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Microstructures, Fabrics, and Seismic Properties of Mylonitic Amphibolites: Implications for Strain Localization in a Thickening Anisotropic Middle Crust of the North China Craton

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Journal of Earth Science 2024年第3期35卷 769-785页

作者： Siqi Liu Bo zhang jinjiang zhang Jian zhang Lei Guo Tao Wang Baoyou Hang Xiaorong Li Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China Department of Earth Sciences The University of Hong KongHong KongChina Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China

Strain localization processes in the continental crust generate faults and ductile shear zones over a broad range of scales affecting the long-term lithosphere deformation and the mechanical response of faults during the seismic *** anisotropy originated within the continental crust can be applied to deduce the kinematics and structures within orogens and is widely attributed to regionally aligned minerals,e.g.,***,naturally deformed rocks commonly show various structural layers(e.g.,strain localization layers).It is necessary to reveal how both varying amphibole contents and fabrics in the structural layers of strain localization impact seismic property and its interpretations in terms of *** present microstructures,petrofabrics,and calculate seismic properties of deformed amphibolite with the microstructures ranging from mylonite to *** transition from mylonite to ultramylonite is accompanied by a slight decrease of amphibole grain size,a disintegration of amphibole and plagioclase aggregates,and amphibole aspect ratio increase(from 1.68 to 2.23),concomitant with the precipitation of feldspar and/or quartz between amphibole *** intensities of amphibole crystallographic preferred orientations(CPOs)show a progressively increasing trend from mylonitic layers to homogeneous ultramylonitic layers,as indicated by the JAm index increasing from 1.9–4.0 for the mylonitic layers and 4.0–4.8 for the transition layer,to 5.1–6.9 for the ultramylonitic *** CPO patterns are nearly random for plagioclase and *** amphibole aggregates in the amphibolitic mylonite deform by diffusion,mechanical rotation,and weak dislocation creep,and develop CPOs *** polymineralic matrix(such as quartz and plagioclase)of the mylonite and the ultramylonite deform dominantly by dissolution-precipitation,combined with weak dislocation *** mean P and S wave velocities are estimated to be 6.3 and 3.5 km/

关键词： amphibolitic mylonite microstructures petrofabrics seismic property middle crust rheology tectonics.

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萨迦穹隆北侧苦堆淡色花岗岩的形成机制及对喜马拉雅造山带演化的约束

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岩石学报 2024年第5期40卷 1647-1668页

作者：王宏立范云松张进江古大祥林超王晓先北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室北京100871 紫金矿业集团股份有限公司厦门361000 应急管理部国家自然灾害防治研究院北京100085

萨迦穹隆位于北喜马拉雅片麻岩穹隆带中部。野外构造解析表明,萨迦穹隆北侧剖面可划分为由浅变质特提斯喜马拉雅沉积岩系构成上构造层,糜棱状石榴石片岩构成中构造层,糜棱状的正片麻岩和副片麻岩复合体构成下构造层(穹隆核部)。从上构... 详细信息

萨迦穹隆位于北喜马拉雅片麻岩穹隆带中部。野外构造解析表明,萨迦穹隆北侧剖面可划分为由浅变质特提斯喜马拉雅沉积岩系构成上构造层,糜棱状石榴石片岩构成中构造层,糜棱状的正片麻岩和副片麻岩复合体构成下构造层(穹隆核部)。从上构造层向中构造层变质变形程度连续增高,但没有明显的拆离断层分隔,中构造层与下构造层被拆离面分隔。不同构造层次都具有统一的近北倾的线理和面理,运动学特征都指示了上盘向北的伸展剪切,表明萨迦穹隆北侧剖面的剪切变形可能代表了藏南拆离系在北喜马拉雅穹隆的出露。苦堆白云母花岗岩和石榴石花岗岩以顺层(面理化)和切层形式侵位于下构造层片麻岩中,呈现明显的同构造变形特征。两类淡色花岗岩具有相似的全岩主量元素特征:高的SiO_(2)(73.26%~74.87%)、Al_(2)O_(3)(14.37%~15.03%)和CaO(1.51%~1.81%),A/CNK指数在1.08~1.16之间。白云母花岗岩表现出较高的Ba(398×10^(-6)~739×10^(-6))和Sr(135×10^(-6)~165×10^(-6)),低的Rb(180×10^(-6)~201×10^(-6))和Rb/Sr比(1.22~1.34),变化的Eu/Eu*(0.76~1.47),轻重稀土分异明显,球粒陨石标准化稀土元素配分图呈明显右倾趋势。石榴石花岗岩表现出低的Ba(204×10^(-6)~282×10^(-6))和Sr(81×10^(-6)~103×10^(-6)),较高的Rb(243×10^(-6)~281×10^(-6))和Rb/Sr比(2.37~3.22),明显的Eu负异常(Eu/Eu*=0.46~0.66),轻重稀土分异不明显,球粒陨石标准化稀土元素配分图呈“海鸥型”。苦堆淡色花岗岩的初始87 Sr/86 Sr比为0.762732~0.766668,ε_(Nd)(t)为-13.1~-12.5,与大喜马拉雅结晶岩系一致。年代学结果表明苦堆白云母花岗岩形成于约27Ma,石榴石花岗岩形成于27.5~28.1Ma。根据岩相学、年代学、运动学、地球化学等分析,认为苦堆白云母花岗岩起源于大喜马拉雅结晶岩系白云母水致熔融,源岩为大喜马拉雅较深位置的变杂砂岩,石榴石花岗岩是白云母花岗岩进一步结晶分异的结果。同构造的苦堆淡色花岗岩反映了渐新世早期藏南拆离系已经启动,藏南拆离系的启动诱发了地壳深部的白云母水致熔融,形成淡色花岗岩,并沿着藏南拆离系侵位。喜马拉雅造山带在渐新世(集中于28~26Ma)已从碰撞增厚转换为代表松弛与折返的伸展构造背景。

关键词：苦堆岩体淡色花岗岩藏南拆离系地球化学喜马拉雅造山带

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On the material invariant of 110°-conjugate angle of shear bands——Reply to Gomez-Rivas and Griera(2015)

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Science China Earth Sciences 2015年第12期58卷 2363-2368,1-3页

作者： ZHENG YaDong zhang jinjiang WANG Tao The Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of Education School of Earth and Space SciencesPeking University Institute of Geology Chinese Academy of Geological Sciences

After their experimental data were re-explained in terms of the maximum-effective-moment （MEM） criterion, Gomez-Rivas and Griera （2015） challenge the validity of the MEM-Criterion in terms of shear fractures, which have mixed up with shear fractures and shear bands. The two features are similar in appearance but different in deformation mechanism （s）. The MEM-criterion proves that ±55° to σ1era are the maximum effective moment directions and the shear bands that formed by mate- rial-line （beddings or fabrics） rotation mechanism have a constant conjugate angle of 110°. Theoretically, the 55° or 110° is a material-invariant, and practically, a statistic-invariant or preferred direction with average deviation of -10°. By this angle, shear bands can be easily recognized from shear fractures with conjugate angle never over 90°. The High-strain deformation in the lozenges usually predates the surrounding shear bands. Two stress states can not coexisted simultaneously in the same place and the resolving cr1＇ normal to the related shear zone represents 0-100% deformation partitioning, depending on the original kinematic vorticity of the shear zones.

关键词： kink-bands/shear bands deformation localization MEM-criterion deformation partitioning

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Using the Maximum Effective Moment Criterion to Interpret Quartz -Fabric Patterns

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Acta Geologica Sinica(English Edition) 2019年第4期93卷 799-809页

作者： ZHENG Yadong zhang jinjiang zhang Bo The Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China

The Maximum Effective Moment(MEM)criterion predicts that the initial orientation of ductile shear zones and shear bands is^55°relative to the maximum principal stress axis(σ1)and that the kinematic vorticity number(Wk)is^*** preferred orientations should be reflected in the pattern of quartz-fabrics in shear zones and shear *** quartz-fabrics in plane strain can be divided into low-temperature(L)and high-temperature(H)fabrics,with each group showing three patterns.A steady flow with a constant value of Wk≈0.94 gives rise to L-1 and H-1 patterns,which are commonly characterized by a singleaxis girdle normal to the shear zone and a single-point maximum parallel to the shear *** the conjugate set develops,L-1 and H-1 have opening angles of^70°and^110°,respectively.L-2 and H-2 are asymmetric patterns associated with variable deformation partitioning and vorticity values of0-fabrics is implicitly linked to the temperature during *** opening angle is^70°at low temperature and^110°at high ***,a linear correction between the opening angle and the temperature cannot be *** deformation partitioning,synthetic shear bands form earlier than antithetic bands and are more easily *** may result in opening angles of110°for high-temperature *** following criteria can be used to recognize reworked shear zones that have experienced multiple orogenic phases and changes in the stress state:1)the initial Wk is larger or smaller than^0.94;2)the change in Wk is abrupt,rather than progressive;3)inconsistent shear senses are inferred for the different phases of deformation;and4)a negative value of Wk is found in reworked shear zones.

关键词： deformation localization deformation partitioning shear bands vorticity Wk quartz CPO patterns

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Multistage Extension and Age Dating of the Xiaoqinling Metamorphic Core Complex,Central China

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Acta Geologica Sinica(English Edition) 1999年第2期73卷 139-147页

作者： zhang jinjiang ZHENG Yadong Institute of Geology Chinese Academy of Sciences P. O. Box 9825 Beijing 100029 Department of Geology Peking University Beijing 100871

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.

关键词： Xiaoqinling metamorphic core complex (XMCC) multistage extension detachment fault collapse ages

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Ductile deformation and its geological implications for retrograded eclogites from the Hongqiyingzi Complex in Chicheng,northern Hebei,China

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Science China Earth Sciences 2016年第8期59卷 1610-1621页

作者： LIU ShiRan zhang jinjiang QI GuoWei WANG Meng Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of EducationSchool of Earth and Space SciencesPeking UniversityBeijing 100871China Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits Ministry of Land and ResourcesSchool of Earth Science and ResourcesChang'an UniversityXi'an 710054China

The rheology of rocks at depth remains a key point in earth sciences. Deformation of high-temperature–highpressure rocks from the subduction zone has not been fully studied; in particular, the deformation behavior of eclogites remains poorly understood. This research is focused on the microstructure and fabric of retrograded eclogites from the Hongqiyingzi Complex in Chicheng, north Hebei, China, based on photomicrography, scanning electron microscopy(SEM) and electron backscattered diffraction(EBSD) analysis. The analytical results show that plastic deformation occurred in the garnets during exhumation, but they do not show an obvious lattice preferred orientation(LPO). This can be interpreted as being caused by the simultaneous activation of multiple slip systems in the garnets during deformation by dislocation creep. The plagioclases have a special fabric; the(001) LPO presents a maximum in Z direction which can be correlated with a new [100](001) slip system. The misorientation angle distribution(MAD) of the plagioclases in the deformed retrograded garnet augens shows a special bimodal distribution with peaks in both a low-angle range(140?). In the retrograded garnet augens(i.e. "white eye socket" garnets) the maximum peak moves from a high-angle range to a low-angle range when we analyze only those plagioclases surrounding the residual garnet porphyroclast. Deformation behavior is controlled by the crystallographic orientation of the host grain and the grain boundary sliding process. Hornblendes in different layers and the retrograded garnet augens show almost the same strong LPO patterns, which are correlated with the [001](010) slip system; and MAD diagrams show a peak in a low-angle range(<40?). Integrating recent studies on metamorphism and geochronology, we argue that ductile deformation occurred during the exhumation periods together with retrograded metamorphism.

关键词： Fabric Microstructure Retrograded eclogites Electron backscatter diffraction(EBSD) Hongqiyingzi Complex North China

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SEM/EBSD analysis of quartz cementation and compaction microstructures during diagenesis of sandstone

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Science China Earth Sciences 2013年第8期56卷 1281-1293页

作者： zhang Bo YAN ShuYu GU ZhiDong zhang jinjiang The Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking University SINOPEC Exploration & Production Research Institute

Compaction and silicon cementation are the dominant processes reducing porosity and permeability in quartzose sandstones during diagenesis. Despite the wealth of information about quartz cementation, there are still unanswered questions related to mechanisms of growth of quartz cement and the diagenesis processes. In this study we present an electron backscatter diffraction （EBSD） analysis, combined with optics and cathodoluminescence （CL） information, for the quartz sandstones from the Upper Triassic Xujiahe Formation of Sichuan Basin, in order to reveal the microstructural and crystallographic features of the silica cementation and detrital grain during the compaction. The EBSD is a crucial technique to provide essential crystallographic data on the quartz grain and its cement. Quartz cement is shown to be syntaxial to its host quartz grain. EBSD data-based orientation maps show dauphin6 twinning and low angle boundary to be common in the host grains and quartz cement of the samples. The dauphin6 twins occurred in grain-grain contacts and in cement-crystal boundaries, and commonly crossed grain cement boundaries. These features indicate that there may be two types of dauphin6 twins, one inherited twins from the source area and the other developed by compaction-induced grain boundary deformation. These investigations suggest that strong mechanical compaction may occur after and/or during quartz cement growth in the later diagenesis of the Xujiahe sandstones. EBSD has a capability of revealing microstructural information and regarding mechanisms of diagenesis crystal growth in quartzose sandstones.

关键词： sandstone quartz cement compaction dauphin~ twins low angle boundary electron backscatter diffraction

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Strain and kinematic vorticity analysis:An indicator for sinistral transpressional strain-partitioning along the Lancangjiang shear zone,western Yunnan,China

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Science China Earth Sciences 2009年第5期52卷 602-618页

作者： Bo zhang jinjiang zhang DaLai Zhong Lei Guo State Key Laboratory Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China The Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of Education Peking University Beijing 10

This work deals with the preliminary relationship between strain path and strain partitioning pattern in a sinistral transpressional zone, Lancangjiang shear zone, located to the southeast of Tibet. Various ductile ro... 详细信息

关键词： strain kinematic vorticity transpression strain partitioning Lancangjiang shear zone

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Northward subduction-related orogenesis of the southern Altaids:Constraints from structural and metamorphic analysis of the HP/UHP accretionary complex in Chinese southwestern Tianshan,NW China

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Geoscience Frontiers 2015年第2期6卷 191-209页

作者： Mark Scheltens Lifei zhang Wenjiao Xiao jinjiang zhang School of Earth and Space Sciences Peking University State Key Laboratory of Lithosphere Evolution Institute of Geology and Geophysics Chinese Academy of Sciences

The Chinese Tianshan belt of the southern Altaids has undergone a complicated geological evolution. Different theories have been proposed to explain its evolution and these are still hotly debated. The major subduction polarity and the way of accretion are the main problems. Southward, northward subduction and multiple subduction models have been proposed. This study focuses on the structural geology of two of the main faults in the region, the South Tianshan Fault and the Nikolaev Line. The dip direction in the Muzhaerte valley is southward and lineations all point towards the NW. Two shear sense motions have been observed within both of these fault zones, a sinistral one, and a dextral one, the latter with an age of 236-251 Ma. Structural analyses on the fault zones show that subduction has been northward rather than southward. The two shear sense directions indicate that the Yili block was first dragged along towards the east due to the cloclkwise rotation of the Tarim block. After the Tarim block stopped rotating, the Yili block still kept going eastward, inducing the dextral shear senses within the fault zones.

关键词： Structural geology Tianshan Subduction polarity HP/UHP belt

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Rapid denudation of the Himalayan orogen in the Nyalam area,southern Tibet, since the Pliocene and implications for tectonics–climate coupling

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Chinese Science Bulletin 2014年第11期59卷 874-885页

作者： Yong Zheng jinjiang zhang Jiamin Wang Bo zhang Xiaoxian Wang Meng Wang Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space Sciences Peking University

The Himalayan orogen characterized by very high variability in tectonic and climatic processes,and is thus regarded as a natural laboratory for investigating the coupling of tectonics and climate,as well as the influence of this coupling on geomorphological *** study uses apatite fission track(AFT)dating of samples from a45-km-long section crossing the Great Himalaya Crystalline Complex(GHC)in the Nyalam area,southern Tibet,to constrain the timing and rate of late Cenozoic *** AFT ages can be divided into two groups:(1)15–6 Ma,to the north of Nyalam town,for which the bestfit line of elevation-age has a gentle slope of 0.05,and for which a denudation rate of 0.27 mm/a is calculated;and(2)3–1 Ma,south of Nyalam town,for which the best-fit line has a steep slope of 0.64,and for which a denudation rate of 1.32 mm/a is *** whole AFT ages has a positive correlation with sample elevation(i.e.,older ages are found at higher elevations),and the geographical location of the point of inflexion of the two fitted lines corresponds closely to the junction of Poqu River near Nyalam *** integrating the AFT data with thermotectonic modeling,it can be inferred that the GHC has experienced two different periods of denudation:(1)slow denudation during middle to late Miocene(15–6 Ma)is recorded in the northern part of the GHC;and(2)rapid denudation from the Pliocene to the Pleistocene(3–1 Ma)is recorded in the southern part of the *** abrupt change in denudation rate occurred between the two periods,with the Pliocene–Pleistocene denudation rate being five times higher than that during the *** abrupt change in denudation rate during Pliocene pervaded the Himalayan orogen,and was roughly synchronous with a marked change in global climate at 4–3 Ma,and intensification of the Asian ***,the later period of rapid denudation in the study region closely coupled to the mean annual precipitation,while there is no clear evidence for

关键词：喜马拉雅造山带聂拉木地区剥蚀速率全球气候构造模型西藏南部上新世耦合

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