盐源盆地重力场与断裂构造特征研究

以盐源盆地1∶5万实测重力数据为基础,对该区重力场进行了解释推断。由研究区大部分为第四系所覆盖,进行了深层重力异常的提取,即利用钻井资所料确定的新近系密度界面深度,采用"剥皮"技术提取古近系及以下地层的重力异常,根据剥皮后的区域布格重力异常图进行了重力异常分区,将研究区划分为三个重力异常区。研究区内已知断裂出露较少,为查明区内隐伏断裂构造,以布格重力异常、剩余重力异常、方向导数等异常图为依据,根据断裂构造所具有的重力异常特征标志划分断裂构造,推断断裂17条,其中大断裂2条,一般断裂15条,并在断裂构造的解释方面获得了新的认识。为了确定盆地内中、新生界的分布和各地层的接触关系,选择了兴隆公社-北门场东西向长剖面进行了剖面拟合计算,推测出了沿剖面方向沉积层的纵横向分布特征。     

区域重力调查在蓟县-沧州地区的应用及认识

蓟县-沧州地区进行1/25万区域重力测量取得了初步的调查研究成果。根据区域重力场特征,在该研究区划出24条断裂和4条重要梯级带。根据断裂构造分布情况和该区地质资料,对研究区进行了构造单位的划分,其划分11个III级构造单元和19个IV级构造单元。同时,还对研究区盆地构造格局与油气田的关系、断裂构造与以往地震发生点的关系进行了分析。     

松辽盆地布格重力异常小波多尺度分解与解释

松辽盆地是中国东北盆地群的代表性盆地之一。松辽盆地及其邻区的布格重力异常分布特征以北东—北北东向为 主,其次为东西向,重力场分区分块特征明显,显示了明显的拼贴构造背景,依据布格重力异常特征对研究区构造单元进 行分区,共分成松辽盆地异常区、大兴安岭重力梯级带等 5 个特征区。利用小波多尺度分解方法对松辽盆地重力场进行分 离,选择最佳的分离阶数(4 阶),随后利用对数功率谱确定每阶异常的视深度,提取区域异常,分层研究地壳顶部(D1G)、基 底(D2G,D3G)及深部密度界面(A4G)的起伏特征,共圈定基底凹陷 14 个,并绘制了研究区的 Moho 面埋深图。地球物理特征 揭示了松辽盆地的深部构造,为研究盆地油气勘探及构造演化提供了重要依据。     

青藏高原北缘重力场研究

根据实测阿尔干—老茫崖、格尔木—额济纳旗两条重力剖面获得的资料,研究了青藏高原北缘重力场特征。划分出5个二级构造单元及11条较大断裂,计算并分析了研究区内Airy重力均衡异常与新构造运动的关系。利用重震联合反演结果,浅析了地壳—上地幔构造及密度分布特点,指出研究区内莫霍界面最深处在青海哈拉湖地区,达65km,新疆阿尔干最浅,只有39km。推测北祁连褶皱带中的中祁连断裂及阿尔金断裂系是青藏高原块体的北界。     

大中条地区重磁场特征及其断裂分布与构造单元

大中条地区是我国著名的铜、金、铁矿集区,区内各类矿床的分布与该区的构造演化有关,并受构造体系、岩浆活动等地质因素控制。因此,系统研究本区的断裂分布和构造单元是预测隐伏矿床的基础。本文通过对大中条地区重、磁场特征研究,系统推断了该区断裂分布并划分了构造单元。对重、磁场特征的研究表明,布格重力异常与化极磁力异常均呈现东西分带的特征,这是大中条地区前寒武纪、中生代和新生代三期构造演化的综合反映。研究中利用重、磁位场边缘识别技术推断出11条断裂,对断裂的研究表明,大中条地区断裂以NE向和NW向为主,大多形成于元古代和中生代,多数断裂表现出多期活动的特点。综合重、磁场特征,构造演化特征及断裂分布,大中条地区可划分为4个一级构造单元和7个二级构造单元,构造单元控制了矿床的成因和分布。上述研究成果对大中条地区构造划分和矿产资源勘查提供了地球物理依据。     

利用综合地球物理资料研究大庆探区外围绥芬河七星镇剖面构造特征及油气远景

通过分析绥芬河-七星镇(简称DB3) 地球物理剖面的位场异常和一阶导数特征, 在波数域利用重力归一化总梯度及相位法进行计算并划分出12条主要断裂。利用频率域的线性反演法计算了盆地基底深度, 并划分出绥阳隆起、敦密断陷、穆棱隆起、鸡西盆地、那丹哈达隆起、勃利盆地、七台河隆起、北兴坳陷和七星镇隆起区, 剖面的重力基底深度为0.9～3.8 km。综合重力和大地电磁测深结果对剖面的9个构造分区进行分析, 并推断敦密断陷内部、鸡西盆地中部和勃利盆地南部分布有3 个油气远景区。     

内蒙古西部银根-额济纳旗盆地重力场与 断裂构造的特征

为了研究银根-额济纳旗盆地的构造特征,为该区油气资源远景调查评价提供依据,系统地收集、研究了已有的重力调查资料,分析了研究区重力场的特征及其成因,推断了研究区的断裂构造体系。研究区区域重力异常主要是由莫霍面起伏变化引起的,剩余重力异常重力高与重力低相间分布的特征,可能一方面反映了研究区凹陷与隆起分布的范围及展布特征,另一方面反映了凹陷与隆起之间发育非对称的断裂。研究区主要发育北东东向(北东向)、北西西向2组断裂,这2组断裂对基底结构、性质、隆坳格架及中生代盆地展布起重要的控制作用。基底断裂将研究区分割成多个块体,使盆地形成凹、凸相间的结构特征。     

内蒙古西部银根一额济纳旗盆地重力场与断裂构造的特征

为了研究银根一额济纳旗盆地的构造特征,为该区油气资源远景调查评价提供依据,系统地收集、研究了已有的重力调查资料,分析了研究区重力场的特征及其成因,推断了研究区的断裂构造体系。研究区区域重力异常主要是由莫霍面起伏变化引起的,剩余重力异常重力高与重力低相间分布的特征,可能一方面反映了研究区凹陷与隆起分布的范围及展布特征,另一方面反映了凹陷与隆起之间发育非对称的断裂。研究区主要发育北东东向（北东向）、北西西向2组断裂,这2组断裂对基底结构、性质、隆坳格架及中生代盆地展布起重要的控制作用。基底断裂将研究区分割成多个块体,使盆地形成凹、凸相间的结构特征。     

基于重磁多尺度边缘检测的庐枞盆地基底构造研究

庐枞盆地位于怀宁-庐江“磁高重高”区域异常带的枞阳-庐江异常区,其区域重力场特征与区域磁场特征明显。本文利用上述特征异常,采用重磁多尺度边缘检测方法,对庐枞盆地重力和航磁数据进行了边缘检测,得到庐枞盆地不同深度的密度和磁性信息及重磁异常边界。结合重磁异常分布特点进行构造格架的推断、基底隆起区划分,建立了庐枞盆地构造格架。认为庐枞盆地基底断裂有四组方向,以北东走向断裂为主;盆地包含四块基底隆起区和一块基底残块隆起区。在此基础上,分析了庐枞盆地主要矿集区与构造格架的关系,提出了“S”形重力高异常带是寻找中深部隐伏矿床的有利部位的新认识。     

青藏高原定日—木孜塔格峰地区重力场特征与断裂构造

为研究青藏高原的地下地质结构和断裂,陕西省地质调查院于2003年～2006年在定日—木孜塔格峰区进行了1∶100万区域重力调查。作者等对获得的重力资料进行了处理和分析,结合地质及其他地球物理资料,将该区布格重力场分成七个区域,描述了其主要特征并分析了其地质意义。进行了定日—木孜塔格峰剖面的重力曲线拟合计算及地质解释,获得了该区地壳结构的定量模型。识别出30条断裂,对它们进行了分类,对其中的重要断裂进行了详细解释。结果表明:重力场分区特征与地质构造分区特征对应得较好;高原边缘及内部各块体间重要的边界断裂都在重力场上有明显的显示;断裂按走向分为近东西向、北东向、近南北向等3组,其中近东西向断裂为主干断裂。     

The crustal structure of the Sahel Basin (eastern Tunisia) determined from gravity and geothermal gradients: implications for petroleum exploration

An analysis of Bouguer gravity anomaly data and geothermal gradient data obtained from bottom hole and drill stem tests temperature is used to determine the crustal structure of the Sahel Basin in eastern Tunisia and its role in the maturation and location of the large number of oil and gas fields in the region. The regional Bouguer gravity anomaly field is dominated by gradual increase in values from the northwest to southeast and is may be caused by crustal thinning as revealed by regional seismic studies. In addition, higher geothermal gradients in the same region as the Bouguer gravity anomaly maximum add an additional constraint for the existence of crustal thinning in the region. A detailed analysis of the Bouguer gravity anomaly data was performed by both upward continuation and horizontal gradients. These two techniques were combined to show that the study area consists of two structural regions: (1) the North–South Axis (NOSA)–Zeramedine region which is characterized by northwest-dipping, northeast-striking faults, thicker crust (30–31 km) and low geothermal gradients, and (2) the Mahres–Kerkennah region which is characterized by vertical, northwest-striking faults, thinner crust (28–29 km) and higher geothermal gradients. The correlation of a variety of features includes mapped and geophysically defined faults, volcanic rocks, a thinned crust and high geothermal gradients within the same location as known oil and gas fields indicate that the faults are a major factor in the location of these petroleum accumulations.     

从重力异常探讨威宁地区深部地质构造

从1：20万布格重力异常分离出来的剩余重力异常和水平梯度重力异常为主要研究对象,结合威宁地区的地质、物化探、遥感资料,揭示该区深部存在8条断裂,火山机构1个,基性-超基性侵入岩体1个。     

额尔古纳地块中生代火山岩盆地基底构造特征:来自灵泉盆地的启示

灵泉盆地布格重力异常特征表明灵泉盆地两侧重力低异常区主要为侏罗-白垩系断陷区,中部主要为基底隆起区.对布格重力异常进行向上延拓处理,结果发现深部地质体具有"东、西深,中间浅"分布特征;剩余重力异常也说明中部局部重力高主要反映基底隆起,东部和西部局部重力低主要反映侏罗-白垩系断陷.灵泉盆地基底断裂早期以北东向为主,晚期发育北西向断裂,区内还有早期近南北向和东西向断裂存在.将灵泉盆地构造单元划分为西部断陷区、中部隆起区和东部断陷区之后发现,灵泉盆地实际上是个相对隆起而不是断陷盆地,这是盆地发生构造反转作用的结果,额尔古纳地块上的其他中生代火山岩盆地普遍具有这种模式,额尔古纳地块中生代盆地基底总体上具有"南深北浅"的特点.      

重力方法在祁连山地区构造特征与岩体解释中的应用

依据地质、航磁等资料,结合实测岩石物性资料,以1∶250 000重力资料为基础对祁连山地区(张掖、刚察地区)进行综合研究。研究地质构造与地球物理特征,划分了大地构造单元,探讨了隐伏与半隐伏岩体分布。该区域经多年的重力工作,勘探面积已近3万多km²,根据重力资料研究布格重力场特征并进行分区; 对地质构造单元重新划分,对主要断裂进行探讨; 圈定隐伏与半隐伏岩体,推断其空间展布特征,并对其解释。结果表明: 祁连山地区地壳密度结构横向分区、纵向分层明显,布格重力异常场的分区特征与地质构造分区特征基本一致。结合2.5D重力剖面反演印证了新的推测结果,为综合地质、地球物理找矿提供参考。     

Application of gravity and magnetic methods for the crustal study and delineating associated ores in the western limb of Hazara Kashmir Syntaxis,Northwest Himalayas,Pakistan

The present geophysical study deals with the ores and crustal demonstration of southeastern Hazara and its adjoining areas of Azad Jammu and Kashmir, Pakistan, on the basis of terrestrial gravity and magnetic data. Tectonically, the study area lies in the Lesser Himalayas as well as to an extent in the sub-Himalaya, more specifically in the western limb of Hazara Kashmir Syntaxis. In this study, 567 gravity and 508 magnetic stations have been measured with CG-5 gravimeter and proton precession magnetometer, respectively. The collected data have been processed by applying standard corrections and then different types of maps were prepared. The ores in the area have been delineated by the qualitative interpretation of residual Bouguer anomaly and reduction to pole total magnetic intensity maps, whereas regional structures are demarcated by the Bouguer anomaly and regional Bouguer anomaly maps. The positive contour closures on the residual Bouguer anomaly map indicate the iron ore and phosphate, whereas negative contour closures are the effects of low-density material which consists of gypsum and soapstone. The pole-reduced total intensity map also shows the negative and positive contour closures almost in the same localities and confirms the residual Bouguer anomaly map. The geological model computed on the basis of Bouguer anomaly demarcated a series of faults between different rock units in the study area. The Kashmir Boundary Thrust cuts the western limb of Hazara Kashmir Syntaxis near the apex in the north of Muzaffarabad and marks the boundary between Murree Formation and carbonates of Abbottabad Formation. The gravity model also suggests that the thickness of the crust increases towards the northeast.     

东昆仑东段深大断裂的新认识

青海东昆仑东段在地质上已划定有东昆中、东昆南、东昆北、布青山南缘、温泉-哇洪山等多条深大断裂构造.以东昆仑东段开展的10个图幅1:20万区域重力调查成果--布格重力异常为基础,依据窗口平均法、水平导数等数据处理方法提取的区域场及剩余场等丰富的重力异常信息,结合航磁异常等资料,对东昆中、东昆北等断裂构造的展布位置提出了新的看法,并根据重力资料新推断断裂构造12条,提出尖山-哈莉哈德山断裂为2个一级构造单元的分界,同时通过拟合布格重力异常长剖面的定量计算方法,获取了部分深大断裂构造在东昆仑东段的产状参数.     

河北强震发生的地震地质条件与构造模式

地壳表层构造和深部构造互相制约是控制河北地区许多强震发生的必要地质条件。由此地质条件,在水平与垂直两个相互叠加的应力场作用下,使河北地区发生许多强震。这个构造-应力场模式,对华北地区许多强震的发生可能具有普遍意义。     

Satellite Gravity Anomalies and Their Correlation with the Major Tectonic Features in the South China Sea

The South China Sea (SCS) is a region of interaction among three major plates: the Pacific, Indo-Australian and Eurasian. The collision of the Indian subcontinent with the Eurasian plate in the northwest, back-arc spreading at the center, and subduction beneath the Philippine plate along Manila trench in the east and the collision along Palawan trough in the south have produced complex tectonic features within and along the SCS. This investigation examines the satellite-derived gravity anomalies of the SCS and compares them with major tectonic features of the area. A map of Bouguer gravity anomaly is derived in conjunction with available seafloor topography to investigate the crustal structure. The residual isostatic gravity anomaly is calculated assuming that the Cenozoic sedimentary load is isostatically compensated. The features in the gravity anomalies in general correlate remarkably well with the major geological features, including offsets in the seafloor spreading segments, major faults, basins, seamounts and other manifestations of magmatism and volcanism on the seafloor. They also correlate with the presumed location of continental-oceanic crust boundary. The region underlain by oceanic crust in the central part of the SCS is characterized by a large positive Bouguer gravity anomaly (220–330 mgal) as well as large free-air and residual isostatic anomalies. There are, however, important differences among spreading segments. For example, in terms of free-air gravity anomaly, the southwest section of mid-ocean has an approximately 50 km wide belt of gravity low superimposed on a broad high of 45 mgal running NW–SE, whereas there are no similar features in other spreading segments. There are indications that gravity anomalies may represent lateral variation in upper crustal density structure. For instance, free air and isostatic anomalies show large positive anomalies in the east of the Namconson basin, which coincide with areas of dense volcanic material known from seismic surveys. The Red River Fault system are clearly identified in the satellite gravity anomalies, including three major faults, Songchay Fault in the southwest, Songlo Fault in the Northeast and Central Fault in the center of the basin. They are elongated in NW–SE direction between 20±30'N and 17°N and reach to Vietnam Scarp Fault around 16°30'N. It is also defined that the crustal density in the south side of the Central Basin is denser than that in the north side of the Central Basin.     

内蒙古东部重力场特征以及寻找内生矿床的意义

依据岩石密度特征，应用布格重力异常资料，在内蒙古东部地区推断7个大型岩浆岩活动区（带）。这些岩浆岩活动区（带）控制着内蒙古自治区东部地区大部分内生矿床，也就是说每一个大型岩浆岩活动区（带）实际上是一个成矿系统。因此，应用布格重力异常资料可以推断岩浆岩活动区（带），预测内生矿床，筛选化探异常。     

Two-dimensional spatial analysis of the seismic b-value and the Bouguer gravity anomaly in the southeastern part of the Zagros Fold-and-Thrust Belt,Iran: Tectonic implications

Environmental managers and protection agencies try to assess the magnitudes of earthquakes in regions of seismic activity. For several decades they have used the seismic b-values and Bouguer anomalies for evaluating the crustal character and stress regimes. We have analyzed geostatistically data on both variables to map their spatial distributions in the southeast of the Zagros of Iran. We found a strong correlation between the distribution of the b-value and the Bouguer gravity anomaly in the region. The large Bouguer gravity anomaly values and small b-values all accord with there being a thinner crustal root and a larger concentration of stress in the center. The small to moderate Bouguer gravity anomaly values and intermediate to large b-values accord with the thicker crustal root and the smaller concentration of stress in the northeast. We conclude the southeast of the Zagros, consists of heterogeneous crust, such that accounts for its varied tectonics.