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1.
The South Yellow Sea Basin is partially surrounded by the East Asian continental Meso-Cenozoic widespread igneous rocks belt. Magnetic anomaly and multi-channel seismic data both reveal the prevalent occurrence of igneous rocks. We preliminarily defined the coupling relation between magnetic anomalies and igneous rock bodies. Some igneous complexes were also recognized by using multi-channel seismic and drilling data. We identified various intrusive and extrusive igneous rock bodies, such as stocks, sills, dikes, laccoliths and volcanic edifice relics through seismic facies analysis. We also forecasted the distribution characteristics of igneous complexes. More than fifty hypabyssal intrusions and volcanic relics were delineated based on the interpretation of magnetic anomaly and dense intersecting multi-channel seismic data. It is an important supplement to regional geology and basin evolution research. Spatial matching relations between igneous rock belts and fractures document that extensional N–E and N–NE-trending deep fractures may be effective pathways for magma intrusion. These fractures formed under the influence of regional extension during the Meso-Cenozoic after the Indosinian movement. Isotopic ages and crosscutting relations between igneous rock bodies and the surrounding bedded sedimentary strata both indicate that igneous activities might have initiated during the Late Jurassic, peaked in the Early Cretaceous, gradually weakened in the Late Cretaceous, and continued until the Miocene. Combined with previous studies, it is considered that the Meso-Cenozoic igneous activities, especially the intensive igneous activity of the Early Cretaceous, are closely associated with the subduction of the Paleo-Pacific Plate.  相似文献   

2.
珠江口盆地白云凹陷内发育大量早中新世(约15.5 Ma)浅成岩浆侵入体(侵入深度<3 km).目前对其形态特征、相互关系以及岩浆侵入诱发的强制褶皱等尚缺乏系统研究.通过利用高精度三维地震资料,细致刻画了侵入体的形态、岩浆运移通道以及岩床复合体内各岩床的空间关系,定量分析了强制褶皱与侵入体的几何关系.白云凹陷内岩浆侵入体...  相似文献   

3.
由于蕴含着潜在的油气勘探和资源储藏信息,岩床复合体在全球范围内被广泛研究。本文基于南海北部三维地震资料以及南极罗斯海地区二维多道地震资料,对岩床复合体的形态特征及分布进行分析,对两个地区岩床复合体的形成时间进行判断,阐述岩床复合体的侵位机制。研究发现,岩床复合体代表性产状除了菱形、碟形及复合型外,还存在沿着层位平行侵入的板状,推测它可能是夭折了的岩床侵入体,以及由几个小型岩床堆叠而成的透镜状岩床复合体。分布上,南海北部岩床主要发育于珠江口盆地白云凹陷三维工区西部,东部只零星可见;南极西罗斯海岩床主要发育于西北角的阿黛尔盆地内。根据岩床上覆的强制褶皱结合区域构造背景,推测南海北部岩床复合体的形成时间为早中新世(15.5 Ma),海底扩张结束之时。残余岩浆将盆地内裂谷时期形成的断层作为岩浆运移的通道,并最终在断层终点处即下中新统近海相砂泥岩地层中实现侵位。南极西罗斯海岩床复合体的形成时间则非常晚,不早于5.5 Ma。该区这期岩浆活动可能与构造作用无关,而是受到冰川消融的影响。研究发现岩床复合体内部的岩床个体互相供给,即深部的大岩床为上覆浅层的小岩床提供岩浆供给,并且互相组合,形成大的岩床复合体。然而,每个岩床复合体则可能由不同的岩浆供给发育而成。  相似文献   

4.

A major phase of igneous activity of Late Oligocene to Early Miocene age affects West Kalimantan and Sarawak in northwest Borneo. The suite of igneous rocks, intruded as stocks, sills and dykes, ranges in composition from diorite to granite, the majority being granodiorite, and has geochemical characteristics similar to I‐type granitoids. The locus of magmatic activity was in the thickest part of Late Cretaceous and Early Tertiary sedimentary basins. The age of magmatism, its tectonic position and geochemistry suggest that it is related to deep crustal re‐melting and intrusion in a passive, postsubduction environment.  相似文献   

5.
An extensive suite of igneous sills was intruded into the Tertiary sedimentary section of the Jiaojiang sag,East China Sea.This suite has been well imaged offshore through 2D and 3D seismic surveys,showing a close relationship with CO2 content in nearby gas discoveries.A new observational model,which incorporates simple upward propagation,simple horizontal propagation,and transgressive propagation,was proposed to interpret these sill intrusions.In this model,the source magma of the saucer-shaped sills was injected from their lowest points near the center.The transgressive propagation can be interpreted as a combination of the vertical and horizontal propagation.Most shallow sub-volcanic intrusions in the Jiaojiang sag exhibit fingered characteristics,both vertically and horizontally.The vertical fingered propagation produced saucer-shaped sills arranged in the flower style.Along the brims of lower sills could usually be found the upper sills,which are interpreted to have formed simultaneously with or later than the lower feeder sills.In the second type,the chilled paths of the older sills were reutilized by subsequent intrusions.The horizontal fingered propagation formed sheet intrusions that exhibit groove,lobate,tubular,and crevasse splaylike geometry in plan view.In 3D view,the sheet intrusions have still preserved the lower center and higher rim that similar with the sub-rounded saucer-shaped sills.Although fracture propagation may be important,flow inflation was the key mechanism of magma intrusion.Further consideration of the mechanisms underlying sill formation may help explain the fingered characteristics of sill propagation.  相似文献   

6.
东海西湖凹陷广泛发育中新世末形成的大型反转背斜,关于背斜成因前人多认为与外力作用有关,忽视了凹陷内部结构的影响.以重磁震资料综合解释分析为基础,系统梳理中新世末反转背斜分布及其与凹陷基底结构的关系,并结合构造物理模拟实验方法探讨基底结构差异对反转背斜发育的影响.结果表明,中新世末反转背斜与高磁性火成岩基底分布呈现出明显的相关性,且均具有南北分段差异.凹陷北段火成岩基底分布在中央洼陷-反转带内,反转背斜主要在火成岩基底东缘区发育;凹陷南段火成岩基底分布在东、西两侧边缘,反转背斜主要在边缘火成岩基底内侧发育.构造物理模拟实验结果显示,在挤压背景下,压应力通过相对刚性硅胶边缘释放,控制挤压背斜褶皱的形成;表明不同岩性基底所产生的抗压强度差异能显著影响反转背斜分布.最终提出在挤压背景下,高磁性、高抗压强度的火成岩基底所引起的局部构造应力场改变是决定中新世末反转背斜强弱分布的关键因素.   相似文献   

7.
岩浆活动在沉积盆地中是非常广泛的.随着油气勘探领域的扩展,对沉积盆地火成岩及相关构造的研究愈加重要.沉积盆地火成构造是指在沉积盆地中由岩浆侵入或喷发作用形成的岩浆和围岩及上覆层变形构造的总和.当前,利用三维地震数据研究岩席的几何学与侵位机制取得了重要进展,开启了沉积盆地火成构造研究的新时代.三维地震分析是沉积盆地火成构...  相似文献   

8.
通 过地 面钻孔 、井下 开采和 磁法 勘探,发现 井 田内 赋存 有 大量 的岩 浆 岩体 ,特 别是 西二 采 区发 育岩 床 ,使该 区可采 储量 急 剧减 少,严重 影 响了 井田 采 掘 工 程的 衔 接 ,使 矿 井 生产 处 于 被 动局 面 。 通过 对 岩 浆 岩侵 入 规 律 的深 入 研究,预 测了井 田岩 床的分 布范 围和面 积,对 区域找 煤以 及为矿 井生 产和可 持续 发展具 有现 实的指 导意 义。  相似文献   

9.
The primary goals of seismic interpretation and quantification are to understand and define reservoir architecture and the distribution of petrophysical properties. Since seismic interpretation is associated with major uncertainties, outcrop analogues are used to support and improve the resulting conceptual models. In this study, the Miocene carbonates of Cerro de la Molata (Las Negras, south‐east Spain) have been selected as an outcrop analogue. The heterogeneous carbonate rocks of the Cerro de la Molata Platform were formed by a variety of carbonate‐producing factories, resulting in various platform morphologies and a wide range of physical properties. Based on textural (thin sections) and petrophysical (porosity, density, carbonate content and acoustic properties) analyses of the sediments, eleven individual facies types were determined. The data were used to produce synthetic seismic profiles of the outcrop. The profiles demonstrate that the spatial distribution of the facies and the linked petrophysical properties are of key importance in the appearance of the synthetic seismic sections. They reveal that carbonate factory and facies‐specific reflection patterns are determined by porosity contrasts, diagenetic modifications and the input of non‐carbonate sediment. The reflectors of the seismograms created with high‐frequency wavelets are coherent with the spatial distribution of the predefined facies within the depositional sequences. The synthetic seismograms resulting from convolution with lower frequency wavelets do not show these details – the major reflectors coincide with: (i) the boundary between the volcanic basement and the overlying carbonates; (ii) the platform geometries related to changes in carbonate factories, thus sequence boundaries; and (iii) diagenetic zones. Changes in seismic response related to diagenesis, switching carbonate producers and linked platform geometries are important findings that need to be considered when interpreting seismic data sets.  相似文献   

10.
Numerous traces of paleoseismic events (seismites) were established in Mesozoic–Cenozoic marine sedimentary sequences of the northern Caucasus. These traces are most prominent in the terrigenous Middle Miocene sandy–clayey sediments. Impact of seismic shocks upon the relatively weakly lithified sediments provoked distortion of the primary sedimentary structure, liquefaction of the sandy material, and injections of different morphologies (neptunic dikes and sills). The formation of jointing in sediments fostered their vertical permeability and promoted the migration of diagenetic solutions into the adjacent horizons, which stimulated the formation of subvertical carbonate bodies. The amount and intensity of seismic events varied at different stages of the accumulation of sequences and in different areas of the paleobasin. In the eastern sector of the northern Caucasus, seismic activity similar to the present-day general pattern was likely developed as early as the Middle Miocene: maximum activity in the Dagestan and its westward attenuation. Traces of seismic activity are also recorded in the Maikopian (Oligocene–Lower Miocene) and Lower–Middle Jurassic rocks.  相似文献   

11.
Three major igneous events, dated at ～1465, ～1070 and ～500 Ma, are represented in the Proterozoic of central Western Australia, yet their extent is poorly understood. The compositions of dated mafic rocks from the western Bangemall Supergroup of Western Australia have been used to establish a chemical fingerprint for the ～1465 Ma and ～1070 Ma intrusive events, and to assign sills of an unknown age to one of the two events. A similar approach has been used to identify the extent of ～500 Ma magmatism. Low-pressure fractionation or accumulation has exerted a strong influence on the chemistry of rocks from all magmatic events, but distinctive trace-element ratios (e.g. Th/Nb, Nb/Zr) and rare-earth element (REE) chemistry (e.g. Eu/Eu?, (Gd/Yb)CN) can discriminate different events. These ratios remain constant regardless of the degree of fractionation or accumulation, and reflect the chemistry of the respective mantle sources. Based on chemistry, ～500 Ma igneous rocks are not found in the Bangemall Supergroup. Neodymium model ages for ～1465 Ma sills overlap with crystallisation ages of subduction-related felsic intrusive rocks from the adjacent Gascoyne Complex, and this, combined with trace-element and REE chemistry, suggests that the mantle source for these sills underwent ～5% crustal contamination approximately 450 Ma prior to melting in a subduction zone environment. Unrealistically large amounts of contaminant are required to explain the chemistry of most ～1070 Ma sills, and their chemistry is better explained by melting of a heterogeneous mantle source, consistent with the overlap of Nd model ages and crystallisation ages. However, the relatively low εNd(T) and high 87Sr/86Sr(T), elevated light REE, Rb and Zr concentrations, and high Th/Nb of some ～1070 Ma eastern Bangemall Supergroup sills are indicative of crustal contamination. These sills are relatively depleted in chalcophile elements and platinum-group elements, consistent with coeval precipitation of sulfides and crustal contamination. The overlap in the maximum depositional age of host-rocks with the crystallisation age of some sills, the confining of most ～1465 Ma sills to older parts of the stratigraphy, and field evidence showing that some sills belonging to both the ～1465 and ～1070 Ma events were intruded into wet sediments, indicate a close temporal relationship between sedimentation and sill intrusion.  相似文献   

12.
Woodlark Island, the largest above‐sea portion of the Woodlark Rise, has an exposed basement of pre‐Miocene (?Cretaceous‐Eocene) low‐K tholeiitic basalt and dolerite, and minor sediments. The basement is unconformably overlain by Early Miocene limestone and volcaniclastic sediments and later Miocene high‐K volcanics and comagmatic intrusives. Pleistocene to Recent sediments partly blanket the Tertiary sequence. Basement low‐K tholeiites vary only slightly in composition and are interpreted as ocean floor or possible marginal basin material. The high‐K suite appears to be chemically similar to late Tertiary to Recent high‐K igneous rocks of mainland Papua New Guinea. It includes porphyritic hornblende‐, clinopyroxene‐, biotite‐ and magnetite‐bearing shoshonite, latite and toscanite, and intrusive equivalents that range from olivine normative to strongly quartz normative compositions (S1Q2 46% to 75%). Computer mixing models indicate that separation of the pheno‐crysts in the shoshonites, particularly pargasitic hornblende, is a feasible mechanism for producing the more silica‐rich monzonites and latites.

The low‐K tholeiitic basement rocks of Woodlark Island are inferred to be part of an ophiolitic slab en echelon with the Papuan Ultramafic Belt, thrust over equivalents of the Cretaceous Owen Stanley Metamorphics or, in part, onto existing oceanic crust. High‐K igneous rocks on Woodlark Island appear to form an eastward extension of a province of calcalkaline to shoshonitic volcanic and intrusive rocks, which stretches from Mount Lamington to the Louisiade Archipelago. Late‐middle Miocene high‐K magmatism at Woodlark Island is consistent with the observation that activity commenced earlier in the E and became progressively younger westwards towards mainland Papua New Guinea. Periodicity in the magmatism was apparently synchronous with major rifting episodes that formed the Woodlark Basin. The data on the Woodlark Island high‐K suite support the currently accepted. concept of delayed partial melting of a mantle source previously modified by the introduction of water and LILE from an earlier subduction zone (Johnson et al., 1978b).  相似文献   

13.
The nature and origin of the sediments and crust of the Murray Ridge System and northern Indus Fan are discussed. The uppermost unit consists of Middle Miocene to recent channel–levee complexes typical of submarine fans. This unit is underlain by a second unit composed of hemipelagic to pelagic sediments deposited during the drift phase after the break-up of India–Seychelles–Africa. A predrift sequence of assumed Mesozoic age occurring only as observed above basement ridges is composed of highly consolidated rocks. Different types of the acoustic basement were detected, which reflection seismic pattern, magnetic anomalies and gravity field modeling indicate to be of continental character. The continental crust is extremely thinned in the northern Indus Fan, lacking a typical block-faulted structure. The Indian continent–ocean transition is marked on single MCS profiles by sequences of seaward-dipping reflectors (SDR). In the northwestern Arabian Sea, the Indian plate margin is characterized by several phases of volcanism and deformation revealed from interpretation of multichannel seismic profiles and magnetic anomalies. From this study, thinned continental crust spreads between the northern Murray Ridge System and India underneath the northern Indus Fan.  相似文献   

14.
The multidisciplinary approach is used to analyze the structure of the sedimentary cover in the northern Knipovich Rift valley, Molloy Fracture Zone and synonymous basin, Svyatogor and Hovgard rises, Gorynych Hills, Litvin and Pogrebitskii seamounts, and western slope of the Spitsbergen Archipelago studied in Cruise 24 of the R/V Akademik Nikolaj Strakhov. Materials of the bathymetric survey with multibeam echo sounder, as well as continuous seismic and vertical acoustic profiling, revealed two main (NNW- and NNE-trending) systems of fractures in the neotectonic structure of the region. It was established that a system of NNE-oriented fractures, linear zones of the dominant development of keyboard deformations included, is consistent with the strike of magnetic anomalies reconstructed for this region. Tectonic aspects of the Knipovich Rift and prospects of its further development are considered. Based on the wave field pattern of continuous seismic profiling (CSP) records, four seismocomplexes indicating contrasting sedimentation settings and intense tectonic processes at different formation stages of the northern Norwegian-Greenland Sea are conditionally defined in the sedimentary cover of the study region. It was established the Molloy Fracture Zone is responsible for a system of horizontal reflectors of acoustically transparent structureless light spots (“blankings”) in the upper well-stratified part of the sedimentary section, which are characteristic of areas with ascending pore fluids. The micropaleontological study (palynomorphs of higher plants, dinocysts, planktonic foraminifers, and diatoms) revealed the presence of Miocene assemblages in sediments. Benthic foraminifers include late Paleocene-middle Eocene assemblages. The composition of rock-forming components demonstrates a directed succession of mineral-terrigenous associations from the feldspar-quartz type to mesomictic quartz-graywacke type.  相似文献   

15.
Arabian Journal of Geosciences - The increasing availability of 3D seismic data and well logs from Ash Shaer Area has provided fundamental new insights into the Miocene igneous activity and its...  相似文献   

16.
In the Yangliu Mine in Huaibei Coalfield, violent magma intrusion produced two layers of the igneous cover sills and the annular dike and caused the ejection of gas and water in the bed splitting from the surface well that destroyed the gas extraction system on the surface. The source, flow characteristics and hazard of the gas in bed splitting under igneous sills were researched via laboratory experiments, theoretical analyses and numerical simulations. The experimental results indicate that the shorter the distance from the igneous sill and the larger the thickness of the igneous sill, the greater will be the amount of the thermal evolution, the pyrolysis stoma, the coal adsorption and desorption ability and the risk of outburst, six coal samples collected at different distances from the igneous sill. The first breaking length of the igneous sill, the volume of the bed splitting, the gas pressure and flow rate in the bed splitting and the accumulative volume of the gas ejected from the surface well #2 were theoretically calculated. The laws of the bed splitting development under the igneous sills were simulated, consistent with the theoretical calculation results. The regional control and prevention technologies for coal seam gas under igneous sills were proposed and applied. Then the safety of the first-mining seam production and the gas extraction in the adjacent seam and bed splitting via the surface well was ensured, and no accidental gas and water ejection occurred.  相似文献   

17.
In order to better constrain the interpretation and the nature of the seismic reflectors, experimental measurements at high confining pressure (up to 300 MPa) and room temperature of the compressional wave velocity (Vp) on 10 samples representative of the most common lithologies along the Aurina (Ahrntal), Tures (Tauferer Tal), and Badia (Abtei Tal) Valleys profile (Eastern Alps, Italy) have been performed. For each sample, the speed of ultrasonic waves was measured in three mutually perpendicular directions, parallel and normal to the rock foliation and lineation.The main results are:(a) Good agreement between the calculated vs. measured modal compositions of the considered rocks, indicating that they were presumably equilibrated at the estimated P–T conditions; therefore, the seismic properties are representative of the crustal level indicated by the thermobarometry.(b) Measured and calculated average Vp are in good agreement, and are typical of mid-crustal level (6.0–6.5 km/s). Only the amphibolites show Vp typical of the lower crust (7.2 km/s).(c) The seismic anisotropy of metapelites is very high (12–27%), both with orthorhombic and transverse isotropy symmetry; amphibolites are transversely isotropic with an anisotropy of 8%; orthogneisses and granitoids are isotropic or weakly anisotropic.(d) The contacts between amphibolites and all other rock types may generate good reflections, provided they are not steeply inclined. Although the metamorphic foliation remains steeply inclined, discordant buried sub-horizontal igneous contacts may be detected.  相似文献   

18.
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   

19.
The Canadian Arctic Islands expose a complex network of dykes and sills that belong to the High Arctic Large Igneous Province (HALIP), which intruded volatile‐rich sedimentary rocks of the Sverdrup Basin (shale, limestone, sandstone and evaporite) some 130 to 120 million years ago. There is thus great potential in studying the HALIP to learn how volatile‐rich sedimentary rocks respond to magmatic heating events during LIP emplacement. The HALIP remains, however, one of the least well known LIPs on the planet due to its remote location, short field season, and harsh climate. A Canadian–Swedish team of geologists set out in summer 2015 to further explore HALIP sills and their sedimentary host rocks, including the sampling of igneous and meta‐sedimentary rocks for subsequent geochemical analysis, and high pressure‐temperature petrological experiments to help define the actual processes and time‐scales of magma–sediment interaction. The research results will advance our understanding of how climate‐active volatiles such as CO2, SO2 and CH4 are mobilised during the magma–sediment interaction related to LIP events, a process which is hypothesised to have drastically affected Earth's carbon and sulphur cycles. In addition, assimilation of sulphate evaporites, for example, is anticipated to trigger sulphide immiscibility in the magma bodies and in so doing could promote the formation of Ni‐PGE ore bodies. Here we document the joys and challenges of ‘frontier arctic fieldwork’ and discuss some of our initial observations from the High Arctic Large Igneous Province.  相似文献   

20.
The Gunnedah Basin, NSW, Australia, contains more than 500 Gt of coal, and has been the subject of recent coalbed methane exploration. Large areas of the basin contain igneous intrusions and large areas of coal have been heat-affected as a consequence. A detailed study has been undertaken of coal seams intersected in a cored coalbed methane exploration drillhole in which two sill-form igneous intrusions are present. Comparisons are made between coals that are unaltered and coals that have been heat-affected, using petrographic and chemical data, coal seam gas desorption data, and gas chemical analysis data.Results demonstrate that the two igneous intrusions have had a very positive effect on coalbed methane development. The gas content in a number of heat-affected coal seams within thermal aureoles above and below the sills is substantially higher than in adjacent unaffected coal seams. In addition, the intrusions have had little effect on gas quality. The coals in the heat-affected zone were found to contain gas with approximately 95% methane. The coals in the thermal aureoles were found, under the microscope, to contain characteristic micropores and slits, which collectively may serve to enhance gas adsorption capacity, permeability, and gas desorption. Gas contents below each of the sills is substantially higher than above the sill, confirming earlier results that the sills appear to have acted as a reservoir seal, during and for some time after intrusion. The background coal rank in ACM Yannergee DDH 1 is in the high-volatile bituminous range. The igneous intrusions have resulted in an increase in rank such that large areas of coal have moved into the optimal thermogenic gas generation window. This rank increase has affected a major part of the coal-bearing sequence.  相似文献   

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