【作者】 万乐；

【导师】 曾佐勋；

【作者基本信息】 中国地质大学 ， 地质学， 2020， 博士

【摘要】 位于华北克拉通北缘东段的辽宁台里地区岩石天然流变极为丰富,是研究岩石天然理想场所。台里地区以花岗质岩石为主体,锆石U-Pb结果显示整个台里地区岩浆活动分为四期:太古代后期（～2.5 Ga）的花岗质片麻岩和（角闪）黑云斜长片麻岩;三叠世后期（～222 Ma）的斑状（眼球状）花岗质片麻岩,长英质变粒岩和花岗质细晶岩;晚侏罗世（～156 Ma）的黑云母二长花岗岩和部分的基性脉体;以及早白垩世（～140 Ma）的中-基性岩脉。台里剪切带以NE-SW左行一般剪切为主,带内地质体变形极为发育,形成不同类型的剪切变形标志,包括:剪切面理,石香肠构造、旋转碎斑等。区域变形可以分为三个主要时期,第一期变形阶段为新太古代-古元古代时期的花岗质片麻岩和（角闪）黑云斜长片麻岩,片麻理极为发育,产状近直立,主要以NE展布。这一阶段的变形主要是流动性为主,无根褶皱和熔体较为发育,岩石变质主要是以角闪岩相为主,表现出典型的岩浆深熔作用特征。根据早期变形的形态特征推测这一时期花岗质岩石的变形深度在25–21 km范围内。Nd-Hf同位素结果显示这些古老锆石普遍表现出较高的?_Hf（t）值（-4.4至+6.5）,对应的二阶段年龄在T_DM2=3.0–2.6 Ga,与球粒陨石或亏损地幔分异物质具有一致性,表明其源区推幔源物质减压脱水有关,后期受到新生地壳物质的影响,在地球化学方面体现了一个“壳源”假象。三叠世中后期（～220 Ma）形成了区内的斑状花岗岩,长英质变粒岩和花岗质细晶岩。岩石发生了强烈的糜棱岩化,压扁作用和剪切作用极为强烈和普遍,其中的斑状花岗质片麻岩表现出强烈的左行剪切特征,反映其变形深度在16–12 km,变形为中-低温压（450–550°C）,属于绿片岩相变质条件,这为第二阶段变形。这一阶段的岩石产出形态不固定,局部以NE-SW和NEE向侵入早期花岗质岩石中;同时期稍晚形成的脉体产出形态不均一,基本可以分为近南北、北东和北西向,以NEE向为主。地球化学证据显示斑状花岗质片麻岩和同期的长英质变粒岩均表现出高K₂O/Na₂O比值（>0.5）,高Sr/Y,高（La/Yb）_N特征,表现出典型的埃达克质岩特征,推测这一时期的岩石形成深度范围在（43–36 km）,与印支构造运动有关。同期稍晚的～214 Ma花岗质脉体则没有表现类似特征。Nd-Hf同位素结果显示这一时期埃达克质岩石?_Hf（t）在-14.1和-22.7之间,对应的两阶段年龄T_DM2=2.1–1.8 Ga,?_Nd（t）在-12.8和-13.1之间,T_DM2年龄为～2.0 Ga,表明台里三叠世的埃达克质岩/斑状花岗质片麻岩与古老下地壳的熔融有关。进入中生代中后期（～150 Ma）,形成了区内南、北两侧的黑云母二长花岗岩,岩石表现出明显的脆-韧性变形,以脆性变形为主。劈理、断层和节理在此阶段较为发育,对应的是第三阶段变形,其变形深度<8 km;Nd-Hf同位素结果表明ε_Hf（t）值为-29.36和-38.08,两阶段年龄T_DM2=3.0–2.5 Ga,与古老地壳物质部分熔融有关。早白垩世时期的基性脉体发育,基本没有受到强烈的变形作用,推测这一时期的变形深度在0–3 km。整个研究区从北向南,地质体产出形态由北东向近东西向过渡,表明区域受力状态从北西向近南北向发生了改变。矿物位错密度法测得台里南部晚侏罗世的黑云母二长花岗岩应力差值在51.2 Mpa,大于北部区域的压差应力为35–38 Mpa,表现出差异性变形;整个台里地区中生代中后期的变形岩石应力差值大于其北部的同时期医巫闾山剪切带变形岩石（9.6–13.9 Mpa）,表明在侏罗纪晚期,华北板块东缘的变形由南向北呈现出由强向弱的变化趋势,反映地壳的变形由深向浅部转换,区域差异性构造应力向北逐渐减弱。台里地区花岗质岩石K值（K=[ln（X/Y）/ln（Y/Z）]）)在大部分在1.26–3.25之间,指示台里的剪切应变属于一般拉伸。早期的花岗质片麻岩和晚期的黑云母二长花岗岩W_k值普遍具有较高>0.71;中生代早期的斑状花岗质片麻岩W_k集中在0.21–0.66之间;早期岩石受到简单剪切作用较强,中后期岩石则受到纯剪切作用为主,总体上也是表现出一般剪切作用。花岗质片麻岩和斑状花岗质片麻岩之间的黏度比为3.5–4.67;而长英质脉体和（角闪）黑云斜长片麻岩黏度比在2.8–6。从花岗质片麻岩-斑状花岗质片麻岩-长英质变粒岩强度依次降低;斑状花岗质片麻岩强度大于早期的（角闪）黑云斜长片麻岩。根据长英质脉体在围岩中形成的石香肠构造特征,可以判定细晶岩和含石榴子石细晶岩脉能干性强于花岗质片麻岩和（角闪）黑云斜长片麻岩。矿物的粒径大小和成分差异是导致能干性差异的重要因素,粒径越大,黏度越高;不同矿物含量是影响流变行为另一个重要因素,长石含量越高,云母含量越低,岩石黏度越高。华北板块东缘岩石圈从新太古代到中生代早期普遍发生了抬升,导致了岩石圈厚度的减薄（减薄程度达到～9 km）,对应着地质体的变形从早期的无根褶皱和熔体相向中-浅部的糜棱岩化和剪切作用过渡;三叠世埃达克质岩反映这一时期的岩石圈厚度的增加,可能与北部的古亚洲洋俯冲作用有关。中生代晚期的构造活动主要受到太平洋构造域控制,导致了岩石圈厚度的破坏和减薄,以及脆-韧性变形发生。前侏罗世的构造活动则主要受到古亚洲洋和扬子板块碰撞影响,多期次构造运动形成华北板块东部复杂的变形样式组合,这种过程一直持续到中生代后期。更多还原

【Abstract】 Our study area,Taili,where belong to the Liaoning Province,located in the eastern part of the north margin of the North China Craton（NCC）.It is an ideal place to study the natural rheology of rocks due to the intensive and extensive deformation.The Taili area is dominated by granitic rocks.According to the detailed U-Pb zircon age,four stages of the magmatic activity occurred in the area,including the late Archean granitic gneiss（～2.5 Ga）and（hornblende）biotite plagioclase gneiss,the late Triassic（～222Ma）porphyritic granitic gneiss,felsic leptynite and granitic aplite,the late Jurassic（～156 Ma）biotite monzogranite and some mafic veins,and the early cretaceous（～140Ma）intermediate-mafic dykes.In general,the Taili is characterized by NE-SW sinistral shear with intensive deformation behaviors as indicated by a series of shear deformation symbols,such as S-C fabrics,boundinage structures,rotated feldspar porphyroclasts etc.Three stages of deformation can be subdivided.The first stage is featured by a steep,generally NE striking granitic gneiss and（hornblende）biotite plagioclase gneiss.Rootless fold and melt facies are well-developed pointing to the anatexis magmatism within amphibolite facies conditions,reflecting that the deformation formed at the depth of～25–21 km.The early zircon have high?_Hf（t）values ranging from-4.4 to+6.5,with corresponding T_DM2=3.0–2.6 Ga,possibly indicate their derivation from the mantle materials associated with extensive dehydration,and subsequently influenced by the young crustal which account for the a"shell source"in geochemical signatures.The second stage of deformation limit to the central part,manifested by the Triassic porphyritic granitic gneiss,felsic leptynite and granitic aplite.Ductile shear and mylonites developed,concomitant with greenschist facie metamorphism（450–550°C）.The porphyritic granitic gneiss display typical sinistral shear,indicating the deformation formed at the depth of～16–12 km.Variable deformation patterns in these granitic rocks with a clear transition from NE to NEE-trending.Contemporaneous felsic veins show uniform deformation behaviors with variable morphology features,which can be basically divided into the NS,NE and NW directions.The Triassic porphyritic granitic gneiss and felsic leptynite show typical adakitic signature as evidenced by the high K₂O/Na₂O values（>0.5）,Sr/Y and（La/Yb）_N,reflecting the thickening lithosphere relate to the Indosinian orogenesis in region.These Triassic adakitic rocks have low?_Hf（t）values of-14.1 and-22.7,with corresponding T_DM2=2.1–1.8 Ga.Their?_Nd（t）range between-12.8 and-13.1,with T_DM2of～2.0 Ga,indicating that the Mesozoic granitic rocks are affected by a addition of ancient lower crustal materials.The last stage deformation mainly occurred in the late Jurassic biotite monzogranite,which was dominated by brittle and ductile deformation.Faults,joints and cleavage are well developed,reflecting the deformation formed at the depth of<8km.The biotite monzogranite have low?_Hf（t）values of-29.36 and-38.08,indicating the ancient crustal involved into the magmatism.Mafic veins are developed in the region with insignificant deformation,pointing to the deformation occurred at the depth of 0–3 km.Overall,the tectonic deformation was obviously stronger than that in the south.From north to south,the compression direction changed from NW to nearly NS.We obtain the stress difference（51.2 Mpa）of the quartz in biotite monzogranite by using dislocation density method,which is larger than that in the north（35–38Mpa）.All the results in Taili are larger than the contemporaneous deformed rocks in the Yiwulushan area（North of the Taili）（9.6–13.9 Mpa）,indicating a deformation trend from strong to the weak from the south to north along the eastern margin of NCC.The Flinn values（K=[ln（X/Y）/ln（Y/Z）]）)of the granitic rocks ranging from 1.26to 3.25,pointing to the general shear.The granitic gneiss and biotite monzogranite have high vorticity>0.71,and 0.21–0.66 of the porphyritic granitic gneiss,reflecting the early is dominated by the simple shear and pure shear for the later.Viscosity ratios（ηa/ηb）between the granitic gneiss and porphyritic granitic gneiss are 3.5–4.67,and felsic veins and（hornblende）biotite plagioclase gneiss are 2.8–6.Combined with detailed field observations,the porphyritic granitic gneiss is stronger than that of early（hornblende）biotite plagioclase gneiss,granitic aplite and garnet-bearing granitic aplite show stronger competency than that of granitic gneiss and（hornblende）biotite plagioclase gneiss.The grain size is the dominant factor controlling the rheology,i.e.,the larger the particle size,the higher the rock viscosity is.The proportion of the mineral content is another dominant factor;the higher the feldspar content,the lower the mica content,the higher the rock viscosity is.From Archean to early Mesozoic,the lithosphere under the eastern NCC uplifted nearly 9 km,associated with the deformation pattern change from the early rootless fold and melt facies to the ductile shear and mylonitic.The exposed Triassic adakitic rocks reflect the growing of lithospheric thickness during this period,relating to the subduction of the Paleo-Asian ocean in the north of NCC.The late Mesozoic tectonic framework in the region is mainly controlled by the Pacific tectonic domain,accompanied by a significant of lithospheric thinning and decratonization,which account for a series of brittle deformation.The pre-Jurassic magma activity was dominated influenced by the collision of the Paleo-Asian ocean and the Yangtze plate.The multi-stage tectonic movement resulted in the complex deformation assemblages in the eastern part of the NCC,which lasted until the late Mesozoic.更多还原