《GFF》2012,134(4):335-357

Abstract

Metamorphism in the nappe terrains of the Central Scandinavian Caledonides is characterized by inverted gradients and other indications of disequilibrium caused by the superposition of nappes of various metamorphic grade and the translation of the nappe pile onto the margin of the Baltic Shield. In the lower nappes there is a gradual westward increase of grade, but some inverted gradients persist. In the upper allochthon, the variation of metamorphism is essentially vertical. It is possible to identify and evaluate parageneses formed prior to, during, and after nappe emplacement. Their interpretation in terms of separate Caledonian or Precambrian events is often ambiguous. Early Caledonian metamorphism apparently represented a range of P-T-conditions. The build-up and translation of the nappe pile was characterized by transient high pressure conditions. A metamorphic pulse, manifest particularly in the west, succeeded nappe emplacement onto the Baltic Shield. Strain-induced metamorphism in the vicinity of thrusts contributes to the overall metamorphic pattern. A variety of P/T-ratios characterized metamorphism in the Scandinavian Caledonides. This conclusion modifies current concepts about an essentially Barrovian metamorphic evolution of the orogen.  相似文献   

Taimyr Peninsula( Arctic Siberia) in Late Precambrian:tectonic thrust sheets and geodynamic evolution     

Sergey G.Samygin 《东北亚地学研究》2014,(3)

Structural relationships between the Neoproterozoic rock complexes of a continental massif,island arc and back-arc basin geodynamic affinities are described and considered in this work based on field observations within the northeastern segment of the Central Taimyr tectonic zone distinguished in the late Hercynian foldthrust belt of Taimyr Peninsula. As is established for the first time,rock complexes of the continental massif with the early Late Riphean( Tonian-Cryogenian) volcanogenic-sedimentary cover occur in the study region as the allochthonous syn- and post-sedimentary thrust sheets buried in or thrust over deposits of a back-arc basin,which accumulated in the terminal Late Riphean( Cryogenian)--initial Vendian( Ediacaran). These and other results of the large-scale structural observations elucidate important details of the region tectonic development in the Late Precambrian,when two lateral ensembles of the Neoproterozoic structures originated in the region. In the first half of the Neoproterozoic,the regional tectonic ensemble included the oceanic plate abut on the continental massif with a primitive volcano-plutonic belt. The subsequent system of an island arc and marginal backarc basin originated in the second half of the Neoproterozoic and existed approximately till the mid-Vendian( Ediacaran) phase of the intense formation of thrust sheets in the region.  相似文献   

    

Yongsheng Wang  Ziqiang Tian  Chuanzhong Song  Qiao Bai 《Geological Journal》2019,54(2):913-928

The Jiulianshan anticlinorium is located at the southern part of the Mount Maoshan–Jiulianshan in the Lower Yangtze region, where a number of new‐found thrust faults were identified. Movement of these thrust faults had resulted in Palaeozoic strata lying unconformably above Cretaceous strata. However, the Lower Yangtze region was mostly under an extensional tectonic regime during the Late Mesozoic, which is inconsistent with existence of the nappe in the Mount Maoshan–Jiulianshan. Therefore, what the structural characteristics are and when these thrust faults developed are important for understanding the evolution of the South China Block. Based on detailed field observations, these new‐found thrust faults outcropped in the Liqiao, Yangxian, and Miaopu areas. These faults, SE‐dipping deeply, developed a meters‐wide fault‐and‐fracture zone of width in meters. The footwall was composed of the Early Cretaceous pyroclastic rock or tuff, which indicates that these faults developed since the Early Cretaceous. Two undeformed dykes formed in the fault‐and‐fracture zone of Miaopu area and a footless intrusion in the hanging wall, which give emplacement ages of ca. 132 Ma by using zircon U–Pb LA‐ICP‐MS dating and thus implies that thrust fault motion occurred prior to or around this time. The volcanic tuff and pyroclastic rocks, located in the footwall of the Yangxian and Miaopu thrust fault, are dated at ca. 137 and 134 Ma, respectively, indicating that fault motion must have occurred after this time. The Qiaotouyang pluton emplaced in the core of one of the folds in the fold‐and‐thrust belt at ca. 141 Ma, which indicates that the fold‐and‐thrust belt of Tongling Uplift formed prior to 141 Ma. Integrating other evidences, such as magmatic quiescence, large‐scale and short‐duration volcanic eruptions, and beginning time of metamorphic core complex and rift basin, it is inferred that Early Yanshanian thrust faults were reactivated during the Late Mesozoic, resulting in thrusting within the Jiulianshan anticlinorium.  相似文献   

Fault Characteristics in Longmen Mountain Thrust Belt,Western Sichuan Foreland Basin,China   总被引：1，自引：0，他引：1  

万桂梅  汤良杰  杨克明  金文正  吕志洲  余一欣 《中国地质大学学报(英文版)》2008,19(6):611-624

Through field geological survey,the authors found that abundant thrust faults developed in the Longmen (龙门) Mountain thrust belt.These faults can be divided into thrust faults and strike-slip faults according to their formation mechanisms and characteristics.Furthermore,these faults can be graded into primary fault,secondary fault,third-level fault,and fourth-level fault according to their scale and role in the tectonic evolution of Longmen Mountain thrust belt.Each thrust fault is composed of several secondary faults,such as Qingchuan (青川)-Maowen (茂汶) fault zone is composed of Qiaozhuang (乔庄) fault,Qingxi (青溪) fault,Maowen fault,Ganyanggou (赶羊沟) fault,etc..The Longmen Mountain thrust belt experienced early Indosinian movement,Anxian (安县) movement,Yanshan (燕山)movement,and Himalayan movement,and the faults formed gradually from north to south.  相似文献   

山前冲断带砂砾岩储层发育机制及控制因素：以柴达木盆地昆北油田切12区为例     

宫清顺  刘占国  王波  朱超  宋光永  伍劲 《地球科学》2024,49(1):55-70

柴达木盆地昆北断阶带为大型山前压扭冲断构造带,该构造带上的昆北油田切12区下干柴沟组下段发育厚层冲积扇沉积的砂砾岩储层.明确储层微观特征及发育控制因素,对冲断带砂砾岩储层评价与油藏治理具有重要意义.运用铸体薄片、X-衍射、扫描电镜、常规压汞与恒速压汞等测试分析资料,系统研究冲积扇砂砾岩储层微观特征,明确储层发育的主控因素.结果表明,切12区砂砾岩储层具有成分成熟度低、结构成熟度低的岩石学特征,储集空间类型具双重孔隙介质特征,发育2类储层结构模态、4类储集空间类型、4类储层孔隙结构,储层物性为低孔、特低渗型储层,成岩作用阶段为早成岩阶段B期.在砂岩动力成岩作用相同的地质背景下,成岩作用对储层改造的影响是相对均衡的,储层发育程度的差异主要受控于沉积作用差异而导致的碎屑组成与结构差异,泥质含量是储层发育程度差异的主控因素,明确泥质含量上限为8%,颗粒分选对储层性质起重要控制作用.建立了基于泥质含量、物性、孔隙结构和产能指标的储层评价分类标准,将砂砾岩储层划分为4类;运用该认识指导油藏综合治理,并取得应用实效.  相似文献   

塔里木盆地东北缘吐格尔明背斜和阳北断裂带构造分析          下载免费PDF全文

蒋俊  缪卫东  赵凤全  李君  袁瑞  周慧  邓晓睿  王珊  董才源  黄智斌  师斌  汲雷昌 《地质科学》2024,59(2):288-299

吐格尔明背斜和阳北断裂位于塔里木盆地北缘,南天山山前库车褶皱冲断带的东段,两者均为基底卷入型构造.阳北断裂是一个反转构造,其变形历史可以追溯到侏罗纪—白垩纪的正断层;新生代构造反转,发生了多期冲断变形加速期,分别发生于白垩纪末—古近纪初、古近纪末—新近纪初、中新世早期、上新世和第四纪.吐格尔明背斜构造带是阳北断裂中新世早期及以后的冲断作用派生出来的一个次级基底卷入型构造变形带.它由吐格尔明背斜及其南、北两条呈背冲关系的逆冲断层组成.背斜核部元古宇变质岩出露地表;中、新生界直接不整合于变质岩之上,缺失全部古生界,说明研究区可能属于一个长期存在的古生代古隆起.  相似文献   

柴北缘骆驼泉剖面新生代地层磁组构特征及其构造意义          下载免费PDF全文

栗兵帅  王江汇  颜茂都  张伟林  鲍晶 《地球物理学报》2024,67(1):205-224

青藏高原东北部新生代构造演化对理解高原隆升和变形模式具有重要意义,而目前对于该地区挤压应力方向转变过程仍存在很大争议.本文对柴北缘逆冲带北西部骆驼泉剖面新生代地层开展系统磁组构(本文特指磁化率各项异性)研究,以揭示该地区挤压应力方向的转变特征.系统岩石磁学结果表明,骆驼泉剖面新生代样品中主要磁性矿物是顺磁性组分和赤铁矿以及少量磁铁矿.通过对磁组构特征分析及其与古水流方向对比表明,骆驼泉剖面新生代地层磁组构主要为初始变形磁组构,可用于指示沉积成岩时期的挤压应力方向.磁组构结果揭示,骆驼泉地区挤压应力方向在上干柴沟组下部沉积时期为NNE-SSW向,而上干柴沟组上部和油砂山组沉积时期转变为NE-SW向.结合柴北缘逆冲带已有磁组构结果指出,该地区早期N-S向或NNE-SSW向挤压应力可能与印度—欧亚板块早新生代以来近N-S向碰撞挤压过程有关,指示印度—欧亚碰撞的挤压应力自下干柴沟组下部沉积时期就已传播至高原东北部地区;而后期NE-SW向挤压应力方向与该地区现今GPS揭示的上地壳运动方向一致,可能与该时段高原东北部巨型走滑断裂构造体系(尤其是阿尔金断裂)有关.此外,柴北缘逆冲带新生代挤压应力方向转变在其北西部起始于上干柴沟组下部沉积时期,而南东部起始于上油砂山组下部沉积时期,与地震反射剖面揭示的断裂活动等地质证据共同揭示柴北缘逆冲带新生代的构造活动自靠近阿尔金断裂的北西部向南东部传播和扩展.综合分析青藏高原东北部地区挤压应力方向转变和其他地质证据发现,挤压应力方向转变显示出自柴北缘逆冲带北西部向东、西和南向扩展特征,与阿尔金断裂在上干柴沟组下部-上油砂山组下部沉积时期剪切应力集中于断裂本身,而上油砂山组下部沉积以来开始散布于高原东北部内部地区的两阶段走滑活动相关.  相似文献   

矿井群冲击地压发生机理与控制技术探讨          下载免费PDF全文

张宁博  许乾海  欧阳振华  李一哲  史庆稳  秦洪岩  易海洋 《煤田地质与勘探》2024,48(10):36-46

煤矿开采中,人工爆破、顶板垮断等震源激发应力波易诱发断层失稳并导致冲击地压等灾害。

以河南义马矿区F16逆冲断层为研究对象,通过开展断层动光弹实验、数值模拟实验和理论分析,对应力波在断裂结构中的传播规律和应力波作用下断层摩擦能演化特征进行了研究,探讨了震源位置及能量对逆冲断层滑移的扰动规律,阐释了应力波扰动下逆冲断层失稳机理和失稳类型。

研究结果表明：(1)应力波传播会被断层阻隔,并造成断层活化加剧、摩擦能迅速增大。(2)震源应力波能量增大可加强断层自锁效应,当能量超过一定阈值时断层才会解锁。(3)应力波自上至下分区扰动断层并造成断层滑移,其滑移模式受初始应力状态和应力波扰动强度影响。(4)初始高水平静载和强应力波扰动是断层失稳的必要条件。研究成果对断层型灾害防控技术发展具有重要的指导意义。

  相似文献   

    

James F Ni 《Journal of Earth System Science》1989,98(1):71-89

The Himalayan mountains are a product of the collision between India and Eurasia which began in the Eocene. In the early stage of continental collision the development of a suture zone between two colliding plates took place. The continued convergence is accommodated along the suture zone and in the back-arc region. Further convergence results in intracrustal megathrust within the leading edge of the advancing Indian plate. In the Himalaya this stage is characterized by the intense uplift of the High Himalaya, the development of the Tibetan Plateau and the breaking-up of the central and eastern Asian continent. Although numerous models for the evolution of the Himalaya have been proposed, the available geological and geophysical data are consistent with an underthrusting model in which the Indian continental lithosphere underthrusts beneath the Himalaya and southern Tibet. Reflection profiles across the entire Himalaya and Tibet are needed to prove the existence of such underthrusting. Geodetic surveys across the High Himalaya are needed to determine the present state of the MCT as well as the rate of uplift and shortening within the Himalaya. Paleoseismicity studies are necessary to resolve the temporal and spatial patterns of major earthquake faulting along the segmented Himalayan mountains.  相似文献   

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WANG D  YANG Biao  XU Daxing  LI Xiaoshuang  FAN Songhao  SU Panyun  MA Huchao  WANG Guilong  WANG Gaotian  MA Lei  LIU Wencan 《《地质学报》英文版》2025,99(2):499-521

Controversy is ongoing regarding the relationship between ore formation and the structural evolution of the Hadamengou gold deposit. To address this issue, we conducted a comprehensive investigation of mineralization-related structures, geochronology and Fe isotopes. From the perspective of spatial evolution, hydrothermal fluids originating from the Shadegai and Xishadegai plutons have extracted accumulated ore-forming elements from the Wulashan Group (Ar2WL) and then evolved, initiating at Exploration Line 11 and migrating eastwards and westwards along the EW-trending thrust fault system to form orebodies. From the temporal evolution standpoint, the Wulashan Group (Ar2WL) experienced diagenesis (2591.00 Ma to 2204.00 Ma) and metamorphism (2074.00 Ma to 1625.00 Ma) from late Neoarchean to early Paleoproterozoic, when ore-forming materials were initially accumulated; in the early Paleozoic (440.71 Ma to 425.00 Ma), the collision led to the formation of early-stage EW-trending imbricated thrust faults, which established a fundamental structural framework for the orefield and further accumulated ore-forming materials; from the late Paleozoic to the Mesozoic, multiple subsequent episodes of regional tectonic-magmatic-hydrothermal events have superimposed, modified and reactivated the thrust fault system. Notably, the Triassic period, particularly between 245.00 Ma and 217.90 Ma, is considered to be a primary ore-forming stage. In summary, the intricate relationship between ore-formation and structural evolution has been fundamentally elucidated.  相似文献