中国东部海区及邻域区域构造图的编制方法及地质构造单元划分

我国东部海区及邻域1:1 000 000地质地球物理系列图将于2008年底出版,区域构造图是其中的主要专业图件之一。讨论了该专业图件的编图方法、地质构造单元的划分方法和主要地质构造单元。首次对黄海东海区进行了全面剥皮编图,剥去了Q+N₂地层。对于沉积盆地用等厚度线表示出了新生界的厚度。地质构造单元划分方法是以板块构造理论为指导并以现今的构造特征为主要划分依据。板块内构造单元的划分是在总结国内外多种构造单元划分方法的基础上进行了修改完善,完成了对我国东部海区及邻域的地质构造单元的划分。区内一级构造单元为板块(太平洋板块、欧亚板块和菲律宾海板块),二级构造单元为构造域(东亚大陆构造域、东亚大陆边缘构造域和西太平洋构造域)。西太平洋构造域主要包括太平洋板块的西部及菲律宾海板块。欧亚板块在该区的部分可分为东亚大陆边缘构造域和东亚大陆构造域。东亚大陆边缘构造域由日本琉球岛弧、冲绳海槽弧后盆地、日本海弧后盆地等次级构造单元构成。东亚大陆构造域在该区内由中朝地块、扬子地块、华南地块等次级构造单元构成。各地块又可划分出盆地、隆褶带、隆起区等多个次一级地质构造单元。最低一级的地质构造单元为凸起和凹陷。     

Middle to Late Cenozoic tectonic events in south and central Palawan (Philippines) and their implications to the evolution of the south-eastern margin of South China Sea: Evidence from onshore structural and offshore seismic data

Using recently gathered onland structural and 2D/3D offshore seismic data in south and central Palawan (Philippines), this paper presents a new perspective in unraveling the Cenozoic tectonic history of the southeastern margin of the South China Sea. South and central Palawan are dominated by Mesozoic ophiolites (Palawan Ophiolite), distinct from the primarily continental composition of the north. These ophiolites are emplaced over syn-rift Eocene turbidites (Panas Formation) along thrust structures best preserved in the ophiolite–turbidite contact as well as within the ophiolites. Thrusting is sealed by Early Miocene (∼20 Ma) sediments of the Pagasa Formation (Isugod Formation onland), constraining the younger limit of ophiolite emplacement at end Late Oligocene (∼23 Ma). The onset of ophiolite emplacement at end Eocene is constrained by thrust-related metamorphism of the Eocene turbidites, and post-emplacement underthrusting of Late Oligocene – Early Miocene Nido Limestone. This carbonate underthrusting at end Early Miocene (∼16 Ma) is marked by the deformation of a seismic unit corresponding to the earliest members of the Early – Middle Miocene Pagasa Formation. Within this formation, a tectonic wedge was built within Middle Miocene (from ∼16 Ma to ∼12 Ma), forming a thrust-fold belt called the Pagasa Wedge. Wedge deformation is truncated by the regionally-observed Middle Miocene Unconformity (MMU ∼12 Ma). A localized, post-kinematic extension affects thrust-fold structures, the MMU, and Late Miocene to Early Pliocene carbonates (e.g. Tabon Limestone). This structural set-up suggests a continuous convergent regime affecting the southeastern margin of the South China Sea between end Eocene to end Middle Miocene. The ensuing structures including juxtaposed carbonates, turbidites and shallow marine clastics within thrust-fold belts have become ideal environments for hydrocarbon generation and accumulation. Best developed in the Northwest Borneo Trough area, the intensity of thrust-fold deformation decreases towards the northeast into offshore southwest Palawan.     

西太平洋边缘海盆的形成与演化

从地球深部地幔流动引起的地质作用出发，结合裂谷的发展演化规律，认为地幔向东（或南东）的蠕散和流动促使亚洲大陆边缘地壳拉伸、变薄以致破裂，由大陆裂谷发展至弧后裂谷，形成西太平洋边缘海盆。最后提出边缘海盆发展演化的4个阶段，即：新生阶段（郯庐裂谷系）、幼年阶段（冲绳海槽）、青壮年阶段（日本海）和成熟阶段（南海）。     

南海北部陆缘构造属性研究进展

南海北部陆缘位于特提斯与古太平洋两大构造域的叠合部位,构造特征十分复杂,其构造属性一直是国内外学者争论的焦点,从主动陆缘到被动陆缘,火山型被动陆缘到非火山型被动陆缘等均有表述。南海复杂的形成机制以及东、西部构造差异性所引起的地球物理、岩浆活动等认识的异同,是造成南海北部陆缘构造属性认识差异的主要原因。通过与全球典型地区的比较研究,进一步加强对南海形成演化过程分析,开展大洋钻探与多学科综合分析,揭示南海海盆的多期扩张与多盆张裂特征,是认识南海北部陆缘构造属性的关键。探讨了南海三叉裂谷张裂模式,初步认为南海第1次扩张具有非火山型被动陆缘性质,第2次扩张具有火山型陆缘性质。     

渤海、黄海和东海的构造性质与演化

渤海、黄海、东海的性质与发展是不同的。渤海和黄海是内陆海,是由于地幔物质的上拱,地壳弯曲断裂而成。东海是一个边缘海,是由于 菲律宾海板块向亚洲板块之下插入,在大陆岩石圈的基础上形成的。它们现在的构造格局基本上是在晚上新世或早更新世奠定的。     

Volcanogenic complexes of the Sea of Okhotsk and the Sea of Japan (Comparative analysis)

Several coeval volcanogenic complexes indicating synchronous volcanic events in the Sea of Japan and the Sea of Okhotsk are defined. Volcanics from different-age complexes of the Sea of Okhotsk show many features in common and are attributed to the Pacific type of calc-alkaline series. They were formed in geodynamic settings of the active continental margin and point to its origination on the continental crust of the fragmented Asian continent margin. The volcanic rocks developed in the Sea of Japan reflect different rifting stages. The initial stage was marked by an eruption of calc-alkaline lavas (Paleocene-Eocene complex). At the stage of the marginal-sea spreading, erupted volcanics of the middle Miocene-Pliocene complex were melted from the depleted mantle and magmatism terminated by an eruption of postspreading Pliocene-Holocene volcanics melted from the enriched mantle EM I. Along with the differences, the magmatism in the Sea of Japan and Sea of Okhotsk has some features in common. In both cases, the sialic component of the lithosphere substantially influenced the magma generation.     

Comparison between the magnetic and petrological characteristics of the peridotites from the gorringe ridge and the peridotites from the mid-ocean ridges

The purpose of our work was to obtain the most possible detailed information about the composition, concentration, and structural features of the magnetic minerals contained in the rock to reveal the differences in the magnetic properties of the peridotites under various circumstances of the mantle magmatism and different conditions of metamorphism. To do this, we examined and analyzed the magnetic and petrographic characteristics of four collections of oceanic and alpinotype spinel peridotites. The main object for comparing the magnetic characteristics was the Gorringe ridge, which lies in the eastern part of the Atlantic Ocean. The peridotite samples from the Gorringe ridge differ from the other collections in many magnetic parameters: I _n , χ, Q, I _rs /I _s , H _c , H _cr , and H _m . The principal question of our work was to clarify the nature of the Earth’s crust where the Gorringe ridge formed. This subject was studied many times in the literature, but the researchers did not reach a common opinion. In accordance with our data, the spinel peridotites from the Gorringe ridge represent a subcontinental lithosphere mantle of the Iberian continental margin. During the metamorphism, the formation of magnetite occurred in the peridotites of the Gorringe ridge in several stages and had a regressive character. Our investigations explain the results of the analysis of the anomalous magnetic field over the Gorringe ridge, which is characterized by sharp roughness and high intensity of the local signchanging anomalies.     

基于独立成分分析的马里亚纳弧后地幔源区特征研究

对采自太平洋洋中脊(277组)、印度洋洋中脊(159组)、马里亚纳海槽(53组)、马里亚纳岛弧(39组)、中南劳海盆(72组)共600组玄武岩数据进行了独立成分分析,从Sr-Nd-Pb五维同位素比值空间提取出占样本方差99％的3个独立成分(IC1,IC2,IC3),并利用这3个独立成分(ICs)与微量元素比值之间的相关...     

两种不同类型大陆边缘的初步研究

１９８６年１０月－１９８７年５月,中国第三次南极考察暨首次环球科学考察的实测重力资料表明,太平洋型活动陆缘重力异常面貌复杂,空间异常变化剧烈,处于极度不均衡状太民。用ｓｉｎｘ／ｘ法反演了 莫氏面深度,利用水层和地壳引起的垂直引力之和与实测的空间异常之差反演了软流层顶界的深度。     

东海陆架盆地南部中生代构造演化与原型盆地性质

东海陆架盆地南部夹持于欧亚板块、太平洋板块与印度板块之间,是发育在前中生代基础之上的中、新生代叠合盆地。其构造演化受古太平洋板块俯冲及特提斯-喜马拉雅构造域的联合影响,经历了印支末期基隆运动、燕山期渔山和雁荡运动的叠加改造。结合浙闽隆起带中生代火成岩事件、盆地构造变形、沉积学的一些证据,通过海陆对比研究,认为东海陆架盆地南部早-中三叠世可能为面向古太平洋的被动大陆边缘盆地;晚三叠世-侏罗纪古太平洋板块已对中国大陆有较强的俯冲作用,东海陆架盆地及南部原型盆地为活动大陆边缘弧前盆地;白垩纪受控于滨海断裂表现为活动大陆边缘走滑拉分盆地;古新世-始新世火山岛弧向东移动,东海陆架变为弧后裂谷盆地。     

Genesis of the lithosphere of the Iceland region (North Atlantic) according to geophysical data

The geothermal and geomagnetic data on the Iceland region are mapped. On the basis of the analysis of geological, tectonic, geothermal, and geomagnetic data and on the information on the age and character of the volcanism at the European and Greenland rifting margins, the principal evolution stages of the Iceland region are substantiated. The modeling estimation of the rates of thermal subsidence of the Reykjanes and Kolbeinsey ridges and of the Greenland-Iceland and Iceland-Faeroes sills shows their more than 20% difference. The different rates of thermal subsidence of the structures are caused by various effects of hot matter of the mantle plume, its volume, and the different genesis of the lithosphere. The formation of the lithosphere of Iceland Island, besides the plate and plume tectonics, involved the thermophysical processes of the transformation of the lithosphere of continental genesis. This is confirmed by the analysis of the spreading rates, basalt age, and the data of the geochemical and isotope studies of volcanic rocks. The numerical modeling performed points to the presence of an additional heat source related to the plume hot matter in the Iceland region (Iceland Island, 30 mW/m²; the Reykjanes and Kolbeinsey ridges, 15 mW/m²), which conforms to the data of magnetotelluric geochemical studies.     

Late Mesozoic–Cenozoic sedimentary basins of active continental margin of Southeast Russia: paleogeography,tectonics, and coal–oil–gas presence

Various settings took place during the Late Mesozoic: divergent, convergent, collisional, and transform. After mid-Jurassic collision of the Siberian and Chinese cratons, a latitudinal system of post-collision troughs developed along the Mongol-Okhotsk suture (the Uda, Torom basins and others), filled with terrigenous coal-bearing molasse.The dispersion of Pangea, creation of oceans during the Late Jurassic are correlated to the emergence of the East Asian submeridional rift system with volcano-terrigenous coal-bearing deposits (the Amur-Zeya basin). At that time, to the east there existed an Andean-type continental margin. Foreland (Upper Bureya, Partizansk, and Razdolny) and flexural (Sangjiang-Middle Amur) basins were formed along the margin of the rigid massifs during the Late Jurassic to Berriasian.During the Valanginian-mid-Albian an oblique subduction of the Izanagi plate beneath the Asian continent occurred, producing a transform margin type, considerable sinistral strike slip displacements, and formation of pull-apart basins filled with turbidites (the Sangjiang-Middle Amur basin).The Aptian is characterized by plate reorganization and formation of epioceanic island arcs, fore-arc and back-arc basins in Sakhalin and the Sikhote-Alin (the Alchan and Sangjiang-Middle Amur basins), filled with volcanoclastics.During the mid-Albian a series of terranes accreted to the Asian continental margin. By the end of the Albian, the East Asian marginal volcanic belt began to form due to the subduction of the Kula plate beneath the Asian continent. During the Cenomanian–Coniacian shallow marine coarse clastics accumulated in the fore-arc basins, which were followed by continental deposits in the Santonian–Campanian. From the Coniacian to the Maastrichtian, a thermal subsidence started in rift basins, and continental oil-bearing clastics accumulated (the Amur-Zeya basin).Widespread elevation and denudation were dominant during the Maastrichtian. This is evidenced by thick sediments accumulated in the Western Sakhalin fore-arc basin.During the Cenozoic, an extensive rift belt rmade up of a system of grabens, which were filled with lacustrine–alluvial coal–and oil-bearing deposits, developed along the East Asian margin.     

Geological structures of ridges with relation to the definition of three types of seafloor highs stipulated in Article 76

The ridge like seafloor highs with various geological origins can be classed into mid-ocean ridges,transverse ridges related to transform faults,hot spot/mantle plume originated ridges,microcontinent rifted from major continent,intra-plate arc formed by interaction of two oceanic plates,and tectonic ridges uplifted by later tectonic activity.Those ridges moved towards the convergent continental margins along with the underlain plate drifting and formed so-called accreted ridges commonly trending at a high angle to the continental margins.At divergent continental margins,the continental crusts were extended and thinned accompanying with magmatism,which formed high terrains protruding or parallel to the coastal line.The ridges worldwide have various origins and the crustal thicknesses and structures of them are diversity.The crusts beneath the microcontinents,and the transverse ridges along the transform margin,and the seafloor highs beside the passive continental margins are continental,while the crusts of other ridges are oceanic.Article 76 of the United Nations Convention on the Law of the Sea (UNCLOS) has classed the seafloor highs worldwide into three legal categories,namely oceanic ridges,submarine ridges and submarine elevations,for the purpose to delineate the outer limit of the coastal States’ continental shelf beyond 200 nautical miles.To define the categories of the legal seafloor highs to which the ridges with various geological origins belong,the continuities in morphology and geology including the rock types,crustal structures,origins and tectonic setting of the ridges and the coastal States’ land mass with its submerged prolongation should be taken into account.If a ridge is continuous both in morphology and geology with the coastal States’ land mass and its submerged prolongation,it is a submarine elevation stipulated in Article 76.If it is discontinuous in morphology,the ridge should be regarded as oceanic ridges.If a ridge is continuous in morphology but discontinuous in geology with the coastal States’ land mass and its submerged prolongation,then it is a submarine ridge as stipulated in Article 76.     

Great Japan earthquake of March 11, 2011: Tectonic and seismological aspects

The tectonic and seismological aspects of the Great Japan Earthquake, which occurred on March 11, 2011 (M _w = 9.0), at the Pacific margin of the northeastern part of Honshu Island, are discussed. The structure and seismotectonic data, seismicity, and the reccurence rate of the great (M ≥ 7.6) earthquakes throughout history and in modern times are represented. It is shown that the reccurence rate of the great events is about 40 years, and that of megaearthquakes is 1000 years or more. A seismic gap of about 800 km in length is found in the region under study, located to the south of latitude 39° N and full of aftershocks to the megaearthquake of March 11, 2011. This event is probably connected with the deep thrust along the Benioff zone and its structural front (Oyashio nappe at the middle Pacific continental slope). The aftershock sequences of this megaearthquake and the Sumatra-Andaman (2004) megaearthquake are compared. It is found that several of their key characteristics (the number of aftershocks, the magnitude of the strongest aftershock, and the time of its occurrence) for 25 days are comparable for both cases with a significant difference in the energies of aftershock processes. A probable scenario for the origination of a repeated shock with M ∼ 8.0 in the Japan Trench is discussed.     

Preliminary Analysis of Seismic Risk in Taiwan Strait and Study on Feasibility of Construction of Tunnel Across the Strait

The collision between Eurasian and Pacific plates along the eastern margin of the Asian continent resulted in formation of a series of island-arcs, one of which is the Taiwan Island-arc, and the Taiwan Straits is a foreland basin in the continent-arc collision zone. The Quaternary fine-grained sediments occur evenly in the upper part of the basin, and the Pliocene deposits in the lower part. The stepped faults run in the deposits, indicating that the tectonic movement tended to weaken after the Pliocene. Strong seismic zones of Taiwan Island released large amount of plate overthrust-collision compressive stress and have their screen and prevention roles for the straits. Only the intersections between offshore NW-trending transform-like faults and seashore NE-trending faults on the southern and northern terminations of the Island are prone to strong earthquakes. The possibility of occurrence of M ≥ 6 earthquake should be very low in the area for the planned future tunnel. Moreover, the seismic intensity is rapidly attenuated from the surface downward. Thus, the seismic intensity for the tunnel under the seabed will be much lower. In seismotectonic view, the construction of tunnel is feasible.     

Mud volcanoes and gas vents in the Okhotsk Sea area

Gas emissions from mud volcanoes on Sakhalin Island and water-column gas flares arising from cold seeps in the Okhotsk Sea appear to be related. They are likely activated by tectonic movements along the transform plate boundary separating the Okhotsk Sea Plate from the Eurasian and Amur plates. Gas vents (flares) and methane anomalies occur in the waters offshore Sakhalin Island, along with NE-SW-trending mounds and fluid escape structures on the seafloor. The intersection of the NE-striking transverse faults on land with the Central Sakhalin and Hokkaido-Sakhalin shear zones apparently determines the sites of mud volcanoes, a pattern that continues offshore where the intersection with the East Sakhalin and West Derugin shear zones determines the sites of the submarine gas vents.     

Geochemistry and palaeo-oceanography of metalliferous and pelagic sediments from the Late Cretaceous Oman ophiolite

Metalliferous and pelagic sediments are exposed within and above the extrusive successions of the Upper Cretaceous Oman ophiolite which, on the basis of mostly geochemical evidence, is believed to have formed in an incipient marginal basin setting located above a NE-dipping subduction zone. The ophiolitic extrusives document various volcano-tectonic settings which include the axial zones of a spreading ridge, fault-controlled seamounts and off-axis volcanic edifices. Most of the Fe, Mn and trace metal-enriched sediments studied are interpreted as precipitates formed by oxidation of solutions derived from high-temperature sulphide-precipitating vents. The trace element content (e.g. REE and Sr) was largely scavenged from seawater. The sediments are similar to the dispersed metalliferous sediments on the flanks of modern spreading ridges, and the ‘basal’ sediments of DSDP wells and of other ophiolite complexes (e.g. Troodos, Cyprus).Distinctive mound structures located low in the lavas are attributed to percolation of sulphide-rich solutions into already deposited metalliferous oxide sediments. The resulting iron-silica rock was probably originally precipitated as ferruginous silicates.Major massive sulphides formed off-axis at the base of intermediate-basic edifices of volcanic arc affinities. Fe, Mn and trace metal enrichment in the sediment cover of a flat-topped seamount of axial lavas is interpreted as a dispersion halo around the largest massive sulphide orebody which is situated 5 km away (Lasail). Small massive sulphide bodies are common in the axial lavas particularly along major seafloor fault zones. The metalliferous sediments, locally precipitated near these vents, are ferromanganiferous, but trace metal-depleted.The metalliferous and pelagic sediment cover of the extrusive successions, generally, documents waning hydrothermal input after volcanism ended in the area.A model is discussed in which the ophiolite was created at a spreading axis above a subduction zone dipping away from the Arabian continental margin. With progressive subduction this crust approached the margin. Initially, calcareous sediment accumulated above the calcite compensation depth (CCD), but then non-calcareous radiolarites were deposited as the ophiolitic crust approached the continental margin where the CCD was higher and marginal upwelling possibly enhanced productivity. As the edge of the Arabian continental margin entered the trench, the over-riding ophiolite was regionally uplifted allowing short-lived chalk accumulation above the CCD. This was followed by volcaniclastic deposition related to the tectonic emplacement.     

Variations in Moho and Curie depths and heat flow in Eastern and Southeastern Asia

The Eastern and Southeastern Asian regions witness the strongest land–ocean and lithosphere–asthenosphere interactions. The extreme diversity of geological features warrants a unified study for a better understanding of their geodynamic uniqueness and/or ubiquity from a regional perspective. In this paper we have explored a large coverage of potential field data and have detected high resolution Moho and Curie depths in the aforementioned regions. The oldest continental and oceanic domains, i.e. the North China craton and the Pacific and Indian Ocean have been found thermally perturbed by events probably linked to small-scale convection or serpentinization in the mantle and to numerous volcanic seamounts and ridges. The thermal perturbation has also been observed in proximity of the fossil ridge of the western Philippine Sea Basin, which shows anomalously small Curie depths. The western Pacific marginal seas have the lowest Moho temperature, with Curie depths generally larger than Moho depths. The contrary is true in most parts of easternmost Eurasian continent. Magmatic processes feeding the Permian Emeishan large igneous province could have also been genetically linked to deep mantle/crustal processes beneath the Sichuan Basin. The regionally elongated magnetic features and small Curie depths along the Triassic Yangtze-Indochina plate boundary suggest that the igneous province could be caused by tectonic processes along plate margins, rather than by a deep mantle plume. At the same time, we interpret the Caroline Ridge, the boundary between the Pacific and the Caroline Sea, as a structure having a continental origin, rather than as hotspot or arc volcanism. The surface heat flow is primarily modulated by a deep isotherm through thermal conduction. This concordance is emphasized along many subduction trenches, where zones of large Curie depths often correspond with low heat flow. Local or regional surface heat flow variations cannot be faithfully used in inferring deep thermal structures, which can be better constrained overall through Curie depths detected from surface magnetic anomalies.     

Gravity and S-wave modelling across the Jan Mayen Ridge,North Atlantic; implications for crustal lithology

The horizontal components from fourteen Ocean Bottom Seismometers deployed along four profiles focused along the western margin of the Jan Mayen microcontinent, North Atlantic, have been modelled with regard to S-waves, based on P-wave models obtained earlier. The seismic models have furthermore been constrained by 2D gravity modelling. High V _p/V _s-ratios (2.3–7.9) within the Cenozoic sedimentary section are attributed to significant porosities, whereas V _p/V _s-ratios in the order of 1.9–2.2 for the Mesozoic and Paleozoic sedimentary rocks indicate shale-dominated lithology throughout the area. The eastern side of the Jan Mayen Ridge is interpreted as a passive, volcanic margin, based on relatively high crustal V _p/V _s-ratios (1.9), whereas lower V _p/V _s-ratios (1.75–1.8) suggest the presence of intermediate composition crust and non-volcanic margin on the western side of the ridge. In the westernmost part of the Jan Mayen Basin, slightly increased upper mantle V _p/V _s-ratios may indicate some degree of serpentization of upper mantle peridotites.     

Controls on the tectono-magmatic evolution of a volcanic transform margin: the Vøring Transform Margin,NE Atlantic

Ocean bottom seismograph (OBS), multichannel seismic and potential field data reveal the structure of the Vøring Transform Margin (VTM). This transform margin is located at the landward extension of the Jan Mayen Fracture Zone along the southern edge of the Vøring Plateau. The margin consists of two distinctive segments. The northwestern segment is characterized by large amounts of volcanic material. The new OBS data reveal a 30–40 km wide and 17 km thick high-velocity body between underplated continental crust to the northeast and normal oceanic crust in the southwest. The southeastern segment of the mar is similar to transform margins elsewhere. It is characterized by a 20–30 km wide transform margin high and a narrow continent-ocean transition. The volcanic sequences along this margin segment are less than 1 km thick. We conclude from the spatial correspondence of decreased volcanism and the location of the fracture zone, that the amount of volcanism was influenced by the tectonic setting. We propose that (1) lateral heat transport from the oceanic lithosphere to the adjacent continental lithosphere decreased the ambient mantle temperature and melt production along the entire transform margin and (2) that right-stepping of the left-lateral shear zone at the northwestern margin segment caused lithospheric thinning and increased volcanism. The investigated data show no evidence that the breakup volcanism influenced the tectonic development of the southeastern VTM.