太仓-奉贤断裂基于遥感、重磁数据的构造特征研究

利用遥感影像数据研究太仓-奉贤断裂地貌特征,通过小波多尺度方法对布格重力数据进行分解,并应用重力、航磁数据分析其深部结构,结合前人人工地震及沉积演化历史资料进一步探讨该断裂与古海岸线的关系.布格重力异常显示,该断裂形成NW向的重力梯度带,由北向南依次控制白茆断凹、甪直断凹和松江断凹的东部边界;重力小波细节图表明,该断裂切穿中上地壳到达下地壳,在下地壳太仓-奉贤断裂仍与太仓-陈家镇断裂、昆山-嘉定断裂、青浦-龙华断裂、松江-嘉善断裂和南汇-平湖断裂相交;航磁场揭示该断裂两侧的地质体存在明显的磁性差异.综合重力、航磁及前人资料可知,太仓-奉贤断裂是江苏地区一条重要的隐伏构造断裂,切穿底部基岩至下地壳,构成全新世中期古海岸线.     

利用重力、航磁资料研究木里-盐源弧形构造带及邻区的深部孕震环境

探讨川西高原木里-盐源弧形构造带重磁异常分布特征与地震孕育和发生的深部孕震环境及地震构造背景。基于木里-盐源弧形构造带的重力和航磁资料,采用重力三维视密度反演、航磁化极和延拓等位场数据处理方法,获得壳内不同深度的视密度变化信息和磁性介质的分布范围及重磁异常的形态、幅值大小及梯度变化等特征。综合三维视密度反演结果表明:沿木里-盐源弧形构造带两侧的视密度异常展布特征各异,锦屏山弧形构造带西侧区域大范围分布的低密度异常反映了川西高原的中下地壳深度范围物质较为软弱。深部低密度异常的存在容易造成浅部脆性地壳内应力积累,是驱动木里-盐源地区构造变形作用和地震频繁活动的深部动力环境。航磁ΔT化极结果显示研究区两侧不同区域呈现不同的异常展布特征,构造边界断裂具有明显的深部地球物理场标志,中强震多数发生在断错地壳和上地幔的深大断裂及其附近。根据航磁ΔT向上延拓10km和20km图像可知,2012年发生在盐源与宁蒗交界处Ms 5.7地震,其震中位置处于航磁异常的突变带上,该区域壳内块体或基底性质之间存在明显的介质磁性差异,易于造成应力积累并在构造应力作用下发生破裂,这是此次Ms 5.7地震的深部孕震条件。     

综合地球物理在三峡重庆库区深部断裂构造特征研究中的应用

地球物理反演问题的多解性等因素决定了综合地球物理解释的必要性和重要性.在继承、分析前人研究成果基础上,运用综合地球物理研究方法和技术路线,结合野外踏勘调研资料,对现有地震、重力、航磁资料进行精细分析研究,获得了对库区深部断裂构造特征的新认识,为深入研究三峡重庆库区深部断裂构造特征,库区地震、地质灾害的监测与防治提供基础依据.     

银川盆地地壳稳定性分析

银川盆地地质构造复杂,地震活动频繁.为评价该区域地壳的稳定性,用重力资料解译3条北西断裂,并结合已有的构造认识,讨论深部构造样式和浅部断裂的空间展布特征及活动性,以及地震活动特征、大地形变特征及区域地球物理场特征;用模糊数学的综合评价模型将银川盆地按照77个待评区进行分区评价.结果表明,银川盆地总体处于稳定与不稳定之间;贺兰山断裂、黄河断裂附近以及盆地的中部贺兰等地区,由于断裂活动性强、构造复杂,深部构造交汇等特征,稳定性相对较差,而盆地的北部和南部稳定性则相对较好.     

鲁西西部壳内物性界面计算及其应用研究

利用位场(重力、航磁)对数功率谱计算了鲁西西部地壳内部的物性(密度、磁性)界面。从资料的处理和结果分析,探讨了本区深层构造的特点和深层构造与浅层构造的关系,并对壳内物性界面的计算结果在能源预测与勘探、地震等方面的应用作了讨论。     

遵义北郊储热构造的地、物、化、遥特征分析

研究区布格重力异常在该区与地质构造线方向基本一致，主要呈北东向梯级带展布为主，总体从东向西逐渐减小，而地热点主要分布在零值线附近及剩余重力异常等值线上；地热点出露与磁法推测的断裂带有联系，与航磁异常关系不明显；研究区地表以F、CaO、MgO地球化学高背景分布；从遥感资料来看，地热点多位于松林—岩孔背斜，该背斜为主要的储热构造；北东向断裂切割其他断裂，为新构造运动形成或复活断裂，为地热的形成提供通道与空间。     

鄂东襄樊-广济断裂黄州段未来地震 危险性分析

通过对鄂东襄樊-广济断裂黄州段的地质构造、第四纪活动性、地震活动和现今地壳变形的分析,综合判定该段断裂的活动性和构造特征。该断裂是中国东部地区典型的弱-中等活动断裂。采用地震构造类比法和矩震级经验关系,综合评估了断裂的未来可能最大发震震级为6. 0级;利用历史和现今地震活动资料,建立了按500 a归算的震级-频度关系,采用泊松概率模型,计算得到襄樊-广济断裂黄州段未来50～200 a地震平均复发间隔和发震概率等定量参数。该成果可为区域地震危险分析及工程抗震设防提供参考。     

大伙房水库断裂构造特征的航磁解释

为查明大伙房水库库区的断裂构造特征及分布,保证工程的正确选址,使工程建设与其他地质环境相协调提供基础资料,利用航磁手段,编制了航磁△T磁场等值线图,将该区断裂构造分为四组,对其分布特征进行解释.不同性质磁场区之间,分界线两侧区域地质发展及演化存在明显差异,其断裂规模大、切割深;线性正或负磁异常带,反映出断裂控制与周边地区的岩性变化;串珠状线性异常带中的单个异常多呈等轴状或似二度异常,沿断裂存在着岩浆活动,断裂切割的深度较深.     

贵州中-深部断裂构造的地震危险性研究

以贵州省的地质构造分析、地貌分析、地震记录到的地震精确定位、重力和航磁数据判断中-深部断裂分布情况,结合人工地震剖面和中石油西南物探分公司对剖面的解释,得出贵州中-深部构造和破坏性地震关系,确定孕震的中-深部断裂。以多种地球物理探测方法以及地质构造分析、地貌分析相结合的深浅构造研究方法,确定断裂的分布特征及活动特征,总结孕震构造条件的研究方法具有一定的可行性。并且随着物探技术的不断发展,向深部断裂的探测将得以实现,进而得到更加详实的中-深部构造情况,对研究孕震区的深部环境、地震的发震原因将具有较大的指导和借鉴意义。     

塔里木盆地中央高磁异常带成因: 来自地震反射剖面的新证据

根据钻井资料及构造分析, 对塔东地区二维地震资料和塔中地区三维地震资料进行系统解释, 在该地区震旦系之下识别出断坳二元结构的陆内裂谷, 该裂谷由4个断陷沿纬向形成一个裂谷带, 其平面分布形态与高磁异常范围极为吻合。结合构造与地层发育特征认为: 裂谷期断陷中发育典型陆内双峰式火山岩, 是航磁异常带上磁力高的直接表现; 高磁异常带轴线与断陷的边界断层位置吻合, 异常源具有垂直向下的通道, 与基底断裂及深部岩浆上涌有关。正演计算验证了南华纪裂谷带模型的磁异常结果。高磁异常带东段为裂谷成因, 向中部、西部裂谷作用逐渐减弱直至消失, 至巴楚段高磁异常主要由二叠纪玄武岩造成, 异常带西段则属于塔南古陆块。     

邦戈尔盆地潜山风化壳储层发育特征与主控因素分析

邦戈尔盆地潜山储层为前寒武纪花岗质风化壳储层,风化壳储层岩性复杂,物性较差,储层类型多样。为明确潜山风化壳储层发育主控因素、建立风化壳储层评价标准,通过分析储层岩性矿物元素差异、储集空间类型和裂缝分布特征确定风化壳储层发育主控因素,并将主控因素进行级别定义和相互匹配,建立风化壳储层评价标准。结果表明：岩性是形成储层的宏观背景,风化淋滤作用是控制储层孔隙发育的基础,构造作用是影响储层裂缝形成的重要因素;花岗质风化壳储层可以划分为三大类,其中Ⅰ类储集性能最好,Ⅲ类最差。风化壳储层评价标准的提出可进一步为风化壳潜山储层的高效勘探开发提供更为准确的指导。     

Petrogenesis and significance of the Hongshan syenitic pluton,South Taihang: zircon SHRIMP U-Pb age, chemical compositions and Sr-Nd isotopes

The Hongshan syenitic pluton (South Taihang) is mainly made up of hornblende syenite and minor granite. SHRIMP zircon dating yields a U-Pb age of 135±2.7 Ma for the emplacement of the pluton, while biotite Rb-Sr isotopic data give an isochron of 120. 3±2.4 Ma. Hongshan syenites show low silica, high alkalis and LILE such as Sr, and exhibit negligible Eu anomalies or slightly positive anomalies in the REE patterns. The syenites show quite enriched isotopic compositions with Isr from 0.7052 to 0. 7102 and εNd(t) from -7.5 to - 11.1. Petrogenesis of the pluton can be that partial melting of an enriched lithospheric mantle gave birth to an alkali basaltic magma, which subsequently underplated in the lower crust and experienced a coupled fractionation of ferromagnesian phases like pyroxene and hornblende and minor (<10 %) contamination of lower continental crust, producing the Hongshan syenites that partially e-volved into granite through combined fractionation of hornblende and feldspar. Our data are not in agreement with a previous model that the syenites originated from melting of lower crust in a thickened crust circumstance, and thus do not support the speculation of "East China Plateau" in the Mesozoic.     

Crustal P-wave velocity structure in Lower Yangtze region： Reinterpretation of Fuliji-Fengxian deep seismic sounding profile

A deep seismic sounding profile in this paper, from Fuliji in Anhui Province to Fengxian of Shanghai City, is located at eastern China (Fig. 1). The field work was jointly accomplished by the Chinese Geological and Mineral Bureau, the China Seismological …     

地壳岩石压剪断裂端倪

将地壳断层视为地壳表面裂纹，应用压剪断裂观点对地震机理进行了分析，提出了地壳岩石复合断裂的压剪断裂核模型和有待研究的课题。开展这方面的研究将有利于地震预报及找矿工作。     

Process and mechanism of mountain-root removal of the Dabie Orogen—Constraints from geochronology and geochemistry of post-collisional igneous rocks

Systematical studies of post-collisional igneous rocks in the Dabie orogen suggest that the thickened mafic lower crust of the oro- gen was partially melted to form low-Mg# adakitic rocks at 143-131 Ma. Delamination and foundering of the thickened mafic lower crust occurred at 130 Ma, which caused the mantle upwelling and following mafic and granitic magmatic intrusions. Mig- matite in the North Dabie zone, coeval with the formation of low-Mg# adakitic intrusions in the Dabie orogen, was formed by partial melting of exhumed ultrahigh-pressure metamorphic rocks at middle crustal level. This paper argues that the partial melting of thickened lower and middle crust before mountain-root collapse needs lithospheric thinning. Based on the geothermal gradient of 6.6~C/km for lithospheric mantle and initial partial melting temperature of ~1000~C for the lower mafic crust, it can be estimated that the thickness of lithospheric mantle beneath thickened lower crust has been thinned to 〈45 km when the thickened lower crust was melting. Thus, a two-stage model for mountain-root removal is proposed. First, the lithospheric mantle keel was partially removal by mantle convection at 145 Ma. Loss of the lower lithosphere would increase heat flow into the base of the crust and would cause middle-lower crustal melting. Second, partial melting of the thickened lower crust has weakened the lower crust and increased its gravity instability, thus triggering delamination and foundering of the thickened mafic lower crust or mountain-root collapse. Therefore, convective removal and delamination of the thickened lower crust as two mechanisms of lithospheric thin- ning are related to causality.     

闸河区周边重合断裂方位分布特征及其导水趋势分析

本文应用了遥感这一先进工具,在地壳表层现实资料及地球遥感影象特征基础上,发展了遥感地质灾害方面研究新理论——重合断裂方位破裂理论,来为防治水害直接提供导水断裂趋势分布特征.     

Geochemical evidence from the Sudbury structure for crustal redistribution by large bolide impacts

Deformation and melting of the crust during the formation of large impact craters must have been important during the Earth's early evolution, but such processes remain poorly understood. The 1.8-billion-year-old Sudbury structure in Ontario, Canada, is greater than 200 km in diameter and preserves a complete impact section, including shocked basement rocks, an impact melt sheet and fallback material. It has generally been thought that the most voluminous impact melts represent the average composition of the continental crust, but here we show that the melt sheet now preserved as the Sudbury Igneous Complex is derived predominantly from the lower crust. We therefore infer that the hypervelocity impact caused a partial inversion of the compositional layering of the continental crust. Using geochemical data, including platinum-group-element abundances, we also show that the matrix of the overlying clast-laden Onaping Formation represents a mixture of the original surficial sedimentary strata, shock-melted lower crust and the impactor itself.     

Evidence of crustal ＇channel flow＇ in the eastern margin of Tibetan Plateau from MT measurements

Magnetotelluric （MT） survey has been carried out in the eastern margin of the Tibetan Plateau and its neighboring Shimian-Leshan area, Sichuan Province. Analysis of this MT data reveals that the electric structure of the Tibetan Plateau differ much from that of the Sichuan block. In general, the electric resistivity of crust beneath the Sichuan block in the east is larger than that of the eastern margin of the Tibetan Plateau in the west. The crust of the plateau is divided into upper, middle, and lower layers. The middle crust is a low resistivity layer with minimum down to 3-10Ωm about 10-15 km thick. It presumably contains partial melt and/or salt-bearing fluids with low viscosity, prone to deform and flow, producing a ＂channel flow＂ under the southeastward squeeze of the eastern Tibetan Plateau. This low-resistivity layer makes the upper crust decoupled mechanically from the lower crust. In the brittle upper crust, faults are dominated by left-lateral strike-slip and thrust motions, leading to surface rising and shallow earthquakes. The low-resistivity layer also cut the Xianshuihe-Anninghe fault zone into two sections vertically. In this region, the thicknesses of upper, middle, and lower crust vary laterally, producing a transitional zone in the eastern margin of the Tibetan Plateau characterized by thicker crust and higher elevation in the west and thinner crust and lower elevation in the east.     

岩体节理到脆性断层的形成过程

根据室内的断裂力学实验结果,对含结构面（节理,裂隙）的岩体,分别分析了其含一组节理,雁行节理,共轭节理等3种情况在受力作用下的变形破坏发展过程过程,结果表明：外力作用下的岩体,其所含的结构面将最终沿接近主应力轴的方向扩展,延伸,破坏,最后结合广东某些地区的地震断层实际资料的分析,认为地壳浅层内某些大规模的脆性断层的形成与上述焦点结构面的岩体扩展,破坏过程基本吻合。