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Structures,kinematics,thermochronology and tectonic evolution of the Ramba gneiss dome in the northern Himalaya

Progress in Natural Science:Materials International 2008年第7期18卷 851-860页

作者： lei guo,jinjiang zhang,bo zhang the key laboratory of orogenic belts and crustal evolution,{3. of Education,china school of earth and space sciences,peking university,beijing 100871,china The key laboratory of orogenic {3. and crustal evolution Ministry of Education China school of earth and space {3. Peking University Beijing 100871 China

The Ramba gneiss dome,one of the north Himalayan gneiss domes,is composed of three tectono-lithologic units separated by an upper and a lower detachment ***-grade metamorphic Tethyan Himalayan sedimentary sequence formed the upper unit above the brittle upper detachment *** gneiss and a leucogranite pluton made up the lower unit beneath the ductile lower detach- ment *** middle-grade garnet-,staurolite-and andalusite-schist constituted the middle unit between the two faults,which may be that the basal part of the upper unit experienced detachment *** Ramba dome underwent three episodes of deformation in its tectonic *** first episode was a top-down-to-north-northwest sliding possibly related to the activity of the south Tibetan detachment system(STDS).The second episode was the dominant deformation related to a east–west extension,which resulted in a unique top-down-to-east kinematics and the major tectonic features of the *** third episode was a collapse sliding toward the outsides of the *** Ramba gneiss dome is possibly a result of the east–west extension and magmatic *** lower detachment fault is probably the main detachment fault separating the sedimentary sequence from the crystalline basement during the east–west extension in the dominant deformation *** diapir of the leucogranite pluton formed the doming shape of the Ramba gneiss *** pluton intruded in the core of the dome in a late stage of the dominant deformation,and its Ar–Ar cooling ages are about 6 *** indicates that the dominant deformation of the dome happened at the same time of the east–west extension represented by the north–south trending rifts throughout the northern Himalaya and southern ***,the formation of the Ramba gneiss dome should be related to this east–west extension.

关键词： Ramba gneiss dome North Himalayan gneiss domes East–west extension

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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 {3. 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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Mesozoic thrusts and extensional structures in the Daqingshan orogen, Inner Mongolia, and their temporal and spatial relationship

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Progress in Natural Science:Materials International 2007年第2期17卷 177-186页

作者： QI guowei, zhang jinjiang , WANG Xinshe and guo lei ( key laboratory of orogenic belts and crustal evolution, ministry of Education, china {13. of earth and space sciences, peking university, beijing 100871, china Institute of Geology, Chinese Academy of Geological sciences, beijing 10003., china) [a]key laboratory of orogenic {3. and crustal evolution Ministry of Education China [b]school of earth and space {3. Peking University Beijing China [c]Chinese Academy of Geological sciences Institute of Geology Beijing China

Three large-scale thrusts developed in the Daqingshan orogen, Inner Mongolia, with a northeast-east trending from Louhuashan to Suletu are described in this paper. These northwest-directed thrusts, together with the four tectonic belts (or tectonic sheets) separated by these faults, formed a typical thrusting system. The originally defined Hohhot metamorphic core complex may be a tectonic sheet, making the uppermost tectonic unit of the thrusting system and truncated by the Daqingshan detachment fault on top. The existing tectono-chronological studies showed that the thrusting of this region possibly happened at the same time as the extension along the top detachment fault. This presents that the contraction and extension in Daqingshan orogen were probably simultaneous. The structural pattern of the Daqingshan orogen can be correlated to the Himalayan orogen, and models for simultaneous thrusting and detachment in Himalaya may give a hint for explaining the development of the Daqingshan orogen.

关键词： Daqingshan thrust metamorphic core complex detachment fault contraction-extension transform Himalaya.

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Microstructures,Deformation Mechanisms and Seismic Properties of Synkinematic Migmatite from Southeastern Tibet:Insights from the Migmatitic Core of the Ailao Shan-Red River Shear Zone,Western Yunnan,china

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Journal of earth Science 2024年第4期35卷 1149-1169页

作者： Weiwei Ma bo zhang Fulong Cai Baoyou Huang lei zhang key laboratory of orogenic {3. and crustal evolution School of Earth and Space SciencesPeking UniversityBeijing100871China Institute of Tibetan Plateau Research Chinese Academy of SciencesBeijing100085China

Seismic anisotropy originating within the continental crust is commonly used to determine the deformation and kinematic flow within active orogens and is attributed to regionally oriented mica or hornblende ***,naturally deformed rocks usually contain compositional layers(e.g.,parallel compositional banding).It is necessary to understand how both varying mineral contents and differing intensities of compositional layering influence the seismic properties of the deep *** this study,we analyzed the seismic response of migmatitic amphibolite with compositional banding *** present the microstructures,fabrics,calculated seismic velocities,and seismic anisotropies of mylonitic amphibolite from a horizontal shear layer preserved within the Ailao Shan-Red River shear zone,southwestern Yunnan,*** investigated sample is characterized by pronounced centimeter-scale compositional *** microstructures and fabrics suggest that migmatitic amphibolite rocks within deep crust may delineate regions of deformation-assisted,channelized,reactive,porous melt *** origin of compositional banding in the studied migmatitic amphibolite is attributed primarily to partial melting together with some horizontal shearing *** microfabrics and structures investigated in this study are considered to be typical for the base of active horizontal shear layers in the deep crust of southeastern *** responses are modeled by using crystal preferred orientations for minerals of the migmatitic amphibolite by applying the Voigt-Reuss-Hill homogenization *** P-wave and S-wave velocities are largely consistent in the various layers of the ***,seismic anisotropies of P-wave(AV_(p))and S-wave(AVs)are higher in the melanosomes(AV_(p)=5.6%,AV_(s)=6.83.)than those in the leucosomes and the whole rock(AV_(p)=4.2%–4.6%,AV_(s)=3.1%–3.2%).In addition,there is pronounced,S-wave splitting oblique to the foliation plane in the migm

关键词： deformation-assisted melt flow seismic anisotropy microstructure compositional banding migmatite deep crust southeastern Tibet

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内蒙古大青山-盘羊山晚中生代-早新生代构造事件及其对华北北缘构造演化的启示

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地学前缘 2024年第1期31卷 127-141页

作者：张进江郑剑磊王海滨郭磊刘江戚国伟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 中国地质科学院地质研究所北京100037 中国地质调查局西安地质调查中心陕西西安710119 北京大学深圳研究生院广东深圳518055

内蒙古大青山和盘羊山位于华北克拉通北缘,其复杂的地质构造对华北克拉通北部中—新生代构造演化具有重要的指示作用。大青山以北的盘羊山逆冲体系,形成于晚二叠世至早三叠世古亚洲洋的闭合,晚侏罗世可能受蒙古-鄂霍次克洋闭合的影响而... 详细信息

内蒙古大青山和盘羊山位于华北克拉通北缘,其复杂的地质构造对华北克拉通北部中—新生代构造演化具有重要的指示作用。大青山以北的盘羊山逆冲体系,形成于晚二叠世至早三叠世古亚洲洋的闭合,晚侏罗世可能受蒙古-鄂霍次克洋闭合的影响而重新活动。大青山地区发育4期中—新生代变形构造,从老至新依次是:SE-NW向伸展形成的呼和浩特变质核杂岩、NW向逆冲的大青山逆冲体系、以不变形花岗岩为核心的构造穹窿、大青山山前断裂及高角度正断层。发生于约142~13. Ma的SE-NW向伸展,形成于造山增厚地壳的重力垮塌,并形成呼和浩特变质核杂岩和相关的拆离体系。大青山逆冲体系形成于约13.~120 Ma,代表造山过程中地壳荷载与板块汇聚的抗衡导致的构造反转,另一可能是古太平洋俯冲的远程效应。自约120 Ma以来,大青山处于一个构造-热松弛期,导致该区约120~90 Ma的冷却事件被广泛记录,并形成以不变形花岗岩(约114 Ma)为核心的穹窿构造;这些事件可能与华北克拉通的峰期破坏相关。大青山山前断裂和相关的高角度正断层开始于始新世,可能是印度-欧亚大陆碰撞和太平洋板块运动方向改变的远程效应所致。古亚洲洋和蒙古-鄂霍次克洋的闭合导致华北克拉通北缘地壳增厚,引发早白垩世造山晚期的垮塌和伸展,形成呼和浩特变质核杂岩。自120 Ma开始,大青山开始受华北克拉通破坏的影响,并形成后造山伸展。新生代,大青山受新特提斯和太平洋构造域的远程影响。

关键词：中生代新生代逆冲变质核杂岩(MCC) 构造转换大青山华北克拉通北缘

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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 {3. State key laboratory Lithospheric evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China The key laboratory of orogenic {3. 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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Structural feature and its significance of the northernmost segment of the Tertiary Biluoxueshan-Chongshan shear zone,east of the Eastern Himalayan Syntaxis

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Science china earth sciences 2011年第7期54卷 959-974页

作者： zhang bo zhang {3. ZHONG DaLai WANG XiaoXian QU JunFeng guo lei key laboratory of orogenic Belt and {3. evolution Ministry of Education School of Earth and Space Sciences Peking University Beijing 100871 China State key laboratory of Geological Processes and Mineral Resources China University ofGeosciences Beijing 100083 China Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China

Here we describe ductile, ductile-brittle and brittle deformation styles in the northern segment of the Tertiary Biluoxue- shan-Chongshan shear zone lying to the east of the Eastern Himalayan Syntaxis. In the northernmost part of the zone in the vi- cinity of the Eastern Himalayan Syntaxis, it consists of mylonitic gneiss, granite, and schist. Based on field relations and min- eral assemblages, the rocks are classified into gneiss belt in the west limb, including banded gneiss, augen mylonite and mig- matite gneiss, and schist belt in the east limb. Except for the massive granite pluton, the other three tectonites are affected by polystage deformation （D1-D4）. Fold deformation of the first stage D1 is isoclinal to tight pattern with nearly N-S fold axes and steeply axial planar cleavage S 1, which resulted in the local crustal thickening under a contractive setting. D2 overprinted D1 and is characterized by tight folds with steep axes and N-S fold axial planar, which are also characterized by large-scale ductile strike-slip shear foliation $2, parallel to the nearly N-S trending axial planes of D1 and D2. The structural pattern of D2 represents a transpression along the zone. D3.occurred during the late stage of the transpression or post-transpression, produc- ing the NW-SE and NE-SW trending strike-slip faults of the third stage D3. Following the D3.deformation, the zone was ex- humed to shallow crustal level where the various tectonites underwent a brittle transtensional deformation D4, combined with one N-S trending strike-slip component and one normal faulting component. Structures and previous geochronologies pre- sented in the paper suggest that the study area is correlated with those in the adjacent tectonic zones, Ailaoshan-Red River shear zone and Gaoligong shear zone in the western Yunnan. It underwent intensive polyphase deformation, namely, crustal thickening, transpression, and transtension, responding to syn-collision and post-collision of India-Eurasi

关键词： Biluoxueshan-Chongshan shear zone Tertiary structure polystage deformation

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Structural features and deformational ages of the northern Dabashan thrust belt

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Geoscience Frontiers 2012年第1期3卷 41-49页

作者： Pengyuan Li jinjiang zhang lei guo Xiongying Yang The key laboratory of orogenic {3. and crustal evolution Peking UniversityBeijing 100871China Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China

A large-scale pop-up structure occurs at the front of the northern Dabashan thrust belt （NDTB）, bound by the NNE-dipping Chengkou fault to the south, and the SSW-dipping Gaoqiao fault to the north. The pop-up structure shows different features along its strike as a direct reflection of the intensity of tectonic＂ activity. To the northwest, the structure is characterized by a two-directional thrust system forming a positive flower-like structure. In contrast, the southeastern part is composed of the vertical Chengkou fault and a series of N-directed backthrusts, showing a semi-flower-like structure. We present results from Ar-Ar dating of syntectonic microthermal metamorphic sericite which show that the Chengkou fault experienced intense deformation during the mid-Mesozoic Yanshanian epoch （about 143.3.Ma）, causing rapid uplift and thrusting of the northern Dabashan thrust belt. During the propagation of this thrust, a series of backthrusts formed because of the obstruction from the frontier of Dabashan thrust belt, leading to the development of the pop-up structure.

关键词： Northern Dabashan Thrust belt Backthrust Tectonics Pop-up structure Ar-Ar geochronology

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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 {3. The key laboratory of orogenic {3. 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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New indicators from bedding-parallel beef veins for the fault valve mechanism

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Science china earth sciences 2015年第8期58卷 1320-1336页

作者： zhang bo YIN CongYuan GU ZhiDong zhang {3. YAN ShuYu WANG Yang The key laboratory of orogenic {3. and crustal evolution School of Earth and Space SciencesPeking University Exploration & Production Research Institute SINOPEC

Beef structures(bedding-parallel veins of fibrous calcite)are widespread within the Lower Triassic carbonate rocks in the Sichuan Basin of china,especially within clay-rich strata of low *** the veins,fibrous calcite occurs in the outer zones,and coarse equant calcite in the inner *** least two generations of calcite crystallization took place during aqueous alteration,at the same time as deformation recorded by the *** first-generation calcite fibers are at steep angles to the hydrocarbon-bearing host beds,and they grew vertically against the force of gravity at a time when the source rocks were ***-generation calcite occurs as coarse equant grains that sealed pores via localized fluid flow during horizontal tectonic compression,so that shear stresses acted at the fracture *** of the host rock was accommodated in part by dissolution-precipitation creep(DPC),grain rotation,and grain slippage,recorded in crystallographic preferred orientations(CPOs)of the host calcite grains beside the crack *** beef veins formed during high pore-fluid overpressures along *** propose that the bedding-parallel veins with beef structures are evidence of a"crack-seal slip"fault valve process during hydrocarbon *** hydrocarbon-bearing calcite beef structure may be a good indicator of oil or gas migration,and of the flow direction of aqueous solutions.

关键词： calcite vein beef structure crack-seal slip EBSD carbonate rock Sichuan Basin

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