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鄣公山地区位处皖赣交界地带,区内广泛分布一套浅变质的陆缘细碎屑岩为主含少量火山物质的复理石建造体,大量高精度同位素测年数据显示,该浅变质地层形成于820~840Ma新元古代。经系统野外调查,在该地层中首次解析出5期褶皱变形,其中F1以原始层理(S0)为形变面形成的紧闭同斜、平卧等形态的露头尺度级片内无根褶皱;F2以早期构造面理(S1∥S0)为形变面的轴向近东西向开阔斜歪及同斜褶皱;F3属与大规模逆冲推覆构造相关的紧闭同斜或斜歪褶皱;F4为与燕山期花岗质岩浆热隆升有关的轴面北倾的透入性不对称紧闭下滑褶皱群;F5为分布于区域脆性平移走滑断裂带附近的倾竖褶皱,上述褶皱分别对应不同的构造变形旋回。本文重点阐述褶皱变形的几何学、叠加样式、变形序次、运动学特征,并对变形机制及大陆动力学等进行分析。 相似文献
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新疆于田塔木其铜锌矿是西昆仑造山带内众多与火山作用有关的热水喷流沉积块状硫化物矿床之一,但该矿的空间位态与典型层控矿床不一致。研究区经历的主要构造运动期次可分为3期,S2期构造运动对现今岩石及矿体的空间分布状态起决定性作用。野外及镜下详细观察表明,S2期构造变形为强压应力兼具一定剪切性质的脆韧性变形,对研究区内原始层理及矿体进行了构造置换。S2期构造透镜体长轴及劈理产状统计表明,构造透镜体空间展布状态小受S2期劈理控制,透镜体最大压扁面平行于S2期劈理面分布,研究区在S2期遭受了强烈的南北挤压应力。通过对小型褶皱、透镜体的观测及劈理的统计,结合构造剖面的测制,推测矿体上一级构造样式为大型无根褶皱,矿体本身为加厚的Z型次级褶皱形成的透镜体,矿体所处部位可能为无根褶皱的背形南翼或向形北翼。S3期节理产状要素统计表明,在S3期研究区发生了南北挤压应力作用下的脆性破裂,这些破裂对矿体的分布有一定影响。 相似文献
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论述了邓家山铅锌矿床含矿硅质岩.即含矿层或矿源层的特证.矿区构造变形特证,滑断构造的存在,劈理的广泛发育,片内无根褶皱的出现.剪切褶皱和紧闭倒转背斜等和4期构造变形序列.从动力作用成矿观点和动力矿床形成的基本条件,来认识邓家山铅锌矿床地质特征和分析矿床形成机制,提出了邓家山铅锌矿床为层控型动力热液成因矿床的新认识. 相似文献
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吉林省金城洞绿岩带构造变形序列 总被引:5,自引:1,他引:5
金城洞绿岩带自晚太古代以来经历了多期变形:D_1变形幕,形成片理、片麻理及无根褶曲,是深部构造层次的产物;D_2变形幕,形成轴面片理及一系列轴向NW或NWW向的紧闭同斜或平卧褶皱,并伴有英云闪长岩—奥长花岗岩侵入,是中深部构造层次的产物;D_3变形幕,形成大型开阔褶皱,晚期形成韧性剪切带,是中浅部构造层次的产物。这三幕变形奠定了本区的基本构造格架。D_4变形幕在中浅构造部位形成NE向开活褶皱。古生代以来,本区主要发生脆性变形。 相似文献
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小秦岭地体中的褶皱包括露头褶皱和宏观褶皱和宏观褶组成褶皱的面理为闪生构造面理。露头褶皱为地壳早期伸展机制下发生左行张扭剪切作用产生的构造形迹;宏观褶皱为侵入岩浆穹起、底辟作用向外扩张窨推拉围岩形成的构造格局。 相似文献
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阳山金矿产于勉阳-略阳板块缝合带中,经历了以逆冲推覆构造为主的复杂构造改造。通过构造研究把阳山金矿内的构造分出四期。第一期构造变形表现为由北向南逆冲,为韧性变形,构造置换明显、完全,形成透入性面理,剪切褶皱、无根褶皱、S-C组构、压力影、旋转碎斑、多米诺骨牌、石香肠等构造发育,构造岩为糜棱岩、超糜棱岩、构造片岩,并伴随有大规模的花岗岩岩浆活动,形成于三叠纪末-早侏罗世。第二期构造变形为由南向北的伸展构造,主要表现对第一期面理的改造和再利用,多为韧性变形,可见剪切褶皱、旋转碎斑等构造,构造岩为糜棱岩,顺层张性石英脉的发育,并伴随有大规模的岩浆活动,形成于侏罗纪末-早白垩世早期。第三期构造为脆韧性变形,为由南向的北逆冲推覆构造,主要表现为对先期构造的改造,使阳山金矿区南部面理产状发生倒转,形成膝折构造,构造岩为糜棱岩、初糜棱岩,形成于早白垩世晚期。第四期构造为表层次脆性的由南向北的伸展构造,形成构造角砾岩、碎裂岩等脆性构造岩,同时有石英脉和方解石脉顺断层侵入,本期构造形成于古近纪。 相似文献
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构造解析证实,金州韧性剪切带是以右行走滑为主的大型缓倾斜剪切带,带内发育的糜棱面理-小型褶皱-香肠构造及肿缩构造-S?C组构的系列,以及广泛分布的拉伸线理,是总体非共轴持续变形条件下,带内共轴与非共轴线路相结合的结果,并且后者占主要地位。糜棱面理是最早生成的透入性构造,对其他构造的形成有重要作用。剪应变量(γ)大小与糜棱岩化程度有直接关系。鞘褶皱多发育于γ≥10地段。微构造发育机制的变化是:γ 由低到高,石英变形从低温晶体-塑性转向塑性变形与重结晶作用; 而云母矿物从外形定向转向粘性颗粒-边界滑动。 相似文献
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Four phases of deformation are recorded by minor structures in the New Harbour Group (NHG) of southern Holy Island. The regional schistosity in these rocks is a differentiated crenulation cleavage of D2 age. An earlier preferred orientation (S1) is commonly preserved as crenulations within the Q-domain microlithons of the S2 schistosity and is demonstrably non-parallel to bedding. F3 folds are widely developed in S2 and, to a lesser extent, in bedding. S3 crenulation cleavage is sporadically developed but can be intense locally. A major antiformal fold exists in the NHG near Rhoscolyn. This fold is of D3 age since it clearly deforms S2 schistosity and is consistent with the vergence of F3 minor structures. All planar structures are deformed by folds of D4 age. © 1997 John Wiley & Sons, Ltd. 相似文献
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《地学前缘(英文版)》2020,11(5):1495-1509
The Qinling-Qilian connection zone(QQCZ) is a key area to reveal the relationship and to make a link of the North Qinling and the North Qilian orogens,China.Here we present U-Pb dating data of detrital zircons from four sedimentary/metasedimentary rocks in the QQCZ and the southwestern North China Block(NCB) and detailed regional structural data.Three episodes of fold deformation(D_1,D_2 and D3) are distinguished in the QQCZ,with the former two occurred during the early Paleozoic.The D_1 deformation is mainly characterized by regionally penetrative schistosity and some residual rootless intrafolial folds due to the intensive superpositions by the subsequent D_2 and D3 deformations.The D_2 deformation characterized by tight folds,associated axial plane foliations and crenulation lineations indicates a stress field characterized by NNE-SSW-directed compression,which may be induced by the collision between the NCB and the southern blocks.The D3 deformation which might occur during the Mesozoic is marked by upright open folds and kink bands.The similarity of the detrital zircon age spectra of the Huluhe Group in the North Qilian Orogen and the Erlangping Group in the North Qinling Orogen suggests that the two groups have similar provenance,which may indicate that the North Qilian Orogen corresponded to the North Qinling Orogen in a regional tectonic framework.In addition,the remarkable age peak at~435 Ma of the detrital zircon age spectrum of the Duanjiaxia Formation in the southwestern NCB indicates that this formation obtained the provenance of the North Qilian and North Qinling orogens,which may be generated by the collage of the southwestern NCB and the QQCZ during the Late Ordovician-Early Silurian.Based on structural,detrital zircon and metamorphic data,we suggest that the North Qilian and North Qinling orogens underwent similar evolution during the early Paleozoic due to the closure of the North Qilian and the Kuanping oceans which located at the northern boundary of the Proto-Tethys Ocean. 相似文献
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P. K. Gangopadhyay 《Journal of Earth System Science》1995,104(3):523-537
The Dating rocks and Darjeeling gneisses, which constitute the Sikkim dome in eastern Himalaya, as well as the Gondwana and
Buxa rocks of ‘Rangit Window’, disclose strikingly similar sequences of deformation and metamorphism. The structures in all
the rocks belong to two generations.
The structures of early generation are long-limbed, tight near-isoclinal folds which are often intrafolial and rootless. These
intrafolial folds are associated with co-planar tight folds with variably oriented axes and sheath folds with arcuate hinges.
Penetrative axial plane cleavage and mineral lineation are related structures; transposition of bedding is remarkable. This
early phase of deformation (D
1) is accompanied by constructive metamorphism. The structures of later generation are open, asymmetrical or polyclinal; a
crenulation cleavage or discrete fracture may occur. The structures of early generation are distorted by folds of later generation
and recrystallized minerals are cataclastically deformed. Recrystallization is meagre or absent during the later phase of
deformation (D
2).
The present discussion is on structures of early generation and strain environment during theD
1 phase of deformation. The concentration of intrafolial folds in the vicinity of ductile shear zones and decollement or detachment
surface (often described as ‘thrust’) may be considered in this context. The rocks of Darjeeling-Sikkim Himalaya display minor
structures other than intrafolial folds and variably oriented co-planar folds. The state of finite strain in the rocks, as
observed from features like flattened grains and pebbles, ptygmatic folds and boudinaged folds indicate combination of flattening
and constrictional type strain. The significance of the intrafolial folds in the same rocks is discussed to probe the environment
of strain during progressive deformation (D
1). 相似文献
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The Feiran–Solaf metamorphic belt consists of low-P high-T amphibolite facies, partly migmatized gneisses, schists, amphibolites and minor calc-silicate rocks of metasedimentary origin. There are also thick concordant synkinematic sheets of diorite, tonalite and granodiorite orthogneiss and foliated granite and pegmatite dykelets. The gneissosity (or schistosity) is referred to as S1, and is almost everywhere parallel to lithological layering, S0. This parallelism is not due to transposition. The gneissosity formed during an extensional tectonic event (termed D1), before folding of S0. S1 formed by coaxial pure shear flattening strain (Z normal to S0, i.e. vertical; with X and Y both extensional and lying in S1). This strain also produced chocolate tablet boudinage of some layers and S1-concordant sills and veins. S1 has a strong stretching lineation L1 with rodding characteristics. Within-plane plastic anisotropy (lower ductility along Y compared to along X) resulted in L1-parallel extensional ductile shears and melt filled cracks. Continued shortening of these veins, and back-rotation of foliations on the shears produced intrafolial F1 folds with hinges parallel to the stretching lineation. F1 fold asymmetry variations do not support previous models involving macroscopic F1 folds or syn-gneissosity compressional tectonics. The sedimentary protoliths of the Feiran–Solaf gneisses were probably deposited in a pre-800 Ma actively extending intracratonic rift characterizing an early stage of the break-up of Rodinia. 相似文献
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New structural data obtained on the Birimian terranes of the Kolia-Boboti sedimentary Basin, the eastern part of the Dialé-Daléma Supergroup in the Kédougou-Kéniéba inlier show two major phases of Eburnean compressional deformation: (1) a D1 phase of thrusting tectonics affected the Lower Birimian B1 tourmalinized sediments. This first tectonic phase is characterized by isoclinals overturned to recumbent folds P1 with N040° 20°NE trending axis, associated with axial plane schistosity S0S1 which is mainly transposed in the bedding; (2) a D2 phase of compressional (D2a) and transpressional (D2b) tectonics is responsible for the crossfolds P2a-P2b exhibiting curved axes. These P2 folds are associated with the major schistosity S2, north-south to SW-NE trending, mainly dipping to the south-east. The S2 schistosity is mostly displayed in the large shear zones corridors where it steeply dips locally toward the north-west. A north-west vergence thrusting phase (D2c) of flats and ramps, associated with reverse folds, represents the last Eburnean event. This geometrical feature is characteristic of a “positive flower structure”. These different Eburnean compressional phases are separated by extensional deformation which is characterized by sedimentary deposits and volcanic flows. 相似文献
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本文运用构造解析的方法,结合地层学、岩石学及地球化学等方面的研究,搞清了鞍山地区元古宙岩群的构造变形规律,建立了构造变形序列,探讨了该区韧性变形带的分类性质、形成机制、形成时代以及韧性变形带与构造序列的关系,在此基础上总结出了本区地质构造的演化规律,以及构造变形对铁矿床的控制规律。 相似文献
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In the high‐grade (granulite facies) metamorphic rocks at Broken Hill the foliation is deformed by two groups of folds. Group 1 folds have an axial‐plane schistosity and a sillimanite lineation parallel to their fold axes; the foliation has been transposed into the plane of the schistosity by these folds. Group 2 folds deform the schistosity and distort the sillimanite lineation so that it now lies in a plane. Both groups of folds are developed as large folds. The retrograde schist zones are zones in which new fold structures have formed. These structures deform Group 1 and Group 2 folds and are associated with the formation of a new schistosity and strain‐slip cleavage. The interface between ore and gneiss is folded about Group 1 axial planes but about axes different from those in the foliation in the gneiss. On the basis of this, the orebody could not have been parallel to the foliation prior to the first recognizable structural and metamorphic events at Broken Hill. The orebody has been deformed by Group 2 and later structures. 相似文献