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1.
《China Geology》2021,4(4):553-570
The southern part of the Kyushu-Palau Ridge (KPR) is located at the conjunction of the West Philippine Basin, the Parece Vela Basin, the Palau Basin, and the Caroline Basin. This area has extremely complex structures and is critical for the research on the tectonic evolution of marginal seas in the Western Pacific Ocean. However, only few studies have been completed on the southern part, and the geophysical fields and deep structures in this part are not well understood. Given this, this study finely depicts the characteristics of the gravity and magnetic anomalies and extracts information on deep structures in the southern part of the KPR based on the gravity and magnetic data obtained from the 11th expedition of the deep-sea geological survey of the Western Pacific Ocean conducted by the Guangzhou Marine Geological Survey, China Geological Survey using the R/V Haiyangdizhi 6. Furthermore, with the data collected on the water depth, sediment thickness, and multichannel seismic transects as constraints, a 3D density model and Moho depths of the study area were obtained using 3D density inversion. The results are as follows. (1) The gravity and magnetic anomalies in the study area show distinct zoning and segmentation. In detail, the gravity and magnetic anomalies to the south of 11°N of the KPR transition from high-amplitude continuous linear positive anomalies into low-amplitude intermittent linear positive anomalies. In contrast, the gravity and magnetic anomalies to the north of 11°N of the KPR are discontinuous and show alternating positive and negative anomalies. These anomalies can be divided into four sections, of which the separation points correspond well to the locations of deep faults, thus, revealing different field-source attributes and tectonic genesis of the KPR. (2) The Moho depth in the basins in the study area is 6–12 km. The Moho depth in the southern part of KPR show segmentation. Specifically, the depth is 10–12 km to the north of 11°N, 12–14 km from 9.5°N to 11°N, 14–16 km from 8.5°N to 9.5°N, and 16–25 km in the Palau Islands. (3) The KPR is a remnant intra-oceanic arc with the oceanic-crust basement.which shows noticeably discontinuous from north to south in geological structure and is intersected by NEE-trending lithospheric-scale deep faults. With large and deep faults F3 and F1 (the Mindanao fault) as boundaries overall, the southern part of the KPR can be divided into three zones. In detail, the portion to the south of 8.5°N (F3) is a tectonically active zone, the KPR portion between 8.5°N and 11°N is a tectonically active transition zone, and the portion to the north of 11°N is a tectonically inactive zone. (4) The oceanic crust in the KPR is slightly thicker than that in the basins on both sides of the ridge, and it is inferred that the KPR formed from the thickening of the oceanic crust induced by the upwelling of deep magma in the process of rifting of remnant arcs during the Middle Oligocene. In addition, it is inferred that the thick oceanic crust under the Palau Islands is related to the constant upwelling of deep magma induced by the continuous northwestward subduction of the Caroline Plate toward the Palau Trench since the Late Oligocene. This study provides a scientific basis for systematically understanding the crustal attributes, deep structures, and evolution of the KPR.©2021 China Geology Editorial Office.  相似文献   

2.
《China Geology》2021,4(4):571-584
The Philippine Sea is the largest marginal sea in the Western Pacific Ocean and is divided into two parts by the Kyushu-Palau Ridge (KPR). The western part is the West Philippine Basin, and the eastern part consists of the Shikoku and Parece Vela basins. Based on surveyed data of massive high-resolution multibeam bathymetric data and sub-bottom profiles data collected from the southern section of the KPR from 2018 to 2021, this paper analyzes the topographic and geomorphological features, shallow sedimentary features, and tectonic genesis of the southern section of the KPR, obtaining the following conclusions. The southern section of the KPR has complex and rugged topography, with positive and negative topography alternatingly distributed and a maximum height difference of 4086 m. The slope of seamounts in this section generally exceeds 10° and is up to a maximum of 59°. All these contribute noticeably discontinuous topography. There are primarily nine geomorphological types in the southern section of the KPR, including seamounts, ridges, and intermontane valleys, etc. Among them, seven independent seamount groups are divided by five large troughs, forming an overall geomorphological pattern of seven abyssal seamount groups and five troughs. This reflects the geomorphological features of a deep oceanic ridge. Intramontane basins and intermontane valleys in the southern section of the KPR are covered by evenly thick sediments. In contrast, sediments in ridges and seamounts in this section are thin or even missing, with slumps developing locally. Therefore, the sediments are discontinuous and unevenly developed. The KPR formed under the control of tectonism such as volcanic activities and plate movements. In addition, exogenic forces such as underflow scouring and sedimentation also play a certain role in shaping seafloor landforms in the KPR.©2021 China Geology Editorial Office.  相似文献   

3.
There were more expounding to north—west (west) trend fault and north\|east trend fault within Qiangtang Basin, North Part of Tibet, in the past literature. With increasing of geophysical exploration data, nearly east\|west trend structure began to be taken note to. Since the year of 1995, by a synthetic study to geophysical and geological data, that south\|north trend faulted structures are well developed. These structures should be paid much more attention to, because they have important theoretical meaning and practical significance.1 Spreading of south\|north faulted structure belt According to different geological and geophysical data, the six larger scale nearly south\|north faulted structure belt could be distinguished within the scope of east longitude 84°～96° and near Qiangtang Basin. The actual location of the six belts are nearly located in the west of the six meridian of east longitude 85°,87°,89°,91°,93°,95° or located near these meridian. The six south\|north faulted structure belts spread in the same interval with near 2° longitude interval. The more clear and much more significance of south\|north trend faulted structure belts are the two S—N trend faulted structure belts of east longitude 87° and 89°. There are S—N trend faulted structure belts in the west of east longitude 83°,81°, or near the longitudes. The structure belts spreading features,manifestation,geological function and its importance, and inter texture and structure are not exactly so same. The structure belts all different degree caused different region of geological structure or gravity field and magnetic field. There is different scale near S—N trend faulted structure belt between the belts.  相似文献   

4.
A 3-D structural model of the Caribbean-South American plate boundary was constructed by gravity modeling. The model was constrained by four wide-angle seismic refraction sections, Moho depth estimations from receiver functions, and additionally seismological hypocenters, surface geology, and geodynamic information. Density values were calculated from empirical velocity-density functions, and mineralogical-chemical composition considering specific P/T conditions. We tested different structural models for Western and Eastern Venezuela. In the final model, the fit of the measured and modeled gravity fields for a long Caribbean slab in Western Venezuela was better than the fit obtained for a short one. This interpretation is consistent with the constraining data. The slab is interpreted to extend further to the south beneath Northern Colombia and culminates in the area of the seismic cluster of the Bucaramanga nest. The modeling estimates a slab dip angle under Maracaibo and Mérida Andes of 15°, which increases to 32° below 100 km depth. The dip direction of approx. N150°E ± 5 increases lightly eastward. In Eastern Venezuela, considering its short wavelength, lineaments analyzed from gravity data (by curvature methods and Euler deconvolution) seem to be related to shallow structures and density contrast in the Serranía del Interior and not from a deep detached slab beneath the continental crust. It is deduced from modeling results that this slab configuration has a very small influence on the gravity field. The slab was modeled according to the subduction-transform propagation model with purely westward subduction and a slab break off along a vertical dip-slip tear through the lithosphere.  相似文献   

5.
The 85°E Ridge extends from the Mahanadi Basin, off northeastern margin of India to the Afanasy Nikitin Seamount in the Central Indian Basin. The ridge is associated with two contrasting gravity anomalies: negative anomaly over the north part (up to 5°N latitude), where the ridge structure is buried under thick Bengal Fan sediments and positive anomaly over the south part, where the structure is intermittently exposed above the seafloor. Ship-borne gravity and seismic reflection data are modelled using process oriented method and this suggest that the 85°E Ridge was emplaced on approximately 10–15 km thick elastic plate (Te) and in an off-ridge tectonic setting. We simulated gravity anomalies for different crust-sediment structural configurations of the ridge that were existing at three geological ages, such as Late Cretaceous, Early Miocene and Present. The study shows that the gravity anomaly of the ridge in the north has changed through time from its inception to present. During the Late Cretaceous the ridge was associated with a significant positive anomaly with a compensation generated by a broad flexure of the Moho boundary. By Early Miocene the ridge was approximately covered by the post-collision sediments and led to alteration of the initial gravity anomaly to a small positive anomaly. At present, the ridge is buried by approximately 3 km thick Bengal Fan sediments on its crestal region and about 8 km thick pre- and post-collision sediments on the flanks. This geological setting had changed physical properties of the sediments and led to alter the minor positive gravity anomaly of Early Miocene to the distinct negative gravity anomaly.  相似文献   

6.
The geological and geophysical data primarily on the structure of the upper sedimentary sequence of the northern Knipovich Ridge (Norwegian-Greenland Basin) that were obtained during Cruise 24 of the R/V Akademik Nikolai Strakhov are considered. These data indicate that the recent kinematics of the northern Knipovich Ridge is determined by dextral strike-slip displacements along the Molloy Fracture Zone (315° NW). This stress field is superimposed by a system related to rifting and latitudinal opening of rifts belonging to the ridge proper. Thus, the structural elements formed under the effect of two stress fields are combined in this district. Several stages of tectonic movements are definable. The first stage (prior to 500 ka ago) is marked by the dominant normal faults, which are overlain by the lower and upper sedimentary sequences. The second stage (prior to 120–100 ka ago) is characterized by development of normal and reverse faults, which displace the lower sequence and are overlain by the upper sequence. Both younger and older structural features reveal peaks of tectonic activity separated by intermediate quiet periods 50–60 ka long. The stress field of the regional strike-slip faulting is realized in numerous oblique NE-trending normal and normal-strike-slip faults that divide the rift valley and its walls into the segments of different sizes. Their strike (20°–30° NE) is consistent with a system of secondary antithetic sinistral strike-slip faults. The system of depressions located 40 km west of the rift valley axis may be considered a paleorift zone that is conjugated at 78°07′ N and 5°20′ W with the NW-trending fault marked by the main dextral offset. The stress field that existed at this stage was identical to the recent one. The rift valley axis migrated eastward to its present-day position approximately 2 Ma ago (if the spreading rate of ～0.7 cm/yr is accepted). The obtained data substantially refine the understanding of the initial breakup of continents with the formation of oceanic structural elements. The neotectonic stage is characterized by combination of different stress fields that resulted in the formation of a complex system of tectonic structural units, including those located beyond the recent extension zone along the rift axis of the Knipovich Ridge. The tectonic deformations occurred throughout the neotectonic stage as discrete recurrent events.  相似文献   

7.
西太平洋典型边缘海盆的岩浆活动   总被引：1，自引：0，他引：1  
在发育有全球最大、最复杂的弧—沟—盆体系的西太平洋地区,集中了全球75％左右的边缘海盆(弧后盆地).根据磁异常条带年龄,这些边缘海盆可粗略分为3个扩张幕.主要根据DS-DP,ODP和IODP计划实施以来所获得的成果,结合其他海洋调查航次研究成果,系统阐述了分属3个扩张幕的西菲律宾海盆(第一扩张幕)、南海—四国海盆(第二扩张幕)和冲绳海槽(第三扩张幕)—马里亚纳海槽内的岩浆活动特点.西菲律宾海盆(扩张时代为65～35 Ma BP)从原先的赤道位置迁移至现今的位置,其内存在如似正常洋中脊玄武岩(NMORB)、洋岛玄武岩(OIB)及弧火山岩等多种岩石类型,其地球动力学背景分别与弧后扩张、地幔柱及火山弧等背景有关,其复杂的构造演化样式需要进一步研究;四国海盆(扩张时代为27 ～ 15 Ma BP)是由古伊豆—小笠原—马里亚纳弧(IBM)裂解形成的,其内除发育正常(N)—富集(E)的洋中脊玄武岩(NMORB-EMORB)外,还在扩张停止的同时出现了板内火山作用,形成了中K-超K碱性玄武岩.四国海盆的扩张模式并没有从岩石学和地质年代学角度进行明确制约,板内火山作用的地球动力学背景也不甚清楚.南海(扩张时代为32～15.5 MaBP)是由来自华南地块的一些微陆块向东南裂离后的海底扩张所形成,并在海底扩张后2 ～8 Ma出现板内火山作用,截止目前,并没有获取到洋壳基底样品,主要获取到了南海海山似OIB的玄武岩,未来需要从岩石学和地质年代学角度对南海海底扩张动力学和时代以及扩张期后的板内火山作用动力学背景进行进一步制约.马里亚纳海槽(扩张时代为5 Ma BP至今)为一年青的洋内弧后盆地,其北段处于裂解增进阶段,其内出露有似MORB(中南段)及介于似MORB与似岛弧岩石之间过渡类型的玄武岩(增进端);虽然在扩张时代上与马里亚纳海槽相当,但冲绳海槽(扩张时代为4 Ma BP至今)为一陆缘、初生弧后盆地,从西南往东北方向,不同区段处于不同的伸展发育阶段,西南段出露有似MORB岩石,中段岩石主要为玄武质岩石和流纹质岩石组成双峰组合,而东北段为中酸性火山岩.正在活动的马里亚纳海槽与冲绳海槽的岩浆作用研究应和其伴随的火山岛弧及其相邻的海沟处正在俯冲的洋壳板块结合起来,完整理解板块俯冲输入(subduction input)与弧及弧后输出(volcanic output)之间的关系,这将为揭示西太平洋地区构造演化提供重要证据.即将在西太平洋地区实施的IODP 349 ～ 352航次,为我国科学家提供了研究西太平洋地区构造演化的契机.  相似文献   

8.
The northern Kyushu-Palau Ridge (KPR), remnant conjugate arc of the Izu-Ogasawara (Bonin)-Mariana (IBM) active arc, is dominated by basalt-andesite except for the Komahashi-Daini Seamount where acidic plutonic rocks of 38 Ma were recovered. These mafic to intermediate volcanics are produced by the rifting volcanism in the proto-IBM arc associated with spreading of the Shikoku Basin. The HFSE and HREE contents and ratios of these volcanics indicate enriched source mantle composition compared to recent volcanic front. The LILE ratios exhibit similar characteristics to reararc volcanism of the recent Izu arc, and some enriched volcanics exhibit high abundance of sediment melt inputs. Based on these observations and compilations of the published data set, the replacement event of the wedge mantle under the IBM arc occurred two times. The first event occurred between 45 and 38 Ma, with Pacific type mantle being replaced by depleted Indian type mantle. The second event occurred between 36 and 25 Ma, enriched mantle flowed from reararc side. The slab component during the proto-IBM arc rifting was a similar characteristic to recent reararc volcanism of the Izu arc, and sediment melt added in a local area.  相似文献   

9.
A geophysical survey in the eastern Gulf of Aden, between the Alula–Fartak (52°E) and the Socotra (55°E) transform faults, was carried out during the Encens–Sheba cruise. The conjugate margins of the Gulf are steep, narrow and asymmetric. Asymmetry of the rifting process is highlighted by the conjugate margins (horst and graben in the north and deep basin in the south). Two transfer fault zones separate the margins into three segments, whereas the present‐day Sheba Ridge is divided into two segments by a transform discontinuity. Therefore segmentation of the Sheba Ridge and that of the conjugate margins did coincide during the early stages of oceanic spreading. Extensive magma production is evidenced in the central part of the western segment. Anomaly 5d was identified in the northern and southern parts of the oceanic basin, thus confirming that seafloor spreading in this part of Gulf of Aden started at least 17.6 Ma ago.  相似文献   

10.
We interpreted marine seismic profiles in conjunction with swath bathymetric and magnetic data to investigate rifting to breakup processes at the eastern Korean margin that led to the separation of the southwestern Japan Arc. The eastern Korean margin is rimmed by fundamental elements of rift architecture comprising a seaward succession of a rift basin and an uplifted rift flank passing into the slope, typical of a passive continental margin. In the northern part, rifting occurred in the Korea Plateau that is a continental fragment extended and partially segmented from the Korean Peninsula. Two distinguished rift basins (Onnuri and Bandal Basins) in the Korea Plateau are bounded by major synthetic and smaller antithetic faults, creating wide and considerably symmetric profiles. The large-offset border fault zones of these basins have convex dip slopes and demonstrate a zig-zag arrangement along strike. In contrast, the southern margin is engraved along its length with a single narrow rift basin (Hupo Basin) that is an elongated asymmetric half-graben. Analysis of rift fault patterns suggests that rifting at the Korean margin was primarily controlled by normal faulting resulting from extension rather than strike-slip deformation. Two extension directions for rifting are recognized: the Onnuri and Hupo Basins were rifted in the east-west direction; the Bandal Basin in the east–west and northwest–southeast directions, suggesting two rift stages. We interpret that the east–west direction represents initial rifting at the inner margin; while the Japan Basin widened, rifting propagated southeastward repeatedly from the Japan Basin toward the Korean margin but could not penetrate the strong continental lithosphere of the Korean Shield and changed the direction to the south, resulting in east–west extension to create the rift basins at the Korean margin. The northwest–southeast direction probably represents the direction of rifting orthogonal to the inferred line of breakup along the base of the slope of the Korea Plateau; after breakup the southwestern Japan Arc separated in the southeast direction, indicating a response to tensional tectonics associated with the subduction of the Pacific Plate in the northwest direction. No significant volcanism was involved in initial rifting. In contrast, the inception of sea floor spreading documents a pronounced volcanic phase which appears to reflect asthenospheric upwelling as well as rift-induced convection particularly in the narrow southern margin. We suggest that structural and igneous evolution of the Korean margin, although it is in a back-arc setting, can be explained by the processes occurring at the passive continental margin with magmatism influenced by asthenospheric upwelling.  相似文献   

11.
尼日尔Termit盆地主要发育早白垩世和始新世-渐新世两个裂陷旋回,其起源于不同的动力学背景和运动学机制,相应表现出不同的盆地性质。其中古近纪始新世-渐新世第二裂陷旋回受区域挤压应力环境下的非洲板块内部局部应力释放控制,具有逃逸盆地的性质,在盆地内部表现为典型走滑伸展特征。该旋回在第一期NW-SE控盆断裂基础上发育了NNW-SSE断裂体系,盆地整体呈现地堑地垒和半地堑结构,北部为双断结构地堑,南部为西断东超多米诺半地堑结构。古近系断裂的斜向拉张作用形成了大量雁列式正断层,以软连接方式相连,在二级构造单元内发育了大量构造调节带,分为同向型、对向型和背向型3大类,以同向叠覆型、对向平行型和背向叠覆型为主,成为Termit盆地最主要的构造调节带样式。古近纪始新世-渐新世第二裂陷旋回及其构造样式控制了盆地沉积体系,在始新世Sokor1初始裂陷期形成了三角洲湖泊沉积体系、渐新世-早中新世Sokor2深陷期沉积了湖相泥岩,形成了盆地主力储盖组合。同时,该旋回的构造调节作用形成了大量断块和断鼻/断背斜构造,成为Termit盆地的主要圈闭类型。渐新世-早中新世的深陷期导致断层沟通白垩系成熟烃源岩,在盆地内发生广泛的垂向和侧向运移,该时期断层的活动强度决定了古近系油气分布和富集程度。Sokor1和Sokor2段中下部岩性圈闭及Sokor2段成藏组合是Termit盆地的下步勘探领域。  相似文献   

12.
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.  相似文献   

13.
The West Philippine basin (WPB) is a currently inactive marginal basin belonging to Philippine Sea plate, which has a complex formation history and various crust structures. Based on gravity, magnetic and seismic data, the tectonics in West Philippine basin is characterized by amagnma spreading stage and strike slip fractures. NNE trending Okinawa-Luzon fracture zone is a large fracture zone with apparent geomorphology and shows a right-handed movement. The results of joint gravity-magnetic-seismic inversion suggest that the Okinawa-Luzon fracture zone has intensive deformation and is a transform fault. Western existence of the NW trending fractures under Ryukyu Islands Arc is the main cause of the differences between south and north Okinawa Trough. The Urdaneta plateau is not a remained arc, but remnant of mantle plume although its lava chemistry is similar to oceanic island basalt (OIB).  相似文献   

14.
The Bohai Bay Basin is a region where part of the North China Craton has been thinned and destroyed. It has experienced two periods of crustal thinning that occurred during the Cretaceous and Paleogene, but investigations of its Mesozoic and Cenozoic lithospheric thermal structure are limited. Therefore, in this study,the distributions of mantle heat flow, crustal heat flow, and Moho temperatures during the Meso-Cenozoic are calculated based on analyses of the thermal history of the Bohai Bay Basin. The results indicate that the ratio of mantle heat flow to surface heat flow peaked during the late stages of the early Cretaceous and during the middle to late Paleogene. The corresponding mantle heat flow was more than 65% of the surface heat flow. Moho temperatures reached three peaks: 900-1100℃ in the late stages of the early Cretaceous;820-900℃ in the middle to late Paleogene; and(in the Linqing Depression, Cangxian Uplift, and Jizhong Depression) 770-810℃ during the early Neogene. These results reveal that the Bohai Bay Basin experienced significant geological change during the Cretaceous, including the transformation of lithospheric thermal structure from "cold mantle and hot crust" before the Cretaceous to "hot mantle and cold crust" after the Cretaceous. The results also indicate that the basin experienced two large-scale rifting events.Therefore, this work may provide the thermal parameters for further investigations of the geodynamic evolution of eastern China.  相似文献   

15.
The main features of the volcanic and nonvolcanic passive margins of the North and Central Atlantic are considered. The margins are compared using rather well-studied reference tectonotypes as examples. The conjugate margins of the Norwegian-Greenland region and the margins of West Iberia and Newfoundland are chosen as tectonotypes of volcanic and nonvolcanic margins, respectively. The structural and magmatic features of the margins and their preceding history are discussed. A complex of interrelated attributes is shown for each tectonotype. The Norwegian-Greenland region close to the Iceland plume is distinguished by narrow zones of stretched continental crust, rapid localization of stretching with breakup of the continent, a high rate of subsequent spreading, and intense magmatism with the formation of a thick new crust at the margin and the adjacent oceanic zone. The Iberia-Newfoundland region, remote from the plumes, is characterized by wide zones of stretched continental crust, long-term and diachronous prebreakup extension propagating northward, extremely restricted mantle melting during rifting and initial spreading, and frequent occurrence of ancient crustal complexes and serpentinized mantle rocks at the margin. Crustal faults and a thin tectonized oceanic crust appear along the margin under conditions of slow spreading. A model of hot and fast spreading with a high degree of melting in the mantle is applicable to the Norwegian-Greenland region, whereas a model of cold and slow amagmatic rifting with a long pre-breakup stretching and thinning of the lithosphere is appropriate to the Iberia-Newfoundland margins. The differences in the development of the margins is determined by the interaction of many factors: deep temperature, rheology of the underlying lithosphere, heterogeneities in the previously formed crust, and the duration and rate of stretching. All of these factors can be related to the effect of deep plumes and propagation of the extension zone toward the segments of the cold Atlantic lithosphere. Both types of margins also reveal similar features, in particular asymmetry. It is suggested that the rotation forces superimposed on the general tectonomagmatic pattern controlled by plumes could have been the cause of structural asymmetry.  相似文献   

16.
西太平洋边缘构造特征及其演化   总被引：1，自引：1，他引：0       下载免费PDF全文
李学杰  王哲  姚永坚  高红芳  李波 《中国地质》2017,44(6):1102-1114
西太平洋边缘构造带是地球上规模最大最复杂的板块边界,以台湾和马鲁古海为界,自北往南大致可以分为3段。北段是典型的沟-弧-盆体系,千岛海盆、日本海盆及冲绳海槽均为典型的弧后扩张盆地。中段菲律宾岛弧构造带为双向俯冲带,构造复杂,新生代经历大的位移和重组,使得欧亚大陆边缘的南海、苏禄海和苏拉威西海成因存在很大的争议。南段新几内亚—所罗门构造带是太平洋板块、印度—澳大利亚及欧亚板块共同作用的结果,既有不同阶段的俯冲、碰撞,也有大规模的走滑与弧后的扩张,其间既有新扩张的海盆,又有正在俯冲消亡的海盆。台湾岛处于枢纽部位,欧亚板块在此被撕裂,南部欧亚大陆边缘南海洋壳沿马尼拉海沟俯冲于菲律宾岛弧之下,而北部菲律宾海洋壳沿琉球海沟俯冲欧亚大陆之下。马鲁古海是西太平洋板块边界又一转折点,马鲁古海板块往东下插于哈马黑拉之下,往西下插于桑义赫弧,形成反U形双向俯冲汇聚带,其洋壳板块已基本全部消失,致使哈马黑拉弧与桑义赫弧形成弧-弧碰撞。  相似文献   

17.
Our research focuses on Holocene tectonics in a broad area surrounding the junction between the active NW–SE trending Husavik-Flatey transform fault (HFF) and the N–S Gudfinnugja normal fault (GF), an exceptional example of onshore transform-ridge intersection. We mapped 637 minor and major faults, and measured the dip-slip and strike-slip offset components on the major faults. We also mapped 1016 individual tension fractures, as well as opening directions on the most reliable ones. The results indicate that this portion of the HFF comprises major right-stepping segments, with both normal and right-lateral strike-slip components, linked by local normal faults. The entire GF always shows pure dip-slip normal displacements, with a strong decrease in offset at the junction with the HFF. Fissure opening directions are in the range N45°-65°E along the HFF, N90°E along the GF, and N110°E within the area south of the HFF and west of the GF. Fault kinematics and fissure openings suggest a displacement field in good agreement with most of present-day GPS measurements, although our data indicate the possible long-term Holocene effects of the superimposition of magma-related stresses on the regional tectonic stresses. The HFF and the GF work together as a structural system able to accommodate differential crustal block motion, and possibly past dyke intrusions.  相似文献   

18.
The Niquelândia layered basic-ultrabasic complex is one of several similar Precambrian massifs that constitute a discontinuous, north-trending chain 300 km long through the central Brazilian Shield in the State of Goiás. Modeling of the positive gravity anomaly associated with the complex indicates that the complex constitutes a westward-dipping slab that extends no deeper than 6 km. This model is similar to that obtained for the Barro Alto complex, the next massif to the south. The Niquelândia and Barro Alto complexes occur on a hinge line or gradient in the regional gravity field marked by paired Bouguer anomalies: residual highs to the west, lows to the east. The massifs may indicate a suture in the central Brazilian Shield marked by vast layered intrusions emplaced in continental rocks at the onset of an episode of rifting. Subsequent compression thrust remnants of the intrusions eastward, an event that may have accompanied the closing of an ancient ocean.  相似文献   

19.
<正>Exploration and development experience show that there is obvious oil gravity difference between the southern part and northern part of the"M1"reservoir in the Fanny oil field in the slope of the Oriente Basin,Ecuador.The American Petroleum Institute Gravity(API) values of oils in the northern part are higher than the one in the southern part of the Fanny oil field,with the values of 20°and 10.0°-13.0°,respectively.So the primary purpose of this study was to analyze the heavy oil characteristics of biodegradation and the oil-oil correlation according to the biomarker data and theδ~(13)C signature of oil samples from T block.The results of the hydrocarbon gas chromatography fingermark and the inversion attribute characteristics indicated that there are fluid compartments between the"M1"reservoir of Fanny south.Finally,the models of oil-gas accumulation under the control of multiple-activities of complicated fault systems,as well as the origin of heavy oil,are contended.The early stage oils from the western part of the basin were biodegraded heavily in varying degrees in the whole basin,and the later stage oils were derived from the southern part in a large scale and were mature and lighter.Generally,oil mixing is the primary control of net oil properties,such as API gravity in Oriente Basin.We therefore predicted that the API gravity variation of oil pools radically depends on the injection amount of the later stage oil.Because of the shale barrier in the"M1"reservoir of Fanny south,the later stage hydrocarbon could not pass through and contribute to increase the oil API value.  相似文献   

20.
Songliao Basin, the largest Mesozoic intracontinental nonmarine basin in eastern China, initiated during the latest Jurassic as a backarc extensional basin; rifting failed and thermal cooling controlled subsidence through the early Late Cretaceous. Integrating 2-D and 3D reflection seismic and borehole data with regional geological studies, we interpret sedimentary sequence and structural patterns of the Coniacian-Maastrichtian fill of Songliao Basin as defining a retroforeland basin system developed after 88 Ma (marked by the T11 unconformity in the basin), including (1) significant increase in the thickness of the Nenjiang Formation eastward towards orogenic highlands of the Zhangguangcai Range and the convergent continental margin; (2) a shift of detrital provenance in the basin from north to southeast; and (3) propagation of E-W shortened structures, increasing eastward in amplitude, frequency, and degree of inversion toward the orogen. During latest Cretaceous, foreland basin fill progressively deformed, as the foredeep evolved to a wedge-top tectonic setting, marked by the basin-wide T04 unconformity within the upper Nenjiang Formation at 81.6 Ma. Much of the basin was brought into the orogenic wedge and eroded by the end of the Cretaceous. Late Jurassic/Early Cretaceous backarc rifting of uncratonized basement comprised of accreted terranes likely facilitated and localized the foreland. Synrift normal faults reactivated and extensively inverted as thrust faults are prominent in the eastern 1/3 of the basin, whereas folds developed above detachments in shaley early post-rift strata dominate the western 2/3 of the basin. Songliao foreland development likely was driven by changing plate dynamics and collision along the Pacific margin after 88 Ma.  相似文献   

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