Heat flow in salt-dome basins of Eurasia: A comparative study

The geothermal fields in the Pericaspian, Pripyat, and North German basins are considered. These basins are characterized by widespread Upper Paleozoic evaporite sequences, which underwent halokinesis with the formation of salt domes and plugs owing to tectonic and gravity instability. Heat flow refraction occurs at the boundaries of the domes with country rocks due to the contrast in thermal conductivity of evaporites and terrigenous rocks between the domal zones. This is the main cause of heat flow variation in the lateral and vertical directions in the salt-dome basins. Close correlation between zones of elevated temperature in the sedimentary rocks and petroleum occurrences is confirmed by the results of 2D and 3D modeling of the geothermal field. The previously noted relations of oil and gas fields to the deep faults in the studied basins create prerequisites for consideration of the geothermal field as a genetic factor controlling the tectonic features and petroleum resources of the salt-dome basins.     

Obliteration of thermal springs by groundwater flows in sedimentary basins of Brazil

Analysis of geothermal and hydrogeologic characteristics of Paleozoic interior basins of Brazil has identified an association between the geographic distribution of thermal springs and areas of occurrences of groundwater flow. Specifically, thermal springs are found to be absent in regions inferred to have lateral flows of groundwater. This trend is evident in the basins of the Amazon region, in the central parts of the Parnaíba basin and in the west-central parts of the Paraná basin. Model studies help to elucidate mutual exclusion of regions of thermal springs and sub-horizontal flows of groundwater. Numerical simulations indicate that groundwater flows with velocities ≥ 1 cm/year are capable of masking the occurrence of thermal anomalies. Also, down flow through distributed recharge zones can lead to development of large zones of relatively low temperature. The observational data sets of temperature gradients and Peclet numbers have been employed outlining advection-convection domains of subsurface strata in the sedimentary basins of the Amazon region, Parnaíba and Paraná. Results obtained indicate that thermal buoyancy forces are incapable of overcoming advective flows in basins of the Amazon region. Similar conditions are also found to prevail in the central parts of the Parnaíba and Paraná basins.     

The evolution of Central Asiatic geosynclines through sea-floor spreading

Late Precambrian-Early Paleozoic and Middle Paleozoic oceanic basins are reconstructed in the orogenic belt of Central Asia. These basins coincide with eugeosynclinal ophiolites which can be considered as remnants of a former oceanic floor. As these ophiolites are of decreasing age from the edges of the eugeosynclinal zones toward their centres, one can assume the creation of an ancient oceanic basin by a sea-floor spreading process. Restored oceanic basins can be considered as analogues of present marginal and inland seas. The distinct structural-magmatic zonal pattern came into existence during the generation of a given oceanic basin. This pattern appears to be governed by the ancient Benioff zone along which energy and light lithophile substance ascended as mantle diapir.     

Continental margins as global oil-accumulation belts: The Gondwana belt

Most present-day petroliferous basins are localized in one of the five global oil and gas accumulation belts confined to continent—ocean transition zones that existed in the Mesozoic and Cenozoic. The Gondwana belt is formed by basins developed on continental margins of the Indian Ocean and South Atlantic (Konyukhov, 2009). All of them are riftogenic in nature and were formed during either the Late Paleozoic (basins on continental margins of the Indian Ocean) or the Late Mesozoic (basins in peripheral zones of the South Atlantic). During the most part of geological history, they were located in zones dominated by the humid climate, which determined the prevalent role of terrigenous rocks in their sedimentary cover.     

The variability of heat flow both regional and with depth in southern Alberta, Canada: Effect of groundwater flow?

Detailed studies of terrestrial heat flow in southern and central Alberta estimated on the basis of an order of magnitude larger data base than ever used before (33653 bottom-hole temperature data from 18711 wells) and thermal conductivity values based on detailed rock studies and measured rock conductivities show significant regional and local variations and variations with depth. Heat flow values were estimated for each 3 × 3 township/range area (28.8 × 28.8 km). A difference in heat flow exists between Paleozoic and Mesozoic strata. Generally lower heat flow values are observed in the strata above the Paleozoic erosional surface (20–75 mW m⁻²). Much higher values are estimated for the Younger Paleozoic formations, with large local and regional variations between 40 and 100 mW m⁻².Average heat flow values based on heat flow determinations below and above the Paleozoic surface that agree within 20% show an increase from values less than 40 mW m⁻² in southern and southwestern Alberta to values as high as 70 mW m⁻² in central Alberta. The predominance of regional downward groundwater flows in Mesozoic strata seem to be responsible for the generally observed heat flow increase with depth.The results show that the basin heat flow pattern is influenced by water movement and even careful detailed heat flow measurements will not give correct values of background steady-state heat flow within the sedimentary strata.     

Lithosphere structure of European sedimentary basins from regional three-dimensional gravity modelling

A three-dimensional (3D) density model, approximated by two regional layers—the sedimentary cover and the crystalline crust (offshore, a sea-water layer was added), has been constructed in 1° averaging for the whole European continent. The crustal model is based on simplified velocity model represented by structure maps for main seismic horizons—the “seismic” basement and the Moho boundary. Laterally varying average density is assumed inside the model layers. Residual gravity anomalies, obtained by subtraction of the crustal gravity effect from the observed field, characterize the density heterogeneities in the upper mantle. Mantle anomalies are shown to correlate with the upper mantle velocity inhomogeneities revealed from seismic tomography data and geothermal data. Considering the type of mantle anomaly, specific features of the evolution and type of isostatic compensation, the sedimentary basins in Europe may be related into some groups: deep sedimentary basins located in the East European Platform and its northern and eastern margins (Peri-Caspian, Dnieper–Donets, Barents Sea Basins, Fore–Ural Trough) with no significant mantle anomalies; basins located on the activated thin crust of Variscan Western Europe and Mediterranean area with negative mantle anomalies of −150 to −200×10⁻⁵ ms⁻² amplitude and the basins associated with suture zones at the western and southern margins of the East European Platform (Polish Trough, South Caspian Basin) characterized by positive mantle anomalies of 50–150×10⁻⁵ ms⁻² magnitude. An analysis of the main features of the lithosphere structure of the basins in Europe and type of the compensation has been carried out.     

Evolution and deep structure of the Zeya-Bureya and Songliao sedimentary basins (East Asia)

The evolution and deep structure of the Songliao and Zeya-Bureya basins can be divided into the rift, platform (subsidence), and neotectonic phases. The rift phase (Middle Jurassic-Early Cretaceous) climaxed at the formation of a basin-wide near N-S-oriented rift system, which was followed (Late Cretaceous) by the deposition of the deep-water organic-rich lacustrine source facies with the maximum thickness identified in the Songliao basin (up to 1100 m). The neotectonic phase was marked by the pronounced differences in the basin’s development caused by the formation of a series of E-W-trending transverse structures, which eventually separated the basins, changed the drainage pattern, and blocked the rivers draining southwards from the Zeya-Bureya to the Songliao basin. The differences in the deep structure of the basins are also strongly pronounced. High heat flow values of more than 70 mW/m² are typical of the Songliao basin, and its mantle heat flow component is higher than the crustal one, as compared to the Zeya-Bureya basin (below 50 mW/m²). The crustal thickness of the Zeya-Bureya basin is higher than that of the Songliao basin (38–42 km and 29–34 km) with a lithospheric thickness of 110–140 km and 50–75 km, respectively. The only exception is the southern Zeya-Bureya basin, which has an electrical structure similar to that of the Songliao basin. These differences have important implications for the evaluation of the hydrocarbon potential of the rift basins. It was suggested that the evaluation of the hydrocarbon potential of the sedimentary basins or parts of these basins should account for two factors: (1) the influence of the lithospheric motions and the related collisional processes and (2) the anomalies in the deep lithospheric structures (the high heat flow and the reduced crustal and lithospheric thickness). The results of this study indicate that the southern part of the Zeya-Bureya basin (in particular, the Lermontovka, Dmitrievka, Mikhailovka, Ekaterinoslavka, and Arkhara troughs) is interpreted to have a fairly high hydrocarbon potential.     

Absence of a regional surface thermal high in the Baikal rift; new insights from detailed contouring of heat flow anomalies

Heat flow in active tectonic zones as the Baikal rift is a crucial parameter for evaluating deep anomalous structures and lithosphere evolution. Based on the interpretation of the existing datasets, the Baikal rift has been characterized in the past by either high heat flow, or moderately elevated heat flow, or even lacking a surface heat flow anomaly. We made an attempt to better constrain the geothermal picture by a detailed offshore contouring survey of known anomalies, and to estimate the importance of observed heat flow anomalies within the regional surface heat output. A total of about 200 new and close-spaced heat flow measurements were obtained in several selected study areas in the North Baikal Basin. With an outrigged and a violin-bow designed thermoprobe of 2–3-m length, both the sediment temperature and thermal conductivity were measured. The new data show at all investigated sites that the large heat flow highs are limited to local heat flow anomalies. The maximum measured heat flow reaches values of 300–35000 mW/m², but the extent of the anomalies is not larger than 2 to 4 km in diameter. Aside of these local anomalies, heat flow variations are restricted to near background values of 50–70 mW/m², except in the uplifted Academician zone. The extent of the local anomalies excludes a conductive source, and therefore heat transport by fluids must be considered. In a conceptual model where all bottom floor heat flow anomalies are the result of upflowing fluids along a conduit, an extra heat output of 20 MW (including advection) is estimated for all known anomalies in the North Baikal Basin. Relative to a basal heat flow of 55–65 mW/m², these estimations suggest an extra heat output in the northern Lake Baikal of only 5%, corresponding to a regional heat flow increase of 3 mW/m². The source of this heat can be fully attributed to a regional heat redistribution by topographically driven ground water flow. Thus, the surface heat flow is not expected to bear a signal of deeper lithospheric thermal anomalies that can be separated from heat flow typical for orogenically altered crust (40–70 mW/m²). The new insights on the geothermal signature in the Baikal rift once more show that continental rifting is not by default characterized by high heat flow.     

Cordilleran Intermontane thermotectonic history and implications for neotectonic structure and petroleum systems,British Columbia,Canada

Heat flow increases northward along Intermontane Belt in the western Canadian Cordillera, as shown by geothermal differences between Bowser and Nechako sedimentary basins, where geothermal gradients and heat flows are ∼30 mK/m and ∼90 mW/m² compared to ∼32 mK/m and 70 –80 mW/m², respectively. Sparse temperature profile data from these two sedimenatary basins are consistent with an isostatic model of elevation and crustal parameters, which indicate that Bowser basin heat flow should be ∼20 mW/m² greater than Nechako basin heat flow. Paleothermometric indicators record a significant northward increasing Eocene or older erosional denudation, up to ∼7 km. None of the heat generation, tectonic reorganization at the plate margin, or erosional denudation produce thermal effects of the type or magnitude that explain the north–south heat flow differences between Nechako and Bowser basins. The more southerly Nechako basin, where heat flow is lower, has lower mean elevation, is less deeply eroded, and lies opposite the active plate margin. In contrast, Bowser basin, where heat flow is higher, has higher mean elevation, is more deeply eroded, and sits opposite a transform margin that succeeded the active margin ∼40 Ma. Differences between Bowser and Nechako basins contrast with the tectonic history and erosion impacts on thermal state. Tectonic history and eroded sedimentary thickness suggest that Bowser basin lithosphere is cooling and contracting relative to Nechako basin lithosphere. This effect has reduced Bowser basin heat flow by ∼10–20 mW/m² since ∼40 Ma. Neither can heat generation differences explain the northerly increasing Intermontane Belt heat flow. A lack of extensional structures in the Bowser basin precludes basin and range-like extension. Therefore, another, yet an unspecified mechanism perhaps associated with the Northern Cordilleran Volcanic Province, contributes additional heat. Bowser basin’s paleogeothermal gradients were higher, ∼36 mK/m, before the Eocene and this might affect petroleum and metallogenic systems.     

华北陆块新元古代-中生代沉积盆地划分及其构造演化

在华北陆块区进行构造-地层区划的基础上,对华北陆块中元古代-新元古代、早古生代、晚古生代、三叠纪-早侏罗世、中侏罗世-白垩纪5个大地构造阶段不同构造-地层区内的沉积盆地类型、充填序列和时空演化过程进行了分析、讨论.中-新元古代是华北周缘裂谷发育期.寒武纪-早、中奥陶世,华北广泛发生沉降并接受海侵,形成几乎广布全华北的碳酸盐岩台地.晚奥陶世-泥盆纪,华北整体抬升,遭受剥蚀,沉积缺失.石炭纪-二叠纪,华北陆块再次发生沉降并接受海侵,形成广阔的陆表海海陆交互相沉积,至晚二叠世华北陆块进入陆相盆地发展阶段.中生代,华北陆块陆内构造运动活跃,普遍形成与火山活动相伴的断陷盆地、坳陷盆地和拉分盆地.      

Petroliferous basins at continental margins of Paleozoic paleoseas: Communication 1. Petroliferous basins at margins of Iapetus and Panthalassa

Although large marine basins governing the fabric of our planet in the Paleozoic disappeared later (whether or not they were oceans is a debatable issue), sedimentary basins formed at continental margins at that time played a crucial role as depositories of various fossil minerals, including ores, salts, phosphorites, coal, bauxites, and construction materials. Many of these basins are oil- and gas-bearing structures. Their oldest representatives are confined to margins of Proterozoic/Paleozoic paleoseas (Iapetus and Panthalassa), whereas other basins appeared after opening of the Central Asian, Uralian, and Rheic (Paleotethys) deep-marine basins. Study of specific features of the sedimentary cover of such basins, rock composition therein, rocks and associated oil- and gas-bearing systems revealed that the Paleozoic planet was divided into two parts: Gondwana, with the major portion confined to high latitudes of the Southern Hemisphere; and other smaller near-equatorial continents. This pattern significantly governed the composition and mode of post-sedimentary transformations of natural reservoirs, as well as age and spatial distribution of the major hydrocarbon (HC) source sequences. Most Paleozoic oil- and gas-bearing basins make up specific belts because of their confinement to continental margins in paleoseas of that time.     

Temperature distribution and anomalies in the crystalline basement of the tataria arch

We made temperature measurements in the crystalline basement of the superdeep and deep boreholes located in the central-eastern part of the East European platform. The basement in the studied region is characterized by an average heat flow of 60 mW m⁻². Our experiments have revealed temperature anomalies in the crystalline basement that we interpreted as unconsolidated zones. The studies indicate that fluid injection anomalies, sheet flow and overflow zones and gas anomalies can be detected by temperature measurements.     

Fault-bounded blocks and their role in localising sedimentation and deformation adjacent to the alpine fault, southern New Zealand

Continental transform boundaries in detail consist of zones of fault-bounded blocks adjacent to the principal active transform fault(s). Relative movement of these blocks in response to plate boundary motions gives rise to differential vertical displacements of the earth's crust and hence exercises a degree of control on the tectonic evolution of sedimentary basins adjacent to the transform boundary. The Cenozoic sedimentary basins of southwest New Zealand have several features in common that may be attributed directly to the movement on the adjacent plate boundary. However, their location, detailed sedimentary evolution and tectonic development may best be understood in the context of the relative displacements of a number of fault-bounded blocks, in response to the plate motions. In particular, movements of the Fiordland block, bounded by the Alpine and Moonlight fault zones, exercised a large measure of influence on the development of the basins. The tectonic model presented is consistent with plate boundary motions inferred from marine magnetic anomalies while at the same time providing an explanation for many of the more detailed features of the basins.     

华北克拉通北缘与盆地流体有关的若干矿床实例

与华南一样,在华北克拉通北缘及其增生带也有与盆地流体有关的矿床产出。矿床的生成总是与张裂型沉积盆地有关。根据基底大地构造性质和盆地动力学演化特征,可划分出两个与盆地流体有关的、特征各异的金属成矿省：1)华北克拉通北部元古代金．多金属成矿省,在克拉通内部,边缘元古代裂谷增生期生成沉积喷流型硫多金属矿床和沉积岩容矿的微细浸染型金矿床;2)大兴安岭中南段古生代锡．多金属成矿省,在克拉通北缘早／晚古生代增生带的张裂型沉积盆地内分别生成各具特征的铅锌/锡-多金属矿床。     

南秦岭古生代热水沉积盆地与热水沉积成矿

扬子地块北部被动边缘的南秦岭古生代沉积盆地中,发育一套自早古生代—中生代以来的碳酸盐岩夹细碎屑岩沉积建造,形成规模巨大独具特色的以铅锌金为主的多金属成矿带。伸展构造体制下形成的裂陷或断陷型盆地中,正常水成沉积与热水沉积同盆共存。正常水成沉积中叠加的热水沉积是一个"突发事件或灾变事件",具有特殊的物质组成和产态。通过对区内沉积成矿盆地的识别、分级,二级沉积盆地中边缘部位常发育多个三级构造热水沉积成矿盆地,它受控于沉积盆地中的同生断裂,具有沉积岩相、热水沉积岩组合、显著成矿作用及物化探异常广布的特点。三级构造热水沉积成矿盆地是矿床定位的构造空间,四级热水沉积洼地为矿体(矿层)的容纳空间。区内热水沉积岩主要为重晶石(毒重石)岩、硅质岩、钠长石岩和铁碳酸盐岩类,铅锌重晶石等矿产多产于热水沉积岩中或上盘。热水沉积形成一般由早期的热水喷发交代→主期热水喷流→晚期热水喷气演变。早期的热水喷发交代往往沿矿液喷发通道,形成网脉状、角砾状矿化;主期热水喷流主要形成多金属及热水喷流相,形成块状、条带状、层纹状矿石或热水沉积岩;晚期热水喷气主要形成浸染状矿石和热水喷气岩石。     

Regional gravity survey and application in oil and gas exploration in China

Ground gravity survey for regional structure unit delineation and oil and gas exploration in China is addressed in this paper with examples. Gravity survey scales, coverage, technical regulations and achievements at the national level are introduced, including data processing and anomaly interpretation techniques. Bouguer anomalies of terrestrial territories of China and classification of anomalous feature zones are also described; they are well correlated with lithotectonical boundaries, fault zones, and unexposed igneous plutons. Recent study results of petroliferous sedimentary basins are presented as well, including concealed boundaries and major structures of large basins. It is concluded that gravity survey is the most effective and economic method in unveiling unexposed and deep-seated structures, targeting and delineating oil and gas-bearing sedimentary basins, and locating main trap structures within prolific basins in early stage of exploration in China. Suggestions for improving exploration of both conventional and unconventional oil and gas reservoirs in China are also given in the paper.     

Helium isotope compositions in sedimentary basins in China

The abundance and isotopic composition of He have been determined for a variety of natural gases (oil-field gases) in sedimentary basins in the continent of China. The³He/⁴He and⁴He/²⁰Ne ratios range from 0.004 to 4.99 Ra (where Ra denotes atmospheric³He/⁴He ratio = 1.4 × 10⁻⁶), and from 100-39,000, respectively. Helium in the gas sample is composed of mantle-derived He and crustal radiogenic He.The high³He/⁴He ratios were observed in the sedimentary basins which underwent Cenozoic extension in the eastern domain, such as the Songliao, Liaohe, North China, Subei, Sanshui and South China Sea basins. The basins where mantle-derived He is recognized are characterized by the presence of surface and subsurface volcanic rocks, high terrestrial heat flow, deep faults and thinned crust. On the other hand, regions which underwent pre-Tertiary extension such as the Jungar, Tarim, Tuba, Caidam and Yumen basins in the NW and tectonic loading such as the Ordos and Sichuan basins in the central domain are marked by almost pure radiogenic⁴He of crustal origin and thus by an apparent absence of mantle-derived He, which coincides with complete lack of Cenozoic volcanics, low terrestrial heat flow and thickened crust. Such a³He/⁴He distribution pattern clearly indicates that tectonic environment control the distribution of He isotopes in the continent of China.     

Meso–Cenozoic thermal regime in the Bohai Bay Basin,eastern North China Craton

This article discusses the Meso–Cenozoic thermal history, thermal lithospheric thinning, and thermal structure of the lithosphere of the Bohai Bay Basin, North China. The present-day thermal regime of the basin features an average heat flow of 64.5 ± 8.1 mW m^–2, a lithospheric thickness of 76–102 km, and a ‘hot mantle but cold crust’-type lithospheric thermal structure. The Meso–Cenozoic thermal history experienced two heat flow peaks in the late Early Cretaceous and in the middle to late Palaeogene, with heat flow values of 82–86 mW m^?2 and 81–88 mW m^?2, respectively. Corresponding to these peaks, the thermal lithosphere experienced two thinning stages during the Cretaceous and Palaeogene, reaching a minimum thickness of 43–61 km. The lithospheric thermal structure transformed from the ‘hot crust but cold mantle’ type in the Triassic–Jurassic to the ‘cold crust but hot mantle’ type in the Cretaceous–Cenozoic, according to the ratio of mantle to surface heat flow (q_m/q_s). The research on the thermal history and lithospheric thermal structure of sedimentary basins can effectively reveal the thermal regime at depth in the sedimentary basins and provide significance for the study of the basin dynamics during the Meso–Cenozoic.     

Reconstructing seafloor age distributions in lost ocean basins

Reconstructions of past seafloor age make it possible to quantify how plate tectonic forces,surface heat flow,ocean basin volume and global sea level have varied through geological time.However,past ocean basins that have now been subducted cannot be uniquely reconstructed,and a significant challenge is how to explore a wide range of possible reconstructions.Here,we investigate possible distributions of seafloor ages from the late Paleozoic to present using published full-plate reconstructions and a new,efficient seafloor age reconstruction workflow,all developed using the open-source software GPlates.We test alternative reconstruction models and examine the influence of assumed spreading rates within the Panthalassa Ocean on the reconstructed history of mean seafloor age,oceanic heat flow,and the contribution of ocean basin volume to global sea level.The reconstructions suggest variations in mean seafloor age of~15 Myr during the late Paleozoic,similar to the amplitude of variations previously proposed for the Cretaceous to present.Our reconstructed oceanic age-area distributions are broadly compatible with a scenario in which the long-period fluctuations in global sea level since the late Paleozoic are largely driven by changes in mean seafloor age.Previous suggestions of a constant rate of seafloor production through time can be modelled using our workflow,but require that oceanic plates in the Paleozoic move slower than continents based on current reconstructions of continental motion,which is difficult to reconcile with geodynamic studies.     

羌塘-三江古生代-中生代沉积盆地演化

羌塘-三江构造-地层大区的古生代-中生代沉积盆地和构造演化受特提斯洋的控制.通过综合分析前人对羌塘-三江地区大量岩石地层、生物地层、同位素年代学及构造学等研究资料,对羌塘-三江构造-地层大区各分区古生代-中生代的沉积盆地类型进行了划分,并分析了各个沉积盆地的形成和演化过程,探讨了该区的大地构造演化:早古生代该区主体属于大洋环境;晚古生代随着特提斯洋向南东、北东方向的俯冲,该区开始发育一系列活动陆缘沉积盆地,产生金沙江弧后洋、澜沧江弧后洋和甘孜-理塘弧后洋,形成多岛洋弧盆系;中生代,随着特提斯洋向北东的俯冲消减,弧后洋逐渐闭合,羌塘-三江地区发生大规模弧-弧、弧-陆碰撞增生,逐渐转化成陆.随着白垩纪特提斯洋的闭合,印度板块与中国西部碰撞、造山,羌塘-三江地区发育陆内盆地.