华北克拉通中东部基底构造单元的重磁特征

系统收集并重新处理了华北克拉通中东部的重磁资料,利用处理结果,结合近年来华北克拉通前寒武纪结晶基底构造研究的进展,重新将华北克拉通中东部划分为2个一级重磁异常单元和7个二级重磁异常单元;重点描述了7条分划性断裂的重磁特征,特别指出中国东部重力梯度带正是华北克拉通中部带的集中表现,而郯庐断裂带和兰考～聊城～盐山～台安-大洼断裂带是燕山期陆内不同刚性块体调整的重要边界,所以也是重磁特征的变异带．据此,对华北克拉通断裂与构造单元的重磁异常特征赋予了新的地质意义．研究表明,华北克拉通现今的地球物理特征能够反映结晶基底构造,其原因是华北克拉通现今构造格局是中新生代构造继承结晶基底构造的结果．     

中国大陆东南缘主要构造带基底结构

利用中国大陆东南缘四条北西向人工地震测深剖面的初至Pg波走时,使用有限差分层析成像方法反演剖面基底速度结构,并通过初始模型选取、射线数分布、走时拟合等手段分析结果的可靠度.研究结果表明,剖面表层速度比华北克拉通的地表速度高,闽东火山断拗带地表速度普遍高于西侧的闽西南坳陷带.相邻构造带的分界线两侧均有明显的速度横向变化,剖面东段的闽东火山断拗带内的东南沿海一带,速度变化较大,地层的褶皱变形要强于西段.基底埋深自西向东呈逐渐变浅的趋势,剖面东段的闽东火山断拗带基底起伏剧烈,基底深度与闽西南坳陷带相比较浅,与闽西北隆起带相比较深.西段的闽西北隆起带基底变化较为平缓,基底深度相对较浅;闽西南坳陷带基底深度明显加深,在龙岩新泉盆地内最深接近4 km.基底形态的起伏变化揭示出东南缘基底是坳陷与隆起并存的构造特征,与研究区近代的地质构造特征相吻合.邵武—河源、政和—大埔和长乐—诏安断裂带都切割基底,其中,政和—大埔断裂4 km深度下方有比较明显的低速异常带,结合本文以及现有的研究结果,进一步确认政和—大埔断裂是不同断块构造单元的分界.     

鄂尔多斯地块深部岩石圈电性结构研究

近年来新的研究成果反应出鄂尔多斯地块岩石圈并不是一个具有深根的完整的刚性块体,尤其在鄂尔多斯北部以及河套地堑发现有大范围的下地壳-上地幔低速低阻物质,如果这一情况属实,那么人们对鄂尔多斯地块的认识将发生大的变化.为此,我们在华北克拉通西部布设了一条穿过鄂尔多斯地块、河套地堑和阴山造山带的南北向大地电磁剖面,试图通过深部电性结构的探测提供更多信息.该剖面全长约850 km,共布设54个宽频测点和17个长周期测点.二维和三维反演结果均表明:鄂尔多斯地块内部以38°N为界,南部和北部电性结构存在明显差异.鄂尔多斯地块南部地壳至上地幔150 km深度范围内整体表现为高阻,具有刚性克拉通的特征;鄂尔多斯地块北部到河套地堑之间下地壳出现低阻层,特别是鄂尔多斯北端与河套地堑接壤地段,深部存在一个规模较大的下地壳-上地幔低阻异常体,该异常体从河套地堑开始,横向上向南延伸到鄂尔多斯地块内部约200 km,纵向上从下地壳向下延伸到上地幔(约100 km深度).根据该异常体的空间特征,参考该区地震波低速异常体的分布,我们认为鄂尔多斯北部及河套地堑中下地壳到上地幔存在热物质,其原因与深部的构造活动有关(软流圈热物质上涌、侧向流动等),这一情况可能反映出鄂尔多斯地块北部岩石圈深部正处于被改造(或者破坏)阶段,这对进一步认识青藏高原东北缘与华北克拉通之间的深部关系具有一定的启示作用.     

利用爆破地震揭示华北克拉通基底的高分辨速度结构——大丰—包头折射剖面的探测结果

大丰—包头剖面以"高密度观测点距与炮距"为特点,我们在1334 km测线上获得了21炮高信噪比的地震资料.在对Pg波震相特点分析基础上利用反演方法处理、构建了基底的精细结构图像,揭示了沿剖面不同构造地块基底结构的差异.苏北盆地基底埋深4.5~9.0 km、苏鲁隆起1.5~2.0 km,基底埋深与速度结构的强烈起伏变化可视其为华北与扬子板块碰撞、挤压构造环境下形成复杂的构造格局在地震学上的体现;鲁西隆起区基底埋深浅、速度高,结构稳定;华北盆地Pg波到时滞后、视速度低,基底埋深7.0~10.km,速度结构与基底面存在局部的起伏变化.诸多现象揭示出该区为新生代沉积巨厚、规模较大的基底坳陷区.同时在盆地内不同构造单元基底结构呈局部分块、凹陷与凸起并存的构造格局,显示出新生代沉积活动显著、变化强烈、结构不稳定的构造特点;太行山前断裂、聊兰断裂是具有显著地震学标志的断裂构造带,断裂两侧基底界面呈现出"断崖式塌陷"和速度结构的强烈横向非均匀性.综合研究认为,太行山前断裂是华北地区一条重要的构造带,它的复杂性不仅体现在两侧地形地貌、地层介质的截然不同,其基底埋深及速度结构、地壳及地幔岩石圈结构均存在显著的差异,其重要的标志是太行山以东不仅地壳厚度发生了相当规模的减薄,岩石圈的厚度也明显减薄,亦即形成了华北克拉.通破坏在东西部其基底一地壳一岩石圈的结构在空间上具有明显的差异性及强烈的横向非均匀性.     

利用S波接收函数研究华南块体的岩石圈结构

本文基于跨越华夏块体至四川盆地西部的130个线性流动地震台站及其附近90个固定台网台站的观测资料,采用S波接收函数波动方程叠后偏移方法,开展了华南大陆岩石圈结构研究.成像结果显示,研究区岩石圈结构复杂,不同构造单元之间差异显著,构造边界带附近小尺度变化强烈.150 km以上的厚岩石圈主要位于四川盆地,不足100 km的薄岩石圈主要分布于川东褶皱带和华夏块体.雪峰山下方岩石圈厚度显著增加,且以雪峰山为界岩石圈结构和性质存在着显著的东西差异.结合其它地球物理观测得到的地壳-上地幔结构信息,我们提出：（1）四川盆地还保留着厚而冷的克拉通岩石圈根,且岩石圈地幔具有结构分层特征;（2）雪峰山可能是扬子克拉通与华夏块体在西南部的边界;（3）雪峰山以东区域可能经历了岩石圈的减薄和改造,且华南岩石圈的减薄与华北相似,都主体发生在东部地区,造成现今南北重力梯度带两侧强烈的结构差异.研究结果为认识华南大陆的构造演化及其深部动力学提供了地震学约束.     

Aeromagnetic anomalies uncover the Precambrian basement in the Chhattisgarh basin area,Central India

This paper presents aeromagnetic images for the Chhattisgarh basin region, in Central India, to provide a new window on Precambrian basement geology and structure. On the basis of aeromagnetic patterns, the Chhattisgarh basin is sub-divided into a northern low (negative) anomaly zone and a southern high (positive) anomaly zone. The northern portion of the main Chhattisgarh basin has been further divided into two subbasins, the Hirri sub-basin in the west, and Baradwar sub-basin in the east. A prominent negative anomaly delineates a NW-SE trending greenstone belt separating these sub-basins. Positive magnetic anomalies delineate the extent of the Dongargarh granite and equivalents, while the weak magnetic anomaly in the southeast of the Dongargarh granite and equivalents reflect granulite gneisses of the Eastern Ghat Mobile Belt. By applying the reduced-to-the-equator filter we enhanced the possible magnetic sources and structural lineaments within the Chhattisgarh basin. A new sketch map of structural elements was then compiled from aeromagnetic interpretation over the Chhattisgarh basin area. It includes possible faults, folds and an inferred lithological boundary.     

Determination of Tectonic and Crustal Structure of the Eastern Pontide Orogenic Belt (NE Turkey) Using Gravity and Magnetic Data

The Eastern Pontide Orogenic Belt is one of the most complex geodynamic settings within the Alpine belt. Subduction polarity, which is responsible for the formation of the Eastern Pontide Magmatic Arc, is still under debate because of limited geological, geophysical and geochemical data. This orogenic belt is mainly divided into three subzones depending on lithological characteristics and facies changes as in Northern, Southern and Axial Zones from North to South. These zones are separated from each other by near-vertical faults that display the block-faulting tectonic style of this belt. In this study, the tectonic and crustal structure of the Eastern Pontides, which as yet have not been prospected by using geophysical data, has been investigated with potential field data. The horizontal gradient map obtained from gravity data shows a number of steep and gentle lineaments. It seems that these lineaments E-W, NE and NW-trending correspond to major structural zones of continental crust. Additionally, The Moho depth and Curie point depth variation maps of the Eastern Pontide Orogenic Belt have been computed with the power spectral method of the radial wavenumber carried out by using the fast Fourier transform method. As a result of this method, we estimated that the depths of the Moho and Curie point varied between 29.0 ± 1.2–47.2 ± 1.9 km and 14.3 ± 0.7–27.9 ± 1.4 km, respectively. Our findings indicate that the Moho depth generally increases from north to south in the region. However, the Curie point depth level within the crust has an undulating surface, not a horizontal one.     

Geophysical evidence of the Eastern Marginal Fault of the Cheb Basin (Czech Republic)

The western part of the Bohemian Massif hosts an intersection of two regional fault zones, the SW-NE trending Oh?e/Eger Graben and the NNW-SSE trending Mariánské Lázně Fault, which has been reactivated several times in the geological history and controlled the formation of the Tertiary Cheb Basin. The broader area of the Cheb Basin is also related to permanent seismic activity of M_L 3+ earthquake swarms. The Eastern Marginal Fault of the Cheb Basin (northern segment of the Mariánské Lázně Fault) separates the basin sediments and underlying granites in the SW from the Kru?né Hory/Erzgebirge Mts. crystalline unit in the NE. We describe a detailed geophysical survey targeted to locating the Eastern Marginal Fault and determining its geometry in the depth. The survey was conducted at the Kopanina site near the Nový Kostel focal zone, which shows the strongest seismic activity of the whole Western Bohemia earthquake swarm region. Complex geophysical survey included gravimetry, electrical resistivity tomography, audiomagnetotellurics and seismic refraction. We found that the rocks within the Eastern Marginal Fault show low resistivity, low seismic velocity and density, which indicates their deep fracturing, weathering and higher water content. The dip of the fault in shallow depths is about 60° towards SW. At greater depths, the slope turns to subvertical with dip angle of about 80°. Results of geoelectrical methods show blocky fabric of the Cheb Basin and deep weathering of the granite bedrock, which is consistent with geologic models based on borehole surveys.     

中国中南地区综合地质地球物理研究

利用重、磁和天然地震资料对中南地区进行了综合地质地球物理研究.根据研究区的重、磁异常的分布特征,可将其分为4个重力异常区、3个航磁异常区.根据重力资料反演计算得到的研究区的地壳厚度在295～41 km之间,总的趋势为西厚东薄,地壳厚度与地形起伏基本上呈镜像关系.根据磁力资料计算得到的研究区居里界面在12～40 km之间变化.地震层析成像结果表明研究区内的速度分布总体上体现了纵横交错的断块特征.在纵向尺度上,江汉－洞庭盆地以及周缘造山带的上地壳结构变化不大,中地壳和下地壳则普遍受到现今构造活动的改造,以致岩石的结构发生了一定的变化.它们主要表现为低速区域的扩大,尤其是在地壳下部尤为突出,这与断陷盆地的拉张以及造山带岩石层的底侵和拆沉作用密切相关.通过对研究区地球物理场的分析计算,在研究区共提取主要断裂带34条.根据岩石层板块大地构造理论,依据岩石层结构、地壳结构和结晶基底等深部结构的不同,将研究区中板内不同构造单元——块体作为一级构造单元,块体之间的深大断裂带作为块体的边界——块体结合带,据此原则在研究区中划分出两个一级构造单元,五个二级构造单元.     

Inversion of Gravity Data for Imaging of a Sediment-basement Interface: A Case Study in the Northwestern Part of Bangladesh

Gravity data collected by the Geological Survey of Bangladesh are processed and interpreted for imaging of a sediment-basement interface over the northwestern part of Bangladesh. The observed gravity data are processed for discriminating gravitational fields contributed subtly from the shallow basement topographic feature with the twelve nodal piecewise cubic polynomial–based finite–element approach. In spectral analysis, the presence of a widely spread shallow basement feature has been detected and interpretation of gravity data using a two-dimensional gravity inversion technique indicates that its depth ranges from 0.041 km to 0.570 km relative to ground surface. In the northern part of the study area, the inferred basement configuration shows a general depression of the basement in the Takurgaon-Panchagar and Lalmonirhat districts and reaches a maximum depth of about 0.570 km. In the Nilphamari district and its southwestern part, the basement occurs at the most shallow depth due to its upliftment. However, the estimated sediment-basement interface depths are compared with the borehole and other geophysical interpretative information and are found to be consistent.     

Deep crustal structures of eastern China and adjacent seas revealed by magnetic data

Through reduction to the North Pole and upward continuation of the total field magnetic anomalies, we analyze magnetic patterns and spatial distributions of different tectonic blocks and crustal faults in eastern China and adjacent seas. Depths to the Curie isotherms are further estimated from radially averaged amplitude spectra of magnetic data reduced to the pole. Data reductions effectively enhance boundaries of regional tectonic belts, such as the Dabie ultra-high metamorphic belt, the Tanlu Fault, and the Diaoyudao Uplift. Curie depths are estimated at between 19.6 and 48.9 km, with a mean of 31.7 km. The Subei Basin and the south Yellow Sea Basin in the lower Yangtze block show relatively deep Curie isotherms, up to about 35 km in depth, whereas in the surrounding areas Curie depths are averaged at about 25 km. This implies that the lower Yangtze Block has experienced a unique tectonic evolution and/or has unique basement lithology and structures. From a regional perspective, sedimentary basins, such as the Subei Basin, the south Yellow Sea Basin, and the East China Sea Basin, normally show deeper Curie isotherms than surrounding uplifts such as the Diaoyudao Uplift and the Zhemin Uplifts. Curie isotherms also upwell significantly in volcanically active areas such as the Ryukyu Arc and the Cheju Island, confirming strong magmatic and geothermal activities at depth. Supported by National Natural Science Foundation of China (Grant Nos. 40776026 and 40876022) and National Basic Research Program of China (Grant No. 2007CB411702)     

Interpretation of Magnetic Anomalies and Estimation of Depth of Magnetic Crust in Slovakia

The magnetic map of Slovakia used in the paper was compiled as part of a project titled Atlas of Geophysical maps and profiles in 2001. The residual magnetic data were analyzed to produce Curie point estimates. To remove distortion of magnetic anomalies caused by the Earth’s magnetic field, reduction to pole transformation was applied to the magnetic anomalies using the magnetization angle of the induced magnetization. Anomalies reduced to the pole tend to be better correlated with tectonic structures. We applied a 3-km upward continuation to the residually compiled magnetic anomalies in order to remove effects of topography. The depth of magnetic dipoles was calculated by an azimuthally averaged power spectrum method for the entire area. Such estimates can be indicative of temperatures in the crust, since magnetic minerals lose their spontaneous magnetization according to Curie temperature of the dominant magnetic minerals in the rocks. The computed Curie point depths in the Slovakia region vary between 15.2 km and 20.9 km. Heat flow higher than 100 mWm⁻² occurs at the central volcanics and eastern part of Slovakia, where the Curie point depths values are shallow. The correlation between Curie point depths, heat flow and crust depth was investigated for two E-W cross sections. Heat flow and Curie point depth values are correlated with each other however, these values could not be correlated with crust depth. The Curie point isotherm, which separates magnetic and non-magnetic parts of the crust, is represented in two cross sections.     

渭河断裂深、中、浅和近地表显示

渭河断裂是渭河盆地一条重要的隐伏断裂,对渭河盆地的形成和发展乃至盆地内的地震活动都具有一定的控制作用。文中基于横跨渭河断裂的深地震反射、浅层地震反射、钻孔勘探和槽探等勘探方法取得的探测结果,从深部、中部、浅部以及近地表4个深度,给出了渭河断裂的呈现特点,即最深切割层位、不同深度的产状变化、错距大小、断裂的最新活动时代和活动期次等     

用远震接收函数研究山西地区地壳厚度变化：“晋中坡折带”及其地质意义探讨

利用山西数字地震台网中心6年的远震数据计算接收函数并进行H-k搜索,以获得台站下方的地壳厚度.结果表明, 山西地区在平遥盆地北缘的文水-晋中一线,地壳厚度存在北厚南薄差异变化的坡折带,称之为“晋中坡折带”.该带呈NEE向延伸,其南部地区地壳厚度37~40 km,北部地区厚41~45 km.本文分析认为,该坡折带代表早前寒武纪基底构造,是华北克拉通内部的重要构造边界.山西地区基底构造保存完好,地壳厚度未明显减薄.     

Investigation into regional thermal structure of the Thrace Region, NW Turkey, from aeromagnetic and borehole data

The aeromagnetic values over the study region are relatively uniform except for a few anomalies in the northeastern and southwestern areas. Analyses of aeromagnetic data were performed in NW Turkey, in order to have a look into the subsurface regional thermal structure of the region. For this purpose, power spectra, reduced to pole (RTP), and band-pass filtered anomalies were produced using geophysical techniques. Band-pass filtered data were produced from the RTP aeromagnetic anomalies to isolate near surface and undesired deep effects. Based on the aeromagnetic data interpretation, the thickness of the magnetized crust, named the Curie Point Depth (CPD), in the study area lies between 9.7 and 20.3 km. The CPD estimates in the Thrace region of Turkey indicate two shallow CPD (SCPD1 and SCPD2) zones (the Istranca Massif and the Saros Graben area). The deep CPD are located within the Thrace Basin with sediment thickness of about 9 km. The corresponding heat flow map prepared from the averaged thermal conductivities and thermal gradients from the CPD reveals the existence of one low heat flow zone (75 mW/m²) over the center of Thrace Basin, and two high heat flow zones over the Istranca Masif (100–125 mW/m²) in the northern side and Saros Graben (125–135 mW/m²) areas in the southern side of the Thrace Basin.     

Magnetic Signatures and Curie Surface Trend Across an Arc–Continent Collision Zone: An Example from Central Philippines

Ground and aeromagnetic data are combined to characterize the onshore and offshore magnetic properties of the central Philippines, whose tectonic setting is complicated by opposing subduction zones, large-scale strike-slip faulting and arc–continent collision. The striking difference between the magnetic signatures of the islands with established continental affinity and those of the islands belonging to the island arc terrane is observed. Negative magnetic anomalies are registered over the continental terrane, while positive magnetic anomalies are observed over the Philippine Mobile Belt. Several linear features in the magnetic anomaly map coincide with the trace of the Philippine Fault and its splays. Power spectral analysis of the magnetic data reveals that the Curie depth across the central Philippines varies. The deepest point of the magnetic crust is beneath Mindoro Island at 32 km. The Curie surface shallows toward the east: the Curie surface is 21 km deep between the islands of Sibuyan and Masbate, and 18 km deep at the junction of Buruanga Peninsula and Panay Island. The shallowest Curie surface (18 km) coincides with the boundary of the arc–continent collision, signifying the obduction of mantle rocks over the continental basement. Comparison of the calculated Curie depth with recent crustal thickness models reveals the same eastwards thinning trend and range of depths. The coincidence of the magnetic boundary and the density boundary may support the existence of a compositional boundary that reflects the crust–mantle interface.     

Thermal regime and amplitude of lithosphere extension in the Sirte basin, Libya: Numerical estimates in the plane basin modeling system

The GALO basin modeling system has been applied for the numerical reconstruction of the subsidence history, variations in temperature, and maturity of the organic matter of sedimentary rocks composing the main tectonic structures of Sirte Basin. The reconstruction was carried out for eight sedimentary cross sections along the profile stretching from the Cyrenaica Platform on the eastern coast of the basin to the Hun Graben on its western wall. The interval of depths for temperature calculations included the sedimentary layer, consolidated crust, and the mantle to below 100 km. This extensive depth coverage made it possible to use the analysis of the variations in the tectonic subsidence of the basin for estimating the amplitudes and duration of the events of thermal activation and extension of the lithosphere of the basin in the history of its evolution. The modeling suggests that thermal activations of the lithosphere in the Albian-Cenomanian and Oligocene-Pleistocene are common for all tectonic structures of the Sirte Basin and the Cyrenaica Platform and that a relatively high temperature regime is also characteristic of the present-day conditions in the Sirte Basin and Cyrenaica Platform. To a considerable extent, such a regime is caused by the thermal activation of the lithosphere of the basin during the last 10 Ma. The intensity of this activation is highest in the western part of the basin, where it is accompanied by the highest erosion amplitudes. The analysis of the variations in tectonic subsidence of the basement also suggests a series of intervals of lithospheric extension, which accounts for the stages of relatively rapid subsidence of the basin. Two intervals of significant extension of the lithosphere in the Upper Cretaceous and Paleocene are common for all areas within the basin. Here, the total amplitudes of the crustal extension attained 1.5 in the central part of the Sirte Basin (the Ajdabiya and Maradah troughs and Zelten and Dahra platforms), was equal to 1.3 in the Hameimat and Zallah troughs, and were minimal (1.11–1.17) in the periphery of the basin (within the Hun Graben and Cyrenaica Platform).     

秦岭造山带与沉积盆地和结晶基底地震波场及动力学响应

秦岭-大别造山带横贯中国大陆中部,并将我国东部分为南北两部;即华北克拉通和扬子克拉通.在南、北相向运动力系驱动下构成了一个极为复杂的复合、叠加构造带、成矿带和地震活动带.同时导致了该地域异常变化的沉积建造和强烈起伏的结晶基底.然而对它们形成的地球物理边界场响应,岩相和结构的异常变化尚不清晰,特别对盆山之间的耦合响应更缺乏深层动力过程的理解.为此本文通过该区榆林-铜川-涪陵长1000 km剖面的地震探测和研究结果提出：（1）沉积建造厚度变化为4~10 km,结晶基底起伏强烈,幅度可达4~6 km;（2）一系列基底断裂将该区切割为南鄂尔多斯盆地和秦岭北缘前陆盆地、秦岭-大巴造山带和南缘前陆盆地与东北四川盆地,其中前陆盆地为秦岭北渭河盆地和秦岭南通江-万源盆地;（3）秦岭造山带是北部华北克拉通向南推挤、南部扬子克拉通向北推挤下隆升的陆内山体,并构筑了其南、北前陆盆地;（4）秦岭造山带的南、北边界并非是一条边界断层,而应是包括前陆盆地在内的组合界带;（5）秦岭与大巴弧形山系源于同一深部结晶基底,即同根生.这一系列的新认识对深化理解秦岭-大巴造山带形成的深层动力过程和演化机理及厘定扬子克拉通的真实北界具有极为重要的意义.     

The ocean floor morphostructure of the Bay of Bengal (Indian Ocean) and the problem of its origin

This study is based on the geological and geophysical data obtained in the Bay of Bengal and adjacent part of the Mid-Indian Ocean Basin by different Russian scientific and industrial institutions in the 1980s and 1990s. The results of the more recent foreign investigations are also involved. The analysis of the collected data provided a new insight into the geological structure and evolution of the region indicating that a large dry-land area—the Bengal elevation—existed in the Cretaceous at the location of the present-day Bay of Bengal. During the Cretaceous, the geological evolution of this area was controlled by epicontinental sedimentation and active volcanism. In the Late Cretaceous, progressive submersion with the inception of the Central Basin took place in the region. The subsidence of the basement was accompanied by active differentiated tectonic movements in the southern part of the Bay of Bengal. As a result, the basement experienced fragmentation into blocks with the formation of horst and graben structures. The horst relics eventually submerged to the current depths in the Late Miocene–Pliocene. The maximal amplitude of basement submersion within the bay is more than 11 km.     

秦岭造山带和邻域磁异常特征及结晶基底变异分析

本文根据最新的跨越南鄂尔多斯盆地-渭河盆地-秦岭-大巴造山带-四川盆地东北缘,即榆林-咸阳-万源-涪陵综合地球物理大剖面的高精度地磁观测数据和1：10万与1：20万航磁异常资料,经数据处理和反演分析了该研究区域内地磁异常场展布特征、构造分区及结晶基底起伏.通过对采集数据的反演与研究结果分析表明,不同构造单元之间地磁异常场和结晶基底起伏均存在明显差异和分区特征.南鄂尔多斯盆地磁异常较平稳,由于燕山运动导致盆地整体抬升,其后受到了不同程度的剥蚀作用,结晶基底埋藏较浅;渭河盆地与四川盆地东北部却长期接受沉积作用,结晶基底埋藏相对较深;而秦岭-大巴造山带磁异常变化剧烈,由于其经历了长期的碰撞、挤压和陆内造山作用,地层、岩性和构造分布极不均匀,且在深部存在物质与能量的交换和运移.这一研究结果为进一步深化认识研究区域内的上地壳属性、构造格局、深层运动学与动力学过程及深部潜在资源远景提供了重要依据.