Tectono-sedimentary events and geodynamic evolution of the Mesozoic and Cenozoic basins of the Alpine Margin,Gulf of Tunis,north-eastern Tunisia offshore

The structural pattern, tectono-sedimentary framework and geodynamic evolution for Mesozoic and Cenozoic deep structures of the Gulf of Tunis (north-eastern Tunisia) are proposed using petroleum well data and a 2-D seismic interpretation. The structural system of the study area is marked by two sets of faults that control the Mesozoic subsidence and inversions during the Paleogene and Neogene times: (i) a NE-SW striking set associated with folds and faults, which have a reverse component; and (ii) a NW–SE striking set active during the Tertiary extension episodes and delineating grabens and subsiding synclines. In order to better characterize the tectono-sedimentary evolution of the Gulf of Tunis structures, seismic data interpretations are compared to stratigraphic and structural data from wells and neighbouring outcrops. The Atlas and external Tell belonged to the southernmost Tethyan margin record a geodynamic evolution including: (i) rifting periods of subsidence and Tethyan oceanic accretions from Triassic until Early Cretaceous: we recognized high subsiding zones (Raja and Carthage domains), less subsiding zones (Gamart domain) and a completely emerged area (Raouad domain); (ii) compressive events during the Cenozoic with relaxation periods of the Oligocene-Aquitanian and Messinian-Early Pliocene. The NW–SE Late Eocene and Tortonian compressive events caused local inversions with sealed and eroded folded structures. During Middle to Late Miocene and Early Pliocene, we have identified depocentre structures corresponding to half-grabens and synclines in the Carthage and Karkouane domains. The north–south contractional events at the end of Early Pliocene and Late Pliocene periods are associated with significant inversion of subsidence and synsedimentary folded structures. Structuring and major tectonic events, recognized in the Gulf of Tunis, are linked to the common geodynamic evolution of the north African and western Mediterranean basins.     

阿尔泰南缘麦兹泥盆纪火山-沉积盆地成矿特点及其铅锌、铁、金找矿潜力分析

麦兹盆地位于西伯利亚板块南缘阿尔泰陆缘活动带中,是一个重要的铅、锌、铁矿化集中区,其中著名的有蒙库大型铁矿床、可可塔勒大型铅锌矿床,是阿尔泰南缘多金属成矿带中最重要的成矿盆地之一。盆地内矿床、矿点多为火山喷流热水沉积成因,层控特征明显,具有规模大、形态规则、厚度及有用组分稳定等特点。铁矿成矿与早泥盆世早期细碧角斑质火山作用相伴,而铅锌成矿则与早泥盆世晚期长英质火山喷流沉积作用相伴。通过对麦兹盆地成矿地质特征和典型矿床中矿体分布变化规律的研究,认为北西向同生断裂、火山沉积洼地、火山喷发中心(火山机构)共同控制铅锌矿的产出,矿体还受到后期褶皱、变质作用的改造。根据有利层位、火山岩相、喷流沉积岩、热液蚀变、矿化组合、铁帽、控矿构造和地球化学异常等综合找矿评价标志,分析了可可塔勒矿区深部、什根特、铁热克萨依、H-48号异常的铅锌找矿潜力,并探讨了盆地内铁、金的找矿潜力,指出了进一步找矿的方向与有利地段。     

A Miocene-restricted platform of the Zibane zone (Saharan Atlas,Algeria), depositional sequences and paleogeographic reconstruction

Depositional sequences and paleogeographic evolution of the Miocene deposits have been studied in the Zibane zone (Saharan Atlas, Algeria) located at the north of the African platform. During the Miocene, this region corresponded to a fault-bounded collapse area and filled by diversified deposits, showing important lateral facies and thicknesses variations. The studied deposits are divided into five depositional sequences separated by major unconformities. These depositional sequences are well developed in the whole basin and testify a paleogeographic differentiation from E–W, induced by a set of NW-SE-trending old faults inherited from the Atlasic orogeny. The organization and the development of those sequences make it possible to correlate them better to the basin scale, which is integrated in a model of restricted platform intersected by NW-SE faults where the tectonic-sedimentation duality is predominant. These new data point to a paleogeographic evolution different from the one usually admitted environment for this region during Miocene time and plead in favour of a reconsideration of the depositional environments of the post-Burdigalian formations in the Zibane zone of the Algerian Atlasic domain.     

杭州湾地区长兴-奉化断裂的展布及中新生代活动特征研究

长兴-奉化断裂是斜跨杭州湾地区的一条新生代北西向断裂,改造了该地区印支运动以来北东向为主的构造格局,对区域矿产资源开发、油气勘探有着重要意义。由于该断裂在航磁异常图上表现不明显,地表行迹不连续,且极易与早期断裂的次级断裂混淆,因此该断裂的存在及其几何展布一直有所争议。本文结合杭州湾地区的TM遥感图像解译、布格重力异常场、以及人工地震勘探资料,分析长兴-奉化断裂的几何展布及中新生代活动特征,提出长兴-奉化断裂西起长兴煤山,经桐乡、海宁、余姚、宁波,向东南延伸入海,而非前人据航磁异常提出的自长兴向奉化地区延伸。TM遥感影像解译表明该断裂是由一系列新生的北西向小断裂呈右阶斜列、平行或断续出现所构成,断错了先存的北东向、东西向构造。人工地震资料显示自白垩纪至古近纪,长兴-奉化断裂均有活动,参与控制了杭州湾地区白垩纪-古近纪陆相盆地的沉积。该断裂在地表和剖面上表现为右旋张扭,是中国东部地区北西向断裂系统带的一部分。     

西北地区侏罗纪原始沉积区恢复

通过边缘相分析、地层接触关系分析、古水流系统分析和构造格架分析并结合侏罗系残余露头与残余沉积体系分布,对早-中侏罗世和中-晚侏罗世的原始沉积区进行了恢复,发现早-中侏罗世的沉积范围要比现今残存的沉积范围大得多,而中-晚侏罗世的沉积范围与现今残存的沉积范围相比则变化不大。     

The effect of Meso-Cenozoic tectonic processes on the formation of Upper Jurassic and Cretaceous hydrocarbon pools in the north of the Aleksandrov arch (West Siberia)

The effect of tectonic processes on the petroleum potential of the Upper Jurassic and Cretaceous sediments is estimated by the example of the deposits in the north of the Aleksandrov arch. The formation history of the structures bearing Upper Jurassic and Cretaceous hydrocarbon (HC) pools is discussed.The results obtained lead to the conclusion that anticlinal traps complicated by faults cutting the Meso-Cenozoic sedimentary cover are the most promising for the formation of large HC pools in Cretaceous sand reservoirs. These traps serve as channels for HC migration from the oil-producing rocks of the Bazhenovo Formation into the overlying reservoirs. In the Upper Jurassic sediments, anticlinal traps free from Cenozoic faults are the most promising for HC accumulation. These conclusions are confirmed by a number of examples.     

The role of E–W basement faults in the Mesozoic geodynamic evolution of the Gafsa and Chotts basins,south-central Tunisia

The Gafsa and Chotts intracratonic basins in south-central Tunisia are transitional zones between the Atlasic domain to the north and the Saharan platform to the south. The principal aim of this paper is to unravel the geodynamic evolution of these basins following an integrated approach including seismic, well log and gravity data. These data are used to highlight the tectonic control on the deposition of Jurassic and Lower Cretaceous series and to discuss the role of the main faults that controlled the basin architecture and Cretaceous–Tertiary inversion. The horizontal gravity gradient map of the study area highlights the pattern of discontinuities within the two basins and reveals the presence of deep E–W basement faults. Primary attention is given to the role played by the E–W faults system and that of the NW–SE Gafsa fault which was previously considered active since the Jurassic. Facies and thickness analyses based on new seismic interpretation and well data suggest that the E–W-oriented faults controlled the subsidence distribution especially during the Jurassic. The NW–SE faults seem to be key structures that controlled the basins paleogeography during Late Cretaceous–Cenozoic time. The upper Triassic evaporite bodies, which locally outline the main NW–SE Gafsa fault, are regarded as intrusive salt bodies rather than early diapiric extrusions as previously interpreted since they are rare and occurred only along main strike-slip faults. In addition, seismic lines show that Triassic rocks are deep and do not exhibit true diapiric features.     

有关贵州成矿研究中的几个问题讨论

很多矿产都产于不整合面及其附近，常见的有油气、金、铀、铅锌、铜、锑与铂族元素等，不整合面与成矿的关系值得深入研究。作认为，不整合面不仅是成矿热液运移的通道和储矿的空间，且是一种容易失稳的界面，在后期的构造活动演化过程中，常形成走向弯曲的拆离断层带和韧性与脆性变形并存的韧性剪切带，进而驱动矿液运移和沉淀。不整合面类型不同，矿体形态和产出特征也不同，不整合面附近多形成一些中低温热液矿床。清墟洞组是贵州铅锌、汞和铀矿的重要赋矿层位，其原因是该地层成矿元素丰度较高，地层上部有透水性低的“地球化学障”，下部有与断裂相通的“矿源层”，一般都沿深大断裂发育的背斜轴部出露。银厂坡矿床的地质地球化学特征与其附近的会泽的矿山厂、麒麟厂(超)大型铅锌矿床非常相似，预测其深部具有良好的找矿前景。     

Fractal modeling and relationship between thrust faults and carbonate-hosted Pb-Zn mineralization in Alborz Mountains,Northern Iran

Central Alborz Metallogenic Belt is a major mineral province of northern Iran placed at the northern margin of the Arabia-Eurasia collision zone. This study aimed to at recognition the affiliation between reverse/thrust faults and Pb-Zn carbonate-hosted mineral deposition using fractal modeling. Thrusting is the major mechanism of faulting in this region in terms of length, frequency and density. The carbonate-hosted Pb and Zn occurrence/deposit were classified using the concentration-number fractal method. All faults then are categorized based on fault density, and concentration-area fractal methods are utilized for the thrust faults. According to our analysis, main fault density zones are situated at the central and western parts of the Alborz Mountains. Relationship among the major fault density zones and the Pb-Zn carbonate-hosted occurrences/deposits using logratio matrix reveals that there is a proper connection between reverse/thrust faults and the Zn-Pb carbonate-hosted occurrences/deposits. Moreover, the results were controlled by four ore deposits/prospects in this region which shows high-grade ores directly relate to faults especially reverse/thrust faults based on their distribution. This research indicates that this method can be used for other various ore deposit types that have been distributed by faulting.     

黔西北矿集区亮岩铅锌矿区成矿构造解析

亮岩铅锌矿是川滇黔接壤区黔西北铅锌矿集区的典型矿床之一。基于矿田地质力学理论与方法,通过对该矿床三个中段出露的垭都—蟒硐断裂带结构进行精细解析,综合矿床地质特征和区域构造分析,认为该区至少历经了三期构造成生发展过程,相应的主压应力方向依次变化为北西向→北东向→东西向,其中在成矿期主要受北西—南东向挤压作用,为北东构造带。因该断裂带走向变化,在其不同部位的力学性质相应发生改变,导致矿体赋存特征存在明显差异。结合黔西北矿集区内其它典型矿床控矿构造的对比研究,发现这些矿床具有相似的构造控矿规律,而且与滇东北矿集区会泽型（HZT）铅锌矿均受到统一的构造应力场控制。不同于垭都—蟒硐成矿带在成矿期受北西构造带构造体系控制的传统观点,该新认识认为燕山期北东—西南向挤压作用所形成的北西构造带构造体系为成矿后构造（破矿构造）。这些认识为该区乃至黔西北矿集区深部找矿预测提供了重要启示。      

Boron-polymetallic metallogeny of the north and northeast of the Sino-Korean Craton

Based on published data and original investigations, it has been shown that the combination of widely known Ag, Fe, and Fe-Mn ore deposits, as well as boron and Pb-Zn world-class deposits, is typical for metallogenic zones in the north and northeast of the Sino-Korean Craton. The ore genesis was spatially inherited and lasted from the Archean to Mesozoic. The Archean metallogenic zones are related to the protocontinental margin terranes of the craton basement and they comprise banded iron ore and Cu-Zn sulfide deposits. The proterozoic-Early Paleozoic metallogenic zones are related to rift basins, where the ore-bearing Archean folded basement is overlain by volcanic and sedimentary complexes. The Proterozoic metallogenic zones host quartz veins and schistosity zone-related Au deposits, banded iron and Cu-Zn ore deposits, large sedimentary-metamorphogenic borate and magnesite deposits, Cu-W deposits in tourmalinites, exhalation-sedimentary Pb-Zn ore deposits, and large polygenic REE-Fe-Nb ore deposits. The Riphean-Cambrian terrigenous-carbonate strata are represented by stratiform Pb-Zn and fluorite deposits. Mesozoic metallogenic zones related to volcano-plutonic complexes of intraplate series coincide with zones where the folded basement is made of Precambrian ore-bearing series. Gold deposits are typical of all the metallogenic zones, but most of them are related to Mesozoic volcano-plutonic complexes.     

贵州五指山铅锌矿田深部找矿远景分析

贵州五指山铅锌矿田发育北东向、北东东向和北西向断层,分别平行于区域性安顺-贵阳、纳雍-息烽及水城-紫云深大断裂,控制了寒武纪-泥盆纪时期的沉积相和石炭纪前的地层剥蚀程度,以及沉积盆地中成矿流体活动。矿田中的那雍枝矿床的矿体产状、矿石结构构造、围岩蚀变及元素地球化学特征,反映其具有海底喷流沉积矿床成因。矿田深部地球物理场显示,矿田及附近存在北东向、北西向和东西向深大断裂,在几组断裂交汇处及附近的深部存在岩浆岩体及大型岩基,具备深部流体上升的条件。推测那润断层北盘那雍枝矿床深部灯影组内,F9、F10与F1断层相交,灯影组和清虚洞组层位及对应的物化探异常变异区的深部应存在大型层状铅锌矿体,具有超大型铅锌矿床的找矿前景。     

层、相、位对广西北山银、锌、镉、黄铁矿矿床的控制作用探讨

一、概述本矿床是一个以银、锌、镉、黄铁矿为大型,铅为中型的硫化物矿床。它兼有我国南方泥盆系碳酸盐岩层控铅—锌矿床和层控黄铁矿矿床的主要地质特征,是一个研究典型层控矿床和成矿理论不可多得的矿床,因此不少专家学者前往参观考察。矿床位于扬子准地台东南缘,在南华后加里东准地台上,处于“江南古陆”南端西南缘,桂中褶断束的北西段,于南岭多金属成矿带西端,属北山—泗顶铅、锌、黄铁矿成矿远景区的西段。矿床周围出露大片泥盆系和石炭系,它的北部和东部是江南古陆,出露有四堡群、板溪群、震旦系及零星分布的寒武系,西北角和南西偶有二叠系出露。     

Inverted intracontinental basin and vertical tectonics: The Saharan Atlas in Tunisia

The present-day architecture of the Saharan Atlas in Tunisia can be defined by two principal models: (1) The first model emphasizes a general SW–NE geological structure in the North forming successive and parallel bands (the Tellian zone, the diapir zone) and the central Atlas, which are cut by the southern Atlas ranges located within a NW–SE corridor. These zones are bordered to the East by the “North–South Axis”. (2) The second model defines the Tunisian Atlas in terms of an E–W strike-slip corridor, which initially controls the sedimentary facies distribution during the Meso-Cenozoïc, and which then generates elongate en echelon folds in the sedimentary cover by dextral shearing.In this study, we aim to show that the Saharan Atlas in Tunisia appears today as a triangular megablock, that we call the Tunisian Block (TB), bounded by three structural trends (N–S, SW–NE and NW–SE) belonging to the African strike-slip fault network: (1) The eastern boundary appears as a complex faulted and folded corridor limiting the folded zone of the central Atlas in the West and the depressed zone of the Sahel in the East: it corresponds to the “North–South Axis” as defined classically in the literature. (2) The southern boundary also corresponds to a faulted belt (Gafsa–Negrine-Tozeur corridor), which cuts off the continuation of the North–South axis southward into the Gabès region; it corresponds to the Southern Saharan Atlas, delimited by the Gafsa fault in the North and the Negrine-Tozeur fault in the South. (3) The northern boundary, trending SW–NE, appears rather in the form of a reverse tectonic bundle, facing SE or S (oblique convergence), whose major feature corresponds to the El Alia-Téboursouk fault. This northern boundary cuts across and delimits the N–S corridor towards the North, in such a way that its extension is limited at both extremities. Finally, the inner part of the TB actually corresponds to a mosaic of second-order blocks, each of which contains an arrangement of widely spaced SW–NE trending anticlines forming the main relief separated by vast plains very often occupied by sebkhas. The paleogeographic and structural evolution of this region during the Mesozoic and Palaeogene shows that the TB, along with its limits as defined here, developed an increasingly distinct identity at a very early stage, being characterized by an extensive and/or transtensive tectonic regime. Finally, the Tunisian Atlas Chain defines a triangular domain that owes its origin and particular character precisely because of the paleogeographic and structural history of this paleoblock. The boundaries of this paleoblock remain mobile, thus tectonically controlling the geometry and morphology of a typical intracontinental basin. The extension directions and the frequent changes of stress regime (or rotations) are related to the existence of two active basins: the strike-slip margin of the western branch of Tethys and the Mesogea oceanic basin, with tectonic activity becoming alternately dominant in one or other of the basins at different times. In this context, the Tunisian basin is characterized by rhythmic sedimentation, composed of a succession of filling sequences linked to the continuing tectonic instability of the sedimentary floor associated with two major crises: one at the end of the Aptian and the other at the end of the Ypresian. The vertical movements related to the extension and/or transtension of the blocks is accentuated by Triassic salt tectonics, giving rise to linear (salt axes) or point (salt domes) structures that lead to the formation of shoal zones during development of the basin, thus enhancing the vertical tectonics. The diapirism developed slowly and gradually from late Triassic through to Langhian times, leading to numerous sedimentary wedges on the flanks of the structures. The uprise of the diapirs exhibits three pauses corresponding to the end-Aptian, end-Ypresian and pre-Burdigalian. The vertical tectonics is characterized by abundant drape folds giving rise to an extensional fault-related folding and strike-slip/dip-slip faults creating frequent unconformities that are nevertheless always localized.Finally, the folded chain results from the structural inversion of this paleoblock from Tortonian times onward. We can only account for the various folds-axis directions in the context of an intracontinental chain where the pre-existing major vertical faults are able to develop on the surface as draped-folds in a transpressive regime by the local reorientation of stresses in crustal-scale faults. In detail, the structures produced by this vertical tectonic activity, which are profoundly controlled by inheritance, display a highly original style at very shallow levels in the crust.     

Seismic tectono-stratigraphy of fluvio-deltaic to deep marine Miocene silicoclastic hydrocarbon reservoir systems in the Gulf of Hammamet,northeastern Tunisia

Most of hydrocarbon accumulations within the Gulf of Hammamet foreland basins in eastern Tunisia are reservoired within the Upper Miocene Birsa and Saouaf sandstones. It is the case of Birsa, Tazarka, Oudna, Baraka, Maamoura, Cosmos and Yasmine fields. These sandstones constitute oil and gas fields located on folded and faulted horst anticline highs and described as varying from shoreface to shallow marine and typically exhibit excellent reservoir quality of 30 to 35% porosity and good permeability from 500 to 1100 md. In addition, the fracturing of faults enhanced their reservoir quality potential. However, due to the lack of seismic stratigraphic studies to highlight depositional environment reservoir characterization and distribution, petroleum exploration faces structural and stratigraphic trap types and remains on targeting only high fold closures with limited reserve volumes of hydrocarbons. As an example of the Birsa concession case, syn-sedimentary tectonic structuring and geodynamic evolution during Middle to Upper Miocene Birsa reservoir sequences have guided the distribution of depositional environment of sandstone channel systems around horst and grabens by E-W, NE-SW and N-S strike slip flower faults controlling the subsidence distribution combined with the eustatic sea level variations. Seismic sequence stratigraphy study of Miocene Birsa reservoir horizons, based on the analysis and interpretations of E-W and N-S 3D selected regional lines that were compared and correlated to outcrops and calibrated by well data, permitted to highlight the basin configuration and sequence deposit nature and distribution. Sedimentary infilling of the basin from Langhian Ain Ghrab carbonate to Serravallian Tortonian Birsa and Saouaf sandstone and shale formations is organized in four third-order seismic sequences, limited by regional erosional toplap, onlap and downlap unconformity surfaces and by remarkable chronostratigraphic horizons of forced and normal erosive lowstand and highstand system tracts separated by transgressive and maximum flooding surfaces. Reconstructed sedimentary paleo-environment distribution vary from deltaic fluvial proximal deposits in the northern part of the high central Birsa horst to a delta front and prodelta coastal and shelf shore face and shore line channelized deposits in the surrounding borders of grabens. Distal deposits seem to be distributed from upper to lower slope fans and probably to the basin floor on the flanks of the subsiding grabens. Synthetic predictive paleogeographic depositional reservoir fairway map distribution of Lower, Middle and Upper Birsa sandstone reservoirs highlights four main domains of channelized superposed and shifted reservoirs to explore.     

西昆仑甜水海地区铅锌矿成矿特征及找矿进展

新疆和田火烧云铅锌矿的发现,标志着我国铅锌找矿在西昆仑甜水海地区取得了重大突破,区内目前已发现铅锌矿床（点）29处,其中铅锌矿中型矿床7个、大型矿床2个、超大型矿床1个。通过收集整理区内最新的矿产地质勘查成果资料,对该区带内铅锌矿的成矿特征、找矿前景进行系统分析与总结,将区内铅锌矿床划分为密西西比河谷型(MVT)和沉积喷流型(SEDEX) 2个大类和4个具体类型,认为它们的成矿过程分别与区域大地构造演化、区域断裂活动及同沉积断层-喷流沉积活动密切相关,在矿体形态、矿石矿物、矿石结构构造等矿化特征及成矿模式方面均有明显差异。火烧云式是受中侏罗统龙山组上段灰岩-白云岩沉积层位控制的沉积喷流型铅锌矿,化石山式是受中侏罗统龙山组铁锰质沉积层位控制的沉积喷流型铅锌矿,多宝山式是受断裂构造控制的碳酸盐岩建造中的MVT型铅锌矿,元宝岭式是受北东向左行张扭性断裂控制的碎屑岩建造中的MVT型铅锌矿。     

Metallogenic ‘factories’ and resultant highly anomalous mineral endowment on the craton margins of China

The current margins of the North China and Yangtze Cratons provide arguably the best examples globally of anomalously high mineral endowment within a 100 km buffer zone, hosting 66 diverse world-class to giant ore systems that help explain China’s premier position as a producer of multiple metal and mineral commodities. After the cratonization of these crustal blocks during the Neoarchean-Paleoproterozoic, with incorporation of iron ores on assembled micro-block margins, the margins of the cratons experienced multiple convergence and rifting events leading to metasomatism and fertilization of their underlying sub-continental lithospheric mantle. The rifted margins with trans-lithosphere faults provided pathways for Cu-Au (Mo-W-Sn)-bearing felsic to Ni-Cu-bearing ultrabasic intrusions and REE-rich carbonatite magmas, and for the development of marginal sedimentary basins with both Cu-Pb-Zn-rich source units and reactive carbonate or carbonaceous host rocks. There was diachronous formation of hydrothermal orogenic gold, antimony, and bismuth systems in the narrow orogenic belts between the cratons. Complexity in the Mesozoic Paleo-Pacific subduction systems resulted in asthenosphere upwelling and lithosphere extension and thinning in the North China Craton, leading to anomalous heat flow and formation of orogenic gold deposits, including those of the giant Jiaodong gold province on its north-eastern margin. These gold deposits, many of which formed from fluids liberated by devolatilization of previously metasomatized sub-continental lithospheric mantle, helped propel China to be the premier gold producer globally. The thick sub-continental lithospheric mantle of the cold buoyant cratons helped the preservation of some of the world’s oldest porphyry-skarn and epithermal mineral systems. Although craton margins globally control the formation and preservation of a diverse range of mineral deposits, China represents the premier example in terms of metal endowment due to the anomalous length of its craton margins combined with their abnormally complex tectonic history.     

湖南省南部泥盆系中统棋梓桥组Pb.Zn.Fe.Mn含量特征

湖南南部地区(以下简称湘南)棋梓桥组广泛分布(图1),是一个重要的含铅锌矿层位。据最近统计,湘南有1/3的铅锌矿床(点)产于此层位中。棋梓桥组本身的厚度(47—1048米)相对于全区地层总厚(933—27808米)是微不足道的,可是却能集中如此之多的矿床(点),自然要引起人们的重视。近年来,随着层控矿床研究的深入,人们自然就把它与成矿相联系,也就是说把它看作是矿源层或就矿层。作为就矿层这是毋庸置疑的,作为矿源层     

黔西南普安铅锌矿区盆地尺度构造

贵州省普安铅锌矿区位于华南褶皱带西北缘的黔西南坳陷,矿体主要赋存在石炭系的白云质灰岩和白云岩中,构造控矿特征显著.NW-SE走向的二维地震剖面横穿了铅锌矿区,清晰地揭示了矿区的地层和NE向构造格架.从浅层的泥盆系至深层的新元古界,共标定了3个反射层和3个反射单元,据两个重要角度不整合面,矿区呈现为双层基底、单层盖层的"...     

非活动大陆边缘的天然气水合物及其成藏过程述评

非活动陆缘是板块活动相对较弱的地区，也是水合物发育的有利地区。通过对世界各地非活动陆缘地区水合物富集情况的系统分析，发现断褶组合构造、底辟构造以及“麻坑”地貌（Pockmark)与水合物的关系密切。尽管模拟海底反射层（Bottom Simulating Reflector,简称BSR，下同）是最重要的水合物识别标志，但水合物与BSR之间并不存在严格的一一对应关系。非活动陆缘具有丰富的烃类物质来源和适宜的温压条件，而断裂－褶皱组合构造、垒堑式构造和底辟构造等则为烃类气体的运移、富集和成藏提供了有利的构造环境，便于最终形成水合物。非活动陆缘的深水区往往发育有多期叠合盆地，因其物源、温压、构造和沉积条件的内在关联性，常常形成深部石油、中部天然气、浅部水合物的“三位一体”烃类能源结构模式。