Mesozoic-Cenozoic tectonic evolution of the Zhuanghai area, Bohai-Bay Basin, east China: the application of balanced cross-sections

The technique of balancing cross-sections, an important method for studying the tectonic history of sedimentary basins, has many applications. It enables one to compile charts for petroleum exploration and development, and growth sections of ancient structures can be restored so that the structural growth history can be studied. In order to study tectonic evolution in the Zhuanghai area of the Bohai-Bay basin, we selected two seismic profiles and compiled two structural growth sections. Based on the two balanced cross-sections, the evolution can be divided into four phases: the Triassic-Middle Jurassic phase, Late Jurassic - Cretaceous phase, Palaeogene extension phase, and Late Palaeogene-to-present phase. The whole area was uplifted during the Triassic-Middle Jurassic phase because of intense extrusion stress related to the Indo-China movement. During the Late Jurassic and Early Cretaceous, intense extension occurred in east China, and the whole area rifted, leading to the deposition of a thick sedimentary sequence. In the Late Cretaceous, the area suffered uplift and compression associated with the sinistral strike slip of the Tanlu fault. In the Palaeogene, a rifting basin developed in the area. Finally, it became stable and was placed in its present position by dextral strike-slip motion. In addition, some problems associated with compiling balanced cross-sections are discussed.

A comprehensive investigation of an offshore active fault in the Western Sagami Bay, central Japan

Offshore active faults, especially those in the deep sea, are very difficult to study because of the water and sedimentary cover. To characterize the nature and geometry of offshore active faults, a combination of methods must be employed. Generally, seismic profiling is used to map these faults, but often only fault-related folds rather than fracture planes are imaged. Multi-beam swath bathymetry provides information on the structure and growth history of a fault because movements of an active fault are reflected in the bottom morphology. Submersible and deep-tow surveys allow direct observations of deformations on the seafloor (including fracture zones and microstructures). In the deep sea, linearly aligned cold seep communities provide indirect evidence for active faults and the spatial migration of their activities. The Western Sagami Bay fault (WSBF) in the western Sagami Bay off central Japan is an active fault that has been studied in detail using the above methods. The bottom morphology, fractured breccias directly observed and photographed, seismic profiles, as well as distribution and migration of cold seep communities provide evidence for the nature and geometry of the fault. Focal mechanism solutions of selected earthquakes in the western Sagami Bay during the period from 1900 to 1995 show that the maximum compression trends NW-SE and the minimum stress axis strikes NE-SW, a stress pattern indicating a left-lateral strike-slip fault.

Tectonics in the northwestern West Philippine basin

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 amagma 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).

Seismic profiles across the middle Tan-Lu fault zone in Laizhou Bay, Bohai Sea, eastern China

The stratigraphic architecture, structure and Cenozoic tectonic evolution of the Tan-Lu fault zone in Laizhou Bay, eastern China, are analyzed based on interpretations of 31 new 2D seismic lines across Laizhou Bay. Cenozoic strata in the study area are divided into two layers separated by a prominent and widespread unconformity. The upper sedimentary layer is made up of Neogene and Quaternary fluvial and marine sediments, while the lower layer consists of Paleogene lacustrine and fluvial facies. In terms of tectonics, the sediments beneath the unconformity can be divided into four main structural units: the west depression, central uplift, east depression and Ludong uplift. The two branches of the middle Tan-Lu fault zone differ in their geometry and offset: the east branch fault is a steeply dipping S-shaped strike-slip fault that cuts acoustic basement at depths greater than 8 km, whereas the west branch fault is a relatively shallow normal fault. The Tan-Lu fault zone is the key fault in the study area, having controlled its Cenozoic evolution. Based on balanced cross-sections constructed along transverse seismic line 99.8 and longitudinal seismic line 699.0, the Cenozoic evolution of the middle Tan-Lu fault zone is divided into three stages: Paleocene-Eocene transtension, Oligocene-Early Miocene transpression and Middle Miocene to present-day stable subsidence. The reasons for the contrasting tectonic features of the two branch faults and the timing of the change from transtension to transpression are discussed. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.

渤海湾盆地济阳坳陷东部走滑构造特征及其对油气成藏的影响研究

研究区位于郯庐断裂中段与济阳坳陷的构造结合部，区内走滑构造广泛发育，主要的走滑断裂有7条，分别是郯庐断裂带的东西两支、垦东断层、孤东断层、长堤断层、埕东断层和发育于垦东凸起中部的浅层走滑构造带。走滑构造带与油气富集带有着明显的对应关系。 通过对研究区内二维、三维地震测线和平面构造图的精细解释和分析，分别揭示了各走滑断裂在平面、剖面和三维空间上的构造形态。根据走滑断裂及其伴生构造的平面和剖面上的几何学特征，将研究区内的走滑断裂划分为三种类型：成熟型走滑断裂、隐伏型走滑断裂、不连续型的走滑断裂。 从理论模式研究入手，推导了拉分盆地中盆地的走滑速率与沉降速率之间的关系，证实了走滑速率同盆地的几何形状参数、最大沉降深度和盆地的沉降速率存在着稳定的数值关系。通过对莱州湾地区潍北凹陷基底沉降历史的分析，建立了潍北凹陷沉降速率与郯庐断裂中段走滑速率之间的经验关系式，进而求出郯庐断裂中段新生代右行走滑位移量的大小为40km。 运用2DMove软件，对研究区内四条典型剖面进行构造复原，计算出了各条剖面每个时期的伸展参数，对研究区构造活动强度进行了定量分析，揭示了研究区的构造演化规律。通过运用Ansys软件进行有限元模拟，恢复了晚白垩世晚期-古近纪早期研究区内的构造应力场和应变场，揭示了扭张作用是研究区内走滑断层开始走滑的主要原因。 通过上述分析，结合对究区内近几年勘探开发成功和失败的实例分析，全面探讨了走滑活动对于油气成藏“生”、“储”、“盖”、“圈”、“运”、“保”各因素的影响。

渤海湾地区前第三系构造特征及其演化研究

Based on fine structural interpretation on seismic profiles of buried-hills in Huanghua depression, structural interpretation and balanced cross-section restoration of regional seismic profiles, drawing structural maps of main seismic interfaces, residual strata distribution of different ages in the Bohai Bay region and structural survey in the western Shandong uplifted area and the intracontinental orogeny of Yanshan mountain, the paper has studied pre-tertiary structural styles and tectonic evolution of the Bohai Bay region. There mainly develop 5 types of pre-tertiary structural style that are extension structure, compression structure, strike-slip structure, negative inversion structure and sliding structure in the Bohai Bay region. Among these 5 types of structural style, extension structure develops detachment fault and its controlling fault terrain structure and fault break slop; compression structure develops reverted fold, fault propagation fold, fault bent fold, imbricate thrust structure and triangle zone; strike-slip structure develops positive flower structure, negative flower structure, en-echelon structure and brush structure; negative reversion structure develops Indosinian compression and Yanshanian extension negative reversion structure, late Yanshanian compression and Cenozoic extension negative reversion structure; sliding structure develops interlayer sliding structure and detachment structure. According to Cangdong fault of SN direction, Zhangjiakou – Penglai fault and Qihe – Guangrao fault of NWW direction, the Bohai Bay region can be divided into 6 sub-regions in which structural direction and style is different from each other. Structural maps of bottom boundary of Cenozoic and upper Paleozoic manifest that main NNE structural direction is formed from late Yanshanian to Himalayan movement and minor NWW structural direction and a string of area more than 8000m are mainly suggest that Indosinian tectonic pattern strongly influence on Yanshanian and Himalayan movement. Residual strata distribution characteristics of middle to upper Neoproterozoic in the Bohai Bay region manifest that middle- to neo- aulacogen position may be corresponding to late Mesozoic uplifted zone. Residual Paleozoic distribution characteristics of main ENN suggest that structural alteration should be resulted from late Yanshanian to Himalayan movement while which of minor NWW structures suggest that deeper structure should restrict shallower structure. Structural patterns of main EW fold direction in the Bohai Bay region and thrust structure in eastern part are formed late Triassic in studied area. Granite magma intrusion of early to middle Jurassic mainly develops Yanshan mountain zone. Late Mesozoic rifting basins of NEE direction are widely distributed in the Bohai Bay region and granite magma intrusions are mainly distributed in Tancheng – Rongcheng zone. Mesozoic structural evolution in the Bohai Bay region is related to scissor convergent from east to west between North China plate and Yangtze plate and gradually reinforcing of the west circum-pacific tectonic tract while basin and range province of late Jurassic and early Cretaceous may be mainly related to lithospheric thinning of North China craton in late Mesozoic.

金川镍矿岩体移动与开采稳定性研究

The two major issues in mining industry are work safety and protection of ground environment when carrying on underground mining activities. Cut-and-fill mining method is increasingly applied in China owing to its advantages of controlling ground pressure and protecting the ground environment effectively. However, some cut-and-fill mines such as Jinchuan nickel mine which has big ore body, broken rock mass and high geostress have unique characteristics on the law of ground pressure and rock mass movement that distinguish from other mining methods. There are still many problems unknown and it is necessary for the further analysis. In this dissertation, vast field survey, geology trenching and relative data analysis are carried out. The distribution of ground fissures and the correlation of the fissures with the location of underground ore body is presented. Using of monitoring data by three-dimension fissure meter and GPS in Jinchuan Deposit Ⅱ, the rule of the surface deformation and the reason of ground fissures generation are analyzed. It is shown that the stress redistribution in surrounding rocks resulting from mining, the existence of the void space underground and the influence of on-going mining activities are three main reasons for the occurrence of ground fissures. Based on actual section planes of No.1 ore body, a large-scale 3D model is established. By this model, the complete process of excavation and filling is simulated and the law of rock mass movement and stability caused by Cut-and-fill Mining is studied. According to simulation results, it is concluded that the deformation of ground surface is still going on developing; the region of subsidence on the ground surface is similar with a circle; the area on the hanging wall side is larger than one on the lower wall side; the contour plots show the centre of subsidence lay on the hanging wall side and the position is near the ore body boundary of 1150m and 1250m where ore body is the thickest. Along strike-line of Jinchuan Deposit Ⅱ, the deformation at the middle of filling body is larger than that in the two sides. Because of the irregular ore body, stress concentrates at the boundary of ore body. With the process of excavation and filling, the high stress release and the stress focus disappear on the hanging wall side. The cut-and-fill mechanism is studied based on monitoring data and numerical simulation. The functions of filling body are discussed. In this dissertation, it is concluded that the stress of filling body is just 2MPa, but the stress of surrounding rock mass is 20MPa. We study the surface movement influenced by the elastic modulus of backfill. The minimal value of the elastic modulus of backfill which can guarantee the safety production of cut-and-fill mine is obtained. Finally, based on the real survey results of the horizontal ore layer and numerical simulation, it is indicated that the horizontal ore layer has destroyed. Key words: cut-and-filling mining, 3D numerical simulation, field monitoring, rock mass movement, cut-and-filling mechanism, the elastic modulus of backfill, the horizontal ore layer

青藏高原及邻区面波频散反演--岩石圈-软流层体系结构研究

The Qinghai-Tibet Plateau lies in the place of the continent-continent collision between Indian and Eurasian plates. Because of their interaction the shallow and deep structures are very complicated. The force system forming the tectonic patterns and driving tectonic movements is effected together by the deep part of the lithosphere and the asthenosphere. It is important to study the 3-D velocity structures, the spheres and layers structures, material properties and states of the lithosphere and the asthenosphere for getting knowledge of their formation and evolution, dynamic process, layers coupling and exchange of material and energy. Based on the Rayleigh wave dispersion theory, we study the 3-D velocity structures, the depths of interfaces and thicknesses of different layers, including the crust, the lithosphere and the asthenosphere, the lithosphere-asthenosphere system in the Qinghai-Tibet Plateau and its adjacent areas. The following tasks include: (1)The digital seismic records of 221 seismic events have been collected, whose magnitudes are larger than 5.0 over the Qinghai-Tibet Plateau and its adjacent areas. These records come from 31 digital seismic stations of GSN , CDSN、NCDSN and part of Indian stations. After making instrument response calibration and filtering, group velocities of fundamental mode of Rayleigh waves are measured using the frequency-time analysis (FTAN) to get the observed dispersions. Furthermore, we strike cluster average for those similar ray paths. Finally, 819 dispersion curves (8-150s) are ready for dispersion inversion. (2)From these dispersion curves, pure dispersion data in 2°×2° cells of the areas (18°N-42°N, 70°E-106°E) are calculated by using function expansion method, proposed by Yanovskaya. The average initial model has been constructed by taking account of global AK135 model along with geodetic, geological, geophysical, receiving function and wide-angle reflection data. Then, initial S-wave velocity structures of the crust and upper mantle in the research areas have been obtained by using linear inversion (SVD) method. (3)Taking the results of the linear inversion as the initial model, we simultaneously invert the S wave velocities and thicknesses by using non-linear inversion (improved Simulated Annealing algorithm). Moreover, during the temperature dropping the variable-scale models are used. Comparing with the linear results, the spheres and layers by the non-linear inversion can be recognized better from the velocity value and offset. (4)The Moho discontinuity and top interface of the asthenosphere are recognized from the velocity value and offset of the layers. The thicknesses of the crust, lithosphere and asthenosphere are gained. These thicknesses are helpful to studying the structural differentia between the Qinghai-Tibet Plateau and its adjacent areas and among geologic units of the plateau. The results of the inversion will provide deep geophysical evidences for studying deep dynamical mechanism and exploring metal mineral resource and oil and gas resources. The following conclusions are reached by the distributions of the S wave velocities and thicknesses of the crust, lithosphere and asthenosphere, combining with previous researches. (1)The crust is very thick in the Qinghai-Tibet Plateau, varying from 60 km to 80 km. The lithospheric thickness in the Qinghai-Tibet Plateau is thinner (130-160 km) than its adjacent areas. Its asthenosphere is relatively thicker, varies from 150 km to 230 km, and the thickest area lies in the western Qiangtang. India located in south of Main Boundary thrust has a thinner crust (32-38 km), a thicker lithosphere of about 190 km and a rather thin asthenosphere of only 60 km. Sichuan and Tarim basins have the crust thickness less than 50km. Their lithospheres are thicker than the Qinghai-Tibet Plateau, and their asthenospheres are thinner. (2)The S-wave velocity variation pattern in the lithosphere-asthenosphere system has band-belted distribution along east-westward. These variations correlate with geology structures sketched by sutures and major faults. These sutures include Main Boundary thrust (MBT), Yarlung-Zangbo River suture (YZS), Bangong Lake-Nujiang suture (BNS), Jinshajiang suture (JSJS), Kunlun edge suture (KL). In the velocity maps of the upper and middle crust, these sutures can be sketched. In velocity maps of 250-300 km depth, MBT, BNS and JSJS can be sketched. In maps of the crustal thickness, the lithospheric thickness and the asthenospheric thickness, these sutures can be still sketched. In particular, MBT can be obviously resolved in these velocity maps and thickness maps. (3)Since the collision between India and Eurasian plate, the “loss” of surface material arising from crustal shortening is caused not only by crustal thickening but also by lateral extrusion material. The source of lateral extrusion lies in the Qiangtang block. These materials extrude along the JSJS and BNS with both rotation and dispersion in Daguaiwan. Finally, it extends toward southeast direction. (4)There is the crust-mantle transition zone of no distinct velocity jump in the lithosphere beneath the Qiangtang Terrane. It has thinner lithosphere and developed thicker asthenosphere. It implies that the crust-mantle transition zone of partial melting is connected with the developed asthenosphere. The underplating of asthenosphere may thin the lithosphere. This buoyancy might be the main mechanism and deep dynamics of the uplift of the Qinghai-Tibet hinterland. At the same time, the transport of hot material with low velocity intrudes into the upper mantle and the lower crust along cracks and faults forming the crust-mantle transition zone.

济阳坳陷深层地质构造与演化

Based on geophysical and geological data in Jiyang depression, the paper has identified main unconformity surfaces (main movement surfaces) and tectonic sequences and established tectonic and strata framework for correlation between different sags. Based on different sorts of structural styles and characteristics of typical structures, the paper summarized characteristics and distribution of deep structures, discussed evolution sequence of structure, analyzed the relation between tectonic evolution and generation of petroleum. The major developments are as following: Six tectonic sequences could be divided from bottom to top in the deep zone of Jiyang depression. These tectonic sequences are Cambrian to Ordovician, Carboniferous to Permian, lower to middle Jurassic, upper Jurassic to lower Cretaceous, upper Cretaceous and Kongdian formation to the fourth member of Shahejie formation. The center of sedimentation and subsidence of tectonic sequences distinguished from each other in seismic profiles is controlled by tectonic movements. Six tectonic evolution stages could be summarized in the deep zone in Jiyang depression. Among these stages, Paleozoic stage is croton sedimentation basin; Indosinian stage, open folds of EW direction are controlled by compression of nearly SN direction in early Indosinian (early to middle Triassic) while fold thrust fault of EW – NWW direction and arch protruding to NNE direction are controlled by strong compression in late Indosinian (latter Triassic); early Yanshanian stage (early to middle Jurassic), in relatively weak movement after Indosinian compressional orogeny, fluviolacustrine is deposited in intermontane basins in the beginning of early Yanshanian and then extensively denudated in the main orogenic phase; middle Yanshanian (late Jurassic to early Cretaceous), strike-slipping basins are wide distribution with extension (negative reversion) of NW – SE direction; latter Yanshanian (late Cretaceous), fold and thrust of NE – NNE direction and positive reversion structure of late Jurassic to early Cretaceous strike-slipping basin are formed by strong compression of NW–SE direction; sedimentation stage of Kongdian formation to the fourth member of Shahejie formation of Cenozoic, half graben basins are formed by extension of SN direction early while uplift is resulted from compression of nearly EW direction latterly. Compression system, extension system and strike-slip system are formed in deep zone of Jiyang depression. According to identifying flower structure of seismic profiles and analysis of leveling layer slice of 3D seismic data and tectonic map of deep tectonic interface, strike-slip structures of deep zone in Jiyang depression are distinguished. In the middle of the Jiyang depression, strike-slip structures extend as SN direction, NNW direction in Huimin sag, but NNE in Zhandong area. Based on map of relict strata thickness, main faults activity and regional tectonic setting, dynamic mechanisms of deep structure are preliminary determination. The main reason is the difference of direction and character of the plate’s movement. Development and rework of multi-stage tectonic effects are benefit for favorable reservoir and structural trap. Based on tectonic development, accumulation conditions of deep sub-sags and exploration achievements in recent years, potential zones of oil-gas reservoir are put forward, such as Dongying sag and Bonan sag.

松辽盆地长岭断陷火山岩气藏的形成条件与分布规律

Changling fault depression is a compound fault depression complicated by interior fault, with faults in the west and overlap in the west. North of Changling fault depression show NNE strike while south is NW strike. Changling fault depression has undergone twochasmic stage which control the development and distribution of volcanic rock, one depression stage, later inversion and uplift stage which control the formation of natural gas reservoir, and basin atrophic stage. The main boundary faults and main faults in Changling fault depression control three volcanic cycles and the distribution of volcanic rock. Seismic reflection characteristic and logging response characteristic of volcanic rock in study area are obvious, and the distribution characteristic, volcanic cycle and active stage of volcanic rock can be revealed by seismic attribute, conventional logging data can distinguish clastic rock from volcanic rock or distinguish partial different types of volcanic rock. The reservoir property of rhyolite and volcanic tuff are the best. Favorable volcanic reservoir can be preserved in deep zone. Imaging logging and frequency decompostion technology of seismic data act as effective role in the study of reservoir physical property and gas-bearing properties of volcanic rock.. Hydrocarbon gas in study area is high and over mature coal type gas, the origin of CO2 is complex, it is either inorganic origin or organic origin, or mixing origin. Hydrocarbon gas is mainly originate from Shahezi formation and Yingcheng formation source rocks, CO2 is mainly mantle source gas. Hydrocarbon has the characteristics of continuous accumulation with two charging peak. The first peak represent liquid hydrocarbon accumulation time, The second peak stand for the accumulation time of gaseous hydrocarbon.CO2 accumulate approximately in Neocene. The source rock distribution range, volcanic rock and favorable reservoir facies, distribution characteristic of deep fault (gas source fault) and late inversion structure are the major factors to control gas reservoir formation and distribution. All the results show that these traps that consist of big inherited paleo uplift(paleo slope), stratigraphic overlap and thinning out, volcanic rock, are the most advantageous target zone.

渤海湾盆地前第三系构造演化与煤成气成藏研究

The disequilibrium between supply and demand the east part of North China accelerated natural gas exploration in Bohai bay basin. Exploration practice showed that coal-derived gas is important resource. In searching of big to middle scaled coal derived gas field, and realize successive gas supply, the paper carried out integrated study on structural evolution of Pre-Tertiary and evaluation of reservoir forming condition of coal-derived gas. Study work of the paper was based on the following condition: available achievement in this field at present, good understanding of multiphase of tectonic movement. Study work was focused on geological evolution, source rock evaluation and dissection key factors controlling reservoir forming. Based on analysis of seismic data, drilling data, tectonic style of Pre-Tertiary was subdivided, with different tectonic style representing different tectonic process. By means of state of the art, such as analysis of balanced cross section, and erosion restoration, the paper reestablished tectonic history and analyzed basin property during different tectonic phase. Dynamic mechanism for tectonic movement and influence of tectonic evolution on tectonic style were discussed. Study made it clear that tectonic movement is intensive since Mesozoic including 2 phase of compressional movement (at the end of Indo-China movement, and Yanshan movement), 2 phase of extensional movement (middle Yanshan movement, and Himalayan movement), 2 phase of strike slip movement, as well as 2 phase of reversal movement (early Yanshan movement, and early Himalayan movement). As a result, three tectonic provinces with different remnant of strata and different tectonic style took shape. Based on afore mentioned study, the paper pointed out that evolution of Bohai bay basin experienced the following steps: basin of rift valley type (Pt2+3)-craton basin at passive continental margin (∈1－2)-craton basin at active continental margin (∈3- O)-convergent craton basin (C-T1+2)-intracontinental basin (J＋K). Superposition of basins in different stage was discussed. Aimed at tectonic feature of multiple phases, the paper put forward concept model of superposition of tectonic unit, and analyzed its significance on reservoir forming. On basis of the difference among 3 tectonic movements in Mesozoic and Cenozoic, superposition of tectonic unit was classified into the following 3 categories and 6 types: continuous subsidence type (I), subsidence in Mesozoic and uplift for erosion in Cenozoic (II1), repeated subsidence and uplift in Mesozoic and subsidence in Cenozoic (II2), repeated subsidence and uplift in Mesozoic and uplift for erosion in Cenozoic (II3), uplift for erosion in Mesozoic and subsidence in Cenozoic (II4), and continuous uplift (III). Take the organic facies analysis as link, the paper established relationship between sedimentary environment and organic facies, as well as organic facies and organic matter abundance. Combined information of sedimentary environment and logging data, the paper estimated distribution of organic matter abundance. Combined with simulation of secondary hydrocarbon generation, dynamic mechanism of hydrocarbon generation, and thermal history, the paper made static and dynamic evaluation of effective source rock, i.e. Taiyuan formation and Shanxi formation. It is also pointed out that superposition of tectonic unit of type II2, type II4, and type I were the most favorable hydrocarbon generation units. Based on dissection of typical primary coal-derived gas reservoir, including reservoir forming condition and reservoir forming process, the paper pointed out key factors controlling reservoir forming for Carboniferous and Permian System: a. remnant thickness and source rock property were precondition; b. secondary hydrocarbon generation during Himalayan period was key factor; c. tectonic evolution history controlling thermal evolution of source rock was main factor that determine reservoir forming; d. inherited positive structural unit was favorable accumulation direction; e. fault activity and regional caprock determined hydrocarbon accumulation horizon. In the end, the paper established reservoir forming model for different superposition of tectonic units, and pointed out promising exploration belts with 11 of the first class, 5 of the second class and 6 of the third class.

天山南北山前盆地中-新生代沉积记录及其动力学分析

It has been long known that intense multiple Mesozoic-Cenozoic intracontinental deformations have controlled the grand scale basin-range structural evolution of the Tianshan and its adjacent basins. So it is important to study the sedimentary records of the piedmont basins along the two sides of the Tianshan synthetically for the continental geodynamic research.We carried out a magnetostratigraphy study on Cretaceous- Tertiary succession and U-Pb dating analysis of detrital zircons from the representative sandstone samples of the Mesozoic-Cenozoic deposits in Kuqa Subbasin, northern Tarim Basin, combining our previous results of multiple depositional records from different profiles including paleocurrent data, conglomerate clast, sandstone framswork grains, detrital heavy minerals and geochemistry analysis, so the multiple intracontinental tectonic processes of Tianshan and their depositional response in the Kuqa Subbasin can be revealed. The results show that the tectonic evolution of the Tianshan Orogen and the sedimentary processes of the Kuqa Subbasin can be divided into four periods: early Triassic(active period), from middle Triassic to late Jurassic(placid period), from early Cretaceous to Tertiary Paleocene(active period) and from Neogene to present (intensely active period). Simultaneously，the depositional records reveal the provenance types and tectonic attributes in different periods. As follows, the lower Triassic with a dominant age ranging from 250 to 290Ma of the Zircons, which were principally derived from alkali feldspar granites and alkaline intrusion obviously, relative to the magma activity in Permian. In middle Triassic-late Jurassic, the two samples collected from the Taliqike formation and the Qiakemake formation respectively show the age peak at 350～450Ma, which was relative to the subduction of the Tarim Block to Yili-Central Tianshan Plate. In this period the provenance of the Kuqa deposits was the Central Tianshan arc orogenic belts distantly with little height predominance.During early Cretaceous-Paleogene, two major zircons age spectra at 240~330Ma and 370~480Ma have been acquired, with some other not dominant age ranges, indicating complicated provenance types. In Neogene, the detrital zircons age dating ranges from 460 to 390 Ma primarily. What’s more, the newer chronology of the stratigraphy and the older source age, indicating that Tianshan was uplifted and exhumated further strongly. Further study on the heavy mineral and the detrital zircons age dating of the Mesozoic-Paleogene representative profiles in southern Junggar Basin, combined with the published results of the sandstone framework grains, we consider that it occurred obvious sedimentary and tectonic changes occurred in the inside of Jurassic, from late Jurassic to early Cretaceous and form early Cretaceous to late Cretaceous. On this faces, there are remarkable changes of the steady minerals and unstable minerals, the sandstone maturity and the age spectra of the detrital zircons. Compared the sedimentary records from the two sides of the Tianshan, We find that they are different obviously since Middle Jurassic. It can be concluded that Tianshan have uplifted highly enough to influence the paleo-climatic. According to the current strata division, the structural activity apparently showed a migration from north to south. That is to say, the South Tianshan uplift later than the north, especially from late Jurassic to early Cretaceous , but it was uplifted and exhumated more strongly. Furthermore, correlating the depositional records and tectonic styles in the Kuqa-South Tianshan basin-range conjugation site in the east with the west, the obvious differentiation between the west and the east from the Cretaceous especially in Tertiary along the Tianshan-Kuqa belt was revealed, probably showing earlier uplifting in the east while greater exhumation depth and sediment rates in the west. In addition, the contacting style of Kuqa subbasin to the Tianshan Orogenic belts and the basement structure are also inconsistent at different basin-range conjugation sites. It is probably controlled by a series of N-S strike adjusting belts within the Kuqa subbasin, or probably correlated with the material difference at the complicated basin-range boundary. The research on the Mesozoic-Cenozoic tectonic-depositional response in the piedmont basins along the two sides of the Tianshan shows that the basin-filling process was controlled by the intracontinental multicyclic basin-range interactions, especially affected by the intense tectonic differentiations of basin-range system, which can’t be illuminated using a single evolutionary model.

南襄盆地泌阳凹陷断裂斜坡带构造特征与油气成藏

The faulted slope zone of Biyang depression, a multiple hydrocarbon accumulation zone lying in a rich oil depression of Nanxiang basin, is a structural-sedimentary compounded slope, which is developed in Yanshanian period and has an area of 500 km2. From the ‘bottom up’, the developed strata may be divided into Yuhuangding formation in Neogene, Dacang Fang, Hetao-yuan plus Liaozhuang formations and Fenghuangzheng plus Pingyuan formation in Neogene, while Hetao-yuan formation is the main hydrocarbon-bearing target. Because of transtensional stress fields formed by persistent action of large-scale faulting in the south of the depression, sedimentary differential compaction in different stages, and tectonic inversion in later developing stage of the depression, a series of nose structure zones cut by different strike faults are developed. Therefore, the reservoir migration and accumulation are controlled by the complex faulted-nose structural zone, reservoir types are dominated by faulted-noses, faulted-blocks and fault-lithology, while lithology and stratigraphic unconformable reservoirs are locally developed. In combination with demands of practical production, applying with a new research approach of systematology and a combination with dynamic and static modes, guided by modern petroleum geologic theory, and based on previous data and studies, new techniques, methods of geophysical exploration, various computer simulation and forecasting techniques are applied in the new research of this paper. Starting from the structural features and formation mechanism, the forming mechanism of faulted structure, conditions and controlling factors of hydrocarbon accumulation, as well as various space-time allocation relationships in the process of accumulation are analyzed in the research. Besides that, the hydrocarbon migration, accumulation mechanism and dynamic evolution process are also discussed in the paper. Through the research, the accumulation rule of the faulted slope zone in faulted lake basin, the distribution and enrichment regularity of different reservoir controlling factors are systematically summarized. The summarizations indicate that the faulted slope is a favorable orientational zone, hydrocarbon is accumulated in nose structures and enriched in the main body of nose structures, faulted transformation zone and the ascent direction of laddering faulted blocks, the faults are the controlling factors, hydrocarbon accumulation zones controlled by fault-lithology are distributed along the faulting direcion. In the end, hydrocarbon migration and accumulation models of complex faulted-nose blocks are established. 1) Down cut model—‘flank-sheet’: the hydrocarbon is migrated like ‘sheet’ along a series of faults with parallel distribution and accumulated in the flank of nose structures; 2）Cross cut --‘axis-string’ model: the hydrocarbon cutting across the faults is migrated like ‘string’ and accumulated in the axis of nose structures. In view of different distribution models, reservoir forming combination patterns are divided and hydrocarbon reservoir evaluation exploration is carried out, which achieves good results in application. Key words: faulted slope zone; migration and accumulation model; reservoir controlling mechanism; reservoir-forming combination

青藏高原东部电性结构特征及其构造意义

Eastern Himalayan Syntaxis (EHS) and its surroundings (eastern margin of Tibet) is one of the most complicated tectonic areas in the world. As the exhaust opening of the balanced materials of the Tibetan Plateau during the collision of Indan and Eurasian plates, the deep structure beneath EHS surrounding region is referred to as the key to the study of the dynamics of the plateau. EHS3D project, sponsored by NSFC, has been proposed to explore the deep electric features of the area. During the first stage of EHS3D(2006-2008), MT+LMT measurements have been conducted along two lines from Chayu to Qingshuihe (EHS3D-3) and Chayu to Ruoergai (EHS3D-2). This paper will discuss the MT models of EHS3D-3 line. By the data procrssing, including distortion analysis, Robust estimation and strike decomposition, rotated apparent resitivities and phases have been obtained for each station. Then conventional 2-D inversion algorithms (NLCG and RRI) were employed to produce 2-D models. The final preferred 2-D model suggests that the upper crust consists of resistive blocks while in mid-lower crust there are two extensive conductive bodies beneath Lhasa block and Qiangtang terrain respectively. Jinshajiang suture is a gradient belt and Bangong-Nujiang suture appear a conductive belt dipping to the north. . We concluded that the formation of the two conductive bodies attributed to the partial melt and fluids in the lower crust. The regional electric strike derived from decomposition analysis indicates that the crust and upper mantle move in different manners. The upper crust moves like slips of rigid blocks along major slip faults while the lower crust creeps as a flow in the conductive channels.

巴丹吉林沙漠沙丘、植被和湖泊演化

The formation and evolution of magedunes and lakes in Badain Jaran desert is focused by scholars for a long time. In this paper, detailed investigation was made with the Remote Sensing, Geographic Information Systems, climatological data of research region to study the evolution of magedunes, vegetation and lakes. The main conclusions are presented as follows: (1) The magedunes are mainly located in south and northeast of the desert. The density of magedunes decreases from south to north, east to west, and greatest in southeast of the desert. Most of magedunes strike NE30°~60°, and which are NE-SW and NNE-SSW directions. The distribution of magedunes’ strikes indicates that the paleowind of the desert is northwest and west wind. (2) The vegetation cover is low in the Badain Jaran Desert, but there are some well-vegetated areas in the desert, and the value of NDVI is 0.6107. In southeast of the desert, the vegetation degradated seriously from 1987 to 2000. (3) At about 2000, the total area of permanent lakes was 2231.64 hm2 (±5.9%) in southeast of Badain Jaran Desert. From 1960 to about 2000, the lakes changed as followings: in the early 30 years, the area of lakes increased, but after 1990 it decreased. When lakes were large, the toral area of lakes is 20648 hm2 in Badain Jaran Desert, much larger than that of present lakes. (4) From 1961 to 2001, the mean annual evaporation of lakes was 1039.8mm (±10%) in Badain Jaran Desert, and the difference between years was large. The monthly evaporation of lakes was mainly affected by rainfall, temperature. And it was largest in June, 140.9mm(±10%). (5) Based on water balance calculation of present lakes and old lakes in southeast of Badain Jaran Desert, the total precipitation is more than the total evaporation in this area. So it is probable that the precipitation in the lake area supplies water to the lakes, and also to groundwater in west and north part of the desert.