Correlation Studies of Rare Earth Elements in Syntectonic Intrusions of Strike-Slip Stage along Southern Segment of Tan-Lu Fault Zone

Intrusions in the Zhangbaling uplift zone and the eastern margin of the Dabie orogenic belt belong to the syntectonic intrusions developed during the strike-slip stage in the southern segment of the Tan-Lu fault zone. However, characteristics of rare earth elements show that intrusions in the Zhangbaling uplift zone have the characteristics of mantle source type and those in the eastern margin of Dabie belt are the typical crust source type. Therefore, Au-deposits related to the intrusions in the Zhangbaling uplift zone are developed better than those in the eastern margin of the Dabieshan. The research results of the rare earth elements coincide with the studies of geophysics, tectonic setting and stable isotope. It is further indicated that the rare earth elements offer effective approach to tracing the material sources of magmatic rocks.

Excess and Radiogenic Argon in High-Pressure Mylonites of the Tan-Lu Fault Zone, Eastern China

Bulk separates of porphyroclastic phengite, neoformed phengite and their mixtures from the Tan-Lu HP mylonites overprinted on the Sulu UHP rocks were analyzed with the 40Ar/39Ar step heating method. Two samples of the neoformed phengite from ultramylonite give 40Ar/39Ar plateau ages of 209.9±1.8 Ma and 214.3±1.8 Ma, which are interpreted as representing cooling times of the TanLu sinistral faulting, and provide geochronological evidence for the syn-orogenic faulting of the Tan-Lu fault zone. The results show that the phengite formed during the retrograde eclogite-facies mylonitization was not contaminated with excess argon and can be used for dating the deformation. Argon closure in previous K-bearing minerals with excess argon under a retrograde HP dry condition is considered to be the reason for lack of excess argon incorporation in the neoformed phengite. Five porphyroclastic phengite samples yield 40Ar/39Ar plateau ages ranging from 666±12 Ma to 307.1±3.3 Ma, which are interpreted as being contaminated with excess argon. Two mixture samples with plateau ages of 239.4±2.1 Ma and 239.3±2.0 Ma show upward-convex age spectra caused by the mixture of older porphyroclastic phengite with excess argon incorporation and younger neoformed phengite without excess argon incorporation. It is demonstrated that excess argon introduced from the previous UHP metamorphism is still preserved in the pre-existing phengite after the Tan-Lu eclogite-facies mylonitization. The intense deformation under HT and HP conditions cannot erase excess argon in the previous phengite totally due to restricted fluid activities. These porphyroclastic phengite previously contaminated with excess argon cannot be used for dating the later HP deformation. This indicates that deformation under a HP dry condition does not play an important role in removing previous 40Are in phengite.

Rock Deformation,Component Migration and 18O/16O Variations during Mylonitization in the Southern Tan-Lu Fault Belt

This paper discusses the relationship between the volume loss, fluid flow and component variations in the ductile shear zone of the southern Tan-Lu fault belt. The results show that there is a large amount of fluids flowing through the shear zone during mylonitization, accompanied with the loss of volume of rocks and variations of elements and oxygen isotopes. The calculated temperature for mylonitization in different mylonites ranges from 446 to 484℃, corresponding to that of 475 to 500℃ for the wall rocks. The condition of differential stress during mylonization has been obtained between 99 and 210 MPa, whereas the differential stress in the wall rock gneiss is 70-78 MPa. The mylonites are enriched by factors of 1.32-1.87 in elements such as TiO2, P2O5, MnO, Y, Zr and V and depleted in SiO2, Na2O, K2O, Al203, Sr, Rb and light REEs compared to their protolith gneiss. The immobile element enrichments are attributed to enrichments in residual phases such as ilmentite, zircon, apatite and epidote in mylonites and are interpreted as due to volume losses from 15% to 60% in the ductile shear zone. The largest amount of SiO2 loss is 35.76 g/100 g in the ductile shear zone, which shows the fluid infiltration. Modeling calculated results of the fluid/rock ratio for the ductile shear zone range from 196 to 1192 by assuming different degrees of fluid saturation. Oxygen isotope changes of quartz and feldspar and the calculated fluid are corresponding to the variations of differential flow stress in the ductile shear zone. With increasing differential flow stress, the mylonites show a slight decrease of δ^18O in quartz, K-feldspar and fluid.

K-Ar dating of extensional fault gouge from the Yi-Shu segment of the Tan-Lu fault zone

Two grabens were developed in the Yi-Shu segment of the Tan-Lu fault zone (TLFZ) during its extensional activities, and are now confined by four major NNE-trending normal faults and filled with Cretaceous sediments. These faults were developed due to their reactivities, containing gouge and cutting the graben sediments. Detailed fieldwork demonstrates that the faults experienced sinistral transtensional moment related to regional NE-SW extension during the reactivity. X-ray diffraction (XRD) analysis of the finest gouge samples gives illite crystallinity values higher than 0.42°Δ2θ, indicating temperatures experienced by the gouge samples were less than 150°C. From the relation between K-Ar data and proportions of detrital illite in different size fractions of the gouge samples, we conclude that refaulting for the western boundary fault of the TLFZ, abbreviated to F4, took place at ca. 90 Ma and for the eastern boundary fault, abbreviated to F1, happened from 70 to 60 Ma. During the two phases of reactivity imposed by the same NE-SW extension, the TLFZ experienced uplifting and no sediments were deposited in the two grabens. It is suggested that the TLFZ experienced extension during the Late Cretaceous, which supports the inference that lithospheric thinning was still undergoing in the east of the North China Craton during the Late Cretaceous magmatic hiatus.

全球天然氢气勘探开发利用进展及中国的勘探前景

在全球能源脱碳背景下,天然氢气作为一种一次能源,因其零碳、可再生的优点而备受关注,但中国目前还未开展专门针对天然氢气的勘探工作。通过介绍全球已知高含量天然氢气(体积分数大于10%)气藏的主要形成地质环境及成因类型,系统总结了天然氢气富集的有利地质条件,并结合国外天然氢气的勘探开发现状,评价了中国天然氢气的勘探前景。研究结果表明:(1)全球高含量天然氢气主要发育于蛇绿岩带、裂谷和前寒武系富铁地层中,且以无机成因为主,富铁矿物的蛇纹石化过程是天然氢气最主要的成因来源,其次为地球深部脱气和水的辐解。(2)优质的氢源与良好的运移通道是氢气富集的前提,而盖层的封盖能力是天然氢气能否成藏的关键要素;天然氢气作为伴生气时,传统盖层对其具备封盖能力,但当其含量较高时,传统盖层可能难以形成有效封盖;裂谷环境、蛇绿岩发育区以及断裂发育的前寒武系富铁地层是富氢气藏的勘探有利区。(3)国外多个国家和地区已制定了天然氢气的勘探开发和利用计划,其中,马里已实现天然氢气的商业开采,美国、澳大利亚也已成功钻探天然氢气勘探井。(4)中国高含量氢气区与富氢地质条件高度匹配,天然氢气勘探前景良好,郯庐断裂带及周缘裂陷盆地区、阿尔金断裂带及两侧盆地区、三江构造带—龙门山断裂带及周缘盆地区的天然氢气勘探潜力较大;中国应尽快开展天然氢气普查工作,加强氢气成藏过程研究和潜力评价,并进行勘探技术、开采分离技术和储运技术的攻关,为天然氢气的大规模开发利用做好技术储备。

金湖凹陷基性岩捕获锆石年龄及其区域构造意义

郯庐断裂带的形成演化是中国东部中生代关键大地构造事件,该断裂带起源机制问题是了解华南与华北板块汇聚过程与方式的基本前提。本文利用郯庐断裂带东侧金湖凹陷内7个新生代基性岩样品394个点的LA-ICP-MS锆石U-Pb年代学数据,在分析岩浆活动时代基础上,利用捕获锆石年龄信息探讨了大别造山带的古生代演化及郯庐断裂带起源机制问题,为认识上述问题提供了一个全新的视角。研究表明,金湖凹陷的基性岩浆活动时代为古近纪早期(66.1~56.5 Ma),与围岩的沉积时代吻合;基性岩中的捕获锆石来自大别造山带,是印支期板块碰撞造山中楔入郯庐断裂带东侧华南板块的造山带物质,具有华南板块、北淮阳和华北板块的混杂岩石圈信息;捕获锆石中445 Ma(变质锆石)、290 Ma(岩浆锆石)及214 Ma(变质锆石)等峰值年龄信息指示古生代以来北淮阳构造带经历了与北秦岭构造带类似的弧—陆俯冲、碰撞历程,暗示秦岭造山带的二郎坪洋、商丹洋和勉略洋可延伸至大别造山带东端;年代学数据及构造分析支持郯庐断裂带起源于嵌入碰撞背景下的华南板片撕裂边界,其起源形式为陆—陆碰撞下的板块斜向汇聚边界。

郯庐断裂转换段新沂地裂缝成生机理及构造意义

新沂地区处于郯庐断裂带转换段的关键部位,自20世纪70年代以来在新沂地区共发现地裂缝灾害点28处。这些地裂缝以群发的形式发育在南马陵山以西、沂河—骆马湖以东的区域内,地裂灾害影响区面积达100 km^(2)。新沂地裂缝与地层结构、地震活动、地下水开采等因素有着千丝万缕的联系,对其研究形成了多种观点。利用实地调查与勘探手段,新近查明了新沂地裂缝的基本特征,它们具有走向一致性、纵向尖灭性、局部群发性等特点,且与邻近断裂(郯庐断裂带次级断裂F3)具有高度一致性,属于区域构造控制型地裂缝。以新沂地区地质构造为原型,构建了逆断层作用下地裂缝成生物理试验模型。试验结果表明,随着逆断层断距加大而依次呈剪裂段、离层段、弯裂段等发展过程。结合新沂地区“地堑地垒地堑”组合结构,新沂地裂缝的成因机制可概括为“跷跷板”构造模型,在构造应力、自重应力、地下水波动等作用下,下沉段受挤压,上升段因抬升而弯裂,从而形成地裂缝。研究新沂地区地裂缝,对揭示郯庐断裂带“北中南”段构造变化和“深浅表”部结构联系具有重要的指示意义。

Structural characteristics of the Tan-Lu fault zone in Cenozoic basins offshore the Bohai Sea

The Tan-Lu fault zone across the eastern margin of the Cenozoic basins offshore the Bohai Sea is a NNE-trending right-lateral strike-slip fault system developed in the Cenozoic basin cover. It cuts through NE-to NNE-striking major extensional faults that controlled the formation of Paleogene basins. Recent petroleum exploration indicates that Cenozoic structural activities of the Tan-Lu fault system have directly or indirectly affected oil and gas distribution offshore the Bohai Sea. As part of a deep fault zone the Tan-Lu fault zone has been activated since the Oligocene,and obviously affected the tectonic evolution of offshore Bohai basins since then. The formation of Paleogene rift basins offshore the Bohai Sea has utilized the pre-existing structural elements of the Tan-Lu fault zone that developed in the late Mesozoic.

Structural deformation and fault activity of the Tan-Lu Fault zone in the Bohai Sea since the late Pleistocene

The Tan-Lu Fault zone (TLFZ) is a significant fractural zone in eastern China and also a seismicity belt in North China. Based on total 4000-km-long shallow penetrated single seismic data with high-resolution, structural deformation and fault activity of the TLFZ in the Bohai Sea since the late Pleistocene are discussed in detail. The results show that the TLFZ with a discontinuous distribution and a general NNE-trending consists of 14 active subfaults with an NNE or NE strike in the Bohai Sea. Seismic data reveal that deformation zones along the subfaults in the central Bohai Sea and the Laizhou Bay are wider and more complex than those in the Liaodong Gulf. Related folds and lots of secondary normal faults which are characterized by nearly vertical fault planes and a same or reverse dip construct the fractural zone in the Laizhou Bay and the central Bohai Sea. Usually, micro sym-metrical grabens develop on the top of anticlines. In the Liaodong Gulf, subfault fractural zones usually consist of secondary normal faults with the same inclination or opposite inclination. Ages of seismic sequences and cutting relation between subfaults and seismic sequences suggest that the latest faulting age of the TLFZ is the end of the late Pleistocene in the Liaodong Gulf and the early Holocene in the Laizhou Bay and the central Bohai Sea. There is a good match between distribution of earthquakes and that of the subfaults in the Laizhou Bay and the central Bohai. Statistical result shows that total vertical offset of the TLFZ since the late Pleistocene ranges from 6 to 11 m. On the basis of offsets of the subfaults, the vertical slip rate is calculated and results show that average vertical slip rates in the central Bohai Sea are larger than those in the Liaodong Gulf and the Laizhou Bay. Slip rates more than 0.06 mm/a during 23-10 ka B.P. and 85-65 ka B.P. are larger than those in other stages. The TLFZ was mainly dominated by tensional normal component since the late Pleistocene. Synthesizing shallow deformation, activity and distribution of earthquakes, the TLFZ in the Bohai Sea can be divided into three segments: the Laizhou-Bay segment, the Bozhong segment, and the Liaodong-Gulf segment.

^(40)Ar/^(39)Ar geochronological constraints on syn-orogenic strike-slip movement of Tan-Lu fault zone

Two phases of sinistral strike-slip ductile shear belts occur on the eastern margin of the Dabie orogenic belt. A muscovite ^40Ar/^39Ar plateau age of 128 Ma was obtained from mylonite in the later ductile shear zone. Three muscovite samples separated from mylonites of 3 localities in the earlier ductile shear belts yield ^40Ar/^39Ar plateau ages of 192.5±0.7 Ma, 189.7±0.6 Ma and 188.7±0.7 Ma, respectively. They are interpreted as cooling ages of the earlier sinistral strike-slip deformation. It is suggested that left-lateral displacement of the Tan-Lu fault zone started in a late stage of the collision orogeny in the Dabie-Sulu orogenic belt between the North and South China plates. Therefore, the earlier Tan-Lu fault zone was syn-orogenic strike-slip tectonics. The fault zone was used again for sinistral displacement during tectonic activities of peri-Pacific regime in Early Cretaceous. It is proposed that the fault zone occurred as a transform fault during the orogenic process.

安徽巢湖地区早白垩世煌斑岩的形成年代、岩石成因及其地质意义

煌斑岩是一种典型的富含挥发分的超基性—中性岩,作为深部幔源岩石,能很好地反映地幔源区的地球化学属性,为探究地球的深部构造和岩浆过程提供了有利窗口。本文以巢湖地区东南部的闪斜煌斑岩为研究对象,在野外地质调查及岩相学研究的基础上,进行了磷灰石年代学、Sr-Nd同位素和全岩主量元素和微量元素分析,通过数据定量模拟,剖析了岩浆过程和地幔源区特征,探讨了其形成构造背景。结果表明,巢湖闪斜煌斑岩(22CH09、22CH14和22CH17)磷灰石LA-ICP-MS ^(206)Pb/^(238)U加权平均年龄分别为119±18 Ma、116.4±7.5 Ma和114±13 Ma,均形成于早白垩世。巢湖闪斜煌斑岩SiO2含量为39.80%~43.52%,Mg^(#)值为63~70,K_(2)O的含量为1.60%~2.46%,为碱性煌斑岩,且相对富集大离子亲石元素(LILEs,如Ba、K、Cs),亏损高场强元素(HFSEs,如Nb、Ta、Zr、Hf),类似于弧相关的岩浆岩。巢湖闪斜煌斑岩具有低的(Hf/Sm)_(N)和(Ta/La)_(N)比值(分别为0.60~0.67和0.27~0.38),指示其源区经历了俯冲板片流体的交代作用;其高的Zn/Fe(0.0012~0.0015)及Fe/Mn值(65.54~84.49)表明其源区主要为辉石岩。数值定量模拟表明,巢湖闪斜煌斑岩可能源于石榴辉石岩小比例部分熔融(<4%),原生岩浆经历了约3%的橄榄石分离结晶作用。煌斑岩磷灰石原位^(87)Sr/^(86)Sr(t)值为0.7069~0.7078,ε_(Nd)(t)值为−9.5~−6.8,与长江中下游带同期基性岩的Sr-Nd同位素组成相似,表明二者起源于同位素组成相似的富集岩石圈地幔。巢湖地区中生代岩石圈地幔与长江中下游带具有较高的亲缘性,长江中下游带与郯庐断裂带南段岩石圈地幔的分界可能介于巢湖闪斜煌斑岩与肥东杂岩之间。结合区域岩浆活动特点,本文认为巢湖闪斜煌斑岩为古太平洋俯冲板片后撤的产物,形成于弧后伸展构造背景。

联合多源数据反演郯庐断裂带南段地壳三维速度结构

郯庐断裂带南段位于不同块体交汇区,高分辨率的地壳速度结构有助于理解该地区的构造特征及成因.本文基于多源数据,利用2015年安徽实验中气枪的体波和高频面波,2008—2018年区域地震体波信号以及背景噪声面波频散等资料,将不同来源、不同周期的面波频散数据和体波走时进行联合反演,获取了郯庐断裂带南段的高精度地壳速度结构.研究结果表明:(1)加入面波信息进行联合反演后,获取的P波和S波速度模型的分辨能力较单一体波数据反演在中下地壳均有显著提升.(2)郯庐断裂带是控制区域异常的主要因素,两侧具有明显的速度差异.地震主要发生在断层附近,集中分布于高低速交界区.(3)秦岭—大别造山带下方5~10 km深度存在明显的高速异常体,对应于超高压变质岩,是大陆深俯冲经历超高压变质作用后折返上升到中上地壳形成的.(4)长江中下游成矿带的矿集区呈现高的P波和S波速度值,可能是陆内俯冲、岩石圈拆沉、幔源岩浆底侵和一系列成矿作用共同造就的.

郯庐断裂带南段早白垩世镁铁质岩墙成因及其地质意义

地壳再循环物质交代岩石圈地幔形成不均质的地幔源区,其衍生的镁铁质岩浆岩为揭示地幔演化及壳-幔相互作用提供了重要信息。本文对郯庐断裂带内张八岭隆起南段肥东地区镁铁质岩中的锆石进行LA-ICP-MS定年,获得年龄集中在127~122 Ma。镁铁质岩样品中SiO_(2)含量为51.33%~54.01%,Mg#值为52.6~70.0,并具有富钠、富碱(σ=2.46~4.22)的特征,属于亚碱性和高钾钙碱性系列。镁铁质岩样品均富集大离子亲石元素(LILEs,如Ba、Pb、K),相对亏损高场强元素(HFSEs,包括Nb、Ta、Ti等),表现为弧型地球化学特征。锆石Hf-O同位素研究获得极负的εHf(t)值(-23.4~-21.2)和略高的δ18O值(5.49‰~6.01‰),与新元古代斜长角闪岩同位素组成显示出一致的演化趋势和相似的分布特征。因此,早白垩世镁铁质岩墙富集的同位素特征主要继承于新元古代(~800 Ma)岩石圈地幔;在郯庐断裂带伸展背景下,由古老岩石圈地幔发生减压熔融形成。

郯庐断裂带中南段地壳厚度与泊松比研究

郯庐断裂带中南段与西太平洋板块俯冲以及华北克拉通破坏密切相关,研究其深部结构对于了解郯庐断裂带构造演化过程、强震的孕震机制具有重要意义.本文利用密集台阵波形资料,采用接收函数H-κ叠加方法获得郯庐断裂带中南段的地壳厚度和泊松比.结果显示,郯庐断裂带中南段的地壳厚度分布以庐江和新沂为分段点呈现出与地质构造相关的南北向分段特征:南段的断裂带西侧的地壳厚度比东侧厚约5 km,中段的断裂带两侧厚度差异减小至约3 km,而北段则表现为断裂带下方隆起特征.郯庐断裂带沿线的地壳泊松比较高,推测是地幔物质的热侵蚀和化学侵蚀所致.根据艾里地壳均衡理论,南段地壳厚度与地表高程相关,基本符合艾里地壳均衡模型;而中段两侧地表高程基本相同,两侧地壳厚度差异表明不符合艾里地壳均衡模型,可能与断裂带西侧的华北克拉通岩石圈比东侧扬子克拉通岩石圈具有更高密度有关,高密度岩石圈产生向下“拖拽力”导致莫霍面相对理论值偏深;北段的莫霍面也偏深,与中段断裂带西侧情况类似,该区域基本位于华北克拉通块体.在郯城地震破裂范围内,存在莫霍面的不平滑过渡、活动块体的边界带以及断裂的分叉与交汇这三类结构特征.在上述结构特征的区域应力更集中,从而孕育产生了1668年郯城8.5级地震.

重力异常反映的郯庐带中南段构造边界与应力场

为解决传统基于重力场数据一阶导数定义的总水平导数和解析信号振幅存在无法均衡深浅异常振幅的问题,应用重力全张量梯度数据,提出改进的倾斜导数地质体边界识别方法NTD_(M)。经模型验证,NTD_(M)在收敛性、抑噪性和边界识别精度方面均有提升。利用NTD_(M)将郯庐带中南段及邻区划分为14个边界较为清晰的构造单元,借助垂线偏差数据对郯庐带中南段的构造应力场和壳幔密度差进行反演。结果显示,二者在水平方向上存在显著差异,在空间上显著相关,构造应力最大差异值约为16 MPa,壳幔密度差约为0.2 g/cm^(3),构造应力等值线密集处与构造单元划分的边界以及地震分布情况对应较好。郯庐带中段最大主应力方向为NEE-EW,南段主应力方向以EW-NWW为主,总体呈EW向,与震源机制解、地应力测量和GPS反演结果具有较好的一致性。

郯庐断裂带赤山段全新世新活动的特征

文中在野外开挖探槽及年龄样品测试的基础上,对郯庐断裂带赤山段全新世的新活动特征进行了详细讨论。在泗县赤山镇徐井村附近开挖了2个地质探槽(XJ1、XJ2),其中XJ1探槽揭露了10个地层单元,从老到新依次为U_(1)—U_(10);发现3条断层,由东向西依次为F_(1)、F_(2)和F_(3);识别出3次古地震事件,由老到新依次为E_(1)、E_(2)和E_(3)。事件E_(1)和E_(2)分别为F_(1)和F_(2)的逆冲活动,事件E_(3)为F_(2)逆走滑和F_(3)正走滑共同活动的结果。前2次古地震事件E_(1)、E_(2)发生于中更新世—晚更新世晚期之间,后一次事件E_(3)代表最新一次古地震活动,发生于地层U9沉积以后,在该层上部采集的泥炭样品的测定年代为11.10~10.75ka BP,说明郯庐断裂带赤山段在全新世早期以后仍有活动。

郯庐断裂带流体中氦的来源、空间分布及地质意义

郯庐断裂带是中国东部规模最大、构造运动强烈以及地震频发的活动断裂带,其深部结构与现今活动状态引人注目。对郯庐断裂带郯城段和庐江段温泉与深井地下水逸出和溶解气体进行He同位素组成和气体组分分析结果显示,郯庐断裂带流体 ^(3)He/^(4)He测试值为大气参考值(记作1 Ra)的0.15~1.15倍。郯城段样品的 ^(3)He/^(4)He和4He/20Ne值分别为0.96~1.15 Ra和0.24~0.30,显示有大气和地下水氚衰变对He来源的贡献。庐江段样品的 ^(3)He/^(4)He空气校正值和4He/20Ne值分别为0.15~0.79 Ra和0.28~272,扣除大气贡献后He主要来源于地壳放射性元素衰变(90.4%~98.4%),局部受到地幔脱气作用的显著影响(幔源He占比最高为9.6%)。在空间上,庐江段幔源He占比呈现出随采样点远离断裂带而逐渐减小的趋势,反映了幔源流体运移过程中经历的稀释效应。幔源He空间分布与地震P波速度图像对比结果表明,庐江段深源流体可能受到地幔部分熔融作用的影响。全球典型走滑断裂带的流体 ^(3)He/^(4)He值和走滑速率之间呈正相关关系(R^(2)=0.8),表明断裂带活动性及其应力状态对幔源流体释放具有一定的控制作用。

郯庐断裂带中段沿线地裂缝发育特征与影响因素

郯庐断裂带作为一条现今仍在活动的巨型走滑断裂带,对沿线区域构造、地震活动、地裂缝灾害产生重要影响。基于文献调查和对比研究,总结郯庐断裂带中段沿线地裂缝的发育情况及空间分布规律,分析郯庐断裂带对沿线地裂缝的控制作用。研究表明,郯庐断裂带中段沿线地裂缝在地表具有北多南少、近密远疏、北强南弱、走向性明显等分布规律,其形成和显现受区域构造运动、断层蠕动、地震作用和人类活动、外动力作用等众多因素的影响。研究成果对郯庐断裂带中段沿线地裂缝灾害的防治具有一定指导意义。

郯庐断裂带山东段的中新生代构造演化特征

本文在总结郯庐断裂带的最新研究成果的基础上,对郯庐断裂带山东段深部构造特征、运动学特征和内部结构特征进行了分析,并对郯庐断裂带山东段的中新生代构造演化过程进行了研究。在华南华北碰撞造山时期,郯庐断裂带山东段发生了显著的左旋走滑剪切变形。郯庐断裂带山东段在晚侏罗至早始新世(50Ma前)的左旋走滑直接受控于古太平洋板块向东亚大陆的俯冲,板块俯冲边界的应力直接传递到郯庐断裂带导致其发生走滑运动;早白垩世中期至古近纪,郯庐断裂带山东段内部及两侧盆地的伸展则受控于深部岩石圈减薄、地幔底辟导致的裂陷作用。

郯庐断裂带中段第四纪活动及其分段特征

郯庐断裂带是中国东部一条岩石圈尺度的构造不连续带。位于江苏和山东境内的郯庐断裂带中段 ,在新构造运动时期强烈右旋走滑复活 ,形成地貌形迹显著的走滑活动断裂带。笔者在断层活动形迹的野外调查和观测的基础上 ,结合TM遥感影象特征解译和地震震源机制解资料 ,分析了郯庐断裂中段第四纪活动的分段行为特征。位于嘉山 潍坊之间的郯庐断裂带中段可以进一步划分为 3段 ,北段安丘 茅埠亚段 ,中段汪湖 宿迁亚段 ,南段宿迁 嘉山亚段 ,这三段可能分别是独立的地震破裂段。观测表明 ,新构造变形主要集中在宿迁以北的中、北段 ,是历史强震的发生段 ,而南段变形相对较弱。嘉山以南安徽境内郯庐断裂新构造变形更弱。郯庐断裂带新构造走滑变形的走向分段行为是华北地区不同块体新构造运动位移调节的结果。