Tensile Fractures and in situ Stress Measurement Data Constraints on Cretaceous-Present Tectonic Stress Field Evolution of the Tanlu Fault Zone in Shandong Province,North China Craton

Tectonic stress fields are the key drivers of tectonic events and the evolution of regional structures.The tectonic stress field evolution of the Tanlu fault zone in Shandong Province,located in the east of the North China Craton(NCC),may have preserved records of the NCC’s tectonic history.Borehole television survey and hydraulic fracturing were conducted to analyze the paleo and present tectonic stress fields.Three groups of tensile fractures were identified via borehole television,their azimuths being NNW-SSE,NW-SE and NE-SW,representing multiple stages of tectonic events.Hydraulic fracturing data indicates that the study region is experiencing NEE-SWW-oriented compression and nearly-N-Soriented extension,in accordance with strike-slip and compression.Since the Cretaceous,the orientation of the extensional stress has evolved counterclockwise and sequentially from nearly-NW-SE-oriented to NE-SW-oriented and even nearly N-S-oriented,the stress state having transitioned from strike-slip-extension to strike-slip-compression,in association with the rotating and oblique subduction of the Pacific Plate beneath the NCC,with the participation of the Indian Plate.

Seismo-tectonic divisions of strong earthquakes with M_s≥7.0 and their tectonic geomorphology along Xianshuihe-Xiaojiang fault zone

Seismo-tectonic areas of historical strong earthquakes with MS(7 along Xianshuihe-Xiaojiang fault zone are divided, and their individual fault-pattern and tectonic geomorphology are analyzed. Those strong-earthquake areas are located in some special parts of the fault zone, where the major branch-faults of the fault zone form left stepping, parallel, and fork-like patterns. In the strong-earthquake areas structurally complicated basins are developed, such as pull-apart basins in fork-like area, in double stepping area, and in stepping and fork-like areas.

Seismic and Tectonic Correspondence of Major Earthquake Regions in Southern Ghana with Mid-Atlantic Transform-Fracture Zones

For four centuries now, southern Ghana has been known to be seismically active, and there is no clear geological explanation for the cause of the seismicity. By evaluating new field data and information with re-interpreted historical earthquake data of southern Ghana, the nature of the seismicity of southern Ghana has been elucidated. The mutual connection between the earthquake epicentres and the remote causes by Mid-Atlantic transform faults and fracture zones has been established. The seismic regions of southern Ghana have been linked separately to tectonic faults and activities of the St. Paul’s and Romanche transform-fracture zone systems offshore in the Gulf of Guinea to onshore. It is concluded that the seismicity of southern Ghana is due to tectonic activities of the St. Paul’s and Romanche transform-fracture systems. The Accra region earthquakes originate from reactivation of faults in the Romanche transform-fracture zone, and propagate onshore through Accra and environs. The Axim region earthquakes come from reactivated faults linked to the St Paul’s fracture zone, which go through southern Cote D’Ivoire to Ghana. Seismotectonic movements along the St Paul’s transform and fracture zones have quieted since 1879. But movement along the Romanche Transform fault and Fracture zone is active, causing ongoing seismicity of southern Ghana.

Tectonic Control of the Theistareykir Geothermal Field by Rift and Transform Zones in North Iceland:A Multidisciplinary Approach

This paper presents a multidisciplinary structural analysis of a 165 km2 area in the Northern Rift Zone and the Tjörnes Fracture Zone of Iceland, and unravels the tectonic control of the Theistareykir geothermal field and its surroundings. About 10729 fracture segments (faults, open fractures, joints) are identified in the upper Tertiary to Holocene igneous series. The segments were extracted from aerial images and hillshade, and then analyzed in terms of number of sets, geometry, motions, frequency, and relative age. The correlation with surface geothermal manifestations, resistivity, earthquakes, and occasional well data reveals the critical regional and local fractures at the surface, reservoir level and greater depth. The main conclusions of this study are: 1) The structural pattern consists of N-S rift-parallel extensional fractures and the Riedel shears of the transform zone striking NNE, ENE, E-W, WNW and NW, which compartmentalize together the blocks at any scale. 2) The en échelon segmentation shows strike and oblique slips on the Riedel shears, with a dextral component on the WNW and NW planes and a sinistral component on the NNE to ENE faults. 3) Fractures form under the influence of the transform mechanism and the effect of rifting becomes significant only with time. 4) The WNW dextral oblique-slip Stórihver Fault of the transform zone has a horsetail splay that extends eastwards into the geothermal field. There, this structure, along with few NW, ENE, NNE and N-S fractures, controls the alteration, alignment of fumaroles, emanating deep gases. These fractures also rupture during natural or induced earthquakes. 5) The resistivity anomalies present en échelon geometries controlled by the six fracture sets. These anomalies display clockwise and anticlockwise rotations within the upper 8 km crustal depth, but at 8 km depth, only three sets (the N-S rift structures, and the E-W and the NW Riedel shears) are present at the rift and transform plate boundaries. Results of this study are relevant to resource exploration in other complex extensional contexts where rift and transform interact.ööö

Tectonic Control of the Reykjanes Geothermal Field in the Oblique Rift of SW Iceland:From Regional to Reservoir Scales

This paper presents a multidisciplinary structural analysis of the Reykjanes Peninsula where Holocene deformation of a young oblique rift controls the geothermal processes in presence of a transform segment. The new structural map from aerial images and outcrops is correlated with selected surface and subsurface data and shows a complex pattern: NNE extensional rift structures, N-S dextral and ENE sinistral oblique-slip Riedel shears of the transform zone, and WNW and NW dextral oblique-slip faults. Shear fractures are more common, and along with the NNE fractures, they compartmentalise the crustal blocks at any scale. The fractures are within two ENE Riedel shear zones, indicating a minimum 7.5 km wide transform zone. The greatly deformed Southern Riedel Shear Zone is bounded to the north and the south by the 1972 and the 2013 earthquake swarms. This shear zone contains the geothermal field in a highly fractured block to the west of a major NW structure. Some of the deformations are: a) clockwise rotation of rift structures by the 1972 earthquake zone, inducing local compression;b) magma injection into extensional and oblique-slip shear fractures;c) reactivation of rift structures by transform zone earthquakes;d) tectonic control of reservoir boundaries by WNW and ENE shear fractures, and the distribution of surface alteration, fumaroles, CO2 flux, reservoir fluid flow and the overall shape of pressure drawdown by N-S, ENE, WNW/NW and NNE fractures. Results demonstrate the role of seismo-tectonic boundaries beyond which fault types and density change, with implications for permeability.

Fracture Permeability: Outcrop Analogues from Active Plate Boundaries and Intraplate Contexts of Iceland

We bring new insights into fracture permeability with 7 analogues from the intraplate outcrops of West Iceland (WI), the active South Iceland transform zone (SISZ), the intersection of rift and SISZ near Hengill (Reykjafjall-RF), and the Reykjanes oblique rift (RP). WI formed at Tertiary plate boundaries, shifted away, is now cut by the Quaternary intraplate Snæfellsnes volcanic zone (SVZ), and undergoes occasional earthquakes. By contrast, fractures are being formed and reactivated under intense plate boundary earthquakes in the younger SISZ, RF and RP. Our mapping of stratigraphy, basement fractures, surface ruptures of earthquakes, and leakages of cold and hot water in all areas shows that: 1) In active SISZ, RF and RP, permeable fractures are identical to N-S to NNW dextral, ENE to E-W sinistral, and WNW to NNW sinistral source faults of earthquakes, acting as Riedel shears that accommodate the sinistral motion of the transform zone. The NNE/NE rift-parallel extensional fractures are the least frequent permeable set. Notably, the NW and WNW sets also show dextral motions in RP where they could be splay of each other but belong to a separate developed fracture system, and in the SISZ where the NW set is a splay of a N-S source fault of earthquake. However, permeable fractures in the intraplate WI are only oblique-slip sets striking N-S to NNW dextral, ENE sinistral, and WNW dextral parallel to the SVZ. 2) In each area, the permeable sets fit the fault plane solutions of intraplate or plate boundary earthquakes, as well as the latest stress fields that allow fracture opening for fluid flow. 3) Fractures are more open in the younger SISZ, RF, and RP, with leakages along the fractures and their splays rather than by their tips or in the stepovers. In the older WI where the crust and fractures are filled with secondary minerals, leakages are as much along fractures as where numerous fracture intersections facilitate fluid flow. 4) In case of intersecting fractures, the strike and dip direction of the structures determine which set acts as a carrier or a barrier to the flow. 5) Although Iceland is more known for rifting, these analogues demonstrate that fracture permeability, block compartmentalisation, and fluid flow are controlled by the oblique-slip structures developed under transform mechanism.

特厚煤层开采覆岩裂隙演化数值模拟研究

煤层开采造成覆岩破坏及裂隙演化发育,因采动卸压而释放的瓦斯在裂隙通道内流动、汇聚,给工作面生产带来了严重威胁。采用3DEC数值模拟实验,以宽沟矿B2特厚煤层工作面开采为原型,对采动覆岩应力演化规律进行了模拟研究,得到了采动覆岩应力演化的4阶段分布特征;在以覆岩卸压系数表征裂隙发育程度的基础上,绘制了裂隙富集区域的动态演化过程;并通过分析采动覆岩破坏及裂隙发育特征,在裂缝带高度范围内沿水平方向将采动覆岩裂隙划分为4个区域,分别为压密裂隙区、结构裂隙区、拉张裂隙区和原岩裂隙区。采动覆岩裂隙演化及区域的划分可为矿井布置钻孔抽采采空区卸压瓦斯,从而消除安全隐患,实现瓦斯资源化利用提供技术参考和依据。

中国大地构造区划及若干问题

在"新全球构造"思想的指导下,以板块构造学说为基础,以大陆动力学为线索,对中国区域地质构造和演化进行讨论并进行构造区划。由于板块构造随着时间的推移不断地发生变化,本文的构造区划以古生代时中国的板块构造格局为基础,同时考虑前古生代和后古生代时期中国的地壳构造演化,将中国划分为7个一级构造单元(板块)和30个二级构造单元,包括克拉通(或微陆块)和不同时期的造山带。在此基础上讨论了它们的边界和相互关系。

“中央造山带”早古生代缝合带及构造分区概述

“中央造山带”是夹持于中国塔里木、华北和扬子克拉通之间的近东西向延展的(局部为北东向和北西向)显生宙造山系统。该造山带中包括了库地-喀拉塔什、红柳沟-肃北-北祁连、南阿尔金-滩间山、昆中、朱阳关-夏馆和商州-丹凤6条早古生代缝合带。被缝合带所围限的前寒武纪地质构造单元包括中阿尔金-祁连-全吉地块、柴达木地块、北秦岭地块和东、西昆仑2个变质地体。南秦岭原为扬子克拉通的北部边缘,但卷入了显生宙造山带,成为中央造山带的一部分。对上述6条早古生代缝合带和6个前寒武纪地质构造单元的特点进行了概略总结,并阐述了各地质构造单元中的构造地层系统和热-构造事件的年代格架。

准噶尔-北天山盆山过渡带构造基本特征

准噶尔-北天山盆山过渡带是一条走向为NWW向（近EW向）的复杂构造变形带。根据构造变形样式的差异，该盆山过渡带从南向北可以划分为出若干变形“带”，自西向东可以划分出若干变形“段”，由深而浅可以划分出2-3个变形“层”。北天山（包括博格达山）是由基底卷入逆冲断层和褶皱构成的基岩断隆带，其中主干断层为向山体倾斜的高角度逆冲断层。该盆山结合带宏观上是一条冲断挠曲带，高角度逆冲的山前大断裂的下盘发育一系列中-低角度的基底卷入逆冲断层，部分逆冲断层上盘发育相关褶皱，但是基岩顶面和卷入变形的沉积盖层总体上构成向盆地倾斜的单斜构造。准噶尔盆地内部是一个宽阔的分层变形叠置带，侏罗系及上覆底层主要为滑脱褶皱变形，侏罗系在背斜核部加厚，滑脱背斜下伏地层及盆地基底发育高角度基底卷入断层。NNE-NE向、近SN向变换断层或构造变换带将上述构造变形带分隔成不同的“段”，同一“带”、同一“段”和同一“层”内的构造变形样式是类似的，不同“带”、不同“段”和不同“层”的构造变形样式则有明显的差异。盆山过渡带的构造特征受早二叠世正断层和走滑正断层活动、晚侏罗世基底卷入逆冲断层和走滑逆冲断层活动以及上新世逆冲断层活动和褶皱变形等多次构造变形的影响，但主要是上新世以来北天山逆冲隆升和对准噶尔盆地挤压的结果。先存的基底断裂、沉积盖层中的软弱岩层以及天山隆升和对准噶尔盆地挤压作用的不均一性是影响盆山过渡带构造形成和演化的主要因素。

贵州省煤矿瓦斯赋存构造控制规律与分带划分

瓦斯赋存规律认识不清,是导致煤矿瓦斯突出灾害频发的根本原因。应用瓦斯赋存地质构造逐级控制理论,结合贵州省煤矿瓦斯地质图编制资料,探讨了贵州省煤矿瓦斯赋存构造控制规律,进行了瓦斯分带划分和瓦斯带特征分析。研究结果表明:贵州省位于滨太平洋构造域和西部特提斯构造域的接合部,其构造演化控制着成煤环境和瓦斯赋存。燕山运动形成的一系列褶皱、逆掩断层和推覆构造,使煤体强烈变形、构造煤特别发育,是导致贵州省瓦斯突出严重的根本原因。燕山期岩浆活动,使煤的变质程度增加,生烃能力增强。将贵州省煤矿瓦斯赋存分布划分为3个高突瓦斯带和1个瓦斯带,即六盘水高突瓦斯带、织纳六枝贵阳北高突瓦斯带、黔北高突瓦斯带和黔东瓦斯带。

潘西煤矿断裂构造突水机制探讨

分析了潘西煤矿历年断裂构造突水资料,把其断层突水类型分为两大类:一是导水断层引起的突水;二是采动引起的断层“活化”突水。导水断层突水主要是由于构造岩带与底板裂隙相互贯通而致。采动引起的断层突水主要是在采动、矿山压力、地温应力、水应力、构造应力等共同作用下,断层产生滑移、张开,断层派生解理与裂隙发生蠕变、扩展、扩径、生长、相互贯通形成导水通道。应用断裂力学理论推导出断层产生滑移、解理发生扩展的计算公式。

建水地区主要断裂断层泥中石英碎砾表面SEM特征及其断裂活动

本文通过小江断裂带与石屏建水断裂交汇地４条主要断裂的现场考查及其断层泥中石英碎砾表面ＳＥＭ特征的分析研究表明：中更新世区内存在有一个较明显的构造活动平静期；全新世以来石屏—建水断裂仍明显强烈活动，李浩寨—甸尾断裂虽有活动但不强烈；黑依小水箐断裂和李浩寨—利民断裂，全新世以来基本不活动。

中国的板块构造区划

20世纪60年代板块构造学说传入中国,为广大地学工作者所接受并应用于相关的地质工作中。在新一代地质志的研究中,以板块学说为主导,已经成为共识。从板块构造来认识,板块的组成包括其核心及边缘。其核心为克拉通,由稳定的陆块组成;边缘包含了不同的活动大陆边缘和被动大陆边缘。边缘在后期板块汇聚的过程中,常由汇聚或碰撞等不同方式而成为不同的造山带。板块之间具有不同形式的汇聚带,其中主要是地壳对接消减带。在地球发展历史的过程中,不同时期的板块构造格局常有很大的变化。因此,本文以古生代的构造格架为主,探讨对中国大陆进行板块构造区划中的一些相关问题,并对全国的区划提出了一个初步方案。此方案将全国划分为7个I级单元(板块),30个II级单元(克拉通和造山带)以及103个III级单元。

郯庐断裂带附近地壳浅层现今构造应力场

郯庐断裂带是中国东部大陆规模最大的第四纪活动构造带和地震活动带,断裂带附近现代构造应力场明显控制了其运动方式、活动强度和地震活动,深入研究郯庐断裂带附近地壳浅层现今构造应力场,对于探讨断裂带当前活动性具有重要的科学意义。在参考前人研究成果的基础上,依据郯庐断裂带附近(山东—环渤海—辽宁段)6个600~1 000 m深孔地应力实测数据,初步揭示了断裂带附近地壳浅层应力分布规律,并分析其在不同活动段之间的差异。结合研究区已有其他应力数据(震源机制解、钻孔崩落、应力解除及断层滑动矢量反演数据等),重绘断裂带及邻区地壳现代构造应力场图,基于此详细分析了现今构造应力场主压应力方位特征及其对断裂活动方式的影响。初步结果表明:(1)在构造应力积累水平上,郯庐断裂带山东段西南端应力积累最高,渤海段东、西两侧之辽东半岛应力积累强度次之,辽宁段东北端本溪地区略低于渤海段,山东段北端和河北昌黎两地应力积累强度最低。(2)断裂带山东段南端地应力环境为逆冲型,而北端以正断型为主;渤海段之辽东半岛和河北昌黎及邻区主要为正断型;辽宁段东北端以正断型为主,兼具走滑型应力状态,地壳浅部地应力状态与断裂各段第四纪以来的运动学特征具有较好的一致性。(3)郯庐断裂带山东段及邻区现今构造应力场主压应力优势方位为N70°E,渤海段及邻区为N68°E,辽宁段及邻区为N72°E,各段之间差异不明显,该应力作用方式有利于断裂带产生右旋走滑活动,同时也表明郯庐断裂带所处的华北及辽宁大部地区具有较统一构造应力环境。

塔里木盆地构造格架和构造应力场分析

以区域构造背景为基础,分析塔里木盆地的基本构造格架是本文的主要宗旨。塔里木盆地中部存在一规模较大的近于E-W向的构造带,谓中塔里木构造带或中塔里木断裂带,平面上它大致和塔里木中央隆起带相对应,东延,和阿尔金造山复合体的一组规模较大的、近于直立的E-W向韧性剪切带和断裂带相连,西延,插入西昆仑造山带和南天山造山带的结合部位。在剖面上具有背冲式(断背状)断裂组合,其形成始于早古生代,强烈活动期在三叠纪后。断裂带具有逆冲、走滑和垂向挤出性质,是目前塔里木盆地的主要含油带。中塔里木断裂带和塔中隆起带属于同一动力学系统中不同构造阶段的产物,在空间上是互为一体的,在早古生代为一强烈坳陷带,晚古生代以后逐渐转化为隆起带。大致位于北纬39°30'～40°的E-W向高正磁异常带,为一以基性麻粒岩为代表的结晶基底、基性岩墙和花岗质类岩石,并叠加晚元古-早古生代活动陆缘岩浆弧的大型东西向构造杂岩带。中塔里木断裂带(塔中隆起带)以南至塔南前陆盆地的塔南地区,以E-W向构造岩浆岩带上叠NEE向断裂构造(断隆和断凹)为基本特征,其断裂组合完全可以与南阿尔金断裂以南的南阿尔金地体的断裂组合相类比。中塔里木断裂带以北至塔北前陆盆地的塔北地区以长期坳陷为特征。西昆仑-塔里木盆地盆山结合带表现为西昆仑山体的北向逆冲推覆和山前带的强烈挤压及塔南前陆盆地的急剧沉降,而西天山-塔里木盆地盆山结合带则表现为由于塔里木地块向天山复合造山体的强烈北向俯冲导致的南天山的南向逆冲推覆和塔北(前陆盆地后的)隆起。塔里木盆地处于南北两侧向盆地挤压、东侧左旋走滑和西侧右旋走滑的复杂构造应力状态,塔里木盆地现今构造格局的形成基本上是上述4类不同性质的构造应力场对先存的E-W向构造经多次强烈改造、叠加的结果。

克拉苏构造带盐下超深层储层的构造改造作用与油气勘探新发现

塔里木盆地克拉苏构造带油气群下白垩统巴什基奇克组埋深超过6000 m,储层基质渗透率低,裂缝普遍发育,构造对储层的改造作用明显,但博孜9井的勘探突破反映出不同区带间构造改造作用差异较大、非均质性极强,重新认识构造对储层的改造作用对于预测超深层储层、指导油气勘探生产具有重要的意义。为此,基于钻井取心、构造平衡恢复、裂缝充填物同位素测年、区块应力数值模拟等资料,结合流体包裹体、声发射古应力、铸体薄片等实验分析方法,从定性分析到定量计算、研究了克拉苏构造带油气群超深层储层的构造改造作用及其差异性。研究结果表明:①北部天山造山带及南部古隆起控制了该构造带储层的沉积格局及差异构造变形,形成巴什基奇克组储层“西薄东厚”的分布特征;②博孜区段古应力最小,构造变形主要为正向挤压、逆冲传播,局部井区为斜向压扭;③大北区段主要为斜向压扭,古应力较小,构造变形为逆冲叠置;克深区段古应力最大,构造变形主要为正向挤压、后缘逆冲抬升、前缘滑脱收缩;④差异构造变形使同一构造带不同构造变形样式的构造减孔量呈现出较大的差别,且控制了不同区段造缝期与成岩胶结的叠加影响、中晚期裂缝网络与油气成藏期的配置关系,加剧了储层的非均质性,是区段间产能差异的基础改造因素;⑤现今构造应力的大小及方向影响裂缝有效性,南部为强挤压应力区,背斜相对高部位裂缝走向与现今应力交角较小,裂缝有效性最好;⑥构造成岩环境决定了构造裂缝充填物的类型,北部区块以淡水—半碱水介质成岩环境为主,裂缝充填物类型为方解石,有利于对储层进行酸化压裂改造。

敦化盆地发育演化及其沉积响应

敦化盆地位于敦密地堑中段,为受敦密断裂控制的裂陷-断陷叠合盆地。敦密断裂带在中、新生代发生了一系列构造体系的转换,即在晚三叠世启动,中晚侏罗世为挤压性质,白垩纪—古近纪具左行平移并有一定规模的拉张,古近纪末有一次挤压,新近纪以后又转变为拉张状态。敦密断裂带的演化对敦化盆地的生成、发展及演化起着主要的控制作用。敦化盆地在中新生代的演化过程为:晚侏罗世—早白垩世的挤压造山-走滑拉分-初始张裂阶段(裂陷发育阶段)、晚白垩世—古新世的回返隆升剥蚀阶段、始新世—渐新世的断陷盆地发育阶段以及新近纪之后的拗陷和玄武岩喷发阶段。各个演化阶段具不同的沉积响应特征。

鲜水河—小江断裂带7级以上强震构造区的划分及其构造地貌特征

划分了鲜水河—小江断裂带 7级以上历史地震的强震构造区 ,分析了各强震构造区地质构造和构造地貌特征 .认为强震构造区是沿断裂带的一些特殊构造段落 ,区内以断裂带主要分支断层的左阶斜列、并行排列或三叉构造组合为主体构造格局 .强震构造区内发育了构造较复杂的盆地类型 ,如三叉区拉分盆地、双阶区拉分盆地和阶区

深圳断裂带构造活动性分析

深圳断裂带的活动性关系到深圳发展的前景,从构造地质学、遥感图像、地震学、地貌学和地球动力学的角度出发,论述了深圳及其邻近地区的地质构造背景,阐述了深圳断裂带的构造活动性。通过对断裂带地层剖面和断层物质研究发现,断裂带晚更新世以来没有明显活动迹象;地震活动方面,断裂带所在区域地震活动以微震为主,且震源分布与断裂带产状一致,反映断裂具有一定的活动性;根据地应力监测资料,最大主应力量值小且应力方向北西向,与断裂近乎垂直,不利于断裂活动。综合各方面因素,认为深圳断裂带晚更新世至今活动已经明显减弱;现代微震活动是其构造能量缓慢释放的表现,现今深圳断裂带构造稳定,不会发生较大规模的活动。