.
基金supported by the National Natural Science Foundation of China(Grant Nos.42272244 and 91755212)Taishan Scholars(Grant No.ts20190918).
文摘Subduction initiation is a critical part of the plate tectonic system,but its geodynamic process is still poorly understood due to the lack of well-preserved geological records.Based on new zircon U–Pb–Hf isotopic and whole-rock geochemical data,we report the first discovery of a latest Cambrian–Early Ordovician forearc-arc rock sequence in the Eastern Alps.This sequence includes granitic gneisses,amphibolites,and amphibole plagiogneisses from the ophiolitic Speik Complex and Gleinalpe Complex.These rocks exhibit geochemical affinities with typical oceanic plagiogranites,forearc basalts(FABs),and island arc basalts,respectively.The latest Cambrian plagiogranitic protoliths(491±2 Ma)are shearing-type plagiogranites that were formed in the tectonic setting of forearc spreading.The latest Cambrian FABs(496–489 Ma)have similar geochemical compositions and positiveεHf(t)values(+2.5 to+14.9)to the depleted mid-ocean ridge basalts.However,they show depletion in high field strength elements(HFSEs;e.g.,Nb,Ta,and Zr)and have relatively low Ti/V ratios.These features suggest that they were derived from a depleted mantle source modified by subducting slab-released components in a forearc environment.The Early Ordovician basaltic protoliths(476–472 Ma)of amphibole plagiogneisses show enrichment in large ion lithophile elements and depletion in HFSEs(e.g.Nb,Ta,Zr,and Hf),implying a mature island arc environment.These metaigneous rocks,along with the coeval boninite-like high-Mg amphibolites near the study area,form a typical rock sequence resembling that of the Izu–Bonin–Mariana(IBM)arc system.The Speik and Gleinalpe complexes document a complete magmatic evolution from subduction initiation to mature arc development within the West Proto-Tethys Ocean.Integrating our new data with published work,we reconstruct the late Ediacaran–early Paleozoic tectonic evolution of the northern Gondwana.During the late Ediacaran–early Cambrian,the rollback of the West Proto-Tethys oceanic plate triggered the separation of the Wechsel-Silvretta-Gleinalpe continental arc from the northern Gondwana.This process led to the formation of the Speik back-arc oceanic basin,a southwestern branch of the West Proto-Tethys Ocean.In the latest Cambrian–Early Ordovician,subduction initiation occurred in the Speik Ocean,which subsequently developed into an intra-oceanic arc system.During the Early Devonian,the Speik Ocean closed and the Wechsel-Silvretta-Gleinalpe continental arc reattached to the Gondwana,as evidenced by the metamorphic event at ca.400 Ma.
基金supported by the National Natural Science Foundation of China(U2244213)the project from China Geological Survey(No.DD20160062)the fundamental research project from the Institute of Geomechanics,Chinese Academy of Geological Sciences(DZLXJK202307).
文摘The Central Asian Orogenic Belt(CAOB)is one of the largest and best preserved accretionary type orogenic belts in the world.Due to its complex tectonic history,the timing and location of the final closure of the Paleo-Asian Ocean and its tectonic evolution have been hotly discussed.To determine the petrogenesis and tectonic characteristics of the poorly exposed Triassic volcanic-intrusive complex on the northern margin of the eastern North China Craton,the authors conducted a study of zircon Lu-Hf isotopes,integrated with zircon U-Pb dating and whole-rock geochemistry.Zircons from eight representative volcanic and intrusive samples yielded concordant U-Pb ages of 251-245 Ma.The volcanic and intrusive rocks are all characterized by enrichments in large ion lithophile elements and depletions in high field strength elements,and they have features similar to those of highly fractionated Ⅰ-type granites.TheεHf(t)values for the volcanic and intrusive rocks,respectively,range from-1.69 to+3.75(mean=+1.22)and-2.17 to+3.15(mean=+0.38),with two-stage model ages of 1035-1345 Ma(mean=1196 Ma)and 1073-1401 Ma(mean=1250 Ma).The Hf isotopic features indicate that these rocks were formed by partial melting of young crustal material that was newly accreted from the depleted mantle,together with a degree of contamination by other crustal material.The volcanic-intrusive complex was related to an active continental margin in a volcanic arc and syn-collisional setting,indicating that the Paleo-Asian Ocean was closed after the Middle Triassic(245 Ma)along the northern margin of the North China Craton.This provides a constraint on the timing of the change in tectonic setting in this area from compression to extension.The results enhance our understanding of the evolution of the Paleo-Asian Ocean.
文摘PSⅡ core antenna complexes, CP43 and CP47, were purified from spinach (Spinacia oleracea L.) by DEAE Fractogel TSK 650S anion exchange chromatography. Their normal temperature (298 K) resonance Raman spectra were measured. The results suggest that all β carotenoids bound to CP43 and CP47 are in all trans configuration and likely in twisted conformations.
文摘Cytochrome b_559 in photosystem Ⅱ reaction center was purified from spinach ( Spinacia oleracea L.) and rice ( Oryza sativa L.) by a rapid and simple procedure. Their low temperature fluorescence emission and excitation spectra, ultraviolet fluorescence spectra and absolute absorption spectra were presented. The author's purification methods, which enhanced the yield of pure protein and shorted the time for isolation, have several advantages: 1. use of oxygen_evolving PSⅡ core complexes as the starting material in order to avoid disturbing from other cytochromes; 2. isocratic elution of cytochrome b_559 from a DEAE_Sephacel column for eliminating the impurity and yielding the protein in pure state; 3. a simple column procedure for removal of excess Triton X_100. Purified cytochromes b_559 from these species have similar optical spectra and mobility during gel electrophoresis under native conditions. From the results of novel electrophoresis (Tricine_SDS_PAGE), cytochrome b_559 from both spinach and rice reveal two polypeptide bands (apparent molecular weight 9 kD and 4 kD, respectively). By measuring of 77 K fluorescence spectra, it was shown that for the purified cytochrome b_559 there were two excitation peaks at 439 nm and 413 nm, and two emission peaks at 563 nm and 668 nm. This is the first indication that Cyt b_559 is able to emit fluorescence and also transfer excited electrons to chlorophyll. By the use of ultraviolet fluorescence spectra, it was demonstrated for the first time that the location of Trp residue could be in the hydrophobic transmembrane region of cytochrome b_559.
文摘Abstract There are two extensional systems in the Xiaoqinling metamorphic core complex (XMCC). One is the detachment fault system developed along the peripheries of the XMCC, which extended in an ESE-WNW direction and whose upper plate moved towards the WNW. The other extensional system includes the retrograde shear zones and normal faults developed within the XMCC, which represent the collapse of the XMCC. Ar-Ar and K-Ar dating shows that the extension of the detachment fault system continued from 135 to 123 Ma, i.e. in the late stage of its evolution at about 127 Ma. The collapse represented by the extensional system within the XMCC was operative during 120–106 Ma, and its main activity occurred about 116 Ma ago. These suggest that the XMCC experienced two extensional stages in its evolution, i.e., the syn-orogenic regional extension and post-orogenic collapse extension.
基金supported by the National Natural Science Foundation of China(grant 40102017)the Doctoral Program of Higher Education(grant 2000000128).
文摘The Louzidian metamorphic core complex (LMCC) in southern Chifeng is located on the northern margin of the North China craton. Structural analyses of the LMCC and its extensional detachment system indicate that the LMCC experienced two-stage extension. The ductile regime experienced top-to-northeast shearing extension and the brittle detachment fault underwent top-down-outwards slipping. Between these two stages, a semi-ductile regime recorded the transition from ductile to brittle. The hanging wall of the detachment fault is similar to those classic supradetachment basins in western North America. Analyses of provenance and paleocurrent directions in the basins show that there were two filling stages. In the early stage, materials came from the southwest margin of the basin and the hanging wall of the detachment system and were transported from southwest to northeast; while in the late stage, deposits were derived from the footwall of the detachment fault and transported outwards to the two sides of the core complex. Since the filling period of the basins is from the late Jurassic to the late Cretaceous and it is coeval with the extension, the two filling stages reflect the two-stage history of the detachment fault. The large-scale late Jurassic underplating in the deep crust of the Chifeng area led to thickening and heating of the middle-upper crust and trigged the extension at depths and volcanism on the surface. In the early Cretaceous the upper plate of the detachment fault moved northeastwards and sediments were transported from southwest to northeast, while in the late Cretaceous the core complex was uplifted rapidly, the original basin was separated by the uplifted core, and lower-plate-derived debris was deposited in the adjacent upper-plate basins of the detachment fault. Evidentially, the development of the supradetachment basins were controlled by the extension and in turn the fillings in the basins recorded information of the extension, which has provided new evidence for kinematic interpretation of the Louzidian core complex.
文摘: The kinematic vorticity number and strain of the mylonitic zone related to the detachment fault increase from ESE to WNW along the moving direction of the upper plate of the Xiaoqinling metamorphic core complex (XMCC) and the geometry of quartz c-axis fabrics changes progressively from crossed girdles to single girdles in the same direction. Therefore, pure shear is dominant in the ESE part of the XMCC while simple shear becomes increasingly important towards WNW. However, the shear type does not change with the strain across the shear zone, thus the variation of shear type is of significance in indicating the formation mechanism. The granitic plutons within the XMCC came from the deep source and their emplacement was an active and forceful upwelling prior to the detachment faulting. The PTt path demonstrates that magmatism is an important cause for the formation of the XMCC. The formation mechanism of the XMCC is supposed to be active plutonism and passive detachment. Crustal thickening and magmatic doming caused necking extension with pure shear, and magmatic heating and doming resulted in detachment extension with simple shear and formed the XMCC.
基金supported by the National Natural Science Foundation of China(Grant Nos.40472105,40510104086 and 40272084)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20040491003).
文摘The Liaonan metamorphic core complex （mcc） has a three-layer structure and is constituted by five parts, i.e. a detachment fault zone, an allochthonous upper plate and an supradetachment basin above the fault zone, and highly metamorphosed rocks and intrusive rocks in the lower plate. The allochthonous upper plate is mainly of Neoproterozoic and Paleozoic rocks weakly deformed and metamorphosed in pre-Indosinan stage. Above these rocks is a small-scale supradetachment basin of Cretaceous sedimentary and volcanic rocks. The lower plate is dominated by Archean TTG gneisses with minor amount of supracrustal rocks. The Archean rocks are intruded by late Mesozoic synkinematic monzogranitic and granitic plutons. Different types of fault rocks, providing clues to the evolution of the detachment fault zone, are well-preserved in the fault zone, e.g. mylonitic gneiss, mylonites, brecciated mylonites, microbreccias and pseudotachylites. Lineations in lower plate granitic intrusions have consistent orientation that indicate uniform top-to-NW shearing along the main detachment fault zone. This also provides evidence for the synkinematic characteristics of the granitic plutons in the lower plate. Structural analysis of the different parts in the mcc and isotopic dating of plutonic rocks from the lower plate and mylonitic rocks from detachment fault zone suggest that exhumation of the mcc started with regional crustal extension due to crustal block rotation and tangential shearing. The extension triggered magma formation, upwelling and emplacement. This event ended with appearance of pseudotachylite and fault gauges formed at the uppermost crustal level. U-Pb dating of single zircon grains from granitic rocks in the lower plate gives an age of 130±2.5 Ma, and biotite grains from the main detachment fault zone have ^40Ar-^39Ar ages of 108-119 Ma. Several aspects may provide constraints for the exhumation of the Liaonan mcc. These include regional extensional setting, cover/basement contact, temporal and spatial coupling of extension and magmatism, basin development and evolution of fault tectonites along detachment fault zone. We propose that the exhumation of the Liaonan mcc resulted from regional extension and thinning of crust or lithosphere in eastern North China, and accompanied with synkinematic intrusion of granitic plutons, formation of detachment fault zone, uplifting and exhumation of lower-plate rocks, and appearance of supradetachment basin.
文摘Metamorphic core complexes are a basic structural pattern related to extensional tectonics. Several characteristics of different scales of metamorphic core complexes in the Fangshan and Yunmengshan (Beijing) , Zhongtiaoshan (Shanxi) , and Dengfong (Henan) are examined. A three-layer model for metam orphic core complexes is suggested . The conclusion is that metam orphic core complexes are the result of multiphase intracontinental crustal extensions and are an important tectonic pattern. which exposes the basement metam orphic rocks to the ground surface in the intracontinental cover .
基金supported by the National Natural Science Foundation of China(Grant No.41774112)。
文摘Widespread magmatism, metamorphic core complexes(MCCs), and significant lithospheric thinning occurred during the Mesozoic in the North China Craton(NCC). It has been suggested that the coeval exhumation of MCCs with uniform northwest-southeast shear senses and magmatism probably resulted from a decratonization event during the retreat of the paleo-Pacific Plate. Here we used two-dimensional finite element thermomechanical numerical models to investigate critical parameters controlling the formation of MCCs under far-field extensional stress. We observed three end-member deformation modes: the MCC mode, the symmetric-dome mode, and the pure-shear mode. The MCC mode requires a Moho temperature of ≥700 ℃ and an extensional strain rate of ≥5 × 10^(-16)s^(-1), implying that the lithosphere had already thinned when the MCC was formed in the Mesozoic. Considering that the widespread MCCs have the same northwest-southeast extension direction in the NCC, we suggest that the MCCs are surface expressions of both large-scale extension and craton destruction and that rollback of the paleo-Pacific slab might be the common driving force.
文摘This study utilizes ANSYS to establish FEM's model of metamorphic core complex,and used thermal-structure analysis to simulate metamorphic core complex's temperature field and stress field.The metamorphic core complex formation mechanism is discussed.The simulation results show that the temperature field change appearing as the earth surface's temperature is the lowest,and the temperature of metamorphic core complex's nucleus is the highest.The temperature field is higher along with depth increase,and the stress field change appearing as the biggest stress occurs in the nucleus.The next stress field occurs at the top of the cover.
文摘As anticipated from studies of ophiolite complexes,direct investigations of the oceanic crust confirm that basaltic dikes are an integral part of the upper 2 km of the oceanic crust.Currently available information suggests
基金The study is supported by the key project of science and technology of the Ministry of Geology and Mineral Resources (NO .85-01-005-1 )
文摘There is a belt of metamorphic core complexes in the western margin of the Yangtze craton . The geological setting of the belt is similar to that of the Cordilleran metamorphic core complexes . A typical one in this belt is the Jianglang metamorphic core complex , which has a configuration consisting of three layers : a core complex consisting of Mesoproterozoic schist sequence . a ductile middle slab consisting of Paleozoic meta- sedimentary -basalt characterized by the development of ' folding layer' and an upper cover consisting of Xikang Group which has suffered both buckling and flattening . A detachment fault developed along the contact boundary between the cover and basement causes the omission of Upper Sinian and Cambrian at the base of cover . A lot of normal ductile shear zones developed in the cover causes the thinning of it . All the features show that the early extension results in the thinning of crust , but the formation of the dome and exposure of basement rocks may be the results of superimposing of the E-W directed contraction and the following southward thrusting during Indosinian to Yanshanian orogeny . Syntectonic plutonism and pervasive thermo - metamor-phism in the cover suggest that the thermal uplift also causes the uplift of the MCC .
基金The State Key Basic Researchand Development Plan(G1998010100)CAS special financial(STZ97_2_07)
文摘Even though light is the unique source of enengy forphotosynthesis,it can also be hannful to plant,Photoin-hibition occurs when light energy absorption largely ex-ceeds the energy consumption of photosynthetic reactions.Today,the mechanisnu of photoinhibition has become amajor topic of photosynthesis research.It is generally ae-cepted that PS IⅡis affected predominantly by photounhi-bition[1],which causes a loss of electron transfer caparityand oxygen evolution activity,bleaching of pigment,degradation of D,and other proteins,croes-linking be-tween polypeptidesi.
基金Supported by the National Natural Science Foundation of China(No.20872108)
文摘The reaction of a ruthenium carbide complex RuCl2（C：）（PCy3）2 with [H（Et2O）x]＋[BF4]- at a molar ratio of 1：2 produced a two-core ruthenium carbene complex, {[RuCl（=CHPCy3）（PCy3）]2（μ-Cl）3}＋·[BF4]-, in the form of a yellow-green crystalline solid in a yield of 94%. This two-core ruthenium complex is a selective catalyst for ring closing metathesis of unsubstituted terminal dienes. More importantly, no isomerized byproduct was observed for N-substrates when the two-core ruthenium complex was used as the catalyst at an elevated temperature（137 °C）, indicating that the complex is a chemo-selective catalyst for ring closing metathesis reactions.
基金supported by the Open Fund of Hubei Luojia Laboratory (No. 220100033)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB41000000)+1 种基金National Natural Science Foundation of China (Grant Nos. 42174108, 41874094, 42192535 and 42242015)the Young Top-notch Talent Cultivation Program of Hubei Province。
文摘The Earth’s Free Core Nutation(FCN) causes Earth tides and forced nutation with frequencies close to the FCN that exhibit resonance effects.High-precision superconducting gravimeter(SG) and very long baseline interferometry(VLBI) provide good observation techniques for detecting the FCN parameters.However,some choices in data processing and solution procedures increase the uncertainty of the FCN parameters.In this study,we analyzed the differences and the effectiveness of weight function and ocean tide corrections in the FCN parameter detection using synthetic data,SG data from thirty-one stations,and the 10 celestial pole offset(CPO) series.The results show that significant discrepancies are caused by different computing options for a single SG station.The stacking method,which results in a variation of0.24-5 sidereal days(SDs) in the FCN period(T) and 10^(3)-10^(4) in the quality factor(Q) due to the selection of the weighting function and the ocean tide model(OTM),can effectively suppress this influence.The statistical analysis results of synthetic data shows that although different weight choices,while adjusting the proportion of diurnal tidal waves involved,do not significantly improve the accuracy of fitted FCN parameters from gravity observations.The study evaluated a series of OTMs using the loading correction efficiency.The fitting of FCN parameters can be improved by selecting the mean of appropriate OTMs based on the evaluation results.Through the estimation of the FCN parameters based on the forced nutation,it was found that the weight function P_(1) is more suitable than others,and different CPO series(after 2009) resulted in a difference of 0.4 SDs in the T and of 103 in the Q.We estimated the FCN parameters for SG(T=430.4±1.5 SDs and Q=1.52×10^(4)±2.5×10^(3)) and for VLBI(T=429.8±0.7 SDs,Q=1.88×10^(4)±2.1×10^(3)).
