哈山冲断带构造变形数值模拟

岩石圈流变结构是控制大陆碰撞造山的重要因素.哈山冲断带的构造变形、地表地形与青藏高原周缘冲断带差异较大,指示需要开展地壳流变学研究.本研究采用二维数值模拟,设计了盆山上地壳强度横向差异的单因素实验,模拟结果分析表明：若上地壳强度山弱盆强,构造变形集中于造山带,断块垂向叠置造成造山带隆升,使地表地形的构造高点位于造山带;若上地壳强度山强盆弱,构造变形集中于冲断带和盆地,盆山相互作用造成地表地形的构造高点位于冲断带,而非后陆.本文基于此单因素实验,模拟了哈山冲断带构造演化,发现哈山冲断带晚二叠世发育推覆构造后,构造变形逐渐减弱,扩展方式由前展式变为后展式,基底倾向由向后陆变为向前陆.结合哈山及龙门山的多学科观测资料,本文认为哈山和龙门山冲断带的构造变形、地表地形分别符合地壳强度山强盆弱模式和山弱盆强模式.研究成果可以为中西部冲断带的地球动力学模型和实验模型的搭建提供一定启示,同时对研究区内构造控藏分析和油气勘探具有指导意义.     

焉耆盆地北缘和静逆断裂-褶皱带第四纪变形

焉耆盆地是塔里木盆地东北缘天山山间的重要坳陷区,盆地北缘发育的和静逆断裂-褶皱带是一条现今活动强烈的逆断裂-褶皱带,对其第四纪以来缩短量和隆升量的计算有利于分析该区域的构造活动情况,对缩短速率和隆升速率的估计可以与天山造山带其他区域的活动速率进行横向对比,从而反映出焉耆盆地在天山晚新生代构造变形的作用。在深部资料不足的情况下,对背斜形态完整、构造样式简单的和静逆断裂-褶皱带,利用地表可获得的地层和断层产状,通过恢复褶皱几何形态,计算褶皱的缩短量、隆升量和断层滑动量,得到逆断裂-褶皱带早更新世晚期(1.8Ma)、中更新世(780ka)和晚更新世中期(80ka)以来的缩短量分别为1.79km、0.88km和26m,初步估计的缩短速率分别为0.99mm/a、1.13mm/a和0.33mm/a。显示和静逆断裂-褶皱带自开始形成以来构造活动强度并不一致。与地壳形变观测结果对比,作为南天山东段最主要的坳陷区,焉耆盆地吸收了这一区域(86°～88°E)的大部分地壳缩短,且主要表现为盆地北缘新生逆断裂-褶皱带的强烈变形。     

南海北部陆缘深水-超深水盆地成因机制分析

本文以海洋地质调查和油气勘探开发中积累的地质和地球物理资料的解释和分析为基础,描述和划分了南海北部被动陆缘地壳岩石圈结构构造单元,由陆向海划分出近端带、细颈化带、远端带和洋陆转换带（OCT,含边缘高地）四个构造单元.从细颈化带到OCT基本处于现今陆架坡折带之外的深水-超深水区的范围,以强烈的地壳薄化和发育大型拆离断层控制的拆离盆地为特征.这些深水-超深水盆地的同裂陷阶段均经历了早期均一断陷、中晚期拆离式断陷的演化过程,受控于南海北部大型拆离断层作用及其所导致的岩石圈临界破裂过程.新的深水-超深水盆地形成机理的认识为南海北部陆缘岩石圈的非瞬时伸展破裂过程的分析提供了新的视角,同时,陆缘深水-超深水盆地具有独特的构造-沉积体系配置和构造-热演化过程,将为科学评价南海北部陆缘深水-超深水盆地油气勘探潜力提供新的思路.     

莺歌海—琼东南盆地构造-地层格架及南海动力变形分区

通过对盆地地震剖面构造-地层的详细解释,在莺歌海盆地和琼东南盆地(简称莺-琼盆地)古近纪同裂陷充填序列中识别出一条区域性的构造变革界面——T70,该界面在地震剖面上表现为显著的下削上超的地震反射结构特征,发育的时代为32~30 Ma,与南海海底扩张起始和红河断裂带左旋走滑的时间一致; T70界面将莺-琼盆地的同裂陷期地层分隔为断陷层和断坳层(琼东南盆地)或坳陷层(莺歌海盆地)两个构造-地层单元,这些构造地层单元和构造变革界面是南海及其周缘区域板块构造重组事件在莺-琼盆地的响应.论文结合前人成果,论述了以红河—越东—Lupar线断层为界,可以将南海及其周缘地区划分为结构构造、演化特征和动力学背景有显著区别的两个构造变形区:挤出-逃逸构造区和古南海俯冲拖曳构造区.以此构造变形分区为基础,确定了莺-琼盆地的动力学机制,建立了其构造演化模式.本研究有助于从整体上理解南海周缘盆地的发育演化过程及主要控制机制,并对大陆边缘动力学研究和陆缘盆地区的油气勘探有重要意义.     

湘西沅麻盆地早白垩世红层古地磁学研究及其对川东褶皱带新生代构造变形的指示

川东褶皱带作为华南板块中部的"侏罗山式"褶皱,开始形成于晚古生代.自白垩纪晚期开始,受太平洋板块和印度板块对欧亚大陆挤压的影响,这一构造带乃至华南板块中部又叠加了新的构造变形.但是,目前对于川东褶皱带白垩纪以来的构造演化缺乏足够的认识.位于川东褶皱带东侧、雪峰造山带西麓的沅麻盆地形成于早白垩世.晚白垩世以来,沅麻盆地与川东褶皱带处于同一构造应力场中,因此对盆地内早白垩世红层的古地磁研究对于解释川东褶皱带中生代晚期以来的构造演化有着重要的意义.该研究在沅麻盆地早白垩世红层中开展的古地磁学研究获得了可靠的原生剩磁分量：Ds=15.6°,Is=42.9°,k=118.6,α95=2.6°,表明沅麻盆地自早白垩世以来发生了4.1°±3.0°的顺时针构造转动.对川东褶皱带周缘白垩纪古地磁数据所揭示的地壳旋转变形,与断裂和褶皱轴组成的构造线迹变化之间的线性相关性分析,表明川东褶皱带位于齐岳山断裂带东南侧的部分,受印度板块-欧亚大陆、太平洋板块-华南板块间的挤压作用,自晚白垩世以来累积了约50~93 km的右旋错断量.     

托斯台逆断裂-褶皱带晚第四纪活动特征

托斯台逆断裂-褶皱带位于乌鲁木齐山前坳陷的西部,为近东西向展布的新生代逆断裂．背斜带。它主要由北单斜带、中部背斜带和南单斜带3个构造带组成,在各构造带均发育逆活动断裂。地震勘探资料显示,南单斜带与中部背斜带为滑脱体,逆断裂在深部沿滑脱面与清水河子深断裂相汇。研究表明,北单斜带与中部背斜带逆断裂断错了晚更新世堆积物,在晚更新世有显著的活动;南单斜带逆断裂断错了全新世堆积物,在全新世时期有最新活动。中部背斜带逆断裂晚更新世以来水平缩短速率为0．6～1．3mm／a;南单斜逆断裂全新世水平缩短速率为0．2～0．6mm／a。     

龙门山中段推覆构造带及相关构造的演化历史和变形机制（二）

川西前陆盆地是从晚三叠世晚期（须家河期）以来开始发育的，其形成是龙门山推覆构造带自北西往南东持续推覆的结果。本区的构造发展经历了伸展裂陷、构造反转和持续推覆３个主要阶段。构造变形的力源主要来自松潘－甘孜褶皱带的北东～南西向收缩派生的南东向挤压     

龙门山中段推覆构造带及相关构造的演化历史和变形机制（一）

从龙门山推覆构造带和松潘－甘孜褶皱带的变形特征及发展过程，论证了龙门山中段推覆构造是由于其北西侧松潘－甘孜褶皱带中的北东～南西向收缩派生的南东向挤压而逐渐发育起来的。推覆作用是晚三叠世晚期以来自北西往南东逐渐扩展的，属前展式（背驮式）。     

喜马拉雅东构造结东缘碧罗雪山-崇山剪切带北段构造变形特征及构造意义

位于喜马拉雅东构造结东缘的新生代碧罗雪山-崇山剪切带出露各类构造岩,其西侧翼主要为片麻岩带,以条带片麻岩、眼球状糜棱岩化片麻岩和混合片麻岩为特征,东侧翼为糜棱岩化片岩带;基于野外构造-组构几何关系和叠加-改造痕迹,可识别出多期韧性、韧-脆性和脆性构造变形（D1~D4）.第一期变形D1主要发育等斜-紧闭褶皱F1（褶皱轴近N-S走向）和陡立的轴面劈理S1,以及代表地壳物质垂向增厚和侧向减薄的布丁构造;第二期变形D2构造特征为发育大规模韧性走滑剪切面理S2,部分S2面理发生褶皱变形,形成褶皱F2,褶皱轴陡倾伏,褶皱面陡立,近N-S走向,与剪切面理S2近平行,D2构造样式表现为左旋走滑挤压应变（Transpression）特征;D1和D2构造变形均被晚期NW-SE和NE-SW走向的第三期D3构造改造,即走滑剪切带S3和共轭走滑断裂;第四期构造D4以脆性右旋走滑伸展应变（Transtension）为特征,即N-S走向的走滑组分和正断组分同时发生.结合邻区新生代哀牢山-红河剪切带和高黎贡剪切带的构造几何、运动学和年代学数据,分析认为自新生代印度-欧亚汇聚-碰撞以来,环喜马拉雅东构造结及东缘地区的陆内构造变形经历了地壳增厚（D1）、左旋走滑挤压（韧性域D2和韧-脆性域D3）和右旋走滑伸展（D4）多期构造变形和变形体制的转换.     

安徽北淮阳构造变形带特征与应力状态研究

在分析安徽北淮阳构造变形带变形特征和活断层作用的基础上,利用该区现代中小地震资料,采用近震直达P波、S波垂直向最大振幅比方法、震源机制的系统聚类和统计分析法,反演部分地震震源机制,并分析现代中小地震活动特征及应力场状态。结果表明,北淮阳构造变形带上主要断层现今处于活动状态;现代中小地震震源总体较浅,在2次6级地震震中附近形成小震密集区,可能反映了震源区介质相对破碎。震源机制的系统聚类和统计分析结果显示,该区断层以走滑或斜滑型破裂为主,但存在倾滑的逆断层;区内应力作用方向以水平为主,也存在部分垂向力作用;主压应力P轴的优势分布为近EW向,其中既有华北应力场,也有华南应力场作用;有少量近NS向应力场作用存在。反映该区处于应力场过渡区,因此将其作为华北、南华地块区的边界是合理的。     

Growth structures and growth strata of the Qianjiadian Basin in the western Yanshan fold and thrust belt,North China

The northwestward subduction of the Izanagi Plate beneath the eastern Eurasian Plate during the Late Mesozoic caused a series of compressional deformation events in the Yanshan fold and thrust belt(YFTB), but the tectonic deformation timing, tectonic properties and relationship between tectonic uplift and sediment accumulation in the intermontane basins continue to be debated. For this reason, the sedimentology, sediment provenance, and basin structure of the Qianjiadian Basin(QJB) in the northern Beijing region during the Late Jurassic and Early Cretaceous were studied in detail. The results suggest that a fault-propagation fold-type(FPFT) growth structure and growth strata developed on the western edge of the QJB and that the top part of Member 2 and Member 3 of the Tuchengzi Formation are growth strata controlled by the limb rotation mechanism. In two small thrust faults in the QJB, the Mesoproterozoic Xiamaling Formation is thrust over the Tuchengzi Formation, and these faults may have controlled the development of the fault-bend fold-type growth strata. An analysis of the "source-to-sink" process suggests that the hanging wall succession of the Shangyi-Pingquan fault(SPF) was the main source area of the Late Jurassic to early Early Cretaceous strata in the QJB. A zircon206 Pb/238 U age of 140.8±2.4 Ma for the volcanic rocks at the bottom of the FPFT growth strata represents the timing of the initiation of FPFT growth structure development. The discovery of the FPFT growth structure and growth strata in the QJB indicate that the QJB was an intermontane flexural basin controlled by fold and thrust structures during the early Early Cretaceous. Near the E-W-trending SPF, the NE-SW-trending Qianjiadian thrust fault(QJTF) and two small intrabasinal thrust faults may constitute a unified right-lateral strike-slip system that formed in response to the northwestward flat subduction of the Izanagi Plate beneath the East Asian continent during the Jurassic-Early Cretaceous.     

南海海盆东北部内孤立波的地震海洋学研究

以往利用地震海洋学方法发现的内孤立波大多在东沙岛附近,本文在南海海盆东北部首次利用地震海洋学方法发现了海盆中的内孤立波.通过叠前偏移观察该内孤立波细结构的变化,发现内孤立波波形在采集时间段内整体较稳定,内孤立波浅层反射相对深层变化较大.通过改进前人的方法,利用共偏移距道集叠前偏移剖面计算内孤立波视相速度.该方法比直接使用共偏移距道集拟合的共中心点-炮点对曲线线性更好,其计算的内孤立波视相速度为0.82 m·s^-1,内孤立波视传播方向为从NW向SE（172°N方向,0°指向北）.

     

Gravity and magnetic field characteristics and hydrocarbon prospects of the Tobago Basin

The Tobago Basin, which is located offshore northern Venezuela with a southern margin close to Trinidad and Tobago, has an area of approximately 59,600 km². The Tobago Basin has relatively favourable hydrocarbon prospects, and to date, exploration work has mainly concentrated on small areas of the southwestern portion of the basin. To conduct a comprehensive study of the structural framework of the basin and the characteristics of the basement in order to identify prospective zones for hydrocarbon exploration, shipborne‐measured and satellite‐measured gravity data, shipborne‐measured magnetic data, and aeromagnetic survey data were analysed. A regularisation filtering method was used to separate and obtain regional and residual gravity and magnetic anomalies. Directional gradients of gravity and magnetic anomalies and the total horizontal gradient and vertical second derivative of gravity anomalies were employed to extract information about fault structures. Regression analysis methods were used to determine the basement depth. The geological significance of the gravity and magnetic fields was examined, the structural framework of the basin was assessed, the basement depth was estimated, and favourable hydrocarbon exploration prospects within the basin were identified. The results show that the Tobago Basin contains complex structures consisting mainly of two groups of faults trending in northeasterly and northwesterly directions and that the major northeasterly trending faults control the main structural configuration and depositional system within the basin. The basement of the Tobago Basin has deep rises and falls. It can be divided into the following four secondary tectonic units: the western sub‐basin, the central uplift area, the southern sub‐basin, and the northeastern sub‐basin. The central uplift area and northeastern sub‐basin are most likely to have developed hydrocarbon accumulations and should be targeted for further exploration.     

A preliminary study of NW Zhejiang foreland fold and thrust belt in Southeast China

The Upper Permian Dalong Formation (P₂d) and Changxing Formation (P₂C), and the Lower Triassic Zhengtang Formation (Tlz) are of deep-water turbidites. The sedimentary features of the NW Zhejiang are of SE-dipping passive continental margin from the Paleozoic to the early Triassic. Together with the foreland molasse basin during the late Triassic (T₃w), the tectonics of the NW Zhejiang is characterised by a tectogenesis which took place in the middle Triassic. From SE to NW, the structural style varies from multi-duplex, antiformal stack to imbricate fans, and then to Jura Mountain-type fold zone with fold-style varying gradually from large-scale tight fold to midscale chevron fold, then to cylindrical fold, reviewing a preliminary scenario of foreland fold and thrust belt. The space-distributed structures and the tectonic vergence indicate the significance of deformation in (T1-T₃). Project supported by the National Natural Science Foundation of China and Chinese Academy of Sciences.     

Segmentations of foreland belts and their tectonic mechanism in the Southwest Tarim Basin

Many geologists focus on the foreland structures, co-relationship between shallow and deep structures and their dynamics between intra-continent orogenies and foreland basin in recent years[1―17]. The intra-plate collision and deformed area of West Kunlun-Pamirand Southern Tianshan become the natural lab of this studies and there are many new developments con-cerned with the geometry and kinemics of foreland thrusting, back-thrusting and triangle zones[3―14]. Many types of foreland thrusti…     

南海含天然气水合物地层地震反射特征及可能分布研究

天然气水合物是当前能源与环境领域的研究热点之一,南中国海是天然气水合物赋存的有利区域。天然气水合物的存在改变了沉积地层的声学特征,这一性质使多道地震勘探成为发现海洋天然气水合物的主要手段。本文首先根据地震成像结果定性分析南海可能含天然气水合物沉积地层的地震反射特征,初步确定天然气水合物存在的可能性并指出地震成像关键技术。在无井条件下,构建虚拟井进行波阻抗反演得到定量的地层速度参数进一步证实这一可能性,最后将反演获得的速度场与ODP184 航次在此区域获得的地球物理、地球化学信息综合分析,可以确定此区域天然气水合物的存在及其空间展布。     

利用反射地震和多波束资料研究南海西北部麻坑的结构特征与成因

麻坑通常是由海底流体逸散形成的一种海底表面的残留地貌.本文所研究的区域主要位于南海的西北部,包括琼东南盆地的西南部和中建南盆地的中北部.该区域海底表面主要覆盖细粒沉积物,并且底流活动强烈,底流水道发育,为麻坑的形成和发育提供了有利条件.麻坑发育的主要因素是流体逸散系统,本文通过反射地震资料在本区发现了断层、气烟囱、泥火山、泥底辟、声空白/声混浊、强反射等多种与流体逸散相关的指示特征.麻坑的几何特征随着区域的不同会有较大变化.首先本区麻坑的尺寸跨度较大,与底流水道伴生的麻坑和广乐隆起的麻坑表面宽度通常是几十米到数百米,其他区域麻坑的表面宽度通常可达数千米,被称为巨型麻坑.其次本区麻坑的表面形态复杂多样,有圆形、椭圆形、新月形、环形等.各种不同的形态有可能指示了麻坑的不同发育阶段,新月形麻坑可能发育程度较低,其次是环形,圆形则相对较为成熟.据此推断发育程度较低的新月形麻坑有可能是活动麻坑,而地震海洋学的资料也倾向于证实这一点.     

琼东南盆地天然气水合物及其成藏模式的海洋可控源电磁研究

南海琼东南盆地是天然气水合物重要远景区之一.由于盆地大部分地区海底地形平缓、地层近于水平,增加了利用地震反射剖面识别似海底反射（BSR,bottom simulating reflector）的难度,从而影响了对水合物的评价.为了进一步开展琼东南盆地水合物调查研究,本文在研究海域进行了海洋可控源电磁探测试验,将自主研发的10台接收机以500 m的间距,投放至水深约为1360 m的海底,完成了一条4.5 km剖面的电磁数据采集.通过对采集的数据进行处理与二维（2D）反演,获得了研究剖面海底的电阻率断面图.反演结果显示,研究区海底60~330 mbsf（meter bottom of seafloor）的地层中,存在多个横向不连续分布的高阻异常体,电阻率介于2~10 Ωm之间;在海底330 mbsf之下,横向上发育了电阻率为2~4 Ωm的3个高阻体.根据研究区热力学条件,本文估算了生物成因气与热成因天然气的水合物稳定带（GHSZ,gas hydrate stability zone）厚度,结合高阻体的分布特征推断了地震剖面上BSR的位置.在此基础上,对反演的电阻率断面进行解释,推断了研究区水合物的分布及游离气运移通道.研究表明,勘探区具有形成天然气水合物矿藏的地质与地球物理条件,其成藏模式可能属于"断层、裂隙输导的下生上储型",水合物的气源为生物成因气.