北祁连早古生代大地构造演化   总被引：68，自引：2，他引：68       下载免费PDF全文

左国朝  刘寄陈 《地质科学》1987,(1):14-24

早古生代北祁连是一个陆间微洋盆。震旦纪时,北祁连开始从华北板块中解体出来。主要裂谷作用发生于寒武世。北祁连地槽主要闭合期为晚奥陶世和早、中志留世。晚志留世和早泥盆世经历了复杂的消减作用。  相似文献   

Organic geochemical characteristics of sediments from the anoxic brine-filled Tyro basin (eastern Mediterranean)     

H.L. ten Haven  M. Baas  J.W. de Leeuw  J.M. Maassen  P.A. Schenck 《Organic Geochemistry》1987,11(6)

Soxhlet-extractable organic compounds of sediments from the anoxic brine-filled Tyro basin (eastern Mediterranean) were analyzed by gas chromatography and gas chromatography-mass spectrometry. Cholesterol and 22,29,30-trisnorhopan-21-one are the major compounds identified. The occurrence of this triterpenoid ketone, as well as 22,29,30-trisnorhop-6-en-21-one and diplopterol (both tentatively identified), is ascribed to an input of microbiota living at the brine-seawater interface.  相似文献   

Geothermal energy prospects in Brazil: A preliminary analysis     

V. M. Hamza  S. M. Eston  R. L. C. Araujo 《Pure and Applied Geophysics》1978,117(1-2):180-195

Results of geothermal gradient measurements in 44 localities in Brazil are presented. The Precambrian shield areas are found to be characterized by relatively low temperature gradients in the range 6 to 20°C/km while younger sedimentary basins are characterized by gradients in the range 15 to 35°C/km. An inverse correlation between geothermal gradient and tectonic age has been observed. This as well as the favourable hydrological conditions suggest that the best sites for extraction of geothermal energy in Brazil are the younger sedimentary basins. The Parana Basin is found to offer at present the best site for extraction of geothermal energy in Brazil. Preliminary examination of the temperature distributions in the major aquifer (Botucatu sandstone) suggest that this aquifer contains substantial quantities of warm waters in the temperature range 40 to 90°C. The water layer in this confined aquifer is in convective motion and can be considered as a low enthalphy geothermal system. Many of the routine uses to which geothermal waters are put, such as space heating and soil warming, are not applicable in Brazil mainly because of the favourable climatic conditions. Conversion of this geothermal energy into electrical energy is also unlikely to be economical. Hence we do not consider the Parana Basin geothermal system as an independent ec9nomically exploitable energy resource. However, a few other applications are pointed out where geothermal waters can be used as a supplementary or supporting energy source in increasing the efficiency of economically viable systems utilizing hot waters.  相似文献   

Low enthalpy geothermal energy resources in Denmark     

Niels Balling  Svend Saxov 《Pure and Applied Geophysics》1978,117(1-2):205-212

The deep oil exploration drillings in Denmark have shown that especially the Danish Embayment contains low enthalpy geothermal resources associated with warm aquifers. The most promising reservoirs have been found in highly permeable Upper Triassic sand and sandstone beds, which cover at least 5000 km² at depths of 2000–3000 m and at temperatures of 60–100°C. The porosity of the main reservoir is of 15–25%, and the permeability is presumed to be approximately 1 darcy (10^–12 m²) or higher. A layer thickness of 30–60 m has been observed on a number of localities. Also the Middle Jurassic and the Lower Triassic contain reservoirs of interest. A major geothermal exploration work is planned with seismic investigations, drillings to depths of 2000–4000 m and probably establishment of pilot district heating plants.  相似文献   

松辽盆地东缘域地壳结构及其地质意义:深反射地震          下载免费PDF全文

王建民  杨宝俊  李占林  于春玲  江才君  李鹏  曹来圣  陈智 《地球物理学报》1954,63(9):3478-3490

松辽盆地东缘域位于松嫩—张广才岭微板块东部.自晚古生代以来该域经历了西拉木伦河缝合带闭合产生的北向挤压作用、蒙古—鄂霍茨克洋自西向东剪刀叉式闭合对其东侧东南侧产生的挤压作用以及西太平洋板块西向变向俯冲产生的挤压作用等区域构造应力场影响,从而产生了复杂的地壳变动.该东缘域的地壳结构与松辽盆地地壳是否具有相近的结构特点,这是至今未被研究的内容.在Songliao Drep研究中已经用深反射地震手段得到松辽盆地地壳结构的一组新认识.这些认识在其东缘域是否还成立,也需要用同样精度的手段予以研究.另外,莫霍界面的宏观特征与微观（内部）特征,从松辽盆地到其东缘域有什么样的变化,其形成机理是什么,也需要进一步研究.为了回答这些科学问题,从哈尔滨西至尚志市附近实施了一条东西向约150 km长的深反射地震剖面.通过研究发现东缘域与松辽盆地基底地壳具有明显的差别,即由松辽盆地地壳的三分性变到东缘域盆地外地壳的二分性,在剖面近东端得到近26 km深的莫霍界面深度,并用均衡理论分析莫霍界面形态特征的形成机理;上部地壳存在双向大型推覆断裂,推测其被推覆体主体是古亚洲洋沉积地层即C-P系海相地层.这些认识为中国东北地区探查晚古生代海相地层、研究东北亚地壳结构特征提供了理论依据.  相似文献   

大洋钻探与西太平洋构造   总被引：3，自引：0，他引：3  

金性春 《地球科学进展》1995,10(3):234-239

菲律宾海的深海钻探证了弧间扩张和残留弧形模式。小笠原－马里亚纳弧前区的钻探表明，俯冲带初生时伴着海底扩张，形成了异常宽阔的火山活动带。有许多出上蛇绿岩形成于俯冲带初生时的海底扩张环境。日本海的钻探揭示了日本边缘盆地的打开和关闭，新近形成的日本海东缘板边界对华北地区的构造有重要制约作用，中国东海和南海占有独特的构造位置，布置大洋钻探意义重大。文章还强调了中国地质学家从全球地质学的观点研究问题（而不仅  相似文献   

Late Paleozoic volcanic rocks of the Intra-Sudetic Basin, Bohemian Massif: petrological and geochemical characteristics   总被引：1，自引：0，他引：1  

J Ulrych  F Fediuk  P Martinec 《Chemie der Erde / Geochemistry》2004,64(2):127-153

Late Paleozoic volcanic rocks in the Intra-Sudetic Basin of the Bohemian Massif in the Czech Republic can be subdivided into two series: (I) a minor bimodal trachyandesite-rhyolite series of Upper Carboniferous age with initial ⁸⁷Sr/⁸⁶Sr of ca. 0.710 and ε_Nd values of −6.1 also characteristic of volcanics of the near Krkonoše Piedmont Basin (0.707 and −6.0, Ulrych et al., 2003) and (II) a major differentiated basaltic trachyandesite-trachyandesite-trachyte-rhyolite series of Lower Permian age with lower initial ⁸⁷Sr/⁸⁶Sr of ca. 0.705-0.708 and ε_Nd values ranging from −2.7 to −3.4/−4.1/. The newly recognized volcanic rocks of trachytic composition indicate that the rocks were formed by magmatic differentiation of similar parental melts rather than constituting a bimodal mafic-felsic sequence from different sources. Both series are generally of subalkaline affinity and calc-alkaline character with some tholeiitic tint (FeO/MgO vs. SiO₂, presence of orthopyroxene). The magmatic activity occurred in cycles in a layered chamber, each starting primarily with felsic volcanics and ending with mafic ones. The mafic rocks represent mantle-melt(s) overprinted by crust during assimilation-fractional crystallization. The Sr-Nd isotopic data confirm a significant crustal component in the volcanic rocks that may have been inherited from the upper mantle source and/or from assimilation of older crust during magmatic underplating and shallow-level melt fractionation.  相似文献   

高煤级煤储层煤层气产能“瓶颈”问题研究   总被引：12，自引：0，他引：12  

傅雪海 秦勇姜波  韦重韬 《地质论评》2004,50(5):507-513

基于山西沁水盆地高煤级煤储层宏观裂隙、显微裂隙的连续观测,孔隙的系统测量,结合应力渗透率、气-水相对渗透率、吸附膨胀等实验成果,分析了高煤级煤储层三级渗流特征,探讨了有效应力和煤基质收缩对高煤级煤储层渗透率的耦合作用,系统揭示了在地面排水降压开发煤层气的过程中,高煤级煤储层初期产气量高,数月后急剧衰减之“瓶颈”现象,找出了造成高煤级煤储层产气缺陷的根本原因。鉴于高煤级煤储层物性的特殊性,指出了高煤级煤储层煤层气开发的技术和措施。  相似文献   

The hydrogeothermal basin of Sofia graben (Bulgaria)     

K.?D.?ShterevEmail author 《Environmental Geology》2004,46(5):651-660

Abstract In the Mesozoic basement and Neogene filling of Sofia tectonic graben a non-homogenous system of thermal water reservoirs connected to a united hydrogeothermal basin occurred. The basin contains and reproduces five types of low mineralized thermal waters and four types of mineralized thermal waters with exotic composition. The water temperatures are 30–80(90) ^°C. The total potential of the basin is assessed at 500 l/s thermal waters and 48 MWt thermal power. The utilization of thermal waters in the area of the Bulgarian capital has its roots and traditions in antiquity, and a promising future. The new town plan of Sofia provides construction of 35 centers for developing a versatile and prosperous hydrothermal business.  相似文献   

Trace elements in medium-temperature (40–80 °C) thermal waters from the Mura basin (North-Eastern Slovenia)     

Peter?KraljEmail author 《Environmental Geology》2004,46(5):622-629

Medium-temperature thermal waters in the Mura basin occur in hydrogeological systems different in age, burial depth, temperature, porosity and permeability, and the presence of free carbon dioxide which penetrates through the fractures from pre-Tertiary basement. The waters commonly belong to sodium-bicarbonate hydrogeochemical facies, but may have significantly different amounts of total dissolved solids, including trace elements. Thermal waters occurring in low-permeable, well-compacted and moderately fractured Tertiary sediments older than Upper Pliocene are the richest in trace elements, although their abundance may be very variable from one aquifer to another. The ratios of major alkaline and alkaline earth elements (Na, K, Ca) and trace elements (Li, Rb, Cs, Ba, Sr) commonly show relative enrichment in highly mineralised waters with respect to the waters with lower mineralisation. Rare earth elements (REEs) and Y show only minor fractionation in the highly mineralised waters, whereas in the waters with lower mineralisation strong fractionation of heavy rare earth elements (HREEs) over light rare earth elements (LREEs) occurs, along with a pronounced positive europium anomaly. Positive Th/U ratios are commonly observed, although both actinide elements occur in the range of some hundredths of ppb to some ppb. Trace elements were particularly useful in the study of well cycling in two hydraulically interconnected geothermal wells in the town of Murska Sobota, which produce a mixture of low- and high-mineralised waters.  相似文献