东阿拉善地块诺尔公群石英岩的碎屑锆石年龄特征——物源区制约及其地质意义

传统上将阿拉善地块东部变质基底"阿拉善岩群"之上的一套以石英岩、浅粒岩、碳酸盐岩及碎屑岩为主的浅变质地层称为诺尔公群,并根据区域地层对比及叠层石化石将其归为"长城纪"。为进一步限定地层时代,对诺尔公群底部3件石英岩进行LA-MC-ICP-MS锆石U-Pb测年,获得的年龄主要集中在2 530~2 500 Ma和1 950~1 850 Ma两个年龄段内,另外还获得少量年龄为~1.69 Ga、~2.0 Ga、~2.15 Ga、~2.35 Ga、~2.7 Ga和~3.4 Ga的锆石。其中,最年轻的碎屑锆石年龄限定了诺尔公群底部石英岩的沉积时代晚于1.69 Ga,结合上覆地层的年龄数据将诺尔公群的沉积时代大致限定为1.69~1.29 Ga,肯定了阿拉善地块存在中元古代地层。石英岩中~2.5 Ga和~1.95 Ga两个显著的碎屑锆石年龄峰符合典型的华北克拉通物源区特征,因此认为,阿拉善地块在太古代-中元古代具有与华北克拉通相似的构造环境,是华北克拉通的一部分。     

狼山地区叠布斯格岩群变形研究及其构造意义

阿拉善东北缘狼山地区的叠布斯格岩群（杂岩）作为阿拉善地块前寒武纪基底之一,主要出露有条痕状黑云斜长片麻岩、斜长角闪片麻岩及透镜状斜长角闪岩,夹透辉石大理岩和磁铁石英岩等。本次研究通过构造解析与填图,系统分析了狼山地区叠布斯格岩群构造变形样式、变形期次与时限。研究显示,古元古代变质杂岩叠布斯格岩群至少记录了四期变形,第一期变形主要表现为片麻岩早期面理的枢纽近E- W向褶皱变形（D1）,轴面倾向NNW,应与华北克拉通统一化过程有关;第二期为近N- S向褶皱变形（D2）,褶皱枢纽向NNE倾伏,古生代时期阿拉善地块与华北板块增生拼合,在阿拉善地块东缘产生近东西向挤压,在狼山地区形成枢纽近N- S向的褶皱;第三期变形为NE向巴彦乌拉山- 狼山断裂带的左行韧性走滑剪切作用（D3）,中-晚三叠世扬子板块与华北板块碰撞造成的阿拉善地块相对华北板块沿巴彦乌拉山- 狼山断裂发生左行剪切运动,使早期构造发生逆时针旋转,是狼山地区一期重要的变形事件;第四期为NE- SW向紧闭褶皱（D4）,褶皱轴面多倾向NW,晚侏罗世来自古太平洋的俯冲和鄂霍茨克洋的闭合产生的NW- SE向挤压,使叠布斯格岩群片麻岩及后期糜棱岩化花岗岩再次发生枢纽NE- SW向褶皱变形。     

贺兰构造带北段-桌子山中-新生代构造变形特征

贺兰山构造带位于鄂尔多斯盆地与阿拉善地块之间,经历了元古代以来长期的构造演化过程。贺兰构造带北段的桌子山具有复杂的构造样式,该构造样式记录了鄂尔多斯块体、阿拉善块体以及古亚洲洋构造演化的丰富信息。详细的野外构造解析揭示,贺兰构造带北段桌子山地区自中生代以来主要经历了多期挤压构造变形。第一期构造变形以三叠系及其以下地层中的NWW向宽缓褶皱为代表,指示了晚三叠纪NNE向的挤压作用;第二期以侏罗系及其以下地层中的NE走向构造为代表,指示了晚侏罗世NW向的挤压作用;第三期构造变形以黄河断裂发生右旋走滑及其两侧早期变形构造线走向及古应力场方向之间30°夹角差异为代表。黄河断裂以东白垩系及其以上地层结构稳定,结合前人古地磁研究结果,认为第三期构造变形为桌子山沿黄河断裂发生近30°逆时针旋转,变形时间为新生代。     

阿拉善地块东缘新生代中新世挤压变形及动力学背景

在阿拉善地块东缘发现新生代中新世挤压构造，形成近SN或NE-SW走向的逆冲断层及卷入新生代地层的褶皱.其形成背景关系到阿拉善地块新生代的变形特征以及与青藏高原扩展的关系.为了进一步探讨阿拉善地块东缘的挤压构造是否受青藏高原扩展控制，为青藏高原北缘新生代扩展过程的研究提供资料，通过详细地质填图、区域地质调查与对比方法，确定了这些挤压构造的几何样式以及运动学特征，结合断层滑动矢量，恢复出变形时的古应力场.室内外的分析表明，形成这些挤压构造的最大主应力方位为NW-SE或近EW向，结合盆地地震反射资料、卷入构造的地层，推测变形的时代是中新世中晚期.这期变形的动力可能是阿拉善地块受到青藏高原北缘的挤压向东运动所致.同时在阿拉善地块向东运动的过程中，其内部发育的早期东西向构造带发生右行走滑，和阿拉善东缘的挤压构造一同调节地块的变形.晚中新世之后，高原东北缘最大主应力方位发生顺时针旋转，阿拉善东缘挤压构造被后期构造叠加.      

内蒙古狼山地区新元古代狼山群变形特征及区域构造意义

狼山群作为阿拉善地块东北部重要的前寒武系地层单元,记录了复杂的构造变形演化历史。本文通过对狼山西南段出露的新元古代狼山群进行构造地质试点填图、剖面测制等方面的研究,总结了狼山群构造变形特征,并对其变形时代和期次进行了初步划分。研究表明狼山群第一期构造变形特征表现为一系列同斜倒转褶皱构造(D1),第二期为近东西向的韧性右行走滑剪切(D2),第三期为北东向巴彦乌拉山—狼山断裂活动对狼山群构造变形进行改造(D3)。结合该地区前人研究成果及年代学资料认为:新元古代狼山群同斜倒转褶皱主要受到古亚洲洋向南俯冲,在古生代晚期沿恩格尔乌缝合带与阿拉善地块北缘拼合,导致近南北向的构造挤压,在狼山地区形成了早期枢纽NEE-EW向的褶皱;晚古生代末期-中生代早期古亚洲洋关闭后发生的板内变形在狼山地区形成韧性右行剪切;三叠纪中晚期韧性左行剪切形成北东向走滑断裂,并使早期形成的褶皱枢纽走向转为北东,奠定了狼山地区现今的构造格局。     

嫩江洋闭合机制:来自内蒙古东南部扎赉特旗地区音德尔杂岩构造变形样式与时代的启示SCIEI北大核心CSCD

嫩江洋闭合机制是大兴安岭地区一个争议较大的科学问题。音德尔杂岩为大兴安岭与松辽盆地盆山结合带上新发现的一套俯冲增生杂岩,岩石强烈韧性变形,其构造变形样式及时间较好的记录了嫩江洋闭合过程。该套杂岩基质由绢云片岩、绿泥石片岩及阳起石片岩等组成,岩块主要包括闪长岩、辉长岩、玄武安山岩及花岗岩。宏观变形样式观察和微观组构分析表明,音德尔杂岩发育两期构造变形:早期变形以倾向NW的片理、片麻理及糜棱面理为标志,并发育有NNW向倾伏的构造线理,线理倾伏角一般较大,指示NW-SE方向强烈挤压背景下形成的一期逆冲线理;晚期变形以NE向倾伏的低角度矿物拉伸线理为标志,石英及长石等矿物通过晶内位错滑移与膨凸式重结晶等塑性流变方式显著定向拉长,构造形迹指示一期NE-SW走向的左行走滑剪切作用,晚期线理普遍改造或置换早期线理。两期构造变形事件分别对应兴安增生地体与松嫩地块碰撞造山早期的强烈挤压阶段和造山晚期伸展走滑调整阶段。构造岩与围岩接触关系年代学研究限定音德尔杂岩构造变形发生于早石炭世末期(323Ma)之前。早石炭世早期嫩江洋开启双向俯冲模式,在兴安增生地体东缘和松嫩地块西缘形成大量增生楔。早石炭世末期嫩江洋闭合,兴安增生地体与松嫩地块碰撞拼贴并发生强烈挤压造山,两侧增生楔在NW-SE方向汇聚应力驱使下呈花状仰冲隆起,伴随斜向走滑形成早期高角度叶理与线理。造山晚期,兴安增生地体与松嫩地块之间发生显著的左行走滑剪切作用,形成了NE-SW走向的低角度矿物拉伸线理。嫩江洋闭合相关构造的解析表明其具有双向俯冲的特征。     

阿拉善地块晚奥陶世—石炭纪的构造演化历史——来自北大山地区多期岩浆-变质-变形事件的约束

阿拉善地块西部的北大山地区识别出两期韧性变形构造,早期的韧性变形以从南(南东)向北(北西)逆冲为特征,晚期的韧性变形以近东西向左行剪切为特征。利用LA-ICP-MS锆石U-Pb测年方法,在记录早期韧性变形的片麻岩中获得锆石的变质年龄为422±1 Ma,代表晚志留世变质事件;在记录晚期韧性变形的2件二长花岗岩中获得锆石结晶年龄分别为326.2±1.2 Ma和323.8±2.6 Ma,代表早石炭世岩浆活动。结合前人研究成果,发现阿拉善地块西部北大山地区的两期韧性变形特征、变形时代与阿拉善地块东部巴彦乌拉山-狼山地区相似,同时阿拉善地块东、西部晚奥陶世-石炭纪多期岩浆活动的岩石类型、期次、地化及Nd同位素等特征也非常相似。以上特征表明,阿拉善地块东、西部经历了相同的构造演化历史,形成一条发育在早前寒武纪变质基底之上、呈近东西向弧形展布的晚奥陶世-石炭纪构造-岩浆岩带(西起桃花拉山,经北大山、诺尔公-巴彦乌拉山,东到狼山),其成因与古亚洲洋的俯冲造山事件密切相关。     

祁连山北阿拉善地体特征及其大地构造演化

祁连山北阿拉善地块在大地构造位置上处于中亚造山带、塔里木板块、祁连山-秦岭造山带和华北板块之间.阿拉善地体在太古代-元古代作为一个相对独立的小地体发育, 其结晶基底岩性与塔里木板块、华北板块存在一定程度差异.受加里东构造运动影响, 板块与地体表现为南聚北散特点; 在中奥陶世早期阿拉善地体与华北板块拼为一体, 进入板块整体演化阶段.中海西构造运动期, 北部早二叠世古亚洲洋关闭, 发育新增地壳, 形成北缘沟弧盆体系; 晚海西构造运动期, 阿拉善地体向南俯冲, 祁连山洋关闭, 地壳增生, 阿拉善地体与塔里木板块、华北板块焊接在一起.新特提斯构造运动对其影响巨大, 南缘表现为"左旋"走滑, 北缘表现为"右旋"走滑, 古生代所形成构造带均受到新生代北东向构造的强烈改造.阿拉善地体频繁的构造运动, 致使其南北部相对稳定的燕山期所形成的煤系中小盆地群(阿拉善-银额盆地群、北山盆地群、河西走廊盆地群、祁连山东部盆地群、祁连山西部盆地群、阿尔金盆地群、柴达木周缘盆地群), 也相应发生快速沉降与快速抬升过程, 后期均遭受强烈改造与破坏, 不仅造就烃源岩欠发育, 就是造成储集层致密, 总体不利于油气的生成、运移、聚集成藏, 油气勘探前景欠佳.     

西天山查岗诺尔矿区构造变形研究:对阿吾拉勒成矿带构造控矿模式的启示

阿吾拉勒成矿带是西天山重要成矿带之一,经历了多期构造作用,并伴生多期成矿作用。本文对成矿带内查岗诺尔矿区及邻区构造变形特征以及变形序列精细解析,探讨构造变形对铁矿的成矿作用以及后期改造作用的影响,为西天山地区铁矿床成因和找矿方向提供新启示。野外构造观察发现,研究区断裂构造主要分为NW-NWW向高角度韧性-韧脆性走滑断层及逆冲推覆断层,以近EW向、近SN向为主的高角度共轭脆(韧)性走滑断层和近SN向脆性右行走滑断层。年代学研究表明,断层分别形成于燕山晚期-喜马拉雅早期、喜马拉雅中期和喜马拉雅晚期,均为成矿期-成矿期后的构造记录。早期高角度韧性-韧脆性走滑断层是区域性控矿构造,而逆冲推覆断层是矿区主导控制性构造;中期共轭脆(韧)性走滑断层对矿体具有较为强烈的破坏和改造作用;晚期脆性右行走滑断层对矿体影响较小。查岗诺尔和智博矿区的断裂构造主要表现为对矿体的破坏和改造作用,而在松湖和塔尔塔格矿区,韧性-韧脆性剪切带是主要的控矿构造。主矿脉与构造密切伴生,具体表现为与成矿作用密切相关的磁铁矿化、绿泥石绿帘石化、碳酸盐化等蚀变多沿构造裂隙发生。     

内蒙古狼山地区新生代断层活动特征：对正断层生长的限定

阿拉善地块东北缘的狼山地区新生代发育有3期构造,分别为中新世NW-SE向挤压形成的逆断层,NNE向挤压形成的左行走滑断层以及晚新生代NW-SE向伸展形成的高角度正断层。结合阿拉善地块东缘的新生代构造,认为狼山地区新生代断层的活动与青藏高原东北缘的逐步扩展、应力场逐渐调整有关。狼山山前正断层目前是一条贯通的断层,其演化基本符合恒定长度断层生长模型,断层中间部位滑动速率最大,向断层两侧逐渐递减。从不同方法得出的滑动速率来看,进入全新世以来,断层滑动速率有逐渐变小的趋势。结合阿拉善地块内部及东缘断层震源机制解以及断层的几何学、运动学特征,认为河套—吉兰泰盆地和银川盆地属于两个性质不同的伸展盆地,两者通过构造转换带相连,转换区内断层表现为右行走滑。转换区5级以上地震可能是受区域性NE-SW向挤压,近南北向右行断层活动的表现。     

北祁连南缘右行韧性走滑剪切带的同位素年代学及其地质意义

北祁连南缘右行韧性走滑剪切带位于祁连地块与北祁连俯冲碰撞杂岩带边界 ,长约 80 0km ,走向NWW SEE ,面理向北陡倾 ,中西部宽 5～ 6km ,东部由四条呈帚状撒开的强应变带组成。构造指向及向南东低角度倾伏的拉伸线理揭示出韧性剪切带的右行走滑和转换挤压性质。TIMS法测定的单颗粒锆石U Pb上交点年龄为 96 5～ 95 6Ma ,代表韧性剪切带原岩———基底变质岩的变质时代。糜棱岩中钾长石、黑云母单矿物40 Ar/ 3 9Ar同位素测年结果及与地层和岩浆活动的关系表明韧性剪切带形成于 4 4 0～ 380Ma。北祁连南缘右行韧性走滑剪切带是在祁连加里东造山带形成过程中 ,祁连地块与阿拉善地块间斜向碰撞诱发大规模转换挤压作用的产物。     

A Large-Scale Palaeozoic Dextral Ductile Strike-Slip Zone:the Aqqikkudug-Weiya Zone along the Northern Margin of the Central Tianshan Belt,Xinjiang,NW China

The nearly E-W-trending Aqqikkudug-Weiya zone, more than 1000 km long and about 30 km wide, is an important segment in the Central Asian tectonic framework. It is distributed along the northern margin of the Central Tianshan belt in Xinjiang, NW China and is composed of mylonitized Early Palaeozoic greywacke, volcanic rocks, ophiolitic blocks as a mélange complex, HP/LT-type bleuschist blocks and mylonitized Neoproterozoic schist, gneiss and orthogneiss. Nearly vertical mylonitic foliation and sub-horizontal stretching lineation define its strike-slip feature; various kinematic indicators, such as asymmetric folds, non-coaxial asymmetric macro- to micro-structures and C-axis fabrics of quartz grains of mylonites, suggest that it is a dextral strike-slip ductile shear zone oriented in a nearly E-W direction characterized by "flower" strusture with thrusting or extruding across the zone toward the two sides and upright folds with gently plunging hinges. The Aqqikkudug-Weiya zone experienced at least two stages of ductile shear tectonic evolution: Early Palaeozoic north vergent thrusting ductile shear and Late Carboniferous-Early Permian strike-slip deformation. The strike-slip ductile shear likely took place during Late Palaeozoic time, dated at 269(5 Ma by the40Ar/39Ar analysis on neo-muscovites. The strike-slip deformation was followed by the Hercynian violent S-type granitic magmatism. Geodynamical analysis suggests that the large-scale dextral strike-slip ductile shearing is likely the result of intracontinental adjustment deformation after the collision of the Siberian continental plate towards the northern margin of the Tarim continental plate during the Late Carboniferous. The Himalayan tectonism locally deformed the zone, marked by final uplift, brittle layer-slip and step-type thrust faults, transcurrent faults and E-W-elongated Mesozoic-Cenozoic basins.     

Sedimentary compared to tectonically-deformed serpentinites and tectonic serpentinite mélanges at outcrop to petrographic scales: Unambiguous and disputed examples from California

This paper compares features of unambiguous tectonic serpentinite mélanges (TSM) or serpentinite shear zones in the Coast Range ophiolite, Franciscan subduction complex, of coastal California and Sierra City Mélange of the northern Sierra Nevada of northeastern California with undisputed sedimentary serpentinite mélange (SSM) of the Great Valley Group (GVG) forearc basin deposits of coastal California, and with Franciscan serpentinite mélanges of disputed (sedimentary versus tectonic) origin. The GVG sedimentary serpentinite mélanges and disputed Franciscan serpentinite mélanges share strongly similar matrix textures and block-matrix relationships at scales from tens of meters or more to petrographic scale but differ significantly from serpentinite shear zones and TSM. This comparison suggests shared (non-diagnostic) and distinguishing features of TSM versus SSM. Internal bedding or foliation in blocks is oriented subparallel to mélange boundaries and matrix foliation for both TSM and SSM both may have strongly foliated matrix and both may feature localized shearing in matrix around block borders, especially if an SSM underwent significant post-depositional deformation. The same holds true for deformation and dismemberment of blocks, which is the block-forming and mixing mechanism in TSM but variably exhibited in SSM. In contrast only SSM have blocks or clasts whose internal foliation or bedding terminates abruptly along clast/block boundaries with a mismatch in mineralogy and/or lithology across such boundaries. Matrix foliation cuts blocks/clasts in TSM but not in SSM. SSM may show block/grain size grading but not TSM. SSM have exotic blocks and blocks may span a range of metamorphic grade, whereas TSM lack exotic blocks and blocks are isofacial.     

Microstructures of mylonites along the Karakoram Shear Zone,Tangste Valley,Pangong Mountains,Karakoram

The Karakoram Shear Zone is a northwest-southeast trending dextral ductile shear zone, which has affected the granitic and granodioritic bodies of the southern Asian Plate margin in three distinct episodes. The ductile shearing of the granitic bodies at Tangste and Darbuk has resulted in the development of mylonites with mylonitic foliation and stretching lineation. More intense deformation is noted in the Tangste granite grading up to orthomylonite, as compared to the Darbuk granite. Kinematic indicators include S-C foliation, synthetic C′ and C″ antithetic shear bands, Type A s-mantled porphyroclasts, oblique quartz foliation, micro-shears with bookshelf gliding, mineral fishes including Group 2 mica fishes, and Type 1 and 2a pull-apart microstructures, and exhibit strong dextral sense of ductile shearing towards southeast. The textural features of the minerals, especially that of quartz and feldspar, indicate temperature of mylonitisation ranging between 300 and 500°C in the upper greenschist facies, and appear to have been evolved during exhumation as a consequence of oblique strike-slip movements along the Karakoram shear zone.     

腾冲地块高地热异常区晚白垩世-始新世钾玄质强过铝花岗岩岩石地球化学、年代学特征及构造意义

腾冲地块高地热异常区清水左所营初糜棱岩化黑云母二长花岗岩岩体、新华黑石河热田强糜棱岩化黑云母二长花岗岩岩体、热海热田硫磺塘硅化碎裂正长花岗岩岩体变形变质、岩石地球化学及锆石年代学的研究表明,晚白垩世(73Ma)初糜棱岩化黑云母二长花岗岩岩体为高温钾玄质强过铝花岗岩,形成于活动大陆边缘火山弧-后碰撞转换或过渡构造环境,并经历强烈伸展变形作用,普遍发育早期近水平-低角度(30°)韧性伸展剪切糜棱面理,局部发育晚期高角度右旋走滑挤压韧性糜棱面理;始新世(48~46Ma)强糜棱岩化黑云母二长花岗岩岩体、硅化碎裂正长花岗岩岩体为中-高温钾玄质强过铝花岗岩,并具铝质A型花岗岩特征,形成于后碰撞-板内构造环境,以发育晚期高角度(70°~87°)右旋走滑挤压韧性糜棱面理为特征,其右旋走滑韧性剪切变形时代晚于始新世(48~46Ma)。晚白垩世-始新世钾玄质强过铝花岗岩的形成与俯冲-碰撞造山隆升后的伸展垮塌、拆沉地幔物质上涌玄武质岩浆底侵和地壳部分熔融作用密切相关。始新世-第四纪岩浆活动与高地热异常区(带)空间上密切伴生,新近纪晚期-第四纪构造活动主要表现为脆性走滑-拉张正断层和构造拉分断陷盆地的形成,构造断陷边界断裂与深部岩浆活动是导致腾冲地区高地热异常区(带)中-高温地热温泉沿走滑-拉张断裂带集中分布的主要原因。     

青海银石山地区巴颜喀拉前陆盆地构造变形特征及动力学机制

银石山地区巴颜喀拉前陆盆地自北而南可分为冬银山倒转褶皱带、丛崭山-张公山大型向斜、屏岭-银石山断褶带等3个变形特征迥异的构造单元。三叠纪末,巴颜喀拉板块北缘向北消减过程中具“双层汇聚”机制——硬度较大的基底板块仍沿其二叠纪末与昆仑地块间的俯冲分界面向北消减,相对较软的巴颜喀拉三叠系盖层则沿其底面薄弱面剥离,被动向昆仑地块之上仰冲,从而在单剪应力状态下在其北面形成北倒南倾的等斜褶皱(东部)或轴面南倾的斜歪褶皱(西部)。受昆仑地块南缘“东凸西凹”的古构造格局控制,巴颜喀拉板块在向北消减时东部具右旋走滑,使北东面巴颜喀拉山群褶皱枢纽呈北东东向,并导致北部及中部的构造变形具东强西弱的特点。盖层与基底问界面、巴颜喀拉山群三段与四段间界面等为两个主要滑脱剥离面。受其控制,在中部丛崭山-张公山一带形成大型向斜,而在南部屏岭-银石山地区则形成中小规模连续褶皱。     

Geodynamic setting and emplacement of mylonitic granitoids within the North Golpayegan shear zone,Iran

The metamorphic complex of the North Golpayegan is part of the Sanandaj-Sirjan Zone. There are at least three distinct stages of deformation in this complex. Throughout the first stage, Paleozoic and Mesozoic sedimentary rocks have experienced regional metamorphism during Late Jurassic tectonic events related to the subduction of the Neo-Tethys oceanic lithosphere under the Iranian microcontinent. During the second deformation stage in the Late Cretaceous-Paleocene, the rocks have been mylonitized. The third stage of deformation in the region has led to folding and faulting superimposed on previous structures, and to exhumation of the metamorphic complex. This stage has determined the current morphology and N70E strike of the complex. The mylonitic zones of the second stage of deformation have been formed along the dextral transpressional faults. During the third stage of deformation and exhumation of the metamorphic complex, the mylonitic zones have been uplifted to the surface. The granitoids in the metamorphic complex have been injected along the extensional shear fractures related to the dextral transpressional displacements. The granitoids have been transformed into mylonites within the synthetic or antithetic shear zones. These granitoids are recognized as syncollision type (CCG) and have been formed at the end of orogenic events synchronous to the collision between the Arabian and the Iranian plates at the Late Cretaceous-Paleocene.