Oil and gas play and prospect assessments of Babel,Diwania and Karbala Governorates (Middle Euphrates Region), Iraq

This study was based on the results of geochemical analysis of 332 core and 10 cutting rock samples from Triassic Jurassic, Cretaceous, and Triassic age, in addition to seismic sections, logs, initial drilling results, final reports of oil wells, and previous studies. Constructing models from these data are to assess new oil reservoirs, evaluation, and development of the existing oil reservoirs and hydrocarbon potential, and suggesting petroleum systems in order to reduce exploration risk and develop simple risk assessment of oil fields in the studied area. In general, Abu-Jir fault zone divides the studied area into two petroleum provinces: Mesopotamian Foredeep Basin and Widyan Basin–Interior Platform. The Mesopotamian Fordeep basin are thick stratigraphic sequences with no exploration for oil or gas source rock intervals within the Paleozoic sequence. while the Mesozoic sequence offers the best potential. The transitional sequence of the Triassic period is expected to contain occasional fair to good quantity of oil source rock intervals. The Widyan Basin–Interior Platform is an area with possible deployment of low to moderate risk of Paleozoic play and Lower Mesozoic plays with fair Triassic and Mesozoic objectives. Oil has generated and expelled into traps in the studied area during two phases; the first is during Early Palaeogene that accumulated in traps of the Cretaceous structural deformation, while the second is during Late Neogene.     

Geological evolution of the Iraqi Mesopotamia Foredeep,inner platform and near surroundings of the Arabian Plate

The Iraqi territory could be divided into four main tectonic zones; each one has its own characteristics concerning type of the rocks, their age, thickness and structural evolution. These four zones are: (1) Inner Platform (stable shelf), (2) Outer Platform (unstable shelf), (3) Shalair Zone (Terrain), and (4) Zagros Suture Zone. The first two zones of the Arabian Plate lack any kind of metamorphism and volcanism.The Iraqi territory is located in the extreme northeastern part of the Arabian Plate, which is colliding with the Eurasian (Iranian) Plate. This collision has developed a foreland basin that includes: (1) Imbricate Zone, (2) High Folded Zone, (3) Low Folded Zone and (4) Mesopotamia Foredeep.The Mesopotamia Foredeep, in Iraq includes the Mesopotamia Plain and the Jazira Plain; it is less tectonically disturbed as compared to the Imbricate, High Folded and Low Folded Zones. Quaternary alluvial sediments of the Tigris and Euphrates Rivers and their tributaries as well as distributaries cover the central and southeastern parts of the Foredeep totally; it is called the Mesopotamian Flood Plain. The extension of the Mesopotamia Plain towards northwest however, is called the Jazira Plain, which is covered by Miocene rocks.The Mesopotamia Foredeep is represented by thick sedimentary sequence, which thickens northwestwards including synrift sediments; especially of Late Cretaceous age, whereas on surface the Quaternary sediments thicken southeastwards. The depth of the basement also changes from 8 km, in the west to 14 km, in the Iraqi–Iranian boarders towards southeast.The anticlinal structures have N–S trend, in the extreme southern part of the Mesopotamia Foredeep and extends northwards until the Latitude 32°N, within the Jazira Plain, there they change their trends to NW–SE, and then to E–W trend.The Mesozoic sequence is almost without any significant break, with increase in thickness from the west to the east, attaining 5 km. The sequence forms the main source and reservoir rocks in the central and southern parts of Iraq. The Cenozoic sequence consists of Paleogene open marine carbonates, which grades upwards into Neogene lagoonal marine; of Early Miocene and evaporitic rocks; of Middle Miocene age, followed by thick molasses of continental clastics that attain 3500 m in thickness; starting from Late Miocene. The Quaternary sediments are very well developed in the Mesopotamia Plain and they thicken southwards to reach about 180 m near Basra city; in the extreme southeastern part of Iraq.The Iraqi Inner Platform (stable shelf) is a part of the Arabian Plate, being less affected by tectonic disturbances; it covers the area due to south and west of the Euphrates River. The main tectonic feature in this zone that had affected on the geology of the area is the Rutbah Uplift; with less extent is the Ga’ara High.The oldest exposed rocks within the Inner Platform belong to Ga’ara Formation of Permian age; it is exposed only in the Ga’ara Depression. The Permian rocks are overlain by Late Triassic rocks; represented by Mulussa and Zor Hauran formations, both of marine carbonates with marl intercalations. The whole Triassic rocks are absent west, north and east of Ga’ara Depression. Jurassic rocks, represented by five sedimentary cycles, overlie the Triassic rocks. Each cycle consists of clastic rocks overlain by carbonates, being all of marine sediments; whereas the last one (Late Jurassic) consists of marine carbonates only. All the five formations are separated from each other by unconformable contacts. Cretaceous rocks, represented by seven sedimentary cycles, overlie the Jurassic rocks. Marine clastics overlain by marine carbonates. Followed upwards (Late Cretaceous) by continental clastics overlain by marine carbonates; then followed by marine carbonates with marl intercalations, and finally by marine clastics overlain by carbonates; representing the last three cycles, respectively.The Paleocene rocks form narrow belt west of the Ga’ara Depression, represented by Early–Late Paleocene phosphatic facies, which is well developed east of Rutbah Uplift and extends eastwards in the Foredeep. Eocene rocks; west of Rutbah Uplift are represented by marine carbonates that has wide aerial coverage in south Iraq. Locally, east of Rutbah Uplift unconformable contacts are recorded between Early, Middle and Late Eocene rocks. During Oligocene, in the eastern margin of the Inner Platform, the Outer Platform was uplifted causing very narrow depositional Oligocene basin. Therefore, very restricted exposures are present in the northern part of the Inner Platform (north of Ga’ara Depression), represented by reef, forereef sediments of some Oligocene formations.The Miocene rocks have no exposures west of Rutbah Uplift, but north and northwestwards are widely exposed represented by Early Miocene of marine carbonates with marl intercalations. Very locally, Early Miocene deltaic clastics and carbonates, are interfingering with the marine carbonates. The last marine open sea sediments, locally with reef, represent the Middle Miocene rocks and fore reef facies that interfingers with evaporates along the northern part of Abu Jir Fault Zone, which is believed to be the reason for the restriction of the closed lagoons; in the area.During Late Miocene, the continental phase started in Iraq due to the closure of the Neo-Tethys and collision of the Sanandaj Zone with the Arabian Plate. The continental sediments consist of fine clastics. The Late Miocene – Middle Pliocene sediments were not deposited in the Inner Platform.The Pliocene–Pleistocene sediments are represented by cyclic sediments of conglomeratic sandstone overlain by fresh water limestone, and by pebbly sandstone.The Quaternary sediments are poorly developed in the Inner Platform. Terraces of Euphrates River and those of main valleys represent pleistocene sediments. Flood plain of the Euphrates River and those of large valleys represent Holocene sediments. Residual soil is developed, widely in the western part of Iraq, within the western marginal part of the Inner Platform.     

Palynomorph stratigraphy,palynofacies and organic geochemistry assessments for hydrocarbon generation of Ratawi Formation,Iraq

Seventy-two core and cutting samples of the Ratawi Formation from selected wells of central and southern Iraq in Mesopotamian Foredeep Basin are analysed for their sedimentary organic matters. Dinoflagellates, spores and pollen are extracted by palynological techniques from these rocks. Accordingly, Hauterivian and late Valanginian ages are suggested for their span of depositional time. These palynomorphs with other organic matter constituents, such as foraminifer’s linings, bacteria and fungi, are used to delineate three palynofacies types that explain organic matter accumulation sites and their ability to generate hydrocarbons. Palaeoenvironments of these sites were mainly suboxic to anoxic with deposition of inshore and neritic marine environments especially for palynofacies type 2. Total organic matters of up to 1.75 total organic carbon (TOC) wt.% and early mature stage of up to 3.7 TAI based on the brown colour of the spore species Cyathidites australis and Gleichenidites senonicus with mottled interconnected amorphous organic matter are used for hydrocarbon generation assessment from this formation. On the other hand, these rock samples are processed with Rock-Eval pyrolysis. Outcomes and data calculations of these analyses are plotted on diagrams of kerogen types and hydrocarbon potential. Theses organic matter have reached the mature stage of up to T _max?=?438 °C, hydrogen index of up to 600 mg hydrocarbons for each gram of TOC wt.% and mainly low TOC (0.50–1.55). Accordingly, this formation could generate fair quantities of hydrocarbons in Baghdad oil field and Basrah oil fields. Organic matters of this formation in the fields of Euphrates subzone extends from Hilla to Nasiriyah cities have not reached mature stage and hence not generated hydrocarbons from the Ratawi Formation. Software 1D PetroMod basin modelling of the Ratawi Formation has confirmed this approach of hydrocarbon generation with 100 % transformations of the intended organic matters to generate hydrocarbons to oil are performed in especially oil fields of East Baghdad, West Qurna and Majnoon while oil fields Ratawi and Subba had performed 80–95 % transformation to oil and hence end oil generation had charged partly the Tertiary traps that formed during the Alpine Orogeny. Oil fields of Nasiriyah and Kifle had performed least transformation ratio of about 10–20 % transformation to oil, and hence, most of the present oil in this field is migrated from eastern side of the Mesopotamian Foredeep Basin that hold higher maturation level.     

恩格尔乌苏冲断带特征及大地构造意义

研究表明恩格尔乌苏冲断带是华北板块和塔里木板块的缝合线,北东东向断续延长800km以上。该冲断带连同南北陆缘地带构造构成典型的陆-弧-陆碰撞造山带,与碰撞造山作用同时,形成区域性透入性劈理。地层学和同位素地质年代学资料表明,碰撞造山作用发生于海西末期或印支早期。碰撞造山作用的动力学过程主要表现为向南的洋壳俯冲和向北的陆壳仰冲,并伴随右旋剪切滑移运动。恩格尔乌苏混杂岩带为韧性-韧脆性冲断推覆构造,其北侧的前陆褶皱冲断带为脆性-脆韧性冲断推覆及褶皱构造。     

Resolving slip vector azimuths and plate motion along the southern boundary of the South Bismarck Plate,Papua New Guinea

The interaction of the Australian, South Bismarck and Solomon Sea Plates in Papua New Guinea is the source of frequent earthquakes that occur as a result of subduction and arc continent collision. Previous investigators have drawn attention to a discontinuity in the horizontal azimuth of slip vectors along the southern boundary of the South Bismarck Plate, with those to the west of 148°E being systematically rotated 20ndash;30° clockwise compared to those located east of 148°E. This has led to the suggestion that relative motion may be occurring between the Huon Peninsula and New Britain or that more than two plates are acting south of the South Bismarck Plate. Global positioning system (GPS) measurements since 1991 indicate that there is no internal deformation occurring within the South Bismark Plate and that at least two distinct plates are in contact with the southern edge of the South Bismarck Plate. We show from a study of a recent earthquake dataset that the change in slip vector azimuth can be modelled by the interaction of the overriding South Bismarck Plate with the underthrusting Australian and Solomon Sea Plates, consistent with the GPS observations, while maintaining the South Bismarck Plate as a rigid entity. We found that a transition zone exists between 147°E and 148°E where the underlying plate changes from the Australian Plate to the Solomon Sea Plate. There are insufficient data at present to indicate whether or not a third plate, the Woodlark Plate, is also interacting directly with the South Bismarck Plate in this transition zone. Slip vector azimuths were used to estimate an Euler pole (6.74°S, 144.64°E), which describes the relative motion of the South Bismarck and Solomon Sea Plates along the New Britain Trench.     

秦岭造山带勉略缝合带构造变形与造山过程

秦岭晚古生代以来造山过程中的构造变形研究对建立华北板块与华南板块之间的最终拼合过程尤为重要。为此，选择勉略带进行了详细的野外调查，对其物质组成，几何学结构，变形序列，运动学和动力学作了系统解剖，认为：勉略带是有一定宽度，由一定实体组成的蛇构造混杂岩带，它包括不同时代，不同构造背景，不同起源的一系列构造岩片，如：基底岩片组，洋壳岩片组，岛弧岩片组，碰撞构造沉积楔形体，大陆边缘岩片组，它们被一系列的北倾南冲的断裂分割。勉略带到－高川段的北倾南冲逆冲断裂和勉略带北部南倾北冲的逆冲断裂组合成为现今不对称的正花状几何学结构，但勉略带的北界状元碑断裂和南界 到－略阳断裂走滑特征明显。结合勉略带邻区的构造特征，分别对带内重要断裂及岩片的构造解析表明，除主造山的大地构造演化阶段外，可将勉略带构造变形序列及演化历程总体归纳为三大阶段：俯冲变形阶段，主造山碰撞变形阶段的陆内造山调整变形阶段，并对不同变表阶段的时限，变形特征，运动学和动力学分别作了描述；最后针对该区复杂的楔入，挤出（逃逸）走滑，逆冲过程，提出了一个统一的动力学演化模式。     

Petroleum Geology of the Southern Pre-Uralian Foredeep with Reference to the Northeastern Pre-Caspian Basin

The southern Pre-Uralian Foredeep and the northeastern Pre-Caspian Basin of southern Russia and Kazakhstan are at the juncture of two major oil-producing regions, the Volga-Ural Basin and the new fields of the Northern Caspian Basin (e.g., Tengiz). The southern Pre-Uralian Foredeep has produced little oil; nevertheless, the Permian-Carboniferous stratigraphy and the general fold-thrust structure of the Pre- Uralian Foredeep, and adjacent Pre-Caspian Basin, afford the possibility for classic and largely untested sub-salt and sub-thrust plays.

Prior to the onset of Uralian orogenic activity, Late Devonian-Early Carboniferous rifting disrupted the East European continent, forming a series of rift basins including the Kama-Kinel troughs and the Pre- Caspian Basin. The Middle Carboniferous to Early-Middle Triassic Uralian Orogenic Belt consists of a complicated series of lower Paleozoic continental margin sequences, basement nappes, and accreted terranes, structurally interleaved via large-scale folding and thrusting. The orogen formed as a result of a progressive series of collisions between the East European continent and microcontinental plates and island arcs (the Tagil-Magnitogorsk and Eastern Uralian megazones), and the Kazakhstan and Siberian continents. N-S and W-E divisions of the Uralian Orogenic Belt and Pre-Uralian Foredeep reflect the basic tectonic structure of the orogen.

The Pre-Uralian Foredeep is not a simple flexural foreland basin, but the exact structural configuration is unresolved. In general, the regional stratigraphy and structure of the foredeep is more complicated than depicted in the literature and on published maps; the biostratigraphy critically needs to be updated. The foredeep developed as a series of regional depressions with up to fourth-order sub-basins. Within these sub-basins, both tectonic and eustatic mechanisms appear to control the sequence stratigraphy. Because of the tectonic influence, subsurface correlation based on sequence stratigraphic concepts may be valid only within each sub-basin. In part, the present structure of the Pre-Uralian Foredeep may reflect the structurally controlled Permian-Carboniferous paleogeography. This complex paleogeography also suggests that application of a simple “balanced cross-section” methodology could lead to erroneous results. Also unresolved are the paleogeographic, stratigraphic, and structural relationships between the Pre- Caspian Basin and the Pre-Uralian Foredeep.     

New constraints on Holocene uplift rates for the Baudo Mountain Range,northwestern Colombia

A beach deposit on the southern end of the Baudo Mountain Range, at an elevation of ∼2.0 m above the backshore of the modern beach, was dated at ∼2870 years using optically stimulated luminescence dating. The calculated average uplift rate necessary to raise this deposit is 0.7 mm/yr. This rate combines the long-term regional deformation associated with the subduction of the Nazca Plate under the South American Plate and the collision of the Choco Block microplate against the South American continent, as well as uplift from local faults. We propose that rapid emergence probably as several pulses, each involving decimeter scale coseismic uplift, is likely to have occurred to elevate the beach above the intertidal zone and offset destructive wave erosion.     

华南陆区板块活动与构造体系的形成演化——纪念李四光先生诞辰130周年

本文通过华南陆区中新元古代以来板块活动与构造体系的"一体化"融合研究,从构造体系形变特征、形成演化历史、形成机制等方面分析了其与板块活动的成生联系。构建了区内以扬子反S型构造体系、新华夏构造体系、南岭纬向带为主体的多体系复合构造格局。其中,新厘定的扬子反S型构造体系为扬子板块的主体构造,原属于华夏系,奠基于晋宁期扬子、华夏板块的陆陆碰撞,定型于燕山陆内活化造山时期。新华夏构造体系为滨西太平洋的主体构造,包括具有成生联系的北东向华夏式和北北东向新华夏式两种型式,共同经历了燕山期挤压扭动成型、造山后伸展和第四纪以来的弱挤压的演变过程。著名的南岭纬向带主要成型于燕山期的板内经向挤压,以东西向叠加褶皱-花岗岩带为主要特征,活动至今。在此基础上,简要论述了主要构造体系复合控制区域成矿区带和分级控制矿集区、矿田、矿床特征以及燕山期岩浆成矿大爆发的核幔式扩展模式。论证了区内燕山期陆内活化造山具有以欧亚板块与太平洋板块近南北向相对左行扭动为主导的多向汇聚、多因复合的动力学特征。     

Main differences between thrust belts

It is useful to differentiate between thrust belts that are related to east(E)-dipping or west(W)-dipping subduction. More precisely, these either follow or resist the overall ‘eastward’ mantle flow detected by the hot-spot reference frame. Because of the overall ‘westward’ drift of the lithosphere we find in E-dipping subduction that the basal decollement underlying the eastern plate reaches the surface and involves deep crustal rocks. With W-dipping subduction, however, we find that the basal decollement of the eastern plate is warped as well as subducted. Consequently thrust belts related to E- (or NE-) dipping subduction show conspicuous structural and morphologic relief, involve deep crustal rocks, and are associated with shallow foredeeps. On the other hand, thrust belts related to W- (or SW-) dipping subduction show relatively low structural and morphological relief, involve only shallow upper crustal rocks and are associated with deep foredeeps as well as back-arc extension. The accretionary wedge-foredeep-back-arc basin association is visualized as an overall eastward propagating tectonic wave. The accretionary wedge forms in the frontal parts and generally below sea-level. This is followed by forward migrating extension that cuts the earlier accretionary wedge. Typically such a system occurs in the context of overall W-dipping subduction and is characterized by an arcuate shape (e.g. Carpathians, Apennines, Barbados, etc.). Along the branches of the arc external transpression and internal transtension co-exist but with different sense (i.e. sinistral transpression contrasting with dextral transtension). We also observe that with W-dipping subduction the tangent to a pre- deformation marker is descending into the foredeep at an angle in the range of 1–10° while with E-(or NE-)dipping subduction the same marker would rise towards the hinterland with typical angles of about 5–10°. Foredeep subsidence is mainly controlled by the load of the thrust sheets in thrust belts due to E-(or NE-)dipping subduction and by the roll-back of the subduction hinge in accretionary wedges due to W-dipping subduction. Subsidence or uplift rates in the foredeeps and accretionary wedges related to the two different types of subduction are very different, providing different P-T-t paths in the two geodynamic realms. The present shape and structure of the thrust belts belonging to one of these two general types may help us in reconstructing the location of thinned lithosphere and basin evolution in the past.     

太行山隆起南段新构造变形过程研究

基于TM遥感影像解译和断裂滑动矢量资料的野外观测,结合年轻地质体热同位素和放射性同位素年代学测试结果分析,重点描述了太行山隆起南段构造地貌特征,划分了新构造变形阶段,确定了新构造应力场及其转换历史。研究表明,新近纪以来,太行山南段经历了两期重要的引张变形时期。中新世中晚期,伴随华北地区广泛的基性火山喷溢活动,太行山南段受近NE-SW向引张应力作用,构造变形集中在南段东缘和南缘断裂带上。上新世至早更新世时期,强烈的NW-SE向地壳引张导致太行山隆起南段夷平地貌的解体和地堑盆地的形成。自中晚更新世以来,太行山南缘断裂带成为新构造变形的主要边界带。断面滑动矢量分析和山前年轻冲积扇体和小冲沟沿断裂错移特征分析,表明太行山南缘断裂带是一条斜张左旋走滑边界断裂带,引张方向为NW-SE至NNW-SSE.从区域大地构造角度,中新世中国东部NE-SW向拉伸作用与东部太平洋板块向西俯仲导致的弧后扩张动力过程有关;而上新世以来新构造变形是与青藏高原快速隆升及其向东构造挤出作用有关。      

The Persian Gulf Basin: Geological history, sedimentary formations, and petroleum potential

The Persian Gulf Basin is the richest region of the World in terms of hydrocarbon resources. According to different estimates, the basin contains 55–68% of recoverable oil reserves and more than 40% of gas reserves. The basin is located at the junction of the Arabian Shield and Iranian continental block that belong to two different (Arabian and Eurasian) lithospheric plates. Collision of these plates at the Mesozoic/Cenozoic boundary produced the Zagros Fold Belt and the large Mesopotamian Foredeep, which is a member of the Persian Gulf Basin. During the most part of the Phanerozoic, this basin belonged to an ancient passive margin of Gondwana, which was opened toward the Paleotethys Ocean in the Paleozoic and toward the Neotethys in the Mesozoic. Stable subsidence and the unique landscape-climatic conditions favored the accumulation of a very thick sedimentary lens of carbonate rocks and evaporites (up to 12–13 km and more). Carbonate rocks with excellent reservoir properties are widespread, while the evaporites play the role of regional fluid seals. Organicrich rocks, which can generate liquid and gaseous hydrocarbons (HC), are present at different levels in the rock sequence.     

Microstructures of mylonites along the Karakoram Shear Zone,Tangste Valley,Pangong Mountains,Karakoram

The Karakoram Shear Zone is a northwest-southeast trending dextral ductile shear zone, which has affected the granitic and granodioritic bodies of the southern Asian Plate margin in three distinct episodes. The ductile shearing of the granitic bodies at Tangste and Darbuk has resulted in the development of mylonites with mylonitic foliation and stretching lineation. More intense deformation is noted in the Tangste granite grading up to orthomylonite, as compared to the Darbuk granite. Kinematic indicators include S-C foliation, synthetic C′ and C″ antithetic shear bands, Type A s-mantled porphyroclasts, oblique quartz foliation, micro-shears with bookshelf gliding, mineral fishes including Group 2 mica fishes, and Type 1 and 2a pull-apart microstructures, and exhibit strong dextral sense of ductile shearing towards southeast. The textural features of the minerals, especially that of quartz and feldspar, indicate temperature of mylonitisation ranging between 300 and 500°C in the upper greenschist facies, and appear to have been evolved during exhumation as a consequence of oblique strike-slip movements along the Karakoram shear zone.     

Cenozoic Plate interaction of the Australia and Philippine Sea Plates: “hit-and-run” tectonics

Recent studies in northwest New Guinea have shown the presence of at least two marginal basins of different age, both of which formed in back-arc settings. The older basin opened between the Middle Jurassic and Early Cretaceous, a remnant of which is now preserved as the New Guinea Ophiolite. Its obduction started at 40 Ma and it was finally emplaced on the Australian margin at 30 Ma. The younger basin was active during the Oligocene to Middle Miocene and was obducted in the Early Pliocene. Studies of the western edge of the Philippine Sea also reveal an important deformation of the Philippine arc in the Oligocene, which hitherto has remained unexplained. Using information from these systems, paleomagnetic results, kinematic reconstructions and geochemistry of the supra-subduction ophiolite, we present a plate model to explain the region's Eo–Oligocene development. We suggest that an extensive portion of oceanic crust extended the Australian Plate a considerable distance north of the Australian Craton. As Australia began its steady 7–8 cm/year northward drift in the Early Eocene, this lithosphere was subducted. Thus, the portion of the Philippine Sea Plate carrying the Taiwan–Philippine Arc to its present site may have actually been in contact with the ophiolite now in New Guinea and obduction led to deformation of the Philippine Sea Plate itself. Neogene Plate kinematics transported the deformed belt in contact with the Sunda block in the Late Miocene and Pliocene. This interpretation has implications for the origin for the Philippine Sea Plate and the potential incorporation of continental fragments against its boundaries.     

西天山造山带构造单元划分及古生代洋陆转换过程

西天山造山带位于哈萨克斯坦—准噶尔板块与卡拉库姆—塔里木板块的结合部,是由一系列前寒武纪微陆块、古生代洋壳残片及陆缘弧相互拼贴而成的多聚合带、多成矿带,其独特的造山-成矿过程受到了国内外的广泛关注。本文通过构造单元划分与编图,建立了古生代西天山造山带的构造格架,认为古生代西天山造山带的构造演化依次经历了:罗迪尼亚大陆裂解与北天山早古生代多岛洋盆形成阶段(Z-O_2),北天山早古生代多岛洋盆闭合与南天山洋盆开始形成阶段(O_3-S),南、北天山洋晚古生代洋盆形成与发展阶段(D-C_1),南、北天山晚古生代洋盆全面闭合与天山碰撞造山带形成阶段(C1-C_2)和碰撞后板内演化阶段(C_2-P)。     

库车新生代构造性质和变形时间

库车构造位于南天山古生代碰撞造山带之南,为塔里木盆地最北的一个构造带。它自北而南可分为边缘逆冲（ 隐伏构造楔） 、斯的克背斜带、北部线性背斜带、拜城盆地、南部背斜带。每个背斜带又包含有若干逆冲断层相关褶皱,它们是断层转折褶皱、断层传播褶皱、滑脱褶皱、断层传播 滑脱混生褶皱、双重逆冲构造、突发构造、三角带构造。底部逆冲断层向南变浅,堆叠逆冲岩席向南变薄,总体上形成一个向南的逆冲构造楔。逆冲断层在斯的克背斜带侵位最早（２５ Ｍａ） ,在北部线性背斜带为１６９ Ｍａ,拜城盆地中的大宛其背斜为３６ Ｍａ,南部背斜带为５３ Ｍａ（ 北部） 和１８ Ｍａ（ 南部） ,变形作用向南变新。库车构造是印 藏板块碰撞的内陆构造响应,是二叠纪前陆盆地复活而成的再生前陆盆地变形带     

Geodynamics of the Ural Foredeep and Geomechanical Modeling of the Origin of Hydrocarbon Accumulations

We present tectonic implications for hydrocarbon accumulations in the Ural?Novaya Zemlya Foredeep. Its eastern flank is rich in economical oil and gas deposits mostly localized within the fold-and-thrust belt that was constructed as a result of continent?continent collision during the Ural Paleoocean closure. On the basis of striking correlation between oil and gas accumulation and fold-and-thrust tectonics we performed geomechanical and petroleum systems modelling that allowed us to propose a new geodynamical model for hydrocarbon accumulations in both fold-upthrust and subthrust structural levels of the Ural?Novaya Zemlya Foredeep.     

Neotectonic evolution of the northwestward arched segment of the Central Anatolian Fault Zone,Central Anatolia,Turkey

Central Anatolia has undergone complex Neotectonic deformation since Late Miocene–Pliocene times. Many faults and intracontinental basins in this region were either formed, or have been reactivated, during this period. The eastern part of central Anatolia is dominated by a NE–SW-trending, left lateral transcurrent structure named the Central Anatolian fault zone located between Sivas in the northeast and west of Mersin in the southwest. Around the central part, it is characterized by transtensional depressions formed by left stepping and southward bending of the fault zone.Pre-Upper Miocene basement rocks of the region consist of the central Anatolian crystalline complex and a sedimentary cover of Tertiary age. These rock units were strongly deformed by N–S convergence. The entire area emerged to become the site of erosion and formed a vast plateau before the Late Miocene. A NE–SW-trending extensional basin developed on this plateau in Late Miocene–Early Pliocene times. Rock units of this basin are characterized by a thick succession of pyroclastic rocks intercalated with calcalkaline–alkaline volcanics. The volcanic sequence is unconformably overlain by Pliocene lacustrine–fluviatile deposits intercalated with ignimbrites and tuffs. Thick, coarse grained alluvial/colluvial fan deposits of marginal facies and fine grained clastics and carbonates of central facies display characteristic synsedimentary structures with volcanic intercalations. These are the main lines of evidence for development of a new transtensional Hırka–Kızılırmak basin in Pliocene times. Reactivation of the main segment of the Central Anatolian fault zone has triggered development of depressions around the left stepping and southward bending of the central part of this sinistral fault zone in the ignimbritic plateau during Late Pliocene–Quaternary time. These transtensional basins are named the Tuzla Gölü and Sultansazlığı pull-apart basins. The Sultansazlığı basin has a lazy S to rhomboidal shape and displays characteristic morphologic features including a steep and stepped western margin, large alluvial and colluvial fans, and a huge composite volcano (the Erciyes Dağı).The geometry of faulting and formation of pull-apart basins can be explained within the framework of tectonic escape of the wedge-like Anatolian block, bounded by sinistral East Anatolian fault zone and dextral North Anatolian transform fault zone. This escape may have been accomplished as lateral continental extrusion of the Anatolian Plate caused by final collision of the Arabian Plate with the Eurasian Plate.     

Age, composition of rocks, and geological setting of the Snezhnoe beryllium deposit: Substantiation of the Late Paleozoic East Sayan rare-metal zone, Russia

The Snezhnoe phenakite-beryl deposit is one of the highest-grade deposits in the Altai-Sayan beryllium province. This deposit is spatially associated with the alkali granite of the Ognit Complex and localized in the apical part of the granitic pluton. The trace element composition of granite, as well as of Be and Ta-Nb ores was studied. The Rb-Sr age of Be mineralization estimated at 305 Ma is consistent with the time of formation of numerous rare-metal alkali granitic plutons in the Eastern Sayan and the eastern Tuva. The region of these granitic plutons is outlined as the Late Paleozoic East Sayan rare-metal metallogenic zone specialized for Nb, Ta, Be, Li, Zr, Th, and REE mineralization. The East Sayan zone is localized in the marginal part of the Barguzin igneous province and is similar to the marginal zone of this province in composition of igneous associations and metallogenic specialization. The formation of the Barguzin igneous province and the East Sayan metallogenic zone is related to the evolution of the Late Carboniferous-Early Permian mantle plume.     

Neotectonic evolution of the northwestward arched segment of the Central Anatolian Fault Zone,Central Anatolia,Turkey

Abstract

Central Anatolia has undergone complex Neotectonic deformation since Late Miocene-Pliocene times. Many faults and intracontinental basins in this region were either formed, or have been reactivated, during this period. The eastern part of central Anatolia is dominated by a NE-SW-trending, left lateral transcurrent structure named the Central Anatolian fault zone located between Sivas in the northeast and west of Mersin in the southwest. Around the central part, it is characterized by transtensional depressions formed by left stepping and southward bending of the fault zone. Pre-Upper Miocene basement rocks of the region consist of the central Anatolian crystalline complex and a sedimentary cover of Tertiary age. These rock units were strongly deformed by N-S con- vergence. The entire area emerged to become the site of erosion and formed a vast plateau before the Late Miocene. A NE-SW- trending extensional basin developed on this plateau in Late Miocene-Early Pliocene times. Rock units of this basin are characterized by a thick succession of pyroclastic rocks intercalated with calcalkaline-alkaline volcanics. The volcanic sequence is uncon- formably overlain by Pliocene lacustrine-fluviatile deposits interrelated with ignimbrites and tuffs. Thick, coarse grained alluvial/colluvial fan deposits of marginal facies and fine grained elastics and carbonates of central facies display characteristic synsedimentary structures with volcanic intercalations. These are the main lines of evidence for development of a new transtensional H?rka— k?zd?rmak basin in Pliocene times. Reactivation of the main segment of the Central Anatolian fault zone has triggered development of depressions around the left stepping and southward bending of the central part of this sinistral fault zone in the ignimbritic plateau during Late Pliocene-Quaternary time. These transtensional basins are named the Tuzla Gölü and Sultansazl??? pull-apart basins. The Sultansazl??? basin has a lazy S to rhomboidal shape and displays characteristic morphologic features including a steep and stepped western margin, large alluvial and colluvial fans, and a huge composite volcano (the Erciyes Da??).

The geometry of faulting and formation of pull-apart basins can be explained within the framework of tectonic escape of the wedgelike Anatolian block, bounded by sinistral East Anatolian fault zone and dextral North Anatolian transform fault zone. This escape may have been accomplished as lateral continental extrusion of the Anatolian Plate caused by final collision of the Arabian Plate with the Eurasian Plate. © 2001 Éditions scientifiques et médicales Elsevier SAS