期刊文献+
共找到2,050篇文章
< 1 2 103 >
每页显示 20 50 100
Observing eddy dye patches induced by shear instabilities in the surf zone on a plane beach
1
作者 Chunping Ren Nannan Fu +2 位作者 Chong Yu Yuchuan Bai Kezhao Fang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2024年第3期15-29,共15页
The effects of surf zone eddy generated by alongshore currents on the deformation and transport of dye are still poorly understood,and related tracer release experiments are lacking.Therefore,a tracer release laborato... The effects of surf zone eddy generated by alongshore currents on the deformation and transport of dye are still poorly understood,and related tracer release experiments are lacking.Therefore,a tracer release laboratory experiment was conducted under monochromatic,unidirectional incident waves with a large incident angle(30°)on a plane beach with a 1:100 slope in a large wave basin.A charge-coupled device suspended above the basin recorded the dye patch image.The evolution of eddy dye patch was observed and the transport and diffusion were analyzed based on the collected images.Subsequently,a linear instability numerical model was adopted to calculate the perturbation velocity field at the initial stage.The observation and image processing results show that surf zone eddy patches occurred and were separated from the original dye patches.Our numerical analysis results demonstrate that the structure of the perturbation velocity field is consistent with the experimental observations,and that the ejection of eddy patches shoreward or offshore may be ascribed to the double vortex. 展开更多
关键词 surf zone tracer release experiment evolution of eddy patch shear instability of alongshore currents
下载PDF
Structural,^(40)Ar/^(39)Ar Geochronological and Rheological Feature Analysis of the Guoxuepu Shear Zone:Indications for the Jitang Metamorphic Complex in the Northern Lancangjiang Zone
2
作者 FENG Yipeng WANG Genhou +5 位作者 WANG Shulai LI Dian WANG Huan LU Yang LIU Han ZHANG Peilie 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2024年第1期32-49,共18页
The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone.Through structural-lithological mapping,structural analysis and laboratory testing,the composition of the Jita... The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone.Through structural-lithological mapping,structural analysis and laboratory testing,the composition of the Jitang metamorphic complex was determined.The macro-and microstructural analyses of the ductile detachment shear zone(Guoxuepu ductile shear zone,2–4 km wide)between the metamorphic complex and the overlying sedimentary cap show that the shear sense of the ductile shear zones is top-to-the-southeast.The presence of various deformation features and quartz C-axis electron backscatter diffraction(EBSD)fabric analysis suggests multiple deformation events occurring at different temperatures.The average stress is 25.68 MPa,with the strain rates(έ)ranging from 9.77×10^(−14)s^(−1)to 6.52×10^(−16)s^(−1).The finite strain of the Guoxuepu ductile shear zone indicates an elongated strain pattern.The average kinematic vorticity of the Guoxuepu ductile shear zone is 0.88,implying that the shear zone is dominated by simple shear.The muscovite selected from the protomylonite samples in the Guoxuepu ductile shear zone yields a 40Ar-39Ar age of 60.09±0.38 Ma.It is suggested that,coeval with the initial Indo–Eurasian collision,the development of strike-slip faults led to a weak and unstable crust,upwelling of lower crust magma,then induced the detachment of the Jitang metamorphic complex in the Eocene. 展开更多
关键词 ^(40)Ar/^(39)Ar dating strain pattern VORTICITY EBSD Guoxuepu shear zone Jitang metamorphic complex
下载PDF
Deformation characteristics of granitic rocks in Erguna ductile shear zone,NE China
3
作者 NWABUEZE Ekene Chibuike LIANG Chenyue +3 位作者 SONG Zhiwei ZHAO jiaqi ENEZE Florence Ego ZHENG Changqing 《Global Geology》 2024年第2期63-75,共13页
The Erguna ductile shear zone is situated in the Erguna Massif,which has been exposed along the eastern bank of the Erguna River in northeastern China.The authors present comprehensive study results on the macro-and m... The Erguna ductile shear zone is situated in the Erguna Massif,which has been exposed along the eastern bank of the Erguna River in northeastern China.The authors present comprehensive study results on the macro-and micro-structures,finite strain and kinematic vorticity,quartz electron backscatter diffraction(EBSD)fabrics,and geochronology of granitic rocks in the Erguna ductile shear zone.The deformed granitic rocks have experienced significant SE-trending dextral strike-slip shearing.Finite strain and kinematic vorticity in all deformed granitic rocks indicate that the deformation is characterized by simple sheardominated general shearing with S-L tectonites.Mineral deformation behaviors and quartz C-axis textures demonstrate that the deformed granitic rocks developed under greenschist to amphibolite facies conditions at deformation temperatures ranging from 450 to 550℃.New LA-ICP-MS zircon U-Pb ages indicate that these granitic rocks were formed in Early Triassic(~248.6 Ma)and Early Cretaceous(~136.7 Ma).All the evidence indicates that this deformation may have occurred in Early Cretaceous and was related to the compression resulting from the final closure of the Mongol-Okhotsk Ocean. 展开更多
关键词 zircon U-Pb dating EBSD analysis finite strain kinematic vorticity Erguna ductile shear zone
下载PDF
Characterizing large-scale weak interlayer shear zones using conditional random field theory
4
作者 Gang Han Chuanqing Zhang +5 位作者 Hemant Kumar Singh Rongfei Liu Guan Chen Shuling Huang Hui Zhou Yuting Zhang 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2023年第10期2611-2625,共15页
The shear behavior of large-scale weak intercalation shear zones(WISZs)often governs the stability of foundations,rock slopes,and underground structures.However,due to their wide distribution,undulating morphology,com... The shear behavior of large-scale weak intercalation shear zones(WISZs)often governs the stability of foundations,rock slopes,and underground structures.However,due to their wide distribution,undulating morphology,complex fabrics,and varying degrees of contact states,characterizing the shear behavior of natural and complex large-scale WISZs precisely is challenging.This study proposes an analytical method to address this issue,based on geological fieldwork and relevant experimental results.The analytical method utilizes the random field theory and Kriging interpolation technique to simplify the spatial uncertainties of the structural and fabric features for WISZs into the spatial correlation and variability of their mechanical parameters.The Kriging conditional random field of the friction angle of WISZs is embedded in the discrete element software 3DEC,enabling activation analysis of WISZ C2 in the underground caverns of the Baihetan hydropower station.The results indicate that the activation scope of WISZ C2 induced by the excavation of underground caverns is approximately 0.5e1 times the main powerhouse span,showing local activation.Furthermore,the overall safety factor of WISZ C2 follows a normal distribution with an average value of 3.697. 展开更多
关键词 Interlayer shear weakness zone Baihetan hydropower station Conditional random field Kriging interpolation technique Activation analysis
下载PDF
Petrology, Age and Geodynamic Implication of the Panafrican Granitoids Associated with the Glito-Kpatala Shear Zone (South-East Togo)
5
作者 Gnanwasou Alayi Sarakawa Abalo Malibida Kpanzou +3 位作者 Yao Agbossoumondé Essodina Padaro René-Pierre Menot Mahaman Sani Tairou 《International Journal of Geosciences》 2023年第12期1193-1225,共33页
The granitic plutons associated with the Glito-Kpatala shear zone are composed of biotite and amphibole granodiorites, biotite granites, two-mica granites and aplitic granites, which are very poorly represented. The c... The granitic plutons associated with the Glito-Kpatala shear zone are composed of biotite and amphibole granodiorites, biotite granites, two-mica granites and aplitic granites, which are very poorly represented. The chemical and mineralogical compositions of these facies indicate that they are I type and belong to high-K calc-alkaline series, with a chemical metaluminous character displayed by the granodiorites relative to the biotite and two-mica facies whose chemical compositions vary between metaluminous and peraluminous caracter. The Th/Ta (14.04 - 43.82 ppm, mean = 26.05), Th/U (2.58 to 15.05 ppm, mean = 5.85 ppm), Zr/Hf (25.27 to 37.21, mean = 30.67 ppm) and Rb/Sr (0.16 to 4.32;mean = 1.67 ppm) ratios of these granitoids reveal a strong crustal involvement in their magmatogenesis. Variations in CaO/Na<sub>2</sub>O (0.47 - 1.44 ppm), Rb/Sr (0.14 - 0.27 ppm), Rb/Ba (0.07 - 0.14 ppm) and Sr/Y (38.21 - 174.42 ppm) ratios indicate that biotite and amphibole granodiorites with their excessive Ni (135.37 - 139.51 ppm) and Cr (395.73 - 447.74 ppm) were derived from a mafic to intermediate lower continental crust where garnet and/or amphibole were stable residual assemblage minerals. The moderate Sr/Y ratios (1.81 - 9.47 ppm) and low transition elements Ni (1 - 6.44 ppm) and Cr (7.89 - 13.47 ppm) contents in both the two-mica and biotite granites are consistent with their emplacement at relatively shallow depths in the upper to mean continental crust, at pressures below 10 Kbar. In the two-mica granites, moderate CaO/Na<sub>2</sub>O (0.20 - 0.57 ppm, mean = 0.38 ppm) and Rb/Ba (0.39 - 1.37, mean = 0.84 ppm) ratios and quite varied Rb/Sr (1.53 - 4.23 ppm, mean = 2.85 ppm) ratios indicate a predominant derivation from psammitic and pelitic metasediments rather than metagreywackes. These low ratios (0.25 ≤ CaO/Na<sub>2</sub>O ≤ 0.32, mean = 0.28 ppm;0.31 ≤ Rb/Ba ≤ 0.44, mean = 0.39 ppm;1.11 ≤ Rb/Sr ≤ 1.78, mean = 0.39 ppm) in biotite granites are more consistent with melting from a metagreywacke-derived source. Evidence for the contribution of mantle-derived mafic magma with granitic magma in the plutons studied is materialized by the presence of magmatic enclaves in both granodiorites and two-mica granites, the volcanic arc geochemical signatures displayed by the plutons in geotectonic diagrams and Nb/Ta ratios (14.14 - 34.61 ppm) closer to mantle estimates. Geochemical data and radiometric dating elements suggest that the granitoids studied can be integrated into the pan-African late magmatic episode, which corresponds between 606 and 583 Ma, to the activity of transcurrent ductile strike-slips and to the synchronous emplacement of high K calc-alkaline plutons in a post-collisional context. 展开更多
关键词 Pan-African Granitoids Post-Collisional shear zone South-East Togo
下载PDF
Boulder-induced form roughness and skin shear stresses in a gravel-bed stream
6
作者 DAS Ratul DATTA Akash 《Journal of Mountain Science》 SCIE CSCD 2024年第1期346-360,共15页
Boulder spacing in mountain rivers and near-wake flow zones within the boulder array is very useful for fish habitat and growth of aquatic organisms.The present study aims to investigate how the boulder array and spac... Boulder spacing in mountain rivers and near-wake flow zones within the boulder array is very useful for fish habitat and growth of aquatic organisms.The present study aims to investigate how the boulder array and spacing influence the near-bed flow structures in a gravel-bed stream.Boulders are staggered over a gravel-bed stream with three different inter-boulder spacing namely(a)large(b)medium and(c)small spacing.An acoustic Doppler velocimeter was used for flow measurements in a rectangular channel and the results were compared with those acquired from numerical simulation.The time-averaged velocity profiles at the near-wake flow zones of boulders experience maximum flow retardation which is an outcome of the boulder-induced form roughness.The ratio of velocity differences associated to form and skin roughness and its positive magnitude reveals the dominance of form roughness closest to the boulders.Form roughness computed is 1.75 to 2 times higher than the skin roughness at the near-wake flow region.In particular,the collective immobile boulders placed at different inter-boulder spacings developed high and low bed shear stresses closest to the boulders.The low bed shear stresses characterised by a secondary peak developed at the trough location of the boulders is attributed to the skin shear stress.Further,the spatial averaging of time-averaged flow quantities gives additional impetus to present an improved illustration of fluid shear stresses.The formation of form-induced shear stress is estimated to be 17%to 23%of doubleaveraged Reynolds shear stress and partially compensates for the damping of time-averaged Reynolds shear stress in the interfacial sub-layer.The quadrant analysis of spatial velocity fluctuations depicts that the form-induced shear stresses are dominant in the interfacial sub-layer and have no significance above the gravel-bed surface. 展开更多
关键词 Array of boulders Near wake flow zones Velocity distributions Skin roughness Form induced shear stresses
下载PDF
Structural and Geochronological Evidence for Multiple Episodes of Tertiary Deformation along the Ailaoshan-Red River Shear Zone, Southeastern Asia, Since the Paleocene 被引量:27
7
作者 ZHANG Jinjiang ZHONG Dalai +1 位作者 SANG Haiqing ZHOU Yong 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2006年第1期79-96,共18页
Structural analyses show that the Ailaoshan-Red River shear zone (ASRRSZ) in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip exper... Structural analyses show that the Ailaoshan-Red River shear zone (ASRRSZ) in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip experienced by the ASRRSZ. The first episode of such deformation occurred throughout the eastern high-grade belt of the ASRRSZ under a transtensional regime and produced L- type tectonites of amphibolite grade. The second episode of left-lateral slip formed high strain zones overprinting the high-grade belt. Its deformational mechanism is similar to simple shear and the deformed rocks are L-S mylonites of greenschist grade. The third episode of left-lateral slip took place chiefly in a western low-grade belt of the ASRRSZ. This deformation occurred in a transpressional regime, formed an overall structure pattern of a sinistral thrust system and produced phyllonites of low-greenschist grade. Geochronological data indicated that the three episodes of left-lateral slip happened before ~58-56 Ma, at least from ~27 Ma to 22 Ma and at ~13-12 Ma respectively. The first episode of slip in the ASRRSZ appeared to correspond to the initial collision of India and Asia at ~60 Ma. The second episode took place almost at the same time as the most intensive compression and uplift in Tibet. The latest event might represent a further eastward material flow in Tibet after ~16-13 Ma. Thus, the ASRRSZ of southeastern Asia probably experienced three main episodes of Tertiary left- lateral slip in the course of intracontinental convergence since the India-Asia collision. 展开更多
关键词 Ailaoshan-Red River shear zone southeastern Asia GEOCHRONOLOGY deformation history India-Asia collision
下载PDF
High Temperature Strain Structures and Quartz C-Axis Fabrics from Mylonitic Rocks in the Ailaoshan-Red River Shear Zone,Yunnan,and Their Tectonic Implication 被引量:12
8
作者 LIU Junlai TANG Yuan XIA Haoran GUO Qiang TRAN My Dung CAO Shuyun WU Hujun WU Wenbin ZHANG Zhaochong ZHAO Zhidan 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2010年第6期1377-1390,共14页
The Ailaoshan-Red River(ASRR) shear zone is one of the major Southeast Asian tectonic discontinuities that have figured the present tectonic framework of the eastern Tibet.Several metamorphic massifs are distributed... The Ailaoshan-Red River(ASRR) shear zone is one of the major Southeast Asian tectonic discontinuities that have figured the present tectonic framework of the eastern Tibet.Several metamorphic massifs are distributed linearly along the shear zone,e.g.Xuelongshan,Diancangshan, Ailaoshan and Day Nui Con Voi from north to south.They bear a lot of lines of evidence for the tectonic evolution of the eastern Tibetan at different crustal levels in different tectonic stages.Controversy still exists on the deformation structures,microstructures and their relationship with metamorphisms along the ASRR.In this paper detailed microstructural and EBSD(Electron Backscattered Diffraction) fabric analysis of some highly sheared granitic rocks from different massifs along the ASRR are conducted.High temperature structures and microstructures are preserved in unsheared gneisses,in weakly sheared xenoliths or in some parts of the highly sheared rocks(mylonites).Several types of high temperature quartz c-axis fabrics show symmetrical patterns or transitions from symmetrical to asymmetrical patterns.The former are attributed to coaxial deformation during regional shortening in an early stage of the Indian-Eurasian tectonic interaction and the latter are related to the transitions from coaxial compression to noncoaxial shearing during the post-collisional ASRR left lateral shearing. 展开更多
关键词 high temperature deformation quartz fabrics shortening deformation Ailaoshan-Red River shear zone southeastern Tibet
下载PDF
New Zircon U-Pb Geochronology of the Post-kinematic Granitic Plutons in the Diancang Shan Metamorphic Massif along the Ailao Shan-Red River Shear Zone and Its Geological Implications 被引量:9
9
作者 CAO Shuyun LIU Junlai +1 位作者 Bemd LEISS ZHAO Chunqiang 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2010年第6期1474-1487,共14页
The Ailao Shan-Red River fault zone is the boundary between the Yangtze block to the northeast and the Indochina block to the southwest.It is an important tectonic zone due to its role in the southeastward extrusion o... The Ailao Shan-Red River fault zone is the boundary between the Yangtze block to the northeast and the Indochina block to the southwest.It is an important tectonic zone due to its role in the southeastward extrusion of the Indochina block during and subsequent to the Indian-Eurasian collision.Diancang Shan(DCS) high-grade metamorphic complex,located at the northwest extension along the Ailao Shan-Red River(ASRR) shear zone,is a representative metamorphic complex of the ASRR tectonic belt.Structural and microstructural analysis of sheared rocks in the high-grade metamorphic rocks reveals that they are coherent with solid-state high-temperature ductile deformation,which is attributed to left-lateral shearing along the ASRR shear zone.New LA-ICP-MS zircon U-Pb geochronological and microstructural studies of the post-kinematic granitic plutons provide a straightforward time constraint on the termination ductile left-lateral shearing and exhumation of the metamorphic massif in the ASRR shear zone.It is suggested that the left-lateral shearing along the ASRR shear zone ended at ca.21 Ma at relative lower-temperature or decreasing temperature conditions.During or after the emplacement of the young dikes at ca.21 Ma,rapid brittle deformation event occurred,which makes the DCS massif start fast uplift/exhumation and cooling to a shallow crustal level. 展开更多
关键词 high-temperature mylonites Diancang Shan metamorphic massif Ailao Shan-Red River shear zone timing of left-lateral ductile shearing GEOCHRONOLOGY
下载PDF
Structures of Syn-deformational Granites in the Longquanguan Shear Zone and Their Monazite Electronic Microprobe Dating 被引量:9
10
作者 ZHANG Jinjiang ZHAO Lan LIU Shuwen 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2006年第6期864-874,共11页
The Longquanguan shear zone is an important structural belt in the North China Craton, separating the underlying Fuping complex from the overlying Wutai complex. This shear zone has experienced three episodes of defor... The Longquanguan shear zone is an important structural belt in the North China Craton, separating the underlying Fuping complex from the overlying Wutai complex. This shear zone has experienced three episodes of deformation: the first and main episode is a ductile top-to-ESE shear along the gently northwest-west dipping foliations, while the other two episodes are later collapse sliding. Prolonged granites parallel to the shear foliations make one of the main compositions of the Longquanguan shear zone. These granites experienced deformation to form mylonitic rocks when they emplaced during the first episode of deformation. Structural characters of the granites and their contacts to the country rocks indicate that these granites possibly resulted from in-situ partial remelting by shearing, i.e., they are syn-deformational granites. Monazites in these mylonitic granites are magmatic minerals and their crystallization ages may represent ages of the magmatic events, and also the ages for the main deformation of the Longquanguan shear zone. Monazite electronic microprobe dating were carried on two samples of granite, which gives multiple peak ages, among which 1,846 Ma and 1,877 Ma are the main peak ages for the two samples. These ages represent the main deformation of the Longquanguan shear zone, which is consistent with the main regional geological event at about 1,850 Ma caused by the collision between the Eastern and Western Blocks in North China. The good match between the monazite ages and the corresponding regional tectono-thermal events shows the feasibility and reliability of monazite electronic microprobe dating. 展开更多
关键词 Longquanguan shear zone syn-deformational granite monazite electronic microprobe dating
下载PDF
A Large Ductile Sinistral Strike-Slip Shear Zone and Its Movement Timing in the South Qilian Mountains, Western China 被引量:4
11
作者 许志琴 李海兵 +4 位作者 陈文 吴才来 杨经绥 金小赤 陈方远 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2002年第2期183-193,共11页
There is a large ductile shear zone, 2 km wide and more than 350 km long, inthe South Qilian Mountains, western China. It is composed of volcanic, granitic and calcareousmylonites. The microstructures of the ductile s... There is a large ductile shear zone, 2 km wide and more than 350 km long, inthe South Qilian Mountains, western China. It is composed of volcanic, granitic and calcareousmylonites. The microstructures of the ductile shear zone show nearly E-W extending subverticalfoliation, horizontal and oblique stretching lineations, shearing sense from sinistral to obliquesinistral strike-slip from east to west, 'A' type folds and abundant granitic veins. Measuredlattice preferred orientations (LPOs) of the mylonitic and recrystallized quartz of the graniticmylonite in the west segment suggest a strong LPO characterized by the dominant slip systems (1010) formed at high temperature (>650 deg C). K-feldspar of the mylonite shows an ^(39)Ar/^(40)Arhigh-temperature plateau age of 243.3 +- 1.3 Ma, and biotite, 250.5 +- 0.5 Ma, which represent theformation age of the ductile shear zone. The ^(39)Ar/^(40)Ar plateau ages of 169.7 +- 0.3 Ma and160.6 +- 0.1 Ma and the ^(39)Ar/^(40)Ar isochron ages of 166.99 +- 2.37 Ma and 160.6 +- 0.1 Ma ofbiotites in the mylonite represent the subsequent deformation age. These ages indicate that thisductile shear zone is similar to the Altun and South Kunlun sinistral ductile shear zones in itsages of movement, formation, reactivation and duration. 展开更多
关键词 Early Triassic ductile sinistral shear zone high-temperature LPO SouthQilian
下载PDF
Fluid-Rock Interaction of Shear Zones in Continental Crust:as Evidenced by Xincheng-Xishui and Hetai Shear Zones 被引量:4
12
作者 Zhong Zengqiu You Zhendong Xu QidongFaculty oj Earth Sciences, China University of Geosciences, Wuhan 430074 《Journal of Earth Science》 SCIE CAS CSCD 1995年第2期18-22,共5页
There is a coupling of thermal, mechanical, chemical and fluidal processes in a continental shear zone. Both Xincheng - Xishui and Hetai shear zones are typical continental crust shear zones of greenschist facies envi... There is a coupling of thermal, mechanical, chemical and fluidal processes in a continental shear zone. Both Xincheng - Xishui and Hetai shear zones are typical continental crust shear zones of greenschist facies environment. The representative mylonite zones of the shear zones are studied with whole rock major and trace element analyses. The chemical compositional variation tendencies in both shear zones are very similar and the gain - loss ratios of various components in the mylonitic rocks are reflected in the mass balance equations. The enrichment of those immobile high - field- strengh elements is considered to be related to the volume loss of the mylonitic rocks in a shear zone. Based on the volume loss expression Cs /Co = 1/(1- V), the fractional volume losses (V) are 37.5% and 36.5%-42.3% respectively for mylonites and ultramylonites in the Xincheng-Xishui shear zone and 11 % and 28% respectively for mylonites and phyllonites in the Hetai shear zone. The high volume loss and large removal of SiO2 from the system imply that there is a large amount of percolating fluids in the shear zones. From the SiO2 loss, the fluid/rock ratios (N) are calculated as Nmyl = 113 - 563, Nultramyl= 133-664 for the Xincheng-Xishui shear zone and Nmyl=42-208, Nphyl=110-550 for the Hetai shear zone. Such a large amount of percolating fluid must have profoundly affected the rheological behavior, chemical behavior and metallogenesis of the shear zones. 展开更多
关键词 continental shear zone chemical compositional variation volume loss flu-id/rock ratio.
下载PDF
A Uniform Orogen-parallel Extension System of the Shear Zones in the Tongbai-Dabie Orogenic Belt, Central China 被引量:3
13
作者 LIU Huan LIN Shoufa SONG Chuanzhong 《Acta Geologica Sinica(English Edition)》 CAS CSCD 2018年第2期556-567,共12页
Large-scale magmatism affected the Tongbai-Dabie orogenic belt during post-collisional lateral tectonic extension in the Cretaceous, which was suggested to account for the widespread deformation and migmatization in t... Large-scale magmatism affected the Tongbai-Dabie orogenic belt during post-collisional lateral tectonic extension in the Cretaceous, which was suggested to account for the widespread deformation and migmatization in the Tongbai-Dabie complexes. However, it cannot explain the most deformations in the shear zones. The northwest-southeast shear zones are developed around or wrapped the Tongbai-Dabie complexes. They play an important role for the interpretation of the tectonic evolution of the Tongbai-Dabie orogenic belt. By a systematically observation and description of the geometry and kinematics of these shear zones, we found that the shear zones to the north dip NE and have a uniform sinistral shear sense, the shear zone to the south dips SW and has a uniform dextral shear sense, and the shear zones at the core are sub-horizontal and have a uniform top-to-NW sense of shear. Combining with the comparison of previous and our geochronological studies, we interpret these associations as indicating that these shear zones were originally a single, more flat-lying and sub- horizontal shear zone with a uniform top-to-NW shear sense before the folding-doming of the Tongbai- Dabie complexes and suggest that the Tongbai-Dabie orogenic belt experienced a uniform top-to-NW orogen-paraUel extension in the ductile lithosphere before the widespread magmatism in the Cretaceous. 展开更多
关键词 Tongbai-Dabie orogenic belt shear zone Tongbai complex Dabie complex orogen-parallel extension
下载PDF
Analysis of the Ore-Controlling Structure of Ductile Shear Zone Type Gold Deposit in Southern Beishan Area, Gansu, Northwest China 被引量:3
14
作者 陈柏林 吴淦国 +3 位作者 叶德金 刘晓春 舒斌 杨农 《Journal of China University of Geosciences》 SCIE CSCD 2007年第1期30-38,共9页
The ductile shear zone-type gold deposit is a kind that both the ore-forming mechanism and ore-controlling factors are closely related to the ductile shear zone and its evolution. Ductile shear zone develops in Beisha... The ductile shear zone-type gold deposit is a kind that both the ore-forming mechanism and ore-controlling factors are closely related to the ductile shear zone and its evolution. Ductile shear zone develops in Beishan area, Gansu of Northwest China, and develops especially well in the south belt. The controls of the ductile shear zone on gold deposits are as follows. (1) The regional distribution of gold deposits (and gold spots) is controlled by the ductile shear zone. (2) The ductile-brittle shear zone is formed in the evolution process of ductile shear zone and both are only ore-bearing structures and control the shape, attitude, scale, and distribution of mineralization zones and ore-bodies. (3) Compresso-shear ductile deformation results in that the main kind of gold mineralization is altered mylonite type and the main alteralization is metasomatic. (4) Ore-bearing fracture systems are mainly P-type ones, some D-type and R-type ones, but only individual R'-type and T-type ones. (5) Dynamic differen- tiation and dynamic metamorphic hydrothermal solution resulting from ductile deformation is one of the sources of ore-forming fluid of gold mineralization, and this is identical with that ore-forming materials are mainly from metamorphic rocks, and ore-forming fluid is mainly composed of metamorphic water, and with the fluid inclusion and geo-chemical characteristics of the deposit. (6) There is a negative correlation between the gold abundance and susceptibility anlsotropy (P) of the altered mylonlte samples from the deposit, which shows that the gold mineralization is slightly later than the structural deformation. All above further expound the ore-forming model of the ductile shear zone type of gold deposits. 展开更多
关键词 analysis of ore.controlling structure gold deposit ductile shear zone Beishanarea of Gansu Northwest China
下载PDF
Transportation of REE in the Ductile Shear Zone in Hetai Gold Deposit, Guangdong Province 被引量:2
15
作者 杨凤根 王鹤年 华仁民 《Journal of Rare Earths》 SCIE EI CAS CSCD 2003年第6期680-685,共6页
The REE transportation in two sorts of mylonites of ductile shear zone, in Hetai gold deposit, Guangdong province was studied. The results show that there is REE compositional variation regularly in the ductile shear ... The REE transportation in two sorts of mylonites of ductile shear zone, in Hetai gold deposit, Guangdong province was studied. The results show that there is REE compositional variation regularly in the ductile shear zone. When mica-quartz schist and migmatite are changing into mylonites or ultramylonites, i.e., along with intensifying deformation, the contents of each rare earth element and the total contents of the LREE, HREE and REE increase or decrease regularly, but the REE patterns of the rock are accordant. The isocon diagram of the tectonic rocks before and after deformation shows that the REE compositional variation of the mylonites or ultramylonites are very small, but there is a few REE moving in or out in the rock deformation. The reason of the REE compositional variation is that there are volume change and fluid flow in the rock deformation, and it leads to the LREE relative enrichment and HREE relative loss. 展开更多
关键词 GEOCHEMISTRY REE compositional variation ductile shear zone Hetai gold deposit Guangdong province
下载PDF
Sequence of Ductile Shear Zones in UHP Metamorphic Province with in Dabie Massif,China 被引量:2
16
作者 Suo Shutian Zhong Zengqiu Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074 《Journal of Earth Science》 SCIE CAS CSCD 1998年第3期3-9,共7页
Structural studies in the Dabie massif show that distribution of strain is extremely heterogeneous and illustrates the pattern of deformation partitioning in the ultra high pressure (UHP) metamorphic province on all ... Structural studies in the Dabie massif show that distribution of strain is extremely heterogeneous and illustrates the pattern of deformation partitioning in the ultra high pressure (UHP) metamorphic province on all scales. Based on the field structural analysis along with microstructural observation, at least five widespread episodes of ductile shear zone systems are identified by using geometric, kinematic and rheological indicators and they constitute a shear zone sequence in the UHP metamorphic province within the Dabie massif (DM), China. Each shear zone system, for example, the UHP eclogite facies shear zone system in the sequence, exhibits its own features including geometric styles, mineral assemblages, metamorphic pt conditions and deformation regimes during the formation of such shear zone system. Detailed macro and micro scopical features of different episodes of the shear zones are given with respect to mechanism of strain localization and deformation partitioning. The tectonic significance during the creation and exhumation of the UHP metamorphic rocks is evaluated briefly, as well. It is argued that the ductile shear zones in the UHP metamorphic province play an important role in the Dabie mountain building geodynamic process. 展开更多
关键词 ductile shear zone UHP metamorphic province exhumation deformation partitioning Dabie massif.
下载PDF
Mineral Chemistry of Two-Mica Granite Rare Metals: Impact of Geophysics on the Distribution of Uranium Mineralization at El Sela Shear Zone, Egypt 被引量:2
17
作者 Ibrahim Gaafar Michel Cuney Ahmed Abdel Gawad 《Open Journal of Geology》 2014年第4期137-160,共24页
The present work aims at identifying Nb-Ta-, Zr-Hf-, REE-, Th-U-bearing two-mica granite from geological, geophysical cross-sections and mineral chemistry studies from three boreholes at G. El Sela shear zone. Microsc... The present work aims at identifying Nb-Ta-, Zr-Hf-, REE-, Th-U-bearing two-mica granite from geological, geophysical cross-sections and mineral chemistry studies from three boreholes at G. El Sela shear zone. Microscopically, the three boreholes are composed mainly of two-mica granite. They are composed of K-feldspar, plagioclase, quartz, biotite and muscovite. Accessories are pyrite, zircon, fluorite, rutile, monazite with Th-U-mineralization identified by scanning electron microscope (SEM) and electron probe-microanalyses (EPMA). Chlorite, muscovite, sericite, kaolinite are secondary minerals. Geochemically, two-mica granite boreholes are A-type granites and peraluminous characteristics. They are enriched in large ion lithophile elements (LILE;Ba, Rb and Sr), high field strength elements (Y, Zr and Nb), and LREE but depleted in HREE with negative Eu anomaly. U-enrichment associated with chloritization, muscovitization, albitization, sericitization, kaolinization and argillization results from convective hydrothermal circulation of fluids through brittle structures along the ENE-WSW main shear zone. The ratios Nb/Ta (7.7 - 17.7) and Zr/Hf (16.9 - 26.4) are relatively enriched in the lighter isovalents Ta and Hf. The accessory minerals observed in the two-mica granites are represented by metallic sulfides (pyrite, arsenopyrite, chalcopyrite, galena and sphalerite), Nb-rutile, Hf-zircon, fluorite, monazite, columbite, betafite, thorite, phosphothorite, uranothorite, brannerite, uraninite, coffinite and pitchblende at G. El Sela shear zone. Uraninite with a low Th content indicates a hydrothermal origin of U-mineralization, Thorite, uranothorite, monazite and zircon is the main uranium bearing minerals of magmatic origin within the enclosing granite. The primary U-mineralization has been observed in two boreholes. In order to illustrate the geophysical signature of El Sela U-mineralization, the radiometric, magnetic, and VLF-EM data as well as radon concentration are included. The magnetic, electrical conductivity and radiometric profiles were produced from detailed ground surveys. The shear zone is characterized by relatively weak levels for both K and eTh, but very high eU anomalies (<3500 ppm), Therefore, the Sela shear zone acts as a good trap for U-mineralization. The Sela Shear zone coincides with positive conductivity anomalies, which are the most prominent features on the respective profiles. The magnetic field over the Sela shear zone is also conspicuous by the sharp contrast which makes with the strong negative signatures of the altered microgranite. The radon distribution map showed the presence of seven high anomalies that are mostly controlled by the structures due to the easy movement of radon through them. 展开更多
关键词 BOREHOLES shear zone RADON Spectrometric Magnetic CONDUCTIVITY
下载PDF
Timing of the Early Paleozoic Yangtze and Cathysian Convergence: Constraint from U-Pb Geochronology of Hydrothermal Zircons from Mafic Mylonite within the Shoucheng-Piaoli Ductile Shear Zone, Northern Guangxi 被引量:8
18
作者 QIN Ya FENG Zuohai +2 位作者 HU Rongguo LI Saisai WANG Chunzeng 《Acta Geologica Sinica(English Edition)》 CAS CSCD 2018年第5期2030-2031,共2页
Objective The northern Guangxi region is in the southwestern part of the Southern China continent,which is located at the junction of the southwest section of the Early Paleozoic Yangtze block and Cathaysian block.A s... Objective The northern Guangxi region is in the southwestern part of the Southern China continent,which is located at the junction of the southwest section of the Early Paleozoic Yangtze block and Cathaysian block.A series of NNE-trending ductile shear zones are developed in this region,and these ductile shear zones are mostly previously suggested boundary faults of the Early Paleozoic Yangtze block and Cathaysian block,such as the Shoucheng–Piaoli ductile shear zone in Northern Guangxi (Meng Yuanku et al., 2016; Zhang Xuefeng et al., 2015). 展开更多
关键词 Pb Th Northern Guangxi Timing of the Early Paleozoic Yangtze and Cathysian Convergence Constraint from U-Pb Geochronology of Hydrothermal Zircons from Mafic Mylonite within the Shoucheng-Piaoli Ductile shear zone
下载PDF
Tectonic Dynamic Metallization of Silver-GoldHydrothermal Fluids in Proterozoic GneissTerrene Shear Zones, Suichang, Zhejiang, China 被引量:1
19
作者 Wang Siyuan Xiao Qibing Zeng Jianguo Faculty of Earth Resources, China University of Geosciences, Wuhan 430074 《Journal of China University of Geosciences》 SCIE CSCD 2001年第1期68-74,共7页
The Suichang mine is the largest silicified vein-type silver-gold mineralization system in Southeast China, whose ore bodies are controlled by shear zones developing in Lower Proterozoic gneiss terrene with initial mi... The Suichang mine is the largest silicified vein-type silver-gold mineralization system in Southeast China, whose ore bodies are controlled by shear zones developing in Lower Proterozoic gneiss terrene with initial migmatization, which is covered by Upper Jurassic and Lower Cretaceous volcanic rock system and cut by acidic igneous veins of Jurassic and Cretaceous. The conclusions are as follows: (1) The ore-forming fluid is defined as superhigh tectonic-metamorphic fluid on the base of : 1 (D)-(18O) values 2 fluid inclusions;3 trace elements of pyrite from ores. (2) The shear zone silicified orebod-ies occurred in proterozoic, Jurassic and Cretaceous, which have been transforms in part by ore-bearing comb quartz vein of volcanism. 展开更多
关键词 tectonic dynamic metallization silver-gold hydrothermal fluids Proterozoic gneiss terrene shear zone Suichang field Cathaysian plate.
下载PDF
Structural,Kinematic and Geochronological Study of the Main Tianshan Shear Zone in the Borohoro Ranges,NW China 被引量:1
20
作者 LIU Tianlun CHEN Siyu +5 位作者 ZHANG Bo CAI Keda HAN Baofu QU Junfeng GUO Lei WANG Meng 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2021年第5期1431-1455,共25页
The western segment of the Main Tianshan shear zone(MTSZ)branches into three major dextral strike-slip shear zones in the Borohoro Ranges,northwestern China.Mylonitic rocks within these zones exhibit vertical foliatio... The western segment of the Main Tianshan shear zone(MTSZ)branches into three major dextral strike-slip shear zones in the Borohoro Ranges,northwestern China.Mylonitic rocks within these zones exhibit vertical foliations,subhorizontal lineations,and dextral kinematics.The microstructures and CPO patterns of calcite and quartz in the tectonites suggest shearing at temperatures of 200℃ to 500℃ or above.The amount of dextral displacement along the zones is less than 100 km.LA-ICP-MS U-Pb dating of zircons from some pre-kinematic granites gave ages of 364-325 Ma and 316 Ma,and zircons from a syn-kinematic leucogranite gave an age of 291 Ma.We propose that dextral shearing along the MTSZ started in the earliest Permian.Our data indicate that collision between the Yili and Junggar plates might have finished before 325 Ma or 316 Ma,with a tectonic transformation from 325 Ma to 300 Ma,resulting in intracontinental transpression from 300 Ma or 291 Ma.We suggest that the formation of the Kazakhstan orocline(KO)took place in two stages,with the early stage of bending driven by convergence related to oblique subduction,and the late stage possibly associated with lateral disarticulation as a result of the dextral strike-slip shear zones. 展开更多
关键词 structural geology geochronology dextral shearing CPO pattern Late Paleozoic Main Tianshan shear zone Yili-North Tianshan
下载PDF
上一页 1 2 103 下一页 到第
使用帮助 返回顶部