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Acta Geologica Sinica(English Edition) 2021年第5期95卷 1551-1567页

作者： Mohamed Salem KAMAR Nuclear Materials Authority El MaadiCairoP.O.Box 530Egypt

Abu Rusheid area lie in the south of the Eastern Desert of Egypt and comprises(1)ophiolitic mélange,consisting of ultramafic rocks and layered metagabbros in metasedimentary matrix(2)cataclastic group,consisting of protomylonites,mylonites,ultramylonites and silicified ultramylonites(3)monzogranites(4)pegmatite pockets,quartz veins and postgranite *** on the monzogranites and the xenoliths of mylonite rocks from the geochemical and mineralogical points of view introduces a new view about the genesis of the related ***,the monzogranites have a metaluminous character and were crystallized under moderate water-vapor pressure around 3 kb and temperatures of 750–800°*** monzogranites are altered along strike-slip faults exhibiting propylitic,with slightly sodic metasomatism and record high radioactive *** average uranium and thorium(U and Th)contents in fresh monzogranites,mylonite xenolith and altered monzogranites are(7.3,21.20),(40.36,94.82),(60.34 and 347.88 ppm),*** high radioactivities are attributed to the presence of kasolite,uranothorite,cerite,fluorite,zircon,apatite and *** mylonite xenolith is higher in radioactivity than the surrounding fresh monzogranites,reflecting U and Th enrichment before emplacement of the monzogranites,then the latter were subjected to right lateral strike-slip faulting with producing hydrothermal solution rich in Th and U.

关键词： geochemistry mineralogy uranium mylonite monzogranites Wadi Abu Rusheid

Mechanical behaviors of mylonitic granite and granitic protomylonite in a deep ductile shear zone

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2663-2677页

作者： Lanbin Zhang Ru Zhang Li Ren Zhilong Zhang Zetian Zhang Dong Wang Xinzhong Wang Huijun Lu State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering College of Water Resource and HydropowerSichuan UniversityChengdu610065China MOE Key Laboratory of Deep Earth Science and Engineering Sichuan UniversityChengdu610065China China Railway Eryuan Engineering Group Company Ltd.Chengdu610065China School of Architecture and Civil Engineering Xihua UniversityChengdu610065China

For projects near the tectonic belt,mylonite of varying metamorphic degrees may be *** matrix proportion of rock reflects its internal microscopic characteristics,thus it is beneficial for engineering geology to study the effect of the matrix proportion on the mechanical properties and rupture behaviors of *** of mylonitic granite and granitic protomylonite with varying matrix proportions were obtained from a ductile shear zone for a series of uniaxial compression and acoustic emission(AE)*** results showed that with the increase in matrix proportion,the average strength and elastic modulus of the samples increased,and the rock sample with the largest matrix proportion exhibited the maximum peak stress of 244.42 MPa,which was 45.86%greater than the average peak stress of the rock samples with the smallest matrix *** the rock samples with larger matrix proportion,their mechanical parameters exhibited greater dispersion and the large-scale appearance of AE events occurred earlier,showing a relatively gradual failure *** samples had larger accumulated AE parameter values and greater degree of *** contrast,for samples with smaller matrix proportions,the large-scale appearance of AE events occurred close to the peak stress,indicating that the occurrence of damage and fractures was centralized and *** samples had lower accumulated AE parameter values and fewer cracks after ***,for the rock samples with more matrix proportion,the average variance of the b-value was 1.1,which was lower than that of rock samples with the smallest matrix proportion(the average variance of the b-value was 3.7).Furthermore,it can be predicted that under certain stress,the failure depth around a tunnel is generally smaller when the strength of rock samples with larger matrix proportion is greater.

关键词： mylonite Matrix proportion Mechanical properties Acoustic emission(AE) Rupture behaviors

Excess and Radiogenic Argon in High-Pressure mylonites of the Tan-Lu Fault Zone, Eastern China

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Acta Geologica Sinica(English Edition) 2008年第1期82卷 84-98页

作者： XIE Chenglong ZHU Guang WANG Yongshen HU Zhaoqi School of Resource and Environment Engineering Hefei University of Technology Hefei Anhui 230009

Bulk separates of porphyroclastic phengite, neoformed phengite and their mixtures from the Tan-Lu HP mylonites overprinted on the Sulu UHP rocks were analyzed with the 40Ar/39Ar step heating method. Two samples of the neoformed phengite from ultramylonite give 40Ar/39Ar plateau ages of 209.9±1.8 Ma and 214.3±1.8 Ma, which are interpreted as representing cooling times of the TanLu sinistral faulting, and provide geochronological evidence for the syn-orogenic faulting of the Tan-Lu fault zone. The results show that the phengite formed during the retrograde eclogite-facies mylonitization was not contaminated with excess argon and can be used for dating the deformation. Argon closure in previous K-bearing minerals with excess argon under a retrograde HP dry condition is considered to be the reason for lack of excess argon incorporation in the neoformed phengite. Five porphyroclastic phengite samples yield 40Ar/39Ar plateau ages ranging from 666±12 Ma to 307.1±3.3 Ma, which are interpreted as being contaminated with excess argon. Two mixture samples with plateau ages of 239.4±2.1 Ma and 239.3±2.0 Ma show upward-convex age spectra caused by the mixture of older porphyroclastic phengite with excess argon incorporation and younger neoformed phengite without excess argon incorporation. It is demonstrated that excess argon introduced from the previous UHP metamorphism is still preserved in the pre-existing phengite after the Tan-Lu eclogite-facies mylonitization. The intense deformation under HT and HP conditions cannot erase excess argon in the previous phengite totally due to restricted fluid activities. These porphyroclastic phengite previously contaminated with excess argon cannot be used for dating the later HP deformation. This indicates that deformation under a HP dry condition does not play an important role in removing previous 40Are in phengite.

关键词： excess argon phengite mylonite Tan-Lu fault zone 40Ar/39Ar dating

Characteristics of Compositional Migration in mylonites from the Ductile Shear Zones of the Southern Tancheng-Lujiang Fault Belt, Eastern Anhui Province

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Acta Geologica Sinica(English Edition) 1998年第1期72卷 37-50页

作者： YANG Xiaoyong LUI Deliang YANG Xueming WANG Kuiren DAI Jinxing Department of Earth and Space Sciences Advanced Centre for Earth Sciences and AstronomyUniversity of Science and Technology of Chinathe Third World Academy of SciencesHefeiAnhui 230026 Research Institute of Petroleum Exploration and Development China National Petroleum CorporationBeijing 100083

On the basis of field geology, three typical ductile shear zones in the southern part of the Tancheng-Lujiang fault belt have been chosen for a detailed study. Altogether ten samples of the tectonites have been collected for this study. The paper is focused on a comprehensive study of the tectonites in the medium-lower horizons of the ductile shear zones. The mineral compositions of the rocks are analyzed with EPMA and some typical whole-rock samples analyzed by chemical and ICP methods. Based on the comprehensive study of the characteristics of the deformation, the mineral assemblages and the changes of chemical composition of the bulk rocks, this paper presents a discussion on the relationship between the volume loss, the fluid flow and compositional changes during mylonitization of the ductile shear zones in this region. Our study shows that there are a large amount of fluids flowing through the shear zones during the process of mylonization, accompanied by the loss of rock volume and migration of elements and components. Modelling calculation results under different saturation conditions of fluids show that the maximum volume loss of the tectonites is about 60% relative to their protolith, while the fluid/rock ratio ranges from 10 to 103 in different ductile shear zones.

关键词： mylonite ductile shear zones volume loss fluid-rock interaction compositional migration Tancheng-Lujiang fault belt

The characteristics of the structure, strain and kinematic vorticity of the Wulian detachment fault zone, Shandong Peninsula, China

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Science China Earth Sciences 2019年第9期62卷 1399-1415页

作者： Jinlong NI Junlai LIU Yujie SUN Xiaoxiao SHI Shen LI Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals College of Earth Sciences and Engineering Shandong University of Science and Technology Qingdao 266590 China State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing 100083 China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and Technology Qingdao 266071 China Cores and Samples Center of Land & Resources China Geological Survey Langfang 065200 China

As one of the vital tectonic units of the Wulian Metamorphic Core Complex(MCC), the Wulian detachment fault zone(WDFZ), which developed in the Jiaodong peninsula, separates the lower plate of the ultrahigh pressure(UHP) metamorphic rocks in the Sulu orogenic belt from the upper plate of the early Cretaceous Zhucheng basin and the basin basement. The fault zone generally strikes NNE with a dip in the west along the southern portion of the MCC and strikes NE with a dip in the WNWalong the northern portion. The fault zone displays a wavy-tile-shaped extension on the plane, principally composed of the fault breccias and mylonite and transits downward to the mylonitic gneiss. As a whole, the detachment fault zone shows a top-towest or a WNW extension. By calculating the harmonic mean, we obtain a Flynn index K of 0.98–2.0, and the mean value is approximately 1.35 in the fault zone. According to the polar Mohr construction, the extensional crenulation cleavage, the RS/θ,and the quartz C-axial fabric methods, we acquire mean kinematic vorticity values of 0.64–0.97, 0.76–0.93, 0.6–0.92, and 0.63–0.98 with mean values of 0.83, 0.80, 0.78 and 0.86, respectively, for mylonite and promylonite. The strain measurement results and the kinematic vorticity values indicate that the WDFZ is a normal ductile shear zone developed in the extensional *** kinematic track shows that the kinematic vorticity value decreases gradually from the NW to the SE as a whole. A simple shear dominates in the middle and upper parts of the shear zone, which is reflected by a higher vorticity value(>0.75, up to 0.98),a low thinning rate and a lower K value. In contrast, toward the footwall, the pure shear is increased significantly, showing a lower vorticity value(<0.70, low to 0.64), a relatively high thinning rate and a higher K value. Combined with the geotectonic background, the development and evolution of the WDFZ should respond to lithospheric thinning and the destruction of the North China

关键词： Wulian Strain intensity Kinematic vorticity mylonite Detachment fault zone

Grain-size reduction of feldspar and flow of deformed granites within the Gaoligong shear zone, southwestern Yunnan, China

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Science China Earth Sciences 2019年第9期62卷 1379-1398页

作者： Yanlong DONG Shuyun CAO Xuemei CHENG Junlai LIU Hanchen CAO State Key Laboratory of Geological Processes and Mineral Resources School of Earth Sciences China University of Geosciences Wuhan 430074 China State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing 100083 China

Mineral deformation and rock flow mechanism in the lithosphere are related to the rheological behavior and weakening mechanism of the continent. Natural deformation behaviors of feldspars are not well understood due to the complexity of their mineral compositions, crystal structures, as well as changing deformation conditions. The refined microstructure,fabric and composition of major minerals in the deformed granitic rocks within the Gaoligong shear zone(GLGSZ), southwestern Yunnan, China, were studied. With increasing mylonitization, two fabric types of end-members have been distinguished(type-I banded granitic mylonite and type-II banded ultramylonite). The two types of deformed granitic rocks have the same mineral assemblage, but different mineral modes. The type-I banded granitic mylonite has a greater proportion of K-feldspar(mostly present as porphyroclasts)>plagioclase>quartz±biotite, however, the type-II banded ultramylonite has a greater proportion of fine-grained plagioclase>K-feldspar>quartz±biotite. The crystallographic preferred orientation(CPO) patterns of quartz combined with two-feldspar geothermometer, confirm that the quartz grains in the type-I and type-II granitic rock have undergone high-temperature dislocation creep deformation. The K-feldspar grains in the matrix of type-II banded ultramylonite show a dominant(100)[010] slip system with dislocation creep recrystallization, while the fine-grained plagioclase grains present a weak CPO pattern with superplastic flow. The K-feldspar porphyroclasts show grain-size reduction associated with mineral composition and fabric transformation. The myrmekite formation with the fine-grained neocrystallization of plagioclase and quartz significally replaced the K-feldspar porphyroclasts. Finally, the fine-grained neocrystallization plagioclases were formed further into the high strain localized ultramylonites with superplastic flow.

关键词： Feldspar Grain-size reduction EBSD fabric Fluid Myrmekite mylonite Ultramylonite

Strain, Kinematic Vorticity and Ductile Thinning along the Detachment Zone of the Yunmeng Shan Metamorphic Core Complex, Beijing, China

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Acta Geologica Sinica(English Edition) 2013年第4期87卷 989-1004页

作者： LI Jianbo WANG Tao GUO Lei TONG Ying OUYANG Zhixia ZENG Tao Fundamental Science on Radioactive Geology and Exploration Technology Laboratory East China Institute of Technology East China Institute of Technology Institute of Geology Chinese Academy of Geological Sciences Geological Survey Institute Guangdong Nonferrousmetals Geological Survey Bureau

The Yunmeng Shan metamorphic core complex （MCC） is composed of the lower plate, the upper plate and the detachment zone. The detachment zone consists of ductile shear zone （mylonite zone）, chloritized microbreccias zone and the brittle fault plane. The ductile shear zone contains mylonitic rocks, protomylonites, and mylonites. Finite strain measurements of feldspar porphyroclasts from those rocks using the Rf/φ method show that the strain intensities increase from mylonitic rocks （Es=0.66-0.72） to protomylonites （Es=0.66-0.83）, and to mylonites （Es=0.71-1.2）. The strain type is close to flatten strain. Kinematic vorticity estimated by Polar Mohr diagrams suggest that foliations and lineation of mylonite （0.47〈Wk〈0.85） record a bulk simple-dominated general shearing at the initial evolution stage of the Yunmeng Shan MCC＇s detachment zone; and the extensional crenulation cleavage（ecc）（0.34〈Wk〈0.77） recorded a bulk pure-dominated general shearing at the later stage of the evolution. Kinematic vorticity measurements also show that the Yunmeng Shan MCC detachment zone is a result of a combination of simple-dominated general shearing caused by crustal extension at the early stage and pure-dominated general shearing caused by MCC uplifting at the late stage. The ductile thinning estimated by finite strain measurements and estimation of Kinematic vorticity ranges from 52% to 82%, which is the minimum thining estimation. Our studies provide new evidence for mechanisms of the Yunmeng Shan MCC detachement zone.

关键词： Yunmeng Shan MCC detachment zone mylonite Strain Kinematic vorticity the ductilethinning

Pseudotachylyte-Induced Weakness of Plate-Boundary Fault:Insight from the Indus-Tsangpo Suture between India and Asia

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Acta Geologica Sinica(English Edition) 2019年第1期93卷 1-11页

作者： XU Zhiqin JI Shaocheng ZHOU Xin School of Earth Sciences and Engineering Nanjing University Département des Génies Civil Géologique et des Mines école Polytechnique de Montréal Institute of Geology Chinese Academy of Geological Sciences

Although the Indus-Tsangpo Suture(ITS) is the most spectacular thrust system of continent-continent collision in the world, fundamental questions about its strength evolution and deformation behavior transition remain unanswered. Here we reported, for the first time, frictional melting-induced pseudotachylytes in the intensively deformed felsic rocks along the ITS zone in southern Tibet. This study reveals that pseudotachylytes induced profound weakness of the boundary fault between Indian and Asian plates. The intrinsically low strength of the foliated microlites crystallized from frictional melt or glass(i.e., pseudotachylyte) at seismogenic depths compared with the surrounding coarse-grained quartzofeldspathic rocks in the brittle and semi-brittle regime is sufficient to explain the localization of shear strain, the development of ductile shear zones embedded in strong wall rocks, and the transition from the strong to weak fault behaviors without invoking the presence of high fluid pressure or low friction coefficient metasomatic materials(e.g., smectite or lizardite) within the faults.

关键词： pseudotachylyte mylonite fault strength strain localization Indus-Tsangpo suture Tibet

Studies on ^(40)Ar/^(39)Ar thermochronology of strike-slip time of the Tan-Lu fault zone and their tectonic implications

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Science China Earth Sciences 2001年第11期44卷 1002-1009页

作者：朱光宋传中王道轩刘国生徐嘉伟 Department of Resource and Environment Science Hefei University of Technology Hefei China

Samples of mylonite, ultramylonite and phyllonite were collected from 5 localities in the Anhui part of the Tan-Lu fault zone for 40Ar/39Ar chronological studies. Among them 4 samples from 3 localities on the eastern margin of the Dabie orogenic belt yielded 40Ar/39Ar plateau ages of 128 -132 Ma; and 2 samples from the western margin of the Zhangbalin uplift and eastern margin of the Bengbu uplift gave the same 40Ar/39Ar plateau ages of 120 Ma. Isochron analyses and other lines of evidence suggest that the data are reliable. The data are interpreted as cooling ages of sinistral strike-slip deformation of the Tan-Lu fault zone. The younger ages from the north might be related to slower strike-slip rising. These results indicate that the large-scale left-lateral displacement in the Tan-Lu fault zone took place in the Early Cretaceous, rather than in Late Triassic (Indosinian) as proposed by some geologists. Therefore, this fault zone is an intracontinental wrench fault rather than a transform fault or suture line developed during formation of the Dabie orogenic belt.

关键词： Tan-Lu fault zone mylonite 40Ar/39Ar age Early Cretaceous the Dabie-Jiaonan orogenic belt

Strain and kinematic vorticity analysis of the Louzidian low-angle ductile shear detachment zone in Chifeng,Inner Mongolia,China

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Science China Earth Sciences 2010年第11期53卷 1611-1624页

作者： LI JianBo WANG Tao OUYANG ZhiXia Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China East China Institute of Technology Fuzhou 344000China

The Louzidian low-angle ductile shear detachment zone at the south of Chifeng is a SE-dipping, low-angle normal fault system. It is composed mainly of ductile shear zone, ductile-brittle shear zone and brittle fault zone. The ductile shear zone consists of, from bottom to top, mylonitic rocks, protomylonites and mylonites. Finite strain measurement of feldspar strain markers from those rocks using the Rf /φ method shows that strain intensities (Es) of the mylonite at core of the ductile shear zone (Es=0.65-0.96) are higher than those of the mylonitic rocks close to the granite intrusions (Es=0.59-0.62) and of the protomylonites at top of the ductile shear zone (Es= 0.47-0.70), and the strain types of the protomylonites and mylonties are elongate strain and plane-flattening strain, respectively. The kinematic vorticity values (Wk) estimated by the Polar Mohr diagram and the Rigid Grain Net range from 0.81 to 0.90 with an average of 0.85 for the protomylonites, and from 0.53 to 0.80 with 0.66 on average for the mylonites; Wk values of the extensional crenulation cleavage, i.e., C′, estimated by C′ method range from 0.63 to 0.37 with an average of 0.50. The angles between the maximum principal stress and shearing direction determined using the Maximum effective moment criterion evolved from 61° to 69° and to 75°, and finally normal to shearing direction. The results of strain and kinematic vorticity measurements suggest that high strain corresponds to low kinematic vorticity. Kinematic vorticity measurements show that the Louzidian low-angle ductile shear detachment zone is a result of a combination of simple-dominated general shearing at the early stage and pure-dominated general shearing at the late stage. All these, together with isotope geochronology and regional tectonic background, suggest that the Louzidian ductile shear detachment zone resulted from a combination of crust extension and magma intrusion. The model of simple shear at the early stage and pure shear

关键词： Louzidian low-angle ductile shear detachment zone mylonite strain intensity kinematic vorticity principal stress