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1.
Wu Mingxian 《中国海洋湖沼学报》1988,6(1):59-70
Transform fault delineation is important for determining the direction of plate motion during sea floor spreading. The analysis
of marine magnetic anomalies is one of the most powerful geophysical methods for this purpose. In this paper the characteristics
of the magnetic anomalies over some transform fault zones in the North Pacific and in the North Atlantic are discussed. Form
comparison of the characteristics of these magnetic anomalies over transform fault zones with those of the NE-SW anomaly zone
in the Davis Strait., the latter anomaly zone is interpreted not as the expression of a transform fault zone caused by horizontal
movement during sea floor spreading but as an anomaly zone caused by basalt and therefore is inferred to be the expression
of a fault zone produced by vertical crustal movement during volcanic activities. We discuss here the identification and correlation
of linear anomalies in the Davis Strait region, and propose our hypothesis on the spreading history of the Davis Strait. 相似文献
2.
Wu Mingxian 《中国海洋湖沼学报》1986,4(1):56-67
Magnetic data collected during several cruises in Davis Strait show north-south lineations over most of the area. The central
positive magnetic zone coincides well with a major gravity low. These results suggest that the magnetic anomalies were produced
by seafloor spreading and that the gravity low marks an extinct spreading center in Davis Strait. Comparison between the geomagnetic
polarity time-scale and dated anomalies in Labrador Sea suggests identification of anomalies 13–27 (37 to 62 MY). In southern
Davis Strait (63°N), the spreading rates are 8.4 mm/y. east of the spreading center, and 2.7 mm/y to the west. In northern
Davis Strait (66°N), the spreading rates are 4.5 mm/y east of the spreading center, and 2.1 mm/y to the west. Seafloor spreading
in Davis Strait was there-fore very asymmetrical, with decreasing rates from south to north. Spreading is interpreted as having
begun at 61–63 M and ending at 37 MY. Three fracture zones have been delineated, suggesting oblique spreading about the ridge
axis in the Davis Strait. A distinct northeast-southwest anomaly zone is interpreted as the, expression of faults caused by
volcanically-induced vertical crustal movements, and not by spreading-related horizontal crustal movement. Faulting along
this northeast-southwest anomaly zone is inferred to have occurred after the spreading and before 30 MY. The magnetic anomalies
off Cape Dyer are proposed to be different from the anomalies striking in northeast-southwest direction. The Cape Dyer anomaly
is interpreted as being formed at 58 MY while the northeast-southwest anomaly zone formed more recently.
This work was carried out at Department of Geology and Centre for Marine Geology, Dalhousie University, Halifax, N. S. Canada. 相似文献
3.
通过对华北地区1∶50万布格重力资料进行小波多尺度分析,得到自地表至莫霍面不同空间尺度范围内地质体产生的重力异常。讨论各阶小波变换细节特性及相应地质构造特征认为,华北裂陷盆地的隆起、坳陷与重力异常的高、低存在明显的对应关系,并给出了它们的下延深度。分析结果显示,华北裂陷盆地内深大断裂两侧岩石密度存在较大差异。采用帕克法反演得到华北地区莫霍界面深度在29～42 km范围内,在太行山与华北平原交界地区存在明显的地壳厚度变化梯级带。 相似文献
4.
The South China Sea locates at the convergence center of the Eurasian Plate,the Pacific Plate and the Indo-Australia plate. The Cenozoic seafloor spreading in the South China Sea Basin is an important part of the tectonic evolution of the South China Sea that records information of the continental margin tectonic history and its impact on regional geologic evolution. Magnetic data contains abundant geological structure information from the surface to deep. This paper reports magnetic data of the South China Sea. Through the conventional processing of these magnetic data,we report general results on the regional magnetic anomalies,such as the upward continuation graph,the polar magnetic anomaly map and the magnetic anomaly partition map. The magnetic anomaly field in the South China Sea is divided into eight areas,of which the characteristics are explained,and the tectonic evolution of the South China Sea is preliminarily discussed. 相似文献
5.
A new approach was taken to investigate the crustal stucture of the Kane transform and its aseismic extension, using high quality bathymetry and gravity data. The gravity signatures associated with variations in crustal thickness of the transform were isolated from the observed free-air anomaly,was continued downward to the mean depth of the crust/mantle interface and converted on to the relief onthat surface. The crustal thickness of the transform was then calculated by subtracting seawater depth from the depth of the gravity-inferred crust/mantle interface. 3-D gravity investigation results indicate that the Kane transform and adjacent areas are associated with a crust thinner than normal oceanic crust. The transform trough is largely underlain by a crust less than 4.5kin thick and in the nodal basins the crust may be as thin as 3 kin. The crust beneath the fracture zone valley is 4 - 5.5 km thick. The rift valleys on the spreading segments are also characterized by thin crust (4 - 5 km thick). Thin oceanic crust extends to 20-30 km from the transform axis,except for some localized places such as the inside comerhighs adjoining the ridge-transform intersections. These gravity-inferred results match fairly well with limited published seismic results. Thinning of the crust is mainly attributable to a thin layer 3, which in turn may be explained by the combined effects of reduced magma supply at the ends of the spreading segments and tectonic activities in the region. 相似文献
6.
山东半岛海域成矿区带划分以往研究程度较低。该文利用海域重磁资料,在研究区梳理了渤海和黄海的重磁异常特征,渤海和北黄海呈负布格重力异常,南黄海北部与之相反;渤海为正磁异常,黄海与之相反。以重磁异常为基础,基于陆域构造单元划分,对海域构造单元划分至Ⅲ级10个构造单元,海域构造单元多为陆域向海域的延伸,仅渤中坳陷和北黄海盆地为独立的海域构造单元。参照陆域成矿区带划分,以构造单元边界为界线,海域成矿区带划分至Ⅳ级6个成矿区,各成矿区特征不同,坳陷构造单元内成矿区富集油气矿产,隆起构造单元内成矿区表现为埕宁隆起富集煤矿,胶北隆起富集金、菱镁矿、煤、灰岩矿,千里隆起富集岩金、蛇纹岩、石棉、花岗石矿。 相似文献
7.
分别利用EGM2008模型和地面实测重力资料反演川滇地区构造应力场,并总结分析川滇地区构造应力场特征。结果表明,EGM2008模型和地面实测重力资料的反演结果较为一致|川滇地区构造应力场复杂,龙门山断裂带和嘉黎断裂带地区构造应力分布明显、聚集程度高,构造应力均值也较大,反映了该地区构造运动活跃,与地震历史资料相对应。 相似文献
8.
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NTDM。经模型验证,NTDM在收敛性、抑噪性和边界识别精度方面均有提升。利用NTDM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/cm3,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。 相似文献
9.
采用重力异常数据,在频率域内通过Parker-Oldenburg反演算法计算南海及邻区的莫霍面深度。通过EGM2008重力场模型联合GOCE重力场模型,计算研究区的自由空气重力异常;通过重力场分离,得到莫霍面起伏引起的重力异常,用于反演莫霍面深度。计算结果与地震剖面计算的莫霍面深度结果平均偏差1.59 km,标准偏差1.9 km。结果表明,南海及邻区的莫霍面深度分布具有明显的区域化构造特征。 相似文献
10.
莱州-安丘铁成矿带已发现大量中小型铁矿床,重磁资料在找矿过程中起到了重要作用。实践表明,按成因划分的3种铁矿床类型所对应的重磁场特征在总场尺度上难以进行有效区分,不同类型的铁矿床分布规律不甚明显。岩石物性的统计分析表明,带内发育的各类岩(矿)石具有显著的密度及磁性差异,岩浆岩密度和磁性均较高,变质岩变化范围较大,而沉积岩以"低磁低密"为特征,磁铁矿石的磁性高于其他岩(矿)石,而且铁矿石与围岩密度差较大,具规模矿体能够引起显著重力异常。利用频率域滤波方法对重磁资料进行场分离处理,将重磁异常分为区域场和局部场,断裂构造在区域场中以梯级带为主要特征,在局部场中磁铁矿床均分布在高磁异常及周边区域,沉积变质型铁矿床、岩浆融离型铁矿床、岩浆期后热液型铁矿床在重力局部异常场中具有不同的特征,对不同类型铁矿床从重磁局部异常场尺度上进行特征总结,为今后带内铁矿床勘查方向提供了参考。 相似文献
11.
凤太铅锌-金矿集区地处秦岭泥盆系贵金属-多金属成矿带西段,总体为夹持于湘子河断裂、酒奠梁断裂之间,以NWW向褶皱和NWW向断裂组合而成的近似菱形构造块体,主要出露的泥盆系为浅变质碳酸盐岩与细碎屑岩建造,东部出露的花红树坪岩体、西坝岩体和集中分布的岩脉为区内铅锌、金成矿提供了物质及热动力.典型矿床解剖结果表明:铅锌矿床受... 相似文献
12.
五莲县七宝山多金属矿位于五莲-胶南成矿带,是山东省重点勘查区和有色金属调查评价区,开展了大量工作,系统总结其多金属矿矿化特征,分析其地球物理、地球化学特征,将为开展外围找矿工作提供参考。通过总结五莲七宝山地区的重力异常特征、航磁异常特征、岩(矿)石物性特征以及地球化学特征,以及对杏山峪和红石岗矿段高精度磁测及激电中梯资料的分析对比,提出七宝山地区低阻、低磁异常带,高低阻过渡带、正负磁异常接触带附近,是找矿的重要地球物理特征标志。地球化学资料显示该区为Cu、Au、Ag等元素构成的近圆形高背景区与七宝山火山机构中心的次火山杂岩体分布范围基本一致,其他异常与已发现的多金属矿床在位置上完全吻合,说明化探异常具有效性。 相似文献
13.
随着全球油气勘探的不断深入,北大西洋极地逐渐成为油气勘探研究的前沿领域,而扬马延矿区勘探程度极低。基于中海油冰岛矿区新采集的地震及重磁资料,结合其他有关扬马延微陆块最新的研究资料,开展了扬马延微陆块的地层和构造特征分析,以及与共轭盆地的对比,建立了扬马延火山型被动陆缘远端带的构造演化模式。研究表明:位于北大西洋格陵兰与挪威之间海域的扬马延微陆块,与北大西洋两侧陆架盆地古生代-中生代地层具有共轭特征;构造呈NE-SE向展布,发育拆离断裂体系,与挪威西部陆架盆地中生界拆离断裂体系具有相似性;构造内部受岩浆侵入及喷出等强烈影响,发育向海倾斜反射层(SDR)及岩浆溢流相沉积。在上述研究基础上,探讨了扬马延微陆块与格陵兰古陆和波罗的海古陆拉断分离的构造演化过程,认为扬马延在古生代-中生代与格陵兰古陆和波罗的海古陆为一体,在经历了古生代-中生代陆内碰撞、弱伸展到陆内裂谷和陆内热沉降后,受北大西洋拉开影响,经历了古近纪和新近纪火山型被动陆缘远端带的形成演化过程,在55 Ma第一次洋中脊扩张期,与波罗的海古陆挪威陆缘盆地分离,在25 Ma第二次洋脊跃迁时期,新生洋脊扩张导致扬马延微陆块与格陵兰古陆分离,在沉积与构造上开始与北大西洋火山型被动陆缘盆地产生分异,最终扬马延微陆块成为孤立在洋壳上的一个"弃子"。本次关于扬马延微陆块的研究揭示了火山型被动陆缘远端带在岩浆活动、拆离断裂作用下,减薄-破裂的残余陆壳及内部新生洋壳的构造面貌及板块构造背景下的演化过程。 相似文献
14.
根据东天山及邻区地层、沉积建造、构造岩石组合、变形、变质、古生物分区、深部地壳结构、地球物理、地球化学特征，以康古尔塔格－黄山深断裂为界，划分了不同级别的构造单元和构造沉积相带。统计分析了２０２个金属矿床，重点研究了金、银、铜、镍、钼、铁等矿产空间分布与板块构造、碰撞带关系，划分出九个成矿带，三个成矿期，以海西中晚期最为显著。成矿与板缘构造活动带地质演化密切相关，与俯冲一碰撞带和韧性剪切带时空演化最为密切。构造分区控制的矿产成带性和构造演化形成的成矿集中期之间相互转化对该区金属矿产有重要控制作用。 相似文献
15.
基于多期绝对重力与相对重力联测资料,获取不同时空尺度的郯庐断裂带苏皖段及周边地区重力场动态变化,采用小波多尺度分解方法计算不同深度的重力变化,结合区域地质构造,从深度层次的横向变化与时间尺度的纵向变化2个方面进行分析。结果表明,研究区重力变化主要由中、上地壳密度变化或断裂构造活动引起。沿郯庐断裂带苏皖段走向断裂活动分布不均,受周边深大断裂带交切作用的影响表现出明显的分段活动特征。淮阴-响水口断裂、滁河断裂等深大活动断裂带构造活动对局部重力变化具有一定的控制作用,沿断裂带走向分布有明显的重力变化梯度带;郯庐断裂带郯城-泗县段、大别山构造带霍山-六安及江苏溧阳-镇江地区在小波细节动态变化中存在重力变化梯度带异常区,但强度不高,考虑到多条深大断裂交切于此,后期需要重点关注。 相似文献
16.
1 IntroductionThroughoutthegeologicalhistory ,almostallthetectonicplateactivities,suchasearthquakes,volcaniceruption ,andmountainbuilding ,takeplaceatactiveplateboundaries.Forexample,approxi mately 90 percentoftheearthquakesoccuratactiveplateboundaries[1 - 4 ] ,andthehighestmountainsofTibetandAndesresultfromthecontinualcollisionbetweenIndiaandAsia ,NazcaandSouthAmericaplates,respectively .Aplateboundaryisafracturethatseparatesaplatefromanother;theneighboringplatesmoverelativetooneanotherin… 相似文献
17.
The identification of fractures is of great importance in gravity and magnetic data processing and interpretation.In this study,four fracture identification methods are applied,and widely used in processing and analysis of the gravity anomaly,including vertical second derivative method,tilt derivative method,theta map method and normalized differential method,for gravity data acquired in a given area in Heilongjiang.By comparing the distribution of the zero contour or maximum contour,we summarize the application effects,and both advantages and disadvantages of each method.It is found that tilt derivative method and normalized differential method provide better effects than other two methods:the narrower anomaly gradient belt and higher identification precision of fracture or geological boundary.The inferred fractures and geological boundaries have a great match with the results obtained from geologic map and remote sensing data interpretation.Those study results have definitely provided the theoretical foundation for identifying faults and the geological boundaries. 相似文献
18.
刘代志 《地球科学与环境学报》1988,(2)
本文较全面地探讨了东南地洼区反映深部构造特点的地球物理特征(波速结构,地温分布,电性,密度,重、磁场异常),综合分析了该区地洼构造形成、演化的力源机制,讨论了地洼构造与板块构造的力源机制关系问题。 相似文献
19.
利用EGM2008地球重力场模型数据计算川西地区的水平构造应力场。结果显示,采用重力场数据可以快速获得水平构造应力场图像;龙门山断裂带及鲜水河-安宁河断裂带水平构造应力聚集程度较高,构造应力值较大,反映出这些地区地质构造运动活跃;水平构造应力方向从巴颜喀拉块体到华南地块再到川滇块体呈现顺时针方向旋转;构造应力场随着深度的增加呈逐渐减小的趋势,地震活动频率也相应降低;构造应力场等值线密集区构造运动活跃、地震活动频发,表明地震活动与构造应力聚集分布存在一定的对应关系。 相似文献
20.
基于EIGEN-6C4重力异常和ETOPO1地形数据,采用基于fan小波的相关性分析方法计算安徽及周边地区较高分辨率的各向同性岩石圈有效弹性厚度Te（effective elastic thickness）,结合区域地质构造和地球动力学背景进行讨论。结果表明,研究区Te处于5~75 km之间,大别造山带和下扬子地区为Te低值区,郯庐断裂两侧Te值相对较低,河淮盆地和苏北盆地Te值较高,Te分布反映了区域特定地质构造特征和地球动力学背景;地震活动主要分布在10~50 km Te值范围内,集中在Te低值区和Te值陡变带,表明相关区域岩石圈抵抗形变能力较弱,易于发生地震。 相似文献