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1.
The distribution of oil and gas resources in the South China Sea and adjacent areas is closely related to the structural pattern that helped to define the controlling effect of deep processes on oil-bearing basins.Igneous rocks can record important information from deep processes.Deep structures such as faults,basin uplift and depression,Cenozoic basement and magnetic basement are all the results of energy exchange within the earth.The study of the relationship between igneous rocks and deep structures is of great significance for the study of the South China Sea.By using the minimum curvature potential field separation technique and the correlation analysis technique of gravitational and magnetic anomalies,the fusion of gravitational and magnetic data reflecting igneous rocks can be obtained,through which the igneous rocks with high susceptibility/high density or high susceptibility/low density can be identified.In this study area,igneous rocks do not develop in the Yinggehai basin,Qiongdongnan basin,Zengmu basin and Brunei-Sabah basin whilst igneous rocks with high susceptibility/high density or high susceptibility/low density are widely-developed in other basins.In undeveloped igneous areas,faults are also undeveloped the Cenozoic thickness is greater,the magnetic basement depth is greater and the Cenozoic thickness is highly positively correlated with the magnetic basement depth.In igneously developed regions,the distribution pattern of the Qiongtai block is mainly controlled by primary faults,while the distribution of the Zhongxisha block,Xunta block and Yongshu-Taiping block is mainly controlled by secondary faults,the Cenozoic thickness having a low correlation with the depth of the magnetic basement. 相似文献
2.
文章利用海南岛SOTER数据库及自动土地评价模型ALES评价结果,对海南岛4种主要母岩上发育的土壤类型、土壤性质及香蕉种植适宜性与母质的关系进行了分析。海南岛不同母岩上土壤类型的发育呈现多样性,土壤类型的分布明显受到母岩类型、成土年龄、成土环境等因素的影响。酸性火成岩上主要发育有雏形土和富铁土,基性岩上则主要是发育良好的铁铝土,碎屑岩上主要是雏形土,而海相沉积物由于土壤形成时间的差异出现了多样的土壤类型。在海南岛湿热的气候条件下,原生母岩上发育的土壤,尽管成土母岩成分各不相同,但一些土壤性质已经没有明显差别,如交换性钙、镁、钠等,部分土壤化学性质如交换性钾的含量继承了母岩特性。各种母岩上发育的土壤,在自然条件下,适宜香蕉种植的比例都很低,但基性火成岩和海积物上发育的土壤,更容易受到人为管理措施的影响,如果满足一定的技术和经济投入,海南岛热带作物的种植潜力可以得到进一步的挖掘。 相似文献
3.
TANG Huafeng ZHAO Zhigang TIAN Zhiwen LU Baoliang TANG Wu HE Kailun ZHU Chenxi WANG Pujun 《《地质学报》英文版》2021,95(1):280-293
Based on the volume magnetic susceptibility and specific gravity measurements and mineral and lithologic identification results for 540 samples,the rock type,density,and magnetic susceptibility of rocks from northern Borneo were analyzed,and the applicability of gravity and magnetic data to the lithologic identification of the Mesozoic strata in the southern South China Sea was assessed accordingly.The results show that there are 3 types and 25 subtypes of rocks in northern Borneo,mainly intermediate-mafic igneous rocks and exogenous clastic sedimentary rocks,with small amounts of endogenous sedimentary rocks,felsic igneous rocks,and metamorphic rocks.The rocks that are very strongly-strongly magnetic and have high-medium densities are mostly igneous rocks,tuffaceous sandstones,and their metamorphic equivalents.The rocks that are weakly magnetic-non-magnetic and have medium-very low densities are mostly conglomerates,sandstones,siltstones,mudstones,and coal.The rocks that are weakly magnetic-diamagnetic and have highmedium densities are mostly limestones and siliceous rocks.The Cenozoic rocks are characterized by low densities and medium susceptibilities;the Mesozoic rocks are characterized by medium densities and medium-high susceptibilities;and the pre-Mesozoic rocks are characterized by high densities and low magnetism.Based on these results and the distribution characteristics of the various rock types,it was found that the pre-Mesozoic rocks produce weak regional gravity anomalies;the Mesozoic sedimentary rocks produce negative regional gravity anomalies;whereas the Mesozoic igneous rocks produce positive regional gravity anomalies;and the Cenozoic igneous rocks produce positive regional gravity anomalies.The regional high magnetic anomalies in the southern part of the South China Sea originate from the Mesozoic mafic igneous rocks and their metamorphic equivalents;and the regional medium magnetic anomalies may be produced by the felsic igneous rocks and their metamorphic equivalents.Accordingly,the identification of the Mesozoic lithology in the southern South China Sea shows that the Mesozoic sedimentary rocks are distributed over a large area of the southern South China Sea.Thus,it is concluded that the Mesozoic strata in this area have the potential for oil and gas exploration. 相似文献
4.
Airborne gamma-ray and magnetic anomaly signatures of serpentinite in relation to soil geochemistry, northern California 总被引：2，自引：1，他引：1
Serpentinized ultramafic rocks and associated soils in northern California are characterized by high concentrations of Cr and Ni, low levels of radioelements (K, Th, and U) and high amounts of ferrimagnetic minerals (primarily magnetite). Geophysical attributes over ultramafic rocks, which include airborne gamma-ray and magnetic anomaly data, are quantified and provide indirect measurements on the relative abundance of radioelements and magnetic minerals, respectively. Attributes are defined through a statistical modeling approach and the results are portrayed as probabilities in chart and map form. Two predictive models are presented, including one derived from the aeromagnetic anomaly data and one from a combination of the airborne K, Th and U gamma-ray data. Both models distinguish preferential values within the aerogeophysical data that coincide with mapped and potentially unmapped ultramafic rocks. The magnetic predictive model shows positive probabilities associated with magnetic anomaly highs and, to a lesser degree, anomaly lows, which accurately locate many known ultramafic outcrops, but more interestingly, locate potentially unmapped ultramafic rocks, possible extensions of ultramafic bodies that dip into the shallow subsurface, as well as prospective buried ultramafic rocks. The airborne radiometric model shows positive probabilities in association with anomalously low gamma radiation measurements over ultramafic rock, which is similar to that produced by gabbro, metavolcanic rock, and water bodies. All of these features share the characteristic of being depleted in K, Th and U. Gabbro is the only rock type in the study area that shares similar magnetic properties with the ultramafic rock. The aerogeophysical model results are compared to the distribution of ultramafic outcrops and to Cr, Ni, K, Th and U concentrations and magnetic susceptibility measurements from soil samples. Analysis of the soil data indicates high positive correlation between magnetic susceptibilities and concentration of Cr and Ni. Although the study focused on characterizing the geophysical properties of ultramafic rocks and associated soils, it has also yielded information on other rock types in addition to ultramafic rocks, which can also locally host naturally-occurring asbestos; specifically, gabbro and metavolcanic rocks. 相似文献
5.
Chemical methods are generally chosen to monitor soil pollution but magnetic measurements proved to yield additional information at low cost and less time consumption. In this investigation, the novel use of rapid and non-destructive magnetic measurements to characterize Br levels in Xuzhou (China) urban roadside soils was reported. X-ray fluorescence spectrometry (XRF) was used to quantify Br in the soil samples. Data from 21 roadside soil samples confirm Br contamination, with a mean level of 4.36 mg kg−1 and a range of 2.4–8.7 mg kg−1. These values are higher than that of unpolluted soils in Xuzhou that averages 1.1 mg kg−1. Hierarchical clustering analysis shows Br in Xuzhou roadside soils is mainly from road traffic. Clear correlations between Br levels and simple magnetic parameters [mass specific susceptibility (χ
LF), susceptibility of anhysteretic remanent magnetization (χ
ARM), saturation isothermal remanence (SIRM)] are observed. The present study shows that these three magnetic parameters can be used as a proxy for Br levels in Xuzhou urban roadside soils. 相似文献
6.
The shallow intrusive bodies and lava flows emplaced within the Permian upper red unit in the Anayet Massif, represent a magmatic episode that occurred about 255 Ma (Saxonian) in the Pyrenean Axial Zone (northern Spain). Anisotropy of magnetic susceptibility (AMS) measurements, in both igneous bodies and their host rocks, allow us to infer the existence of magnetic fabrics of tectonic origin linked to the main cleavage-related folding episode. The relationship between the susceptibility axes and the field structures is the criterion that permits to differentiate normal from inverse magnetic fabrics in the igneous samples. The structural interpretation of all AMS data taken from the igneous bodies and sedimentary host rocks, is in accordance with a folding model which include: (i) flattening associated with cleavage formation during fold amplification in incompetent layers (host pelites), responsible for a magnetic lineation at high angles with respect to the regional folding axis and (ii) buckling in competent (conglomerates and igneous bodies) levels, responsible for a magnetic lineation parallel to the regional fold axes. 相似文献
7.
长江中下游成矿带是我国重要的铁铜多金属矿产资源基地,燕山期中酸性岩浆岩对铜、铁、金等各种内生金属矿床的形成起着举足轻重的作用,识别和厘定岩浆岩体特别是隐伏岩体的三维分布形态对成矿动力学研究和深部找矿预测工作都有着重要意义。我们采用重磁三维物性反演技术,获得长江中下游成矿带磁化率和密度差三维模型,根据物性与岩性对应关系,识别和分析了区内岩浆岩体三维空间结构。推测了区内存在5个主要的岩浆活动中心,探讨了岩浆流动形式与轨迹。根据重磁三维反演反映的长江中下游岩浆岩三维分布特征,结合区域莫霍面、均衡重力异常和重磁多尺度边缘检测结果,以及区域成矿背景,预测了5个找矿远景区。结果表明,重磁三维反演技术是一种行之有效的岩浆岩体识别手段,通过对反演所得磁化率、密度分布情况的分析,可识别、圈定隐伏或半隐伏岩体,并可定量获取岩体三维形态特征,从而为寻找与火山岩、侵入岩体有关的金属矿产提供指示信息。 相似文献
8.
Fragments of igneous rocks, glasses and minerals comprise 25 per cent of the studied sample of the Luna 20 soil. Basalt fragments in the Luna 20 soil are similar to basalts from the mare regions of the Moon—in that they are characterized by the presence of iron-rich olivines and pyroxenes. On the basis of the FeO contents of plagioclases, it appears possible to distinguish between the plagioclase of the mare and highland regions of the Moon. Other igneous rock fragments are anorthosite, gabbroic anorthosite and anorthositic gabbro. The most abundant rock type (75 per cent of the sample) is microbreceia. One third of the fragments of microbreccia have undergone thermal metamorphism resulting in the homogenization of phases and the development of poikioblastic and hornfelsic textures. Excluding the basalt fragments, the dominant minerals in the Luna 20 soil are anorthite (An93–98), magnesium-rich orthopyroxenes, intermediate clinopyroxenes and olivine (< Fa50). Chemically, the Luna 20 and Apollo 16 soil samples are similar, but the Luna 20 soil is slightly depleted in aluminum and calcium and enriched in iron and magnesium relative to the Apollo 16 soils. The slight difference in bulk chemistry of the two soils may be a result of the presence of a minor amount of mare material in the Luna 20 soil and its apparent absence in the Apollo 16 soils. 相似文献
9.
During the ascent, emplacement and post-emplacement deformation of igneous rocks, two or more phases of deformation that overprint
each other are often depicted. These overprints, when magnetic minerals are present, are recorded in magnetic fabric. In this
contribution, overprints are studied by means of numerical modeling, following several basic scenarios common to igneous rocks.
Biotite and amphibole that occur often together in igneous rocks are considered as carriers of the anisotropy of magnetic
susceptibility. Modeling shows that (1) a constrictional fabric with a low degree of anisotropy as commonly recorded in magmatic
rocks may result from a deformation overprint and not necessarily from an extensional/transtensional regime, and (2) that
the constrictional AMS fabrics originates from orthogonal superimposition of a deformation event on an AMS fabric inherited
from earlier magma emplacement history. Therefore, the interpretation of a constrictional fabric must be performed with caution.
Numerical modeling may provide a suitable help in strengthening the interpretation of real magnetic fabric data. 相似文献
10.
B. Antolín-Tomás T. Román-Berdiel A. Casas-Sainz I. Gil-Peña B. Oliva R. Soto 《International Journal of Earth Sciences》2009,98(2):427-441
The structural and magnetic fabric study of the Marimanha granite, Axial Zone of the Pyrenees, provides new data to characterize
the zonation and the internal structure of the pluton. The Marimanha granite intrudes Cambro–Ordovician clastic rocks and
Silurian–Devonian limestones and slates. The zonation of the low field magnetic susceptibility, consistent with the petrological
zonation of the igneous body, indicates a concentric arrangement of rock types, with more basic compositions at the external
areas. This pluton is characterized by a low susceptibility, and rock–magnetic studies indicate a majority of “paramagnetic”
samples. Magnetic foliations strike parallel to petrographic contacts and to contours of zonation of magnetic susceptibility,
and show a dominant NE–SW strike, steeply dipping towards the North. Locally, in the northern border of the pluton foliation
directions become perpendicular to petrographic contacts and depict sigmoidal trajectories. Magnetic lineations are characterized
by the predominance of NE–SW trends with shallow plunges to the NE and SW. These foliations and lineations are parallel to
the slight elongation of internal petrographic zonation. Magnetic fabric within the granitoid body and internal elliptical
shape of petrographic zonation, suggest an intrusion contemporary with a transpressional regime and NNW–SSE shortening, syntectonic
with the late stages of the Variscan orogeny. These results are in accordance with anisotropy of magnetic susceptibility studies
of others plutons in the Pyrenees. To explain the origin of the Marimanha granite we propose magma ascent through faults at
depth and emplacement by ballooning in situ at the rheological boundary between Cambro–Ordovician and Siluro–Devonian metasediments. 相似文献
11.
D.P. Moseley J.K. Pringle R.B. Haslam S.S. Egan S.L. Rogers R. Gertisser N.J. Cassidy I.G. Stimpson 《Geology Today》2015,31(3):109-115
The geology of the Snowdonia National Park in North Wales comprises a mixture of Lower Palaeozoic shallow marine sediments, acidic igneous rocks and basic intrusions of the Welsh Basin that were subsequently deformed during the Caledonian Orogeny. Thin igneous intrusions are challenging to map due to variable surface exposures, their intrusive origin, structural deformation and burial by glacial sediments. This study used a combination of traditional geological techniques, near‐surface geophysical surveys and remote sensing to detect and map a buried dolerite sheet intrusion. Both simple and mathematical analysis of magnetic anomalies and numerical modelling allowed the dolerite position, depths and target widths to be determined. Results showed that calibrated magnetic surveys can characterize buried igneous bodies in such mountainous environments. 相似文献
12.
The mid-German crystalline rise has its westernmost exposures at the western margin of the Rhine graben in the southern Pfalz
and the northern Alsace. The outcrops are made up of granitoid rocks and minor volcano-sedimentary sequences. Radiometric
ages obtained by U/Pb, Pb/Pb, Sm/Nd and Rb/Sr analyses of the igneous rocks from this area range from ∼433 to ∼325 Ma thus
covering a time span from the Silurian to the end of the lower Carboniferous. Because the investigated rocks are — according
to their chemical composition — largely related to subduction zone environments, the following three geodynamical scenarios
are postulated, always taking subduction of oceanic crust beneath the mid-German crystalline rise into account: (a) subduction
of the Rheic ocean during the Silurian from the north; (b) subduction of the Rhenohercynian ocean during the late Devonian
(∼369 Ma) from the north; (c) subduction of the Saxothuringian ocean during the lower Carboniferous (∼334 Ma) from the south. 相似文献
13.
海南省东北地区土壤环境地球化学研究 总被引：12，自引：0，他引：12
通过对表层和深层土壤微量元素的环境地球化学研究，认为研究区内土壤环境本底和现状整体良好，但母质为基性火山岩的土壤环境状况易受破坏。 相似文献
14.
Polarization and radiation measurements and microwave studies show that the planets and the great majority of asteroids in the solar system are covered by soils similar to regolith on the moon surface.The soils repesent the composition of the asteroids and the geological elements of the planets. The spectral reflectance shows a tendency of decreasing from near ultraviolet,visible to near-infrared in order of LL→L→H→H with increasing Fe^0/Fet rato and toward to absorption for Jilin,Xinyang and Zanoyang ordinary chondrites and Qinzhen enstatite chondrite recently fallen in China,The same chemical group of meteorites feature deeper absorption valleys with increasing metamorphic grade.The spectal reflectance of igneous rocks varies from strong to what is like that of H-group chondrites in order of acid→basic→ultrabasic rocks. 相似文献
15.
16.
内蒙古西部银根-额济纳旗盆地航磁
异常特征及地质意义 总被引：1，自引：0，他引：1
在对银根-额济纳旗(银-额)盆地出露的岩体的磁性特征和航磁异常特征分析的基础上,结合局部重力异常资料和前人在区域地质方面的研究成果,讨论了航磁异常与岩浆岩之间的联系,定量拟合解释了盆地东部地区的一条重磁剖面,进而探讨了岩浆岩的分布规律。研究结果表明,银根-额济纳旗盆地各类岩体磁性分布不均匀,哨马营东南侧的中性岩、银根附近的中性和酸性岩磁性较强,而其它地区出露的岩体的磁性则为弱磁性或无磁性,并且基性岩总体表现为弱磁性;区域磁异常反映了磁性基底的特征,额济纳旗西侧、苏亥图—乌力吉—苏红图一带区域磁力高异常是古元古界深变质岩系的反映,额济纳旗—绿园—特罗西滩—因格井和银根—查干德勒苏一带区域磁力低异常是前二叠系中浅变质岩系的反映;额济纳旗、哨马营北—特罗西滩、苏亥图西—因格井—乌力吉—查干德勒苏一带局部磁力高异常主要由中酸性岩所引起,哨马营—陶勒特—特罗西滩东一带局部磁力高异常主要由中性岩体所引起,绿园—务桃亥—因格井一带局部磁力高异常主要由沉积盖层中磁性物质所引起;区域性大断裂控制着银-额盆地磁性侵入岩的发育。 相似文献
17.
在对银根-额济纳旗（银-额）盆地出露的岩体的磁性特征和航磁异常特征分析的基础上,结合局部重力异常资料和前人在区域地质方面的研究成果,讨论了航磁异常与岩浆岩之间的联系,定量拟合解释了盆地东部地区的一条重磁剖面,进而探讨了岩浆岩的分布规律。研究结果表明,银根-额济纳旗盆地各类岩体磁性分布不均匀,哨马营东南侧的中性岩、银根附近的中性和酸性岩磁性较强,而其它地区出露的岩体的磁性则为弱磁性或无磁性,并且基性岩总体表现为弱磁性;区域磁异常反映了磁性基底的特征,额济纳旗西侧、苏亥图—乌力吉—苏红图一带区域磁力高异常是古元古界深变质岩系的反映,额济纳旗—绿园—特罗西滩—因格井和银根—查干德勒苏一带区域磁力低异常是前二叠系中浅变质岩系的反映;额济纳旗、哨马营北—特罗西滩、苏亥图西—因格井—乌力吉—查干德勒苏一带局部磁力高异常主要由中酸性岩所引起,哨马营—陶勒特—特罗西滩东一带局部磁力高异常主要由中性岩体所引起,绿园—务桃亥—因格井一带局部磁力高异常主要由沉积盖层中磁性物质所引起;区域性大断裂控制着银-额盆地磁性侵入岩的发育。 相似文献
18.
Maria Teresa Gómez-Pugnaire Peter Ulmer Vicente López-Sánchez-Vizcaíno 《Contributions to Mineralogy and Petrology》2000,139(4):436-457
Mafic igneous rocks are widespread in the Nevado-Filábride Complex, the lowermost metamorphic unit of the internal zones
of the Betic Cordilleras. They form intrusive, small, discontinuous bodies, predominantly dikes with subordinate small lava
flows. The entire complex underwent alpine compressional metamorphism during the Paleogene continental collision, resulting
in eclogites and blueschists in the mafic bodies and high-pressure assemblages in the intruded metasediments. Locally, weakly
metamorphosed or completely unmetamorphosed igneous rocks with the same textural features occur as patches surrounded by eclogitized
igneous rocks. The bulk rock chemistry of unmetamorphosed and completely metamorphosed mafic igneous rocks is consistent with
an alkaline to transitional tholeiitic magmatism with typical within-plate geochemical characteristics. All but a few samples
are nepheline normative and display REE and trace element characteristics typical of continental, rift-related magmatism.
This conclusion is strongly supported by the mineral chemistry of the major constituents, in particular the calcic Ti-rich
character of clinopyroxene, the lack of orthopyroxene, and the occurrence of kaersutitic amphibole. Incompatible trace element
abundances and Sr and Nd isotopes support the provenance of these magmas from a variably metasomatized previously depleted
sub-continental lithospheric mantle source.
Received: 5 July 1999 / Accepted: 28 February 2000 相似文献
19.
The dependence of the partitioning of iron and europium between plagioclase and hydrous tonalitic melt on oxygen fugacity 总被引：1，自引：0，他引：1
The dependence of iron and europium partitioning between plagioclase and melt on oxygen fugacity was studied in the system
SiO2(Qz)—NaAlSi3O8(Ab)—CaAl2Si2O8(An)—H2O. Experiments were performed at 500 MPa and 850 °C/750 °C under water saturated conditions. The oxygen fugacity was varied
in the log f
O2-range from −7.27 to −15.78. To work at the most reducing conditions the classical double-capsule technique was modified.
The sample and a C—O—H bearing sensor capsule were placed next to each other within a BN jacket to minimise loss of hydrogen
to the vessel atmosphere. By this setup redox conditions slightly more reducing than the FeO—Fe3O4 buffer could be maintained even in 96 h runs. Raman spectra showed that the BN was modified by reaction with hydrogen resulting
in a low hydrogen permeability. The partition coefficients determined for Eu at 850 °C and 500 MPa vary from 0.095 at conditions
of the Cu—Cu2O buffer to 1.81 at the most reducing conditions (C—O—H sensor). In the same f
O2 interval the partition coefficient for Fe varies from 0.55 at oxidising conditions to 0.08 at the most reducing conditions.
The partitioning of Sm, which was added as a reference for a trivalent REE, does not vary with the oxygen fugacity, yielding
an average value for D = 0.07. Lowering the temperature to 750 °C for a given f
O2 decreases the partition coefficient of Eu and increases that of Fe. Comparison with published data at 1 atm and at higher
temperatures shows that both temperature and composition of the melt have strong effects on the partitioning behaviour. As
the change of the partition coefficients in the geologically relevant f
O2 range is quite strong, element partitioning of Eu and Fe might be used to estimate redox conditions for the genesis of igneous
rocks. Furthermore, by modelling the partitioning data it is possible to extract information about the redox state of the
melt. Resulting ferric-ferrous ratios show significant differences from those predicted by empirical models.
Received: 14 October 1998 / Received: 5 March 1999 相似文献
20.
Mapping of heavy metal loadings in soils by means of magnetic susceptibility measurements 总被引：13，自引：0，他引：13
Contamination of soils with heavy metals is an issue all industrial and urban regions have to deal with. Generally, chemical methods are chosen to monitor soil pollution but measurements of magnetic susceptibility proved to yield additional information at low cost and consuming less time. We measured the magnetic susceptibility of soils which had been analysed chemically during the soil surveys of three Austrian provinces. Each anomaly of susceptibility either coincided with geogenic anomalies or indicated anthropogenic input of pollutants. Regional comparisons of susceptibility with chemical analyses revealed that susceptibility can be used as an indicator for the contents of individual pollutants in soils. This calibration of susceptibility has been successfully applied to an industrial region as well as to an urban environment. Two powerful applications of susceptibility measurements of soils are shown: the identification of polluted areas, and the detailed mapping of these areas to reveal the extent of pollution. 相似文献