共查询到19条相似文献,搜索用时 125 毫秒
1.
The Hatugou-Qingshuiquan-Gouli ductile shear zone recorded multiple cycles of orogeny in the eastern section of East Kunlun. The quartz c-axis fabric and microstructure of samples from the ductile shear zone were analyzed. We discussed the formation mechanism of subducted and crust extension-thinning of continental blocks in the eastern section of East Kunlun. Analysis results show that the deformation temperature of the ductile shear zone was between 380℃ and 650℃, which can be analogue with metamorphisms of middle-high greenschist facies to lower amphibolite facies. The differential stress and strain rate of the ductile shear zone are estimated at 173-509 MPa, 6.93×10-14-1.43×10-8 s-1, respectively, which suggest a possible origin of rapid subduction. Moreover, the deformation temperature, differential stress and strain increase toward the middle of East Kunlun fault zone, which is consistent with the fact that the middle part of the East Kunlun experienced the most intensive ductile shear deformation. The calculations of the kinematic vorticity values of the ductile shear belt show that the early transient kinematic vorticity (0.56-1.00) of ductile shear zone corresponds to the initial stage of the northward subducted southern parts of East Kunlun. In the middle to later stage, the kinematic vorticity (0.25-0.91) should correspond to the collision between southern and northern parts of East Kunlun. The latest C' instantaneous kinematic vorticity (0.19-0.51) corresponds to extensional stage in the post-orogenic setting. The quartz c-axis fabric and the structural characteristics show that the middle part of East Kunlun tectonic belt experienced at least 3 stages of tectonic movements, including the late Caledonian thrusting and left lateral strike slip shearing, the late Hercynian Indosinian thrusting and dextral strike slip shearing and the brittle ductile brittle-left lateral strike slip shearing in the early and later Yanshanian. ©, 2015, Science Press. All right reserved. 相似文献
2.
Huan-zhang LU Guy Archambault LI Yuansheng WEI Jiaxue 《中国地球化学学报》2007,26(3):215-234
The Linglong-Jiaojia district is one of the most important regions containing gold deposits in China. These gold deposits can be divided into: a) the pyrite-gold-quartz vein type (Linglong type), which is controlled by brittle-ductile to ductile deformation structures, and b) the alteration-zone type (Jiaojia type), characterized by small veinlets, or the disseminated type recognized in brittle shear zones. Lode gold deposits in the Jiaojia area occur in NE brittle fracture zones, formed in a dominantly simple shear deformation regime, mainly in thrust attitude with a minor sinistral strike slip component. In the Linglong area, the lode gold deposits are located at the intersection of three types of structures: NNE and NE brittle-ductile fault zones and the ENE ductile reverse shear zone in the south of the area. The structural characteristics of these brittle shear zones are consistent with a tectonic NNW-SSE principal stress field orientation. Similar stresses explain the ENE Qixia fold axes, the Potouqing and several other ENE reverse ductile shear zones elsewhere in the region, the Tancheng-Lujiang fault zone and its subsidiaries in the vicinity of the Linglong-Jiaojia district, as well as the southern ENE suture zone north of Qingdao. Therefore these structural systems occurred as part of different major tectonic events under NNW-SSE compression principal stress fields in the area. Gold deposits are hosted in smaller-scale structures within the brittle fault zones and brittle-ductile shear zones. Although ore bodies and, on a smaller scale, quartz ore veins often seem to be randomly oriented, it is possible to explain their distribution and orientation in terms of the simple shear deformation process under which they were developed. The progressive simple shear failure is characterized by various fracture modes (tension and shear) that intervene in sequence. The tension and shear fractures are influenced by the stress level (depth of burial beneath the paleosurface) in their structural behavior, show variable dilatancy (void openings) and extend on all scales. By making use of these characteristics, a progressive failure analysis can be applied to predicting the shape and extent of ore bodies as well as the styles of mineralization at any given location. 相似文献
3.
Structural and Chronological Evidence for the India-Eurasia Collision of the Early Paleocene in the Eastern Himalayan Syntaxis, Namjagbarwa 总被引:3,自引:0,他引:3
ZHANG Jinjiang JI Jianqing Department of Geology Peking University Beijing ZHONG Dalai SANG Haiqing HE Shundong Institute of Geology Geophysics Chinese Academy of Sciences Beijing 《《地质学报》英文版》2002,76(4):446-454
The eastern Himalayan syntaxis in Namjagbarwa is a high-grade metamorphic terrain formed by the India-Eurasia collision and northward indentation of the Indian continent into Asia. Right- and left-lateral slip zones were formed by the indentation on the eastern and western boundaries of the syntaxis respectively. The Dongjug-Mainling fault zone is the main shear zone on the western boundary. This fault zone is a left-lateral slip belt with a large component of thrusting. The kinematics of the fault is consistent with the shortening within the syntaxis, and the slipping history along it represents the indenting process of the syntaxis. The Ar-Ar chronological study shows that the age of the early deformation in the Dongjug-Mainling fault zone ranges from 62 to 59 Ma. This evidences that the India-Eurasia collision occurred in the early Paleocene in the eastern Himalayan syntaxis. 相似文献
4.
FENG Yipeng WANG Genhou WANG Shulai LI Dian WANG Huan LU Yang LIU Han ZHANG Peilie 《《地质学报》英文版》2024,98(1):32-49
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 (?) 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. 相似文献
5.
Thermal Evolution of the Tanlu Fault Zone on the Eastern Margin of the Dabie Mountains and Its Tectonic Implications 总被引:7,自引:3,他引:4
ZHU Guang HOU Minjin WANG Yongsheng LIU Guosheng NIU Manlan School of Resource Environment Engineering Hefei University of Technology Hefei Anhui Geological Survey of Anhui Hefei Anhui 《《地质学报》英文版》2004,78(4):940-953
Five samples of muscovite from mylonites of the earlier Tanlu ductile shear zone on the eastern margin of the Dabie Mountains yield 40Ar/39Ar ages ranging from 178 Ma to 196 Ma. Three of them have reliable plateau ages of 188.7±0.7 Ma, 189.7±0.6 Ma and 192.5±0.7 Ma respectively, which indicates a syn-orogenic, sinistral strike-slip thermal event. This displacement movement derived from the continent-continent collision of the North and South China blocks took place in the Early Jurassic and after uplifting of high-pressure to ultrahigh-pressure slabs to the mid-crust. It is suggested that during the collision the Tanlu fault zone was an intracontinental transform fault caused by differential subduction speeds. The 40Ar/39Ar ages of mylonite whole-rock and muscovite from the later Tanlu ductile shear zone suggest another sinistral strike-slip cooling event at 128 Ma. During this strike-slip faulting, large-scale intrusion and doming uplift occurred in the eastern part of the Dabie orogenic belt. Data o 相似文献
6.
The Wahongshan fault zone in Qinghai province is one of the most important faults in westem China. In this paper, deformation and X-ray petrofabrics have been studied in the middle segment of the fault. The results show that the formation of the fault zones can be divided into two major stages: ductile shear deformation stage and brittle deformation stage. The early stage ductile shearing leads to the formation of the NW-NNW trending mylonite zones along the fault, which is intensely cut by the late-formed brittle faults. X-ray petrofabrics of rocks near the faults indicate that the minerals in the tectonites show a great degree of orientation in the alignment. The quartz, which is a very important mineral in the tectonites, is deformed by basal face gliding or near basal face gliding, and sometimes by prismatic face sliding, which indicates that the rocks are deformed in epithermal to mesothermal or mesothermal environment, and the dynamic recrystallization also plays an important role in the formation 相似文献
7.
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 con- trol the shape, attitude, scale, and distribution of mineralization zones and ore-bodies. (3) Com- presso-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 ma- terials 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 nega- tive correlation between the gold abundance and susceptibility anisotropy (P) of the altered mylonite 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. 相似文献
8.
By a detailed investigation of geometry and kinematics of the Shangma (商麻) fault in Dabieshan (大别山),three different crust levels of extension movement have been recognized in sequence from the deep to the shallow:① low-angle ductile detachment shearing with top to the NW; ② low-angle normal fault with top to the NW or NWW in brittle or brittle-ductile transition domain; ③high-angle brittle normal fault with top to the W or NWW. Two samples were chosen for zircon U-Pb age dating to constrain the activity age of the Shangma fault. A bedding intrusive granitoid pegmatite vein that is parallel to the foliation of the low-angle ductile detachment shear zone of the country rock exhibits a lotus-joint type of boudinage deformation,showing syn-tectonic emplacing at the end of the ductile deformation period and deformation in the brittle-ductile transition domain. The zircon U-Pb dating of this granitoid pegmatite vein gives an age of (125.9±4.2) Ma,which expresses the extension in the brittle-ductile transition domain of the Shangma fault. The other sample,which is collected from a granite pluton cutting the foliation of the low-angle ductile detachment shear zone, gives a zircon U-Pb age of (118.8±4.1) Ma,constraining the end of the ductile detachment shearing. Then the transformation age from ductile to brittle deformation can be constrained between 126-119 Ma.Combined with the previous researches,the formation of the Luotian (罗田) dome,which is located to the east of the Shangma fault,can beconstrained during 150-126 Ma. This study gives a new time constraint to the evolution of the Dabie orogenic belt. 相似文献
9.
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相似文献
10.
Transpressional deformation has played an important role in the late Neoproterozoic evolution of the ArabianNubian Shield including the Central Eastern Desert of Egypt. The Ghadir Shear Belt is a 35 km-long, NW-oriented brittleductile shear zone that underwent overall sinistral transpression during the Late Neoproterozoic. Within this shear belt, strain is highly partitioned into shortening, oblique, extensional and strike-slip structures at multiple scales. Moreover, strain partitioning is heterogeneous along-strike giving rise to three distinct structural domains. In the East Ghadir and Ambaut shear belts, the strain is pure-shear dominated whereas the narrow sectors parallel to the shear walls in the West Ghadir Shear Zone are simple-shear dominated. These domains are comparable to splay-dominated and thrust-dominated strike-slip shear zones. The kinematic transition along the Ghadir shear belt is consistent with separate strike-slip and thrustsense shear zones. The earlier fabric(S1), is locally recognized in low strain areas and SW-ward thrusts. S2 is associated with a shallowly plunging stretching lineation(L2), and defines ~NW-SE major upright macroscopic folds in the East Ghadir shear belt. F2 folds are superimposed by ~NNW–SSE tight-minor and major F3 folds that are kinematically compatible with sinistral transpressional deformation along the West Ghadir Shear Zone and may represent strain partitioning during deformation. F2 and F3 folds are superimposed by ENE–WSW gentle F4 folds in the Ambaut shear belt. The sub-parallelism of F3 and F4 fold axes with the shear zones may have resulted from strain partitioning associated with simple shear deformation along narrow mylonite zones and pure shear-dominant deformation in fold zones. Dextral ENEstriking shear zones were subsequently active at ca. 595 Ma, coeval with sinistral shearing along NW-to NNW-striking shear zones. The occurrence of upright folds and folds with vertical axes suggests that transpression plays a significant role in the tectonic evolution of the Ghadir shear belt. Oblique convergence may have been provoked by the buckling of the Hafafit gneiss-cored domes and relative rotations between its segments. Upright folds, fold with vertical axes and sinistral strike-slip shear zones developed in response to strain partitioning. The West Ghadir Shear Zone contains thrusts and strikeslip shear zones that resulted from lateral escape tectonics associated with lateral imbrication and transpression in response to oblique squeezing of the Arabian-Nubian Shield during agglutination of East and West Gondwana. 相似文献
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In eastern China, the Dabie Shan–Su–Lu orogenic belt has been separated by the Tan–Lu sinistral strike–slip fault. Mylonites are exposed along the strike–slip fault system in the southern segment, and along the eastern margin of the Dabie Shan orogenic belt. The country rocks of the mylonites are retrograde UHP eclogites, gneissic granites, muscovite granites and gneisses. The ductile strike–slip shear zone trends 30–40°N (NE30–40°‐trending) and exhibits stretching lineations and nearly vertical, SE‐dipping foliations. Most of the zircon grains separated from mylonites have a weighted average radiometric age of 233 ± 6–225 ± 6 Myr. These data constrain the onset of the Tan–Lu sinistral strike–slip movement and imply that the Tan–Lu sinistral strike–slip motion developed after retrograde UHP metamorphism. The related phengite within the eclogite rocks on the western side of the Tan–Lu fault, with 40Ar/39Ar plateau ages of c. 182–190 Myr, is also deformed and aligned parallel to the almost NE trending stretching lineations. Non‐metamorphosed granites exhibit sinistral strike–slip shearing and indicate that the Tan–Lu fault initially developed after 182–190 Myr. Muscovite collected from the mylonite yields 40Ar/39Ar plateau ages of 162 ± 1–156 ± 2 Myr. The zircon SHRIMP age data, the muscovite 40Ar/39Ar plateau ages, together with structural and petrological field information support the interpretation that the Tan–Lu strike–slip fault was not related to the Yangtze–north China plates collision, but corresponded to the formation of a NE‐trending tectonic framework in eastern China starting c. 165–160 Ma. 相似文献
13.
~(40)Ar-~(39)Ar Dating of Albite and Phlogopite from Porphyry Iron Deposits in the Ningwu Basin in East-Central China and Its Significance 总被引:2,自引:1,他引:1
YU Jinjie MAO Jingwen Institute of Mineral Resources Chinese Academy of Geological Sciences Beijing 《《地质学报》英文版》2004,78(2):435-442
40Ar-39Ar dating of albite from the Meishan and Taocun iron deposits yields plateau ages of 122.90±0.16 Ma and 124.89±0.30 Ma, and isochron ages of 122.60±0.16 Ma and 124.90±0.29 Ma, respectively. Phlogopite from the Zhongshan-Gushan ore field has a plateau age of 126.7±0.17 Ma and an isochron age of 127.21±1.63 Ma. Analysis of regional geodynamic evolution of the middle-lower Yangtze River region suggests that the porphyry iron deposits were formed as a result of large-scale lithosphere delamination and strong sinistral strike-slip movement of the Tancheng Lujiang fault zone. The copper, molybdenum and gold deposit system in the middle-lower Yangtze River region was formed during the stress transition period of the eastern China continent. 相似文献
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A Large Ductile Sinistral Strike-Slip Shear Zone and Its Movement Timing in the South Qilian Mountains, Western China 总被引:6,自引:1,他引:5
XU Zhiqin LI Haibing CHEN Wen WU Cailai YANG Jingsui JIN Xiaochi CHEN Fangyuan Institute of Geology Chinese Academy of Geological Sciences Beijing Xie Guanglian 《《地质学报》英文版》2002,76(2):183-193
There is a large ductile shear zone, 2 km wide and more than 3SO km long, in the South Qilian Mountains, western China. It is composed of volcanic, granitic and calcareous mylonites. The microstructures of the ductile shear zone show nearly E-W extending subvertical foliation, horizontal and oblique stretching lineations, shearing sense from sinis-tral to oblique sinistral strike-slip from east to west, "A" type folds and abundant granitic veins. Measured lattice preferred orientations (LPOs) of the mylonitic and recrystallized quartz of the granitic mylonite in the west segment suggest a strong LPO characterized by the dominant slip systems {1010} formed at high temperature (>650℃). K-feldspar of the mylonite shows an 39Ar/40Ar high-temperature plateau age of 243.3±1.3 Ma, and biotite, 250.5±0.5 Ma, which represent the formation age of the ductile shear zone. The 39Ar/40Ar plateau ages of 169.7±0.3 Ma and 160.6±0.1 Ma and the 39Ar/40Ar isochron ages of 166.99±2.37 Ma and 160.6±0.1 Ma of biot 相似文献
16.
郯庐断裂带的延伸与切割深度 总被引:24,自引:0,他引:24
摘要:采用地质 地球化学 地球物理相结合的方法,系统研究了中生代以来郯庐断裂带的延伸长度与切割深度。250~208Ma期间,郯庐断裂带开始形成,延展长度不超过1500km,切割深度在15~20km,是以左行走滑活动为主的基底断裂。135~52Ma时期,该断裂带大幅度地扩展了长度(达3500km),切割深度在30~40km之间,为略具右行平移活动的正断层,属地壳断裂。233Ma以来,断裂带以向下深切为主,深度从50km左右逐渐加深到80~100km,终于形成岩石圈断裂 相似文献
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在大别造山带东端和苏鲁造山带西端,郯庐断裂带存在着同造山期和早白垩世两期左旋走滑韧性剪切带,在张八岭隆起南段迄今为止只发现了早白垩世的走滑剪切带。这些剪切带由若干条小型韧性剪切带组成,带内糜棱岩都具有陡倾的糜棱面理和平缓的矿物拉伸线理。野外构造、显微构造及石英C轴组构皆指示了左旋走滑剪切指向。新生矿物组合和矿物变形行为分析显示大别山东端郯庐早、晚两期剪切带主要形成于中绿片岩相的变质温度环境,张八岭隆起南段剪切带主要形成于高绿片岩相的变质温度环境,苏鲁造山带西端郯庐早、晚两期剪切带则形成于高角闪岩相的变质温度环境。糜棱岩内基质中新生白云母的电子探针分析指示大别山东端和张八岭隆起南段出露的郯庐韧性剪切带形成于低压环境下,而苏鲁造山带西端的郯庐韧性剪切带形成于高压榴辉岩相环境。这些详细的构造研究显示:在华北与华南板块的碰撞造山期郯庐断裂带以左旋走滑构造型式存在,而在早白垩世太平洋构造域中它又再次发生了强烈的左行平移。 相似文献
19.
The NE to ENE trending Mesozoic Xingcheng-Taili ductile shear zone of the northeastern North China Craton was shaped by three phases of deformation. Deformation phase D1 is characterized by a steep, generally E–W striking gneissosity. It was then overprinted by deformation phase D2 with NE-sinistral shear with K-feldspar porphyroclasts forming a subhorizontal low-angle stretching lineation on a steep foliation. During deformation phase D3, lateral motion accommodated by ENE sinistral strike-slip shear zones dominated. Associated fabrics developed at upper greenschist metamorphic facies conditions and show the deformation characteristics of middle- to shallow crustal levels. In some parts, the older structures have been in turn overprinted by late-stage sinistral D3 shearing. Finite strain and kinematic vorticity in all deformed granitic rocks indicate a prolate ellipsoid (L-S tectonites) near plane strain. Simple shear-dominated general shear during D3 deformation is probably of general significance. The quartz c-axis textures indicate prism-gliding with a dominant rhomb <a> slip and basal <a> slip system formed mainly at low-middle temperatures. Mineral deformation behavior, quartz c-axis textures, quartz grain size and the Kruhl thermometer demonstrate that the ductile shear zone developed under greenschist facies metamorphic conditions at deformation temperatures ranging from 400 to 500 °C. Dislocation creep is the main deformation mechanism at a shallow crustal level. Fractal analysis showed that the boundaries of recrystallized quartz grains had statistically self-similarities. Differential stresses deduced from dynamically recrystallized quartz grain size are at around 20–39 MPa, and strain rates in the order of 10−12 to 10−14 s−1. This indicates deformation of granitic rocks in the Xingcheng-Taili ductile shear zone at low strain rates, which is consistent with most other ductile shear zones. Hornblende-plagioclase thermometer and white mica barometer indicate metamorphic conditions of medium pressures at around ca. 3–5 kbar and temperatures of 400–500 °C within greenschist facies conditions. The main D3 deformation of the ENE-trending sinistral strike-slip ductile shearing is related to the roll-back of the subducting Pacific plate beneath the North China Craton. 相似文献